Recycling potential of neodymium: the case of computer hard disk drives.

PubMed

Sprecher, Benjamin; Kleijn, Rene; Kramer, Gert Jan

2014-08-19

Neodymium, one of the more critically scarce rare earth metals, is often used in sustainable technologies. In this study, we investigate the potential contribution of neodymium recycling to reducing scarcity in supply, with a case study on computer hard disk drives (HDDs). We first review the literature on neodymium production and recycling potential. From this review, we find that recycling of computer HDDs is currently the most feasible pathway toward large-scale recycling of neodymium, even though HDDs do not represent the largest application of neodymium. We then use a combination of dynamic modeling and empirical experiments to conclude that within the application of NdFeB magnets for HDDs, the potential for loop-closing is significant: up to 57% in 2017. However, compared to the total NdFeB production capacity, the recovery potential from HDDs is relatively small (in the 1-3% range). The distributed nature of neodymium poses a significant challenge for recycling of neodymium.

The thermal expansion of hard magnetic materials of the Nd-Fe-B system

NASA Astrophysics Data System (ADS)

Savchenko, Igor; Kozlovskii, Yurii; Samoshkin, Dmitriy; Yatsuk, Oleg

2017-10-01

The results of dilatometric measurement of the thermal expansion of hard magnetic materials brands N35M, N35H and N35SH containing as a main component the crystalline phase of Nd2Fe14B type are presented. The temperature range from 200 to 750 K has been investigated by the method of dilatometry with an error of 1.5-2×10-7 K-1. The approximation dependences of the linear thermal expansion coefficient have been obtained. The character of changes of the thermal coefficient of linear expansion in the region of the Curie point has been specified, its critical indices and critical amplitudes have been defined.

New magnetic rails with double-layer Halbach structure by employing NdFeB and ferrite magnets for HTS maglev

NASA Astrophysics Data System (ADS)

Sun, Ruixue; Zheng, Jun; Zheng, Botian; Qian, Nan; Li, Jipeng; Deng, Zigang

2018-01-01

In the high temperature superconducting (HTS) maglev system, the magnetic rail as an essential infrastructure is needed all along the route to carry passengers and goods to the destinations. Thus, large amount of rare earth magnetic materials are required in the magnetic rail construction. In order to decrease the dependence of magnetic rails on rare earth elements, the ferrite magnet is employed to replace part of the NdFeB magnets containing rare earth elements. Consequently, a new type rail with double-layer Halbach structure is presented, which is consisted of NdFeB and ferrite magnets. In this paper, we designed and fabricated the proposed rail, and further measured its magnetic flux density distribution and electromagnetic force interacting with HTS bulks. Experimental results indicate that, this new type rail, in double-layer Halbach structure, can achieve an equivalent distribution of magnetic flux density and levitation performance as the pure NdFeB Halbach rail, while a 10% reduction in NdFeB magnet consumption can be realized at the same time. In addition this work explores another magnetic material selection for HTS maglev applications. The dependence on rare earth element and the cost of magnetic rails can be further reduced, as the coercive force of ferrite magnets improved.

Dysprosium-free melt-spun permanent magnets.

PubMed

Brown, D N; Wu, Z; He, F; Miller, D J; Herchenroeder, J W

2014-02-12

Melt-spun NdFeB powders can be formed into a number of different types of permanent magnet for a variety of applications in electronics, automotive and clean technology industries. The melt-spinning process produces flake powder with a fine uniform array of nanoscale Nd2Fe14B grains. These powders can be net-shape formed into isotropic polymer-bonded magnets or hot formed into fully dense magnets. This paper discusses the influence of heavy rare earth elements and microstructure on the magnetic performance, thermal stability and material cost of NdFeB magnets. Evidence indicates that melt-spun nanocrystalline NdFeB magnets are less dependent on heavy rare earth elements for high-temperature performance than the alternative coarser-grained sintered NdFeB magnets. In particular, hot-pressed melt-spun magnets are an attractive low-cost solution for applications that require thermal stability up to 175-200 °C.

Material flow analysis of NdFeB magnets for Denmark: a comprehensive waste flow sampling and analysis approach.

PubMed

Habib, Komal; Schibye, Peter Klausen; Vestbø, Andreas Peter; Dall, Ole; Wenzel, Henrik

2014-10-21

Neodymium-iron-boron (NdFeB) magnets have become highly desirable for modern hi-tech applications. These magnets, in general, contain two key rare earth elements (REEs), i.e., neodymium (Nd) and dysprosium (Dy), which are responsible for the very high strength of these magnets, allowing for considerable size and weight reduction in modern applications. This study aims to explore the current and future potential of a secondary supply of neodymium and dysprosium from recycling of NdFeB magnets. For this purpose, material flow analysis (MFA) has been carried out to perform the detailed mapping of stocks and flows of NdFeB magnets in Denmark. A novel element of this study is the value added to the traditionally practiced MFAs at national and/or global levels by complementing them with a comprehensive sampling and elemental analysis of NdFeB magnets, taken out from a sample of 157 different products representing 18 various product types. The results show that the current amount of neodymium and dysprosium in NdFeB magnets present in the Danish waste stream is only 3 and 0.2 Mg, respectively. However, this number is estimated to increase to 175 Mg of neodymium and 11.4 Mg of dysprosium by 2035. Nevertheless, efficient recovery of these elements from a very diverse electronic waste stream remains a logistic and economic challenge.

The Impact Induced Demagnetization Mechanism in NdFeB Permanent Magnets

NASA Astrophysics Data System (ADS)

Li, Yan-Feng; Zhu, Ming-Gang; Li, Wei; Zhou, Dong; Lu, Feng; Chen, Lang; Wu, Jun-Ying; Qi, Yan; Du, An

2013-09-01

Compression of unmagnetized Nd2Fe14B permanent magnets is executed by using shock waves with different pressures in a one-stage light gas gun system. The microstructure, crystal structure, and magnetic properties of the magnets are examined with scanning electronic microscopy, x-ray diffraction, hysteresis loop instruments, and a vibrating sample magnetometer, respectively. The NdFeB magnets display a demagnetization phenomenon after shock wave compression. The coercivity dropped from about 21.4 kOe to 3.2 kOe. The critical pressure of irreversible demagnetization of NdFeB magnets should be less than 4.92 GPa. The coercivity of the NdFeB magnets compressed by shock waves could be recovered after annealing at 900°C and 520°C for 2 h, sequentially. The chaotic orientation of Nd2Fe14B grains in the compressed magnets is the source of demagnetization.

Life Cycle Assessment of Neodymium-Iron-Boron Magnet-to-Magnet Recycling for Electric Vehicle Motors.

PubMed

Jin, Hongyue; Afiuny, Peter; Dove, Stephen; Furlan, Gojmir; Zakotnik, Miha; Yih, Yuehwern; Sutherland, John W

2018-03-20

Neodymium-iron-boron (NdFeB) magnets offer the strongest magnetic field per unit volume, and thus, are widely used in clean energy applications such as electric vehicle motors. However, rare earth elements (REEs), which are the key materials for creating NdFeB magnets, have been subject to significant supply uncertainty in the past decade. NdFeB magnet-to-magnet recycling has recently emerged as a promising strategy to mitigate this supply risk. This paper assesses the environmental footprint of NdFeB magnet-to-magnet recycling by directly measuring the environmental inputs and outputs from relevant industries and compares the results with production from "virgin" materials, using life cycle assessments. It was found that magnet-to-magnet recycling lowers environmental impacts by 64-96%, depending on the specific impact categories under investigation. With magnet-to-magnet recycling, key processes that contribute 77-95% of the total impacts were identified to be (1) hydrogen mixing and milling (13-52%), (2) sintering and annealing (6-24%), and (3) electroplating (6-75%). The inputs from industrial sphere that play key roles in creating these impacts were electricity (24-93% of the total impact) and nickel (5-75%) for coating. Therefore, alternative energy sources such as wind and hydroelectric power are suggested to further reduce the overall environmental footprint of NdFeB magnet-to-magnet recycling.

Evaluation of the effects of aging in synthetic saliva solution of both commercial and silanized Nd-Fe-B magnets for dental application

NASA Astrophysics Data System (ADS)

Fabiano, F.; Puliafito, V.; Calabrese, L.; Borsellino, C.; Bonaccorsi, L. M.; Giordano, A.; Fabiano, V.; Cordasco, G.

2016-04-01

Neodymium-iron-boron magnets are able to ensure a magnetic flux with high maximum energy product also at miniaturized size. In the past, due to their marked corrosion in saliva they were unsuccessfully implemented in orthodontic systems. Thereby, we propose a multi-layered organic-inorganic coating able to supply anticorrosion resistance, wear resistance and durability to the whole assembly. We evaluated the influence on the magnetic force of commercial nickel plated and silanized Nd-Fe-B during aging time in synthetic Fusayama saliva. Two magnets based-micromagnetic simulations were performed in order to analyze the magnetic field generated which is linked to the magnetic force. Our key results underline that the proposed hybrid coating does not affect the magnetic force of Nd-Fe-B magnets, moreover, preventing corrosion degradation in aggressive solution. Thus the limiting aspects avoiding the use of Nd-Fe-B magnets for orthodontic and prosthodontic applications can be overcome by using silane agents as surface coating.

Assessment of corrosion resistance of Nd-Fe-B magnets by silanization for orthodontic applications

NASA Astrophysics Data System (ADS)

Fabiano, F.; Celegato, F.; Giordano, A.; Borsellino, C.; Bonaccorsi, L.; Calabrese, L.; Tiberto, P.; Cordasco, G.; Matarese, G.; Fabiano, V.; Azzerboni, B.

2014-02-01

Nd-Fe-B permanent magnets are characterised by excellent magnetic properties. However, being extremely vulnerable to the attack of both climate and corrosive environments, their applications are limited. This paper describes how, at different thicknesses of N-propyl-trimetoxy-silane, the coating affects the magnetic force of nickel plated magnets. We also investigate if the corrosion resistance of silanized Nd-Fe-B magnets increases in mildly corrosive environments by immersing them in a synthetic saliva solution. It was found that the silanization treatment does not affect the strength of the magnetic force and provide an enhancement of the corrosion resistance of the substrate.

High performance bonded neo magnets using high density compaction

NASA Astrophysics Data System (ADS)

Herchenroeder, J.; Miller, D.; Sheth, N. K.; Foo, M. C.; Nagarathnam, K.

2011-04-01

This paper presents a manufacturing method called Combustion Driven Compaction (CDC) for the manufacture of isotropic bonded NdFeB magnets (bonded Neo). Magnets produced by the CDC method have density up to 6.5 g/cm3 which is 7-10% higher compared to commercially available bonded Neo magnets of the same shape. The performance of an actual seat motor with a representative CDC ring magnet is presented and compared with the seat motor performance with both commercial isotropic bonded Neo and anisotropic NdFeB rings of the same geometry. The comparisons are made at both room and elevated temperatures. The airgap flux for the magnet produced by the proposed method is 6% more compared to the commercial isotropic bonded Neo magnet. After exposure to high temperature due to the superior thermal aging stability of isotropic NdFeB powders the motor performance with this material is comparable to the motor performance with an anisotropic NdFeB magnet.

CRADA/NFE-15-05761 Report: Additive Manufacturing of Isotropic NdFeB Bonded Permanent Magnets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paranthaman, M. Parans

2016-07-18

The technical objective of this technical collaboration phase I proposal is to fabricate net shape isotropic NdFeB bonded magnets utilizing additive manufacturing technologies at the ORNL MDF. The goal is to form complex shapes of thermoplastic and/or thermoset bonded magnets without expensive tooling and with minimal wasted material. Two additive manufacturing methods; the binder jet process; and big area additive manufacturing (BAAM) were used. Binder jetting produced magnets with the measured density of the magnet of 3.47 g/cm 3, close to 46% relative to the NdFeB single crystal density of 7.6 g/cm 3 were demonstrated. Magnetic measurements indicate that theremore » is no degradation in the magnetic properties. In addition, BAAM was used to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm 3, and the room temperature magnetic properties are: Intrinsic coercivity Hci = 8.65 kOe, Remanence Br = 5.07 kG, and energy product (BH) max = 5.47 MGOe (43.50 kJ/m 3). This study provides a new pathway for preparing near-net shape bonded magnets for various magnetic applications.« less

Double coating protection of Nd-Fe-B magnets: Intergranular phosphating treatment and copper plating

NASA Astrophysics Data System (ADS)

Zheng, Jingwu; Chen, Haibo; Qiao, Liang; Lin, Min; Jiang, Liqiang; Che, Shenglei; Hu, Yangwu

2014-12-01

In this work, a double coating protection technique of phosphating treatment and copper plating was made to improve the corrosion resistance of sintered Nd-Fe-B magnets. In other words, the intergranular region of sintered Nd-Fe-B is allowed to generate passive phosphate conversion coating through phosphating treatment, followed by the copper coating on the surface of sintered Nd-Fe-B. The morphology and corrosion resistance of the phosphated sintered Nd-Fe-B were observed using SEM and electrochemical method respectively. The phosphate conversion coating was formed more preferably on the intergranular region of sintered Nd-Fe-B than on the main crystal region; just after a short time of phosphating treatment, the intergranular region of sintered Nd-Fe-B has been covered by the phosphate conversion coating and the corrosion resistance is significantly improved. With the synergistic protection of the intergranular phosphorization and the followed copper electrodeposition, the corrosion resistance of the sintered Nd-Fe-B is significantly better than that with a single phosphate film or single plating protection.

20 T portable bipolar magnetic pulser.

PubMed

Wolf Cruz, R R; Dias, A L B; Bonfim, M J C

2010-06-01

High magnetic fields are required for the study of hard magnetic materials and, in many cases, the reversal of these fields is essential. This paper describes a portable pulse generator capable of producing bipolar magnetic fields up to 20 T into a copper coil. The peak current around 7 kA is achieved by discharging two capacitor banks through a combination of thyristors and fast diodes. Each pulse polarity has a semisinusoidal shape with 18 mus base width. Pulse triggering is computer controlled and magnetic measurements are done by an induction coil or Kerr effect acquired by a sampling oscilloscope. The whole apparatus weighs less than 2 kg. Hysteresis loops of NdFeB magnets were done to demonstrate the viability of the system.

Effect of washing process on the magnetic properties of Nd-Fe-B nanoparticles prepared by reduction-diffusion method

NASA Astrophysics Data System (ADS)

Wang, Y.; Ahn, J.; Kim, D.; Ren, W. J.; Liu, W.; Zhang, Z. D.; Choi, C. J.

2017-10-01

Nd-Fe-B nanoparticles with a particle size below 50 nm and excellent magnetic properties were obtained via a novel route which makes use of both spray drying and reduction-diffusion processes. Uniform Nd-Fe-B particles were formed by the optimization of Ca amount as a reducing agent and additional washing by milling in ethanol media. Especially, we implemented a two-step washing process which contributed to the excellent magnetic properties with high remanence and coercivity. After the removal of CaO by novel washing process, the maximum energy product (BH)max of the particles showed 22.1 MGOe. This value is superior to those reported in reduction-diffusion process. We used Henkel plot to assume the mechanism of magnetic interactions of the Nd-Fe-B nanoparticles.

Study on corrosion behaviors of sintered Nd-Fe-B magnets in different environmental conditions

NASA Astrophysics Data System (ADS)

Li, J. J.; Li, A. H.; Zhu, M. G.; Pan, W.; Li, W.

2011-04-01

Nd-Fe-B magnets have outstanding magnetic properties, but their corrosion resistance is poor because the rare-earth-rich phases in them are easily oxidized. In this article, we report an investigation of the corrosion behaviors of sintered Nd-Fe-B magnets with varied compositions in different corrosion conditions. The weight losses of the magnets after corrosion testing were measured after brushing off the corrosion products. The magnetic flux losses of the magnets were measured using a fluxmeter. A scanning electron microscope equipped with an energy dispersive x-ray analysis system was employed to observe the corrosion morphology. It was found that the humid-heat resistance of the magnets was obviously improved by partially substituting Dy for Nd and adding minor Co. The corrosion products and morphologies of Nd-Fe-B magnets for the autoclave test were different from those for the constant humid-heat test. The corrosion rates of the magnets for the former were much slower than for the latter; this is probably because the high-pressure steam led to an oxygen-deficient atmosphere, and the liquid film on the surface of the magnet specimens hindered the diffusion of oxygen into the bulk for the autoclave test.

Microstructure evaluation for Dy-free Nd-Fe-B sintered magnets with high coercivity

NASA Astrophysics Data System (ADS)

Goto, R.; Matsuura, M.; Sugimoto, S.; Tezuka, N.; Une, Y.; Sagawa, M.

2012-04-01

Nd-Fe-B sintered magnets are used for motors of hybrid or electric vehicles due to their high energy products. Dy is added to Nd-Fe-B sintered magnets to work in a high temperature environment. Although the addition of Dy decreases the magnetization of Nd-Fe-B magnets, it increases coercivity; a decrease in the amount of Dy is strongly required. Recently, Nd-Fe-B sintered magnets with a grain size of 1 μm achieved high coercivity of ˜20 kOe without the addition of Dy or other heavy rare earth elements. In this paper, the microstructure of their magnets was observed and compared to magnets with a grain size of ˜3 μm. The coercivity of magnets consisting of larger particles was 17 kOe. Microstructures were observed by the scanning electron microscope and the shapes of grains and the distribution of the Nd-rich phase were evaluated. The observation was promoted in two directions. One direction is the plane perpendicular to the magnetically aligned direction (c plane side) and the other is the side parallel to the magnetically aligned direction (c axis side). For magnets consisting of smaller particles, the shapes of grains are isotropic for the c plane side and elongated for the c axis side. The angle of minor axis prefers to be parallel to magnetically aligned direction. The distribution of the Nd-rich phase for magnets was also evaluated for both magnets. The distribution of the Nd-rich phase at triple junctions for the magnets with smaller particles becomes homogeneous compared to that for magnets with larger particles. It is considered that Dy-free magnets with high coercivity were realized by the achievement of homogeneous distribution of Nd-rich phase besides decreasing grain size.

Tracking the Flow of Resources in Electronic Waste - The Case of End-of-Life Computer Hard Disk Drives.

PubMed

Habib, Komal; Parajuly, Keshav; Wenzel, Henrik

2015-10-20

Recovery of resources, in particular, metals, from waste flows is widely seen as a prioritized option to reduce their potential supply constraints in the future. The current waste electrical and electronic equipment (WEEE) treatment system is more focused on bulk metals, where the recycling rate of specialty metals, such as rare earths, is negligible compared to their increasing use in modern products, such as electronics. This study investigates the challenges in recovering these resources in the existing WEEE treatment system. It is illustrated by following the material flows of resources in a conventional WEEE treatment plant in Denmark. Computer hard disk drives (HDDs) containing neodymium-iron-boron (NdFeB) magnets were selected as the case product for this experiment. The resulting output fractions were tracked until their final treatment in order to estimate the recovery potential of rare earth elements (REEs) and other resources contained in HDDs. The results further show that out of the 244 kg of HDDs treated, 212 kg comprising mainly of aluminum and steel can be finally recovered from the metallurgic process. The results further demonstrate the complete loss of REEs in the existing shredding-based WEEE treatment processes. Dismantling and separate processing of NdFeB magnets from their end-use products can be a more preferred option over shredding. However, it remains a technological and logistic challenge for the existing system.

Energy barrier analysis of Nd-Fe-B thin films

NASA Astrophysics Data System (ADS)

Goto, R.; Okamoto, S.; Kikuchi, N.; Kitakami, O.

2015-05-01

The magnetization reversal mechanism of a permanent magnet has long been a controversial issue, which is closely related to the so-called coercivity problem. It is well known that the energy barrier for magnetization reversal contains essential information on reversal process. In this study, we propose a method to analyze the energy barrier function for the magnetization reversal. Preferentially (001) oriented Nd-Fe-B films with and without a Nd overlayer are used as model magnets. By combining the magnetic viscosity and time dependent coercivity measurements, the barrier function has been successfully evaluated. As a result, although the Nd-Fe-B films with and without Nd overlayer exhibit different magnetic behaviors, the power indices for their energy barrier are almost the same, suggesting that the magnetization reversal proceeds in a similar mode.

COST-EFFECTIVE RARE EARTH ELEMENT RECYCLING PROCESS FROM INDUSTRIAL SCRAP AND DISCARDED ELECTRONIC PRODUCTS TO VALUABLE MAGNETIC ALLOYS AND PERMANENT MAGNETS - PHASE II

EPA Science Inventory

Rare earth element (REE) based Nd-Fe-B and Sm-Co permanent magnets have been widely used because of their excellent magnetic properties. The applications of Nd-Fe-B and Sm-Co rare earth permanent magnets include hybrid electric vehicles (HEVs), power generators for wind tur...

Strategic coating of NdFeB magnets with Dy to improve the coercivity of permanent magnets

DOE PAGES

Ucar, Huseyin; Parker, David S.; Nlebedim, I. C.; ...

2015-12-25

Here, we present a method, supported by theoretical analysis, for optimizing the usage of the critical rare earth element dysprosium in Nd 2Fe 14B (NdFeB)-based permanent magnets. In this method, we use Dy selectively in locations such as magnet edges and faces, where demagnetization factors are most significant, rather than uniformly throughout the bulk sample. A 200 nm thick Dy film was sputtered onto commercial N-38, NdFeB magnets with a thickness of 3 mm and post-annealed at temperatures from 600 - 700 C. Magnets displayed enhanced coercivities after post-annealing. Furthermore, our experimental results indicate as large as a 5 percentmore » increase in the energy product of NdFeB magnets, achieved for a total Dy weight percentage of 0.06 percent, much less than that used in commercial grade Dy-NdFeB magnets. Finally, by assuming all Dy diffused into NdFeB magnets, the improvement in energy product corresponds to a saving of over 1% Dy (critical element). Magnets manufactured using this technique will therefore be higher performing and significantly less expensive than those made presently.« less

Electromagnetic machines with Nd-Fe-B magnets

NASA Astrophysics Data System (ADS)

Hanitsch, Rolf

1989-08-01

Permanent magnet motors are now becoming more accepted for general use in industrial fixed and variable speed drives. With the application of high-energy permanent magnets, such as Nd-Fe-B, the new motors offer higher efficiency and reduced size and weight compared with wound field energy converters of the same rating.

Characterization of the magnetic properties of NdFeB thick films exposed to elevated temperatures

NASA Astrophysics Data System (ADS)

Fujiwara, Ryogen; Devillers, Thibaut; Givord, Dominique; Dempsey, Nora M.

2018-05-01

Hard magnetic films used in magnetic micro-systems may be exposed to elevated temperatures during film and system fabrication and also during use of the micro-system. In this work, we studied the influence of temperature on the magnetic properties of 10 μm thick out-of-plane textured NdFeB films fabricated by high rate triode sputtering. Out-of-plane hysteresis loops were measured in the range 300K - 650K to establish the temperature dependence of coercivity, magnetization at 7 T and remanent magnetization. Thermal demagnetization was measured and magnetization losses were recorded from 350K in films heated under zero or low (-0.1 T) external field and from 325 K for films heated under an external field of -0.5 T. The effect of thermal cycling under zero field on the remanent magnetization was also studied and it was found that cycling between room temperature and 323 K did not lead to any significant loss in remanence at room temperature, while a 4% drop is recorded when the sample is cycled between RT and 343K. Measurement of hysteresis loops at room temperature following exposure to elevated temperatures reveals that while remanent magnetisation is practically recovered in all cases, irreversible losses in coercivity occur (6.7 % following heating to 650K, and 1.3 % following heating to 343K). The relevance of these results is discussed in terms of system fabrication and use.

Influence of Nb addition on vacancy defects and magnetic properties of the nanocrystalline Nd-Fe-B permanent magnets

NASA Astrophysics Data System (ADS)

Szwaja, Małgorzata; Gębara, Piotr; Filipecki, Jacek; Pawlik, Katarzyna; Przybył, Anna; Pawlik, Piotr; Wysłocki, Jerzy J.; Filipecka, Katarzyna

2015-05-01

In present work, influence of Nb addition on vacancy defects and magnetic properties of nanocrystalline Nd-Fe-B permanent magnets, was investigated. Samples with composition (Nd,Fe,B)100-xNbx (where x=6,7,8) were studied in as-cast state and after annealing. Samples were prepared by arc-melting with high purity of constituent elements under Ar atmosphere. Ribbons were obtained by melt-spinning technique under low pressure of Ar. Ribbon samples in as-cast state had amorphous structure and soft magnetic properties. Positron annihilation lifetime spectroscopy PALS has been applied to detection of positron - trapping voids (vacancy defects). With increase of Nb in alloy increasing of vacancy defects concentration was observed. Heat treatment of the samples was carried out at various temperatures (from 923 K to 1023 K) for 5 min, in order to obtain nanocrystalline structure. The aim of present work was to determine the influence of Nb addition and annealing conditions on the vacancy defects and magnetic properties of the Nd-Fe-B- type alloys in as-cast state and after heat treatment.

Fabrication of highly dense isotropic Nd-Fe-B nylon bonded magnets via extrusion-based additive manufacturing [Fabrication of highly dense isotropic Nd-Fe-B bonded magnets via extrusion-based additive manufacturing

DOE PAGES

Li, Ling; Jones, Kodey E.; Sales, Brian C.; ...

2018-04-03

Magnetically isotropic bonded magnets with a high loading fraction of 70 vol.% Nd-Fe-B are fabricated via an extrusion-based additive manufacturing, or 3D printing system that enables rapid production of large parts. The density of the printed magnet is ~5.2 g/cm 3. The room temperature magnetic properties are: intrinsic coercivity Hci = 8.9 kOe (708.2 kA/m), remanence Br = 5.8 kG (0.58 T), and energy product (BH)max = 7.3 MGOe (58.1 kJ/m 3). The as-printed magnets are then coated with two types of polymers, both of which improve the thermal stability as revealed by flux aging loss measurements. Tensile tests performedmore » at 25 °C and 100 °C show that the ultimate tensile stress (UTS) increases with increasing loading fraction of the magnet powder, and decreases with increasing temperature. AC magnetic susceptibility and resistivity measurements show that the 3D printed Nd-Fe-B bonded magnets exhibit extremely low eddy current loss and high resistivity. Lastly, we demonstrate the performance of the 3D printed magnets in a DC motor configuration via back electromotive force measurements.« less

Fabrication of highly dense isotropic Nd-Fe-B nylon bonded magnets via extrusion-based additive manufacturing [Fabrication of highly dense isotropic Nd-Fe-B bonded magnets via extrusion-based additive manufacturing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Ling; Jones, Kodey E.; Sales, Brian C.

Magnetically isotropic bonded magnets with a high loading fraction of 70 vol.% Nd-Fe-B are fabricated via an extrusion-based additive manufacturing, or 3D printing system that enables rapid production of large parts. The density of the printed magnet is ~5.2 g/cm 3. The room temperature magnetic properties are: intrinsic coercivity Hci = 8.9 kOe (708.2 kA/m), remanence Br = 5.8 kG (0.58 T), and energy product (BH)max = 7.3 MGOe (58.1 kJ/m 3). The as-printed magnets are then coated with two types of polymers, both of which improve the thermal stability as revealed by flux aging loss measurements. Tensile tests performedmore » at 25 °C and 100 °C show that the ultimate tensile stress (UTS) increases with increasing loading fraction of the magnet powder, and decreases with increasing temperature. AC magnetic susceptibility and resistivity measurements show that the 3D printed Nd-Fe-B bonded magnets exhibit extremely low eddy current loss and high resistivity. Lastly, we demonstrate the performance of the 3D printed magnets in a DC motor configuration via back electromotive force measurements.« less

Modeling of magnetic hystereses in soft MREs filled with NdFeB particles

NASA Astrophysics Data System (ADS)

Kalina, K. A.; Brummund, J.; Metsch, P.; Kästner, M.; Borin, D. Yu; Linke, J. M.; Odenbach, S.

2017-10-01

Herein, we investigate the structure-property relationships of soft magnetorheological elastomers (MREs) filled with remanently magnetizable particles. The study is motivated from experimental results which indicate a large difference between the magnetization loops of soft MREs filled with NdFeB particles and the loops of such particles embedded in a comparatively stiff matrix, e.g. an epoxy resin. We present a microscale model for MREs based on a general continuum formulation of the magnetomechanical boundary value problem which is valid for finite strains. In particular, we develop an energetically consistent constitutive model for the hysteretic magnetization behavior of the magnetically hard particles. The microstructure is discretized and the problem is solved numerically in terms of a coupled nonlinear finite element approach. Since the local magnetic and mechanical fields are resolved explicitly inside the heterogeneous microstructure of the MRE, our model also accounts for interactions of particles close to each other. In order to connect the microscopic fields to effective macroscopic quantities of the MRE, a suitable computational homogenization scheme is used. Based on this modeling approach, it is demonstrated that the observable macroscopic behavior of the considered MREs results from the rotation of the embedded particles. Furthermore, the performed numerical simulations indicate that the reversion of the sample’s magnetization occurs due to a combination of particle rotations and internal domain conversion processes. All of our simulation results obtained for such materials are in a good qualitative agreement with the experiments.

Effect of Fe-Mn addition on microstructure and magnetic properties of NdFeB magnetic powders

NASA Astrophysics Data System (ADS)

Kurniawan, C.; Purba, A. S.; Setiadi, E. A.; Simbolon, S.; Warman, A.; Sebayang, P.

2018-03-01

In this paper, the effect of Fe-Mn alloy addition on microstructures and magnetic properties of NdFeB magnetic powders was investigated. Varied Fe-Mn compositions of 1, 5, and 10 wt% were mixed with commercial NdFeB type MQA powders for 15 minutes using shaker mill. The characterizations were performed by powder density, PSA, XRD, SEM, and VSM. The Fe-Mn addition increased the powder density of NdFeB/Fe-Mn powders. On the other side, particle size distribution slightly decreased as the Fe-Mn composition increases. Magnetic properties of NdFeB/Fe-Mn powders changed with the increasing of Fe-Mn content. SEM analysis showed the particle size of NdFeB/Fe-Mn powder was smaller as the Fe-Mn composition increases. It showed that NdFeB/Fe-Mn particles have different size and shape for NdFeB and Fe-Mn particles separately. The optimum magnetic properties of NdFeB/Fe-Mn powder was achieved on the 5 wt% Fe-Mn composition with remanence M r = 49.45 emu/g, coercivity H c = 2.201 kOe, and energy product, BH max = 2.15 MGOe.

Dynamic fracture of sintered Nd-Fe-B magnet under uniaxial compression

NASA Astrophysics Data System (ADS)

Wang, Huanran; Wan, Yin; Chen, Danian; Lei, Guohua; Ren, Chunying

2018-06-01

The dynamic fracture of the Nd-Fe-B magnets under uniaxial compression is investigated using a split Hopkinson pressure bar (SHPB). The surface deformation and fracture processes of the Nd-Fe-B specimens are recorded adopting a high-speed photography (HSP) with digital image correlation (DIC). The load and work applied to the specimens in the SHPB tests are determined with the strain signals of the transmitted and reflected waves. The surface strain distributions of the Nd-Fe-B specimen during the SHPB testing are revealed with DIC. It is shown by the HSP with DIC that when the load is near the maximum, the cracks at some positions on the surface of the expanding Nd-Fe-B specimen are formed and ran along certain directions. The work applied to the specimen per unit volume which corresponds to the maximal load is used to characterize the impact stability of the Nd-Fe-B specimen. The localized fracture strains at some positions on the surface of the expanding specimens at some characteristic times are determined with DIC, which are the projections of the strains onto the DIC plane.

Liquid coated melt-spun Nd-Fe-B powders for bonded magnets

NASA Astrophysics Data System (ADS)

Li, D.; Gaiffi, S.; Kirk, D.; Young, K.; Herchenroeder, J.; Berwald, T.

1999-04-01

The liquid coating (LC) has been employed to apply epoxy and lubricant over the surface of rapidly solidified Nd-Fe-B powder particles. The LC led to an improvement of physical and magnetic properties for the powders and magnets compared to the dry blending and the encapsulation methods. The LC powders have excellent flowability and can be used for bonded magnets requiring very close tolerances; further bonded magnets made using this powder posses higher strength.

Re-exchange of Fe and Cu at the interface in sintered Nd-Fe-B magnets: A method to eliminate Fe precipitation at grain boundaries

NASA Astrophysics Data System (ADS)

Yang, YuQi; Si, HengGang; Yang, Hao; Zhang, Lan; Huang, DongFang; Chen, BaiYi; Xu, Fang; Hu, YongMei; Han, BaoJun

2018-01-01

According to the decoupling hypothesis for magnetic grains, the coercivity in sintered Nd-Fe-B magnets is increased after Cu doping, which is due to the formation of non-magnetic grain boundaries. However, this method partially fails, and ferromagnetic Fe-segregation occurs at the grain boundary. We discovered both experimentally and through calculation that the Fe content at the grain boundaries can be tuned across a wide range by introducing another element of Ag. Segregated Fe at high temperature at the grain boundary re-dissolves into Nd2Fe14B grains during annealing at low temperature. Both configurable and magnetic entropies contribute a large driving force for the formation of nonmagnetic grain boundaries. Almost zero Fe content could be achieved at the grain boundaries of sintered Nd-Fe-B magnet.

Structure and performance of anisotropic nanocrystalline Nd-Fe-B magnets fabricated by high-velocity compaction followed by deformation

NASA Astrophysics Data System (ADS)

Zhao, L. Z.; Deng, X. X.; Yu, H. Y.; Guan, H. J.; Li, X. Q.; Xiao, Z. Y.; Liu, Z. W.; Greneche, J. M.

2017-12-01

High-velocity compaction (HVC) has been proposed as an effective approach for the fabrication of nanocrystalline Nd-Fe-B magnets. In this work, the effect of powder size on the density of HVCed magnets has been studied and the anisotropic nanocrystalline Nd-Fe-B magnets were prepared by HVC followed by hot deformation (HD). It is found that a proper particle size range is beneficial to high density. The investigations on the microstructure, magnetic domain structure, and hyperfine structure, indicate that the deformed grain structure and the magnetic domain structure with uniform paramagnetic grain boundary phase give good magnetic properties of HVC + HDed magnets. These magnets also have good mechanical and anti-corrosion properties. The results indicate that HVC is not only a near-net-shape, room temperature and binder-free process but is also able to maintain uniform nanostructure and to achieve good magnetic properties in both isotropic and anisotropic magnets. As a result, HVC can be employed as an ideal alternative process for bonding or hot pressing for the conventional MQI, MQII and MQIII magnets.

Roles of coercivity and remanent flux density of permanent magnet in interior permanent magnet synchronous motor (IPMSM) performance for electric vehicle applications

NASA Astrophysics Data System (ADS)

Won, Hoyun; Hong, Yang-Ki; Lee, Woncheol; Choi, Minyeong

2018-05-01

We used four rotor topologies of an interior permanent magnet synchronous motor (IPMSM) to investigate the effects of remanent flux density (Br) and coercivity (Hc) of permanent magnet on motor performance. Commercial strontium hexaferrite (SrFe12O19: energy product, (BH)max, of 4.62 MGOe) and Nd-Fe-B ((BH)max of 38.2 MGOe) magnets were used for the rotor designs. The same machine specifications and magnet volume keep constant, while the Hc and Br vary to calculate torque and energy efficiency with the finite-element analysis. A combination of high Hc and low Br more effectively increased maximum torque of IPMSM when the hexaferrite magnet was used. For Nd-Fe-B magnet, the same combination did not affect maximum torque, but increased energy efficiency at high speed. Therefore, the Hc value of a permanent magnet is more effective than the Br in producing high maximum torque for SrM-magnet based IPMSM and high energy efficiency at high speed for Nd-Fe-B magnet based IPMSM.

Magnetic properties of (misch metal, Nd)-Fe-B melt-spun magnets

NASA Astrophysics Data System (ADS)

Li, R.; Shang, R. X.; Xiong, J. F.; Liu, D.; Kuang, H.; Zuo, W. L.; Zhao, T. Y.; Sun, J. R.; Shen, B. G.

2017-05-01

The effect of replacing Nd with misch metal (MM) on magnetic properties and thermal stability has been investigated on melt-spun (Nd1-xMMx)13.5Fe79.5B7 ribbons by varying x from 0 to 1. All of the alloys studied crystallize in the tetragonal 2:14:1 structure with single hard magnetic phase. Curie temperature (Tc), coercivity (Hcj), remanence magnetization (Br) and maximum energy product ((BH)max) all decrease with MM content. The melt-spun MM13.5Fe79.5B ribbons with high ratio of La and Ce exhibit high magnetic properties of Hcj = 8.2 kOe and (BH)max= 10.3 MGOe at room temperature. MM substitution also significantly strengthens the temperature stability of coercivity. The coercivities of the samples with x = 0.2 and even 0.4 exhibit large values close to that of Nd13.5Fe79.5B7 ribbons above 400 K.

Micro-patterning of resin-bonded NdFeB magnet for a fully integrated electromagnetic actuator

NASA Astrophysics Data System (ADS)

Tao, Kai; Wu, Jin; Kottapalli, Ajay Giri Prakash; Chen, Di; Yang, Zhuoqing; Ding, Guifu; Lye, Sun Woh; Miao, Jianmin

2017-12-01

This paper reports a fully-integrated, batch-fabricated electromagnetic actuator which features micro-patterned NdFeB magnets. The entire actuator is fabricated through MEMS-compatible laminated surface micromachining technology, eliminating the requirement for further component assembly processes. The fabrication strategy allowed the entire volume of the actuator to be reduced to a small size of 2.5 × 2.5 × 2 mm3, which is one of the smallest NdFeB-based electromagnetic actuators demonstrated to date. The magnetic properties of NdFeB thin films are further investigated and optimized using different types of lithographically-defined micromolds. By altering the direction of the input current, actuating displacements of approximately ±10 μm are achieved during both the attraction and the repulsion operations. This work demonstrates the viability and compatibility of using polymer-bonded magnets for magnetic MEMS applications.

Coercivity enhancement mechanism in Dy-substituted Nd-Fe-B nanoparticles synthesized by sol-gel base method followed by a reduction-diffusion process

NASA Astrophysics Data System (ADS)

Rahimi, Hamed; Ghasemi, Ali; Mozaffarinia, Reza; Tavoosi, Majid

2017-05-01

In current work, Nd15-xDyxFe77.5B7.5 (at%) nanoparticles with different Dy-content (x=0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0) were synthesized by sol-gel method followed by a reduction-diffusion process. The effects of Dy on the magnetic properties and the relations between the microstructure and the coercivity of Dy-substituted Nd-Fe-B nanoparticles have been studied. The coercivity of Nd-Fe-B nanoparticles with the addition of Dy first increase, reaches a maximum, and then starts to decrease. The coercivity of Dy-substituted Nd-Fe-B nanoparticle synthesized by sol-gel method increased from 938.9 to 1663.9 kA/m while the remanence decreased slightly from 1.16 to 1.06 T. The results show that with an increase in Dy content the variation of maximum energy product ((BH)max), lowest-order uniaxial magnetocrystalline anisotropy constant (Ku1), and Curie temperature (Tc) had a trend as same as the coercivity. The Henkel plot showed that the existence of exchange coupling interaction between grains, and the exchange coupling interactions increased with increasing x from 0.0 to 2.0 and then decrease with further increasing x≥2.5. The optimum magnetic properties of Nd-Fe-B nanoparticles with (BH)max =40.38 MGOe, Hc=1663.9 kA/m, Br=1.08 T were obtained by substituted 2.0 at% Dy. The effects of increasing temperature on magnetic properties of Dy-substituted Nd-Fe-B nanoparticle magnets with 2.0 at% Dy was investigated. The reduced spin-reorientation temperature was obtained for Dy-substituted Nd-Fe-B nanoparticles with 2.0 at% Dy. Below 100 K a spin-reorientation transition was takes place. The temperature coefficient of coercivity (β) was -0.36, -0.46, -0.41, -0.34, -0.29, -0.24, -0.25%/°C at different temperature 50, 100, 150, 200, 250, 300, 350 °C, respectively. Mössbauer spectroscopy was applied to study the composition and properties of Dy-substituted Nd-Fe-B magnet. Microstructure analysis showed a homogeneous distribution of Dy in produced samples. The possible reason for observed magnetic behavior is improving the intrinsic material parameter and optimizing the microstructure by a uniform enhancement of magnetocrystalline anisotropy by formation the nanocrystalline compound (Nd,Dy)2Fe14B.

Micromagnetics of rare-earth efficient permanent magnets

NASA Astrophysics Data System (ADS)

Fischbacher, Johann; Kovacs, Alexander; Gusenbauer, Markus; Oezelt, Harald; Exl, Lukas; Bance, Simon; Schrefl, Thomas

2018-05-01

The development of permanent magnets containing less or no rare-earth elements is linked to profound knowledge of the coercivity mechanism. Prerequisites for a promising permanent magnet material are a high spontaneous magnetization and a sufficiently high magnetic anisotropy. In addition to the intrinsic magnetic properties the microstructure of the magnet plays a significant role in establishing coercivity. The influence of the microstructure on coercivity, remanence, and energy density product can be understood by using micromagnetic simulations. With advances in computer hardware and numerical methods, hysteresis curves of magnets can be computed quickly so that the simulations can readily provide guidance for the development of permanent magnets. The potential of rare-earth reduced and rare-earth free permanent magnets is investigated using micromagnetic simulations. The results show excellent hard magnetic properties can be achieved in grain boundary engineered NdFeB, rare-earth magnets with a ThMn12 structure, Co-based nano-wires, and L10-FeNi provided that the magnet’s microstructure is optimized.

Binder Jetting: A Novel NdFeB Bonded Magnet Fabrication Process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paranthaman, M. Parans; Shafer, Christopher S.; Elliott, Amy M.

2016-04-05

Our goal of this research is to fabricate near-net-shape isotropic (Nd) 2Fe 14B-based (NdFeB) bonded magnets using a three dimensional printing process to compete with conventional injection molding techniques used for bonded magnets. Additive manufacturing minimizes the waste of critical materials and allows for the creation of complex shapes and sizes. The binder jetting process works similarly to an inkjet printer. A print-head passes over a bed of NdFeB powder and deposits a polymer binding agent to bind the layer of particles together. The bound powder is then coated with another layer of powder, building the desired shape in successivemore » layers of bonded powder. Upon completion, the green part and surrounding powders are placed in an oven at temperatures between 100°C and 150°C for 4–6 h to cure the binder. After curing, the excess powder can be brushed away to reveal the completed “green” part. Green magnet parts were then infiltrated with a clear urethane resin to achieve the measured density of the magnet of 3.47 g/cm 3 close to 46% relative to the NdFeB single crystal density of 7.6 g/cm 3. Magnetic measurements indicate that there is no degradation in the magnetic properties. In conclusion, this study provides a new pathway for preparing near-net-shape bonded magnets for various magnetic applications.« less

Coercivity enhancement in hot deformed Nd2Fe14B-type magnets by doping low-melting RCu alloys (R = Nd, Dy, Nd + Dy)

NASA Astrophysics Data System (ADS)

Lee, Y. I.; Huang, G. Y.; Shih, C. W.; Chang, W. C.; Chang, H. W.; You, J. S.

2017-10-01

Magnetic properties of the anisotropic NdFeB magnets prepared by hot pressing followed by die-upsetting NdFeB MQU-F powders doped with low-melting RCu alloy powders were explored, where RCu stands for Nd70Cu30, Dy70Cu30 and (Nd0.5Dy0.5)70Cu30, respectively. In addition, the post-annealing at 600 °C was employed to modify the microstructures and the magnetic properties of the hot deformed magnets. It is found that doping RCu alloy powders is effective in enhancing the coercivity of the hot deformed NdFeB magnets from 15.1 kOe to 16.3-19.5 kOe. For Nd70Cu30-doped magnets, the increment of coercivity is only 1.2 kOe. Meanwhile, Dy70Cu30-doped and (Nd0.5Dy0.5)70Cu30-doped magnets show an almost identical enhancement of coercivity of about 4.4 kOe. Importantly, the latter magnet shows a beneficial effect of reducing the usage of Dy from 1.6 wt% to 0.8 wt%. TEM analysis shows that nonmagnetic Nd, Dy and Cu appear at grain boundary and isolate the magnetic grains, leading to an enhancement of coercivity. Doping lower melting point Dy-lean (Nd0.5Dy0.5)70Cu30 powders into commercial MQU-F powders for making high coercivity hot deformed NdFeB magnets might be a potential and economic way for mass production.

Perspective for using Nd-Fe-B magnets as a tool for the improvement of the production and transportation of Vietnamese crude oil with high paraffin content

NASA Astrophysics Data System (ADS)

Tung, N. P.; Vinh, N. Q.; Phong, N. T. P.; Long, B. Q. K.; Hung, P. V.

2003-04-01

Controlling the paraffin deposition is one of the most serious and costly problems for high-paraffin crude-oil production and transportation. This holds especially for offshore, deep-water wells and pipelines, like in Vietnam. For finding solutions for these problems, a series of experiments has been performed in order to study the effects of a magnetic field on the rheology of two often produced crude oil samples, using the high and variable magnetic-flux density of a Nd-Fe-B magnet. The resulting changes in the essential characteristics of the magnetically treated (MT) crude oils, like form and size of the paraffin clusters as well as the rheology parameters, have definitely proved the possibility to use a Nd-Fe-B magnetic tool as an environmentally friendly and effective method to control the paraffin deposition in crude oils of Vietnam that have a high paraffin content.

Cryogenic Permanent Magnet Undulators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chavanne, J.; Lebec, G.; Penel, C.

For an in-vacuum undulator operated at small gaps the permanent magnet material needs to be highly resistant to possible electron beam exposure. At room temperature, one generally uses Sm{sub 2}Co{sub 17} or high coercivity NdFeB magnets at the expense of a limited field performance. In a cryogenic permanent magnet undulator (CPMU), at a temperature of around 150 K, any NdFeB grade reveals a coercivity large enough to be radiation resistant. In particular, very high remanence NdFeB material can be used to build undulators with enhanced field and X-ray brilliance at high photon energy provided that the pre-baking of the undulatormore » above 100 deg. C can be eliminated. The ESRF has developed a full scale 2 m long CPMU with a period of 18 mm. This prototype has been in operation on the ID6 test beamline since January 2008. A significant effort was put into the characterization of NdFeB material at low temperature, the development of dedicated magnetic measurement systems and cooling methods. The measured heat budget with beam is found to be larger than expected without compromising the smooth operation of the device. Leading on from this first experience, new CPMUs are currently being considered for the upgrade of the ESRF.« less

Angular dependence of coercivity in isotropically aligned Nd-Fe-B sintered magnets

NASA Astrophysics Data System (ADS)

Matsuura, Yutaka; Nakamura, Tetsuya; Sumitani, Kazushi; Kajiwara, Kentaro; Tamura, Ryuji; Osamura, Kozo

2018-05-01

In order to understand the coercivity mechanism in Nd-Fe-B sintered magnets, the angular dependence of the coercivity of an isotropically aligned Nd15Co1.0B6Febal. sintered magnet was investigated through magnetization measurements using a vibrating sample magnetometer. These results are compared with the angular dependence calculated under the assumption that the magnetization reversal of each grain follows the Kondorskii law or, in other words, the 1/cos θ law for isotropic alignment distributions. The calculated angular dependence of the coercivity agrees very well with the experiment for magnetic fields applied between angles of 0 and 60°, and it is expected that the magnetization reversal occurs in each grain individually followed the 1/cos θ law. In contrast, this agreement between calculation and experiment is not found for anisotropic Nd-Fe-B samples. This implies that the coercivity of the aligned magnets depends upon the de-pinning of the domain walls from pinning sites. When the de-pinning occurs, it is expected that the domain walls are displaced through several grains at once.

Effects of Mg nanopowders intergranular addition on the magnetic properties and corrosion resistance of sintered Nd-Fe-B

NASA Astrophysics Data System (ADS)

Li, Zhi-jie; Wang, Xiao-er; Li, Jia-yang; Li, Jia; Wang, Hong-zhi

2017-11-01

In order to improve the magnetic properties and corrosion resistance of sintered Nd-Fe-B magnets, the (PrNd)29.9Dy0.1B1Co1Cu0.15Febal (wt%) powders were mixed with Mg nanopowders, as grain boundary modifiers. For Nd-Fe-B magnets with 0.1-0.4 wt% Mg addition, the result showed that addition amount of 0.1 wt% Mg, Hcj reaches the maximum value of 999.1 kA/m, Br reaches 1.436T, (BH)max reaches 396.9 kJ/m3 and magnet density is 7.42 g/cm3, which are related to the microstructural modification of grain boundaries and the magnet density. Effects of Mg addition on corrosion behavior in sulphuric acid and sodium chloride solution were researched by electrochemical workstation. With increase of Mg addition level, the magnet turns to have a higher corrosion potential and lower corrosion current density, the corrosion poverty is improved. However, temperature coefficient remained nearly unchanged with Mg addition.

Selective Extraction and Recovery of Nd and Dy from Nd-Fe-B Magnet Scrap by Utilizing Molten MgCl2

NASA Astrophysics Data System (ADS)

Shirayama, Sakae; Okabe, Toru H.

2018-06-01

Fundamental experiments are conducted with the aim of developing an efficient recycling process for rare earth elements (REEs) from neodymium-iron-boron (Nd-Fe-B) permanent magnet scrap. Molten magnesium dichloride (MgCl2) was chosen as an extraction medium, which can selectively chlorinate and extract REEs in magnet alloys. Dysprosium-containing Nd-Fe-B magnet alloy was immersed in molten MgCl2 at 1273 K (1000 °C) for 3 to 12 hours. The results of the experiments clearly show that the REEs in the magnetic alloy were successfully extracted into the molten salt, while the Fe-B alloy remained in a solid form. The extraction ratios of Nd and Dy were at most 87 and 78 mass pct, respectively. After the extraction experiment, excess MgCl2 and Mg were removed by vacuum distillation and the rare earth chlorides were recovered. Thus, the feasibility of this method for efficient recovery of rare earths using molten MgCl2 is demonstrated.

Selective Extraction and Recovery of Nd and Dy from Nd-Fe-B Magnet Scrap by Utilizing Molten MgCl2

NASA Astrophysics Data System (ADS)

Shirayama, Sakae; Okabe, Toru H.

2018-02-01

Fundamental experiments are conducted with the aim of developing an efficient recycling process for rare earth elements (REEs) from neodymium-iron-boron (Nd-Fe-B) permanent magnet scrap. Molten magnesium dichloride (MgCl2) was chosen as an extraction medium, which can selectively chlorinate and extract REEs in magnet alloys. Dysprosium-containing Nd-Fe-B magnet alloy was immersed in molten MgCl2 at 1273 K (1000 °C) for 3 to 12 hours. The results of the experiments clearly show that the REEs in the magnetic alloy were successfully extracted into the molten salt, while the Fe-B alloy remained in a solid form. The extraction ratios of Nd and Dy were at most 87 and 78 mass pct, respectively. After the extraction experiment, excess MgCl2 and Mg were removed by vacuum distillation and the rare earth chlorides were recovered. Thus, the feasibility of this method for efficient recovery of rare earths using molten MgCl2 is demonstrated.

Electrochemical corrosion behavior, microstructure and magnetic properties of sintered Nd-Fe-B permanent magnet doped by CuZn5 powders

NASA Astrophysics Data System (ADS)

Liu, W. Q.; Wang, Z.; Sun, C.; Yue, M.; Liu, Y. Q.; Zhang, D. T.; Zhang, J. X.

2014-05-01

Nd-Fe-B permanent magnets with a small amount of CuZn5 powders doping were prepared by conventional sintered method. The effects of CuZn5 contents on magnetic properties and microstructure, electrochemical corrosion resistance of sintered Nd-Fe-B magnets were systematically studied. The results show that the magnetic properties of magnets do not have a significant variation by CuZn5 powders doping; the coercivity of magnets rises gradually, while the remanence of the magnets decreases a little with increasing of the CuZn5 amount. The CuZn5 doped magnets have more positive corrosion potential, Ecorr, and much lower corrosion current density, icorr, than the magnets without CuZn5 doping, indicating CuZn5 doping could improve the corrosion resistance. Both Zn and Cu enrich mainly into the Nd-rich phase, fully improve the wettability between the Nd-rich phase and the Nd2Fe14B phase, and repair the defects of the main phase, so the coercivity of magnets doped with CuZn5 powders rises. Such microstructure modification effectively restrains the aggressive inter-granular corrosion. As a result, the CuZn5 doped magnet possesses excellent corrosion resistance in NaCl electrolyte.

Monitoring long-term evolution of engineered barrier systems using magnets: Magnetic response.

PubMed

Rigonat, N; Isnard, O; Harley, S L; Butler, I B

2018-01-05

Remote and non-destructive monitoring of the stability and performance of Engineered Barrier Systems for Geological Disposal Facility of is gaining considerable importance in establishing the safety cases for Higher Activity Wastes disposal. This study offers an innovative use of mineral magnetism for monitoring groundwater saturation of the barrier. Four mixtures of permanent magnets (Nd-Fe-B, coated and uncoated; SmCo and AlNiCo) and bentonite were reacted for 4, 8 and 12 months with mildly-saline, high-pH leachates, representing the fluids saturating a time-evolved engineered barrier. Coupled hysteresis and thermomagnetic analyses demonstrate how Nd-Fe-B feature a time-dependent transition from square-like ferromagnetic to superparamagnetic loop via pot-bellied and wasp-waist loops, whereas SmCo and AlNiCo do not show so extensive corrosion-related variations of the intrinsic and extrinsic magnetic properties. This study allowed to identify magnetic materials suitable for shorter- (Nd-Fe-B) and longer-term (SmCo and AlNiCo) monitoring purposes. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Novel hydrogen decrepitation behaviors of (La, Ce)-Fe-B strips

NASA Astrophysics Data System (ADS)

Jin, Jiaying; Bai, Guohua; Zhang, Yujing; Peng, Baixing; Liu, Yongsheng; Ma, Tianyu; Yan, Mi

2018-05-01

La and Ce substitution for Nd in the 2:14:1-type sintered magnet is of commercial interest to reduce the material cost and to balance the utilization of rare earth (RE) sources. As hydrogen decrepitation (HD) is widely utilized to prepare the magnetic powders during magnets fabrication, incorporating La and Ce into the Nd-Fe-B permanent magnets, however, may exert complex influences on the decrepitation behavior. In the present work, through a comparative study of the HD behaviors between the (La, Ce)-Fe-B strips and the conventional Nd-Fe-B ones, we find that similar to the Nd-Fe-B system, increasing hydrogen pressures from 2.5 to 5.5 MPa do not break the 2:14:1 tetragonal structure of (La, Ce)-Fe-B strips. The enhanced hydrogen absorption behaviors are observed with increasing pressure, which are still inferior to that of the Nd-Fe-B strips. This should be ascribed to the higher oxygen affinity of La and Ce than that of Nd, leading to the decreased amount of active RE-rich phase and limited hydrogen diffusion channel. As a result, the hydrogen absorption of 2:14:1 matrix phase is significantly suppressed, dramatically weakening the exothermic effect. This finding suggests that La and Ce with stable 2:14:1 tetragonal structure upon HD process are promising alternatives for Nd, despite that more precise oxygen control is necessary for the microstructure modification and magnetic performance enhancement of (La, Ce)-Fe-B sintered magnets.

Prediction of the new efficient permanent magnet SmCoNiFe3

NASA Astrophysics Data System (ADS)

Söderlind, P.; Landa, A.; Locht, I. L. M.; Åberg, D.; Kvashnin, Y.; Pereiro, M.; Däne, M.; Turchi, P. E. A.; Antropov, V. P.; Eriksson, O.

2017-09-01

We propose a new efficient permanent magnet, SmCoNiFe3, which is a development of the well-known SmCo5 prototype. More modern neodymium magnets of the Nd-Fe-B type have an advantage over SmCo5 because of their greater maximum energy products due to their iron-rich stoichiometry. Our new magnet, however, removes most of this disadvantage of SmCo5 while preserving its superior high-temperature efficiency over the neodymium magnets. We show by means of first-principles electronic-structure calculations that SmCoNiFe3 has very favorable magnetic properties and could therefore potentially replace SmCo5 or Nd-Fe-B types in various applications.

Corrosion Protection of Nd-Fe Magnets via Phophatization, Silanization and Electrostatic Spraying with Organic Resin Composite Coatings

NASA Astrophysics Data System (ADS)

Ding, Xia; Li, Jingjie; Li, Musen; Ge, Shengsong; Wang, Xiuchun; Ding, Kaihong; Cui, Shengli; Sun, Yongcong

2014-09-01

Nd-Fe-B permanent magnets possess excellent properties. However, they are highly sensitive to the attack of corrosive environment. The aim of this work is to improve the corrosion resistance of the magnets by phosphatization, silanization, and electrostatic spraying with organic resin composite coatings. Field emission scanning electron microscope (FE-SEM) and energy dispersive spectrometer (EDS) tests showed that uniform phosphate conversion coatings and spray layers were formed on the surface of the Nd-Fe-B magnets. Neutral salt spray tests exhibited that, after treated by either phosphating, silanization or electrostatic spraying, the protectiveness of Nd-Fe-B alloys was apparently increased. And corrosion performance of magnets treated with silane only was slightly inferior to those of phosphatized ones. However, significant improvement in corrosion protection was achieved after two-step treatments, i.e. by top-coating spray layer with phosphate or silane films underneath. Grid test indicated that the phosphate and silane coating were strongly attached to the substrate while silane film was slightly weaker than the phosphate-treated ones. Magnetic property analysis revealed phosphatization, silanization, and electrostatic spraying caused decrease in magnetism, but silanization had the relatively smaller effect.

Synthesis of hard magnetic Mn3Ga micro-islands by e-beam evaporation

NASA Astrophysics Data System (ADS)

Akdogan, O.

2018-05-01

The permanent magnet industry heavily depends on Nd-Fe-B and Sm-Co alloys because of their high-energy product and high room temperature coercivity. Main ingredient for having such superior magnetic properties compared to other known ferromagnetic materials is rare earth elements (Nd, Sm, Dy…). However recent worldwide reserve and export limitation problem of rare earths, shifted researchers' focus to rare earth free permanent magnets. Among many alternatives (FePt, Zr2Co11, FeNi …), Mn-based alloys are the most suitable due to abundance of the forming elements and trivial formation of the necessary hard phases. In this study, Mn3Ga micro islands have been prepared. Mn3Ga owes its hard magnetic properties to tetragonal D022 phase with magnetic anisotropy energy of 2 MJ/m3. Thin films and islands of Cr/MnGa/Cr layers have been deposited on Si/SiO2 wafers using combination of e-beam and thermal evaporation techniques. Cr has been used as buffer and cover layer to protect the sample from the substrate and prevent oxidation during annealing. Annealing under Ar/H2 forming gas has been performed at 350oC for 10 min. Nano thick islands of 25, 50 and 100 μm lateral size have been produced by photolithography technique. Room temperature coercivity of 7.5 kOe has been achieved on 100 μm micro islands of Mn3Ga. Produced micro islands could be a rare earth free alternative for magnetic memory and MEMS applications.

Magnetic properties of the surface layer and its magnetic interaction with the interior of Nd-Fe-B sintered magnets

NASA Astrophysics Data System (ADS)

Kobayashi, Kurima; Nakamura, Michi-hide; Urushibata, Kimiko

2015-05-01

The magnetization and demagnetization mechanisms in the mechanically polished surface layers (SL) of the c-plane and a-b plane of Nd-Fe-B sintered magnets were investigated. The magnetic interaction between the SL and the interior of the magnet was clarified by using vibrating sample magnetometer measurements of a whole sample and magneto-force microscopy observations of the domain structure of the SL layer. The polishing eliminated the Nd-rich grain boundary phases, which was only about 2 nm thick, from the SL crystal grains in the sintered magnets. The a-b plane polishing caused the independent magnetic reversal of the a-b plane SL, which was about 5.5 μm thick, as in the platy samples. The coercivities (μ0Hc) of the SL were less than 0.3 T. In contrast, the c-plane polishing did not produce independent magnetic reversal of the SL, although the coercivity of bulk samples was clearly decreased by the formation of the c-plane SL. The grains in the SL should form clusters that alter the demagnetizing factors, depending on the shape of cluster as a magnetic unit. The magnetic interaction among the SL crystal grains is expected to play an important role in the coercivity mechanism of Nd-Fe-B sintered magnets.

Hydrogen Decrepitation Press-Less Process recycling of NdFeB sintered magnets

NASA Astrophysics Data System (ADS)

Xia, Manlong; Abrahamsen, Asger B.; Bahl, Christian R. H.; Veluri, Badrinath; Søegaard, Allan I.; Bøjsøe, Poul

2017-11-01

A Hydrogen Decrepitation Press-Less Process (HD-PLP) recycling method for recycling of anisotropic NdFeB magnets is demonstrated. The method combines hydrogen decrepitation (HD) disintegration of the initial magnet, powder sieving and the Press-Less Process (PLP), where hydride powder is sintered in a graphite mold. Coercivities up to 534 kA/m were obtained in porous samples based on powder size d < 100 μm. Adding a ball milling step resulted in full density isotropic magnets for d > 100 μm. The coercivity reached Hci = 957 kA/m being 86% of the original N48M material without addition of rare earth elements.

Coercivity degradation caused by inhomogeneous grain boundaries in sintered Nd-Fe-B permanent magnets

NASA Astrophysics Data System (ADS)

Chen, Hansheng; Yun, Fan; Qu, Jiangtao; Li, Yingfei; Cheng, Zhenxiang; Fang, Ruhao; Ye, Zhixiao; Ringer, Simon P.; Zheng, Rongkun

2018-05-01

Quantitative correlation between intrinsic coercivity and grain boundaries in three dimensions is critical to further improve the performance of sintered Nd-Fe-B permanent magnets. Here, we quantitatively reveal the local composition variation across and especially along grain boundaries using the powerful atomic-scale analysis technique known as atom probe tomography. We also estimate the saturation magnetization, magnetocrystalline anisotropy constant, and exchange stiffness of the grain boundaries on the basis of the experimentally determined structure and composition. Finally, using micromagnetic simulations, we quantify the intrinsic coercivity degradation caused by inhomogeneous grain boundaries. This approach can be applied to other magnetic materials for the analysis and optimization of magnetic properties.

Soapnut extract mediated synthesis of nanoscale cobalt substituted NdFeB ferromagnetic materials and their characterization

NASA Astrophysics Data System (ADS)

Rao, G. V. S. Jayapala; Prasad, T. N. V. K. V.; Shameer, Syed; Rao, M. Purnachandra

2018-04-01

Neodymium iron boron (NdFeB) permanent magnets have high energy product with suitable magnetic and physical properties for an array of applications including power generation and motors. However, synthetic routes of NdFeB permanent magnets involve critical procedures with high energy and needs scientific skills. Herein, we report on soapnut extract mediated synthesis of nanoscale cobalt substituted NdFeB (Co-NdFeB) permanent magnetic powders (Nd: 15%, Fe: 77.5%, B: 7.5% and Co with molar ratios: 0.5, 1, 1.5 and 2). A 10 ml of 10% soapnut extract was added to 90 ml of respective chemical composition and heated to 60 °C for 30 min and aged for 24 h. The dried powder was sintered at 500 °C for 1 h. The characterization of the prepared nanoscale Co-NdFeB magnetic powders was done using the techniques such as Dynamic Light Scattering (DLS for size and zeta potential measurements), X-ray diffraction (XRD) for structural determination, Scanning electron microscopy (SEM) with energy dispersion spectroscopy (EDS) for surface morphological and elemental analysis, Fourier transform infrared spectroscopy (FT-IR) for the identification of functional groups associated and hysteresis loop studies to quantify the magnetization. The results revealed that particles were in irregular and tubular shaped and highly stable (Zeta potential: -44.4 mV) with measured size <100 nm. XRD micrographs revealed a tetragonal crystal structure and FTIR showed predominant N-H and O-H stretching indicates the involvement of these functional groups in the reduction and stabilization process of Co-NdFeB magnetic powders. Hysteresis studies signify the effect of an increase in Co concentration.

Preparation and properties of isotropic Nd-Fe-B bonded magnets with sodium silicate binder

NASA Astrophysics Data System (ADS)

Liu, W. Q.; Hu, R. J.; Yue, M.; Yin, Y. X.; Zhang, D. T.

2017-08-01

In present study, sodium silicate, a kind of heat-resistant binder, was used to prepare bonded Nd-Fe-B magnets with improved thermal stability and mechanical strength. Effect of curing temperature and curing time of the new binder to the magnetic properties, microstructure, and mechanical strength of the magnets was systematically investigated. Fracture surface morphology observation show that sodium silicate in bonded magnets could completely be cured at 175 °C for 40 min, and the magnets prepared under this condition exhibit optimal properties. They exhibit usable magnetic properties of Br of 4.66 kGs, Hcj of 4.84 kOe, and (BH)max of 4.06 MGOe at 200 °C. Moreover, the magnets possess high compressive strength of 63 MPa.

Prediction of the new efficient permanent magnet SmCoNiFe 3

DOE PAGES

Soderlind, P.; Landa, A.; Locht, I. L. M.; ...

2017-09-14

Here, we propose a new efficient permanent magnet, SmCoNiFe 3, which is a development of the well-known SmCo 5 prototype. More modern neodymium magnets of the Nd-Fe-B type have an advantage over SmCo 5 because of their greater maximum energy products due to their iron-rich stoichiometry. Our new magnet, however, removes most of this disadvantage of SmCo 5 while preserving its superior high-temperature efficiency over the neodymium magnets. We show by means of first-principles electronic-structure calculations that SmCoNiFe 3 has very favorable magnetic properties and could therefore potentially replace SmCo 5 or Nd-Fe-B types in various applications.

A combined experimental and finite element analysis method for the estimation of eddy-current loss in NdFeB magnets.

PubMed

Fratila, Radu; Benabou, Abdelkader; Tounzi, Abdelmounaïm; Mipo, Jean-Claude

2014-05-14

NdFeB permanent magnets (PMs) are widely used in high performance electrical machines, but their relatively high conductivity subjects them to eddy current losses that can lead to magnetization loss. The Finite Element (FE) method is generally used to quantify the eddy current loss of PMs, but it remains quite difficult to validate the accuracy of the results with complex devices. In this paper, an experimental test device is used in order to extract the eddy current losses that are then compared with those of a 3D FE model.

Big Area Additive Manufacturing of High Performance Bonded NdFeB Magnets

NASA Astrophysics Data System (ADS)

Li, Ling; Tirado, Angelica; Nlebedim, I. C.; Rios, Orlando; Post, Brian; Kunc, Vlastimil; Lowden, R. R.; Lara-Curzio, Edgar; Fredette, Robert; Ormerod, John; Lograsso, Thomas A.; Paranthaman, M. Parans

2016-10-01

Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm3, and the room temperature magnetic properties are: intrinsic coercivity Hci = 688.4 kA/m, remanence Br = 0.51 T, and energy product (BH)max = 43.49 kJ/m3 (5.47 MGOe). In addition, tensile tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. The present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials.

Big Area Additive Manufacturing of High Performance Bonded NdFeB Magnets

PubMed Central

Li, Ling; Tirado, Angelica; Nlebedim, I. C.; Rios, Orlando; Post, Brian; Kunc, Vlastimil; Lowden, R. R.; Lara-Curzio, Edgar; Fredette, Robert; Ormerod, John; Lograsso, Thomas A.; Paranthaman, M. Parans

2016-01-01

Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm3, and the room temperature magnetic properties are: intrinsic coercivity Hci = 688.4 kA/m, remanence Br = 0.51 T, and energy product (BH)max = 43.49 kJ/m3 (5.47 MGOe). In addition, tensile tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. The present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials. PMID:27796339

Big Area Additive Manufacturing of High Performance Bonded NdFeB Magnets.

PubMed

Li, Ling; Tirado, Angelica; Nlebedim, I C; Rios, Orlando; Post, Brian; Kunc, Vlastimil; Lowden, R R; Lara-Curzio, Edgar; Fredette, Robert; Ormerod, John; Lograsso, Thomas A; Paranthaman, M Parans

2016-10-31

Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm 3 , and the room temperature magnetic properties are: intrinsic coercivity H ci  = 688.4 kA/m, remanence B r  = 0.51 T, and energy product (BH) max  = 43.49 kJ/m 3 (5.47 MGOe). In addition, tensile tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. The present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials.

Big area additive manufacturing of high performance bonded NdFeB magnets

DOE PAGES

Li, Ling; Tirado, Angelica; Nlebedim, I. C.; ...

2016-10-31

Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm3, and the room temperature magnetic propertiesmore » are: intrinsic coercivity Hci = 688.4 kA/m, remanence B r = 0.51 T, and energy product (BH) max = 43.49 kJ/m 3 (5.47 MGOe). In addition, tensile tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. As a result, the present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials.« less

Big area additive manufacturing of high performance bonded NdFeB magnets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Ling; Tirado, Angelica; Nlebedim, I. C.

Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm3, and the room temperature magnetic propertiesmore » are: intrinsic coercivity Hci = 688.4 kA/m, remanence B r = 0.51 T, and energy product (BH) max = 43.49 kJ/m 3 (5.47 MGOe). In addition, tensile tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. As a result, the present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials.« less

Current status and recent topics of rare-earth permanent magnets

NASA Astrophysics Data System (ADS)

Sugimoto, S.

2011-02-01

After the development of Nd-Fe-B magnets, rare-earth magnets are now essential components in many fields of technology, because of their ability to provide a strong magnetic flux. There are two, well-established techniques for the manufacture of rare earth magnets: powder metallurgy is used to obtain high-performance, anisotropic, fully dense magnet bodies; and the melt-spinning or HDDR (hydrogenation, disproportionation, desorption and recombination) process is widely used to produce magnet powders for bonded magnets. In the industry of sintered Nd-Fe-B magnets, the total amount of production has increased and their dominant application has been changed to motors. In particular, their use for motors in hybrid cars is one of the most attractive applications. Bonded magnets have also been used for small motors, and the studies of nanocomposite and Sm-Fe-N magnets have become widespread. This paper reviews the current status and future trend in the research of permanent magnets.

One pot synthesis of exchange coupled Nd2Fe14B/alpha-Fe by pechini type sol-gel method.

PubMed

Hussain, Abid; Jadhav, Abhijit P; Baek, Yeon Kyung; Choi, Hul Jin; Lee, Jaeho; Kang, Young Soo

2013-11-01

In this work, a combination of nanoparticles of Nd2Fe14B hard magnetic phase and alpha-Fe soft magnetic phase were synthesized by one pot chemical synthesis technique using sol-gel method. A gel of Nd-Fe-B was prepared using NdCl3 x 6H2O, FeCl3 x 6H2O, H3BO3, citric acid, and ethylene glycol by pechini type sol-gel method. The gel was subsequently calcined and annealed to obtain the mixed oxide powders. The produced metal oxide particles were identified with XRD, SEM, TEM to obtain the crystal structure, shape and domain structure of them. The nanoparticles of mixed phase of Nd2Fe14B/alpha-Fe were obtained from these oxides by a process of reduction-diffusion in vacuum by employing CaH2 as reducing agent. During this process it was optimized by controlling temperature, reaction time and concentration of the reducing agent (CaH2). The phase formation of Nd2Fe14B was resulted by the direct diffusion of NdH2, Fe and B. The magnetic property of produced hard and soft phases was successfully identified with vibrating sample magnetometer (VSM). The mixed domains of the hard and soft phases were identified with selected area electron diffraction method (SAED) patterns.

Method for forming permanent magnets with different polarities for use in microelectromechanical devices

DOEpatents

Roesler, Alexander W [Tijeras, NM; Christenson, Todd R [Albuquerque, NM

2007-04-24

Methods are provided for forming a plurality of permanent magnets with two different north-south magnetic pole alignments for use in microelectromechanical (MEM) devices. These methods are based on initially magnetizing the permanent magnets all in the same direction, and then utilizing a combination of heating and a magnetic field to switch the polarity of a portion of the permanent magnets while not switching the remaining permanent magnets. The permanent magnets, in some instances, can all have the same rare-earth composition (e.g. NdFeB) or can be formed of two different rare-earth materials (e.g. NdFeB and SmCo). The methods can be used to form a plurality of permanent magnets side-by-side on or within a substrate with an alternating polarity, or to form a two-dimensional array of permanent magnets in which the polarity of every other row of the array is alternated.

Effect of Partial Substitution of Neodymium with Praseodymium on the Magnetic and Process Properties of Sintered Magnets of Type NdFeB

NASA Astrophysics Data System (ADS)

Dormidontov, N. A.; Dormidontov, A. G.; Lileev, A. S.; Kamynin, A. V.; Lukin, A. A.

2017-01-01

The effect of substitution of neodymium with praseodymium in sintered magnets of type NdFeB on their magnetic and process properties in the concentration range of [Pr] = 0 - 13 wt.% is studied. The special features of milling of the alloys, sintering processes and heat treatments in the production of magnets containing praseodymium are discussed. Hysteresis characteristics of B r ≥ 1.2 T, H cJ ≥ 1200 kA/m, H cb ≥ 880 kA/m, H k ≥ 960 kA/m, and BH max ≥ 280 kJ/m3 are obtained for magnets with composition (in wt.%) 33 Nd, 10 Pr, 1.5 (Ti + Al + Cu), 1.3 B, the remainder Fe.

The effect of surface grain reversal on the AC losses of sintered Nd-Fe-B permanent magnets

NASA Astrophysics Data System (ADS)

Moore, Martina; Roth, Stefan; Gebert, Annett; Schultz, Ludwig; Gutfleisch, Oliver

2015-02-01

Sintered Nd-Fe-B magnets are exposed to AC magnetic fields in many applications, e.g. in permanent magnet electric motors. We have measured the AC losses of sintered Nd-Fe-B magnets in a closed circuit arrangement using AC fields with root mean square-values up to 80 mT (peak amplitude 113 mT) over the frequency range 50 to 1000 Hz. Two magnet grades with different dysprosium content were investigated. Around the remanence point the low grade material (1.7 wt% Dy) showed significant hysteresis losses; whereas the losses in the high grade material (8.9 wt% Dy) were dominated by classical eddy currents. Kerr microscopy images revealed that the hysteresis losses measured for the low grade magnet can be mainly ascribed to grains at the sample surface with multiple domains. This was further confirmed when the high grade material was subsequently exposed to DC and AC magnetic fields. Here a larger number of surface grains with multiple domains are also present once the step in the demagnetization curve attributed to the surface grain reversal is reached and a rise in the measured hysteresis losses is evident. If in the low grade material the operating point is slightly offset from the remanence point, such that zero field is not bypassed, its AC losses can also be fairly well described with classical eddy current theory.

Evaluation of the attractive force of different types of new-generation magnetic attachment systems.

PubMed

Akin, Hakan; Coskun, M Emre; Akin, E Gulsah; Ozdemir, A Kemal

2011-03-01

Rare earth magnets have been used in prosthodontics, but their tendency for corrosion in the oral cavity and insufficient attractive forces limit long-term clinical application. The purpose of this study was to evaluate the attractive force of different types of new-generation magnetic attachment systems. The attractive force of the neodymium-iron-boron (Nd-Fe-B) and samarium-cobalt (Sm-Co) magnetic attachment systems, including closed-field (Hilop and Hicorex) and open-field (Dyna and Steco) systems, was measured in a universal testing machine (n=5). The data were statistically evaluated with 1-way ANOVA and post hoc Tukey-Kramer multiple comparison test (α=.05). The closed-field systems exhibited greater (P<.001) attractive force than the open-field systems. Moreover, there was a statistically significant difference in attractive force between Nd-Fe-B and Sm-Co magnets (P<.001). The strongest attractive force was found with the Hilop system (9.2 N), and the lowest force was found with the Steco system (2.3 N). The new generation of Nd-Fe-B closed-field magnets, along with improved technology, provides sufficient denture retention for clinical application. Copyright © 2011 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

A Lightweight Loudspeaker for Aircraft Communications and Active Noise Control

NASA Technical Reports Server (NTRS)

Warnaka, Glenn E.; Kleinle, Mark; Tsangaris, Parry; Oslac, Michael J.; Moskow, Harry J.

1992-01-01

A series of new, lightweight loudspeakers for use on commercial aircraft has been developed. The loudspeakers use NdFeB magnets and aluminum alloy frames to reduce the weight. The NdFeB magnet is virtually encapsulated by steel in the new speaker designs. Active noise reduction using internal loudspeakers was demonstrated to be effective in 1983. A weight, space, and cost efficient method for creating the active sound attenuating fields is to use the existing cabin loudspeakers for both communication and sound attenuation. This will require some additional loudspeaker design considerations.

Alternatives to Rare Earth Permanent Magnets for Energy Harvesting Applications

NASA Astrophysics Data System (ADS)

Khazdozian, Helena; Hadimani, Ravi; Jiles, David

Direct-drive permanent magnet generators (DDPMGs) offer increased reliability and efficiency over the more commonly used geared doubly-fed induction generator, yet are only employed in less than 1 percent of utility scale wind turbines in the U.S. One major barrier to increased deployment of DDPMGs in the U.S. wind industry is NdFeB permanent magnets (PMs), which contain critical rare earth elements Nd and Dy. To allow for the use of rare earth free PMs, the magnetic loading, defined as the average magnetic flux density over the rotor surface, must be maintained. Halbach cylinders are employed in 3.5kW Halbach PMGs (HPMGs) of varying slot-to-pole ratio to concentrate the magnetic flux output by a lower energy density PM over the rotor surface. We found that for high pole and slot number, the increase in magnetic loading is sufficient to allow for the use of strontium iron oxide hard ferrite PMs and achieved rated performance. Joule losses in the stator windings were found to increase for the hard ferrite PMs due to increased inductance in the stator windings. However, for scaling of the HPMG designs to 3MW, rated performance and high efficiency were achieved, demonstrating the potential for elimination for rare earth PMs in commercial scale wind turbines. This work was supported by the National Science Foundation under Grant No. 1069283 and a Barbara and James Palmer Endowment at Iowa State University.

Corrosion and protection of NdFeB type magnets

NASA Astrophysics Data System (ADS)

Cavalloti, P.; Bozzini, B.; Cecchini, R.; Bava, G. F.; Davies, H. A.; Hoggarth, C.

1992-02-01

A general mechanism for the corrosion behaviour of NdFeB magnets is presented, related to the magnet heterogeneity with the presence of different phases. Cathodic control is outlined. An electrochemical method to assess the corrosion resistance of magnets, with and without coatings, is proposed; it is based on the study of the transient voltage at the magnet surface after a second cathodic current pulse in a suitable aggressive solution and its dependence on the amount of cathodic current circulating. Suitable pretreatments have been tried and interesting results obtained with passivation pretreatments, giving phosphorous Nd at grain boundaries. Coatings if sintered and plastic magnets have been tried using several methods. Good results are obtained with Zn-Co layers on sintered magnets and a sol-gel glass on powders for plastic magnets. Improved ACS (Autocatalytic Chemical Deposition) Ni=P coatings have been realized, with an alkaline brass flash plating to start ACD deposition.

Efficient reuse of the waste sintered NdFeB magnet with Dy2O3 addition

NASA Astrophysics Data System (ADS)

Li, Chencheng; Sun, Aizhi; Tian, Zhenya; Zhang, Xun; Ma, Bin

2018-09-01

In this paper, the efficient recycling method of sintered NdFeB waste was studied. The production process can be greatly simplified by crushing the recovered waste magnet into hundreds of micron-sized magnetic powder and preparing the magnet directly with orientating, molding and sintering. The magnetic properties of the magnet prepared by commercial N45 recovered waste can reach Br = 1.09 T, (BH)max = 196 kJ/m3 and Hcj = 601 kA/m. Adding a small amount of Dy2O3 can significantly improve the Br of the above magnet. The maximum Hcj can reach 1310 kA/m and (BH)max can reach 204 kJ/m3. The microstructure analysis shows that Dy2O3 diffused along the grain boundaries mainly and forms Dy-rich shell around the Nd2Fe14B grains which increase the difficulty of forming anti-magnetization.

A novel method combining additive manufacturing and alloy infiltration for NdFeB bonded magnet fabrication

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Ling; Tirado, Angelica; Conner, Benjamin S.

In this paper, binder jetting additive manufacturing technique is employed to fabricate NdFeB isotropic bonded magnets, followed by an infiltration process with low-melting point eutectic alloys [i.e., Nd 3Cu 0.25Co 0.75 (NdCuCo) and Pr 3Cu 0.25Co 0.75 (PrCuCo)]. Densification and mechanical strength improvement are achieved for the as-printed porous part. Meanwhile, the intrinsic coercivity H ci is enhanced from 732 to 1345 kA/m and 1233 kA/m after diffusion of NdCuCo and PrCuCo, respectively. This study presents a novel method for fabricating complex-shaped bonded magnets with promising mechanical and magnetic properties.

A novel method combining additive manufacturing and alloy infiltration for NdFeB bonded magnet fabrication

DOE PAGES

Li, Ling; Tirado, Angelica; Conner, Benjamin S.; ...

2017-04-27

In this paper, binder jetting additive manufacturing technique is employed to fabricate NdFeB isotropic bonded magnets, followed by an infiltration process with low-melting point eutectic alloys [i.e., Nd 3Cu 0.25Co 0.75 (NdCuCo) and Pr 3Cu 0.25Co 0.75 (PrCuCo)]. Densification and mechanical strength improvement are achieved for the as-printed porous part. Meanwhile, the intrinsic coercivity H ci is enhanced from 732 to 1345 kA/m and 1233 kA/m after diffusion of NdCuCo and PrCuCo, respectively. This study presents a novel method for fabricating complex-shaped bonded magnets with promising mechanical and magnetic properties.

Influence of annealing temperature on the Dy diffusion process in NdFeB magnets

NASA Astrophysics Data System (ADS)

Hu, Sheng-qing; Peng, Kun; Chen, Hong

2017-03-01

Sintered NdFeB magnets were coated with a layer of Dy metal using electron beam evaporation method and then annealed at various temperatures to investigate the temperature dependence of Dy diffusion process in NdFeB magnets. A Dy-rich phase was observed along the grain boundaries after the grain boundary diffusion process, the diffusion coefficients of various temperatures were obtained, the diffusion coefficients of Dy along the grain boundaries at 800 °C and 900 °C were determined to be 9.8×10-8 cm2 s-1 and 2.4×10-7 cm2 s-1, respectively. The diffusion length depended on the annealing temperature and the maximum diffusion length of approximately 1.8 mm and 3.0 mm can be obtained after annealing at 800 °C and 900 °C for 8 h. Higher diffusion temperature results in the diffusion not only along the grain boundaries but also into grains and then decrease in magnetic properties. The optimum annealing conditions can be determined as 900 °C for 8 h. The coercivity was improved from 1040 kA/m to 1450 kA/m and its magnetization has no significant reduction after the grain boundary diffusion process at the optimum annealing conditions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

He Yongzhou; Zhang Jidong; Zhou Qiaogen

Two in-vacuum undulators IVU25s and one elliptically polarized undulator EPU100 have been developed for SSRF. Two IVU25s with the same hybrid design contain about 640 Sm{sub 2}Co{sub 17} magnet blocks and the dimension of blocks is 65 Wx25 Hx9 D. The EPU100 of the APPLE-II type contains about 690 NdFeB magnet blocks with the dimension of 35 Wx35 Hx25 D. This paper describes the magnetic measurements of these magnet blocks with the Helmholtz coil measurement system for IVU25 magnet blocks and the Hall probe measurement system for EPU100 magnet blocks. The measured maximum magnetic moment deviation and the maximum anglemore » deviation are less than {+-}1.0% and 1.1 deg. respectively both for Sm{sub 2}Co{sub 17} blocks and NdFeB blocks and satisfy the specifications of undulators.« less

The origin of coercivity decrease in fine grained Nd-Fe-B sintered magnets

NASA Astrophysics Data System (ADS)

Li, W. F.; Ohkubo, T.; Hono, K.; Sagawa, M.

2009-04-01

Microstructures of fine grained Nd-Fe-B sintered magnets that were produced by the pressless process were investigated to understand the origin of the sudden coercivity decrease below a certain grain size. The intrinsic coercivity is inversely proportional to ln D2 with the highest coercivity of 17 kOe at D˜4.5 μm, below which the coercivity drops as the grain size decreases. We found that the degradation of the coercivity of the magnet with a grain size of 3 μm was mainly caused by the inhomogeneous distribution of fcc-Nd oxide whose volume fraction increased with respect to the dhcp Nd-rich phase.

The status of Chinese permanent magnet industry and R&D activities

NASA Astrophysics Data System (ADS)

Dong, Shengzhi; Li, Wei; Chen, Hongsheng; Han, Rui

2017-05-01

It has been 15 years since China dominated the rare earth permanent magnet market in 2001. The annual output of sintered Nd-Fe-B magnets in China reached a new record of 126,300 tonnages in 2015 while the output in 2001 is only 6,500 tonnages. The average growth rate from 2001 to 2015 is about 23.5% though the output in 2012 suffers a deep drop due to the well known rare earth crisis in 2011. Currently, the RE magnet production capability in China seems to be over developed compared to actual requirements. Needless to say the oversupply situation implies a hard time for RE magnet manufacturers due to the fierce competition but maybe a good time for the whole industry. The motivation for a company to develop new technology and more competitive products with better performance and/or lower costs is greatly enhanced. The objective of this paper is to give a general picture of Chinese REPM industry and market including the output capability, the status of competition, the development of magnet application and the market trend. Some new research hot points potentially being applied, for example the Cerium magnet, will be introduced as well.

The effect of CuAl addition on the magnetic property, thermal stability and corrosion resistance of the sintered NdFeB magnets

NASA Astrophysics Data System (ADS)

Liu, Y. L.; Liang, J.; He, Y. Ch.; Li, Y. F.; Wang, G. F.; Ma, Q.; Liu, F.; Zhang, Y.; Zhang, X. F.

2018-05-01

To improve the coercivity of the Nd-Fe-B sintered magnets, the Cu29.8Al70.2 (at.%) powders with low melting point were introduced into the Nd-Fe-B magnets. The magnetic properties, microstructure, thermal stability and corrosion behavior of the sintered magnets with different amount of Cu29.8Al70.2 (0,0.25,0.50,0.75,1.0 wt.%) were investigated. When the amount of doped Cu29.8Al70.2 was less than 0.75 wt.%, the coercivity was improved, especially that of the magnets with 0.25 wt.% Cu29.8Al70.2, markedly increased to 13.97 kOe from 12.67 kOe (without CuAl). The improvement of magnetic properties could be attributed to enhanced wettability between Nd2Fe14B phase and Nd-rich phase and decreased exchange coupling between grains, which depended on the optimization of grain boundary microstructure and their distribution by codoping Cu and Al. With the addition of 0-1.0 wt.% Cu29.8Al70.2 powders, the reversible temperature coefficients of remanence and coercivity of the magnets could be also improved. The corrosion resistances was also found to be improved through small addition of Cu29.8Al70.2 powder in 3.5 wt.% NaCl solution by electrochemical and immersion tests, which could be due to the enhancement of the Nd-rich intergranular phase by addition Cu29.8Al70.2.

Perspectives for high-performance permanent magnets: applications, coercivity, and new materials

NASA Astrophysics Data System (ADS)

Hirosawa, Satoshi; Nishino, Masamichi; Miyashita, Seiji

2017-03-01

High-performance permanent magnets are indispensable in the production of high-efficiency motors and generators and ultimately for sustaining the green earth. The central issue of modern permanent magnetism is to realize high coercivity near and above room temperature on marginally hard magnetic materials without relying upon the critical elements such as heavy rare earths by means of nanostructure engineering. Recent investigations based on advanced nanostructure analysis and large-scale first principles calculations have led to significant paradigm shifts in the understandings of coercivity mechanism in Nd-Fe-B permanent magnets, which includes the discovery of the ferromagnetism of the thin (2 nm) intergranular phase surrounding the Nd2Fe14B grains, the occurrence of negative (in-plane) magnetocrystalline anisotropy of Nd ions and some Fe atoms at the interface which degrades coercivity, and visualization of the stochastic behaviors of magnetization in the magnetization reversal process at high temperatures. A major change may occur also in the motor topologies, which is currently overwhelmed by the magnetic flux weakening interior permanent magnet motor type, to other types with variable flux permanent magnet type in some applications to open up a niche for new permanent magnet materials. Keynote talk at 8th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN2016), 8-12 November 2016, Ha Long City, Vietnam.

Rare Earth Extraction from NdFeB Magnet Using a Closed-Loop Acid Process.

PubMed

Kitagawa, Jiro; Uemura, Ryohei

2017-08-14

There is considerable interest in extraction of rare earth elements from NdFeB magnets to enable recycling of these elements. In practical extraction methods using wet processes, the acid waste solution discharge is a problem that must be resolved to reduce the environmental impact of the process. Here, we present an encouraging demonstration of rare earth element extraction from a NdFeB magnet using a closed-loop hydrochloric acid (HCl)-based process. The extraction method is based on corrosion of the magnet in a pretreatment stage and a subsequent ionic liquid technique for Fe extraction from the HCl solution. The rare earth elements are then precipitated using oxalic acid. Triple extraction has been conducted and the recovery ratio of the rare earth elements from the solution is approximately 50% for each extraction process, as compared to almost 100% recovery when using a one-shot extraction process without the ionic liquid but with sufficient oxalic acid. Despite its reduced extraction efficiency, the proposed method with its small number of procedures at almost room temperature is still highly advantageous in terms of both cost and environmental friendliness. This study represents an initial step towards realization of a closed-loop acid process for recycling of rare earth elements.

Increased Efficiency of a Permanent Magnet Synchronous Generator through Optimization of NdFeB Magnet Arrays

NASA Astrophysics Data System (ADS)

Khazdozian, Helena; Hadimani, Ravi; Jiles, David

2014-03-01

The United States is currently dependent on fossil fuels for the majority of its energy needs, which has many negative consequences such as climate change. Wind turbines present a viable alternative, with the highest energy return on investment among even fossil fuel generation. Traditional commercial wind turbines use an induction generator for energy conversion. However, induction generators require a gearbox to increase the rotational speed of the drive shaft. These gearboxes increase the overall cost of the wind turbine and account for about 35 percent of reported wind turbine failures. Direct drive permanent magnet synchronous generators (PMSGs) offer an alternative to induction generators which eliminate the need for a gearbox. Yet, PMSGs can be more expensive than induction generators at large power output due to their size and weight. To increase the efficiency of PMSGs, the geometry and configuration of NdFeB permanent magnets were investigated using finite element techniques. The optimized design of the PMSG increases flux density and minimizes cogging torque with NdFeB permanent magnets of a reduced volume. These factors serve to increase the efficiency and reduce the overall cost of the PMSG. This work is supported by a National Science Foundation IGERT fellowship and the Barbara and James Palmer Endowment at the Department of Electrical and Computer Engineering of Iowa State University.

Low temperature diffusion process using rare earth-Cu eutectic alloys for hot-deformed Nd-Fe-B bulk magnets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akiya, T., E-mail: akiya.takahiro@nims.go.jp; Sepehri-Amin, H.; Ohkubo, T.

2014-05-07

The low temperature grain boundary diffusion process using RE{sub 70}Cu{sub 30} (RE = Pr, Nd) eutectic alloy powders was applied to sintered and hot-deformed Nd-Fe-B bulk magnets. Although only marginal coercivity increase was observed in sintered magnets, a substantial enhancement in coercivity was observed when the process was applied to hot-deformed anisotropic bulk magnets. Using Pr{sub 70}Cu{sub 30} eutectic alloy as a diffusion source, the coercivity was enhanced from 1.65 T to 2.56 T. The hot-deformed sample expanded along c-axis direction only after the diffusion process as RE rich intergranular layers parallel to the broad surface of the Nd{sub 2}Fe{sub 14}B are thickened inmore » the c-axis direction.« less

Magnetic properties and magnetization reversal mechanism of Nd-Fe-B nanoparticles synthesized by a sol-gel method

NASA Astrophysics Data System (ADS)

Rahimi, Hamed; Ghasemi, Ali; Mozaffarinia, Reza; Tavoosi, Majid

2017-12-01

Nd-Fe-B oxide powders with various pH were prepared using chloride and nitrate precursors including NdCl3·6H2O, FeCl3·6H2O, H3BO3, Nd2O3, Fe(NO3)3·9H2O, HNO3, citric acid (CA), ethylene glycol (EG) by Pechini type sol-gel method. The pH of chloride and nitrate base sols were 0 and 2.2, respectively. Mixed oxide powders were obtained by calcination and annealing the gels. These oxides by using a reduction-diffusion process under high vacuum and employing CaH2 as reducing agent at 800 °C were hated to prepare Nd2Fe14B nanoparticles. The role of pH on phase, morphologies, microstructure, and magnetic properties of the powders were investigated. The results show that with a decrease in pH, the average particle size and coercivity of Nd-Fe-B oxide powders were decreased and increased, respectively. Nd2Fe14B nanoparticles were formed successfully after reduction process. The average particle size of reduction treated products were 30 and 65 nm for powders which made of chloride and nitrate base metal salts, respectively. Final powders which made of chloride and nitrate base metal salts had a saturation magnetization of 127.7 emu/g and 122.8 emu/g while the coercivity of samples were 3.32 kOe and 1.82 kOe, respectively. The experimental results in the angular dependence of coercivity indicated that the normalized coercivity of the permanent magnets Hc(θ)/Hc(0) obeys the 1/cosθ law and intermediate between the 1/cosθ law and Stoner-Wohlfarth formula for different Nd2Fe14B magnets which made of nitrate and chloride base metal salts, respectively. Also, the results show that different Nd2Fe14B magnets which made of nitrate and chloride base metal salts had the maximum energy product of 5 and 16 MGOe, respectively. The Henkel plot showed that magnetic phases in synthesized NdFeB magnets which made of chloride and nitrate base metal salts were coupled by exchange and dipolar interactions, respectively. Different average particle size, morphology and microstructure were the reasons for variation of magnetic properties.

Towards understanding of magnetization reversal in Nd-Fe-B nanocomposites: analysis by high-throughput micromagnetic simulations

NASA Astrophysics Data System (ADS)

Erokhin, Sergey; Berkov, Dmitry; Ito, Masaaki; Kato, Akira; Yano, Masao; Michels, Andreas

2018-03-01

We demonstrate how micromagnetic simulations can be employed in order to characterize and analyze the magnetic microstructure of nanocomposites. For the example of nanocrystalline Nd-Fe-B, which is a potential material for future permanent-magnet applications, we have compared three different models for the micromagnetic analysis of this material class: (i) a description of the nanocomposite microstructure in terms of Stoner-Wohlfarth particles with and without the magnetodipolar interaction; (ii) a model based on the core-shell representation of the nanograins; (iii) the latter model including a contribution of superparamagnetic clusters. The relevant parameter spaces have been systematically scanned with the aim to establish which micromagnetic approach can most adequately describe experimental data for this material. According to our results, only the last, most sophisticated model is able to provide an excellent agreement with the measured hysteresis loop. The presented methodology is generally applicable to multiphase magnetic nanocomposites and it highligths the complex interrelationship between the microstructure, magnetic interactions, and the macroscopic magnetic properties.

Micromagnetic simulation of anisotropic grain boundary diffusion for sintered Nd-Fe-B magnets

NASA Astrophysics Data System (ADS)

Li, W.; Zhou, Q.; Zhao, L. Z.; Wang, Q. X.; Zhong, X. C.; Liu, Z. W.

2018-04-01

A systematic investigation on the anisotropic grain boundary diffusion in sintered Nd-Fe-B magnets is carried out by micromagnetic simulation. The results indicate that the critical reason for the anisotropic diffusion effect is not the difference in the amount of Dy diffused along different directions but the macroscopic demagnetizing field. The diffusion parallel to the easy axis from both pole surfaces of the magnet can increase the nucleation fields in the two major regions with large macroscopic demagnetizing fields, where the reverse domains can nucleate easily. As a consequence, the grain boundary diffusion along the directions parallel to the easy axis from two pole surfaces is more effective to improve the coercivity of the magnets than that along other directions. It is also found that, to enhance the coercivity, only a limited diffusion depth is required. The present result is in good agreement with the recent experimental findings.

Magnetic Properties Improvement of Die-upset Nd-Fe-B Magnets by Dy-Cu Press Injection and Subsequent Heat Treatment

NASA Astrophysics Data System (ADS)

Wang, Zexuan; Ju, Jinyun; Wang, Jinzhi; Yin, Wenzong; Chen, Renjie; Li, Ming; Jin, Chaoxiang; Tang, Xu; Lee, Don; Yan, Aru

2016-12-01

Ultrafine-grained die-upset Nd-Fe-B magnets are of importance because they provide a wide researching space to redesign the textured structures. Here is presented a route to obtain a new die-upset magnet with substantially improved magnetic properties. After experiencing the optimized heat treatment, both the coercivity and remanent magnetization of the Dy-Cu press injected magnets increased substantially in comparison with those of the annealed reference magnets, which is distinct from the reported experimental results on heavy rare-earth diffusion. To study the mechanism, we analyzed the texture evolution in high-temperature annealed die-upset magnets, which had significant impact on the improvement of remanent magnetization. On basis of the results, we find that the new structures are strongly interlinked with the initial structures. With injecting Dy-Cu eutectic alloy, an optimized initial microstructure was achieved in the near-surface diffused regions, which made preparations for the subsequent texture improvement. Besides, the Dy gradient distribution of near-surface regions of the Dy-Cu press injected magnets was also investigated. By controlling the initial microstructure and subsequent diffusion process, a higher performance magnet is expected to be obtained.

Influence of Segmentation of Ring-Shaped NdFeB Magnets with Parallel Magnetization on Cylindrical Actuators

PubMed Central

Eckert, Paulo Roberto; Goltz, Evandro Claiton; Filho, Aly Ferreira Flores

2014-01-01

This work analyses the effects of segmentation followed by parallel magnetization of ring-shaped NdFeB permanent magnets used in slotless cylindrical linear actuators. The main purpose of the work is to evaluate the effects of that segmentation on the performance of the actuator and to present a general overview of the influence of parallel magnetization by varying the number of segments and comparing the results with ideal radially magnetized rings. The analysis is first performed by modelling mathematically the radial and circumferential components of magnetization for both radial and parallel magnetizations, followed by an analysis carried out by means of the 3D finite element method. Results obtained from the models are validated by measuring radial and tangential components of magnetic flux distribution in the air gap on a prototype which employs magnet rings with eight segments each with parallel magnetization. The axial force produced by the actuator was also measured and compared with the results obtained from numerical models. Although this analysis focused on a specific topology of cylindrical actuator, the observed effects on the topology could be extended to others in which surface-mounted permanent magnets are employed, including rotating electrical machines. PMID:25051032

Influence of segmentation of ring-shaped NdFeB magnets with parallel magnetization on cylindrical actuators.

PubMed

Eckert, Paulo Roberto; Goltz, Evandro Claiton; Flores Filho, Aly Ferreira

2014-07-21

This work analyses the effects of segmentation followed by parallel magnetization of ring-shaped NdFeB permanent magnets used in slotless cylindrical linear actuators. The main purpose of the work is to evaluate the effects of that segmentation on the performance of the actuator and to present a general overview of the influence of parallel magnetization by varying the number of segments and comparing the results with ideal radially magnetized rings. The analysis is first performed by modelling mathematically the radial and circumferential components of magnetization for both radial and parallel magnetizations, followed by an analysis carried out by means of the 3D finite element method. Results obtained from the models are validated by measuring radial and tangential components of magnetic flux distribution in the air gap on a prototype which employs magnet rings with eight segments each with parallel magnetization. The axial force produced by the actuator was also measured and compared with the results obtained from numerical models. Although this analysis focused on a specific topology of cylindrical actuator, the observed effects on the topology could be extended to others in which surface-mounted permanent magnets are employed, including rotating electrical machines.

Magnetic Properties Improvement of Die-upset Nd-Fe-B Magnets by Dy-Cu Press Injection and Subsequent Heat Treatment

PubMed Central

Wang, Zexuan; Ju, Jinyun; Wang, Jinzhi; Yin, Wenzong; Chen, Renjie; Li, Ming; Jin, Chaoxiang; Tang, Xu; Lee, Don; Yan, Aru

2016-01-01

Ultrafine-grained die-upset Nd-Fe-B magnets are of importance because they provide a wide researching space to redesign the textured structures. Here is presented a route to obtain a new die-upset magnet with substantially improved magnetic properties. After experiencing the optimized heat treatment, both the coercivity and remanent magnetization of the Dy-Cu press injected magnets increased substantially in comparison with those of the annealed reference magnets, which is distinct from the reported experimental results on heavy rare-earth diffusion. To study the mechanism, we analyzed the texture evolution in high-temperature annealed die-upset magnets, which had significant impact on the improvement of remanent magnetization. On basis of the results, we find that the new structures are strongly interlinked with the initial structures. With injecting Dy-Cu eutectic alloy, an optimized initial microstructure was achieved in the near-surface diffused regions, which made preparations for the subsequent texture improvement. Besides, the Dy gradient distribution of near-surface regions of the Dy-Cu press injected magnets was also investigated. By controlling the initial microstructure and subsequent diffusion process, a higher performance magnet is expected to be obtained. PMID:27922060

Coercivity enhancement of Dy-coated Nd-Fe-B flakes by crystallization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fukunaga, H.; Sugimoto, Y.; Nakano, M.

2011-04-01

The coercivity of isotropic Dy-coated Nd-Fe-B flakes was enhanced by crystallization and simultaneous diffusion of Dy from their surfaces. Amorphous Dy-coated Nd-Fe-B flakes were crystallized by heating them to 923 K 2over a 2 min period followed by rapid cooling. During crystallization, the Dy on the surface diffused into the flakes. This low-temperature rapid annealing produced flakes with fine grains and the Dy diffusion enhanced their coercivity. The coercivity after crystallization increased with increasing Dy layer thickness, although the remanence decreased when the layer thickness exceeded 3 {mu}m. Thick coatings of over 6 {mu}m resulted in the formation of DyFe{submore » 2}, which degraded the magnetic properties of the crystallized flakes. Flakes with a 3-{mu}m-thick coating exhibited excellent magnetic properties after annealing: They had a coercivity of 1880 kA/m and a remanence of 78 emu/g. This coercivity is approximately 500 kA/m higher than that of uncoated flakes, whereas the remanence is comparable to that of uncoated flakes.« less

Effect of annealing conditions on the microstructure and magnetic properties of sintered Nd-Fe-B magnets as seen by magnetic small-angle neutron scattering

NASA Astrophysics Data System (ADS)

Périgo, Élio A.; Titov, Ivan; Weber, Raoul; Mettus, Denis; Peral, Inma; Vallcorba, Oriol; Honecker, Dirk; Feoktystov, Artem; Michels, Andreas

2018-03-01

We have investigated the effect of the annealing conditions (heating rate and temperature) on the magnetic microstructure of sintered Nd-Fe-B magnets by means of magnetometry, scanning electron microscopy, high-energy synchrotron x-ray diffraction, and small-angle neutron scattering (SANS). While the temperature treatment has a strong effect on the coercivity (reduction by about 50% on annealing), the associated changes in the microstructure do surprisingly not show up (or at best only very weakly) in the neutron-scattering signal, which probes a mesoscopic real-space length scale ranging between about 1–300 nm. On the other hand, the x-ray data reveal microstructural changes in the Nd-rich phases, presumably due to modifications in grain-boundary regions. Moreover, we observe an unusual diamond-shaped angular anisotropy in the SANS cross section, which strongly points towards the existence of texture in the nuclear microstructure.

Effect of oxygen content of Nd-Fe-B sintered magnet on grain boundary diffusion process of DyH2 dip-coating

NASA Astrophysics Data System (ADS)

Bae, Kyoung-Hoon; Lee, Seong-Rae; Kim, Hyo-Jun; Lee, Min-Woo; Jang, Tae-Suk

2015-11-01

We investigated the effect of oxygen content on the microstructural and magnetic properties of a DyH2 dip-coated Nd-Fe-B sintered magnet. When the magnet had a low oxygen content (1500 ppm), the volume and size of the rare-earth-rich oxide (Nd-Dy-O) phase was reduced, and a uniform and continuous thin Nd-rich grain boundary phase (GBP) was well developed. The grain boundary diffusion depth of Dy increased from 200 to 350 μm with decreasing oxygen content from ˜3000 to 1500 ppm. The coercivity of the low-oxygen magnet increased from 19.98 to 23.59 kOe after grain boundary diffusion process (GBDP) while the remanence reduction was minimized. The formation of an fcc-NdOx Nd-rich phase in the high-oxygen magnet hindered the formation of a Nd-rich triple-junction phase and GBP. In contrast, a metallic dhcp-Nd phase, which was closely related to coercivity enhancement after GBDP, was formed in the low-oxygen magnet.

Characterisation of the aqueous corrosion process in NdFeB melt spun ribbon and MQI bonded magnets

NASA Astrophysics Data System (ADS)

McCain, Stephen

A major factor limiting the use and longevity of rare earth based magnetic materials is their susceptibility to aqueous corrosion and associated detrimental effects upon the magnetic properties of the material. This process was investigated through a combination of exposure to simulated environmental conditions and hydrogen absorption/desorption studies (HADS) in conjunction with magnetic characterisation. This study utilises NdFeB MQP-B melt-spun ribbon manufactured by Magnequench, in the form of MQI bonded magnets and also in its unbonded state as MQ powder. Specifically, it was concerned with how effective a variety of bonding media (epoxy resin,PTFE, zinc) and surface coatings (PTFE, Qsil, zinc LPPS, Dex-Cool) were at limiting the impact of aqueous corrosion in MQI bonded magnets. To characterise the effect of hydrogen absorption upon the magnetic properties of the MQP-B, hydrogen uptake was induced followed by a series of outgassing heat treatments with subsequent magnetic characterisation accompanied by HADS techniques performed after each outgas. This allowed comparisons to be made between the effects of aqueous corrosion process and hydrogen absorption upon the magnetic properties of the alloy.. This study has clearly demonstrated the link between the abundance of environmental moisture and rate of Hci losses in MQI bonded magnets. In addition to this the key mechanism responsible for the degradation of magnetic properties has been identified. These losses have been attributed to the absorption of hydrogen generated by the dissociation of water in the presence of NdFeB during the aqueous corrosion process. It has been shown that the use of a bonding media that is impermeable to water can limit the effects of aqueous corrosion by limiting water access to the Magnequench particles (MQP) and also the positive effects of the use of suitable surface coatings has been shown to be effective for the same reason..

High coercivity, anisotropic, heavy rare earth-free Nd-Fe-B by Flash Spark Plasma Sintering.

PubMed

Castle, Elinor; Sheridan, Richard; Zhou, Wei; Grasso, Salvatore; Walton, Allan; Reece, Michael J

2017-09-11

In the drive to reduce the critical Heavy Rare Earth (HRE) content of magnets for green technologies, HRE-free Nd-Fe-B has become an attractive option. HRE is added to Nd-Fe-B to enhance the high temperature performance of the magnets. To produce similar high temperature properties without HRE, a crystallographically textured nanoscale grain structure is ideal; and this conventionally requires expensive "die upset" processing routes. Here, a Flash Spark Plasma Sintering (FSPS) process has been applied to a Dy-free Nd 30.0 Fe 61.8 Co 5.8 Ga 0.6 Al 0.1 B 0.9 melt spun powder (MQU-F, neo Magnequench). Rapid sinter-forging of a green compact to near theoretical density was achieved during the 10 s process, and therefore represents a quick and efficient means of producing die-upset Nd-Fe-B material. The microstructure of the FSPS samples was investigated by SEM and TEM imaging, and the observations were used to guide the optimisation of the process. The most optimal sample is compared directly to commercially die-upset forged (MQIII-F) material made from the same MQU-F powder. It is shown that the grain size of the FSPS material is halved in comparison to the MQIII-F material, leading to a 14% increase in coercivity (1438 kA m -1 ) and matched remanence (1.16 T) giving a BH max of 230 kJ m -3 .

Correlative multi-scale characterization of a fine grained Nd-Fe-B sintered magnet.

PubMed

Sasaki, T T; Ohkubo, T; Hono, K; Une, Y; Sagawa, M

2013-09-01

The Nd-rich phases in pressless processed fine grained Nd-Fe-B sintered magnets have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and three dimensional atom probe tomography (3DAP). The combination of the backscattered electron (BSE) and in-lens secondary electron (IL-SE) images in SEM led to an unambiguous identification of four types of Nd-rich phases, NdOx, Ia3 type phase, which is isostructural to Nd₂O₃, dhcp-Nd and Nd₁Fe₄B₄. In addition, the 3DAP analysis of thin Nd-rich grain boundary layer indicate that the coercivity has a close correlation with the chemistry of the grain boundary phase. Copyright © 2013 Elsevier B.V. All rights reserved.

A Double-Decker Levitation Experiment Using a Sandwich of Superconductors.

ERIC Educational Resources Information Center

Jacob, Anthony T.; And Others

1988-01-01

Shows that the mutual repulsion that enables a superconductor to levitate a magnet and a magnet to levitate a superconductor can be combined into a single demonstration. Uses an overhead projector, two pellets of "1-2-3" superconductor, Nd-Fe-B magnets, liquid nitrogen, and paraffin. Offers superconductor preparation, hazards, and disposal…

Frequency adjustable MEMS vibration energy harvester

NASA Astrophysics Data System (ADS)

Podder, P.; Constantinou, P.; Amann, A.; Roy, S.

2016-10-01

Ambient mechanical vibrations offer an attractive solution for powering the wireless sensor nodes of the emerging “Internet-of-Things”. However, the wide-ranging variability of the ambient vibration frequencies pose a significant challenge to the efficient transduction of vibration into usable electrical energy. This work reports the development of a MEMS electromagnetic vibration energy harvester where the resonance frequency of the oscillator can be adjusted or tuned to adapt to the ambient vibrational frequency. Micro-fabricated silicon spring and double layer planar micro-coils along with sintered NdFeB micro-magnets are used to construct the electromagnetic transduction mechanism. Furthermore, another NdFeB magnet is adjustably assembled to induce variable magnetic interaction with the transducing magnet, leading to significant change in the spring stiffness and resonance frequency. Finite element analysis and numerical simulations exhibit substantial frequency tuning range (25% of natural resonance frequency) by appropriate adjustment of the repulsive magnetic interaction between the tuning and transducing magnet pair. This demonstrated method of frequency adjustment or tuning have potential applications in other MEMS vibration energy harvesters and micromechanical oscillators.

Effect of deformation ratios on grain alignment and magnetic properties of hot pressing/hot deformation Nd-Fe-B magnets

NASA Astrophysics Data System (ADS)

Guo, Zhaohui; Li, Mengyu; Wang, Junming; Jing, Zheng; Yue, Ming; Zhu, Minggang; Li, Wei

2018-05-01

The magnetic properties, microstructure and orientation degrees of hot pressing magnet and hot deformation Nd-Fe-B magnets with different deformation ratios have been investigated in this paper. The remanence (Br) and maximum magnetic energy product ((BH)max) were enhanced gradually with the deformation ratio increasing from 0% to 70%, whereas the coercivity (HCj) decreased. The scanning electron microscopy (SEM) images of fractured surfaces parallel to the pressure direction during hot deformation show that the grains tend to extend perpendicularly to the c-axes of Nd2Fe14B grains under the pressure, and the aspect ratios of the grains increase with the increase of deformation ratio. Besides, the compression stress induces the long axis of grains to rotate and the angle (θ) between c-axis and pressure direction decreases. The X-ray diffraction (XRD) patterns reveal that orientation degree improves with the increase of deformation ratio, agreeing well with the SEM results. The hot deformation magnet with a deformation ratio of 70% has the best Br and (BH)max, and the magnetic properties are as followed: Br=1.40 T, HCj=10.73 kOe, (BH)max=42.30 MGOe.

The Rare Earth Magnet Industry and Rare Earth Price in China

NASA Astrophysics Data System (ADS)

Ding, Kaihong

2014-07-01

In the past four years, the price of rare earth metal fluctuates sharply for many reasons. Currently, it has become more stable and more reasonable. This presentation is focused on the effect about the rare earth metal price. Some motor manufacturers have shifted from rare earth permanent magnet to ferrite magnet. Many motor manufacturers changed the design for the motor cooling system to make the motor function at a lower temperature. Thus the consumption of Dy can be markedly reduced. As for manufacturer of NdFeB magnet, we are also trying to optimize our process to reduce to dependence of HREE such as Dy and Tb. HS process have been introduced to solve the problem. With more and more people focusing and engaging on the REE industry, the price of REE will be more transparent without too many fluctuations. China is considering the problems of balancing the environment, energy sources, and labor sources. The application field about NdFeB such as wind turbine generator, HEV/EV, FA /OA is flourishing.

Improved thermal stability of TbF3-coated sintered Nd-Fe-B magnets by electrophoretic deposition

NASA Astrophysics Data System (ADS)

Cao, X. J.; Chen, L.; Guo, S.; Di, J. H.; Ding, G. F.; Chen, R. J.; Yan, A. R.; Chen, K. Z.

2018-05-01

Using electrophoretic deposition (EPD) method, the impact of TbF3 diffusion on the coercivity, microstructure and thermal stability of sintered Nd-Fe-B magnets with different rare earth (RE) content was investigated. In the diffused magnets with the RE content of 34 wt.%, the maximum coercivity about 28.12 kOe with less than 1.44 wt.% Tb was achieved, the coercivity temperature coefficient (β) was improved to -0.50 %/°C from -0.58 %/°C within the temperature interval 25-160 °C, and the maximum operating temperature further increased to about 160 °C. It suggested that TbF3 diffused magnets had much superior thermal stability than the annealed samples. This was attributed to the formation of the Tb-rich (Nd, Tb)2Fe14B phase in the outer region of the matrix grains and the improved Nd-rich grain boundary phase after TbF3 diffusion.

Coercivity enhancement of Nd-Fe-B hot-deformed magnets by the eutectic grain boundary diffusion process using Nd-Ga-Cu and Nd-Fe-Ga-Cu alloys

NASA Astrophysics Data System (ADS)

Liu, Lihua; Sepehri-Amin, H.; Sasaki, T. T.; Ohkubo, T.; Yano, M.; Sakuma, N.; Kato, A.; Shoji, T.; Hono, K.

2018-05-01

Nd80Ga15Cu5 and Nd62Fe14Ga20Cu4 alloys were used as diffusion sources for the eutectic grain boundary diffusion process, applying to 4 mm-thick Nd-Fe-B hot-deformed magnets. Both samples showed nearly same coercivity of 2.2 T, while the sample processed with Nd62Fe14Ga20Cu4 showed smaller remanence deterioration from 1.50 T to 1.30 T, in contrast to that of the sample processed with Nd80Ga15Cu5 to 1.08 T. Mr/Ms of the initial sample and the samples processed with Nd62Fe14Ga20Cu4 and Nd80Ga15Cu5 were 0.946, 0.934 and 0.917, respectively, suggesting that the sample processed with Nd62Fe14Ga20Cu4 retains stronger c-axis texture after the diffusion process. Nd-rich phases with Ia3 ¯ and fcc structures were observed in the sample processed with Nd80Ga15Cu5, while the Nd-rich phases with the Ia3 ¯ and hcp structures were found in the sample processed with Nd62Fe14Ga20Cu4, all of which are the phases commonly observed in Nd-Fe-B sintered magnets.

The corrosion mechanism of the sintered (Ce, Nd)-Fe-B magnets prepared by double main phase and single main phase approaches

NASA Astrophysics Data System (ADS)

Shi, Xiaoning; Zhu, Minggang; Zhou, Dong; Song, Liwei; Guo, Zhaohui; Li, Jia; Li, Wei

2018-05-01

The sintered (Ce, Nd)-Fe-B magnets were produced widely by Double Main Phase (DMP) method in China as the magnetic properties of the DMP magnets are superior to those of single main phase (SMP) magnets with the same nominal composition. In this work, the microstructure and corrosion mechanism of the sintered (Ce0.2Nd0.8)30FebalB (wt.%) magnets prepared by DMP and SMP method were studied in detail. Compared to SMP magnets, the DMP magnets have more positive corrosion potential, lower corrosion current density, larger electron transfer resistance, and lower mass loss of the free corrosion experiment in 0.5mol/l Na2SO4 aqueous solution. All of the results show that the DMP magnets have better corrosion resistance than SMP magnets. The back scattered electron images show that the crystalline grains of the DMP magnets are sphericity with a smooth surface while the SMP ones have plenty of edges and corners. Besides, the distribution of Ce/Nd is much more uneven in both magnetic phase and rare earth (Re)-rich phase of the DMP magnets than those of SMP magnets. After corrosion, DMP magnets show eroded magnetic phase and intact Re-rich phase, which indicate that galvanic corrosion of the Re-rich phase acting as the cathode appears.

Degradation phenomena of magnetic attachments used clinically in the oral environment

NASA Astrophysics Data System (ADS)

Chung, Chae-Heon; Choe, Han-Cheol; Kwak, Jong-Ha

2006-08-01

The purpose of this study was to investigate the mechanisms involved in the failure of magnetic attachments used to retain dental prostheses. Dyna magnets were retrieved from dentures that had failed after 34 months of clinical use. These magnetic attachments were prepared and sectioned so as to observe the corrosion surface and layer in order to analyze the corrosion behaviors of the attachments. The corroded surface was observed under a field emission scanning electron microscope (FE-SEM) (JSM 840A, JEOL, Japan). An X-ray diffractometer (XRD) was used to analyze the corrosion product formed due to corrosion in the oral environment. Erosion-corrosion started in the uneven portion of the stainless steel cover in the magnetic attachments composed with Nd-Fe-B alloy. Corrosion was initiated on the worn stainless steel surface, followed by spalling of magnetic material due to corrosive solution. The corrosion rate increased drastically after the corrosion product caused spalling in Nd-Fe-B alloy. Corrosion initiated in the uneven stainless steel surface as well as in the welded zone. In conclusion, the failure of magnetic attachments may occur by either welding failure or breakdown of the encapsulating material. Thus, we believe that treating the surface of magnetic attachments would resolve the corrosion problem seen in magnetic attachments to some extent.

Self-vibration cancellation of a novel bi-directional magnetized NdFeB/magnetostrictive/piezoelectric laminate

NASA Astrophysics Data System (ADS)

Leung, Chung Ming; Wang, Feifei; Wang, Ya

2016-06-01

A novel magnetoelectric (ME) laminated composite structure is proposed in this work, aiming to provide a good self-vibration cancellation performance under the magnetic field detection environment. The proposed structure consists of two Terfenol-D magnetostrictive alloy plates which are revised and length-magnetized by two NdFeB magnets bonded on the top surface of a thickness-polarized Pb(Zr, Ti)O3 (PZT) ceramic plate with separate electrodes. Experiments have shown that great vibration suppression up to 44 dB under harmonic disturbance was observed. The ME coefficient of the proposed structure also reaches up to ˜29 mV/Oe at non-resonance frequency and 758 mV/Oe at resonance frequency of 79 kHz which is ˜2 times larger than the traditional L-T Terfenol-D/PZT bilayer configuration of the same scale. Such performance improvement is achieved based on the bi-directional magnetic field bias (HBias) of two NdFeB magnets in magnetostrictive layer, internal in-series electrical wire connection in piezoelectric layer. The proposed design has great potential to be used for industrial applications associated with heavy environmental vibration noise.

Solid-solution stability and preferential site-occupancy in (R-R′){sub 2}Fe{sub 14}B compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Colin, C. V.; Dempsey, N. M.; Univ. Grenoble Alpes, Inst NEEL, F-38000 Grenoble

The rare-earth (R) uniaxial anisotropy of R{sub 2}Fe{sub 14}B compounds with magnetic R atoms (e.g., Nd or Pr) is at the origin of the exceptional hard magnetic properties achieved in magnets based on these compounds. The uniaxial anisotropy found in Ce{sub 2}Fe{sub 14}B is attributed mainly to the magnetism of Fe. Ce is the most abundant R element and there has been much recent effort to fabricate magnets in which Ce is partially substituted for Nd. In the present neutron study of (R{sub 1−x}Ce{sub x}){sub 2}Fe{sub 14}B (R = La or Nd), Ce is found to enter the R{sub 2}Fe{submore » 14}B phase over the entire composition range. The crystallographic parameters decrease with increasing Ce content and the Ce atoms preferentially occupy the smaller 4f sites. It is concluded that Ce in these (RR′){sub 2}Fe{sub 14}B compounds essentially maintains the intermediate valence character found in Ce{sub 2}Fe{sub 14}B. It is proposed that, in this intermediate valence state, Ce weakly contributes to uniaxial anisotropy, thus making a link with the fact that significant coercivity is preserved in Ce-substituted NdFeB magnets.« less

3D print of polymer bonded rare-earth magnets, and 3D magnetic field scanning with an end-user 3D printer

NASA Astrophysics Data System (ADS)

Huber, C.; Abert, C.; Bruckner, F.; Groenefeld, M.; Muthsam, O.; Schuschnigg, S.; Sirak, K.; Thanhoffer, R.; Teliban, I.; Vogler, C.; Windl, R.; Suess, D.

2016-10-01

3D print is a recently developed technique, for single-unit production, and for structures that have been impossible to build previously. The current work presents a method to 3D print polymer bonded isotropic hard magnets with a low-cost, end-user 3D printer. Commercially available isotropic NdFeB powder inside a PA11 matrix is characterized, and prepared for the printing process. An example of a printed magnet with a complex shape that was designed to generate a specific stray field is presented, and compared with finite element simulation solving the macroscopic Maxwell equations. For magnetic characterization, and comparing 3D printed structures with injection molded parts, hysteresis measurements are performed. To measure the stray field outside the magnet, the printer is upgraded to a 3D magnetic flux density measurement system. To skip an elaborate adjusting of the sensor, a simulation is used to calibrate the angles, sensitivity, and the offset of the sensor. With this setup, a measurement resolution of 0.05 mm along the z-axes is achievable. The effectiveness of our calibration method is shown. With our setup, we are able to print polymer bonded magnetic systems with the freedom of having a specific complex shape with locally tailored magnetic properties. The 3D scanning setup is easy to mount, and with our calibration method we are able to get accurate measuring results of the stray field.

Influence of radius of cylinder HTS bulk on guidance force in a maglev vehicle system

NASA Astrophysics Data System (ADS)

Longcai, Zhang

2014-07-01

Bulk superconductors had great potential for various engineering applications, especially in a high-temperature superconducting (HTS) maglev vehicle system. In such a system, the HTS bulks were always exposed to AC external magnetic field, which was generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, it was observed that the guidance force of the YBCO bulk over the NdFeB guideway used in the HTS maglev vehicle system was decayed by the application of the AC external magnetic field. In this paper, we investigated the influence of the radius of the cylinder HTS bulk exposed to an AC magnetic field perturbation on the guidance force in the maglev vehicle system. From the results, it was found that the guidance force was stronger for the bulk with bigger radius and the guidance force decay rates of the bulks were approximately equal despite of the different radius in the maglev vehicle system. Therefore, in order to obtain higher guidance force in the maglev vehicle system, we could use the cylinder HTS bulks with the bigger radius.

De Magnete et Meteorite: Cosmically Motivated Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewis, LH; Pinkerton, FE; Bordeaux, N

2014-01-01

Meteorites, likely the oldest source of magnetic material known to mankind, are attracting renewed interest in the science and engineering community. Worldwide focus is on tetrataenite, a uniaxial ferromagnetic compound with the tetragonal L1(0) crystal structure comprised of nominally equiatomic Fe-Ni that is found naturally in meteorites subjected to extraordinarily slow cooling rates, as low as 0.3 K per million years. Here, the favorable permanent magnetic properties of bulk tetrataenite derived from the meteorite NWA 6259 are quantified. The measured magnetization approaches that of Nd-Fe-B (1.42 T) and is coupled with substantial anisotropy (1.0-1.3 MJ/m(3)) that implies the prospect formore » realization of technologically useful coercivity. A highly robust temperature dependence of the technical magnetic properties at an elevated temperature (20-200 degrees C) is confirmed, with a measured temperature coefficient of coercivity of -0.005%/ K, over one hundred times smaller than that of Nd-Fe-B in the same temperature range. These results quantify the extrinsic magnetic behavior of chemically ordered tetrataenite and are technologically and industrially significant in the current context of global supply chain limitations of rare-earth metals required for present-day high-performance permanent magnets that enable operation of a myriad of advanced devices and machines.« less

The temperature dependence of magnetic anisotropy of Nd-Fe-B thin films

NASA Astrophysics Data System (ADS)

Sato, Takuya; Hashimoto, Ryuji; Tanaka, Yoshitomo; Suzuki, Kenichi; Enokido, Yasushi; Choi, Kyung-Ku; Suzuki, Takao

2018-05-01

The magnetic properties of Nd-Fe-B thin films with the three different compositions (#1: Nd12.6Fe81.5B5.9, #2: Nd14.6Fe78.1B7.4 and #3: Nd22.6Fe66.2B11.2) are discussed. With increasing Nd content, the c-axis orientation along the film normal is enhanced. It is found that sample #2 possesses the saturation magnetization Ms very close to that for Nd2Fe14B over a temperature range from 100 to about 300K. The magnetic anisotropy constant Ku2 for sample #2 is the highest among those samples, but smaller by about 20%, as compared to that for Nd2Fe14B. It is of interest to note that the temperature TR at which Ku1 changes its sign is lower by about 30K as compared to that previously reported for Nd2Fe14B. The reason for this discrepancy is not clear, but could be due to the presence of the minority phases of Nd-rich compounds and also a possible contribution of the magneto-elastic effect to the net magnetic anisotropy.

Electromagnetic braking revisited with a magnetic point dipole model

NASA Astrophysics Data System (ADS)

Land, Sara; McGuire, Patrick; Bumb, Nikhil; Mann, Brian P.; Yellen, Benjamin B.

2016-04-01

A theoretical model is developed to predict the trajectory of magnetized spheres falling through a copper pipe. The derive magnetic point dipole model agrees well with the experimental trajectories for NdFeB spherical magnets of varying diameter, which are embedded inside 3D printed shells with fixed outer dimensions. This demonstration of electrodynamic phenomena and Lenz's law serves as a good laboratory exercise for physics, electromagnetics, and dynamics classes at the undergraduate level.

Tunable biasing magnetic field design of ferrite tuner for ICRF heating system in EAST

NASA Astrophysics Data System (ADS)

Manman, XU; Yuntao, SONG; Gen, CHEN; Yanping, ZHAO; Yuzhou, MAO; Guang, LIU; Zhen, PENG

2017-11-01

Ion cyclotron range of frequency (ICRF) heating has been used in tokamaks as one of the most successful auxiliary heating tools and has been adopted in the EAST. However, the antenna load will fluctuate with the change of plasma parameters in the ICRF heating process. To ensure the steady operation of the ICRF heating system in the EAST, fast ferrite tuner (FFT) has been carried out to achieve real-time impedance matching. For the requirements of the FFT impedance matching system, the magnet system of the ferrite tuner (FT) was designed by numerical simulations and experimental analysis, where the biasing magnetic circuit and alternating magnetic circuit were the key researched parts of the ferrite magnet. The integral design goal of the FT magnetic circuit is that DC bias magnetic field is 2000 Gs and alternating magnetic field is ±400 Gs. In the FTT, E-type magnetic circuit was adopted. Ferrite material is NdFeB with a thickness of 30 mm by setting the working point of NdFeB, and the ampere turn of excitation coil is 25 through the theoretical calculation and simulation analysis. The coil inductance to generate alternating magnetic field is about 7 mH. Eddy-current effect has been analyzed, while the magnetic field distribution has been measured by a Hall probe in the medium plane of the biasing magnet. Finally, the test results show the good performance of the biasing magnet satisfying the design and operating requirements of the FFT.

Achievement of high coercivity in sintered R-Fe-B magnets based on misch-metal by dual alloy method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niu, E, E-mail: niue@aphy.iphy.ac.cn; Wang, Zhen-Xi; Beijing Zhong Ke San Huan Research, No.10 Chuangxin Road, Changping District, Beijing 102200

2014-03-21

The R-Fe-B (R, rare earth) sintered magnets prepared with different ratio of alloys of MM-Fe-B (MM, misch-metal) and Nd-Fe-B by dual alloy method were investigated. As expected, the high ratio of MM-Fe-B alloy degrades the hard magnetic properties heavily with intrinsic coercivity lower than 5 kOe. When the atomic ratio MM/R ≤ 21.5% the magnetic properties can reach a practical level of B{sub r} ≥ 12.1 kGs, H{sub cj} ≥ 10.7 kOe, and (BH){sub max} ≥ 34.0 MGOe. And the effect of H{sub cj} enhancement by the grain boundary diffusion process is obvious when MM/R ≤ 21.5%. It is revealed that the decrement of intrinsic magnetic properties of R{sub 2}Fe{submore » 14}B matrix phase is not the main reason of the degradation of the magnets with high MM ratio. The change of deteriorated microstructure together with phase component plays fundamental roles in low H{sub cj}. In high MM ratio magnets, (a) after annealing, Ce atoms inside main phase are inclined to be segregated in the outer layer of the main phase grains; (b) there is no thin layer of Ce-rich phase as an analogue of Nd-rich phase to separate main phase grains; (c) excessive Ce tends to form CeFe{sub 2} grains.« less

Permanent magnet design methodology

NASA Technical Reports Server (NTRS)

Leupold, Herbert A.

1991-01-01

Design techniques developed for the exploitation of high energy magnetically rigid materials such as Sm-Co and Nd-Fe-B have resulted in a revolution in kind rather than in degree in the design of a variety of electron guidance structures for ballistic and aerospace applications. Salient examples are listed. Several prototype models were developed. These structures are discussed in some detail: permanent magnet solenoids, transverse field sources, periodic structures, and very high field structures.

[Studies on reduction of repellent force of rare earth magnets--concerning tooth intrusion].

PubMed

Kitsugi, A

1992-12-01

The purpose of this investigation was to evaluate the sealing effect of the repelling force of the magnets with ferromagnetic stainless steel and also to examine the reduction pattern along with the change of the relative position of the magnets. The Nd-Fe-B magnet as rare earth magnet, and SUSXM 27, YEP-3, SUS 416 as ferromagnetic stainless steel were used in this experiment. The findings were as follows: 1. There was a little decrease of the repelling force of the magnets sealed with ferromagnetic stainless steel. On the other hand, no significant differences in the repelling force sealed with any kind of ferromagnetic stainless steel were found. 2. Direct contact of the repelling force of the phi 4.0 x 1.5 mm magnets sealed with SUSXM 27 of 0.2 mm in thickness was 242 gf. According to relative horizontal 1.2 mm movement keeping direct contact, the vertical and horizontal components of the repelling force were of the same value. 3. The repelling force of the phi 10.0 x 1.8 mm magnets sealed with SUSXM 27 of 0.2 mm in thickness was 815 gf. It showed more than 300 gf of vertical component of the repelling force when the magnets shifted to 3.0 mm horizontally when in contact. 4. It is suggested that the repelling force of the Nd-Fe-B magnets will be clinically useful for the intrusion of molar teeth.

High electrical resistivity Nd-Fe-B die-upset magnet doped with eutectic DyF3-LiF salt mixture

NASA Astrophysics Data System (ADS)

Kim, K. M.; Kim, J. Y.; Kwon, H. W.; Kim, D. H.; Lee, J. G.; Yu, J. H.

2017-05-01

Nd-Fe-B-type die-upset magnet with high electrical resistivity was prepared by doping of eutectic DyF3-LiF salt mixture. Mixture of melt-spun Nd-Fe-B flakes (MQU-F: Nd13.6Fe73.6Co6.6Ga0.6B5.6) and eutectic binary (DyF3-LiF) salt (25 mol% DyF3 - 75 mol% LiF) was hot-pressed and then die-upset. By adding the eutectic salt mixture (> 4 wt%), electrical resistivity of the die-upset magnet was enhanced to over 400 μ Ω .cm compared to 190 μ Ω .cm of the un-doped magnet. Remarkable enhancement of the electrical resistivity was attributed to homogeneous and continuous coverage of the interface between flakes by the easily melted eutectic salt dielectric mixture. It was revealed that active substitution of the Nd atoms in neighboring flakes by the Dy atoms from the added (DyF3-LiF) salt mixture had occurred during such a quick thermal processing of hot-pressing and die-upsetting. This Dy substitution led to coercivity enhancement in the die-upset magnet doped with the eutectic (DyF3-LiF) salt mixture. Coercivity and remanence of the die-upset magnet doped with (DyF3-LiF) salt mixture was as good as those of the DyF3-doped magnet.

Angular dependence of coercivity derived from alignment dependence of coercivity in Nd-Fe-B sintered magnets

NASA Astrophysics Data System (ADS)

Matsuura, Yutaka; Nakamura, Tetsuya; Sumitani, Kazushi; Kajiwara, Kentaro; Tamura, Ryuji; Osamura, Kozo

2018-01-01

Experimental results of the alignment dependence of the coercivity in Nd-Fe-B sintered magnets showed that the angle of magnetization reversal for anisotropically aligned magnets was bigger than that obtained from the theoretical results calculated using the postulation that every grain independently reverses its magnetization direction following the 1/cos θ law. The angles of reversed magnetization (θ1) for Nd13.48Co0.55B5.76Febal. with alignment α=0.95 and for Nd12.75Dy0.84B5.81Co0.55Febal. with α=0.96 were 30° and 36°, respectively, which were very similar to that of an ideal magnet with a Gaussian distribution (σ=31° and 44°, respectively) of the grain alignment. In this model, we postulated that every grain independently reversed according to the 1/cos θ law. The calculation results for the angular dependence of the coercivity using the values θ1=ω1(0°)=30°, σ=31° and θ1=ω1(0°)=36°, σ=44° could qualitatively and convincingly explain the observed angular dependence of the coercivity of Nd14.2B6.2Co1.0Febal. and Nd14.2Dy0.3B6.2Co1.0Febal.. It is speculated that the magnetic domain wall is pinned at grains tilted away from the easy magnetization direction, and when the magnetic domain wall de-pins from the tilted grains, the magnetic domain wall jumps through several grains. We suggest that the coercive force of the aligned magnet behaves like a low-aligned magnet owing to the magnetization reversal of the crust of the grains induced by the pinning and subsequent jumping of the magnetic domain wall.

Method of making permanent magnets

DOEpatents

McCallum, R.W.; Dennis, K.W.; Lograsso, B.K.; Anderson, I.E.

1993-09-07

A method for making an isotropic permanent magnet comprises atomizing a melt of a rare earth-transition metal alloy (e.g., an Nd--Fe--B alloy enriched in Nd and B) under conditions to produce protectively coated, rapidly solidified, generally spherical alloy particles. Wherein a majority of the particles are produced/size classified within a given size fraction (e.g., 5 to 40 microns diameter) exhibiting optimum as-atomized magnetic properties and subjecting the particles to concurrent elevated temperature and elevated isotropic pressure for a time effective to yield a densified, magnetically isotropic magnet compact having enhanced magnetic properties and mechanical properties. 13 figures.

Method of making permanent magnets

DOEpatents

McCallum, R. William; Dennis, Kevin W.; Lograsso, Barbara K.; Anderson, Iver E.

1993-09-07

A method for making an isotropic permanent magnet comprises atomizing a melt of a rare earth-transition metal alloy (e.g., an Nd--Fe--B alloy enriched in Nd and B) under conditions to produce protectively coated, rapidly solidified, generally spherical alloy particles wherein a majority of the particles are produced/size classified within a given size fraction (e.g., 5 to 40 microns diameter) exhibiting optimum as-atomized magnetic properties and subjecting the particles to concurrent elevated temperature and elevated isotropic pressure for a time effective to yield a densified, magnetically isotropic magnet compact having enhanced magnetic properties and mechanical properties.

[Influence on flux density of intraoral dental magnets during 1.5 and 3.0 tesla MRI].

PubMed

Blankenstein, F H; Truong, B; Thomas, A; Boeckler, A; Peroz, I

2011-08-01

When using dental duo-magnet systems, a mini-magnet remains in the jaw after removal of the prosthesis. In some cases, implant-borne magnets may be removed, whereas tooth-borne magnets are irreversibly fixed on a natural tooth root. The goal of this paper is to identify the impacts of the duration and orientation of exposure on these magnets in a 1.5 or 3 Tesla MRI. For this study, 30 SmCo and 60 NdFeB magnets were used. During the first experiment, they were exposed with free orientation for 64 minutes. During the second experiment, the magnets were fixed in position and exposed at 1.5 and 3 Tesla while aligned in a parallel or antiparallel direction. While the duration of exposure in MRI is irrelevant, the orientation is not. The coercive field strength of these NdFeB and SmCo alloys is not sufficient to reliably withstand demagnetization in a 1.5 or 3 T MRI when aligned in an antiparallel direction. At 1.5 T neodymium magnets were reduced to approx. 34 % and samarium magnets to approx. 92 % of their initial values. At 3 T all magnets were reversed. As a precaution, the worst-case scenario, i. e. an antiparallel orientation, should be assumed when using a duo-magnet system. If an MRI can be postponed, the general dentist should remove implant-borne magnets. If there is a vital indication, irreversible damage to the magnets is acceptable in consultation with the patient since the replacement costs are irrelevant given the underlying disease. © Georg Thieme Verlag KG Stuttgart · New York.

Enhanced method of magnetic powder alignment for production of PLP Nd-Fe-B magnets

NASA Astrophysics Data System (ADS)

Popov, A. G.; Golovnia, O. A.; Protasov, A. V.

2017-04-01

It is demonstrated how the high degree of powder alignment in PLP magnets can be achieved by loading the powder into a container placed in a magnetic field of moderate strength. The strip-cast alloy with a composition of 30.00 Nd, 1.95 Dy, 66.42 Fe, 0.99 B, 0.54 Co, 0.1 Ga (wt%) was subjected to hydrogen decrepitation and then milled in a vibratory mill in toluene to an average particle size of 2.9 μm determined by the FSSS method. The powder was compacted in the magnetic field of 0.2 - 1.2 T to the filling density 2.6 - 3.2×103 kg/m3. It is shown that loading the powder into a container placed in a magnetic field enhances the degree of powder alignment in sintered Nd-Fe-B magnets produced from non-pressed powder. At the filling density less than 3.2×103 kg/m3, the density of magnets is high but insufficient, because of the formation of magnetostatic chains of particles, which impedes the powder compaction. The simulation by the discrete-element method qualitatively proves that the magnetostatic interaction of the chains of particles that are formed in the course of loading in the magnetic field stimulates a decrease in the density of the sintered magnets and its non-uniform distribution over the sample. As a result of the optimization of the parameters of the alignment and compaction of the powder loaded in a magnetic field, PLP magnets with Br ≥1.34 T, Hc ≥950 kA/m, (BH)max ≥340 kJ/m3, and the degree of alignment exceeding 96% were produced.

Cytotoxic effect of indigenously fabricated dental magnets for application in prosthodontics.

PubMed

Guttal, Satyabodh Shesharaj; Nadiger, Ramesh K; Shetty, Pravinkumar

2018-01-01

Dental magnets are used for retaining removable prostheses such as a removable partial denture, complete denture, and maxillofacial prosthesis. They provide good retention for the prostheses. However, the elements released from the magnets may be cytotoxic for the tissues. Therefore, it is necessary to evaluate their cytotoxic effect on cell lines. The aim of the study is to check the cytotoxic effect of indigenously fabricated dental magnets on animal cell lines. Neodymium-iron-boron (Nd-Fe-B) magnet was tested for cytotoxicity. The magnet was encased in a teflon cylinder. Magnets were placed in the well tissue-cultured plates together with a suspension containing NIH 3T3 mouse fibroblasts (5 × 10 5 cells/ml). After 3 days of incubation at 37°C, cell viability was determined by mean transit time (MTT) assay. Cells were subsequently dissolved in 100 μl dimethyl sulfoxide with gentle shaking for 2 h at room temperature followed by measurement of absorbance at 570 nm. Eight replicate wells were used at each point in each of four separate measurements. Measured absorbance values were directly used for calculating percent of viable cells remaining after the respective treatment. Data were analyzed statistically with significance level set at P < 0.05. The control group had highest absorbance reading for the MTT assay followed by test group. The lowest values were found with bare Nd-Fe-B magnets. One-way ANOVA test was performed for the data obtained. There was a statistical significant difference seen in the positive control (bare magnets, 44.96) and the test (teflon cased magnets, 96.90) group. More number of viable cells was visible in test group cells indicating that the indigenously fabricated dental magnet did not show any cytotoxicity.

Nd-Fe-B/Sm-M/Nd-M (M = Fe, Co, Ti, Cu, Zr) hybrid magnets with improved thermal stability

NASA Astrophysics Data System (ADS)

Grigoras, M.; Lostun, M.; Urse, M.; Borza, F.; Chiriac, H.; Lupu, N.

2018-02-01

Hybrid magnets of Nd12Fe82B6(2:14:1-phase)/Nd9.4Fe59Co25.3Ti6.3(3:29-phase) and Nd12Fe82B6/Sm11.1Co65.8Fe8.9Cu10.7Zr3.5(2:17-phase) with different weight ratio have been prepared by spark plasma sintering pressing technique from ball-milled powders obtained from melt-spun ribbons. Influence of the ratio between the two phases on the magnetic properties and thermal stability of the hybrid magnets was studied. It has been found that the ratio has a remarkable influence, especially on the thermal stability of the bulk magnets. However, the magnetic properties of such type of hybrid magnets result not only from the type and ratio of components but also from the interaction between them. It was found that in NdFeB/3:29 hybrid magnets with 15% content of 3:29-phase, the temperature coefficients of remanence (α) and of coercivity (β) are improved from -0.095 to -0.082 (%/°C) and from -0.57 to -0.47 (%/°C), respectively, as compared to the Nd2Fe14B single-phase counterpart. While for the NdFeB/2:17 hybrid magnets the content of 2:17-phase is not significantly influencing the temperature coefficient of induction (α), the temperature coefficient of °C (β) increases up to -0.41 (%/°C) for 10% content of 2:17-phase. The increase in the reversible temperature coefficients of hybrid magnets indicate a remarkable improvement of their thermal stability.

The influence of inhomogeneous magnetic field over a NdFeB guideway on levitation force of the HTS bulk maglev system

NASA Astrophysics Data System (ADS)

Zhao, Lifeng; Deng, Jiangtao; Li, Linbo; Feng, Ning; Wei, Pu; Lei, Wei; Jiang, Jing; Wang, Xiqin; Zhang, Yong; Zhao, Yong

2018-04-01

Dynamic responses of high temperature superconducting bulk to inhomogeneous magnetic field distribution of permanent magnet guideway, as well as enlarged amplitude of magnetic field obtained by partially covering the permanent magnet guideway (PMG) with iron sheets in different thickness, are investigated. Experiments show that the instantaneous levitation force increases with the increase of the variation rate of magnetic field (dB/dt). Meanwhile, inhomogeneous magnetic field from PMG causes the decay of levitation force. The decay of levitation force almost increases linearly with the increase of alternating magnetic field amplitude. It should be very important for the application of high-speed maglev system.

Effect of low-melting point phases on the microstructure and properties of spark plasma sintered and hot deformed Nd-Fe-B alloys

NASA Astrophysics Data System (ADS)

Zhang, Li; Wang, Meiyu; Yan, Xueliang; Lin, Ye; Shield, Jeffrey

2018-04-01

The effect of adding a low melting point Pr-Cu-Al alloy during spark plasma sintering of melt-spun Nd-Fe-B ribbons is investigated. Regions of coarse grains were reduced and overall grain refinement was observed after the addition of Pr68Cu25Al7, leading to an enhancement of coercivity from 12.7 kOe to 20.4 kOe. Hot deformation of the samples in the spark plasma sintering system resulted in the formation of platelet-like grains, producing crystallographic alignment and magnetic anisotropy. The hot deformation process improved the remanence and energy product but reduced the coercivity. The decrease of coercivity resulted from grain growth and aggregation of Pr and Nd elements at triple-junction phases.

Quantitative magneto-optical investigation of superconductor/ferromagnet hybrid structures

NASA Astrophysics Data System (ADS)

Shaw, G.; Brisbois, J.; Pinheiro, L. B. G. L.; Müller, J.; Blanco Alvarez, S.; Devillers, T.; Dempsey, N. M.; Scheerder, J. E.; Van de Vondel, J.; Melinte, S.; Vanderbemden, P.; Motta, M.; Ortiz, W. A.; Hasselbach, K.; Kramer, R. B. G.; Silhanek, A. V.

2018-02-01

We present a detailed quantitative magneto-optical imaging study of several superconductor/ferromagnet hybrid structures, including Nb deposited on top of thermomagnetically patterned NdFeB and permalloy/niobium with erasable and tailored magnetic landscapes imprinted in the permalloy layer. The magneto-optical imaging data are complemented with and compared to scanning Hall probe microscopy measurements. Comprehensive protocols have been developed for calibrating, testing, and converting Faraday rotation data to magnetic field maps. Applied to the acquired data, they reveal the comparatively weaker magnetic response of the superconductor from the background of larger fields and field gradients generated by the magnetic layer.

Application of spark plasma sintering for fabricating Nd-Fe-B composite

NASA Astrophysics Data System (ADS)

Sivkov, A. A.; Ivashutenko, A. S.; Lomakina, A. A.

2015-10-01

Constant magnets are applied in such fields as electric equipment and electric generators with fixed rotor. Rare earth metal neodymium is well known as promising material. Production of magnets by sintering three elements (neodymium, iron and boron) is one the most promising methods. But there are difficulties in choosing the right temperature for sintering and further processing. Structure and properties of the product, consisted of rare earth metals, was analyzed. X-ray analysis of the resulting product and the finished constant magnet was performed. Vickers microhardness was obtained.

Magnetic navigation of an untethered micro device using four stationary coils.

PubMed

Ha, Yong H; Choi, Kyung M; Han, Byung H; Cho, Min H; Lee, Soo Y

2009-01-01

We introduce a magnetic navigation of a small magnet using four stationary coils. We used a Maxwell gradient coil to get magnetic propulsion force and three Helmholtz coils to control the moving direction of the magnet in the magnetic navigation. Using a three-channel coil driver with output capacity of 320A, we performed magnetic navigation of a small NdFeB magnet with the size of 10 mm x 10 mm x 12 mm on a horizontal plane. When navigated with a slow speed of about 1 mm/s, the magnet kept track of any arbitrary navigational path. We expect the proposed magnetic navigation method can be easily incorporated into the system for human applications since it does not use any moving coils.

Electrodeposition of amorphous Ni P coatings onto Nd Fe B permanent magnet substrates

NASA Astrophysics Data System (ADS)

Ma, C. B.; Cao, F. H.; Zhang, Z.; Zhang, J. Q.

2006-12-01

Decorative and protective Ni-P amorphous coatings were electroplated onto NdFeB permanent magnet from an ortho-phosphorous acid contained bath. The influences of the main electroplating technological parameters including current density, bath pH, bath temperature and H3PO3 on the structure and chemical composition of Ni-P coatings were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques in conjunction with X-ray diffraction (XRD), scanning transmission electron microscopy (SEM) and X-ray energy-dispersive spectrometry (EDX). The optimized amorphous Ni-P coated NdFeB can stand for ca. 180 h against neutral 3.0 wt.% NaCl salt spray without any pitting corrosion. Meanwhile, the results also showed that large phosphorous content is the precondition for Ni-P coatings to possess the amorphous structure, but too much high phosphorous content can damage the amorphous structure due to the separation of superfluous P from Ni2P/Ni3P and the resultant formation of multi-phase coatings (such as Ni2P-P).

Influence of Waiting Time on the Levitation Force Between a Permanent Magnet and a Superconductor

NASA Astrophysics Data System (ADS)

Zhang, Xing-Yi; Zhou, You-He; Zhou, Jun

This paper describes the experimental results of the levitation force of single-grained YBaCuO bulk superconductors preparing by the top-seeded melt-growth method with different waiting time tw below an NdFeB permanent magnet. It was found that waiting time has large effects on the zero-field-cooled (ZFC) and field-cooled (FC) levitation force, and the levitation force shows aging characteristics at the liquid nitrogen temperature.

Additive manufacturing of near-net-shape bonded magnets: Prospects and challenges

DOE PAGES

Li, Ling; Post, Brian; Kunc, Vlastimil; ...

2017-01-03

Additive manufacturing (AM) or 3D printing is well known for producing arbitrary shaped parts without any tooling required, offering a promising alternative to the conventional injection molding method to fabricate near-net-shaped magnets. In order to determine their applicability in the fabrication of Nd-Fe-B bondedmagnets, we compare two 3D printing technologies, namely binder jetting and material extrusion. Some prospects and challenges of these state-of-the-art technologies for large-scale industrial applications will be discussed.

Texture formation mechanism and constitutive equation for anisotropic thermorheological rare-earth permanent magnets

NASA Astrophysics Data System (ADS)

Zhu, Minggang; Li, Wei

2017-05-01

The study investigates the mechanism and constitutive equations describing oriented texture formation in anisotropic thermorheological rare-earth permanent magnets. The thermorheological process cannot be considered as creep, since the related phenomena are not suitably explained by the diffusion creep model. A mathematical model describing the relationship between the rheological deformation rate and texture orientation was established, and a theoretical expression was obtained for the orientation factor of thermorheological magnets. In addition, nanocrystalline Nd-Fe-B magnets were fabricated, with intrinsic coercivity Hcj=760.1 kA/m, remanence Br=1.469 T, and maximum energy product (BH)max=427.1 kJ/m3.

Rapid sintering of anisotropic, nanograined Nd-Fe-B by flash-spark plasma sintering

NASA Astrophysics Data System (ADS)

Castle, Elinor; Sheridan, Richard; Grasso, Salvatore; Walton, Allan; Reece, Mike

2016-11-01

A Spark Plasma Sintering (SPS) furnace was used to Flash-Sinter (FS) Nd-Fe-Dy-Co-B-Ga melt spun permanent magnetic material. During the 10 s "Flash" process (heating rate 2660 K min-1), sample sintering (to theoretical density) and deformation (54% height reduction) occurred. This produced texturing and significant magnetic anisotropy, comparable to conventional die-upset magnets; yet with much greater coercivities (>1600 kA m-1) due to the nanoscale characteristics of the plate-like sintered grains. These preliminary results suggest that Flash-SPS could provide a new processing route for the mass production of highly anisotropic, nanocrystalline magnetic materials with high coercivity.

A superconducting levitation vehicle prototype

NASA Astrophysics Data System (ADS)

Stephan, R. M.; Nicolsky, R.; Neves, M. A.; Ferreira, A. C.; de Andrade, R.; Cruz Moreira, M. A.; Rosário, M. A.; Machado, O. J.

2004-08-01

This paper presents a small scale MAGLEV vehicle prototype which is under development at UFRJ. The levitation is done by Y-Ba-Cu-O superconducting blocks refrigerated by liquid nitrogen in the presence of Nd-Fe-B magnets. A long primary linear synchronous motor gives the traction. Design considerations and experimental results show the characteristics and performance of this system.

Electromagnetic miniactuators using thin magnetic layers

NASA Astrophysics Data System (ADS)

Kube, H.; Zoeppig, V.; Hermann, R.; Hoffmann, A.; Kallenbach, E.

2000-06-01

This paper presents two examples of miniactuators based on the electromagnetic and electrodynamic force generation principle respectively. They use modern high-energy polymer-bonded permanent magnetic layers basing on NdFeB. The first example is a linear drive with an integrated magnetic bearing. It generates electrodynamic forces to lift and move a lightweight platen. The position of the platen is measured and controlled. The second example is a miniature pneumatic valve with a fully integrated polarized electromagnetic actuator. The valve consumes power only when the armature position is changed. The holding force is generated without consumption of power.

Development of a low-cost double rotor axial flux motor with soft magnetic composite and ferrite permanent magnet materials

NASA Astrophysics Data System (ADS)

Liu, Chengcheng; Zhu, Jianguo; Wang, Youhua; Guo, Youguang; Lei, Gang; Liu, Xiaojing

2015-05-01

This paper proposes a low-cost double rotor axial flux motor (DRAFM) with low cost soft magnetic composite (SMC) core and ferrite permanent magnets (PMs). The topology and operating principle of DRAFM and design considerations for best use of magnetic materials are presented. A 905 W 4800 rpm DRAFM is designed for replacing the high cost NdFeB permanent magnet synchronous motor (PMSM) in a refrigerator compressor. By using the finite element method, the electromagnetic parameters and performance of the DRAFM operated under the field oriented control scheme are calculated. Through the analysis, it is shown that that the SMC and ferrite PM materials can be good candidates for low-cost electric motor applications.

Scanning hall probe microscopy (SHPM) using quartz crystal AFM feedback.

PubMed

Dede, M; Urkmen, K; Girişen, O; Atabak, M; Oral, A; Farrer, I; Ritchie, D

2008-02-01

Scanning Hall Probe Microscopy (SHPM) is a quantitative and non-invasive technique for imaging localized surface magnetic field fluctuations such as ferromagnetic domains with high spatial and magnetic field resolution of approximately 50 nm and 7 mG/Hz(1/2) at room temperature. In the SHPM technique, scanning tunneling microscope (STM) or atomic force microscope (AFM) feedback is used to keep the Hall sensor in close proximity of the sample surface. However, STM tracking SHPM requires conductive samples; therefore the insulating substrates have to be coated with a thin layer of gold. This constraint can be eliminated with the AFM feedback using sophisticated Hall probes that are integrated with AFM cantilevers. However it is very difficult to micro fabricate these sensors. In this work, we have eliminated the difficulty in the cantilever-Hall probe integration process, just by gluing a Hall Probe chip to a quartz crystal tuning fork force sensor. The Hall sensor chip is simply glued at the end of a 32.768 kHz or 100 kHz Quartz crystal, which is used as force sensor. An LT-SHPM system is used to scan the samples. The sensor assembly is dithered at the resonance frequency using a digital Phase Locked Loop circuit and frequency shifts are used for AFM tracking. SHPM electronics is modified to detect AFM topography and the frequency shift, along with the magnetic field image. Magnetic domains and topography of an Iron Garnet thin film crystal, NdFeB demagnetised magnet and hard disk samples are presented at room temperature. The performance is found to be comparable with the SHPM using STM feedback.

Effects of thickness and annealing condition on magnetic properties and thermal stabilities of Ta/Nd/NdFeB/Nd/Ta sandwiched films

NASA Astrophysics Data System (ADS)

Liu, Wen-Feng; Zhang, Min-Gang; Zhang, Ke-Wei; Zhang, Hai-Jie; Xu, Xiao-Hong; Chai, Yue-Sheng

2016-11-01

Ta/Nd/NdFeB/Nd/Ta sandwiched films are deposited by magnetron sputtering on Si (100) substrates, and subsequently annealed in vacuum at different temperatures for different time. It is found that both the thickness of NdFeB and Nd layer and the annealing condition can affect the magnetic properties of Ta/Nd/NdFeB/Nd/Ta films. Interestingly, the thickness and annealing temperature show the relevant behaviors that can affect the magnetic properties of the film. The high coercivity of 24.1 kOe (1 Oe = 79.5775 A/m) and remanence ratio (remanent magnetization/saturation magnetization) of 0.94 can be obtained in a Ta/Nd(250 nm)/NdFeB(600 nm)/Nd(250 nm)/Ta film annealed for 3 min at 1023 K. In addition, the thermal stability of the film is also linked to the thickness of NdFeB and Nd layer and the annealing temperature as well. The excellent thermal stability can be achieved in a Ta/Nd(250 nm)/NdFeB(600 nm)/Nd(250 nm)/Ta film annealed at 1023 K. Program supported by the National Natural Science Foundation of China (Grant No. 51305290), the Higher Education Technical Innovation Project of Shanxi Province, China (Grant No. 2013133), the Fund Program for the Scientific Activities of Selected Returned Overseas Professionals of Shanxi Province, China (Grant No. 2015003), and the Program for the Key Team of Scientific and Technological Innovation of Shanxi Province, China (Grant No. 2013131009).

Simulation and Characterisation of Planar Spring Based on PCB-FR4 in Electromechanical System for Energy Harvesting

NASA Astrophysics Data System (ADS)

Fuadah, A. N.; Maulanisa, N. F.; Ismardi, A.; Sugandi, G.

2017-05-01

This paper presents comparison study of simulation and fabrication characterized two type planar springs at micro-fabricated electromagnetic power generator for an ambient vibration energy harvesting system. The power generator utilized a LASER-machined FR4-PCB planar spring, a copper coil, and NdFeB magnet. In order to change resonant frequency, we developed a gimbal suspension structure for the fabrication of spring. The NdFeB permanent magnet was applied as inertial mass. The system was specially designed to harvest low ambient vibrations from 20 to several hundred hertz and low acceleration. The dimension of fabricated energy harvester had 2.5 x 2.5 cm2 in size. In this study we present two different design of cantilever, which is has two and four cantilever, respectively. The different designed given different resonance frequency to the system. The result of simulation giving resonance frequency of two cantilever membrane 22.6 Hz and four cantilever membrane 110.3 Hz. The measurements result has generated 0.135 V with resonance frequency 39 Hz of two cantilever membrane appropriate for human motions, four cantilever membrane has generated 0.174 V with resonance frequency106 Hz appropriate for machine industries.

Polydimethylsiloxane films doped with NdFeB powder: magnetic characterization and potential applications in biomedical engineering and microrobotics.

PubMed

Iacovacci, V; Lucarini, G; Innocenti, C; Comisso, N; Dario, P; Ricotti, L; Menciassi, A

2015-12-01

This work reports the fabrication, magnetic characterization and controlled navigation of film-shaped microrobots consisting of a polydimethylsiloxane-NdFeB powder composite material. The fabrication process relies on spin-coating deposition, powder orientation and permanent magnetization. Films with different powder concentrations (10 %, 30 %, 50 % and 70 % w/w) were fabricated and characterized in terms of magnetic properties and magnetic navigation performances (by exploiting an electromagnet-based platform). Standardized data are provided, thus enabling the exploitation of these composite materials in a wide range of applications, from MEMS/microrobot development to biomedical systems. Finally, the possibility to microfabricate free-standing polymeric structures and the biocompatibility of the proposed composite materials is demonstrated.

Anisotropy and Microstructure of High Coercivity Rare Earth Iron Permanent Magnets, List of Papers Published

DTIC Science & Technology

1989-01-01

EARTH IRON PERMANENT MAGNETS. LIST OF PAPERS PUBLISHED 1986 - 1989 Contract No.: DAJA45-86-C-0010 Report No.: R/D-5295-MS-01 NOV 0 � A = LIST OF...R.Gr~ssinger - ’-Does a Co substitution really improve the temperature dependence of Nd-Fe-B based permanent magnets" .’ Proc. of 91h Int. Workshop...in NdzFe,4-4-iZx B (Z=A1,Si,Co, Ga) compounds", J. de Physique 49 (1988) CS-599. (16) R.Gr8ssinger, R.Krewenka, H.Buchn~r, H.Harada " A new analysis of

Design of a new electron cyclotron resonance ion source at Oshima National College of Maritime Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asaji, T., E-mail: asaji@oshima-k.ac.jp; Hirabara, N.; Izumihara, T.

A new electron cyclotron resonance ion/plasma source has been designed and will be built at Oshima National College of Maritime Technology by early 2014. We have developed an ion source that allows the control of the plasma parameters over a wide range of electron temperatures for material research. A minimum-B magnetic field composed of axial mirror fields and radial cusp fields was designed using mainly Nd-Fe-B permanent magnets. The axial magnetic field can be varied by three solenoid coils. The apparatus has 2.45 GHz magnetron and 2.5–6.0 GHz solid-state microwave sources.

Quantum Hall effect in epitaxial graphene with permanent magnets.

PubMed

Parmentier, F D; Cazimajou, T; Sekine, Y; Hibino, H; Irie, H; Glattli, D C; Kumada, N; Roulleau, P

2016-12-06

We have observed the well-kown quantum Hall effect (QHE) in epitaxial graphene grown on silicon carbide (SiC) by using, for the first time, only commercial NdFeB permanent magnets at low temperature. The relatively large and homogeneous magnetic field generated by the magnets, together with the high quality of the epitaxial graphene films, enables the formation of well-developed quantum Hall states at Landau level filling factors v = ±2, commonly observed with superconducting electro-magnets. Furthermore, the chirality of the QHE edge channels can be changed by a top gate. These results demonstrate that basic QHE physics are experimentally accessible in graphene for a fraction of the price of conventional setups using superconducting magnets, which greatly increases the potential of the QHE in graphene for research and applications.

Enhancement of exchange coupling interaction of NdFeB/MnBi hybrid magnets

NASA Astrophysics Data System (ADS)

Nguyen, Truong Xuan; Nguyen, Khanh Van; Nguyen, Vuong Van

2018-03-01

MnBi ribbons were fabricated by melt - spinning with subsequent annealing. The MnBi ribbons were ground and mixed with NdFeB commercial Magnequench powders (MQA). The hybrid powder mixtures were subjected thrice to the annealing and ball-milling route. The hybrid magnets (100 - x)NdFeB/xMnBi, x=0, 30, 40, 50 and 100 wt% were in-mold aligned in an 18 kOe magnetic field and warm compacted at 290 °C by 2000 psi uniaxial pressure for 10 min. An enhancement of the exchange coupling of NdFeB/MnBi hybrid magnets was obtained by optimizing the magnets' microstructures via annealing and ball-milling processes. The magnetic properties of prepared NdFeB/MnBi hybrid magnets were studied and discussed in details.

Magnetic levitation and its application for education devices based on YBCO bulk superconductors

NASA Astrophysics Data System (ADS)

Yang, W. M.; Chao, X. X.; Guo, F. X.; Li, J. W.; Chen, S. L.

2013-10-01

A small superconducting maglev propeller system, a small spacecraft model suspending and moving around a terrestrial globe, several small maglev vehicle models and a magnetic circuit converter have been designed and constructed. The track was paved by NdFeB magnets, the arrangement of the magnets made us easy to get a uniform distribution of magnetic field along the length direction of the track and a high magnetic field gradient in the lateral direction. When the YBCO bulks mounted inside the vehicle models or spacecraft model was field cooled to LN2 temperature at a certain distance away from the track, they could be automatically floating over and moving along the track without any obvious friction. The models can be used as experimental or demonstration devices for the magnetic levitation applications.

First report on soapnut extract-mediated synthesis of sulphur-substituted nanoscale NdFeB permanent magnets and their characterization

NASA Astrophysics Data System (ADS)

Jayapala Rao, G. V. S.; Prasad, T. N. V. K. V.; Shameer, Syed; Arun, T.; Purnachandra Rao, M.

2017-10-01

Biosynthesis of nanoscale materials has its own advantages over other physical and chemical methods. Using soapnut extract as reducing and stabilizing agent for the synthesis of inorganic nanoscale materials is novel and has not been exploited to its potential so far. Herein, we report for the first time on the effects of sulphur substitution on soapnut extract-mediated synthesis of nanoscale NdFeB (S-NdFeB) permanent magnetic powders (Nd 15%, Fe 77.5%, B 7.5% and S with molar ratios: 0.1, 0.2, 0.3, 0.4, and 0.5). To synthesize, a 10 ml of 10% soapnut extract was added to 90 ml of respective chemical composition and heated to 60 °C for 30 min and aged for 24 h. The dried powder was sintered at 500 °C for 1 h. The characterization of the as-prepared nanoscale S-NdFeB magnetic materials was done using the techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersion spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS for size and zeta potential measurements) and vibrating sample magnetometer (VSM)-hysteresis loop studies. The results revealed that particles were highly stable (with a negative zeta potential of 25.7 mV) with irregular and spherical shape (with measured hydrodynamic diameter 6.7 and 63.5 nm). The tetragonal structures of the formed powders were revealed by XRD micrographs. Hysteresis loop studies clearly indicate the effect of S concentration on the enhanced magnetization of the materials.

Local profile dependence of coercivity in (MM0.3Nd0.7)-Fe-B sintered magnets

NASA Astrophysics Data System (ADS)

Yu, Xiaoqiang; Zhu, Minggang; Liu, Weiqiang; Li, Wei; Sun, Yachao; Shi, Xiaoning; Yue, Ming

2018-03-01

Two magnets with the same nominal composition of (MM0.3Nd0.7)-Fe-B (Marked as A) and [(La0.27Ce0.53Pr0.03Nd0.17)0.3Nd0.7]-Fe-B (Marked as B) were prepared using traditional powder metallurgical process, respectively. In order to point out the difference between two magnets, the magnetic properties, microstructure and magnetic domain of both magnets were investigated. Both magnets have the same elements, but different raw materials of misch-metal (MM) and La/Ce/Pr/Nd pure metal, which induces different magnetic properties. The magnet A with Br of 13.1 kGs, Hcj of 7.6 kOe, (BH)max of 37.8 MGOe and magnet B with Br of 13.4 kGs, Hcj of 5.8 kOe, (BH)max of 34.5 MGOe are obtained. Although both magnets have the similar Br, magnet A has higher coercivity than that of magnet B. According to refined results of characteristic X-ray diffraction peaks, there is a hard magnetic main phase with higher magnetic anisotropy field (HA) in magnet A and opposite case happens on magnet B. SEM images demonstrate that magnet A has more continuous RE-rich phase and smaller grain size compared to that of magnet B, which contributes to enhancing the coercivity. In addition, two main phases of [Nd0.82(La, Ce)0.18]-Fe-B and [Nd0.75(La, Ce)0.25]-Fe-B were detected by the EDX calculation, and the two main phases in both magnets were observed by magnetic domains again. Compared to magnet B, 2:14:1 main phases in magnet A contain more [Nd0.82(La, Ce)0.18]-Fe-B main phases and less [Nd0.75(La, Ce)0.25]-Fe-B main phases, which also leads to higher coercivity due to the different HA among Nd2Fe14B, La2Fe14B and Ce2Fe14B phases. Therefore, it is concluded that MM substitution could exhibit better magnetic properties than (La0.27Ce0.53Pr0.03Nd0.17)-metal substitution. Furthermore, applications of MM are beneficial to fabricate (MM, Nd)-Fe-B permanent magnets with lower cost.

A transportable magnetic resonance imaging system for in situ measurements of living trees: the Tree Hugger.

PubMed

Jones, M; Aptaker, P S; Cox, J; Gardiner, B A; McDonald, P J

2012-05-01

This paper presents the design of the 'Tree Hugger', an open access, transportable, 1.1 MHz (1)H nuclear magnetic resonance imaging system for the in situ analysis of living trees in the forest. A unique construction employing NdFeB blocks embedded in a reinforced carbon fibre frame is used to achieve access up to 210 mm and to allow the magnet to be transported. The magnet weighs 55 kg. The feasibility of imaging living trees in situ using the 'Tree Hugger' is demonstrated. Correlations are drawn between NMR/MRI measurements and other indicators such as relative humidity, soil moisture and net solar radiation. Copyright © 2012 Elsevier Inc. All rights reserved.

Optical motion control of maglev graphite.

PubMed

Kobayashi, Masayuki; Abe, Jiro

2012-12-26

Graphite has been known as a typical diamagnetic material and can be levitated in the strong magnetic field. Here we show that the magnetically levitating pyrolytic graphite can be moved in the arbitrary place by simple photoirradiation. It is notable that the optical motion control system described in this paper requires only NdFeB permanent magnets and light source. The optical movement is driven by photothermally induced changes in the magnetic susceptibility of the graphite. Moreover, we demonstrate that light energy can be converted into rotational kinetic energy by means of the photothermal property. We find that the levitating graphite disk rotates at over 200 rpm under the sunlight, making it possible to develop a new class of light energy conversion system.

Effects of an external magnetic field in pulsed laser deposition

NASA Astrophysics Data System (ADS)

García, T.; de Posada, E.; Villagrán, M.; Ll, J. L. Sánchez; Bartolo-Pérez, P.; Peña, J. L.

2008-12-01

Thin films were grown by pulsed laser deposition, PLD, on Si (1 0 0) substrates by the ablation of a sintered ceramic SrFe 12O 19 target with and without the presence of a nonhomogeneous magnetic field of μ0H = 0.4 T perpendicular to substrate plane and parallel to the plasma expansion axis. The field was produced by a rectangular-shaped Nd-Fe-B permanent magnet and the substrate was just placed on the magnet surface (Aurora method). An appreciable increment of optical emission due to the presence of the magnetic field was observed, but no film composition change or thickness increment was obtained. It suggests that the increment of the optical emission is due mainly to the electron confinement rather than confinement of ionic species.

Note: Enhanced energy harvesting from low-frequency magnetic fields utilizing magneto-mechano-electric composite tuning-fork.

PubMed

Yang, Aichao; Li, Ping; Wen, Yumei; Yang, Chao; Wang, Decai; Zhang, Feng; Zhang, Jiajia

2015-06-01

A magnetic-field energy harvester using a low-frequency magneto-mechano-electric (MME) composite tuning-fork is proposed. This MME composite tuning-fork consists of a copper tuning fork with piezoelectric Pb(Zr(1-x)Ti(x))O3 (PZT) plates bonded near its fixed end and with NdFeB magnets attached at its free ends. Due to the resonance coupling between fork prongs, the MME composite tuning-fork owns strong vibration and high Q value. Experimental results show that the proposed magnetic-field energy harvester using the MME composite tuning-fork exhibits approximately 4 times larger maximum output voltage and 7.2 times higher maximum power than the conventional magnetic-field energy harvester using the MME composite cantilever.

[Signal loss in magnetic resonance imaging caused by intraoral anchored dental magnetic materials].

PubMed

Blankenstein, F H; Truong, B; Thomas, A; Schröder, R J; Naumann, M

2006-08-01

To measure the maximum extent of the signal loss areas in the center of the susceptibility artifacts generated by ferromagnetic dental magnet attachments using three different sequences in the 1.5 and 3.0 Tesla MRI. Five different pieces of standard dental magnet attachments with volumes of 6.5 to 31.4 mm(3) were used: a NdFeB magnet with an open magnetic field, a NdFeB magnet with a closed magnetic field, a SmCo magnet with an open magnetic field, a stainless steel keeper (AUM-20) and a PdCo piece. The attachments were placed between two cylindrical phantoms and examined in 1.5 and 3.0 Tesla MRI using gradient echo and T1- and T2-weighted spin echoes. We measured the maximum extent of the generated signal loss areas parallel and perpendicular to the direction of B (O). In gradient echoes the artifacts were substantially larger and symmetrically adjusted around the object. The areas with total signal loss were mushroom-like with a maximum extent of 7.4 to 9.7 cm parallel to the direction of B (O) and 6.7 to 7.4 cm perpendicular to B (O). In spin echoes the signal loss areas were obviously smaller, but not centered. The maximum values ranged between 4.9 and 7.2 cm (parallel B (O)) and 3.6 and 7.0 cm (perpendicular B (O)). The different ferromagnetic attachments had no clinically relevant influence on the signal loss neither in 1.5 T nor 3.0 T MRI. Ferromagnetic materials used in dentistry are not intraorally standardized. To ensure, that the area of interest is not affected by the described artifacts, the maximum extent of the signal loss area should be assumed: a radius of up to 7 cm in 1.5 and 3.0 T MRI by T1 and T2 sequences, and a radius of up to 10 cm in T2* sequences. To decide whether magnet attachments have to be removed before MR imaging, physicians should consider both the intact retention of the keepers and the safety distance between the ferromagnetic objects and the area of interest.

Topology optimization of reduced rare-earth permanent magnet arrays with finite coercivity

NASA Astrophysics Data System (ADS)

Teyber, R.; Trevizoli, P. V.; Christiaanse, T. V.; Govindappa, P.; Rowe, A.

2018-05-01

The supply chain risk of rare-earth permanent magnets has yielded research efforts to improve both materials and magnetic circuits. While a number of magnet optimization techniques exist, literature has not incorporated the permanent magnet failure process stemming from finite coercivity. To address this, a mixed-integer topology optimization is formulated to maximize the flux density of a segmented Halbach cylinder while avoiding permanent demagnetization. The numerical framework is used to assess the efficacy of low-cost (rare-earth-free ferrite C9), medium-cost (rare-earth-free MnBi), and higher-cost (Dy-free NdFeB) permanent magnet materials. Novel magnet designs are generated that produce flux densities 70% greater than the segmented Halbach array, albeit with increased magnet mass. Three optimization formulations are then explored using ferrite C9 that demonstrates the trade-off between manufacturability and design sophistication, generating flux densities in the range of 0.366-0.483 T.

Tessellated permanent magnet circuits for flow-through, open gradient separations of weakly magnetic materials

PubMed Central

Moore, Lee R.; Williams, P. Stephen; Chalmers, Jeffrey J.; Zborowski, Maciej

2017-01-01

Emerging microfluidic-based cell assays favor label-free red blood cell (RBC) depletion. Magnetic separation of RBC is possible because of the paramagnetism of deoxygenated hemoglobin but the process is slow for open-gradient field configurations. In order to increase the throughput, periodic arrangements of the unit magnets were considered, consisting of commercially available Nd-Fe-B permanent magnets and soft steel flux return pieces. The magnet design is uniquely suitable for multiplexing by magnet tessellation, here meaning the tiling of the magnet assembly cross-sectional plane by periodic repetition of the magnet and the flow channel shapes. The periodic pattern of magnet magnetizations allows a reduction of the magnetic material per channel with minimal distortion of the field cylindrical symmetry inside the magnet apertures. A number of such magnet patterns are investigated for separator performance, size and economy with the goal of designing an open-gradient magnetic separator capable of reducing the RBC number concentration a hundred-fold in 1 mL whole blood per hour. PMID:29104346

Tessellated permanent magnet circuits for flow-through, open gradient separations of weakly magnetic materials.

PubMed

Moore, Lee R; Williams, P Stephen; Chalmers, Jeffrey J; Zborowski, Maciej

2017-04-01

Emerging microfluidic-based cell assays favor label-free red blood cell (RBC) depletion. Magnetic separation of RBC is possible because of the paramagnetism of deoxygenated hemoglobin but the process is slow for open-gradient field configurations. In order to increase the throughput, periodic arrangements of the unit magnets were considered, consisting of commercially available Nd-Fe-B permanent magnets and soft steel flux return pieces. The magnet design is uniquely suitable for multiplexing by magnet tessellation, here meaning the tiling of the magnet assembly cross-sectional plane by periodic repetition of the magnet and the flow channel shapes. The periodic pattern of magnet magnetizations allows a reduction of the magnetic material per channel with minimal distortion of the field cylindrical symmetry inside the magnet apertures. A number of such magnet patterns are investigated for separator performance, size and economy with the goal of designing an open-gradient magnetic separator capable of reducing the RBC number concentration a hundred-fold in 1 mL whole blood per hour.

Framework for resilience in material supply chains, with a case study from the 2010 Rare Earth Crisis.

PubMed

Sprecher, Benjamin; Daigo, Ichiro; Murakami, Shinsuke; Kleijn, Rene; Vos, Matthijs; Kramer, Gert Jan

2015-06-02

In 2010, Chinese export restrictions caused the price of the rare earth element neodymium to increase by a factor of 10, only to return to almost normal levels in the following months. This despite the fact that the restrictions were not lifted. The significant price peak shows that this material supply chain was only weakly resistant to a major supply disruption. However, the fact that prices rapidly returned to lower levels implies a certain resilience. With the help of a novel approach, based on resilience theory combined with a material flow analysis (MFA) based representation of the neodymium magnet (NdFeB) supply chain, we show that supply chain resilience is composed of various mechanisms, including (a) resistance, (b) rapidity, and (c) flexibility, that originate from different parts of the supply chain. We make recommendations to improve the capacity of the NdFeB system to deal with future disruptions and discuss potential generalities for the resilience of other material supply chains.

A large-diameter hollow-shaft cryogenic motor based on a superconducting magnetic bearing for millimeter-wave polarimetry.

PubMed

Johnson, B R; Columbro, F; Araujo, D; Limon, M; Smiley, B; Jones, G; Reichborn-Kjennerud, B; Miller, A; Gupta, S

2017-10-01

In this paper, we present the design and measured performance of a novel cryogenic motor based on a superconducting magnetic bearing (SMB). The motor is tailored for use in millimeter-wave half-wave plate (HWP) polarimeters, where a HWP is rapidly rotated in front of a polarization analyzer or polarization-sensitive detector. This polarimetry technique is commonly used in cosmic microwave background polarization studies. The SMB we use is composed of fourteen yttrium barium copper oxide (YBCO) disks and a contiguous neodymium iron boron (NdFeB) ring magnet. The motor is a hollow-shaft motor because the HWP is ultimately installed in the rotor. The motor presented here has a 100 mm diameter rotor aperture. However, the design can be scaled up to rotor aperture diameters of approximately 500 mm. Our motor system is composed of four primary subsystems: (i) the rotor assembly, which includes the NdFeB ring magnet, (ii) the stator assembly, which includes the YBCO disks, (iii) an incremental encoder, and (iv) the drive electronics. While the YBCO is cooling through its superconducting transition, the rotor is held above the stator by a novel hold and release mechanism. The encoder subsystem consists of a custom-built encoder disk read out by two fiber optic readout sensors. For the demonstration described in this paper, we ran the motor at 50 K and tested rotation frequencies up to approximately 10 Hz. The feedback system was able to stabilize the rotation speed to approximately 0.4%, and the measured rotor orientation angle uncertainty is less than 0.15°. Lower temperature operation will require additional development activities, which we will discuss.

A large-diameter hollow-shaft cryogenic motor based on a superconducting magnetic bearing for millimeter-wave polarimetry

NASA Astrophysics Data System (ADS)

Johnson, B. R.; Columbro, F.; Araujo, D.; Limon, M.; Smiley, B.; Jones, G.; Reichborn-Kjennerud, B.; Miller, A.; Gupta, S.

2017-10-01

In this paper, we present the design and measured performance of a novel cryogenic motor based on a superconducting magnetic bearing (SMB). The motor is tailored for use in millimeter-wave half-wave plate (HWP) polarimeters, where a HWP is rapidly rotated in front of a polarization analyzer or polarization-sensitive detector. This polarimetry technique is commonly used in cosmic microwave background polarization studies. The SMB we use is composed of fourteen yttrium barium copper oxide (YBCO) disks and a contiguous neodymium iron boron (NdFeB) ring magnet. The motor is a hollow-shaft motor because the HWP is ultimately installed in the rotor. The motor presented here has a 100 mm diameter rotor aperture. However, the design can be scaled up to rotor aperture diameters of approximately 500 mm. Our motor system is composed of four primary subsystems: (i) the rotor assembly, which includes the NdFeB ring magnet, (ii) the stator assembly, which includes the YBCO disks, (iii) an incremental encoder, and (iv) the drive electronics. While the YBCO is cooling through its superconducting transition, the rotor is held above the stator by a novel hold and release mechanism. The encoder subsystem consists of a custom-built encoder disk read out by two fiber optic readout sensors. For the demonstration described in this paper, we ran the motor at 50 K and tested rotation frequencies up to approximately 10 Hz. The feedback system was able to stabilize the rotation speed to approximately 0.4%, and the measured rotor orientation angle uncertainty is less than 0.15°. Lower temperature operation will require additional development activities, which we will discuss.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Ling; Post, Brian; Kunc, Vlastimil

Additive manufacturing (AM) or 3D printing is well known for producing arbitrary shaped parts without any tooling required, offering a promising alternative to the conventional injection molding method to fabricate near-net-shaped magnets. In order to determine their applicability in the fabrication of Nd-Fe-B bondedmagnets, we compare two 3D printing technologies, namely binder jetting and material extrusion. Some prospects and challenges of these state-of-the-art technologies for large-scale industrial applications will be discussed.

A compact permanent-magnet system for measuring magnetic circular dichroism in resonant inelastic soft X-ray scattering.

PubMed

Miyawaki, Jun; Suga, Shigemasa; Fujiwara, Hidenori; Niwa, Hideharu; Kiuchi, Hisao; Harada, Yoshihisa

2017-03-01

A compact and portable magnet system for measuring magnetic dichroism in resonant inelastic soft X-ray scattering (SX-RIXS) has been developed at the beamline BL07LSU in SPring-8. A magnetic circuit composed of Nd-Fe-B permanent magnets, which realised ∼0.25 T at the center of an 11 mm gap, was rotatable around the axis perpendicular to the X-ray scattering plane. Using the system, a SX-RIXS spectrum was obtained under the application of the magnetic field at an angle parallel, nearly 45° or perpendicular to the incident X-rays. A dedicated sample stage was also designed to be as compact as possible, making it possible to perform SX-RIXS measurements at arbitrary incident angles by rotating the sample stage in the gap between the magnetic poles. This system enables facile studies of magnetic dichroism in SX-RIXS for various experimental geometries of the sample and the magnetic field. A brief demonstration of the application is presented.

Study on static and dynamic characteristics of moving magnet linear compressors

NASA Astrophysics Data System (ADS)

Chen, N.; Tang, Y. J.; Wu, Y. N.; Chen, X.; Xu, L.

2007-09-01

With the development of high-strength NdFeB magnetic material, moving magnet linear compressors have been gradually introduced in the fields of refrigeration and cryogenic engineering, especially in Stirling and pulse tube cryocoolers. This paper presents simulation and experimental investigations on the static and dynamic characteristics of a moving magnet linear motor and a moving magnet linear compressor. Both equivalent magnetic circuits and finite element approaches have been used to model the moving magnet linear motor. Subsequently, the force and equilibrium characteristics of the linear motor have been predicted and verified by detailed static experimental analyses. In combination with a harmonic analysis, experimental investigations were conducted on a prototype of a moving magnet linear compressor. A voltage-stroke relationship, the effect of charging pressure on the performance and dynamic frequency response characteristics are investigated. Finally, the method to identify optimal points of the linear compressor has been described, which is indispensable to the design and operation of moving magnet linear compressors.

Centrifugal Force Based Magnetic Micro-Pump Driven by Rotating Magnetic Fields

NASA Astrophysics Data System (ADS)

Kim, S. H.; Hashi, S.; Ishiyama, K.

2011-01-01

This paper presents a centrifugal force based magnetic micro-pump for the pumping of blood. Most blood pumps are driven by an electrical motor with wired control. To develop a wireless and battery-free blood pump, the proposed pump is controlled by external rotating magnetic fields with a synchronized impeller. Synchronization occurs because the rotor is divided into multi-stage impeller parts and NdFeB permanent magnet. Finally, liquid is discharged by the centrifugal force of multi-stage impeller. The proposed pump length is 30 mm long and19 mm in diameter which much smaller than currently pumps; however, its pumping ability satisfies the requirement for a blood pump. The maximum pressure is 120 mmHg and the maximum flow rate is 5000ml/min at 100 Hz. The advantage of the proposed pump is that the general mechanical problems of a normal blood pump are eliminated by the proposed driving mechanism.

Design, fabrication, and characterization of a valveless magnetic travelling-wave micropump

NASA Astrophysics Data System (ADS)

Yu, Huawei; Ye, Weixiang; Zhang, Wei; Yue, Zhao; Liu, Guohua

2015-06-01

In this paper, we propose a valveless magnetic micropump for lab-on-a-chip and microfluidic applications. The micropump, based on polydimethylsiloxane (PDMS) and polymethylmethacrylate (PMMA), consists primarily of a saw-toothed microchannel, two substrates, and two integrated NdFeB permanent magnetic arrays. The travelling wave beneath the top wall of the elastic microchannel can be induced by the proper magnetic pole orientation arrangement of these magnetic arrays, and the liquid particles are then transported along with the travelling wave in the microchannel. Appropriate geometry of the saw-toothed microchannel was also studied for optimizing the performance of the micropump. Experimental characterization of the micropump has been performed in terms of the frequency response of the flow rate and backpressure. The results demonstrate that this micropump is capable of reliably generating a maximum flow rate of 342.4 μL min-1 and operating against a high backpressure of 1.67 kPa.

Recovery of rare earths from spent NdFeB magnets of wind turbine: Leaching and kinetic aspects.

PubMed

Kumari, Aarti; Sinha, Manish Kumar; Pramanik, Swati; Sahu, Sushanta Kumar

2018-05-01

Increasing demands of rare earth (RE) metals for advanced technological applications coupled with the scarcity of primary resources have led to the development of processes to treat secondary resources like scraps or end of life products that are often rich in such metals. Spent NdFeB magnet may serve as a potential source of rare earths containing around ∼30% of neodymium and other rare earths. In the present investigation, a pyro-hydrometallurgical process has been developed to recover rare earth elements (Nd, Pr and Dy) from the spent wind turbine magnet. The spent magnet is demagnetized and roasted at 1123 K to convert rare earths and iron to their respective oxides. Roasting of the magnet not only provides selectivity, but enhances the leaching efficiency also. The leaching of the roasted sample with 0.5 M hydrochloric acid at 368 K, 100 g/L pulp density and 500 rpm for 300 min selectively recovers the rare earth elements almost quantitatively leaving iron oxide in the residue. Leaching of rare earth elements with hydrochloric acid follows the mixed controlled kinetic model with activation energy (E a ) of 30.1 kJ/mol in the temperature range 348-368 K. The leaching mechanism is further established by characterizing the leach residues obtained at different time intervals by scanning electron microscopy- energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction (XRD). Individual rare earth elements from the leach solution containing 16.8 g/L of Nd, 3.8 g/L Pr, 0.28 g/L of Dy and other minor impurity elements could be separated by solvent extraction. However, mixed rare earth oxide of 99% purity was produced by oxalate precipitation followed by roasting. The leach residue comprising of pure hematite has a potential to be used as pigment or can find other applications. Copyright © 2018 Elsevier Ltd. All rights reserved.

Magnetic levitation in the analysis of foods and water.

PubMed

Mirica, Katherine A; Phillips, Scott T; Mace, Charles R; Whitesides, George M

2010-06-09

This paper describes a method and a sensor that use magnetic levitation (MagLev) to characterize samples of food and water on the basis of measurements of density. The sensor comprises two permanent NdFeB magnets positioned on top of each other in a configuration with like poles facing and a container filled with a solution of paramagnetic ions. Measurements of density are obtained by suspending a diamagnetic object in the container filled with the paramagnetic fluid, placing the container between the magnets, and measuring the vertical position of the suspended object. MagLev was used to estimate the salinity of water, to compare a variety of vegetable oils on the basis of the ratio of polyunsaturated fat to monounsaturated fat, to compare the contents of fat in milk, cheese, and peanut butter, and to determine the density of grains.

Life on magnets: stem cell networking on micro-magnet arrays.

PubMed

Zablotskii, Vitalii; Dejneka, Alexandr; Kubinová, Šárka; Le-Roy, Damien; Dumas-Bouchiat, Frédéric; Givord, Dominique; Dempsey, Nora M; Syková, Eva

2013-01-01

Interactions between a micro-magnet array and living cells may guide the establishment of cell networks due to the cellular response to a magnetic field. To manipulate mesenchymal stem cells free of magnetic nanoparticles by a high magnetic field gradient, we used high quality micro-patterned NdFeB films around which the stray field's value and direction drastically change across the cell body. Such micro-magnet arrays coated with parylene produce high magnetic field gradients that affect the cells in two main ways: i) causing cell migration and adherence to a covered magnetic surface and ii) elongating the cells in the directions parallel to the edges of the micro-magnet. To explain these effects, three putative mechanisms that incorporate both physical and biological factors influencing the cells are suggested. It is shown that the static high magnetic field gradient generated by the micro-magnet arrays are capable of assisting cell migration to those areas with the strongest magnetic field gradient, thereby allowing the build up of tunable interconnected stem cell networks, which is an elegant route for tissue engineering and regenerative medicine.

Life on Magnets: Stem Cell Networking on Micro-Magnet Arrays

PubMed Central

Zablotskii, Vitalii; Dejneka, Alexandr; Kubinová, Šárka; Le-Roy, Damien; Dumas-Bouchiat, Frédéric; Givord, Dominique; Dempsey, Nora M.; Syková, Eva

2013-01-01

Interactions between a micro-magnet array and living cells may guide the establishment of cell networks due to the cellular response to a magnetic field. To manipulate mesenchymal stem cells free of magnetic nanoparticles by a high magnetic field gradient, we used high quality micro-patterned NdFeB films around which the stray field’s value and direction drastically change across the cell body. Such micro-magnet arrays coated with parylene produce high magnetic field gradients that affect the cells in two main ways: i) causing cell migration and adherence to a covered magnetic surface and ii) elongating the cells in the directions parallel to the edges of the micro-magnet. To explain these effects, three putative mechanisms that incorporate both physical and biological factors influencing the cells are suggested. It is shown that the static high magnetic field gradient generated by the micro-magnet arrays are capable of assisting cell migration to those areas with the strongest magnetic field gradient, thereby allowing the build up of tunable interconnected stem cell networks, which is an elegant route for tissue engineering and regenerative medicine. PMID:23936425

Magnetizing technique for permanent magnets by intense static fields generated by HTS bulk magnets: Numerical Analysis

NASA Astrophysics Data System (ADS)

N. Kawasaki; Oka, T.; Fukui, S.; Ogawa, J.; Sato, T.; Terasawa, T.; Itoh, Y.

A demagnetized Nd-Fe-B permanent magnet was scanned in the strong magnetic field space just above the magnetic pole containing a HTS bulk magnet which generates the magnetic field 3.4 T. The magnet sample was subsequently found to be fully magnetized in the open space of the static magnetic fields. The finite element method was carried out for the static field magnetization of a permanent magnet using a HTS bulk magnet. Previously, our research group experimentally demonstrated the possibility of full magnetization of rare earth permanent magnets with high-performance magnetic properties with use of the static field of HTS bulk magnets. In the present study, however, we succeeded for the first time in visualizing the behavior of the magnetizing field of the bulk magnet during the magnetization process and the shape of the magnetic field inside the body being magnetized. By applying this kind of numerical analysis to the magnetization for planned motor rotors which incorporate rare-earth permanent magnets, we hope to study the fully magnetized regions for the new magnetizing method using bulk magnets and to give motor designing a high degree of freedom.

A new method to determine magnetic properties of the unsaturated-magnetized rotor of a novel gyro

NASA Astrophysics Data System (ADS)

Li, Hai; Liu, Xiaowei; Dong, Changchun; Zhang, Haifeng

2016-06-01

A new method is proposed to determine magnetic properties of the unsaturated-magnetized, small and irregular shaped rotor of a novel gyro. The method is based on finite-element analysis and the measurements of the magnetic flux density distribution, determining magnetic parameters by comparing the magnetic flux intensity distribution differences between the modeling results under different parameters and the measured ones. Experiment on a N30 Grade NdFeB magnet shows that its residual magnetic flux density is 1.10±0.01 T, and coercive field strength is 801±3 kA/m, which are consistent with the given parameters of the material. The method was applied to determine the magnetic properties of the rotor of the gyro, and the magnetic properties acquired were used to predict the open-loop gyro precession frequency. The predicted precession frequency should be larger than 12.9 Hz, which is close to the experimental result 13.5 Hz. The result proves that the method is accurate in estimating the magnetic properties of the rotor of the gyro.

Changes in the topography of cellular components in pea root statocytes exposed to high gradient magnetic fields

NASA Astrophysics Data System (ADS)

Belyavskaya, Ninel A.; Polishchuk, Olexandr V.; Kondrachuk, Alexander V.

2005-08-01

High-gradient magnetic field (HGMF) is one of methods, by which gravitropism in plants is studied. The aim of our study was elucidation of HGMF effects on topography of cellular components in root statocytes of 4- day Pisum sativum L. seedlings in comparison to gravistimulation. Under gravistimulation during 5, 30 and 60 min seedlings were rotated 45o; magnetostimulation was carried out along gap between two NdFeB magnets (0.7 T). Morphometric measurements were made from images of whole statocytes, for upper, middle and lower thirds of cells, and proximal and distal halves of cells. Morphometric analysis revealed that HGMF resulted in the redistribution of all cellular components in statocytes. The correlation in the amyloplast distribution between gravistimulation and magnetostimulation was established.

Repulsive force support system feasibility study

NASA Technical Reports Server (NTRS)

Boom, R. W.; Abdelsalam, M. K.; Eyssa, Y. M.; Mcintosh, G. E.

1987-01-01

A new concept in magnetic levitation and control is introduced for levitation above a plane. A set of five vertical solenoid magnets mounted flush below the plane supports and controls the model in five degrees of freedom. The compact system of levitation coils is contained in a space 2.4 m (96 in) diameter by 1 m (40 in) deep with the top of the levitation system 0.9 m (36 in) below the center line of the suspended model. The levitated model has a permanent magnet core held in position by the five parallel superconductive solenoids symmetrically located in a circle. The control and positioning system continuously corrects for model position in five dimensions using computer current pulses superimposed on the levitation coil base currents. The conceptual designs include: superconductive and Nd-Fe-B permanent magnet model cores and levitation solenoids of either superconductive, cryoresistive, or room temperature windings.

Vibration measurements and analyses for a magnet superconductor levitated system

NASA Astrophysics Data System (ADS)

Wen, Zheng; Liu, Yu; Yang, Wenjiang; Qiu, Ming

2007-12-01

Magnetic levitation technology, having the characteristics of low cost and high quality, has been considered a preferable option for the next generation of launcher systems. A world-wide research design on the conceptual level has been carried out on the highly reusable space transportation systems by applying magnetic levitation to the launch assistance. Recently, a research plan has been implemented in our laboratory by constructing a scale-model suspension system with high temperature superconductor (HTS henceforth) bulks over a 7 m Nd-Fe-B permanent-magnet (PM henceforth) track for the launch assistance. An experimental platform was built to investigate the dynamic responses of the PM-HTS interaction at different field-cooled positions. The critical frequencies and amplitudes which lead to the instability of levitation drift were investigated. The stiffness and the vibration damping were also discussed at the zero-field-cooled position.

Spherical, rolling magnet generators for passive energy harvesting from human motion

NASA Astrophysics Data System (ADS)

Bowers, Benjamin J.; Arnold, David P.

2009-09-01

In this work, non-resonant, vibrational energy harvester architectures intended for human-motion energy scavenging are researched. The basic design employs a spherical, unidirectionally magnetized permanent magnet (NdFeB) ball that is allowed to move arbitrarily in a spherical cavity wrapped with copper coil windings. As the ball rotates and translates within the cage, the time-varying magnetic flux induces a voltage in the coil according to Faraday's Law. Devices ranging from 1.5 cm3 to 4 cm3 in size were tested under human activity scenarios—held in the user's hand or placed in the user's pocket while walking (4 km h-1) and running (14.5 km h-1). These harvesters have demonstrated rms voltages ranging from ~80 mV to 700 mV and time-averaged power densities up to 0.5 mW cm-3.

A table top experiment to investigate production and properties of a plasma confined by a dipole magnet

NASA Astrophysics Data System (ADS)

Baitha, Anuj Ram; Kumar, Ashwani; Bhattacharjee, Sudeep

2018-02-01

We report a table top experiment to investigate production and properties of a plasma confined by a dipole magnet. A water cooled, strong, cylindrical permanent magnet (NdFeB) magnetized along the axial direction and having a surface magnetic field of ˜0.5 T is employed to create a dipole magnetic field. The plasma is created by electron cyclotron resonance heating. Visual observations of the plasma indicate that radiation belts appear due to trapped particles, similar to the earth's magnetosphere. The electron temperature lies in the range 2-13 eV and is hotter near the magnets and in a downstream region. It is found that the plasma (ion) density reaches a value close to 2 × 1011 cm-3 and peaks at a radial distance about 3 cm from the magnet. The plasma beta β (β = plasma pressure/magnetic pressure) increases radially outward, and the maximum β for the present experimental system is ˜2%. It is also found that the singly charged ions are dominant in the discharge.

A high-damping magnetorheological elastomer with bi-directional magnetic-control modulus for potential application in seismology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Miao, E-mail: yumiao@cqu.edu.cn; Qi, Song; Fu, Jie

A high-damping magnetorheological elastomer (MRE) with bi-directional magnetic-control modulus is developed. This MRE was synthesized by filling NdFeB particles into polyurethane (PU)/ epoxy (EP) interpenetrating network (IPN) structure. The anisotropic samples were prepared in a permanent magnetic field and magnetized in an electromagnetic field of 1 T. Dynamic mechanical responses of the MRE to applied magnetic fields are investigated through magneto-rheometer, and morphology of MREs is observed via scanning electron microscope (SEM). Test result indicates that when the test field orientation is parallel to that of the sample's magnetization, the shear modulus of sample increases. On the other hand, when themore » orientation is opposite to that of the sample's magnetization, shear modulus decreases. In addition, this PU/EP IPN matrix based MRE has a high-damping property, with high loss factor and can be controlled by applying magnetic field. It is expected that the high damping property and the ability of bi-directional magnetic-control modulus of this MRE offer promising advantages in seismologic application.« less

Polarized Linear Motor Combined With Levitation Actuators Working in a Partial Vacuum Environment—Application to Swissmetro

NASA Astrophysics Data System (ADS)

Cassat, Alain; Espanet, Christophe; Bourquin, Vincent; Hagmann, Pascal; Jufer, Marcel

Worldwide high speed Maglev (> 400km/h) developments refer to Maglev such as the Japanese JR-Maglev MLX, the German Transrapid and the USA Inductrack Maglev. Other world projects exist such as the Japan HSST (< 300km/h) and the China HTC. The JR-Maglev, the Transrapid and the HSST have reached industrial levels. The Swissmetro Project presents a unique aspect of Maglev: it is designed to work under partial vacuum (< 10kPa) in two tunnels and for high speeds (>400km/h). The authors investigate new possibilities to combine both the propulsion and the levitation. In order to minimize the heat due to the motor levitation and guidance losses, a polarized excitation is proposed. The use of permanent magnet NdFeB for the excitation is still not applied for high speed Maglev, requiring mechanical power greater than 6MW. Such a solution only appears in Urban Rapid Transit Maglev (<160km/h), such as the USA MagneMotion M3 and the General Atomic Urban Maglev. For Swissmetro, the authors study the polarized inductors for the levitation, implying a polarized synchronous linear motor. The polarization is obtained with permanent magnets NdFeB. This paper presents some key issues related to such technical choices. The motor design is described and the power balance is presented. The thermal behavior is analyzed using a numerical platform of the complete vehicle-tunnel system, based on computation of the air flow dynamic.

A permanent magnet trap for buffer gas cooled atoms and molecules

NASA Astrophysics Data System (ADS)

Nohlmans, D.; Skoff, S. M.; Hendricks, R. J.; Segal, D. M.; Sauer, B. E.; Hinds, E. A.; Tarbutt, M. R.

2013-05-01

Cold molecules are set to provide a wealth of new science compared to their atomic counterparts. Here we want to present preliminary results for cooling and trapping atoms/molecules in a permanent magnetic trap. By replacing the conventional buffer gas cell with an arrangement of permanent magnets, we will be able to trap a fraction of the molecules right where they are cooled. For this purpose we have designed a quadrupole trap using NdFeB magnets, which has a trap depth of 0.4 K for molecules with a magnetic moment of 1 μB. Cold helium gas is pulsed into the trap region by a solenoid valve and the atoms/molecules are subsequently ablated into this and cooled via elastic collisions, leaving a fraction of them trapped. This new set-up is currently being tested with lithium atoms as they are easier to make. After having optimised the trapping and detection processes, we will use the same trap for YbF molecules.

Rare earth-transition metal scrap treatment method

DOEpatents

Schmidt, Frederick A.; Peterson, David T.; Wheelock, John T.; Jones, Lawrence L.; Lincoln, Lanny P.

1992-02-11

Rare earth-transition metal (e.g. iron) scrap (e.g. Nd-Fe-B scrap) is melted to reduce the levels of tramp oxygen and nitrogen impurities therein. The tramp impurities are reduced in the melt by virtue of the reaction of the tramp impurities and the rare earth to form dross on the melt. The purified melt is separated from the dross for reuse. The oxygen and nitrogen of the melt are reduced to levels acceptable for reuse of the treated alloy in the manufacture of end-use articles, such as permanent magnets.

Rare earth-transition metal scrap treatment method

DOEpatents

Schmidt, F.A.; Peterson, D.T.; Wheelock, J.T.; Jones, L.L.; Lincoln, L.P.

1992-02-11

Rare earth-transition metal (e.g. iron) scrap (e.g. Nd-Fe-B scrap) is melted to reduce the levels of tramp oxygen and nitrogen impurities therein. The tramp impurities are reduced in the melt by virtue of the reaction of the tramp impurities and the rare earth to form dross on the melt. The purified melt is separated from the dross for reuse. The oxygen and nitrogen of the melt are reduced to levels acceptable for reuse of the treated alloy in the manufacture of end-use articles, such as permanent magnets. 3 figs.

MagLev Cobra: Test Facilities and Operational Experiments

NASA Astrophysics Data System (ADS)

Sotelo, G. G.; Dias, D. H. J. N.; de Oliveira, R. A. H.; Ferreira, A. C.; De Andrade, R., Jr.; Stephan, R. M.

2014-05-01

The superconducting MagLev technology for transportation systems is becoming mature due to the research and developing effort of recent years. The Brazilian project, named MagLev-Cobra, started in 1998. It has the goal of developing a superconducting levitation vehicle for urban areas. The adopted levitation technology is based on the diamagnetic and the flux pinning properties of YBa2Cu3O7-δ (YBCO) bulk blocks in the interaction with Nd-Fe-B permanent magnets. A laboratory test facility with permanent magnet guideway, linear induction motor and one vehicle module is been built to investigate its operation. The MagLev-Cobra project state of the art is presented in the present paper, describing some construction details of the new test line with 200 m.

Demonstrating the conservation of angular momentum using spherical magnets

NASA Astrophysics Data System (ADS)

Lindén, Johan; Slotte, Joakim; Källman, Kjell-Mikael

2018-01-01

An experimental setup for demonstrating the conservation of angular momentum of rotating spherical magnets is described. Two spherical Nd-Fe-B magnets are placed on a double inclined plane and projected towards each other with pre-selected impact parameters ranging from zero to a few tens of millimeters. After impact, the two magnets either revolve vigorously around the common center of mass or stop immediately, depending on the value of the impact parameter. Using a pick-up coil connected to an oscilloscope, the angular frequency for the rotating magnets was measured, and an estimate for the angular momentum was obtained. A high-speed video camera captured the impact and was used for measuring linear and angular velocities of the magnets. A very good agreement between the initial angular momentum before the impact and the final angular momentum of the revolving dumbbell is observed. The two rotating magnets, and the rotating electromagnetic field emanating from them, can also be viewed as a toy model for the newly discovered gravitational waves, where two black holes collide after revolving around each other. (Enhanced online)

Magnetic forces and magnetized biomaterials provide dynamic flux information during bone regeneration.

PubMed

Russo, Alessandro; Bianchi, Michele; Sartori, Maria; Parrilli, Annapaola; Panseri, Silvia; Ortolani, Alessandro; Sandri, Monica; Boi, Marco; Salter, Donald M; Maltarello, Maria Cristina; Giavaresi, Gianluca; Fini, Milena; Dediu, Valentin; Tampieri, Anna; Marcacci, Maurilio

2016-03-01

The fascinating prospect to direct tissue regeneration by magnetic activation has been recently explored. In this study we investigate the possibility to boost bone regeneration in an experimental defect in rabbit femoral condyle by combining static magnetic fields and magnetic biomaterials. NdFeB permanent magnets are implanted close to biomimetic collagen/hydroxyapatite resorbable scaffolds magnetized according to two different protocols . Permanent magnet only or non-magnetic scaffolds are used as controls. Bone tissue regeneration is evaluated at 12 weeks from surgery from a histological, histomorphometric and biomechanical point of view. The reorganization of the magnetized collagen fibers under the effect of the static magnetic field generated by the permanent magnet produces a highly-peculiar bone pattern, with highly-interconnected trabeculae orthogonally oriented with respect to the magnetic field lines. In contrast, only partial defect healing is achieved within the control groups. We ascribe the peculiar bone regeneration to the transfer of micro-environmental information, mediated by collagen fibrils magnetized by magnetic nanoparticles, under the effect of the static magnetic field. These results open new perspectives on the possibility to improve implant fixation and control the morphology and maturity of regenerated bone providing "in site" forces by synergically combining static magnetic fields and biomaterials.

Silicon MEMS bistable electromagnetic vibration energy harvester using double-layer micro-coils

NASA Astrophysics Data System (ADS)

Podder, P.; Constantinou, P.; Mallick, D.; Roy, S.

2015-12-01

This work reports the development of a MEMS bistable electromagnetic vibrational energy harvester (EMVEH) consisting of a silicon-on-insulator (SOI) spiral spring, double layer micro-coils and miniaturized NdFeB magnets. Furthermore, with respect to the spiral silicon spring based VEH, four different square micro-coil topologies with different copper track width and number of turns have been investigated to determine the optimal coil dimensions. The micro-generator with the optimal micro-coil generated 0.68 micro-watt load power over an optimum resistive load at 0.1g acceleration, leading to normalized power density of 3.5 kg.s/m3. At higher accelerations the load power increased, and the vibrating magnet collides with the planar micro-coil producing wider bandwidth. Simulation results show that a substantially wider bandwidth could be achieved in the same device by introducing bistable nonlinearity through a repulsive configuration between the moving and fixed permanent magnets.

Magnetic separation of general solid particles realised by a permanent magnet

PubMed Central

Hisayoshi, K.; Uyeda, C.; Terada, K.

2016-01-01

Most existing solids are categorised as diamagnetic or weak paramagnetic materials. The possibility of magnetic motion has not been intensively considered for these materials. Here, we demonstrate for the first time that ensembles of heterogeneous particles (diamagnetic bismuth, diamond and graphite particles, as well as two paramagnetic olivines) can be dynamically separated into five fractions by the low field produced by neodymium (NdFeB) magnets during short-duration microgravity (μg). This result is in contrast to the generally accepted notion that ordinary solid materials are magnetically inert. The materials of the separated particles are identified by their magnetic susceptibility (χ), which is determined from the translating velocity. The potential of this approach as an analytical technique is comparable to that of chromatography separation because the extraction of new solid phases from a heterogeneous grain ensemble will lead to important discoveries about inorganic materials. The method is applicable for the separation of the precious samples such as lunar soils and/or the Hayabusa particles recovered from the asteroids, because even micron-order grains can be thoroughly separated without sample-loss. PMID:27929081

Magnetic separation of general solid particles realised by a permanent magnet

NASA Astrophysics Data System (ADS)

Hisayoshi, K.; Uyeda, C.; Terada, K.

2016-12-01

Most existing solids are categorised as diamagnetic or weak paramagnetic materials. The possibility of magnetic motion has not been intensively considered for these materials. Here, we demonstrate for the first time that ensembles of heterogeneous particles (diamagnetic bismuth, diamond and graphite particles, as well as two paramagnetic olivines) can be dynamically separated into five fractions by the low field produced by neodymium (NdFeB) magnets during short-duration microgravity (μg). This result is in contrast to the generally accepted notion that ordinary solid materials are magnetically inert. The materials of the separated particles are identified by their magnetic susceptibility (χ), which is determined from the translating velocity. The potential of this approach as an analytical technique is comparable to that of chromatography separation because the extraction of new solid phases from a heterogeneous grain ensemble will lead to important discoveries about inorganic materials. The method is applicable for the separation of the precious samples such as lunar soils and/or the Hayabusa particles recovered from the asteroids, because even micron-order grains can be thoroughly separated without sample-loss.

Magnetic separation of general solid particles realised by a permanent magnet.

PubMed

Hisayoshi, K; Uyeda, C; Terada, K

2016-12-08

Most existing solids are categorised as diamagnetic or weak paramagnetic materials. The possibility of magnetic motion has not been intensively considered for these materials. Here, we demonstrate for the first time that ensembles of heterogeneous particles (diamagnetic bismuth, diamond and graphite particles, as well as two paramagnetic olivines) can be dynamically separated into five fractions by the low field produced by neodymium (NdFeB) magnets during short-duration microgravity (μg). This result is in contrast to the generally accepted notion that ordinary solid materials are magnetically inert. The materials of the separated particles are identified by their magnetic susceptibility (χ), which is determined from the translating velocity. The potential of this approach as an analytical technique is comparable to that of chromatography separation because the extraction of new solid phases from a heterogeneous grain ensemble will lead to important discoveries about inorganic materials. The method is applicable for the separation of the precious samples such as lunar soils and/or the Hayabusa particles recovered from the asteroids, because even micron-order grains can be thoroughly separated without sample-loss.

Direct current force sensing device based on compressive spring, permanent magnet, and coil-wound magnetostrictive/piezoelectric laminate.

PubMed

Leung, Chung Ming; Or, Siu Wing; Ho, S L

2013-12-01

A force sensing device capable of sensing dc (or static) compressive forces is developed based on a NAS106N stainless steel compressive spring, a sintered NdFeB permanent magnet, and a coil-wound Tb(0.3)Dy(0.7)Fe(1.92)/Pb(Zr, Ti)O3 magnetostrictive∕piezoelectric laminate. The dc compressive force sensing in the device is evaluated theoretically and experimentally and is found to originate from a unique force-induced, position-dependent, current-driven dc magnetoelectric effect. The sensitivity of the device can be increased by increasing the spring constant of the compressive spring, the size of the permanent magnet, and/or the driving current for the coil-wound laminate. Devices of low-force (20 N) and high-force (200 N) types, showing high output voltages of 262 and 128 mV peak, respectively, are demonstrated at a low driving current of 100 mA peak by using different combinations of compressive spring and permanent magnet.

Coercivity enhancement of sintered Nd-Fe-B magnets by chemical bath deposition of TbCl{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Shuai, E-mail: gshuai@nimte.ac.cn; Zhang, Xiaofeng; Ding, Guangfei

2014-05-07

The chemical bath deposition (CBD) and the grain boundary diffusion method were combined to diffuse the heavy rare earth for obtain the thick magnets with high coercivity and low heavy rare earth. The jet mill powders were soaked into the alcohol solution of 0.2 wt. % TbCl{sub 3}. A thin layer of TbCl{sub 3} was wrapped to the surface of (PrNd){sub 2}Fe{sub 14}B powder particles. The coercivity of magnet is increased from 11.89 kOe to 14.72 kOe without significant reduction of remanence after grain boundary diffusion in the sintering and the annealing processes. The temperature coefficients of the remanence and themore » coercivity are improved by the substitution of PrNd by Tb in the surface of grains. The highly accelerated temperature/humidity stress test (HAST) results indicate that the CBD magnet has poor corrosion resistance, attributing to the present of Cl atoms in the grain boundaries.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mccall, Scott K.; Kuntz, Joshua D.

A method of making a bulk exchange spring magnet by providing a magnetically soft material, providing a hard magnetic material, and producing a composite of said magnetically soft material and said hard magnetic material to make the bulk exchange spring magnet. The step of producing a composite of magnetically soft material and hard magnetic material is accomplished by electrophoretic deposition of the magnetically soft material and the hard magnetic material to make the bulk exchange spring magnet.

Phase composition and magnetic properties in hot deformed magnets based on Misch-metal

NASA Astrophysics Data System (ADS)

Ma, Q.; Zhang, Z. Y.; Zhang, X. F.; Hu, Z. F.; Liu, Y. L.; Liu, F.; Jv, X. M.; Wang, J.; Li, Y. F.; Zhang, J. X.

2018-04-01

In this paper, the Rare-earth Iron Boron (RE-Fe-B) magnets were fabricated successfully by using the double main phase method through mixing the Neodymium Iron Boron (Nd-Fe-B) powders and Misch-metal Iron Boron (MM-Fe-B) powders with different ratio. Aiming at the nanocrystalline RE2Fe14B magnets prepared by using spark plasma sintering technology, phase structure and magnetic properties were investigated. It is found that the Misch-metal (MM) alloys promote the domain nucleation during the the process of magnetization reversal and then damage the coercivity (Hcj) of isotropic RE2Fe14B magnets, while the Hcj could still remain more than 1114.08 kA/m when the mass proportion of MM (simplified as: "a") is 30%. Curie temperature and phase structure were also researched. Two kinds of mixed-solid-solution (MSS) main phases with different Lanthanum (La) and Cerium (Ce) content were believed to be responsible for the two curie temperature of the RE2Fe14B magnets with "a" ≥20%. This is resulted from the inhomogeneous elemental distribution of RE2Fe14B phase.

The preliminary tests of the superconducting electron cyclotron resonance ion source DECRIS-SC2.

PubMed

Efremov, A; Bekhterev, V; Bogomolov, S; Drobin, V; Loginov, V; Lebedev, A; Yazvitsky, N; Yakovlev, B

2012-02-01

A new compact version of the "liquid He-free" superconducting ECR ion source, to be used as an injector of highly charged heavy ions for the MC-400 cyclotron, is designed and built at the Flerov Laboratory of Nuclear Reactions in collaboration with the Laboratory of High Energy Physics of JINR. The axial magnetic field of the source is created by the superconducting magnet and the NdFeB hexapole is used for the radial plasma confinement. The microwave frequency of 14 GHz is used for ECR plasma heating. During the first tests, the source shows a good enough performance for the production of medium charge state ions. In this paper, we will present the design parameters and the preliminary results with gaseous ions.

A fully superconducting bearing system for flywheel applications

NASA Astrophysics Data System (ADS)

Xu, Ke-xi; Wu, Dong-jie; Jiao, Y. L.; Zheng, M. H.

2016-06-01

A fully superconducting magnetic suspension structure has been designed and constructed for the purpose of superconducting bearing applications in flywheel energy storage systems. A thrust type bearing and two journal type bearings, those that are composed of melt textured high-Tc superconductor YBCO bulks and Nd-Fe-B permanent magnets, are used in the bearing system. The rotor dynamical behaviors, including critical speeds and rotational loss, are studied. Driven by a variable-frequency three-phase induction motor, the rotor shaft attached with a 25 kg flywheel disc can be speeded up to 15 000 rpm without serious resonance occurring. Although the flywheel system runs stably in the supercritical speeds region, very obvious rotational loss is unavoidable. The loss mechanism has been discussed in terms of eddy current loss and hysteresis loss.

Field homogeneity improvement of maglev NdFeB magnetic rails from joints.

PubMed

Li, Y J; Dai, Q; Deng, C Y; Sun, R X; Zheng, J; Chen, Z; Sun, Y; Wang, H; Yuan, Z D; Fang, C; Deng, Z G

2016-01-01

An ideal magnetic rail should provide a homogeneous magnetic field along the longitudinal direction to guarantee the reliable friction-free operation of high temperature superconducting (HTS) maglev vehicles. But in reality, magnetic field inhomogeneity may occur due to lots of reasons; the joint gap is the most direct one. Joint gaps inevitably exist between adjacent segments and influence the longitudinal magnetic field homogeneity above the rail since any magnetic rails are consisting of many permanent magnet segments. To improve the running performance of maglev systems, two new rail joints are proposed based on the normal rail joint, which are named as mitered rail joint and overlapped rail joint. It is found that the overlapped rail joint has a better effect to provide a competitive homogeneous magnetic field. And the further structure optimization has been done to ensure maglev vehicle operation as stable as possible when passing through those joint gaps. The results show that the overlapped rail joint with optimal parameters can significantly reduce the magnetic field inhomogeneity comparing with the other two rail joints. In addition, an appropriate gap was suggested when balancing the thermal expansion of magnets and homogenous magnetic field, which is considered valuable references for the future design of the magnetic rails.

Multi-scale characterization by FIB-SEM/TEM/3DAP.

PubMed

Ohkubo, T; Sepehri-Amin, H; Sasaki, T T; Hono, K

2014-11-01

In order to improve properties of functional materials, it is important to understand the relation between the structure and the properties since the structure has large effect to the properties. This can be done by using multi-scale microstructure analysis from macro-scale to nano and atomic scale. Scanning electron microscope (SEM) equipped with focused ion beam (FIB), transmission electron microscope (TEM) and 3D atom probe (3DAP) are complementary analysis tools making it possible to know the structure and the chemistry from micron to atomic resolution. SEM gives us overall microstructural and chemical information by various kinds of detectors such as secondary electron, backscattered electron, EDS and EBSD detectors. Also, it is possible to analyze 3D structure and chemistry via FIB serial sectioning. In addition, using TEM we can focus on desired region to get more complementary information from HRTEM/STEM/Lorentz images, SAED/NBD patterns and EDS/EELS to see the detail micro or nano-structure and chemistry. Especially, combination of probe Cs corrector and split EDS detectors with large detector size enable us to analyze the atomic scale elemental distribution. Furthermore, if the specimen has a complicated 3D nanostructure, or we need to analyze light elements such as hydrogen, lithium or boron, 3DAP can be used as the only technique which can visualize and analyze distribution of all constituent atoms of our materials within a few hundreds nm area. Hence, site-specific sample preparation using FIB/SEM is necessary to get desired information from region of interest. Therefore, this complementary analysis combination works very well to understand the detail of materials.In this presentation, we will show the analysis results obtained from some of functional materials by Carl Zeiss CrossBeam 1540EsB FIB/SEM, FEI Tecnai G(2) F30, Titan G2 80-200 TEMs and locally build laser assisted 3DAP. As the one of the example, result of multi-scale characterization for ultra-fine grain Nd-Fe-B permanent magnet will be shown [1]. In order to improve the magnetic properties, especially to increase the coercivity (resistance against magnetization reversal) of the magnet, decreasing the grain size and isolating each grain by non-ferromagnetic grain boundary phase are quite important since the nucleation of magnetic reversal from grain boundary phase can be suppressed and pinning force of magnetic domain wall at the grain boundary phase can be strengthened. Therefore, micro and nano structure and chemistry analysis can shed a light do grain boundary engineering.Figure 1(a,b) shows SEM BSE images of ultrafine grain Nd-Fe-B sintered magnet and the reconstructed 3D tomography of Nd-rich phases obtained by FIB/SEM serial sectioning. This data can provide us information about the distribution of Nd-rich phase and its volume fraction. Moreover, the HRTEM image from the grain boundary phase, the 3DAP maps and the concentration depth profiles are shown in Fig. 1(c,d,e). This magnet shows high coercivity (1517kA/m), and by comparing these results with the microstructures of low coercivity specimen, importance of grain boundary formation was confirmed and it gives us hint to improve the coercivity further. We will show the detail and results from other materials.jmicro;63/suppl_1/i6/DFU046F1F1DFU046F1Fig. 1.(a) SEM BSE images of ultrafine grain Nd-Fe-B sintered magnet. (b) 3D FIB/SEM tomography of Nd-rich phases. (c) HRTEM image from the grain boundary phase. (d) 3DAP maps of Nd, Cu and Al. (e) Concentration depth profiles for Fe, Nd+Pr, B, Co, Cu and Al, determined from the selected box in (d)[1]. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Investigation of Anisotropic Bonded Magnets in Permanent Magnet Machine Applications

NASA Astrophysics Data System (ADS)

Khazdozian, H. A.; McCall, S. K.; Kramer, M. J.; Paranthaman, M. P.; Nlebedim, I. C.

Rare earth elements (REE) provide the high energy product necessary for permanent magnets, such as sintered Nd2Fe14B, in many applications like wind energy generators. However, REEs are considered critical materials due to risk in their supply. To reduce the use of critical materials in permanent magnet machines, the performance of anisotropic bonded NdFeB magnets, aligned under varying magnetic field strength, was simulated using 3D finite element analysis in a 3MW direct-drive permanent magnet generator (DDPMG), with sintered N42 magnets used as a baseline for comparison. For direct substitution of the anisotropic bonded magnets, approximately 85% of the efficiency of the baseline model was achieved, irrespective of the alignment field. The torque and power generation of the DDPMG was not found to vary significantly with increase in the alignment field. Finally, design changes were studied to allow for the achievement of rated torque and power with the use of anisotropic bonded magnets, demonstrating the potential for reduction of critical materials in permanent magnets for renewable energy applications. This work was supported by the Critical Materials Institute, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office.

Paramagnetic ionic liquids for measurements of density using magnetic levitation.

PubMed

Bwambok, David K; Thuo, Martin M; Atkinson, Manza B J; Mirica, Katherine A; Shapiro, Nathan D; Whitesides, George M

2013-09-03

Paramagnetic ionic liquids (PILs) provide new capabilities to measurements of density using magnetic levitation (MagLev). In a typical measurement, a diamagnetic object of unknown density is placed in a container containing a PIL. The container is placed between two magnets (typically NdFeB, oriented with like poles facing). The density of the diamagnetic object can be determined by measuring its position in the magnetic field along the vertical axis (levitation height, h), either as an absolute value or relative to internal standards of known density. For density measurements by MagLev, PILs have three advantages over solutions of paramagnetic salts in aqueous or organic solutions: (i) negligible vapor pressures; (ii) low melting points; (iii) high thermal stabilities. In addition, the densities, magnetic susceptibilities, glass transition temperatures, thermal decomposition temperatures, viscosities, and hydrophobicities of PILs can be tuned over broad ranges by choosing the cation-anion pair. The low melting points and high thermal stabilities of PILs provide large liquidus windows for density measurements. This paper demonstrates applications and advantages of PILs in density-based analyses using MagLev.

Compaction and sintering behaviors of a Nd-Fe-B permanent magnet alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chin, T.; Hung, M.; Tsai, D.

1988-11-15

Extensive x-ray diffraction (XRD) and magnetic measurements were done on Nd/sub 15/ Fe/sub 77/ B/sub 8/ magnet alloy green compacts after cold isostatic pressing following a pulsed 2-T field (CIP) and die-pressing under a static 1.2-T perpendicular field (DP1) or parallel field (DP2), and on those after sintering. An alignment factor F, through the calculation of the integrated diffraction intensity ratio of the XRD patterns, was adopted as the effectiveness of magnetic alignment. At the green compact state, DP1 has the best alignment while CIP the worst. However, after sintering the alignment factor was such that CIP>DPI>DP2, the same ordermore » as the magnetic properties. Three mechanisms were proposed for the evolution of the alignment factor at different stages of sintering, i.e., that both the appearance of a liquid phase at low temperatures and preferred grain growth at high temperatures enhance F, while recrystallization at intermediate temperatures deteriorates F. CIP results in less-defect green compact, hence less recrystallization, leading to better resultant alignment« less

The feasibility of using magnetic nanoparticles modified as gene vector.

PubMed

Chen, D; Tang, Q; Xue, W; Wang, X

2010-06-01

To evaluate the feasibility of using magnetic nanoparticles (MNPs) as gene vector and the effect of magnetic field on efficiency of transfection. Magnetic nanoparticles were prepared by controlling some chemical reaction parameters through a partially reduction precipitation method with ferric chloride aqueous solution as precursor material. The surface of particles was modified by polyethyleneimine (PEI) agents. The appearance, the size distribution, structure and phase constitute of MNPs were characterized by Transmission electron microscope (TEM), X-ray diffraction (XRD); the potential of absorbing DNA of MNPs was analysed by electrophoresis. Transfection was determined by delivering reporter gene, PGL2-control encoding luciferase, to different cell lines using MNPs-PLL as vector. The effect of magnetic field on the efficiency of transfection was determined using Nd-Fe-B permanent magnet. Foreign gene could be delivered to various cell lines by MNPs-PLL and expressed with high efficiency but the transfection efficiency and time course varied in the different cell lines studied. Magnetic field could enhance the efficiency of transfection by 5-10 fold. MNPs- PLL can be used as a novel non-viral gene vector in vitro, which offers a basis for gene delivery in vivo.

A Review of Permanent Magnet Stirring During Metal Solidification

NASA Astrophysics Data System (ADS)

Zeng, Jie; Chen, Weiqing; Yang, Yindong; Mclean, Alexander

2017-12-01

Rather than using conventional electromagnetic stirring (EMS) with three-phase alternating current, permanent magnet stirring (PMS), based on the use of sintered NdFeB material which has excellent magnetic characteristics, can be employed to generate a magnetic field for the stirring of liquid metal during solidification. Recent experience with steel casting indicates that PMS requires less than 20 pct of the total energy compared with EMS. Despite the excellent magnetic density properties and low power consumption, this relatively new technology has received comparatively little attention by the metal casting community. This paper reviews simulation modeling, experimental studies, and industrial trials of PMS conducted during recent years. With the development of magnetic simulation software, the magnetic field and associated flow patterns generated by PMS have been evaluated. Based on the results obtained from laboratory experiments, the effects of PMS on metal solidification structures and typical defects such as surface pinholes and center cavities are summarized. The significance of findings obtained from trials of PMS within the metals processing sector, including the continuous casting of steel, are discussed with the aim of providing an overview of the relevant parameters that are of importance for further development and industrial application of this innovative technology.

Body motion for powering biomedical devices.

PubMed

Romero, Edwar; Warrington, Robert O; Neuman, Michael R

2009-01-01

Kinetic energy harvesting has been demonstrated as a useful technique for powering portable electronic devices. Body motion can be used to generate energy to power small electronic devices for biomedical applications. These scavengers can recharge batteries, extending their operation lifetime or even replace them. This paper addresses the generation of energy from human activities. An axial flux generator is presented using body motion for powering miniature biomedical devices. This generator presents a gear-shaped planar coil and a multipole NdFeB permanent magnet (PM) ring with an attached eccentric weight. The device generates energy by electromagnetic induction on the planar coil when subject to a changing magnetic flux due to the generator oscillations produced by body motion. A 1.5 cm(3) prototype has generated 3.9 microW of power while walking with the generator placed laterally on the ankle.

Static magnetic field reduced exogenous oligonucleotide uptake by spermatozoa using magnetic nanoparticle gene delivery system

NASA Astrophysics Data System (ADS)

Katebi, Samira; Esmaeili, Abolghasem; Ghaedi, Kamran

2016-03-01

Spermatozoa could introduce exogenous oligonucleotides of interest to the oocyte. The most important reason of low efficiency of sperm mediated gene transfer (SMGT) is low uptake of exogenous DNA by spermatozoa. The aim of this study was to evaluate the effects of static magnetic field on exogenous oligonucleotide uptake of spermatozoa using magnetofection method. Magnetic nanoparticles (MNPs) associated with the labeled oligonucleotides were used to increase the efficiency of exogenous oligonucleotide uptake by rooster spermatozoa. We used high-field/high-gradient magnet (NdFeB) to enhance and accelerate exogenous DNA sedimentation at the spermatozoa surface. Flow cytometry analysis was performed to measure viability and percentage of exogenous oligonucleotide uptake by sperm. Flow cytometry analysis showed a significant increase in exogenous oligonucleotide uptake by rooster spermatozoa (P<0.001) when spermatozoa were incubated in exogenous oligonucleotide solution and MNPs. However, by applying static magnetic field during magnetofection method, a significant decrease in exogenous oligonucleotide uptake was observed (P<0.05). Findings of this study showed that MNPs were effective to increase exogenous oligonucleotide uptake by rooster spermatozoa; however unlike others studies, static magnetic field, was not only ineffective to enhance exogenous oligonucleotide uptake by rooster spermatozoa but also led to reduction in efficiency of magnetic nanoparticles in gene transfer.

Coercivity enhancement of sintered Nd-Fe-B magnets by chemical bath deposition

NASA Astrophysics Data System (ADS)

Zhang, Qiushuang; Guo, Shuai; Yang, Xiao; Zeng, Jiling; Cao, Xuejing; Chen, Renjie; Yan, Aru

2018-05-01

The chemical bath deposition (CBD) method is used to diffuse the heavy rare earth element in order to obtain the high coercivity magnets with low heavy rare earth element. The jet mill powders are soaked in the alcohol suspension of Dy(CH3CHOHCH3)3 (Dy-ipa) so that Nd2Fe14B powder particles are surrounded by Dy-ipa homogeneously. By adding 1.0 wt. % Dy, the coercivity of magnet is increased from 14.47 kOe to 17.55 kOe with slight reduction of remanence after grain boundary diffusion (GBD) in the sintering and annealing processes. The temperature coefficient of coercivity optimizes from -0.629 %/°C to -0.605 %/°C as well as that of remanence improves from -0.108 %/°C to -0.100 %/°C. The CBD method is helpful for thermal stability and alignment either. The relation between the microstructure and the coercivity has been studied systematically.

Automated digital magnetofluidics

NASA Astrophysics Data System (ADS)

Schneider, J.; Garcia, A. A.; Marquez, M.

2008-08-01

Drops can be moved in complex patterns on superhydrophobic surfaces using a reconfigured computer-controlled x-y metrology stage with a high degree of accuracy, flexibility, and reconfigurability. The stage employs a DMC-4030 controller which has a RISC-based, clock multiplying processor with DSP functions, accepting encoder inputs up to 22 MHz, provides servo update rates as high as 32 kHz, and processes commands at rates as fast as 40 milliseconds. A 6.35 mm diameter cylindrical NdFeB magnet is translated by the stage causing water drops to move by the action of induced magnetization of coated iron microspheres that remain in the drop and are attracted to the rare earth magnet through digital magnetofluidics. Water drops are easily moved in complex patterns in automated digital magnetofluidics at an average speed of 2.8 cm/s over a superhydrophobic polyethylene surface created by solvent casting. With additional components, some potential uses for this automated microfluidic system include characterization of superhydrophobic surfaces, water quality analysis, and medical diagnostics.

Influence of experimental methods on crossing in magnetic force-gap hysteresis curve of HTS maglev system

NASA Astrophysics Data System (ADS)

Lu, Yiyun; Qin, Yujie; Dang, Qiaohong; Wang, Jiasu

2010-12-01

The crossing in magnetic levitation force-gap hysteresis curve of melt high-temperature superconductor (HTS) vs. NdFeB permanent magnet (PM) was experimentally studied. One HTS bulk and PM was used in the experiments. Four experimental methods were employed combining of high/low speed of movement of PM with/without heat insulation materials (HIM) enclosed respectively. Experimental results show that crossing of the levitation force-gap curve is related to experimental methods. A crossing occurs in the magnetic force-gap curve while the PM moves approaching to and departing from the sample with high or low speed of movement without HIM enclosed. When the PM is enclosed with HIM during the measurement procedures, there is no crossing in the force-gap curve no matter high speed or low speed of movement of the PM. It was found experimentally that, with the increase of the moving speed of the PM, the maximum magnitude of levitation force of the HTS increases also. The results are interpreted based on Maxwell theories and flux flow-creep models of HTS.

Selective Extraction of Rare Earth Elements from Permanent Magnet Scraps with Membrane Solvent Extraction.

PubMed

Kim, Daejin; Powell, Lawrence E; Delmau, Lætitia H; Peterson, Eric S; Herchenroeder, Jim; Bhave, Ramesh R

2015-08-18

The rare earth elements (REEs) such as neodymium, praseodymium, and dysprosium were successfully recovered from commercial NdFeB magnets and industrial scrap magnets via membrane assisted solvent extraction (MSX). A hollow fiber membrane system was evaluated to extract REEs in a single step with the feed and strip solutions circulating continuously through the MSX system. The effects of several experimental variables on REE extraction such as flow rate, concentration of REEs in the feed solution, membrane configuration, and composition of acids were investigated with the MSX system. A multimembrane module configuration with REEs dissolved in aqueous nitric acid solutions showed high selectivity for REE extraction with no coextraction of non-REEs, whereas the use of aqueous hydrochloric acid solution resulted in coextraction of non-REEs due to the formation of chloroanions of non-REEs. The REE oxides were recovered from the strip solution through precipitation, drying, and annealing steps. The resulting REE oxides were characterized with XRD, SEM-EDX, and ICP-OES, demonstrating that the membrane assisted solvent extraction is capable of selectively recovering pure REEs from the industrial scrap magnets.

The Use of Gadolinium-Carbon Nanostructures to Magnetically Enhance Stem Cell Retention for Cellular Cardiomyoplasty

PubMed Central

Tran, Lesa A.; Hernández-Rivera, Mayra; Berlin, Ari N.; Zheng, Yi; Sampaio, Luiz; Bové, Christina; Cabreira-Hansen, Maria da Graça; Willerson, James T.; Perin, Emerson C.; Wilson, Lon J.

2014-01-01

In this work, the effectiveness of using Gadonanotubes (GNTs) with an external magnetic field to improve retention of transplanted adult mesenchymal stem cells (MSCs) during cellular cardiomyoplasty was evaluated. As a high-performance T1-weighted magnetic resonance imaging (MRI) cell tracking label, the GNTs are gadolinium-loaded carbon nanotube capsules that render MSCs magnetic when internalized. MSCs were internally labeled with either superparamagnetic GNTs or colloidal diamagnetic lutetium (Lu). In vitro cell rolling assays and ex vivo cardiac perfusion experiments qualitatively demonstrated increased magnetic-assisted retention of GNT-labeled MSCs. Subsequent in vivo epicardial cell injections were performed around a 1.3 T NdFeB ring magnet sutured onto the left ventricle of female juvenile pigs (n = 21). Cell dosage, magnet exposure time, and endpoints were varied to evaluate the safety and efficacy of the proposed therapy. Quantification of retained cells in collected tissues by elemental analysis (Gd or Lu) showed that the external magnet helped retain nearly three times more GNT-labeled MSCs than Lu-labeled cells. The sutured magnet was tolerated for up to 168 hours; however, an inflammatory response to the magnet was noted after 48 hours. These proof-of-concept studies support the feasibility and value of using GNTs as a magnetic nanoparticle facilitator to improve cell retention during cellular cardiomyoplasty. PMID:24148239

Non-resonant electromagnetic energy harvester for car-key applications

NASA Astrophysics Data System (ADS)

Li, X.; Hehn, T.; Thewes, M.; Kuehne, I.; Frey, A.; Scholl, G.; Manoli, Y.

2013-12-01

This paper presents a novel non-resonant electromagnetic energy harvester for application in a remote car-key, to extend the lifetime of the battery or even to realize a fully energy autonomous, maintenance-free car-key product. Characteristic for a car-key are low frequency and large amplitude motions during normal daily operation. The basic idea of this non-resonant generator is to use a round flat permanent magnet moving freely in a round flat cavity, which is packaged on both sides by printed circuit boards embedded with multi-layer copper coils. The primary goal of this structure is to easily integrate the energy harvester with the existing electrical circuit module into available commercial car-key designs. The whole size of the energy harvester is comparable to a CR2032 coin battery. To find out the best power-efficient and optimal design, several magnets with different dimensions and magnetizations, and various layouts of copper coils were analysed and built up for prototype testing. Experimental results show that with an axially magnetized NdFeB magnet and copper coils of design variant B a maximum open circuit voltage of 1.1V can be observed.

Sensitivity Enhancement in Magnetic Sensors Based on Ferroelectric-Bimorphs and Multiferroic Composites.

PubMed

Sreenivasulu, Gollapudi; Qu, Peng; Petrov, Vladimir; Qu, Hongwei; Srinivasan, Gopalan

2016-02-20

Multiferroic composites with ferromagnetic and ferroelectric phases have been studied in recent years for use as sensors of AC and DC magnetic fields. Their operation is based on magneto-electric (ME) coupling between the electric and magnetic subsystems and is mediated by mechanical strain. Such sensors for AC magnetic fields require a bias magnetic field to achieve pT-sensitivity. Novel magnetic sensors with a permanent magnet proof mass, either on a ferroelectric bimorph or a ferromagnetic-ferroelectric composite, are discussed. In both types, the interaction between the applied AC magnetic field and remnant magnetization of the magnet results in a mechanical strain and a voltage response in the ferroelectric. Our studies have been performed on sensors with a Nd-Fe-B permanent magnet proof mass on (i) a bimorph of oppositely-poled lead zirconate titanate (PZT) platelets and (ii) a layered multiferroic composite of PZT-Metglas-Ni. The sensors have been characterized in terms of sensitivity and equivalent magnetic noise N. Noise N in both type of sensors is on the order of 200 pT/√Hz at 1 Hz, a factor of 10 improvement compared to multiferroic sensors without a proof mass. When the AC magnetic field is applied at the bending resonance for the bimorph, the measured N ≈ 700 pT/√Hz. We discuss models based on magneto-electro-mechanical coupling at low frequency and bending resonance in the sensors and theoretical estimates of ME voltage coefficients are in very good agreement with the data.

Effects of pulsed electromagnetic field vibration on tooth movement induced by magnetic and mechanical forces: a preliminary study.

PubMed

Darendeliler, M Ali; Zea, A; Shen, G; Zoellner, H

2007-12-01

This study was designed to determine whether or not high-frequency and low-magnitude vibration affects orthodontic tooth movement caused by magnetic or/and mechanical forces. Forty-four 7-week-old Wistar rats were randomly divided into four groups, with each group further divided into experimental and control subgroups. Neodymium-Iron-Boron (Nd-Fe-B) magnets and Sentalloy closed coil springs were placed between maxillary or mandibular first molars and incisors to activate tooth movement. The animals of experimental subgroups were exposed to the vibration induced by pulsed electromagnetic fields (PEMF) whilst the control subgroups were under normal atmosphere. The experiment lasted for 14 days and all of the animals were sacrificed for examination. The changes in the space between the molar and incisor were measured to indicate the amount of tooth movement. The coil springs, either with sham or active magnets, move molar much more than magnets alone, regardless of absence or presence of PEMF (p < 0.001). Under PEMF, the coil spring moved significantly more amount of tooth movement than that of coil-magnet combination (p < 0.01), as did the magnets compared to sham magnets (p < 0.019). Under a non-PEMF scenario, there was no significant difference in tooth movement between coil spring and coil-magnets combination, nor was there difference between magnets and sham magnets. It is suggested that the PEMF-induced vibration may enhance the effect of mechanical and magnetic forces on tooth movement.

A study on the changes in attractive force of magnetic attachments for overdenture.

PubMed

Leem, Han-Wool; Cho, In-Ho; Lee, Jong-Hyuk; Choi, Yu-Sung

2016-02-01

Although magnetic attachment is used frequently for overdenture, it is reported that attractive force can be decreased by abrasion and corrosion. The purpose of this study was to establish the clinical basis about considerations and long term prognosis of overdenture using magnetic attachments by investigating the change in attractive force of magnetic attachment applied to the patients. Among the patients treated with overdenture using magnetic attachments in Dankook University Dental Hospital, attractive force records of 61 magnetic attachments of 20 subjects who re-visited from July 2013 to June 2014 were analyzed. Dental magnet tester (Aichi Micro Intelligent Co., Aichi, Japan) was used for measurement. The magnetic attachments used in this study were Magfit IP-B Flat, Magfit DX400, Magfit DX600 and Magfit DX800 (Aichi Steel Co., Aichi, Japan) filled with Neodymium (NdFeB), a rare-earth magnet. Reduction ratio of attractive force had no significant correlation with conditional variables to which attachments were applied, and was higher when the maintenance period was longer (P<.05, r=.361). Reduction ratio of attractive force was significantly higher in the subject group in which attachments were used over 9 years than within 9 years (P<.05). Furthermore, 16.39% of total magnetic attachments showed detachment of keeper or assembly. Attractive force of magnetic attachment is maintained regardless of conditional variables and reduction ratio increased as the maintenance period became longer. Further study on adhesive material, attachment method and design improvement to prevent detachment of magnetic attachment is needed.

Thermodynamic properties of a hard/soft-magnetic bilayer model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taaev, T. A., E-mail: taaev89@mail.ru; Khizriev, K. Sh.; Murtazaev, A. K.

2016-05-15

A model for describing the thermodynamic properties of a hard/soft-magnetic bilayer is proposed and thoroughly studied using the Monte Carlo method. Temperature dependences of the heat capacity, total magnetization, magnetizations of the hard- and soft-magnetic layers, total magnetic susceptibility, and susceptibilities of the hard- and soft-magnetic layers have been calculated by this method in the framework of the proposed model. The obtained temperature dependences of the heat capacity and magnetic susceptibility display double maxima that result from the two phase transitions that take place in the system. The influence of system dimensions on the thermodynamic properties of the model hasmore » been considered.« less

Method for treating rare earth-transition metal scrap

DOEpatents

Schmidt, Frederick A.; Peterson, David T.; Wheelock, John T.; Jones, Lawrence L.

1992-12-29

Rare earth-transition metal (e.g., iron) scrap (e.g., Nd-Fe-B scrap) is flux (slag) remelted to reduce tramp non-metallic impurities, such as oxygen and nitrogen, and metallic impurities, such as Li, Na, Al, etc., picked up by the scrap from previous fabrication operations. The tramp impurities are reduced to concentrations acceptable for reuse of the treated alloy in the manufacture of end-use articles, such as permanent magnets. The scrap is electroslag or inductoslag melted using a prefused, rare earth fluoride-bearing flux of CaF.sub.2, CaCl.sub.2 or mixtures thereof or the slag resulting from practice of the thermite reduction process to make a rare earth-iron alloy.

Method for treating rare earth-transition metal scrap

DOEpatents

Schmidt, F.A.; Peterson, D.T.; Wheelock, J.T.; Jones, L.L.

1992-12-29

Rare earth-transition metal (e.g., iron) scrap (e.g., Nd-Fe-B scrap) is flux (slag) remelted to reduce tramp non-metallic impurities, such as oxygen and nitrogen, and metallic impurities, such as Li, Na, Al, etc., picked up by the scrap from previous fabrication operations. The tramp impurities are reduced to concentrations acceptable for reuse of the treated alloy in the manufacture of end-use articles, such as permanent magnets. The scrap is electroslag or inductoslag melted using a rare earth fluoride-bearing flux of CaF[sub 2], CaCl[sub 2] or mixtures thereof or the slag resulting from practice of the thermite reduction process to make a rare earth-iron alloy. 3 figs.

Magnetophoretic velocimetry of manganese(II) in a single microdroplet in a flow system under a high gradient magnetic field generated with a superconducting magnet.

PubMed

Suwa, Masayori; Watarai, Hitoshi

2002-10-01

An experimental system for magnetophoretic velocimetry, which could determine the volume magnetic susceptibility of a single particle dispersed in a liquid phase from a magnetophoretic velocity, has been developed. A micrometer-sized high-gradient magnetic field could be generated in a capillary by a pair of iron pole pieces in a superconducting magnet (10 T). The magnetophoretic behavior of a single particle in a capillary flow system was investigated under the inhomogeneous magnetic field. From the magnetophoretic velocity of a polystyrene latex particle dispersed in a MnCl2 aqueous solution, the product of the magnetic flux density and the gradient, B(dB/dx), was determined as a function of the position along the capillary. The maximum value of B(dB/dx) was 4.7 x 10(4) T2 m(-1), which was approximately 100 times higher than that obtained by two Nd-Fe-B permanent magnets (0.4 T). Organic droplets extracting manganese(II) with 2-thenoyltrifluoroacetone and tri-n-octylphosphine oxide from MnCl2 solution were used as test samples. The difference of the volume magnetic susceptibility between the droplet and the medium could be determined from the magnetophoretic velocity. This method allowed us to continuously measure a volume magnetic susceptibility of 10-6 level for a picoliter droplet and to determine manganese(II) in the single droplet at the attomole level.

Comparison of Achievable Magnetic Fields with Superconducting and Cryogenic Permanent Magnet Undulators – A Comprehensive Study of Computed and Measured Values

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moog, E. R.; Dejus, R. J.; Sasaki, S.

2017-01-01

Magnetic modeling was performed to estimate achievable magnetic field strengths of superconducting undulators (SCUs) and to compare them with those of cryogenically cooled permanent magnet undulators (CPMUs). Starting with vacuum (beam stay-clear) gaps of 4.0 and 6.0 mm, realistic allowances for beam chambers (in the SCU case) and beam liners (in the CPMU case) were added. (A 6.0-mm vacuum gap is planned for the upgraded APS). The CPMU magnetic models consider both CPMUs that use NdFeB magnets at ~150 K and PrFeB magnets at 77 K. Parameters of the magnetic models are presented along with fitted coefficients of a Halbach-typemore » expression for the field dependence on the gap-to-period ratio. Field strengths for SCUs are estimated using a scaling law for planar SCUs; an equation for that is given. The SCUs provide higher magnetic fields than the highest-field CPMUs – those using PrFeB at 77 K – for period lengths longer than ~14 mm for NbTi-based SCUs and ~10 mm for Nb3Sn-based SCUs. To show that the model calculations and scaling law results are realistic, they are compared to CPMUs that have been built and NbTi-based SCUs that have been built. Brightness tuning curves of CPMUs (PrFeB) and SCUs (NbTi) for the upgraded APS lattice are also provided for realistic period lengths.« less

Influence of bath PH value on microstructure and corrosion resistance of phosphate chemical conversion coating on sintered Nd-Fe-B permanent magnets

NASA Astrophysics Data System (ADS)

Ding, Xia; Xue, Long-fei; Wang, Xiu-chun; Ding, Kai-hong; Cui, Sheng-li; Sun, Yong-cong; Li, Mu-sen

2016-10-01

The effect of bath PH value on formation, microstructure and corrosion resistance of the phosphate chemical conversion (PCC) coatings as well as the effect on the magnetic property of the magnets is investigated in this paper. The results show that the coating mass and thickness increase with the decrease of the bath PH value. Scanning electron microscopy observation demonstrates that the PCC coatings are in a blocky structure with different grain size. Transmission electron microscope and X-ray diffractometer tests reveal the coatings are polycomponent and are mainly composed of neodymium phosphate hydrate and praseodymium phosphate hydrate. The electrochemical analysis and static immersion corrosion test show the corrosion resistance of the PCC coatings prepared at bath PH value of 0.52 is worst. Afterwards the corrosion resistance increases first and then decreases with the increasing of the bath PH values. The magnetic properties of all the samples with PCC treatment are decreased. The biggest loss is occurred when the bath PH value is 0.52. Taken together, the optimum PH range of 1.00-1.50 for the phosphate solution has been determined.

Magnetic force study for the helical afterburner for the European XFEL

NASA Astrophysics Data System (ADS)

Li, Peng; Wei, Tao; Li, Yuhui; Pflueger, Joachim

2017-05-01

At present the SASE3 undulator line at the European XFEL is using a planar undulator producing linear polarized soft Xray radiation only. In order to satisfy the demand for circular polarized radiation a helical undulator system, the so-called afterburner is in construction. It will be operated as a radiator using the pre-bunched beam of the SASE3 undulator system. Among several options for the magnetic structure the Apple-X geometry was chosen. This is a pure permanent magnet undulator using NdFeB material. Four magnet arrays are arranged symmetrically the beam axis. Polarization can be changed by adjusting the phase shift (PS) between the two orthogonal structures. The field strength can be adjusted either by gap adjustment or alternatively by the amplitude shift (AS) scheme. For an engineering design the maximum values of forces and torques on each of the components under worst case operational conditions are important. The superposition principle is used to reduce calculation time. It is found that the maximum forces Fx, Fy and Fz for a 2m long Apple-X undulator are 1.8*104N, 2.4*104N and 2.3*104N, respectively. More results are presented in this paper.

Vibrational characteristics of a superconducting magnetic bearing employed for a prototype polarization modulator

NASA Astrophysics Data System (ADS)

Sakurai, Yuki; Matsumura, Tomotake; Sugai, Hajime; Katayama, Nobuhiko; Ohsaki, Hiroyuki; Terao, Yutaka; Terachi, Yusuke; Kataza, Hirokazu; Utsunomiya, Shin; Yamamoto, Ryo

2017-07-01

We present the vibrational characteristics of a levitating rotor in a superconducting magnetic bearing (SMB) system operating at below 10 K. We develop a polarization modulator that requires a continuously rotating optical element, called half-wave plate (HWP), for a cosmic microwave background polarization experiment. The HWP has to operate at the temperature below 10 K, and thus an SMB provides a smooth rotation of the HWP at the cryogenic temperature of about 10 K with minimal heat dissipation. In order to understand the potential interference to the cosmological observations due to the vibration of the HWP, it is essential to characterize the vibrational properties of the levitating rotor of the SMB. We constructed a prototype model that consists of an SMB with an array of high temperature superconductors, YBCO, and a permanent magnet ring, NdFeB. The rotor position is monitored by a laser displacement gauge, and a cryogenic Hall sensor via the magnetic field. In this presentation, we present the measurement results of the vibration characteristics using our prototype SMB system. We characterize the vibrational properties as the spring constant and the damping, and discuss the projected performance of this technology toward the use in future space missions.

High performance Nd-Fe-B permanent magnets without critical elements

DOE PAGES

Pathak, Arjun K.; Gschneidner, Jr., K. A.; Khan, M.; ...

2016-01-28

Scanning electron microscopy, and magnetization measurements reveal that as cast (Nd 1–xCe x) 2Fe 14B alloys contain significant amounts of α-Fe that can be dramatically reduced by annealing the alloys at 1000 °C for 3 days. The room temperature intrinsic coercivity, Hci, of (Nd 0.8Ce 0.2) 2.2Fe 14B melt spun ribbons was found to be 11 kOe, which is ~32 to ~10% higher in comparison to that of Nd 2Fe 14B (Hci = 8.3 kOe), and (Nd 0.8Ce 0.2) 2.0Fe 14B (Hci = 10 kOe), respectively. The substitution of Co for Fe in (Nd 0.8Ce 0.2) 2Fe 14–zCo zB significantlymore » increases both TC and the maximum energy product, (BH)max. Our study shows that both Co-containing and Co-free Ce-substituted Nd 2Fe 14B alloys have excellent magnetic properties at room temperature and above. As a result, the experimental results also demonstrate the potential of Nd-Ce-Fe-TM-B based alloys as alternative to expensive Dy-containing high performance rare earth magnets.« less

Separation of mixed waste plastics via magnetic levitation.

PubMed

Zhao, Peng; Xie, Jun; Gu, Fu; Sharmin, Nusrat; Hall, Philip; Fu, Jianzhong

2018-06-01

Separation becomes a bottleneck of dealing with the enormous stream of waste plastics, as most of the extant methods can only handle binary mixtures. In this paper, a novel method that based on magnetic levitation was proposed for separating multiple mixed plastics. Six types of plastics, i.e., polypropylene (PP), acrylonitrile butadiene styrene (ABS), polyamide 6 (PA6), polycarbonate (PC), polyethylene terephthalate (PET), and polytetrafluoroethylene (PTFE), were used to simulate the mixed waste plastics. The samples were mixed and immersed into paramagnetic medium that placed into a magnetic levitation configuration with two identical NdFeB magnets with like-poles facing each other, and Fourier transform infrared (FTIR) spectroscopy was employed to verify the separation outputs. Unlike any conventional separation methods such as froth flotation and hydrocyclone, this method is not limited by particle sizes, as mixtures of different size fractions reached their respective equilibrium positions in the initial tests. The two-stage separation tests demonstrated that the plastics can be completely separated with purities reached 100%. The method has the potential to be industrialised into an economically-viable and environmentally-friendly mass production procedure, since quantitative correlations are determined, and the paramagnetic medium can be reused indefinitely. Copyright © 2018 Elsevier Ltd. All rights reserved.

Selective Extraction of Rare Earth Elements from Permanent Magnet Scraps with Membrane Solvent Extraction

DOE PAGES

Kim, Daejin; Powell, Lawrence E.; Delmau, Lætitia H.; ...

2015-06-24

In this paper, the rare earth elements (REEs) such as neodymium, praseodymium, and dysprosium were successfully recovered from commercial NdFeB magnets and industrial scrap magnets via membrane assisted solvent extraction (MSX). A hollow fiber membrane system was evaluated to extract REEs in a single step with the feed and strip solutions circulating continuously through the MSX system. The effects of several experimental variables on REE extraction such as flow rate, concentration of REEs in the feed solution, membrane configuration, and composition of acids were investigated with the MSX system. A multimembrane module configuration with REEs dissolved in aqueous nitric acidmore » solutions showed high selectivity for REE extraction with no coextraction of non-REEs, whereas the use of aqueous hydrochloric acid solution resulted in coextraction of non-REEs due to the formation of chloroanions of non-REEs. The REE oxides were recovered from the strip solution through precipitation, drying, and annealing steps. Finally, the resulting REE oxides were characterized with XRD, SEM-EDX, and ICP-OES, demonstrating that the membrane assisted solvent extraction is capable of selectively recovering pure REEs from the industrial scrap magnets.« less

Helium temperature measurements in a hot filament magnetic mirror plasma using high resolution Doppler spectroscopy

NASA Astrophysics Data System (ADS)

Knott, S.; McCarthy, P. J.; Ruth, A. A.

2016-09-01

Langmuir probe and spectroscopic diagnostics are used to routinely measure electron temperature and density over a wide operating range in a reconfigured Double Plasma device at University College Cork, Ireland. The helium plasma, generated through thermionic emission from a negatively biased tungsten filament, is confined by an axisymmetric magnetic mirror configuration using two stacks of NdFeB permanent magnets, each of length 20 cm and diameter 3 cm placed just outside the 15 mm water cooling jacket enclosing a cylindrical vacuum vessel of internal diameter 25 cm. Plasma light is analysed using a Fourier Transform-type Bruker spectrometer with a highest achievable resolution of 0.08 cm-1 . In the present work, the conventional assumption of room temperature ions in the analysis of Langmuir probe data from low temperature plasmas is examined critically using Doppler spectroscopy of the 468.6 nm He II line. Results for ion temperatures obtained from spectroscopic data for a variety of engineering parameters (discharge voltage, gas pressure and plasma current) will be presented.

Computational search for rare-earth free hard-magnetic materials

NASA Astrophysics Data System (ADS)

Flores Livas, José A.; Sharma, Sangeeta; Dewhurst, John Kay; Gross, Eberhard; MagMat Team

2015-03-01

It is difficult to over state the importance of hard magnets for human life in modern times; they enter every walk of our life from medical equipments (NMR) to transport (trains, planes, cars, etc) to electronic appliances (for house hold use to computers). All the known hard magnets in use today contain rare-earth elements, extraction of which is expensive and environmentally harmful. Rare-earths are also instrumental in tipping the balance of world economy as most of them are mined in limited specific parts of the world. Hence it would be ideal to have similar characteristics as a hard magnet but without or at least with reduced amount of rare-earths. This is the main goal of our work: search for rare-earth-free magnets. To do so we employ a combination of density functional theory and crystal prediction methods. The quantities which define a hard magnet are magnetic anisotropy energy (MAE) and saturation magnetization (Ms), which are the quantities we maximize in search for an ideal magnet. In my talk I will present details of the computation search algorithm together with some potential newly discovered rare-earth free hard magnet. J.A.F.L. acknowledge financial support from EU's 7th Framework Marie-Curie scholarship program within the ``ExMaMa'' Project (329386).

Use of natural clays as sorbent materials for rare earth ions: Materials characterization and set up of the operative parameters.

PubMed

Iannicelli-Zubiani, Elena Maria; Cristiani, Cinzia; Dotelli, Giovanni; Gallo Stampino, Paola; Pelosato, Renato; Mesto, Ernesto; Schingaro, Emanuela; Lacalamita, Maria

2015-12-01

Two mineral clays of the montmorillonite group were tested as sorbents for the removal of Rare Earths (REs) from liquid solutions. Lanthanum and neodymium model solutions were used to perform uptake tests in order to: (a) verify the clays sorption capability, (b) investigate the sorption mechanisms and (c) optimize the experimental parameters, such as contact time and pH. The desorption was also studied, in order to evaluate the feasibility of REs recovery from waters. The adsorption-desorption procedure with the optimized parameters was also tested on a leaching solution obtained by dissolution of a dismantled NdFeB magnet of a hard-disk. The clays were fully characterized after REs adsorption and desorption by means of X-ray powder diffraction (XRPD) and X-ray photoelectron spectroscopy (XPS); the liquid phase was characterized via Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analyses. The experimental results show that both clays are able to capture and release La and Nd ions, with an ion exchange mechanism. The best total efficiency (capture ≈ 50%, release ≈ 70%) is obtained when the uptake and release processes are performed at pH=5 and pH=1 respectively; in real leached scrap solutions, the uptake is around 40% but release efficiency is strongly decreased passing from a mono-ion system to a real system (from 80% to 5%). Furthermore, a strong matrix effect is found, with the matrix largely affecting both the uptake and the release of neodymium. Copyright © 2015 Elsevier Ltd. All rights reserved.

ATLAS 10 GHz ECR ions source upgrade project.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moehs, D. P.; Pardo, R. C.; Vondrasek, R.

1999-08-10

A major upgrade of the first ATLAS 10 GHz ECR ion source, which began operations in 1987, is in the planning and procurement phase. The new design will convert the old two-stage source into a single-stage source with an electron donor disk and high gradient magnetic field that preserves radial access for solid material feeds and pumping of the plasma chamber. The new magnetic field profile allows for the possibility of a second ECR zone at a frequency of 14 GHz. An open hexapole configuration, using a high energy-product Nd-Fe-B magnet material, having an inner diameter of 8.8 cm andmore » pole gaps of 2.4 cm has been adopted. Models indicate that the field strengths at the chamber wall, 4 cm in radius, will be 9.3 kG along the magnet poles and 5.6 kG along the pole gaps. The individual magnet bars will be housed in austenitic stainless steel allowing the magnet housing within the aluminum plasma chamber to be used as a water channel for direct cooling of the magnets. Eight solenoid coils from the existing ECR will be enclosed in an iron yoke to produce the axial mirror. Based on a current of 500 A, the final model predicts a minimum B field of 3 kG with injection and extraction mirror ratios of 4.4 and 2.9 respectively.« less

Construction of CHESS compact undulator magnets at Kyma

NASA Astrophysics Data System (ADS)

Temnykh, Alexander B.; Lyndaker, Aaron; Kokole, Mirko; Milharcic, Tadej; Pockar, Jure; Geometrante, Raffaella

2015-05-01

In 2014 KYMA S.r.l. has built two CHESS Compact Undulator (CCU) magnets that are at present installed and successfully operate at the Cornell Electron Storage Ring. This type of undulator was developed for upgrade of Cornell High Energy Synchrotron Source beam-lines, but it can be used elsewhere as well. CCU magnets are compact, lightweight, cost efficient and in-vacuum compatible. They are linearly polarized undulators and have a fixed gap. Magnetic field tuning is achieved by phasing (shifting) top magnetic array relative bottom. Two CCUs constructed by KYMA S.r.l. have 28.4 mm period, 6.5 mm gap, 0.93 T peak field. Magnetic structure is of PPM type, made with NdFeB (40UH grade) permanent magnet material. Transitioning from the laboratory to industrial environment for a novel design required additional evaluation, design adjusting and extensive testing. Particular attention was given to the soldering technique used for fastening of the magnetic blocks to holders. This technique had thus far never been used before for undulator magnet construction by industry. The evaluation included tests of different types of soldering paste, measurements of strength of solder and determining the deformations of the soldered magnet and holder under simulated loading forces. This paper focuses on critical features of the CCU design, results of the soldering technique testing and the data regarding permanent magnets magnetization change due to soldering. In addition it deals with optimization-assisted assembly and the performance of the assembled devices and assesses some of the results of the CCU magnets operation at CESR.

Sensitivity Enhancement in Magnetic Sensors Based on Ferroelectric-Bimorphs and Multiferroic Composites

PubMed Central

Sreenivasulu, Gollapudi; Qu, Peng; Petrov, Vladimir; Qu, Hongwei; Srinivasan, Gopalan

2016-01-01

Multiferroic composites with ferromagnetic and ferroelectric phases have been studied in recent years for use as sensors of AC and DC magnetic fields. Their operation is based on magneto-electric (ME) coupling between the electric and magnetic subsystems and is mediated by mechanical strain. Such sensors for AC magnetic fields require a bias magnetic field to achieve pT-sensitivity. Novel magnetic sensors with a permanent magnet proof mass, either on a ferroelectric bimorph or a ferromagnetic-ferroelectric composite, are discussed. In both types, the interaction between the applied AC magnetic field and remnant magnetization of the magnet results in a mechanical strain and a voltage response in the ferroelectric. Our studies have been performed on sensors with a Nd-Fe-B permanent magnet proof mass on (i) a bimorph of oppositely-poled lead zirconate titanate (PZT) platelets and (ii) a layered multiferroic composite of PZT-Metglas-Ni. The sensors have been characterized in terms of sensitivity and equivalent magnetic noise N. Noise N in both type of sensors is on the order of 200 pT/√Hz at 1 Hz, a factor of 10 improvement compared to multiferroic sensors without a proof mass. When the AC magnetic field is applied at the bending resonance for the bimorph, the measured N ≈ 700 pT/√Hz. We discuss models based on magneto-electro-mechanical coupling at low frequency and bending resonance in the sensors and theoretical estimates of ME voltage coefficients are in very good agreement with the data. PMID:26907290

Experiments in a real scale maglev vehicle prototype

NASA Astrophysics Data System (ADS)

Sotelo, G. G.; Dias, D. H. N.; Machado, O. J.; David, E. D.; de Andrade, R., Jr.; Stephan, R. M.; Costa, G. C.

2010-06-01

A Brazilian real scale magnetically levitated transport system prototype is under development at the Federal University of Rio de Janeiro. To test this system a 180 m long line has been projected and it will be concluded by the end of 2010. A superconducting linear bearing (SLB) is used to replace the wheels of a conventional train. High temperature superconductor bulks placed inside cryostats attached to the vehicle and a magnetic rail composes the SLB. To choose the magnetic rail for the test line three different rails, selected in a previous simulation work, were built and tested. They are composed by Nd-Fe-B and steel, arranged in a flux concentrator topology. The magnetic flux density for those magnetic rails was mapped. Also, the levitation force between those rails and the superconductor cryostat, for several cooling gaps, were measured to select the best rail geometry to be used in the real scale line. The SLB allows building a light vehicle with distributed load, silent and high energy efficient. The proposed vehicle is composed of four modules with just 1.5 m of length each one and it can transport up to 24 passengers. The test line having two curves with 45 m radius and a 15% acclivity ramp is also presented.

Permanent magnetic properties of NdFe12Nx sputtered films epitaxially grown on V buffer layer

NASA Astrophysics Data System (ADS)

Sato, T.; Ohsuna, T.; Yano, M.; Kato, A.; Kaneko, Y.

2017-08-01

To clarify the magnetic properties of the NdFe12Nx compound, which shows promise as a high-performance permanent magnet material, NdFe12Nx epitaxial films fabricated by using a V underlayer on MgO (100) single-crystalline substrates were investigated. Nd-Fe films deposited on a V underlayer consist of NdFe12 grains, which have a c-axis orientation perpendicular to the film plane, as well as α-Fe and Nd2Fe17 phases. In the Nd-Fe-N film obtained by subsequent nitridation of the Nd-Fe film, NdFe12Nx grains grew as the dominant phase, and the volume fractions of α-Fe phases dropped below 5%. A Nd-Fe-N film with a thickness of 50 nm exhibits a saturation magnetization (Ms) of 1.7 T, an anisotropy field (HA) of ˜60 kOe, a magnetocrystalline anisotropy energy (K1) of ˜4.1 MJ/m3, and a coercivity (Hc) of 1.7 kOe. The Hc of a Nd-Fe-N film with a thickness of 25 nm is 4.3 kOe. These results indicate that NdFe12Nx compounds have a superior Ms compared to Nd-Fe-B magnets, while the enhancement in Hc is indispensable.

Magnetohydrodynamic and Paramagnetic Phenomena in Electrochemistry with Diamagnetic and Ferromagnetic Millielectrodes

NASA Technical Reports Server (NTRS)

Leventis, Nicholas; Dass, Amala

2004-01-01

There are three kinds of body forces operating in electrolytic solutions in the magnetic field: the magnetohydrodynamic force F(sub B) (=i x B), the F(sub delB) force (approximately B(raised dot)gradB) and the F(sub delC) force (approximately |B|(sup 2)gradC). These three forces manifest themselves differently, depending on the experimental conditions. Thus, diamagnetic disc millielectrodes (e.g., Au) with their plane parallel to the flux density of the homogeneous magnetic field of an electromagnet yield convective behavior analogous to that observed with rotating electrodes; that response is controlled by F(sub B). The same electrodes placed in the inhomogeneous field of a strong permanent magnet yield also convective behavior that is controlled by both F(sub B) and F(sub delB). Finally, similarly sized millielectrodes made of permanent magnets (e.g., Au-coated Nd-Fe-B discs) yield diffusion-controlled behavior at conditions where a gold disc electrode shows behavior dominated by density gradient driven natural convection; in this case the predominant forces are both F(sub delB) and F(sub delC). Under open circuit conditions, ferromagnetic (i.e., magnetizable) millielectrodes (Co, Fe, Ni) dipped in corrosive solutions and placed in homogeneous magnetic fields yield mass-transfer phenomena that seem to be controlled by magnetophoresis.

Tactile sensor of hardness recognition based on magnetic anomaly detection

NASA Astrophysics Data System (ADS)

Xue, Lingyun; Zhang, Dongfang; Chen, Qingguang; Rao, Huanle; Xu, Ping

2018-03-01

Hardness, as one kind of tactile sensing, plays an important role in the field of intelligent robot application such as gripping, agricultural harvesting, prosthetic hand and so on. Recently, with the rapid development of magnetic field sensing technology with high performance, a number of magnetic sensors have been developed for intelligent application. The tunnel Magnetoresistance(TMR) based on magnetoresistance principal works as the sensitive element to detect the magnetic field and it has proven its excellent ability of weak magnetic detection. In the paper, a new method based on magnetic anomaly detection was proposed to detect the hardness in the tactile way. The sensor is composed of elastic body, ferrous probe, TMR element, permanent magnet. When the elastic body embedded with ferrous probe touches the object under the certain size of force, deformation of elastic body will produce. Correspondingly, the ferrous probe will be forced to displace and the background magnetic field will be distorted. The distorted magnetic field was detected by TMR elements and the output signal at different time can be sampled. The slope of magnetic signal with the sampling time is different for object with different hardness. The result indicated that the magnetic anomaly sensor can recognize the hardness rapidly within 150ms after the tactile moment. The hardness sensor based on magnetic anomaly detection principal proposed in the paper has the advantages of simple structure, low cost, rapid response and it has shown great application potential in the field of intelligent robot.

A study on the changes in attractive force of magnetic attachments for overdenture

PubMed Central

Lee, Jong-Hyuk; Choi, Yu-Sung

2016-01-01

PURPOSE Although magnetic attachment is used frequently for overdenture, it is reported that attractive force can be decreased by abrasion and corrosion. The purpose of this study was to establish the clinical basis about considerations and long term prognosis of overdenture using magnetic attachments by investigating the change in attractive force of magnetic attachment applied to the patients. MATERIALS AND METHODS Among the patients treated with overdenture using magnetic attachments in Dankook University Dental Hospital, attractive force records of 61 magnetic attachments of 20 subjects who re-visited from July 2013 to June 2014 were analyzed. Dental magnet tester (Aichi Micro Intelligent Co., Aichi, Japan) was used for measurement. The magnetic attachments used in this study were Magfit IP-B Flat, Magfit DX400, Magfit DX600 and Magfit DX800 (Aichi Steel Co., Aichi, Japan) filled with Neodymium (NdFeB), a rare-earth magnet. RESULTS Reduction ratio of attractive force had no significant correlation with conditional variables to which attachments were applied, and was higher when the maintenance period was longer (P<.05, r=.361). Reduction ratio of attractive force was significantly higher in the subject group in which attachments were used over 9 years than within 9 years (P<.05). Furthermore, 16.39% of total magnetic attachments showed detachment of keeper or assembly. CONCLUSION Attractive force of magnetic attachment is maintained regardless of conditional variables and reduction ratio increased as the maintenance period became longer. Further study on adhesive material, attachment method and design improvement to prevent detachment of magnetic attachment is needed. PMID:26949482

Magnetocaloric effect: permanent magnet array for generation of high magnetic fields

NASA Astrophysics Data System (ADS)

Lee, Seong-Jae; Kenkel, John; Jiles, David

2002-03-01

The magnetocaloric effect (MCE), the heating or cooling of magnetic materials in a magnetic field, is unusually large in the Gd_5(Si_xGe_1-x)4 alloy system. Normally the maximum in the MCE occurs at the Curie temperature (Tc) because the spin entropy change is a maximum. By suitable selection of the composition of this alloy system the Curie temperature can be changed over the range 25 K for x = 0 to 340 K for x =1, and the composition range around x = 0.5 exhibits the largest magnetocaloric effect. In order to increase the amount of heat exchanged the change in applied magnetic field should be as large as possible, and in this research values above 1.5 Tesla are suggested. We have studied a permanent magnet array based on NdFeB, which with a remanent magnetization of only 1.2 Tesla can still generate a magnetic flux density, or magnetic induction B of 2-3 Tesla. In order to generate the high magnetic induction in the absence of a power supply, a modified hollow cylindrical permanent magnet array (HCPMA) has been designed to produce the required strength of magnetic field. Soft magnetic materials including permalloy (NiFe) were used for focusing the magnetic field in the central region. The magnitude of the magnetic flux density at the center was about 2 Tesla. The magnitude and homogeneity of the magnetic field for this design are comparable with the conventional C-shaped yoke and HCPMA. This can be easily adapted for a low power rotary system in which the magnetocaloric material can be exposed alternately to high and low magnetic fields so that it can accept and reject heat from its surroundings.

Low frequency driven electromagnetic energy harvester for self-powered system

NASA Astrophysics Data System (ADS)

Lee, Byung-Chul; Ataur Rahman, Md; Hyun, Seung-Ho; Chung, Gwiy-Sang

2012-12-01

This paper describes a low frequency driven electromagnetic energy harvester (EMEH) for a self-powered system. The EMEH consists of two thin flame resistant (FR-4) springs, NdFeB permanent magnets, and a copper coil. The FR-4 spring was fabricated by a desk computer numerical control (CNC) 3D modeling machine. The two FR-4 springs were used at the top and bottom sides of the device to reduce the stress on the springs and to achieve linear movement of the moving magnet. The finite element method (FEM) is used to investigate the mechanical properties of the system. The proposed EMEH can generate up to 1.52 mW at a resonance frequency of 16 Hz with an acceleration of 0.2 g (g = 9.8 m s-2) and a superior normalized power density (NPD) of 1.07 mW cm-3 g2. The EMEH attached to the engine of an automobile produced 2.4 mW of power, showing the viability of practical applications.

Magnetic properties of hybrid elastomers with magnetically hard fillers: rotation of particles

NASA Astrophysics Data System (ADS)

Stepanov, G. V.; Borin, D. Yu; Bakhtiiarov, A. V.; Storozhenko, P. A.

2017-03-01

Hybrid magnetic elastomers belonging to the family of magnetorheological elastomers contain magnetically hard components and are of the utmost interest for the development of semiactive and active damping devices as well as actuators and sensors. The processes of magnetizing of such elastomers are accompanied by structural rearrangements inside the material. When magnetized, the elastomer gains its own magnetic moment resulting in changes of its magneto-mechanical properties, which remain permanent, even in the absence of external magnetic fields. Influenced by the magnetic field, magnetized particles move inside the matrix forming chain-like structures. In addition, the magnetically hard particles can rotate to align their magnetic moments with the new direction of the external field. Such an elastomer cannot be demagnetized by the application of a reverse field.

Exchange coupling interaction in L10-FePd/α-Fe nanocomposite magnets with large maximum energy products.

PubMed

Sakuma, Noritsugu; Ohshima, Tsubasa; Shoji, Tetsuya; Suzuki, Yoshihito; Sato, Ryota; Wachi, Ayako; Kato, Akira; Kawai, Yoichiro; Manabe, Akira; Teranishi, Toshiharu

2011-04-26

Nanocomposite magnets (NCMs) consisting of hard and soft magnetic phases are expected to be instrumental in overcoming the current theoretical limit of magnet performance. In this study, structural analyses were performed on L1(0)-FePd/α-Fe NCMs with various hard/soft volume fractions, which were formed by annealing Pd/γ-Fe(2)O(3) heterostructured nanoparticles and pure Pd nanoparticles. The sample with a hard/soft volume ratio of 82/18 formed by annealing at 773 K had the largest maximum energy product (BH(max) = 10.3 MGOe). In such a sample, the interface between the hard and soft phases was coherent and the phase sizes were optimized, both of which effectively induced exchange coupling. This exchange coupling was directly observed by visualizing the magnetic interaction between the hard and soft phases using a first-order reversal curve diagram, which is a valuable tool to improve the magnetic properties of NCMs.

Magnetic interactions in anisotropic Nd-Dy-Fe-Co-B/α-Fe multilayer magnets

NASA Astrophysics Data System (ADS)

Dai, Z. M.; Liu, W.; Zhao, X. T.; Han, Z.; Kim, D.; Choi, C. J.; Zhang, Z. D.

2016-10-01

The magnetic properties and the possible interaction mechanisms of anisotropic soft- and hard-magnetic multilayers have been investigated by altering the thickness of different kinds of spacer layers. The metal Ta and the insulating oxides MgO, Cr2O3 have been chosen as spacer layers to investigate the characteristics of the interactions between soft- and hard-magnetic layers in the anisotropic Nd-Dy-Fe-Co-B/α-Fe multilayer system. The dipolar and exchange interaction between hard and soft phases are evaluated with the help of the first order reversal curve method. The onset of the nucleation field and the magnetization reversal by domain wall movement are also evident from the first-order-reversal-curve measurements. Reversible/irreversible distributions reveal the natures of the soft- and hard-magnetic components. Incoherent switching fields are observed and the calculations show the semiquantitative contributions of hard and soft components to the system. An antiferromagnetic spacer layer will weaken the interaction between ferromagnetic layers and the effective interaction length decreases. As a consequence, the dipolar magnetostatic interaction may play an important role in the long-range interaction in anisotropic multilayer magnets.

Magnetic Yoking and Tunable Interactions in FePt-Based Hard/Soft Bilayers

PubMed Central

Gilbert, Dustin A.; Liao, Jung-Wei; Kirby, Brian J.; Winklhofer, Michael; Lai, Chih-Huang; Liu, Kai

2016-01-01

Magnetic interactions in magnetic nanostructures are critical to nanomagnetic and spintronic explorations. Here we demonstrate an extremely sensitive magnetic yoking effect and tunable interactions in FePt based hard/soft bilayers mediated by the soft layer. Below the exchange length, a thin soft layer strongly exchange couples to the perpendicular moments of the hard layer; above the exchange length, just a few nanometers thicker, the soft layer moments turn in-plane and act to yoke the dipolar fields from the adjacent hard layer perpendicular domains. The evolution from exchange to dipolar-dominated interactions is experimentally captured by first-order reversal curves, the ΔM method, and polarized neutron reflectometry, and confirmed by micromagnetic simulations. These findings demonstrate an effective yoking approach to design and control magnetic interactions in wide varieties of magnetic nanostructures and devices. PMID:27604428

A Simple Analytical Model for Magnetization and Coercivity of Hard/Soft Nanocomposite Magnets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Jihoon; Hong, Yang-Ki; Lee, Woncheol

Here, we present a simple analytical model to estimate the magnetization (σ s) and intrinsic coercivity (Hci) of a hard/soft nanocomposite magnet using the mass fraction. Previously proposed models are based on the volume fraction of the hard phase of the composite. But, it is difficult to measure the volume of the hard or soft phase material of a composite. We synthesized Sm 2Co 7/Fe-Co, MnAl/Fe-Co, MnBi/Fe-Co, and BaFe 12O 19/Fe-Co composites for characterization of their σs and Hci. The experimental results are in good agreement with the present model. Therefore, this analytical model can be extended to predict themore » maximum energy product (BH) max of hard/soft composite.« less

A Simple Analytical Model for Magnetization and Coercivity of Hard/Soft Nanocomposite Magnets

DOE PAGES

Park, Jihoon; Hong, Yang-Ki; Lee, Woncheol; ...

2017-07-10

Here, we present a simple analytical model to estimate the magnetization (σ s) and intrinsic coercivity (Hci) of a hard/soft nanocomposite magnet using the mass fraction. Previously proposed models are based on the volume fraction of the hard phase of the composite. But, it is difficult to measure the volume of the hard or soft phase material of a composite. We synthesized Sm 2Co 7/Fe-Co, MnAl/Fe-Co, MnBi/Fe-Co, and BaFe 12O 19/Fe-Co composites for characterization of their σs and Hci. The experimental results are in good agreement with the present model. Therefore, this analytical model can be extended to predict themore » maximum energy product (BH) max of hard/soft composite.« less

Magnetic hard gap due to bound magnetic polarons in the localized regime.

PubMed

Rimal, Gaurab; Tang, Jinke

2017-02-08

We investigate the low temperature electron transport properties of manganese doped lead sulfide films. The system shows variable range hopping at low temperatures that crosses over into an activation regime at even lower temperatures. This crossover is destroyed by an applied magnetic field which suggests a magnetic origin of the hard gap, associated with bound magnetic polarons. Even though the gap forms around the superconducting transition temperature of lead, we do not find evidence of this being due to insulator-superconductor transition. Comparison with undoped PbS films, which do not show the activated transport behavior, suggests that bound magnetic polarons create the hard gap in the system that can be closed by magnetic fields.

A supported liquid membrane system for the selective recovery of rare earth elements from neodymium-based permanent magnets

DOE PAGES

Kim, Daejin; Powell, Lawrence; Delmau, Lætitia H.; ...

2016-04-04

We present that the rare earth elements (REEs) play a vital role in the development of green energy and high-tech industries. In order to meet the fast-growing demand and to ensure sufficient supply of the REEs, it is essential to develop an efficient REE recovery process from post-consumer REE-containing products. In this research effort, we have developed a supported liquid membrane system utilizing polymeric hollow fiber modules to extract REEs from neodymium-based magnets with neutral extractants such as tetraoctyl digylcol amide (TODGA). The effect of process variables such as REE concentration, molar concentration of acid, and membrane area on REEmore » recovery was investigated. We have demonstrated the selective extraction and recovery of REEs such as Nd, Pr, and Dy without co-extraction of non-REEs from permanent NdFeB magnets through the supported liquid membrane system. The extracted REEs were then recovered by precipitation followed by the annealing step to obtain crystalline REE powders in nearly pure form. Finally, the recovered REE oxides were characterized by X-ray diffraction, scanning electron microscope coupled with energy-dispersive X-ray spectroscopy, and inductively coupled plasma–optical emission spectroscopy.« less

Noise reduction in heat-assisted magnetic recording of bit-patterned media by optimizing a high/low Tc bilayer structure

NASA Astrophysics Data System (ADS)

Muthsam, O.; Vogler, C.; Suess, D.

2017-12-01

It is assumed that heat-assisted magnetic recording is the recording technique of the future. For pure hard magnetic grains in high density media with an average diameter of 5 nm and a height of 10 nm, the switching probability is not sufficiently high for the use in bit-patterned media. Using a bilayer structure with 50% hard magnetic material with low Curie temperature and 50% soft magnetic material with high Curie temperature to obtain more than 99.2% switching probability leads to very large jitter. We propose an optimized material composition to reach a switching probability of Pswitch > 99.2% and simultaneously achieve the narrow transition jitter of pure hard magnetic material. Simulations with a continuous laser spot were performed with the atomistic simulation program VAMPIRE for a single cylindrical recording grain with a diameter of 5 nm and a height of 10 nm. Different configurations of soft magnetic material and different amounts of hard and soft magnetic material were tested and discussed. Within our analysis, a composition with 20% soft magnetic and 80% hard magnetic material reaches the best results with a switching probability Pswitch > 99.2%, an off-track jitter parameter σoff,80/20 = 0.46 nm and a down-track jitter parameter σdown,80/20 = 0.49 nm.

Design and Implementation of a Hall Effect Sensor Array Applied to Recycling Hard Drive Magnets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kisner, Roger; Lenarduzzi, Roberto; Killough, Stephen M

Rare earths are an important resource for many electronic components and technologies. Examples abound including Neodymium magnets used in mobile devices and computer hard drives (HDDs), and a variety of renewable energy technologies (e.g., wind turbines). Approximately 21,000 metric tons of Neodymium is processed annually with less than 1% being recycled. An economic system to assist in the recycling of magnet material from post-consumer goods, such as Neodymium Iron Boron magnets commonly found in hard drives is presented. A central component of this recycling measurement system uses an array of 128 Hall Effect sensors arranged in two columns to detectmore » the magnetic flux lines orthogonal to the HDD. Results of using the system to scan planar shaped objects such as hard drives to identify and spatially locate rare-earth magnets for removal and recycling from HDDs are presented. Applications of the sensor array in other identification and localization of magnetic components and assemblies will be presented.« less

Dual levitated coils for antihydrogen production

NASA Astrophysics Data System (ADS)

Wofford, J. D.; Ordonez, C. A.

2013-04-01

Two coaxial superconducting magnetic coils that carry currents in the same direction and that are simultaneously levitated may serve for antihydrogen plasma confinement. The configuration may be suitable for use by a collaboration at the CERN Antiproton Decelerator facility to test fundamental symmetries between the properties of hydrogen and antihydrogen. Nested Penning traps are currently used to confine recombining antihydrogen plasma. Symmetry studies require the production of sufficiently cold antihydrogen. However, plasma drifts within nested Penning traps can increase the kinetic energy of antiprotons that form antihydrogen atoms. Dual levitated coils may serve to confine relatively large, cold, dense non-drifting recombining antihydrogen plasmas. A minimum-B magnetic field that is produced by the coils could provide for atom trapping. A toroidal plasma is confined between the coils. High density plasmas may be possible, by allowing plasma pressure to balance mechanical pressure to keep the coils apart. Progress is reported on theoretical and experimental efforts. The theoretical effort includes the development of a classical trajectory Monte Carlo simulation of confinement. The experimental effort includes levitation of a NdFeB permanent ring magnet, which produces a magnetic field that is qualitatively similar to the field that would be produced by the two coaxial superconducting magnetic coils. Liquid-nitrogen-cooled Bi-2223 high-temperature-superconducting components, with a critical temperature of 108 K, were used to levitate the ring magnet. An issue concerning keeping the plane of the levitated ring horizontal is discussed.

Monte Carlo study of magnetization reversal in the model of a hard/soft magnetic bilayer

NASA Astrophysics Data System (ADS)

Taaev, T. A.; Khizriev, K. Sh.; Murtazaev, A. K.

2017-06-01

Magnetization reversal in the model of a hard/soft magnetic bilayer under the action of an external magnetic field has been investigated by the Monte Carlo method. Calculations have been performed for three systems: (i) the model without a soft-magnetic layer (hard-magnetic layer), (ii) the model with a soft-magnetic layer of thickness 25 atomic layers (predominantly exchange-coupled system), and (iii) with 50 (weak exchange coupling) atomic layers. The effect of a soft-magnetic phase on the magnetization reversal of the magnetic bilayer and on the formation of a 1D spin spring in the magnetic bilayer has been demonstrated. An inf lection that has been detected on the arch of the hysteresis loop only for the system with weak exchange coupling is completely determined by the behavior of the soft layer in the external magnetic field. The critical fields of magnetization reversal decrease with increasing thickness of the soft phase.

Technological and economical analysis of salient pole and permanent magnet synchronous machines designed for wind turbines

NASA Astrophysics Data System (ADS)

Gündoğdu, Tayfun; Kömürgöz, Güven

2012-08-01

Chinese export restrictions already reduced the planning reliability for investments in permanent magnet wind turbines. Today the production of permanent magnets consumes the largest proportion of rare earth elements, with 40% of the rare earth-based magnets used for generators and other electrical machines. The cost and availability of NdFeB magnets will likely determine the production rate of permanent magnet generators. The high volatility of rare earth metals makes it very difficult to quote a price. Prices may also vary from supplier to supplier to an extent of up to 50% for the same size, shape and quantity with a minor difference in quality. The paper presents the analysis and the comparison of salient pole with field winding and of peripheral winding synchronous electrical machines, presenting important advantages. A neodymium alloy magnet rotor structure has been considered and compared to the salient rotor case. The Salient Pole Synchronous Machine and the Permanent Magnet Synchronous Machine were designed so that the plate values remain constant. The Eddy current effect on the windings is taken into account during the design, and the efficiency, output power and the air-gap flux density obtained after the simulation were compared. The analysis results clearly indicate that Salient Pole Synchronous Machine designs would be attractive to wind power companies. Furthermore, the importance of the design of electrical machines and the determination of criteria are emphasized. This paper will be a helpful resource in terms of examination and comparison of the basic structure and magnetic features of the Salient Pole Synchronous Machine and Permanent Magnet Synchronous Machine. Furthermore, an economic analysis of the designed machines was conducted.

Between metamagnetic transition and spin-flip behavior in Ce 122 system of (Ce-Gd)Ru2Si2

NASA Astrophysics Data System (ADS)

Yano, K.; Amakai, Y.; Hara, Y.; Sato, K.; Kita, E.; Takano, H.; Ohta, T.; Murayama, S.

2018-03-01

Aiming at getting some clues to the mechanism of meta-magnetic transition and surprisingly small magnetic moment of Ce along hard axis in CeRu2Si2, the (Ce-Gd)Ru2Si2 system where Ce was substituted by Gd were studied through magnetic properties mainly in Gd-rich regions. At Gd=0, i.e. in CeRu2Si2, the magnetic moment of Ce showed a symptom of saturation in M-H curve under H=90,000 Oe at 2 K and the Ce magnetic moment at 4.2 K can be nearly identical to that at 2 K employing 1/H plot. At Gd-rich content of 0.8, Ce magnetic moment coupled parallel to that of Gd, Ce ↑ Gd ↑ both in easy and hard axis and the extremely smallness of Ce magnetic moment in hard axis disappeared perfectly at x=0.8. Furthermore at Gd=1, GdRu2Si2, Gd magnetic moment caused 2-step like spin-flip in both easy and hard axis.

Magnetic hyperthermia with hard-magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Kashevsky, Bronislav E.; Kashevsky, Sergey B.; Korenkov, Victor S.; Istomin, Yuri P.; Terpinskaya, Tatyana I.; Ulashchik, Vladimir S.

2015-04-01

Recent clinical trials of magnetic hyperthermia have proved, and even hardened, the Ankinson-Brezovich restriction as upon magnetic field conditions applicable to any site of human body. Subject to this restriction, which is harshly violated in numerous laboratory and small animal studies, magnetic hyperthermia can relay on rather moderate heat source, so that optimization of the whole hyperthermia system remains, after all, the basic problem predetermining its clinical perspectives. We present short account of our complex (theoretical, laboratory and small animal) studies to demonstrate that such perspectives should be related with the hyperthermia system based on hard-magnetic (Stoner-Wohlfarth type) nanoparticles and strong low-frequency fields rather than with superparamagnetic (Brownian or Neél) nanoparticles and weak high-frequency fields. This conclusion is backed by an analytical evaluation of the maximum absorption rates possible under the field restriction in the ideal hard-magnetic (Stoner-Wohlarth) and the ideal superparamagnetic (single relaxation time) systems, by theoretical and experimental studies of the dynamic magnetic hysteresis in suspensions of movable hard-magnetic particles, by producing nanoparticles with adjusted coercivity and suspensions of such particles capable of effective energy absorption and intratumoral penetration, and finally, by successful treatment of a mice model tumor under field conditions acceptable for whole human body.

Hybrid polymer composite membrane for an electromagnetic (EM) valveless micropump

NASA Astrophysics Data System (ADS)

Said, Muzalifah Mohd; Yunas, Jumril; Bais, Badariah; Azlan Hamzah, Azrul; Yeop Majlis, Burhanuddin

2017-07-01

In this paper, we report on a hybrid membrane used as an actuator in an electromagnetically driven valveless micropump developed using MEMS processes. The membrane structure consists of the combination of a magnetic polymer composite membrane and an attached bulk permanent magnet which is expected to have a compact structure and a strong magnetic force with maintained membrane flexibility. A soft polymeric material made of polydimethylsiloxane (PDMS) is initially mixed with neodymium magnetic particles (NdFeB) to form a magnetic polymer composite membrane. The membrane is then bonded with the PDMS based microfluidic part, developed using soft lithography process. The developed micropump was tested in terms of the actuator membrane deflection capability and the fluidic flow of the injected fluid sample through the microfluidic channel. The experimental results show that the magnetic composite actuator membrane with an attached bulk permanent magnet is capable of producing a maximum membrane deflection of up to 106 µm. The functionality test of the electromagnetic (EM) actuator for fluid pumping purposes was done by supplying an AC voltage with various amplitudes, signal waves and frequencies. A wide range of sample injection rates from a few µl min-1 to tens of nl min-1 was achieved with a maximum flow rate of 6.6 µl min-1. The injection flow rate of the EM micropump can be controlled by adjusting the voltage amplitude and frequency supplied to the EM coil, to control the membrane deflection in the pump chamber. The designed valveless EM micropump has a very high potential to enhance the drug delivery system capability in biomedical applications.

Anisotropic magnetic switching along hard [1 1 0]-type axes in Er-doped DyFe2/YFe2 thin films

NASA Astrophysics Data System (ADS)

Stenning, G. B. G.; Bowden, G. J.; van der Laan, G.; Figueroa, A. I.; Bencok, P.; Steadman, P.; Hesjedal, T.

2017-10-01

Epitaxial-grown DyFe2/YFe2 multilayer thin films form an ideal model system for the study of magnetic exchange springs. Here the DyFe2 (YFe2) layers are magnetically hard (soft). In the presence of a magnetic field, exchange springs form in the YFe2 layers. Recently, it has been demonstrated that placing small amounts of Er into the centre of the YFe2 springs generates substantial changes in magnetic behavior. In particular, (i) the number of exchange-spring states is increased dramatically, (ii) the resulting domain-wall states cannot simply be described as either Néel or Bloch walls, (iii) the Er and Dy magnetic loops are strikingly different, and (iv) it is possible to engineer Er-induced magnetic exchange-spring collapse. Here, results are presented for Er-doped (1 1 0)-oriented DyFe2 (60 Å/YFe2(240 Å)15 multilayer films, at 100 K in fields of up to 12 T. In particular, we contrast magnetic loops for fields applied along seemingly equivalent hard-magnetic [1 1 0]-type axes. MBE-grown cubic Laves thin films offer the unique feature of allowing to apply the magnetic field along (i) a hard out-of-plane [1 1 0]-axis (the growth axis) and (ii) a similar hard in-plane [ 1 bar 10 ] -axis. Differences are found and attributed to the competition between the crystal-field interaction at the Er site and the long-range dipole-dipole interaction. In particular, the out-of-plane [1 1 0] Er results show the existence of a new magnetic exchange spring state, which would be very difficult to identify without the aid of element-specific technique of X-ray magnetic circular dichroism (XMCD).

Hard-hard coupling assisted anomalous magnetoresistance effect in amine-ended single-molecule magnetic junction

NASA Astrophysics Data System (ADS)

Tang, Y.-H.; Lin, C.-J.; Chiang, K.-R.

2017-06-01

We proposed a single-molecule magnetic junction (SMMJ), composed of a dissociated amine-ended benzene sandwiched between two Co tip-like nanowires. To better simulate the break junction technique for real SMMJs, the first-principles calculation associated with the hard-hard coupling between a amine-linker and Co tip-atom is carried out for SMMJs with mechanical strain and under an external bias. We predict an anomalous magnetoresistance (MR) effect, including strain-induced sign reversal and bias-induced enhancement of the MR value, which is in sharp contrast to the normal MR effect in conventional magnetic tunnel junctions. The underlying mechanism is the interplay between four spin-polarized currents in parallel and anti-parallel magnetic configurations, originated from the pronounced spin-up transmission feature in the parallel case and spiky transmission peaks in other three spin-polarized channels. These intriguing findings may open a new arena in which magnetotransport and hard-hard coupling are closely coupled in SMMJs and can be dually controlled either via mechanical strain or by an external bias.

A strong pinning model for the coercivity of die-upset Pr-Fe-B magnets

NASA Astrophysics Data System (ADS)

Pinkerton, F. E.; fürst, C. D.

1991-04-01

We have measured the temperature dependence of the intrinsic coercivity Hci(T) between 5 and 565 K in a die-upset Pr-Fe-B magnet. Over a very wide temperature range up to 477 K, Hci(T) is in excellent agreement with a model for strong domain-wall pinning by a random array of pinning sites proposed by Gaunt [P. Gaunt, Philos. Mag. B 48, 261 (1983)]. The model includes both the temperature dependence of the intrinsic magnetic properties of the Pr2Fe14B phase and the effects of thermal activation of domain walls over the pinning barrier. The pinning sites are modeled as nonmagnetic planar inhomogeneities at the boundaries between platelet-shaped Pr2Fe14B grains. We develop an expression for the maximum pinning force per site, f, and derive the model prediction that (Hci/γHA)1/2 varies linearly with (T/γ)2/3, where HA and γ are the magnetocrystalline anisotropy field and the domain-wall energy per unit area of the Pr2Fe14B phase, respectively. Significant deviations from the model are observed only at high temperature, suggesting that the strong pinning model is no longer valid very close to the Curie temperature (565 K). The present result agrees with the model fit obtained for a die-upset Nd-Fe-B magnet.

X-ray magnetic circular dichroism and hard X-ray photoelectron spectroscopy of tetragonal Mn72Ge28 epitaxial thin film

NASA Astrophysics Data System (ADS)

Kim, Jinhyeok; Mizuguchi, Masaki; Inami, Nobuhito; Ueno, Tetsuro; Ueda, Shigenori; Takanashi, Koki

2018-04-01

An epitaxially grown Mn72Ge28 film with a tetragonal crystal structure was fabricated. It was clarified that the film had a perpendicular magnetization and a high perpendicular magnetic anisotropy energy of 14.3 Merg/cm3. The electronic structure was investigated by X-ray magnetic circular dichroism and hard X-ray photoelectron spectroscopy. The obtained X-ray magnetic circular dichroism spectrum revealed that the Mn orbital magnetic moment governed the magnetocrystalline anisotropy of the Mn72Ge28 film. A doublet structure was observed for the Mn 2p3/2 peak of hard X-ray photoelectron spectrum, indicating the spin exchange interaction between the 2p core-hole and 3d valence electrons.

Exchange-coupled hard magnetic Fe-Co/CoPt nanocomposite films fabricated by electro-infiltration

NASA Astrophysics Data System (ADS)

Wen, Xiao; Andrew, Jennifer S.; Arnold, David P.

2017-05-01

This paper introduces a potentially scalable electro-infiltration process to produce exchange-coupled hard magnetic nanocomposite thin films. Fe-Co/CoPt nanocomposite films are fabricated by deposition of CoFe2O4 nanoparticles onto Si substrate, followed by electroplating of CoPt. Samples are subsequently annealed under H2 to reduce the CoFe2O4 to magnetically soft Fe-Co and also induce L10 ordering in the CoPt. Resultant films exhibit 0.97 T saturation magnetization, 0.70 T remanent magnetization, 127 kA/m coercivity and 21.8 kJ/m3 maximum energy density. First order reversal curve (FORC) analysis and δM plot are used to prove the exchange coupling between soft and hard magnetic phases.

Performance degradation of ferrofluidic feedthroughs in a mixed irradiation field

NASA Astrophysics Data System (ADS)

Simos, Nikolaos; Fernandes, S.; Mittig, Wolfgang; Pellemoine, Frederique; Avilov, M.; Kostin, M.; Mausner, L.; Ronningen, R.; Schein, M.; Bollen, G.

2017-01-01

Ferrofluidic feedthrough (FF) rotary seals containing either NdFeB or SmCo-type permanent magnets have been considered for use in the target and beam dump systems of the Facility for Rare Isotope Beams (FRIB). To evaluate their performance under irradiation three FF seals were irradiated in a mixed field consisting of fast neutrons, protons and γ-rays to an average absorbed dose of 0.2, 2.0, and 20.0 MGy at the Brookhaven Linac Isotope Producer facility (BLIP). The radiation types and energy profiles mimic those expected at the FRIB facility. Degradation of the operational performance of these devices due to irradiation is expected to be the result of the de-magnetization of the permanent magnets contained within the seal and the changes in the ferrofluid properties. Post-irradiation performance was evaluated by determining the ferrofluidic seal vacuum tightness and torque under static and dynamic conditions. The study revealed that the ferrofluidic feedthrough seal irradiated to a dose of 0.2 MGy maintained its vacuum tightness under both static and rotational condition while the one irradiated to a dose of 2.0 MGy exhibited signs of ferrofluid damage but no overall performance loss. At 20 MGy dose the effects of irradiation on the ferrofluid properties (viscosity and particle agglomeration) were shown to be severe. Furthermore, limited de-magnetization of the annular shaped Nd2Fe14B and Sm2Co17 magnets located within the irradiated FFs was observed for doses of 0.2 MGy and 20 MGy respectively.

Unsupervised data mining in nanoscale x-ray spectro-microscopic study of NdFeB magnet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duan, Xiaoyue; Yang, Feifei; Antono, Erin

Novel developments in X-ray based spectro-microscopic characterization techniques have increased the rate of acquisition of spatially resolved spectroscopic data by several orders of magnitude over what was possible a few years ago. This accelerated data acquisition, with high spatial resolution at nanoscale and sensitivity to subtle differences in chemistry and atomic structure, provides a unique opportunity to investigate hierarchically complex and structurally heterogeneous systems found in functional devices and materials systems. However, handling and analyzing the large volume data generated poses significant challenges. Here we apply an unsupervised data-mining algorithm known as DBSCAN to study a rare-earth element based permanentmore » magnet material, Nd 2Fe 14B. We are able to reduce a large spectro-microscopic dataset of over 300,000 spectra to 3, preserving much of the underlying information. Scientists can easily and quickly analyze in detail three characteristic spectra. Our approach can rapidly provide a concise representation of a large and complex dataset to materials scientists and chemists. For instance, it shows that the surface of common Nd 2Fe 14B magnet is chemically and structurally very different from the bulk, suggesting a possible surface alteration effect possibly due to the corrosion, which could affect the material’s overall properties.« less

Superconducting-electromagnetic hybrid bearing using YBCO bulk blocks for passive axial levitation

NASA Astrophysics Data System (ADS)

Nicolsky, R.; de Andrade, R., Jr.; Ripper, A.; David, D. F. B.; Santisteban, J. A.; Stephan, R. M.; Gawalek, W.; Habisreuther, T.; Strasser, T.

2000-06-01

A superconducting/electromagnetic hybrid bearing has been designed using active radial electromagnetic positioning and a superconducting passive axial levitator. This bearing has been tested for an induction machine with a vertical shaft. The prototype was conceived as a four-pole, two-phase induction machine using specially designed stator windings for delivering torque and radial positioning simultaneously. The radial bearing uses four eddy-current sensors, displaced 90° from each other, for measuring the shaft position and a PID control system for feeding back the currents. The stator windings have been adapted from the ones of a standard induction motor. The superconducting axial bearing has been assembled with commercial NdFeB permanent magnets and a set of seven top-seeded-melt-textured YBCO large-grain cylindrical blocks. The bearing set-up was previously simulated by a finite element method for different permanent magnet-superconductor block configurations. The stiffness of the superconducting axial bearing has been investigated by measuring by a dynamic method the vertical and transversal elastic constants for different field cooling processes. The resulting elastic constants show a linear dependence on the air gap, i.e. the clearance between the permanent magnet assembly and the set of superconducting large-grain blocks, which is dependent on cooling distance.

Unsupervised data mining in nanoscale x-ray spectro-microscopic study of NdFeB magnet

DOE PAGES

Duan, Xiaoyue; Yang, Feifei; Antono, Erin; ...

2016-09-29

Novel developments in X-ray based spectro-microscopic characterization techniques have increased the rate of acquisition of spatially resolved spectroscopic data by several orders of magnitude over what was possible a few years ago. This accelerated data acquisition, with high spatial resolution at nanoscale and sensitivity to subtle differences in chemistry and atomic structure, provides a unique opportunity to investigate hierarchically complex and structurally heterogeneous systems found in functional devices and materials systems. However, handling and analyzing the large volume data generated poses significant challenges. Here we apply an unsupervised data-mining algorithm known as DBSCAN to study a rare-earth element based permanentmore » magnet material, Nd 2Fe 14B. We are able to reduce a large spectro-microscopic dataset of over 300,000 spectra to 3, preserving much of the underlying information. Scientists can easily and quickly analyze in detail three characteristic spectra. Our approach can rapidly provide a concise representation of a large and complex dataset to materials scientists and chemists. For instance, it shows that the surface of common Nd 2Fe 14B magnet is chemically and structurally very different from the bulk, suggesting a possible surface alteration effect possibly due to the corrosion, which could affect the material’s overall properties.« less

Motion stability of the magnetic levitation and suspension with YBa2Cu3O7-x high-Tc superconducting bulks and NdFeB magnets

NASA Astrophysics Data System (ADS)

Li, Jipeng; Zheng, Jun; Huang, Huan; Li, Yanxing; Li, Haitao; Deng, Zigang

2017-10-01

The flux pinning effect of YBa2Cu3O7-x high temperature superconducting (HTS) bulk can achieve self-stable levitation over a permanent magnet or magnet array. Devices based on this phenomenon have been widely developed. However, the self-stable flux pinning effect is not unconditional, under disturbances, for example. To disclose the roots of this amazing self-stable levitation phenomenon in theory, mathematical and mechanical calculations using Lyapunov's stability theorem and the Hurwitz criterion were performed under the conditions of magnetic levitation and suspension of HTS bulk near permanent magnets in Halbach array. It is found that the whole dynamical system, in the case of levitation, has only one equilibrium solution, and the singular point is a stable focus. In the general case of suspension, the system has two singular points: one is a stable focus, and the other is an unstable saddle. With the variation of suspension force, the two first-order singular points mentioned earlier will get closer and closer, and finally degenerate to a high-order singular point, which means the stable region gets smaller and smaller, and finally vanishes. According to the center manifold theorem, the high-order singular point is unstable. With the interaction force varying, the HTS suspension dynamical system undergoes a saddle-node bifurcation. Moreover, a deficient damping can also decrease the stable region. These findings, together with existing experiments, could enlighten the improvement of HTS devices with strong anti-interference ability.

Exploring the Hard and Soft X-ray Emission of Magnetic Cataclysmic Variables

NASA Astrophysics Data System (ADS)

de Martino, D.; Anzolin, G.; Bonnet-Bidaud, J.-M.; Falanga, M.; Matt, G.; Mouchet, M.; Mukai, K.; Masetti, N.

2009-05-01

A non-negligible fraction of galactic hard (>20 keV) X-ray sources were identified as CVs of the magnetic Intermediate Polar type in INTEGRAL, SWIFT and RXTE surveys, that suggests a still hidden but potentially important population of faint hard X-ray sources. Simbol-X has the unique potential to simultaneously characterize their variable and complex soft and hard X-ray emission thus allowing to understand their putative role in galactic populations of X-ray sources.

Method for determining the hardness of strain hardening articles of tungsten-nickel-iron alloy

DOEpatents

Wallace, Steven A.

1984-01-01

The present invention is directed to a rapid nondestructive method for determining the extent of strain hardening in an article of tungsten-nickel-iron alloy. The method comprises saturating the article with a magnetic field from a permanent magnet, measuring the magnetic flux emanating from the article, comparing the measurements of the magnetic flux emanating from the article with measured magnetic fluxes from similarly shaped standards of the alloy with known amounts of strain hardening to determine the hardness.

The observed characteristics of flare energy release. I - Magnetic structure at the energy release site

NASA Technical Reports Server (NTRS)

Machado, Marcos E.; Moore, Ronald L.; Hagyard, Mona J.; Hernandez, Ana M.; Rovira, Marta G.

1988-01-01

It is shown that flaring activity as seen in X-rays usually encompasses two or more interacting magnetic bipoles within an active region. Soft and hard X-ray spatiotemporal evolution is considered as well as the time dependence of the thermal energy content in different magnetic bipoles participating in the flare, the hardness and impulsivity of the hard X-ray emission, and the relationship between the X-ray behavior and the strength and 'observable shear' of the magnetic field. It is found that the basic structure of a flare usually consists of an initiating closed bipole plus one or more adjacent closed bipoles impacted against it.

Preparation of poly (arylene ether nitrile)/NzdFeB composite film with excellent thermal properties and tensile strength

NASA Astrophysics Data System (ADS)

Pan, Hai; Xu, Mingzhen; Liu, Xiaobo

2017-12-01

PEN/NdFeB composite films were prepared by the solution casting method. The thermal properties, fracture morphology and tensile strength of the composite films were tested by DSC, TGA, SEM and electromechanical universal testing machine, respectively. The results reveal that the composite film has good thermal properties and tensile strength. Glass-transition temperature and decomposition temperatures at weight loss of 5% ot the composite films retain at 166±1 C and 462±4 C, respectively. The composite film with 5 wt.% NdFeB has the best tensile strength value for 100.5 MPa. In addition, it was found that the NdFeB filler was well dispersed in PEN matrix by SEM analysis.

Full magnetization process of 3d-4f hard magnetic materials in ultrahigh magnetic fields (an example: RFe11Ti)

NASA Astrophysics Data System (ADS)

Kuz'min, M. D.; Zvezdin, A. K.

1998-03-01

The prospects of using the free-powder high-field magnetization method for a quantitative study of inter-sublattice exchange interaction in 3d-4f hard magnetic materials are analyzed. Such analysis is stimulated by the availability of pulsed magnetic fields ˜103 T generated by implosion. Particular attention is paid to effects due to magnetic anisotropy, essential for these materials. The 3d-4f ferrimagnets where both sublattices contribute positively to the easy-axis anisotropy are shown to be suitable objects of study by the free-powder method, because (i) anomalies in their low-temperature magnetizatization curves are sharp and (ii) anisotropic effects can be allowed for without quantitative knowledge of the anisotropy constants. Moreover, these "good" hard magnetic materials can be brought into metamagnetic regime by diluting the rare earth sublattice with nonmagnetic yttrium; then, regardless of the anisotropy constants, the magnetization curve at low temperatures has just one steplike anomaly, the threshold field being equal exactly to the molecular field acting on the rare earth.

Performance Testing of a High Temperature Linear Alternator for Stirling Convertors

NASA Technical Reports Server (NTRS)

Metscher, Jonathan; Geng, Steven

2016-01-01

The NASA Glenn Research Center has conducted performance testing of a high temperature linear alternator (HTLA) in support of Stirling power convertor development for potential future Radioisotope Power Systems (RPS). The high temperature linear alternator is a modified version of that used in Sunpowers Advanced Stirling Convertor (ASC), and is capable of operation at temperatures up to 200 C. Increasing the temperature capability of the linear alternator could expand the mission space of future Stirling RPS designs. High temperature Neodymium-Iron-Boron (Nd-Fe-B) magnets were selected for the HTLA application, and were fully characterized and tested prior to uses. Higher temperature epoxy for alternator assembly was also selected and tested for thermal stability and strength. A characterization test was performed on the HTLA to measure its performance at various amplitudes, loads, and temperatures. HTLA endurance testing at 200 C is currently underway.

Performance Testing of a High Temperature Linear Alternator for Stirling Convertors

NASA Technical Reports Server (NTRS)

Metscher, Jonathan F.; Geng, Steven M.

2016-01-01

The NASA Glenn Research Center has conducted performance testing of a high temperature linear alternator (HTLA) in support of Stirling power convertor development for potential future Radioisotope Power Systems (RPS). The high temperature linear alternator is a modified version of that used in Sunpower's Advanced Stirling Convertor (ASC), and is capable of operation at temperatures up to 200 deg. Increasing the temperature capability of the linear alternator could expand the mission set of future Stirling RPS designs. High temperature Neodymium-Iron-Boron (Nd-Fe-B) magnets were selected for the HTLA application, and were fully characterized and tested prior to use. Higher temperature epoxy for alternator assembly was also selected and tested for thermal stability and strength. A characterization test was performed on the HTLA to measure its performance at various amplitudes, loads, and temperatures. HTLA endurance testing at 200 deg is currently underway.

TU-H-BRA-05: A System Design for Integration of An Interior MRI and a Linear Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mao, W; Henry Ford Hospital, Detroit, MI; Wang, G

Purpose: MRI is a highly desirable modality to guide radiation therapy but it is difficult to combine a conventional MRI scanner directly with a linear accelerator (linac). An interior MRI (iMRI) concept has been proposed to acquire MRI images within a small field of view only covering targets and immediate surrounding tissues. The objective of this project is to design an interior MRI system to work with a linac using a magnet to provide a field around 0.2T in a cube of 20cm per side, and perform image reconstruction with a slightly inhomogeneous static magnetic fields. Methods: All the resultsmore » are simulated using a commercially available software package, FARADY. In our design, a ring structure holds the iMRI system and also imbeds a linac treatment head. The ring is synchronized to the linac gantry rotation. Half of the ring is made of steel and becomes a magnetic flux return path (yoke) so that a strong magnetic field will be limited inside the iron circuit and fringe fields will be very weak. In order to increase the static magnetic field homogeneity, special steel magnet boots or tips were simulated. Three curved boots were designed based on two-dimensional curves: arc, parabola and hyperbola. Results: Different boot surfaces modify magnetic field distributions differently. With the same pair of neodymium-iron-boron (NdFeB) magnets, the magnetic induction at the centers are 0.217T, 0.201T, 0.204T, and 0.212T for flat, arc, parabola and hyperbola boots, respectively. The hyperbola boots lead to the most homogeneous results, the static magnetic field deviations are within 0.5% in a cube of 20cm, and can be further improved using shimming techniques. Conclusion: This study supports the concept of an iMRI design. Successful development of iMRI will provide crucial information for tumor delineation in radiation therapy.« less

Exchange bias effect in L10-ordered FePt and FeCo-based bilayer structure: effect of increasing applied field

NASA Astrophysics Data System (ADS)

Singh, Sadhana; Kumar, Dileep; Bhagat, Babli; Choudhary, R. J.; Reddy, V. R.; Gupta, Ajay

2018-02-01

The applied magnetic field (H APP) dependence of the exchange bias (EB) is studied in an exchange-coupled thin-film bilayer composed of a hard ferromagnetic FePt layer in the proximity of a soft ferromagnetic FeCo layer. FePt/FeCo structure is deposited in an ultra-high vacuum chamber, where the FePt layer was first annealed at 823 K for 30 min and subsequently cooled to room temperature in the presence of an in-plane magnetic field, H MAX ~ 1.5 kOe to promote L10-ordered hard magnetic phase with magnetic moments aligned in one of the in-plane directions in the FePt layer. In-situ magneto-optical Kerr effect measurements during different stages of bilayer growth and detailed ex-situ superconducting quantum interference device-vibrating sample magnetometer measurements jointly revealed that due to the interplay between exchange coupling at the interface and dipolar energies of the saturated hard FePt layer, a hysteresis loop of FeCo layer shifts along the magnetic field axis. A clear dependence of EB field (H EB) on increasing maximum value of the H APP during the hysteresis loop measurement is understood in terms of the magnetic state of soft and hard magnetic layers, where EB increases with increasing H APP until the hard layer moment remains undisturbed in its remanence state. As soon as the field was sufficient to rotate the spins of the FePt layer, the loop became symmetric with respect to the field axis.

Performance degradation of ferrofluidic feedthroughs in a mixed irradiation field

DOE PAGES

Simos, Nikolaos; Fernandes, S.; Mittig, Wolfgang; ...

2016-10-06

We present ferrofluidic feedthrough (FF) rotary seals containing either NdFeB or SmCo-type permanent magnets that have been considered for use in the target and beam dump systems of the Facility for Rare Isotope Beams (FRIB). To evaluate their performance under irradiation three FF seals were irradiated in a mixed field consisting of fast neutrons, protons and γ-rays to an average absorbed dose of 0.2, 2.0, and 20.0 MGy at the Brookhaven Linac Isotope Producer facility (BLIP). The radiation types and energy profiles mimic those expected at the FRIB facility. Degradation of the operational performance of these devices due to irradiationmore » is expected to be the result of the de-magnetization of the permanent magnets contained within the seal and the changes in the ferrofluid properties. Post-irradiation performance was evaluated by determining the ferrofluidic seal vacuum tightness and torque under static and dynamic conditions. The study revealed that the ferrofluidic feedthrough seal irradiated to a dose of 0.2 MGy maintained its vacuum tightness under both static and rotational condition while the one irradiated to a dose of 2.0 MGy exhibited signs of ferrofluid damage but no overall performance loss. Lastly, at 20 MGy dose the effects of irradiation on the ferrofluid properties (viscosity and particle agglomeration) were shown to be severe. Furthermore, limited de-magnetization of the annular shaped Nd 2Fe 14B and Sm 2Co 17 magnets located within the irradiated FFs was observed for doses of 0.2 MGy and 20 MGy respectively.« less

Magnetocrystalline anisotropy of cementite pseudo single crystal fabricated under a rotating magnetic field

NASA Astrophysics Data System (ADS)

Yamamoto, Sukeyoshi; Terai, Tomoyuki; Fukuda, Takashi; Sato, Kazunori; Kakeshita, Tomoyuki; Horii, Shigeru; Ito, Mikio; Yonemura, Mitsuharu

2018-04-01

We have fabricated a pseudo single crystal of cementite under a rotating magnetic field and investigated its easy and hard axes of magnetization, and determined its magnetocrystalline anisotropy energy. The obtained results are as follows: the hard and easy axes of cementite are the a- and c-axes of the orthorhombic structure with the space group Pnma, respectively. The hard axis observed experimentally was in good agreement with that obtained by an ab initio calculation; however, such consistency was not observed for the easy axis. The magnetocrystalline anisotropy energy was determined as 334 ± 20 kJ/m3 at 5 K.

Time-resolved scanning Kerr microscopy of flux beam formation in hard disk write heads

NASA Astrophysics Data System (ADS)

Valkass, Robert A. J.; Spicer, Timothy M.; Burgos Parra, Erick; Hicken, Robert J.; Bashir, Muhammad A.; Gubbins, Mark A.; Czoschke, Peter J.; Lopusnik, Radek

2016-06-01

To meet growing data storage needs, the density of data stored on hard disk drives must increase. In pursuit of this aim, the magnetodynamics of the hard disk write head must be characterized and understood, particularly the process of "flux beaming." In this study, seven different configurations of perpendicular magnetic recording (PMR) write heads were imaged using time-resolved scanning Kerr microscopy, revealing their detailed dynamic magnetic state during the write process. It was found that the precise position and number of driving coils can significantly alter the formation of flux beams during the write process. These results are applicable to the design and understanding of current PMR and next-generation heat-assisted magnetic recording devices, as well as being relevant to other magnetic devices.

High coercivity microcrystalline Nd-rich Nd-Fe-Co-Al-B bulk magnets prepared by direct copper mold casting

NASA Astrophysics Data System (ADS)

Zhao, L. Z.; Hong, Y.; Fang, X. G.; Qiu, Z. G.; Zhong, X. C.; Gao, X. S.; Liu, Z. W.

2016-06-01

High coercivity Nd25Fe40Co20Al15-xBx (x=7-15) hard magnets were prepared by a simple process of injection casting. Different from many previous investigations on nanocomposite compositions, the magnets in this work contain hard magnetic Nd2(FeCoAl)14B, Nd-rich, and Nd1+ε(FeCo)4B4 phases. The magnetic properties, phase evolution, and microstructure of the as-cast and annealed magnets were investigated. As the boron content increased from 7 to 11 at%, the intrinsic coercivity Hcj of the as-cast magnet increased from 816 to 1140 kA/m. The magnets annealed at 750 °C have shown more regular and smaller grains than the as-cast alloys, especially for the x=11 alloy. The high intrinsic coercivities for the annealed alloys with x=8~11 result from the presence of small-sized grains in the microstructure. The highest Hcj of 1427 kA/m was obtained for the heat treated alloy with x=10. This work provides an alternative approach for preparing fully dense Nd-rich bulk hard magnets with relatively good properties.

Rare-Earth-Free Permanent Magnets for Electrical Vehicle Motors and Wind Turbine Generators: Hexagonal Symmetry Based Materials Systems Mn-Bi and M-type Hexaferrite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Yang-Ki; Haskew, Timothy; Myryasov, Oleg

2014-06-05

The research we conducted focuses on the rare-earth (RE)-free permanent magnet by modeling, simulating, and synthesizing exchange coupled two-phase (hard/soft) RE-free core-shell nano-structured magnet. The RE-free magnets are made of magnetically hard core materials (high anisotropy materials including Mn-Bi-X and M-type hexaferrite) coated by soft shell materials (high magnetization materials including Fe-Co or Co). Therefore, our research helps understand the exchange coupling conditions of the core/shell magnets, interface exchange behavior between core and shell materials, formation mechanism of core/shell structures, stability conditions of core and shell materials, etc.

Micromagnetic simulations with periodic boundary conditions: Hard-soft nanocomposites

DOE PAGES

Wysocki, Aleksander L.; Antropov, Vladimir P.

2016-12-01

Here, we developed a micromagnetic method for modeling magnetic systems with periodic boundary conditions along an arbitrary number of dimensions. The main feature is an adaptation of the Ewald summation technique for evaluation of long-range dipolar interactions. The method was applied to investigate the hysteresis process in hard-soft magnetic nanocomposites with various geometries. The dependence of the results on different micromagnetic parameters was studied. We found that for layered structures with an out-of-plane hard phase easy axis the hysteretic properties are very sensitive to the strength of the interlayer exchange coupling, as long as the spontaneous magnetization for the hardmore » phase is significantly smaller than for the soft phase. The origin of this behavior was discussed. Additionally, we investigated the soft phase size optimizing the energy product of hard-soft nanocomposites.« less

System and method for manipulating domain pinning and reversal in ferromagnetic materials

DOEpatents

Silevitch, Daniel M.; Rosenbaum, Thomas F.; Aeppli, Gabriel

2013-10-15

A method for manipulating domain pinning and reversal in a ferromagnetic material comprises applying an external magnetic field to a uniaxial ferromagnetic material comprising a plurality of magnetic domains, where each domain has an easy axis oriented along a predetermined direction. The external magnetic field is applied transverse to the predetermined direction and at a predetermined temperature. The strength of the magnetic field is varied at the predetermined temperature, thereby isothermally regulating pinning of the domains. A magnetic storage device for controlling domain dynamics includes a magnetic hard disk comprising a uniaxial ferromagnetic material, a magnetic recording head including a first magnet, and a second magnet. The ferromagnetic material includes a plurality of magnetic domains each having an easy axis oriented along a predetermined direction. The second magnet is positioned adjacent to the magnetic hard disk and is configured to apply a magnetic field transverse to the predetermined direction.

Effect of grain alignment distribution on magnetic properties in (MM, Nd)-Fe-B sintered magnets

NASA Astrophysics Data System (ADS)

Yu, Xiaoqiang; Yue, Ming; Zhu, Minggang; Liu, Weiqiang; Li, Yuqing; Xi, Longlong; Li, Jiajie; Zhang, Jiuxing; Li, Wei

2018-03-01

H cj of (MM x Nd1-x )-Fe-B sintered magnets decreases distinctly with x increasing when misch metal (MM) content (x) ranges from 0.3 to 1. Practical application is taken into consideration so that the (MM0.6Nd0.4)-Fe-B components are chosen to analyze the changes in behavior of the magnetic properties. Both Magnet II and Magnet III belong to (MM0.6Nd0.4)-Fe-B sintered magnets, however, it should be noted that Magnet II is prepared by the single alloying method (SAM) and Magnet III is prepared by the double main phase alloy method (DMPAM). Core-shell structures of the magnets prepared by DMPAM can result in the higher H cj and lower knee-point coercivity (H k) compared with that by SAM. Furthermore, for Magnet II, the abnormal grain growth contributes to a better grain alignment and smaller distribution coefficient (σ) defined as the degree of grain alignment, which will enforce a higher tendency of the H cj decreasing and H k increasing. The expression of their normalized coercivity h(σ) is deduced by combining Gao’s starting field model with Kronmüller’s nucleation mechanism. Based on the overall h(σ) ~ σ curve, the best desirable h(σ) value is calculated when σ  =  0.09. Theoretically, for Magnet III, the resultant larger σ should be attributed to the more uniform grain alignment. In addition, the deviations of grain size distributions on the c-plane become more remarkable with more MM concentrates, which can be presented by SEM images. Meanwhile, by means of the pole figures, it is also verified that the grain alignment distribution becomes much more diverse with x increasing. Therefore, it can be predicted whether the grain alignment distribution is significant for H k and H cj of (MM x Nd1-x )-Fe-B sintered magnets (x  ≠  0.6) prepared by SAM/DMPAM or not.

Dysprosium electrodeposition from a hexaalkylguanidinium-based ionic liquid

NASA Astrophysics Data System (ADS)

Berger, Claudia A.; Arkhipova, Maria; Maas, Gerhard; Jacob, Timo

2016-07-01

The rare-earth element dysprosium (Dy) is an important additive that increases the magnetocrystalline anisotropy of neodymium magnets and additionally prevents from demagnetizing at high temperatures. Therefore, it is one of the most important elements for high-tech industries and is mainly used in permanent magnetic applications, for example in electric vehicles, industrial motors and direct-drive wind turbines. In an effort to develop a more efficient electrochemical technique for depositing Dy on Nd-magnets in contrast to commonly used costly physical vapor deposition, we investigated the electrochemical behavior of dysprosium(iii) trifluoromethanesulfonate in a custom-made guanidinium-based room-temperature ionic liquid (RTIL). We first examined the electrodeposition of Dy on an Au(111) model electrode. The investigation was carried out by means of cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS). The initial stages of metal deposition were followed by in situ scanning tunneling microscopy (STM). CV measurements revealed a large cathodic reduction peak, which corresponds to the growth of monoatomic high islands, based on STM images taken during the initial stages of deposition. XPS identified these deposited islands as dysprosium. A similar reduction peak was also observed on an Nd-Fe-B substrate, and positively identified as deposited Dy using XPS. Finally, we varied the concentration of the Dy precursor, electrolyte flow and temperature during Dy deposition and demonstrated that each of these parameters could be used to increase the thickness of the Dy deposit, suggesting that these parameters could be tuned simultaneously in a temperature-controlled flow cell to enhance the thickness of the Dy layer.The rare-earth element dysprosium (Dy) is an important additive that increases the magnetocrystalline anisotropy of neodymium magnets and additionally prevents from demagnetizing at high temperatures. Therefore, it is one of the most important elements for high-tech industries and is mainly used in permanent magnetic applications, for example in electric vehicles, industrial motors and direct-drive wind turbines. In an effort to develop a more efficient electrochemical technique for depositing Dy on Nd-magnets in contrast to commonly used costly physical vapor deposition, we investigated the electrochemical behavior of dysprosium(iii) trifluoromethanesulfonate in a custom-made guanidinium-based room-temperature ionic liquid (RTIL). We first examined the electrodeposition of Dy on an Au(111) model electrode. The investigation was carried out by means of cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS). The initial stages of metal deposition were followed by in situ scanning tunneling microscopy (STM). CV measurements revealed a large cathodic reduction peak, which corresponds to the growth of monoatomic high islands, based on STM images taken during the initial stages of deposition. XPS identified these deposited islands as dysprosium. A similar reduction peak was also observed on an Nd-Fe-B substrate, and positively identified as deposited Dy using XPS. Finally, we varied the concentration of the Dy precursor, electrolyte flow and temperature during Dy deposition and demonstrated that each of these parameters could be used to increase the thickness of the Dy deposit, suggesting that these parameters could be tuned simultaneously in a temperature-controlled flow cell to enhance the thickness of the Dy layer. Electronic supplementary information (ESI) available. See DOI: 10.1039/C6NR01351A

Magnetic field induced random pulse trains of magnetic and acoustic noises in martensitic single-crystal Ni2MnGa

NASA Astrophysics Data System (ADS)

Daróczi, Lajos; Piros, Eszter; Tóth, László Z.; Beke, Dezső L.

2017-07-01

Jerky magnetic and acoustic noises were evoked in a single variant martensitic Ni2MnGa single crystal (produced by uniaxial compression) by application of an external magnetic field along the hard magnetization direction. It is shown that after reaching the detwinning threshold, spontaneous reorientation of martensite variants (twins) leads not only to acoustic emission but magnetic two-directional noises as well. At small magnetic fields, below the above threshold, unidirectional magnetic emission is also observed and attributed to a Barkhausen-type noise due to magnetic domain wall motions during magnetization along the hard direction. After the above first run, in cycles of decreasing and increasing magnetic field, at low-field values, weak, unidirectional Barkhausen noise is detected and attributed to the discontinuous motion of domain walls during magnetization along the easy magnetization direction. The magnetic noise is also measured by constraining the sample in the same initial variant state along the hard direction and, after the unidirectional noise (as obtained also in the first run), a two-directional noise package is developed and it is attributed to domain rotations. From the statistical analysis of the above noises, the critical exponents, characterizing the power-law behavior, are calculated and compared with each other and with the literature data. Time correlations within the magnetic as well as acoustic signals lead to a common scaled power function (with β =-1.25 exponent) for both types of signals.

Nanocomposite Nd-Y-Fe-B-Mo bulk magnets prepared by injection casting technique

NASA Astrophysics Data System (ADS)

Tao, Shan; Ahmad, Zubair; Zhang, Pengyue; Yan, Mi; Zheng, Xiaomei

2017-09-01

The phase composition, magnetic and microstructural properties of Nd2Fe14B/(α-Fe, Fe3B) nanocomposite magnets produced by injection casting technique have been studied. Magnetic hysteresis loop of the Nd7Y6Fe61B22Mo4 permanent magnet demonstrates the coercivity as high as 1289 kA/m. Electron microscopy elucidates a microstructure composed of magnetically soft α-Fe, Fe3B and hard Nd2Fe14B/Y2Fe14B nanograins (20-50 nm) separated by ultra-thin grain boundary layer. The Henkel plot curve of the Nd7Y6Fe61B22Mo4 magnet yields the existence of exchange coupling interactions between soft and hard phases. Macroscopically large size sheet magnet is obtained due to high glass forming ability of the Nd7Y6Fe61B22Mo4 alloy derived from large atomic radius mismatch and negative enthalpy of alloy constituent elements. The high coercivity of the magnet is attributed to the magnetically hard phase increment, nucleation of reverse domains and the presence of thin grain boundary phase. Good magnetic properties such as remanence of 0.51 T, coercivity of 1289 kA/m and maximum energy product of 46.2 kJ/m3 are obtained in directly casted Nd7Y6Fe61B22Mo4 sheet magnets.

Time-resolved scanning Kerr microscopy of flux beam formation in hard disk write heads

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valkass, Robert A. J., E-mail: rajv202@ex.ac.uk; Spicer, Timothy M.; Burgos Parra, Erick

To meet growing data storage needs, the density of data stored on hard disk drives must increase. In pursuit of this aim, the magnetodynamics of the hard disk write head must be characterized and understood, particularly the process of “flux beaming.” In this study, seven different configurations of perpendicular magnetic recording (PMR) write heads were imaged using time-resolved scanning Kerr microscopy, revealing their detailed dynamic magnetic state during the write process. It was found that the precise position and number of driving coils can significantly alter the formation of flux beams during the write process. These results are applicable tomore » the design and understanding of current PMR and next-generation heat-assisted magnetic recording devices, as well as being relevant to other magnetic devices.« less

Integrated CoPtP Permanent Magnets for MEMS Electromagnetic Energy Harvesting Applications

NASA Astrophysics Data System (ADS)

Mallick, Dhiman; Roy, Saibal

2016-10-01

This work reports the development of integrated Co rich CoPtP hard magnetic material for MEMS applications such as Electromagnetic Vibration Energy Harvesting. We report a new method of electrodeposition compared to the conventional DC plating, involving a combination of forward and reverse pulses for optimized deposition of Co rich CoPtP hard magnetic material. This results in significant improvements in the microstructure of the developed films as the pulse reverse plated films are smooth, stress free and uniform. Such improvements in the structural properties are reflected in the hard magnetic properties of the material as well. The intrinsic coercivities of the pulse reverse deposited film are more than 6 times higher for both in-plane and out-of-plane measurement directions and the squareness of the hysteresis loops also improve due to the similar reasons.

Eddy Current, Magnetic Particle and Hardness Testing, Aviation Quality Control (Advanced): 9227.04.

ERIC Educational Resources Information Center

Dade County Public Schools, Miami, FL.

This unit of instruction includes the principles of eddy current, magnetic particle and hardness testing; standards used for analyzing test results; techniques of operating equipment; interpretation of indications; advantages and limitations of these methods of testing; care and calibration of equipment; and safety and work precautions. Motion…

Magnetization dynamics of imprinted non-collinear spin textures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Streubel, Robert, E-mail: r.streubel@ifw-dresden.de; Kopte, Martin; Makarov, Denys, E-mail: d.makarov@ifw-dresden.de

2015-09-14

We study the magnetization dynamics of non-collinear spin textures realized via imprint of the magnetic vortex state in soft permalloy into magnetically hard out-of-plane magnetized Co/Pd nanopatterned heterostructures. Tuning the interlayer exchange coupling between soft- and hard-magnetic subsystems provides means to tailor the magnetic state in the Co/Pd stack from being vortex- to donut-like with different core sizes. While the imprinted vortex spin texture leads to the dynamics similar to the one observed for vortices in permalloy disks, the donut-like state causes the appearance of two gyrofrequencies characteristic of the early and later stages of the magnetization dynamics. The dynamicsmore » are described using the Thiele equation supported by the full scale micromagnetic simulations by taking into account an enlarged core size of the donut states compared to magnetic vortices.« less

Magnetic ionic liquids as non-conventional extraction solvents for the determination of polycyclic aromatic hydrocarbons.

PubMed

Trujillo-Rodríguez, María J; Nacham, Omprakash; Clark, Kevin D; Pino, Verónica; Anderson, Jared L; Ayala, Juan H; Afonso, Ana M

2016-08-31

This work describes the applicability of magnetic ionic liquids (MILs) in the analytical determination of a group of heavy polycyclic aromatic hydrocarbons. Three different MILs, namely, benzyltrioctylammonium bromotrichloroferrate (III) (MIL A), methoxybenzyltrioctylammonium bromotrichloroferrate (III) (MIL B), and 1,12-di(3-benzylbenzimidazolium) dodecane bis[(trifluoromethyl)sulfonyl)]imide bromotrichloroferrate (III) (MIL C), were designed to exhibit hydrophobic properties, and their performance examined in a microextraction method for hydrophobic analytes. The magnet-assisted approach with these MILs was performed in combination with high performance liquid chromatography and fluorescence detection. The study of the extraction performance showed that MIL A was the most suitable solvent for the extraction of polycyclic aromatic hydrocarbons and under optimum conditions the fast extraction step required ∼20 μL of MIL A for 10 mL of aqueous sample, 24 mmol L(-1) NaOH, high ionic strength content of NaCl (25% (w/v)), 500 μL of acetone as dispersive solvent, and 5 min of vortex. The desorption step required the aid of an external magnetic field with a strong NdFeB magnet (the separation requires few seconds), two back-extraction steps for polycyclic aromatic hydrocarbons retained in the MIL droplet with n-hexane, evaporation and reconstitution with acetonitrile. The overall method presented limits of detection down to 5 ng L(-1), relative recoveries ranging from 91.5 to 119%, and inter-day reproducibility values (expressed as relative standard derivation) lower than 16.4% for a spiked level of 0.4 μg L(-1) (n = 9). The method was also applied for the analysis of real samples, including tap water, wastewater, and tea infusion. Copyright © 2016 Elsevier B.V. All rights reserved.

The magnetization process: Hysteresis

NASA Technical Reports Server (NTRS)

Balsamel, Richard

1990-01-01

The magnetization process, hysteresis (the difference in the path of magnetization for an increasing and decreasing magnetic field), hysteresis loops, and hard magnetic materials are discussed. The fabrication of classroom projects for demonstrating hysteresis and the hysteresis of common magnetic materials is described in detail.

Superconducting Magnet Power Supply and Hard-Wired Quench Protection at Jefferson Lab for 12 GeV Upgrade

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghoshal, Probir K.; Bachimanchi, Ramakrishna; Fair, Ruben J.

The superconducting magnet system in Hall B being designed and built as part of the Jefferson Lab 12 GeV upgrade requires powering two conduction cooled superconducting magnets - a torus and a solenoid. The torus magnet is designed to operate at 3770 A and solenoid at 2416 A. Failure Modes and Effects Analysis (FMEA) determined that voltage level thresholds and dump switch operation for magnet protection should be tested and analyzed before incorporation into the system. The designs of the quench protection and voltage tap sub-systems were driven by the requirement to use a primary hard-wired quench detection sub-system togethermore » with a secondary PLC-based protection. Parallel path voltage taps feed both the primary and secondary quench protection sub-systems. The PLC based secondary protection is deployed as a backup for the hard-wired quench detection sub-system and also acts directly on the dump switch. Here, we describe a series of tests and modifications carried out on the magnet power supply and quench protection system to ensure that the superconducting magnet is protected for all fault scenarios.« less

Superconducting Magnet Power Supply and Hard-Wired Quench Protection at Jefferson Lab for 12 GeV Upgrade

DOE PAGES

Ghoshal, Probir K.; Bachimanchi, Ramakrishna; Fair, Ruben J.; ...

2017-10-05

The superconducting magnet system in Hall B being designed and built as part of the Jefferson Lab 12 GeV upgrade requires powering two conduction cooled superconducting magnets - a torus and a solenoid. The torus magnet is designed to operate at 3770 A and solenoid at 2416 A. Failure Modes and Effects Analysis (FMEA) determined that voltage level thresholds and dump switch operation for magnet protection should be tested and analyzed before incorporation into the system. The designs of the quench protection and voltage tap sub-systems were driven by the requirement to use a primary hard-wired quench detection sub-system togethermore » with a secondary PLC-based protection. Parallel path voltage taps feed both the primary and secondary quench protection sub-systems. The PLC based secondary protection is deployed as a backup for the hard-wired quench detection sub-system and also acts directly on the dump switch. Here, we describe a series of tests and modifications carried out on the magnet power supply and quench protection system to ensure that the superconducting magnet is protected for all fault scenarios.« less

Guest Editorial

NASA Astrophysics Data System (ADS)

Alagarsamy, Perumal; Srinivasan, Ananthakrishnan; Pandian, Subramanian

2014-09-01

Magnetic materials play a vital role in technologies ranging from those concerning the day-to-day life of man to special applications in nuclear, space, defense and health sectors. Despite several notable developments in theoretical and experimental fronts in the area of magnetism and magnetic materials and the ever increasing number of researchers and engineers actively engaged in these topics, only a few international conferences are being organized in these topics in Asia. To address this lacuna, the second edition of International Conference on Magnetic Materials and Applications - 2013 (MagMA-2013) was jointly hosted and organized by Indian Institute of Technology Guwahati (IITG) under the auspicious of Magnetics Society of India (MSI). MagMA-2013 devoted special sessions for (A) Soft and Hard Magnetic Materials and their Applications, (B) Magnetic Thin Films, Particles and Nanostructures, (C) Magnetic Recording, Memories, and Spintronics, (D) Strongly Correlated Electron System, (E) Fundamental Magnetic Properties and Cooperative Phenomena, (F) Novel Magnetic Materials and Device Applications, (G) Magnet Industry - Product and Marketing and (H) Interdisciplinary Topics in Magnetism. These sessions included plenary and invited talks by speakers drawn from the international arena who shared their expertise and experiences on recent developments in various topics such as (1) conventional (bulk and powder metallurgy processed) soft and hard magnetic materials, (2) novel forms (nanostructured, particulate/granular, composite, thin film and multilayered films) of soft and hard magnetic materials and their hybrids, (3) sensors and actuators based on magnetoresistive, magnetostrictive, magnetoelastic and magnetoimpedance materials, (4) magnetic storage and its trends, (5) multi-disciplinary area of bio-magnetism and applications of magnetic materials in medicine, (6) newly emerging interdisciplinary topics in magnetism and (7) recent progress in theoretical and computational techniques in magnetism.

Feasibility study of electrophoresis deposition of DyF3 on Nd-Fe-B particles for coercivity enhancement

NASA Astrophysics Data System (ADS)

Kim, K. M.; Kang, M. S.; Kwon, H. W.; Lee, J. G.; Yu, J. H.

2018-05-01

Feasibility of the electrophoresis deposition (EPD) technique for homogeneous and adhesive deposition of DyF3 particles on the Nd-Fe-B-type particles was studied, and coercivity enhancement in the diffusion-treated Nd-Fe-B-type particles deposited with DyF3 by EPD was investigated. HDDR-treated Nd12.5Fe80.6B6.4Ga0.3Nb0.2 particles were deposited with DyF3 particles by EPD. More homogeneous and adhesive deposition of DyF3 particles on the surface of Nd-Fe-B particles was made by the EPD with respect to conventional dip-coating, and this led to more active and homogeneous diffusion of Dy. More profound coercivity enhancement was achieved in the diffusion-treated Nd-Fe-B-type particles deposited with DyF3 by EPD compared to dip-coated particles.

Magnetic nanostructuring and overcoming Brown's paradox to realize extraordinary high-temperature energy products

NASA Astrophysics Data System (ADS)

Balasubramanian, Balamurugan; Mukherjee, Pinaki; Skomski, Ralph; Manchanda, Priyanka; Das, Bhaskar; Sellmyer, David J.

2014-09-01

Nanoscience has been one of the outstanding driving forces in technology recently, arguably more so in magnetism than in any other branch of science and technology. Due to nanoscale bit size, a single computer hard disk is now able to store the text of 3,000,000 average-size books, and today's high-performance permanent magnets--found in hybrid cars, wind turbines, and disk drives--are nanostructured to a large degree. The nanostructures ideally are designed from Co- and Fe-rich building blocks without critical rare-earth elements, and often are required to exhibit high coercivity and magnetization at elevated temperatures of typically up to 180 °C for many important permanent-magnet applications. Here we achieve this goal in exchange-coupled hard-soft composite films by effective nanostructuring of high-anisotropy HfCo7 nanoparticles with a high-magnetization Fe65Co35 phase. An analysis based on a model structure shows that the soft-phase addition improves the performance of the hard-magnetic material by mitigating Brown's paradox in magnetism, a substantial reduction of coercivity from the anisotropy field. The nanostructures exhibit a high room-temperature energy product of about 20.3 MGOe (161.5 kJ/m3), which is a record for a rare earth- or Pt-free magnetic material and retain values as high as 17.1 MGOe (136.1 kJ/m3) at 180°C.

A double-superconducting axial bearing system for an energy storage flywheel model

NASA Astrophysics Data System (ADS)

Deng, Z.; Lin, Q.; Ma, G.; Zheng, J.; Zhang, Y.; Wang, S.; Wang, J.

2008-02-01

The bulk high temperature superconductors (HTSCs) with unique flux-pinning property have been applied to fabricate two superconducting axial bearings for an energy storage flywheel model. The two superconducting axial bearings are respectively fixed at two ends of the vertical rotational shaft, whose stator is composed of seven melt-textured YBa2Cu3O7-x (YBCO) bulks with diameter of 30 mm, height of 18 mm and rotor is made of three cylindrical axial-magnetized NdFeB permanent magnets (PM) by superposition with diameter of 63 mm, height of 27 mm. The experimental results show the total levitation and lateral force produced by the two superconducting bearings are enough to levitate and stabilize the 2.4 kg rotational shaft. When the two YBCO stators were both field cooled to the liquid nitrogen temperature at respective axial distances above or below the PM rotor, the shaft could be automatically levitated between the two stators without any contact. In the case of a driving motor, it can be stably rotated along the central axis besides the resonance frequency. This double-superconducting axial bearing system can be used to demonstrate the flux-pinning property of bulk HTSC for stable levitation and suspension and the principle of superconducting flywheel energy storage system to visitors.

Latching Solenoid-Operated Ball Valve

NASA Technical Reports Server (NTRS)

Brudnicki, Myron

1994-01-01

Proposed solenoid-operated ball valve latches in open or closed position until energized to change position. Electrical energy consumed only during opening or closing motion. Valve ball contains central channel through which fluid could flow. Made of highly magnetically permeable steel. When appropriate coil(s) energized by brief pulse (or pulses) of electrical current at appropriate polarity, ball rotates clockwise until permanent magnets come to rest against hard stops in housing, and inlet and outlet ports aligned with central channel so fluid flows through valve. Magnets adhere to stops by magnetic attraction, latching valve in open position. To close valve, appropriate coil(s) energized by pulse (or pulses) of appropriate polarity to generate magnetic forces rotating ball counterclockwise until magnets make contact with hard stops, and inlet and outlet ports sealed.

Magnetic materials and devices for the 21st century: stronger, lighter, and more energy efficient.

PubMed

Gutfleisch, Oliver; Willard, Matthew A; Brück, Ekkes; Chen, Christina H; Sankar, S G; Liu, J Ping

2011-02-15

A new energy paradigm, consisting of greater reliance on renewable energy sources and increased concern for energy efficiency in the total energy lifecycle, has accelerated research into energy-related technologies. Due to their ubiquity, magnetic materials play an important role in improving the efficiency and performance of devices in electric power generation, conditioning, conversion, transportation, and other energy-use sectors of the economy. This review focuses on the state-of-the-art hard and soft magnets and magnetocaloric materials, with an emphasis on their optimization for energy applications. Specifically, the impact of hard magnets on electric motor and transportation technologies, of soft magnetic materials on electricity generation and conversion technologies, and of magnetocaloric materials for refrigeration technologies, are discussed. The synthesis, characterization, and property evaluation of the materials, with an emphasis on structure-property relationships, are discussed in the context of their respective markets, as well as their potential impact on energy efficiency. Finally, considering future bottlenecks in raw materials, options for the recycling of rare-earth intermetallics for hard magnets will be discussed. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhancement of switching stability of tunneling magnetoresistance system with artificial ferrimagnet

NASA Astrophysics Data System (ADS)

You, Chun-Yeol; Bader, Sam. D.; Scheinfein, M. R.

2002-03-01

In the study of spin dependent magnetic tunneling junctions, the switching stability of the magnetically hard layer is a crucial issue in magnetic random access memory applications[1]. After repeated cycling of the soft layer, the magnetization of the hard layer is demagnetized by the stray field from the domain wall created during the switching[2]. The magnitude of the stray field from the soft layer is large enough to switch a domain in the hard layer. Therefore, reducing this stray field is necessary to increase the switching stability. In this study, we explore an artificial ferrimagnet to replace the usual soft layer in order to reduce stray field. The ferrimagnet consists of an antiferromagnetically coupled trilayer that has two ferromagnetic layers of unequal thickness and opposite magnetization orientation. Since the sign of stray field of the two ferromagnetic layers is opposed, the total stray field is greatly reduced. [Supported by the US DOE, BES-MS, under Contract W-31-109-ENG-38.] [1] S. Gider et al. Science 281, 797 (1998). [2] L. Thomas et al. Phys. Rev. Lett. 84, 1816 (2000).

High-throughput search for new permanent magnet materials.

PubMed

Goll, D; Loeffler, R; Herbst, J; Karimi, R; Schneider, G

2014-02-12

The currently highest-performance Fe-Nd-B magnets show limited cost-effectiveness and lifetime due to their rare-earth (RE) content. The demand for novel hard magnetic phases with more widely available RE metals, reduced RE content or, even better, completely free of RE metals is therefore tremendous. The chances are that such materials still exist given the large number of as yet unexplored alloy systems. To discover such phases, an elaborate concept is necessary which can restrict and prioritize the search field while making use of efficient synthesis and analysis methods. It is shown that an efficient synthesis of new phases using heterogeneous non-equilibrium diffusion couples and reaction sintering is possible. Quantitative microstructure analysis of the domain pattern of the hard magnetic phases can be used to estimate the intrinsic magnetic parameters (saturation polarization from the domain contrast, anisotropy constant from the domain width, Curie temperature from the temperature dependence of the domain contrast). The probability of detecting TM-rich phases for a given system is high, therefore the approach enables one to scan through even higher component systems with one single sample. The visualization of newly occurring hard magnetic phases via their typical domain structure and the correlation existing between domain structure and intrinsic magnetic properties allows an evaluation of the industrial relevance of these novel phases.

Intramuscular changes of soft and hard areas after low-level static contraction of the masseter muscle and the correlations with muscle hardness and increase in water content: evaluations with sonographic elastography and magnetic resonance imaging.

PubMed

Ariji, Yoshiko; Nakayama, Miwa; Taguchi, Akira; Gotoh, Akihiko; Kise, Yoshitaka; Katsumata, Aakitoshi; Kurita, Kenichi; Ariji, Eiichiro

2013-09-01

To investigate the intramuscular changes on sonographic elastography (SE) after low-level static contraction of the masseter muscle, and to clarify the relationship with the total hardness and edematous change. Ten healthy volunteers performed sustained bilateral biting at 20% of maximal voluntary contraction for 10 min. The SE and magnetic resonance (MR) scans of the masseter muscles were performed before, immediately after, and 10 min after exercise. The masseter muscle elasticity index (MEI) ratio, muscle thickness, and intramuscular soft and hard areas distribution were evaluated on SE images. The signal to noise ratio (SNR), indicating the water content, was measured on MR images. The soft area ratio showed significant correlations with the water content expressed as SNR. The hard area ratio showed significant correlations with the total muscle hardness expressed as the MEI ratio. Intramuscular soft and hard areas could be used both clinically and experimentally. Copyright © 2013 Elsevier Inc. All rights reserved.

Rational design of the exchange-spring permanent magnet.

PubMed

Jiang, J S; Bader, S D

2014-02-12

The development of the optimal exchange-spring permanent magnet balances exchange hardening, magnetization enhancement, and the feasibility of scalable fabrication. These requirements can be met with a rational design of the microstructural characteristics. The magnetization processes in several model exchange-spring structures with different geometries have been analyzed with both micromagnetic simulations and nucleation theory. The multilayer geometry and the soft-cylinders-in-hard-matrix geometry have the highest achievable figure of merit (BH)max, while the soft-spheres-in-hard-matrix geometry has the lowest upper limit for (BH)max. The cylindrical geometry permits the soft phase to be larger and does not require strict size control. Exchange-spring permanent magnets based on the cylindrical geometry may be amenable to scaled-up fabrication.

Magnetic Properties of Hard Magnetic Alloy Fe - 28% Cr - 13.4% Co - 2% Mo - 0.5% Si

NASA Astrophysics Data System (ADS)

Vompe, T. A.; Milyaev, I. M.; Yusupov, V. S.

2017-01-01

The method of regression analysis is used to obtain equations describing the dependences of magnetic hysteresis properties of magnetically hard powder alloy Fe - 28% Cr - 13.4% Co - 2% Mo - 0.5% Si on regimes of thermomagnetic treatment (the temperatures of the start of the treatment and the rates of cooling in magnetic field). The determined treatment modes make it possible to obtain in an alloy with a coercive force H c up to 40 kA/m, a residual induction B r up to 1.2 T, and a maximum energy product ( BH)max up to 25 kJ/m3. The alloy may find application in the production of rotors of synchronous hysteresis-reluctance motors.

Fascinating Magnetic Energy Storage Nanomaterials: A Brief Review.

PubMed

Sreenivasulu, Kummari V; Srikanth, Vadali V S S

2017-07-10

In this brief review, the importance of nanotechnology in developing novel magnetic energy storage materials is discussed. The discussion covers recent patents on permanent magnetic materials and especially covers processing of permanent magnets (rare-earth and rare-earth free magnets), importance of rare-earth permanent magnets and necessity of rare-earth free permanent magnets. Magnetic energy storage materials are those magnetic materials which exhibit very high energy product (BH)max (where B is the magnetic induction in Gauss (G) whereas H is the applied magnetic field in Oersted (Oe)). (BH)max is the direct measure of the ability of a magnetic material to store energy. In this context, processing of magnetic energy storage composite materials constituted by soft and hard magnetic materials played a predominant role in achieving high (BH)max values due to the exchange coupling phenomenon between the soft and hard magnetic phases within the composite. Magnetic energy storage composites are normally composed of rare-earth magnetic materials as well as rare-earth free magnetic materials. Nanotechnology's influence on the enhancement of energy product due to the exchange coupling phenomenon is of great prominence and therefore discussed in this review. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Unravelling the tunable exchange bias-like effect in magnetostatically-coupled two dimensional hybrid (hard/soft) composites

NASA Astrophysics Data System (ADS)

Hierro-Rodriguez, A.; Teixeira, J. M.; Rodriguez-Rodriguez, G.; Rubio, H.; Vélez, M.; Álvarez-Prado, L. M.; Martín, J. I.; Alameda, J. M.

2015-06-01

Hybrid 2D hard-soft composites have been fabricated by combining soft (Co73Si27) and hard (NdCo5) magnetic materials with in-plane and out-of-plane magnetic anisotropies, respectively. They have been microstructured in a square lattice of CoSi anti-dots with NdCo dots within the holes. The magnetic properties of the dots allow us to introduce a magnetostatic stray field that can be controlled in direction and sense by their last saturating magnetic field. The magnetostatic interactions between dot and anti-dot layers induce a completely tunable exchange bias-like shift in the system’s hysteresis loops. Two different regimes for this shift are present depending on the lattice parameter of the microstructures. For large parameters, dipolar magnetostatic decay is observed, while for the smaller one, the interaction between the adjacent anti-dot’s characteristic closure domain structures enhances the exchange bias-like effect as clarified by micromagnetic simulations.

Hard X-ray Emission and Efficient Particle Acceleration by Supernova Remnants

NASA Astrophysics Data System (ADS)

Vink, Jacco

2009-05-01

I discuss the non-thermal X-ray emission from young supernova remnants. Over the last decade it has become clear from both X-ray and γ-ray observations that young supernovae accelerate particles up to 100 TeV. In soft X-rays the accelerated >10 TeV electrons produce synchrotron radiation, coming from narrow filaments located at the shock fronts. The width of these filaments shows that the magnetic fields are relatively high, thus providing evidence for magnetic field amplification. The synchrotron radiation of several remnants is known to extend into the hard X-ray regime. In particular Cas A, has a spectrum that appears as a power law up to almost 100 TeV. This is very surprising, as a steepening is expected going from the soft to the hard X-ray band. The spectrum is likely a result of many superimposed individual spectra, each steepening at different energies. This implies considerable spatial variation in hard X-rays, an obvious target for Simbol-X. The variations will be important to infer local shock acceleration properties, but also magnetic field fluctuations may cause spatial and temporal variations. Finally, I draw the attention to super bubbles and supernovae as sources of cosmic rays. As such they may be sources of hard X-ray emission. In particular, supernovae exploding inside the dense red supergiants winds of their progenitors ares promising candidates for hard X-ray emission.

Novel design configurations for permanent magnet wind generators

NASA Astrophysics Data System (ADS)

Chen, Yicheng

2004-12-01

The aim of this research is to search for optimal designs of permanent magnet (PM) wind generators of different topologies. The dissertation deals with the development of analytical design equations and formulas for PM wind generators of different topologies, including equivalent magnetic circuit model for magnets, calculation of leakage flux, influence of d-q axis armature reaction, flux waveform analysis, as well as performance verification. 3-D and simplified 2-D finite element analysis is used to enhance the design precision, by which analytical formulas are modified. A new and improved formula is proposed for lamination loss calculations, based on a large experimental data set provided by steel manufacturers. The temperature stability of NdFeB magnets is analyzed and some proposals for eliminating irreversible demagnetization are presented. Two existing experimental machines are used to validate the design equations. The genetic algorithms are used to investigate the multi-objective design optimization of PM wind generators for a high efficiency and light-weight design. The reasoning behind the selection of the objective functions, design variables and constraints are given as guidance for the PM wind generator optimum design. The implementation of the genetic algorithm is also given. A comparison of PM wind generators of different topologies is presented. Conclusions are drawn for topology selections of PM wind generators. The group of soft magnetic composites (SMC) has recently been expanded by the introduction of new materials with significantly improved frequency properties. This has made SMC a viable alternative to steel laminations for a range of new applications, especially axial-flux wind generators. The isotropic nature of the SMC combined with the unique shaping possibilities opens up new design solutions for axial-flux wind generators. Through careful design, an axial-flux PM wind generator with SMC core is built and tested, demonstrating the advantages of better performance, reduced size and weight, fewer parts and lower cost.

Crystal-field splittings in rare-earth-based hard magnets: An ab initio approach

NASA Astrophysics Data System (ADS)

Delange, Pascal; Biermann, Silke; Miyake, Takashi; Pourovskii, Leonid

2017-10-01

We apply the first-principles density functional theory + dynamical mean-field theory framework to evaluate the crystal-field splitting on rare-earth sites in hard magnetic intermetallics. An atomic (Hubbard-I) approximation is employed for local correlations on the rare-earth 4 f shell and self-consistency in the charge density is implemented. We reduce the density functional theory self-interaction contribution to the crystal-field splitting by properly averaging the 4 f charge density before recalculating the one-electron Kohn-Sham potential. Our approach is shown to reproduce the experimental crystal-field splitting in the prototypical rare-earth hard magnet SmCo5. Applying it to R Fe12 and R Fe12X hard magnets (R =Nd , Sm and X =N , Li), we obtain in particular a large positive value of the crystal-field parameter A20〈r2〉 in NdFe12N resulting in a strong out-of-plane anisotropy observed experimentally. The sign of A20〈r2〉 is predicted to be reversed by substituting N with Li, leading to a strong out-of-plane anisotropy in SmFe12Li . We discuss the origin of this strong impact of N and Li interstitials on the crystal-field splitting on rare-earth sites.

Non-rare earth magnetic nanoparticles

DOEpatents

Carpenter, Everett E.; Huba, Zachary J.; Carroll, Kyler J.; Farghaly, Ahmed; Khanna, Shiv N.; Qian, Meichun; Bertino, Massimo

2017-09-26

Continuous flow synthetic methods are used to make single phase magnetic metal alloy nanoparticles that do not contain rare earth metals. Soft and hard magnets made from the magnetic nanoparticles are used for a variety of purposes, e.g. in electric motors, communication devices, etc.

A new quasi-thermal trap model for solar flare hard X-ray bursts - An electrostatic trap model

NASA Technical Reports Server (NTRS)

Spicer, D. S.; Emslie, A. G.

1988-01-01

A new quasi-thermal trap model of solar flare hard X-ray bursts is presented. The new model utilizes the trapping ability of a magnetic mirror and a magnetic field-aligned electrostatic potential produced by differences in anisotropies of the electron and ion distribution function. It is demonstrated that this potential can, together with the magnetic mirror itself, effectively confine electrons in a trap, thereby enhancing their bremsstrahlung yield per electron. This analysis makes even more untenable models involving precipitation of the bremsstrahlung-producing electrons onto a cold target.

Mechanochemical synthesis of LaCo5 magnetically hard anisotropic powder

NASA Astrophysics Data System (ADS)

Gabay, A. M.; Hadjipanayis, G. C.

2014-05-01

LaCo5 particles were prepared from La2O3 and Co powders processed in the presence of Ca as a reducing agent and a CaO dispersant. After high-energy ball milling followed by a short annealing at 900 °C, the particles exhibited a room-temperature intrinsic coercivity of 24.5 kOe. Separation of the hard magnetic particles with water is accompanied by the release of hydrogen and this leads to replacement of the LaCo5 structure by various LaCo5Hx hydrides. The LaCo5 structure was restored by removing hydrogen via vacuum annealing. The resulting particles were polydispersed with an average size of 540 nm and crystallographically anisotropic; they exhibited a remanent magnetization of 83.8 emu g-1 (8.7 kG) and a coercivity of 9.6 kOe. The dramatic improvement of the hard magnetic properties as compared to those obtained by standard milling is attributed to a lower density of anisotropy defects at the surface of the mechanochemically synthesized particles. This advantage may allow for the commercial utilization of more abundant/less expensive raw materials for permanent magnets.

Magnetization measurements reveal the local shear stiffness of hydrogels probed by ferromagnetic nanorods

NASA Astrophysics Data System (ADS)

Bender, P.; Tschöpe, A.; Birringer, R.

2014-12-01

The local mechanical coupling of ferromagnetic nanorods in hydrogels was characterized by magnetization measurements. Nickel nanorods were synthesized by the AAO-template method and embedded in gelatine hydrogels with mechanically soft or hard matrix properties determined by the gelatine weight fraction. By applying a homogeneous magnetic field during gelation the nanorods were aligned along the field resulting in uniaxially textured ferrogels. The magnetization curves of the soft ferrogel exhibited not only important similarities but also characteristic differences as compared to the hard ferrogel. The hystereses measured in a field parallel to the texture axis were almost identical for both samples indicating effective coupling of the nanorods with the polymer network. By contrast, measurements in a magnetic field perpendicular to the texture axis revealed a much higher initial susceptibility of the soft as compared to the hard ferrogel. This difference was attributed to the additional rotation of the nanorods allowed by the reduced shear modulus in the soft ferrogel matrix. Two methods for data analysis were presented which enabled us to determine the shear modulus of the gelatine matrix which was interpreted as a local rather than macroscopic quantity in consideration of the nanoscale of the probe particles.

Spin-polarized scanning tunneling microscopy experiments on the rough surface of a polycrystalline NiFe film with a fine magnetic tip sensitive to a well-defined magnetization component

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsuyama, H., E-mail: matsu@phys.sci.hokudai.ac.jp; Nara, D.; Kageyama, R.

We developed a micrometer-sized magnetic tip integrated onto the write head of a hard disk drive for spin-polarized scanning tunneling microscopy (SP-STM) in the modulated tip magnetization mode. Using SP-STM, we measured a well-defined in-plane spin-component of the tunneling current of the rough surface of a polycrystalline NiFe film. The spin asymmetry of the NiFe film was about 1.3% within the bias voltage range of -3 to 1 V. We obtained the local spin component image of the sample surface, switching the magnetic field of the sample to reverse the sample magnetization during scanning. We also obtained a spin imagemore » of the rough surface of a polycrystalline NiFe film evaporated on the recording medium of a hard disk drive.« less

Ames Lab 101: Ultrafast Magnetic Switching

ScienceCinema

Wang; Jigang

2018-01-01

Ames Laboratory physicists have found a new way to switch magnetism that is at least 1000 times faster than currently used in magnetic memory technologies. Magnetic switching is used to encode information in hard drives, magnetic random access memory and other computing devices. The discovery potentially opens the door to terahertz and faster memory speeds.

A New Hard X-ray Wiggler for DORIS III

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tischer, M.; Gumprecht, L.; Pflueger, J.

2007-01-19

A 4 m long hard X-ray wiggler has been built and installed in the DORIS III storage ring at DESY. The device replaces an old wiggler especially designed for angiography studies. Future use of this beamline at the HARWI straight section has been dedicated to hard X-ray scattering and diffraction experiments for material science and geological investigations. The required energy range is from 30 keV to about 200 keV with emphasis on the {approx}100 keV spectral range. The magnet configuration corresponds to a hybrid structure with additional side magnets to achieve a 2 T peak field for the specified periodmore » length of 110 mm. The wiggler position in the storage ring has been moved 8 m upstream into the next cell which allowed for reduction of the minimum magnetic wiggler gap to 14 mm.« less

Microstructure evolution and coercivity enhancement in Nd-Fe-B thin films diffusion-processed by R-Al alloys (R=Nd, Pr)

NASA Astrophysics Data System (ADS)

Xie, Yigao; Yang, Yang; Zhang, Tongbo; Fu, Yanqing; Jiang, Qingzheng; Ma, Shengcan; Zhong, Zhenchen; Cui, Weibin; Wang, Qiang

2018-05-01

Diffusion process by Nd-Al and Pr-Al alloys was compared and investigated in Nd-Fe-B thin films. Enhanced coercivity 2.06T and good squareness was obtained by using Pr85Al15 and Nd85Al15 alloys as diffusion sources. But the coercivity of diffusion-processed thin films by Pr70Al30 and Pr55Al45 alloys decreased to 2.04T and 1.82T. High ambient coercivity of 2.26T was achieved in diffusion-processed thin film by Nd70Al30 leading to an improved coercivity thermal stability because Nd2Fe14B grains were enveloped by Nd-rich phase as seen by transmission electron microscopy Nd-loss image. Meanwhile, microstructure-dependent parameters α and Neff were improved. However, high content of Al in diffusion-processed thin film by Nd55Al45 lead to degraded texture and coercivity.

Investigation of the Nd-rich phases in the Nd-Fe-B system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, W.; Zhou, S.; Wang, R.

1988-11-15

The crystal structures and the compositions of the Nd-rich phases in the Nd-Fe-B system have been investigated by means of transmission electron microscopy, x-ray diffraction, and Auger spectroscopy techniques. It has been observed that there are two kinds of Nd-rich phases with different structures and compositions. Most of the Nd-rich phases will undergo a phase transformation when the powder is sintered at high temperatures. This phase transformation is accompanied by the introduction of oxygen into the alloy which will change from a ternary system into a quaternary one. Both of the two Nd-rich phases are stable phases in this latermore » system. With the aid of the EDX and the Auger spectroscope, the compositions of the dhcp and the fcc Nd-rich phases have been determined. The Nd contents of the two phases are about 90 and 70 at. %, respectively, with the later phase containing about 15 at. % of oxygen.« less

Magnetic small-angle neutron scattering on bulk metallic glasses: A feasibility study for imaging displacement fields

NASA Astrophysics Data System (ADS)

Mettus, Denis; Deckarm, Michael; Leibner, Andreas; Birringer, Rainer; Stolpe, Moritz; Busch, Ralf; Honecker, Dirk; Kohlbrecher, Joachim; Hautle, Patrick; Niketic, Nemanja; Fernández, Jesús Rodríguez; Barquín, Luis Fernández; Michels, Andreas

2017-12-01

Magnetic-field-dependent small-angle neutron scattering (SANS) has been utilized to study the magnetic microstructure of bulk metallic glasses (BMGs). In particular, the magnetic scattering from soft magnetic Fe70Mo5Ni5P12.5B2.5C5 and hard magnetic (Nd60Fe30Al10) 92Ni8 alloys in the as-prepared, aged, and mechanically deformed state is compared. While the soft magnetic BMGs exhibit a large field-dependent SANS response with perturbations originating predominantly from spatially varying magnetic anisotropy fields, the SANS cross sections of the hard magnetic BMGs are only weakly dependent on the field, and their angular anisotropy indicates the presence of scattering contributions due to spatially dependent saturation magnetization. Moreover, we observe an unusual increase in the magnetization of the rare-earth-based alloy after deformation. Analysis of the SANS cross sections in terms of the correlation function of the spin misalignment reveals the existence of field-dependent anisotropic long-wavelength magnetization fluctuations on a scale of a few tens of nanometers. We also give a detailed account of how the SANS technique relates to unraveling displacement fields on a mesoscopic length scale in disordered magnetic materials.

Hard X-ray Emission and Efficient Particle Acceleration by Supernova Remnants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vink, Jacco

I discuss the non-thermal X-ray emission from young supernova remnants. Over the last decade it has become clear from both X-ray and {gamma}-ray observations that young supernovae accelerate particles up to 100 TeV. In soft X-rays the accelerated >10 TeV electrons produce synchrotron radiation, coming from narrow filaments located at the shock fronts. The width of these filaments shows that the magnetic fields are relatively high, thus providing evidence for magnetic field amplification.The synchrotron radiation of several remnants is known to extend into the hard X-ray regime. In particular Cas A, has a spectrum that appears as a power lawmore » up to almost 100 TeV. This is very surprising, as a steepening is expected going from the soft to the hard X-ray band. The spectrum is likely a result of many superimposed individual spectra, each steepening at different energies. This implies considerable spatial variation in hard X-rays, an obvious target for Simbol-X. The variations will be important to infer local shock acceleration properties, but also magnetic field fluctuations may cause spatial and temporal variations.Finally, I draw the attention to super bubbles and supernovae as sources of cosmic rays. As such they may be sources of hard X-ray emission. In particular, supernovae exploding inside the dense red supergiants winds of their progenitors ares promising candidates for hard X-ray emission.« less

Epitaxial Fe{sub 3}Pt/FePt nanocomposites on MgO and SrTiO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Casoli, F., E-mail: casoli@imem.cnr.it; Nasi, L.; Cabassi, R.

We have exploited the pseudomorphic growth of the magnetically soft Fe{sub 3}Pt phase on top of L1{sub 0}-FePt to obtain fully epitaxial soft/hard nanocomposites on both MgO(100) and SrTiO{sub 3}(100). The magnetic properties of this new nanocomposite system, driven by the soft/hard exchange-coupling, can be tailored by varying soft phase thickness, soft phase magnetic anisotropy and substrate. Coercivity is strongly reduced by the addition of the soft phase, a reduction which is definitely affected by the nominal composition of the soft phase and by the substrate choice; similarly is the magnetic phase diagram of the composite system. Coercive field decreasesmore » down to 21% of the hard layer value for Fe{sub 3}Pt(5 nm)/FePt(3.55 nm) nanocomposites on SrTiO{sub 3}; this maximum coercivity reduction was obtained with a nominal atomic content of Fe in the soft phase of 80%.« less

Hard X-ray spectra of neutron stars and black hole candidates

NASA Technical Reports Server (NTRS)

Durouchoux, P.; Mahoney, W.; Clenet, Y.; Ling, J.; Wallyn, P.; Wheaton, W.; Corbet, S.; Chapuis, C.

1997-01-01

The hard X-ray behavior of several X-ray binary systems containing a neutron star or a black hole candidate is analyzed in an attempt to determine the specific signature of these categories of compact objects. Limiting the consideration to two subclasses of neutron stars, Atoll sources and non-pulsating Z sources, it appears that only the Atoll sources have a spectral behavior similar to black holes. It is proposed that Atoll sources are weakly magnetized neutron stars, whereas Z sources are small radius moderate magnetized neutron stars. Large magnetic fields funnel the accreting matter, thus preventing spherical accretion and free fall if the neutron star radius is smaller than the last stable accreting orbit. Weak magnetic fields do not have this effect, and blackbody soft photons from the stellar surface are upscattered on the relativistic infalling matter, leading to excess hard X-rays. This excess is visible in two of the observed Atoll sources and in the spectrum of a black hole candidate. In the case of a Z source, a lack of photons was remarked, providing a possible signature to distinguish between these classes of objects.

Magnetic Materials

DTIC Science & Technology

1985-03-01

provides high magnetic field capabilities. The emphasis, however, has largely been on semiconaucting and superconducting materials. The lab has not...was easily magnetized and demagnetized , whereas iiardened 0reel acted as a permanent magnet , led to the terminology of hard and soBt magnetic ...similar to Alnico, have relatively low magnetization but high coercive fields. They are well suited for uses where the demagnetizing fields are high

The Stoner-Wohlfarth Model of Ferromagnetism

ERIC Educational Resources Information Center

Tannous, C.; Gieraltowski, J.

2008-01-01

The Stoner-Wohlfarth (SW) model is the simplest model that describes adequately the physics of fine magnetic grains, the magnetization of which can be used in digital magnetic storage (floppies, hard disks and tapes). Magnetic storage density is presently increasing steadily in almost the same way as electronic device size and circuitry are…

Miniature magnetic fluid seal working in liquid environments

NASA Astrophysics Data System (ADS)

Mitamura, Yoshinori; Durst, Christopher A.

2017-06-01

This study was carried out to develop a miniature magnetic fluid (MF) seal working in a liquid environment. The miniature MF seal is intended for use in a catheter blood pump. The requirements for the MF seal included a size of less than Ø4×4.5 mm, shaft diameter of 1 mm, sealing pressure of 200 mmHg, shaft speed of up to 40000 rpm, and life of one month. The miniature MF seal was composed of an NdFeB magnet (Ø4×Ø2×1) sandwiched between two pole pieces (Ø4×Ø1.1×0.5). A shield (Ø4×Ø1.2×1.5) was placed on the pole piece facing the liquid to minimize the influence of pump flow on the MF. The seal was installed on a Ø1 shaft. A seal was formed by injecting MF (Ms: 47.8 kA/m and η: 0.5 Pa·sec) into the gap between the pole pieces and the shaft. Total volume of the MF seal was 44 μL. A sealing pressure of 370 mmHg was obtained at motor speeds of 0-40,000 rpm. The seal remained perfect for 10 days in saline under the condition of a pump flow of 1.5 L/min (The test was terminated in accordance with plans). The seal remained intact after ethylene oxide sterilization during which the seal was exposed to high pressures. In conclusion, the newly developed MF seal will be useful for a catheter pump.

Static magnetic field effects on proteases with fibrinolytic activity produced by Mucor subtilissimus.

PubMed

Albuquerque, Wendell; Nascimento, Thiago; Brandão-Costa, Romero; Fernandes, Thiago; Porto, Ana

2017-02-01

The influence of a static magnetic field (SMF) on crude enzyme extracts with proteolytic activity is described and discussed. Proteolytic enzymes, which hydrolyze peptide bonds, and fibrinolytic enzymes, which dissolve fibrin clots, have industrial relevance, and applicability dependent on improvements of productivity and activity. We investigated whether a moderate SMF affects proteolysis in different in vitro tests: general proteolysis of azocasein substrate, and static and dynamic fibrinolytic processes (to compare fibrin gel configuration under exposure). Crude enzyme extracts, obtained from solid state fermentation of Mucor subtilissimus UCP (Universidade Católica de Pernambuco, Recife, Brazil) 1262, were used to carry out assays under slightly heterogeneous fields: a varied vertical SMF (for tests in Eppendorf tubes, from 0.100 to 0.170 T) and a varied horizontal SMF (for tests in Petri dishes, from 0.01 to 0.122 T), generated by two permanent magnets (NdFeB alloy). Results showed significant differences (P < 0.05) in static fibrinolysis assays after 24 h of exposure. The mean diameter of halos of fibrin degradation in the treated group increased by 21% compared to the control group; and the pixel number count of fibrin consumption (in a computational analysis of the area of each halo) enhanced by 30% with exposure. However, in dynamic fibrinolysis assays, no effects of SMF were observed. These results suggest a response of fibrin monomers to the SMF as a possible cause of the observed effects. Bioelectromagnetics. 38:109-120, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Development of a miniature motor-driven pulsatile LVAD driven by a fuzzy controller.

PubMed

Okamoto, Eiji; Makino, Tsutomu; Tanaka, Shuji; Yasuda, Takahiko; Akasaka, Yuta; Tani, Makiko; Inoue, Yusuke; Mitoh, Ayumu; Mitamura, Yoshinori

2007-01-01

We have been developing a small, lightweight motor-driven pulsatile left ventricular assist device (LVAD) with a ball screw. The motor-driven LVAD consists of a brushless DC motor and a ball screw. The attractive magnetic force between Nd-Fe-B magnets (with a diameter of 5 mm and a thickness of 1.5 mm) mounted in holes in a silicone rubber sheet (thickness 2 mm) and an iron plate adhered onto the a diaphragm of the blood pump can provide optimum active blood filling during the pump filling phase. The LVAD has a stroke volume of 55 ml and an overall volume of 285 ml; it weighs 360 g. The controller mainly consists of a fuzzy logic position and velocity controller to apply doctors' and engineers' knowledge to control the LVAD. Each unit of the controller consists of a functionally independent program module for easy improvement of the controller's performance. The LVAD was evaluated in in vitro experiments using a mock circulation. A maximum pump outflow of 5.1 l/min was obtained at a drive rate of 95 bpm against an afterload of 95 mmHg, and active filling using the attractive magnetic force provided a pump output of 3.6 l/min at a drive rate of 75 bpm under a preload of 0 mmHg. The operating efficiency of the LVAD was measured at between 8% and 10.5%. While the LVAD can provide adequate pump outflow for cardiac assistance, further upgrading of the software and improvement of the blood pump are required to improve pump performance and efficiency.

Embedded NMR Sensor to Monitor Compressive Strength Development and Pore Size Distribution in Hydrating Concrete

PubMed Central

Díaz-Díaz, Floriberto; de J. Cano-Barrita, Prisciliano F.; Balcom, Bruce J.; Solís-Nájera, Sergio E.; Rodríguez, Alfredo O.

2013-01-01

In cement-based materials porosity plays an important role in determining their mechanical and transport properties. This paper describes an improved low–cost embeddable miniature NMR sensor capable of non-destructively measuring evaporable water loss and porosity refinement in low and high water-to-cement ratio cement-based materials. The sensor consists of two NdFeB magnets having their North and South poles facing each other, separated by 7 mm to allow space for a Faraday cage containing a Teflon tube and an ellipsoidal RF coil. To account for magnetic field changes due to temperature variations, and/or the presence of steel rebars, or frequency variation due to sample impedance, an external tuning circuit was employed. The sensor performance was evaluated by analyzing the transverse magnetization decay obtained with a CPMG measurement from different materials, such as a polymer phantom, fresh white and grey cement pastes with different w/c ratios and concrete with low (0.30) and high (0.6) w/c ratios. The results indicated that the sensor is capable of detecting changes in water content in fresh cement pastes and porosity refinement caused by cement hydration in hardened materials, even if they are prepared with a low w/c ratio (w/c = 0.30). The short lifetime component of the transverse relaxation rate is directly proportional to the compressive strength of concrete determined by destructive testing. The r2 (0.97) from the linear relationship observed is similar to that obtained using T2 data from a commercial Oxford Instruments 12.9 MHz spectrometer.

Dysprosium electrodeposition from a hexaalkylguanidinium-based ionic liquid.

PubMed

Berger, Claudia A; Arkhipova, Maria; Maas, Gerhard; Jacob, Timo

2016-08-07

The rare-earth element dysprosium (Dy) is an important additive that increases the magnetocrystalline anisotropy of neodymium magnets and additionally prevents from demagnetizing at high temperatures. Therefore, it is one of the most important elements for high-tech industries and is mainly used in permanent magnetic applications, for example in electric vehicles, industrial motors and direct-drive wind turbines. In an effort to develop a more efficient electrochemical technique for depositing Dy on Nd-magnets in contrast to commonly used costly physical vapor deposition, we investigated the electrochemical behavior of dysprosium(iii) trifluoromethanesulfonate in a custom-made guanidinium-based room-temperature ionic liquid (RTIL). We first examined the electrodeposition of Dy on an Au(111) model electrode. The investigation was carried out by means of cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS). The initial stages of metal deposition were followed by in situ scanning tunneling microscopy (STM). CV measurements revealed a large cathodic reduction peak, which corresponds to the growth of monoatomic high islands, based on STM images taken during the initial stages of deposition. XPS identified these deposited islands as dysprosium. A similar reduction peak was also observed on an Nd-Fe-B substrate, and positively identified as deposited Dy using XPS. Finally, we varied the concentration of the Dy precursor, electrolyte flow and temperature during Dy deposition and demonstrated that each of these parameters could be used to increase the thickness of the Dy deposit, suggesting that these parameters could be tuned simultaneously in a temperature-controlled flow cell to enhance the thickness of the Dy layer.

The Levitation Characteristics of MGB2 Plates on Tracks of Permanent Magnets

NASA Astrophysics Data System (ADS)

Perini, E.; Bassani, E.; Giunchi, G.

2010-04-01

The bulk MgB2 can be manufactured in large plates by an innovative process: the reactive liquid Mg infiltration (Mg-RLI). According to this process it is possible to produce, even at lab scale, plates of 10÷20 cm in lateral dimensions. The superconducting material resulting is very dense and, even if it is in polycrystalline form, it levitates with respect to Permanent Magnets (PM), like the textured YBCO samples, up to 35 K. In order to control the levitation forces and stiffnesses of an MgB2 plate (10×10×1 cm3) moving with respect to a track of PM's (NdFeB bars arranged in 4 lines according to an Halbach disposition and separated by Iron flux concentrators), we have used an instrumented Cryogenic Levitation Apparatus (CLA). We have studied different kind of movements of the PM's track with respect to the MgB2 plate. First, we consider the vertical movement, assumed z direction, which describes the properly levitation characteristics. Secondly, we consider two kinds of lateral movements of the track, assumed x direction, with the long size of the magnets either perpendicular or parallel to the movement direction. The resulting configurations simulate the main movements that a superconducting levitating vehicle will do in a real track, either of axial or of guidance type. The levitation axial forces, measured in Field Cooling or Zero Field Cooling conditions, indicate that at the distance between superconducting plate and PM's of 4 mm it is possible to have an overall levitating pressure of 7 N/cm2.

Development and studies on a compact electron cyclotron resonance plasma source

NASA Astrophysics Data System (ADS)

Ganguli, A.; Tarey, R. D.; Arora, N.; Narayanan, R.

2016-04-01

It is well known that electron cyclotron resonance (ECR) produced plasmas are efficient, high-density plasma sources and have many industrial applications. The concept of a portable compact ECR plasma source (CEPS) would thus become important from an application point of view. This paper gives details of such a CEPS that is both portable and easily mountable on a chamber of any size. It uses a fully integrated microwave line operating at 2.45 GHz, up to 800 W, cw. The required magnetic field is produced by a set of suitably designed NdFeB ring magnets; the device has an overall length of  ≈60 cm and weighs  ≈14 kg including the permanent magnets. The CEPS was attached to a small experimental chamber to judge its efficacy for plasma production. In the pressure range of 0.5-10 mTorr and microwave power of  ≈400-500 W the experiments indicate that the CEPS is capable of producing high-density plasma (≈9  ×  1011-1012 cm-3) with bulk electron temperature in the range  ≈2-3 eV. In addition, a warm electron population with density and temperature in the range ≈7  ×  108-109 cm-3 and  ≈45-80 eV, respectively has been detected. This warm population plays an important role at high pressures in maintaining the high-density plasma, when plasma flow from the CEPS into the test chamber is strongly affected.

Electric field control of magnetic states in isolated and dipole-coupled FeGa nanomagnets delineated on a PMN-PT substrate.

PubMed

Ahmad, Hasnain; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

2015-10-09

We report observation of a 'non-volatile' converse magneto-electric effect in elliptical FeGa nanomagnets delineated on a piezoelectric PMN-PT substrate. The nanomagnets are first magnetized with a magnetic field directed along their nominal major axes. Subsequent application of a strong electric field across the piezoelectric substrate generates strain in the substrate, which is partially transferred to the nanomagnets and rotates the magnetizations of some of them away from their initial orientations. The rotated magnetizations remain in their new orientations after the field is removed, resulting in 'non-volatility'. In isolated nanomagnets, the magnetization rotates by <90° upon application of the electric field, but in a dipole-coupled pair consisting of one 'hard' and one 'soft' nanomagnet, which are both initially magnetized in the same direction by the magnetic field, the soft nanomagnet's magnetization rotates by [Formula: see text] upon application of the electric field because of the dipole influence of the hard nanomagnet. This effect can be utilized for a nanomagnetic NOT logic gate.

ThMn12-type phases for magnets with low rare-earth content: Crystal-field analysis of the full magnetization process.

PubMed

Tereshina, I S; Kostyuchenko, N V; Tereshina-Chitrova, E A; Skourski, Y; Doerr, M; Pelevin, I A; Zvezdin, A K; Paukov, M; Havela, L; Drulis, H

2018-02-26

Rare-earth (R)-iron alloys are a backbone of permanent magnets. Recent increase in price of rare earths has pushed the industry to seek ways to reduce the R-content in the hard magnetic materials. For this reason strong magnets with the ThMn 12  type of structure came into focus. Functional properties of R(Fe,T) 12 (T-element stabilizes the structure) compounds or their interstitially modified derivatives, R(Fe,T) 12 -X (X is an atom of hydrogen or nitrogen) are determined by the crystal-electric-field (CEF) and exchange interaction (EI) parameters. We have calculated the parameters using high-field magnetization data. We choose the ferrimagnetic Tm-containing compounds, which are most sensitive to magnetic field and demonstrate that TmFe 11 Ti-H reaches the ferromagnetic state in the magnetic field of 52 T. Knowledge of exact CEF and EI parameters and their variation in the compounds modified by the interstitial atoms is a cornerstone of the quest for hard magnetic materials with low rare-earth content.

A Compact and Low-Cost MEMS Loudspeaker for Digital Hearing Aids.

PubMed

Sang-Soo Je; Rivas, F; Diaz, R E; Jiuk Kwon; Jeonghwan Kim; Bakkaloglu, B; Kiaei, S; Junseok Chae

2009-10-01

A microelectromechanical-systems (MEMS)-based electromagnetically actuated loudspeaker to reduce form factor, cost, and power consumption, and increase energy efficiency in hearing-aid applications is presented. The MEMS loudspeaker has multilayer copper coils, an NiFe soft magnet on a thin polyimide diaphragm, and an NdFeB permanent magnet on the perimeter. The coil impedance is measured at 1.5 Omega, and the resonant frequency of the diaphragm is located far from the audio frequency range. The device is driven by a power-scalable, 0.25-mum complementary metal-oxide semiconductor class-D SigmaDelta amplifier stage. The class-D amplifier is formed by a differential H-bridge driven by a single bit, pulse-density-modulated SigmaDelta bitstream at a 1.2-MHz clock rate. The fabricated MEMS loudspeaker generates more than 0.8-mum displacement, equivalent to 106-dB sound pressure level (SPL), with 0.13-mW power consumption. Driven by the SigmaDelta class-D amplifier, the MEMS loudspeaker achieves measured 65-dB total harmonic distortion (THD) with a measurement uncertainty of less than 10%. Energy-efficient and cost-effective advanced hearing aids would benefit from further miniaturization via MEMS technology. The results from this study appear very promising for developing a compact, mass-producible, low-power loudspeaker with sufficient sound generation for hearing-aid applications.

A review of high magnetic moment thin films for microscale and nanotechnology applications

DOE PAGES

Scheunert, Gunther; Heinonen, O.; Hardeman, R.; ...

2016-02-17

Here, the creation of large magnetic fields is a necessary component in many technologies, ranging from magnetic resonance imaging, electric motors and generators, and magnetic hard disk drives in information storage. This is typically done by inserting a ferromagnetic pole piece with a large magnetisation density M S in a solenoid. In addition to large M S, it is usually required or desired that the ferromagnet is magnetically soft and has a Curie temperature well above the operating temperature of the device. A variety of ferromagnetic materials are currently in use, ranging from FeCo alloys in, for example, hard diskmore » drives, to rare earth metals operating at cryogenic temperatures in superconducting solenoids. These latter can exceed the limit on M S for transition metal alloys given by the Slater-Pauling curve. This article reviews different materials and concepts in use or proposed for technological applications that require a large M S, with an emphasis on nanoscale material systems, such as thin and ultra-thin films. Attention is also paid to other requirements or properties, such as the Curie temperature and magnetic softness. In a final summary, we evaluate the actual applicability of the discussed materials for use as pole tips in electromagnets, in particular, in nanoscale magnetic hard disk drive read-write heads; the technological advancement of the latter has been a very strong driving force in the development of the field of nanomagnetism.« less

Retention assessment of magnetic nanoparticles in rat arteries with micro-computed tomography

NASA Astrophysics Data System (ADS)

Tu, Shu-Ju; Wu, Siao-Yun; Wang, Fu-Sheng; Ma, Yunn-Hwa

2014-03-01

Magnetic nanoparticles (MNPs) may serve as carriers for pharmacological agents to the target in a magnetic-force guiding system. It is essential to achieve effective retention of MNPs through the external magnet placement. However, it is difficult to estimate the retention efficiency of MNPs and validate the experimental strategies. Micro-CT was used to identify the spatial distribution of MNP retention and image analysis is then extended to evaluate the MNP delivery efficiency. Male Sprague Dawley rats were anesthetized to expose abdominal arteries with an NdFeB magnet of 4.9 kG placed by the left iliac artery. After a 20 min equilibrium period, arteries were ligated, removed and fixed in a paraformaldehyde solution. Experiments were performed with intravenous injection in our platform with two independent groups. MNPs were used in the first group, while chemical compounds of recombinant tissue plaminogen activator were attached to MNPs as rtPA (recombinant tissue plaminogen activator)-MNPs in the second group. Image analysis of micro-CT shows the average retention volume of MNPs and rtPA-MNPs in the left iliac arteries is 9.3 and 6.3 fold of that in the right. Large local aggregation of MNPs and rtPA-MNPs in the left iliac arteries is the consequence of external magnet placement, suggesting feasibility of magnetic targeting through the intravenous administration. We also determined that on average 0.57% and 0.064% of MNPs and rtPA-MNPs respectively were retained in the left iliac artery. It was estimated that the average rtPA concentration of 60.16 µg mL-1 may be achieved with rtPA-MNPs. With the micro-CT imaging approach, we accomplished visualization of the aggregation of retained particles; reconstructed 3D distribution of relative retention; estimated the average particle number of local retention; determined efficiency of targeted delivery. In particular, our quantitative image assessment suggests that intravenous administration of rtPA-MNPs may retain local concentration of rtPA high enough to induce thrombolysis.

Maximizing coupling strength of magnetically anchored surgical instruments: how thick can we go?

PubMed

Best, Sara L; Bergs, Richard; Gedeon, Makram; Paramo, Juan; Fernandez, Raul; Cadeddu, Jeffrey A; Scott, Daniel J

2011-01-01

The Magnetic Anchoring and Guidance System (MAGS) includes an external magnet that controls intra-abdominal surgical instruments via magnetic attraction forces. We have performed NOTES (Natural Orifice Transluminal Endoscopic Surgery) and LESS (Laparoendoscopic Single Site) procedures using MAGS instruments in porcine models with up to 2.5-cm-thick abdominal walls, but this distance may not be sufficient in some humans. The purpose of this study was to determine the maximal abdominal wall thickness for which the current MAGS platform is suitable. Successive iterations of prototype instruments were developed; those evaluated in this study include external (134-583 g, 38-61 mm diameter) and internal (8-39 g, 10-22 mm diameter) components using various grades, diameters, thicknesses, and stacking/shielding/focusing configurations of permanent Neodymium-iron-boron (NdFeB) magnets. Nine configurations were tested for coupling strength across distances of 0.1-10 cm. The force-distance tests across an air medium were conducted at 0.5-mm increments using a robotic arm fitted with a force sensor. A minimum theoretical instrument drop-off (decoupling) threshold was defined as the separation distance at which force decreased below the weight of the heaviest internal component (39 g). Magnetic attraction forces decreased exponentially over distance. For the nine configurations tested, the average forces were 3,334 ± 1,239 gf at 0.1 cm, 158 ± 98 gf at 2.5 cm, and 8.7 ± 12 gf at 5 cm; the drop-off threshold was 3.64 ± 0.8 cm. The larger stacking configurations and magnets yielded up to a 592% increase in attraction force at 2.5 cm and extended the drop-off threshold distance by up to 107% over single-stack anchors. For the strongest configuration, coupling force ranged from 5,337 gf at 0.1 cm to 0 gf at 6.95 cm and yielded a drop-off threshold distance of 4.78 cm. This study suggests that the strongest configuration of currently available MAGS instruments is suitable for clinically relevant abdominal wall thicknesses. Further platform development and optimization are warranted.

Prognostic value of high-dose dobutamine stress magnetic resonance imaging in 1,493 consecutive patients: assessment of myocardial wall motion and perfusion.

PubMed

Korosoglou, Grigorios; Elhmidi, Yacine; Steen, Henning; Schellberg, Dieter; Riedle, Nina; Ahrens, Johannes; Lehrke, Stephanie; Merten, Constanze; Lossnitzer, Dirk; Radeleff, Jannis; Zugck, Christian; Giannitsis, Evangelos; Katus, Hugo A

2010-10-05

This study sought to determine the prognostic value of wall motion and perfusion assessment during high-dose dobutamine stress (DS) cardiac magnetic resonance imaging (MRI) in a large patient cohort. DS-MRI offers the possibility to integrate myocardial perfusion and wall motion analysis in a single examination for the detection of coronary artery disease (CAD). A total of 1,493 consecutive patients with suspected or known CAD underwent DS-MRI, using a standard protocol in a 1.5-T magnetic resonance scanner. Wall motion and perfusion were assessed at baseline and during stress, and outcome data including cardiac death, nonfatal myocardial infarction ("hard events"), and "late" revascularization performed >90 days after the MR scans were collected during a 2 ± 1 year follow-up period. Fifty-three hard events, including 14 cardiac deaths and 39 nonfatal infarctions, occurred during the follow-up period, whereas 85 patients underwent "late" revascularization. Using multivariable regression analysis, an abnormal result for wall motion or perfusion during stress yielded the strongest independent prognostic value for both hard events and late revascularization, clearly surpassing that of clinical and baseline magnetic resonance parameters (for wall motion: adjusted hazard ratio [HR] of 5.9 [95% confidence interval (CI): 2.5 to 13.6] for hard events and of 3.1 [95% CI: 1.7 to 5.6] for late revascularization, and for perfusion: adjusted HR of 5.4 [95% CI: 2.3 to 12.9] for hard events and of 6.2 [95% CI: 3.3 to 11.3] for late revascularization, p < 0.001 for all). DS-MRI can accurately identify patients who are at increased risk for cardiac death and myocardial infarction, separating them from those with normal findings, who have very low risk for future cardiac events. (Prognostic Value of High Dose Dobutamine Stress Magnetic Resonance Imaging; NCT00837005). Copyright © 2010 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Indirect Coupling of Magnetic Layers via Domain Wall Fringing fields

NASA Astrophysics Data System (ADS)

Parkin, Stuart

2001-03-01

Ferromagnetic films separated by thin metallic spacer layers are usually coupled through an indirect exchange interaction which oscillates in sign between ferro and antiferromagnetic coupling as a function of the spacer layer thickness^1. For both such metallic systems, and for multilayered systems in which the ferromagnetic films are separated by thin insulating layers, correlated roughness of the magnetic layers gives rise to a weak ferromagnetic coupling via dipole fields. Another type of dipolar coupling mechanism, which has largely been ignored, is that arising from domain wall fringing fields. These fields can be locally very large^2 and can result in the demagnetization of ferromagnetic films which are nominally highly coercive ("hard") in sandwiches comprised of "hard" and "soft" ferromagnetic layers. When the moment of the soft layer is reversed back and forth in small magnetic fields, much too small to affect the moment of the hard layer, substantial local fringing fields from domain walls created in the soft film gradually result in the demagnetization of the hard film. In some cases the moment of the hard layer decays in an oscillatory manner as it is successively partially demagnetized and remagnetized. This process has been observed on both macroscopic and microscopic length scales using SQUID magnetometry and high resolution photoemission electron microscopy, respectively^3. Magnetic interactions from domain wall fringing fields may be very important for magnetic devices, especially, magnetoresistance sensors and memory elements. [1] S.S.P. Parkin, N. More and K.P. Roche, Phys. Rev. Lett. 64, 2304 (1990); S.S.P. Parkin, Phys. Rev. Lett., 67, 3598 (1991). [2] L. Thomas, M. Samant and S.S.P. Parkin, Phys. Rev. Lett. 84, 1816 (2000). [3] L. Thomas, J Lüning, A. Scholl, F. Nolting, S. Anders, J. Stöhr and S.S.P. Parkin, Phys. Rev. Lett. 84, 3462 (2000).

Integrated semiconductor-magnetic random access memory system

NASA Technical Reports Server (NTRS)

Katti, Romney R. (Inventor); Blaes, Brent R. (Inventor)

2001-01-01

The present disclosure describes a non-volatile magnetic random access memory (RAM) system having a semiconductor control circuit and a magnetic array element. The integrated magnetic RAM system uses CMOS control circuit to read and write data magnetoresistively. The system provides a fast access, non-volatile, radiation hard, high density RAM for high speed computing.

Preparation and characterization of SiO2-coated submicron-sized L10 Fe-Pt particles

NASA Astrophysics Data System (ADS)

Hayashi, Yoshiaki; Ogawa, Tomoyuki; Ishiyama, Kazushi

2018-05-01

The development of magnets with higher performance is attracting increasing interest. The optimization of their microstructure is essential to enhance their properties, and a microstructure comprising magnetically isolated hard magnetic grains of a single-domain size has been proposed as an ideal structure for enhancing the coercivity of magnets. To obtain magnets with an ideal structure, we consider the fabrication of magnets by an approach based on core/shell nanoparticles with a hard magnetic core and a non-magnetic shell. In this study, to obtain particles for our proposed approach, we attempted to fabricate L10 Fe-Pt/SiO2-core/shell particles with submicron-sized cores less than the critical single-domain size. The fabrication of such core/shell particles was confirmed from morphology observations and XRD analysis of the particles. Although the formation of more desirable core/shell particles with submicron-sized single-crystal cores in the single-domain size range was not achieved, the fabricated core/shell particles showed a high coercivity of 25 kOe.

A study of the physical properties of single crystalline Fe 5B 2P

DOE PAGES

Lamichhane, Tej N.; Taufour, Valentin; Thimmaiah, Srinivasa; ...

2015-10-24

Single crystals of Fe 5B 2P were grown by self-flux growth technique. Structural and electrical and magnetic anisotropic properties are studied. The Curie temperature of Fe5B2P is determined to be 655 ± 2 K. The saturation magnetization is determined to be 1.72μ B/Fe at 2 K. The temperature variation of the anisotropy constant K 1 is determined for the first time, reaching ~0.50MJ/m 3 at 2 K, and it is comparable to that of hard ferrites. The saturation magnetization is found to be larger than the hard ferrites. In conclusion, the first principle calculations of saturation magnetization and anisotropy constantmore » are found to be consistent with the experimental results.« less

Specific feature of magnetooptical images of stray fields of magnets of various geometrical shapes

NASA Astrophysics Data System (ADS)

Ivanov, V. E.; Koveshnikov, A. V.; Andreev, S. V.

2017-08-01

Specific features of magnetooptical images (MOIs) of stray fields near the faces of prismatic hard magnetic elements have been studied. Attention has primarily been focused on MOIs of fields near faces oriented perpendicular to the magnetic moment of hard magnetic elements. With regard to the polar sensitivity, MOIs have practically uniform brightness and geometrically they coincide with the figures of the bases of the elements. With regard to longitudinal sensitivity, MOIs consist of several sectors, the number of which is determined by the number of angles of the image. Each angle is divided by the bisectrix into two sectors of different brightnesses; therefore, the MOI of a triangular magnet consists of three sectors. A rectangle consists of four sectors separated by the bisectrices of the interior angles. In all types of figures, these lines converge at the center of the figure and form a singular point of the source or sink type.

Evolution of Large-Scale Magnetic Fields and State Transitions in Black Hole X-Ray Binaries

NASA Astrophysics Data System (ADS)

Wang, Ding-Xiong; Huang, Chang-Yin; Wang, Jiu-Zhou

2010-04-01

The state transitions of black hole (BH) X-ray binaries are discussed based on the evolution of large-scale magnetic fields, in which the combination of three energy mechanisms are involved: (1) the Blandford-Znajek (BZ) process related to the open field lines connecting a rotating BH with remote astrophysical loads, (2) the magnetic coupling (MC) process related to the closed field lines connecting the BH with its surrounding accretion disk, and (3) the Blandford-Payne (BP) process related to the open field lines connecting the disk with remote astrophysical loads. It turns out that each spectral state of the BH binaries corresponds to each configuration of magnetic field in BH magnetosphere, and the main characteristics of low/hard (LH) state, hard intermediate (HIM) state and steep power law (SPL) state are roughly fitted based on the evolution of large-scale magnetic fields associated with disk accretion.

Fesbnd X (X = B, N) binary compounds: First-principles calculations of electronic structures, theoretic hardness and magnetic properties

NASA Astrophysics Data System (ADS)

Hui, Liangliang; Xie, Zhongjing; Li, Chunmei; Chen, Zhi-Qian

2018-04-01

The first-principles calculations are implemented to investigate the electronic structures, theoretic hardness and magnetic properties of iron borides and nitrides with four different crystal systems containing hexagonal (FeB2, ε-Fe3N), tetragonal (Fe2B, α″-Fe16N2), orthorhombic (α-FeB, θ-Fe3B, ζ-Fe2N), and cubic (zb-FeN, rs-FeN, γ‧-Fe4N, γ-Fe23B6) phase. The calculated lattice parameters using RPBE meet well with the experimental results. The cohesive energy and formation enthalpy values indicate the Fesbnd X (X = B, N) binary compounds are thermodynamically stable. Meanwhile, the h-FeB2 is most difficult phase for experimental synthesis among these interstitial compounds. Moreover, magnetic properties are discussed and show that the mean magnetic moments of o-Fe3B and c-Fe23B6 with the values of 2.227 μB and 2.256 μB per iron atom are approaching to that of pure iron (2.32 μB) while the c-Fe4N and t-Fe16N2 with the values of 2.51 and 2.48 μB are beyond that of pure α-Fe. The c-FeN phase shows nonmagnetic in zb-style while rs-type shows antiferromagnetic with a value of 2.52 μB. Furthermore, the average bonding length and Mulliken population combined with electronic structures are also analysed in this paper which provide that strong Fesbnd X and Xsbnd X covalent bonds are responsible for high hardness. Finally, the theoretic hardness of Xsbnd X, Fesbnd X and Fesbnd Fe bonds is predicted by semi empirical hardness theory.

Modeling of non-ideal hard permanent magnets with an affine-linear model, illustrated for a bar and a horseshoe magnet

NASA Astrophysics Data System (ADS)

Glane, Sebastian; Reich, Felix A.; Müller, Wolfgang H.

2017-11-01

This study is dedicated to continuum-scale material modeling of isotropic permanent magnets. An affine-linear extension to the commonly used ideal hard model for permanent magnets is proposed, motivated, and detailed. In order to demonstrate the differences between these models, bar and horseshoe magnets are considered. The structure of the boundary value problem for the magnetic field and related solution techniques are discussed. For the ideal model, closed-form analytical solutions were obtained for both geometries. Magnetic fields of the boundary value problems for both models and differently shaped magnets were computed numerically by using the boundary element method. The results show that the character of the magnetic field is strongly influenced by the model that is used. Furthermore, it can be observed that the shape of an affine-linear magnet influences the near-field significantly. Qualitative comparisons with experiments suggest that both the ideal and the affine-linear models are relevant in practice, depending on the magnetic material employed. Mathematically speaking, the ideal magnetic model is a special case of the affine-linear one. Therefore, in applications where knowledge of the near-field is important, the affine-linear model can yield more accurate results—depending on the magnetic material.

Magnetic hardening of Ce 1+xFe 11–yCo yTi with ThMn 12 structure by melt spinning

DOE PAGES

Zhou, Chen; Sun, Kewei; Pinkerton, Frederick E.; ...

2015-04-15

A recent study on the intrinsic magnetic properties of CeFe 11–yCo yTi has revealed that substituting one Co for Fe retains the favorable magnetocrystalline anisotropy H a found in the ternary Fe end member, while enhancing the Curie temperature T c and saturation magnetization 4πM s. These findings warrant further optimization around Co substitution y = 1 to try to exploit the hard magnetic properties of these Ce-based magnets. Both Ce and Co concentrations in Ce 1+xFe 11–yCo yTi have been optimized in the range of x = 0 – 0.2 and y = 0 –1.5. It was found thatmore » Co substitution effectively enhances all hard magnetic properties, although the values are still lower than those predicted from the intrinsic magnetic properties. Specifically, T c increases from 210 °C to 285 – 350 °C; 4πM 19 (magnetization at 19 kOe) from 8.9 kG to 10.5 – 11.5 kG, remanence Br from 3.1 kG to 4.1 – 4.5 kG, and most importantly, H ci from 1.1 kOe to 1.5 kOe. As a result, the room temperature energy product (BH) max has been increased by over 100% from 0.7 MGOe in Ce 1.1Fe 11Ti to 1.5 MGOe in Ce 1.05Fe 9.75Co 1.25Ti. Microscopy analysis indicates that the addition of Co refines the grain size and promotes chemical homogeneity at the microscopic scale. As a result, the beneficial effect of Co on the microstructure contributes to the improved hard magnetic properties.« less

40 CFR 63.11995 - In what form and how long must I keep my records?

Code of Federal Regulations, 2013 CFR

2013-07-01

... years. Records may be maintained in hard copy or computer-readable format including, but not limited to, on paper, microfilm, hard disk drive, floppy disk, compact disk, magnetic tape or microfiche. ...

40 CFR 63.11995 - In what form and how long must I keep my records?

Code of Federal Regulations, 2014 CFR

2014-07-01

... years. Records may be maintained in hard copy or computer-readable format including, but not limited to, on paper, microfilm, hard disk drive, floppy disk, compact disk, magnetic tape or microfiche. ...

40 CFR 63.11995 - In what form and how long must I keep my records?

Code of Federal Regulations, 2012 CFR

2012-07-01

... years. Records may be maintained in hard copy or computer-readable format including, but not limited to, on paper, microfilm, hard disk drive, floppy disk, compact disk, magnetic tape or microfiche. ...

Effects of trace elements on the crystal field parameters of Nd ions at the surface of Nd{sub 2}Fe{sub 14}B grains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toga, Yuta; Suzuki, Tsuneaki; Sakuma, Akimasa, E-mail: sakuma@solid.apph.tohoku.ac.jp

2015-06-14

Using first-principles calculations, we investigate the positional dependence of trace elements such as O and Cu on the crystal field parameter A{sub 2}{sup 0}, proportional to the magnetic anisotropy constant K{sub u} of Nd ions placed at the surface of Nd{sub 2}Fe{sub 14}B grains. The results suggest the possibility that the A{sub 2}{sup 0} parameter of Nd ions at the (001) surface of Nd{sub 2}Fe{sub 14}B grains exhibits a negative value when the O or Cu atom is located near the surface, closer than its equilibrium position. At the (110) surface, however, O atoms located at the equilibrium position providemore » a negative A{sub 2}{sup 0}, while for Cu additions A{sub 2}{sup 0} remains positive regardless of Cu's position. Thus, Cu atoms are expected to maintain a positive local K{sub u} of surface Nd ions more frequently than O atoms when they approach the grain surfaces in the Nd-Fe-B grains.« less

Pancreatic hardness: Correlation of surgeon’s palpation, durometer measurement and preoperative magnetic resonance imaging features

PubMed Central

Hong, Tae Ho; Choi, Joon-Il; Park, Michael Yong; Rha, Sung Eun; Lee, Young Joon; You, Young Kyoung; Choi, Moon Hyung

2017-01-01

AIM To evaluate the correlation between subjective assessments of pancreatic hardness based on the palpation, objective measurements using a durometer, and magnetic resonance imaging (MRI) findings for assessing pancreatic hardness. METHODS Eighty-three patients undergoing pancreatectomies were enrolled. An experienced surgeon subjectively evaluated the pancreatic hardness in the surgical field by palpation. The pancreatic hardness was also objectively evaluated using a durometer. Preoperative MRI findings were evaluated by a radiologist in terms of the apparent diffusion coefficient (ADC) values, the relative signal intensity decrease (RSID) of the pancreatic parenchyma, and the diameter of the pancreatic parenchyma and duct. Durometer measurement results, ADC values, RSID, pancreatic duct and parenchyma diameters, and the ratio of the diameters of the duct and parenchyma were compared between pancreases judged to be soft or hard pancreas on the palpation. A correlation analysis was also performed between the durometer and MRI measurements. RESULTS The palpation assessment classified 44 patients as having a soft pancreas and 39 patients as having a hard pancreas. ADC values were significantly lower in the hard pancreas group. The ductal diameter and duct-to-pancreas ratio were significantly higher in the hard pancreas group. For durometer measurements, a correlation analysis showed a positive correlation with the ductal diameter and the duct-to-pancreas ratio and a negative correlation with ADC values. CONCLUSION Hard pancreases showed lower ADC values, a wider pancreatic duct diameter and a higher duct-to-pancreas ratio than soft pancreases. Additionally, the ADC values, diameter of the pancreatic duct and duct-to-pancreas ratio were closely correlated with the durometer results. PMID:28373771

Pancreatic hardness: Correlation of surgeon's palpation, durometer measurement and preoperative magnetic resonance imaging features.

PubMed

Hong, Tae Ho; Choi, Joon-Il; Park, Michael Yong; Rha, Sung Eun; Lee, Young Joon; You, Young Kyoung; Choi, Moon Hyung

2017-03-21

To evaluate the correlation between subjective assessments of pancreatic hardness based on the palpation, objective measurements using a durometer, and magnetic resonance imaging (MRI) findings for assessing pancreatic hardness. Eighty-three patients undergoing pancreatectomies were enrolled. An experienced surgeon subjectively evaluated the pancreatic hardness in the surgical field by palpation. The pancreatic hardness was also objectively evaluated using a durometer. Preoperative MRI findings were evaluated by a radiologist in terms of the apparent diffusion coefficient (ADC) values, the relative signal intensity decrease (RSID) of the pancreatic parenchyma, and the diameter of the pancreatic parenchyma and duct. Durometer measurement results, ADC values, RSID, pancreatic duct and parenchyma diameters, and the ratio of the diameters of the duct and parenchyma were compared between pancreases judged to be soft or hard pancreas on the palpation. A correlation analysis was also performed between the durometer and MRI measurements. The palpation assessment classified 44 patients as having a soft pancreas and 39 patients as having a hard pancreas. ADC values were significantly lower in the hard pancreas group. The ductal diameter and duct-to-pancreas ratio were significantly higher in the hard pancreas group. For durometer measurements, a correlation analysis showed a positive correlation with the ductal diameter and the duct-to-pancreas ratio and a negative correlation with ADC values. Hard pancreases showed lower ADC values, a wider pancreatic duct diameter and a higher duct-to-pancreas ratio than soft pancreases. Additionally, the ADC values, diameter of the pancreatic duct and duct-to-pancreas ratio were closely correlated with the durometer results.

Ground state of dipolar hard spheres confined in channels

NASA Astrophysics Data System (ADS)

Deißenbeck, Florian; Löwen, Hartmut; Oǧuz, Erdal C.

2018-05-01

We investigate the ground state of a classical two-dimensional system of hard-sphere dipoles confined between two hard walls. Using lattice sum minimization techniques we reveal that at fixed wall separations, a first-order transition from a vacuum to a straight one-dimensional chain of dipoles occurs upon increasing the density. Further increase in the density yields the stability of an undulated chain as well as nontrivial buckling structures. We explore the close-packed configurations of dipoles in detail, and we find that, in general, the densest packings of dipoles possess complex magnetizations along the principal axis of the slit. Our predictions serve as a guideline for experiments with granular dipolar and magnetic colloidal suspensions confined in slitlike channel geometry.

Manganese mono-boride, an inexpensive room temperature ferromagnetic hard material

PubMed Central

Ma, Shuailing; Bao, Kuo; Tao, Qiang; Zhu, Pinwen; Ma, Teng; Liu, Bo; Liu, Yazhou; Cui, Tian

2017-01-01

We synthesized orthorhombic FeB-type MnB (space group: Pnma) with high pressure and high temperature method. MnB is a promising soft magnetic material, which is ferromagnetic with Curie temperature as high as 546.3 K, and high magnetization value up to 155.5 emu/g, and comparatively low coercive field. The strong room temperature ferromagnetic properties stem from the positive exchange-correlation between manganese atoms and the large number of unpaired Mn 3d electrons. The asymptotic Vickers hardness (AVH) is 15.7 GPa which is far higher than that of traditional ferromagnetic materials. The high hardness is ascribed to the zigzag boron chains running through manganese lattice, as unraveled by X-ray photoelectron spectroscopy result and first principle calculations. This exploration opens a new class of materials with the integration of superior mechanical properties, lower cost, electrical conductivity, and fantastic soft magnetic properties which will be significant for scientific research and industrial application as advanced structural and functional materials. PMID:28262805

Vacuum nonlinear electrodynamic polarization effects in hard emission of pulsars and magnetars

NASA Astrophysics Data System (ADS)

Denisov, V. I.; Sokolov, V. A.; Svertilov, S. I.

2017-09-01

The nonlinear electrodynamics influence of pulsar magnetic field on the electromagnetic pulse polarization is discussed from the point of observation interpretation. The calculations of pulsar magnetic field impact on the electromagnetic pulse polarization are made in such a way to make it easier to interpret these effects in space experiments. The law of hard emission pulse propagation in the pulsar magnetic field according to the vacuum (nonlinear electrodynamics is obtained. It has been shown, that due to the birefringence in the vacuum the front part of any hard emission pulse coming from a pulsar should be linearly polarized and the rest of pulse can have arbitrary polarization. The observational possibilities of vacuum birefringence are discussed. In this paper we give the estimations of detector parameters such as effective area, exposure time and necessity of polarization measurements with high accuracy. The combination of large area and extremely long exposure time gives the good opportunity to search the fine polarization effects like vacuum nonlinear electrodynamics birefringence.

Vacuum nonlinear electrodynamic polarization effects in hard emission of pulsars and magnetars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denisov, V.I.; Sokolov, V.A.; Svertilov, S.I., E-mail: vid.msu@yandex.ru, E-mail: sokolov.sev@inbox.ru, E-mail: sis@coronas.ru

The nonlinear electrodynamics influence of pulsar magnetic field on the electromagnetic pulse polarization is discussed from the point of observation interpretation. The calculations of pulsar magnetic field impact on the electromagnetic pulse polarization are made in such a way to make it easier to interpret these effects in space experiments. The law of hard emission pulse propagation in the pulsar magnetic field according to the vacuum (nonlinear electrodynamics is obtained. It has been shown, that due to the birefringence in the vacuum the front part of any hard emission pulse coming from a pulsar should be linearly polarized and themore » rest of pulse can have arbitrary polarization. The observational possibilities of vacuum birefringence are discussed. In this paper we give the estimations of detector parameters such as effective area, exposure time and necessity of polarization measurements with high accuracy. The combination of large area and extremely long exposure time gives the good opportunity to search the fine polarization effects like vacuum nonlinear electrodynamics birefringence.« less

40 CFR 63.9060 - In what form and how long must I keep my records?

Code of Federal Regulations, 2010 CFR

2010-07-01

... may be maintained in hard copy or computer-readable format including, but not limited to, on paper, microfilm, hard disk drive, floppy disk, compact disk, magnetic tape, or microfiche. (d) You must keep each...

Spectral and Timing Investigations of Dwarf Novae Selected in Hard X-Rays

NASA Technical Reports Server (NTRS)

Thorstensen, John; Remillard, Ronald A.

2000-01-01

There are 9 dwarf novae (DN) among the 43 cataclysmic variables (accreting white dwarfs in close binary systems) that were detected during the HEAO-1 all-sky X-ray survey (1977-1979). On the other hand, there are roughly one hundred dwarf novae that are closer and/or optically brighter and yet they were not detected as hard X-ray sources. Two of the HEAO-1 DN show evidence for X-ray pulsations that imply strong magnetic fields on the white dwarf surface, and magnetic CVs are known to be strong X-ray sources. However, substantial flux in hard X-rays may be caused by non-magnetic effects, such as an optically thin boundary layer near a massive white dwarf. We proposed RXTE observations to measure plasma temperatures and to search for X-ray pulsations. The observations would distinguish whether these DN belong to one of (rare) magnetic subclasses. For those that do not show pulsations, the observations support efforts to define empirical relations between X-ray temperature, the accretion rate, and the mass of the white dwarf. The latter is determined via optical studies of the dynamics of the binary constituents.

Exchange coupling and microwave absorption in core/shell-structured hard/soft ferrite-based CoFe2O4/NiFe2O4 nanocapsules

NASA Astrophysics Data System (ADS)

Feng, Chao; Liu, Xianguo; Or, Siu Wing; Ho, S. L.

2017-05-01

Core/shell-structured, hard/soft spinel-ferrite-based CoFe2O4/NiFe2O4 (CFO/NFO) nanocapsules with an average diameter of 17 nm are synthesized by a facile two-step hydrothermal process using CFO cores of ˜15 nm diameter as the hard magnetic phase and NFO shells of ˜1 nm thickness as the soft magnetic phase. The single-phase-like hysteresis loop with a high remnant-to-saturation magnetization ratio of 0.7, together with a small grain size of ˜16 nm, confirms the existence of exchange-coupling interaction between the CFO cores and the NFO shells. The effect of hard/soft exchange coupling on the microwave absorption properties is studied. Comparing to CFO and NFO nanoparticles, the finite-size NFO shells and the core/shell structure enable a significant reduction in electric resistivity and an enhancement in dipole and interfacial polarizations in the CFO/NFO nanocapsules, resulting in an obvious increase in dielectric permittivity and loss in the whole S-Ku bands of microwaves of 2-18 GHz, respectively. The exchange-coupling interaction empowers a more favorable response of magnetic moment to microwaves, leading to enhanced exchange resonances in magnetic permeability and loss above 10 GHz. As a result, strong absorption, as characterized by a large reflection loss (RL) of -20.1 dB at 9.7 GHz for an absorber thickness of 4.5 mm as well as a broad effective absorption bandwidth (for RL<-10 dB) of 8.4 GHz (7.8-16.2 GHz) at an absorber thickness range of 3.0-4.5 mm, is obtained.

Crystal structure, magnetic properties and advances in hexaferrites: A brief review

NASA Astrophysics Data System (ADS)

Jotania, Rajshree

2014-10-01

Hexaferrites are hard magnetic materials and specifically ferri-magnetic oxides with hexagonal magnetoplumbite type crystallographic structure. Hexagonal ferrites are used as permanent magnets, high-density perpendicular and magneto-optical recording media, and microwave devices like resonance isolators, filters, circulators, phase shifters because of their high magnetic permeability, high electrical resistivity and moderable permittivity. In addition to these; hexagonal ferrites have excellent chemical stability, mechanical hardness and low eddy current loss at high frequencies. The preparation of hexaferrites is a complicated process. Various experimental techniques like standard ceramic techniques, solvent free synthesis route, co precipitation, salt-melt, ion exchange, sol-gel, citrate synthesis, hydrothermal synthesis, spray drying, water-in-oil microemulsion, reverse micelle etc are used to prepare hexaferrite materials. Structural, dielectric and magnetic properties, crystallite size of hexaferrites depend upon nature of substituted ions, method of preparation, sintering temperature and time. The recent interest is nanotechnology, the development of hexaferrite fibres and composites with carbon nano tubes (CNT). Magnetic properties of some doped and un-doped hexaferrites are discussed here. Recent advances in hexaferrites also highlighted in present paper.

Magnetic-field sensing coil embedded in ceramic for measuring ambient magnetic field

DOEpatents

Takahashi, Hironori

2004-02-10

A magnetic pick-up coil for measuring magnetic field with high specific sensitivity, optionally with an electrostatic shield (24), having coupling elements (22) with high winding packing ratio, oriented in multiple directions, and embedded in ceramic material for structural support and electrical insulation. Elements of the coil are constructed from green ceramic sheets (200) and metallic ink deposited on surfaces and in via holes of the ceramic sheets. The ceramic sheets and the metallic ink are co-fired to create a monolithic hard ceramic body (20) with metallized traces embedded in, and placed on exterior surfaces of, the hard ceramic body. The compact and rugged coil can be used in a variety of environments, including hostile conditions involving ultra-high vacuum, high temperatures, nuclear and optical radiation, chemical reactions, and physically demanding surroundings, occurring either individually or in combinations.

Characterization of aging-induced microstructural changes in M250 maraging steel using magnetic parameters

NASA Astrophysics Data System (ADS)

Rajkumar, K. V.; Vaidyanathan, S.; Kumar, Anish; Jayakumar, T.; Raj, Baldev; Ray, K. K.

2007-05-01

The best combinations of mechanical properties (yield stress and fracture toughness) of M250 maraging steel is obtained through short-term thermal aging (3-10 h) at 755 K. This is attributed to the microstructure containing precipitation of intermetallic phases in austenite-free low-carbon martensite matrix. Over-aged microstructure, containing reverted austenite degrades the mechanical properties drastically. Hence, it necessitates identification of a suitable non-destructive evaluation (NDE) technique for detecting any reverted austenite unambiguously during aging. The influence of aging on microstructure, room temperature hardness and non-destructive magnetic parameters such as coercivity ( Hc), saturation magnetization ( Ms) and magnetic Barkhausen emission (MBE) RMS peak voltage is studied in order to derive correlations between these parameters in aged M250 maraging steel. Hardness was found to increase with precipitation of intermetallics during initial aging and decrease at longer durations due to austenite reversion. Among the different magnetic parameters studied, MBE RMS peak voltage was found to be very sensitive to austenite reversion (non-magnetic phase) as they decreased drastically up on initiation of austenite reversion. Hence, this parameter can be effectively utilized to detect and quantify the reverted austenite in maraging steel specimen. The present study clearly indicates that the combination of MBE RMS peak voltage and hardness can be used for unambiguous characterization of microstructural features of technological and practical importance (3-10 h of aging duration at 755 K) in M250 grade maraging steel.

High Temperature Texturing of Engineered Materials in a Magnetic Field

DTIC Science & Technology

2003-03-01

by 43.7 % after magnetic annealing in a 19 T field. The kink at the demagnetization curve disappeared and, in addition, a much better squareness of...the demagnetization curves was observed after the magnetic annealing (Figure 10). The improvement in the hard magnetic properties after magnetic ...A number of materials systems have been tested in a variety of magnetic fields (8-20 Tesla) and temperatures (500 to 1250oC). Four materials

Bringing Science Research into Secondary Schools

ERIC Educational Resources Information Center

Allwood, Dan A.; Dean, Julian; Bryan, Matthew T.; Baker, Alan

2009-01-01

Finite element modelling software has been used to allow secondary school students to study nanoscale magnetic materials for hard drive recording applications. The students were introduced to the basic concepts of finite element modelling using a freely available internet game before modelling the magnetization reversal of single magnetic grains.…

Disposal of waste computer hard disk drive: data destruction and resources recycling.

PubMed

Yan, Guoqing; Xue, Mianqiang; Xu, Zhenming

2013-06-01

An increasing quantity of discarded computers is accompanied by a sharp increase in the number of hard disk drives to be eliminated. A waste hard disk drive is a special form of waste electrical and electronic equipment because it holds large amounts of information that is closely connected with its user. Therefore, the treatment of waste hard disk drives is an urgent issue in terms of data security, environmental protection and sustainable development. In the present study the degaussing method was adopted to destroy the residual data on the waste hard disk drives and the housing of the disks was used as an example to explore the coating removal process, which is the most important pretreatment for aluminium alloy recycling. The key operation points of the degaussing determined were: (1) keep the platter plate parallel with the magnetic field direction; and (2) the enlargement of magnetic field intensity B and action time t can lead to a significant upgrade in the degaussing effect. The coating removal experiment indicated that heating the waste hard disk drives housing at a temperature of 400 °C for 24 min was the optimum condition. A novel integrated technique for the treatment of waste hard disk drives is proposed herein. This technique offers the possibility of destroying residual data, recycling the recovered resources and disposing of the disks in an environmentally friendly manner.

Nanoindentation hardness of particles used in magnetorheological finishing (MRF).

PubMed

Shorey, A B; Kwong, K M; Johnson, K M; Jacobs, S D

2000-10-01

Knowledge of the hardness of abrasive particles that are used in polishing is a key to the fundamental understanding of the mechanisms of material removal. The magnetorheological-finishing process uses both magnetic and nonmagnetic abrasive particles during polishing. The nanohardnesses of the micrometer-sized magnetic carbonyl iron and nonmagnetic abrasive particles have been measured successfully by use of novel, to our knowledge, sample-preparation and nanoindentation techniques. Some of the results reported compare favorably with existing microhardness data found in the literature, whereas other results are new.

Dispersive admicelle solid-phase extraction based on sodium dodecyl sulfate coated Fe3 O4 nanoparticles for the selective adsorption of three alkaloids in Gegen-Qinlian oral liquid before high-performance liquid chromatography.

PubMed

Shi, Zhihong; Xu, Dan; Zhao, Xuan; Li, Xinghong; Shen, Huimin; Yang, Bing; Zhang, Hongyi

2017-12-01

A novel dispersive admicelle solid-phase extraction method based on sodium dodecyl sulfate-coated Fe 3 O 4 nanoparticles was developed for the selective adsorption of berberine, coptisine, and palmatine in Gegen-Qinlian oral liquid before high-performance liquid chromatography. Fe 3 O 4 nanoparticles were synthesized by a chemical coprecipitation method and characterized by using transmission electron microscopy. Under acidic conditions, the surface of Fe 3 O 4 nanoparticles was coated with sodium dodecyl sulfate to form a nano-sized admicelle magnetic sorbent. Owing to electrostatic interaction, the alkaloids were adsorbed onto the oppositely charged admicelle magnetic nanoparticles. The quick separation of the analyte-adsorbed nanoparticles from the sample solution was performed by using Nd-Fe-B magnet. Best extraction efficiency was achieved under the following conditions: 800 μL Fe 3 O 4 nanoparticles suspension (20 mg/mL), 150 μL sodium dodecyl sulfate solution (10 mg/mL), pH 2, and vortexing time 2 min for the extraction of alkaloids from 10 mL of diluted sample. Four hundred microliters of methanol was used to desorb the alkaloids by vortexing for 1 min. Satisfactory extraction recoveries were obtained in the range of 85.9-120.3%, relative standard deviations for intra- and interday precisions were less than 6.3 and 10.0%, respectively. Finally, the established method was successfully applied to analyze the alkaloids in two batches of Gegen-Qinlian oral liquids. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnetic properties of doped Mn-Ga alloys made by mechanical milling and heat treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Daniel R.; National High Magnetic Field Laboratory, Tallahassee, FL 32310; Han, Ke

2016-05-15

Mn-Ga alloys have shown hard magnetic properties, even though these alloys contain no rare-earth metals. However, much work is needed before rare-earth magnets can be replaced. We have examined the magnetic properties of bulk alloys made with partial replacement of both the Mn and Ga elements in the Mn{sub 0.8}Ga{sub 0.2} system. Bulk samples of Mn-Ga-Bi, Mn-Ga-Al, Mn-Fe-Ga and Mn-(FeB)-Ga alloys were fabricated and studied using mechanically milling and heat treatments while altering the atomic percentage of the third element between 2.5 and 20 at%. The ternary alloy exhibits all hard magnetic properties at room temperature with large coercivity. Annealedmore » Mn-Ga-X bulk composites exhibit high coercivities up to 16.6 kOe and remanence up to 9.8 emu/g, that is increased by 115% over the binary system.« less

Magnetic properties and effect of pressure on the electronic state of EuCo2Ge2

NASA Astrophysics Data System (ADS)

Ashitomi, Y.; Kakihana, M.; Honda, F.; Nakamura, A.; Aoki, D.; Uwatoko, Y.; Nakashima, M.; Amako, Y.; Takeuchi, T.; Kida, T.; Tahara, T.; Hagiwara, M.; Haga, Y.; Hedo, M.; Nakama, T.; Ōnuki, Y.

2018-05-01

EuCo2Ge2 with the tetragonal structure is a Eu-divalent antiferromagnet with the Néel temperature TN = 23 K. The magnetic easy-axis corresponds to the [100] direction (a-axis), while the [001] direction (c-axis) is a hard-axis. The magnetization for H∥ [ 100 ] indicates a metamagnetic transition at 25 kOe and saturates above 75 kOe. On the other hand, the hard-axis magnetization increases approximately linearly and saturates above 110 kOe. The magnetic phase diagram was constructed. A characteristic feature in EuCo2Ge2 is known as a valence transition under pressure, from Eu 2+δ to Eu 3 - δ ‧(δ, δ ‧ < 1). We also clarified the valence transition by measuring the electrical resistivity under pressure. The valence transition occurs at 3 GPa, with a hysteresis, and terminates at about 4.5 GPa. Further increasing pressure, the electronic state is changed into a moderate heavy fermion state and approaches the nearly trivalent electronic state.

A magnetic model for low/hard state of black hole binaries

NASA Astrophysics Data System (ADS)

Ye, Yong-Chun; Wang, Ding-Xiong; Huang, Chang-Yin; Cao, Xiao-Feng

2016-03-01

A magnetic model for the low/hard state (LHS) of two black hole X-ray binaries (BHXBs), H1743-322 and GX 339-4, is proposed based on transport of the magnetic field from a companion into an accretion disk around a black hole (BH). This model consists of a truncated thin disk with an inner advection-dominated accretion flow (ADAF). The spectral profiles of the sources are fitted in agreement with the data observed at four different dates corresponding to the rising phase of the LHS. In addition, the association of the LHS with a quasi-steady jet is modeled based on transport of magnetic field, where the Blandford-Znajek (BZ) and Blandford-Payne (BP) processes are invoked to drive the jets from BH and inner ADAF. It turns out that the steep radio/X-ray correlations observed in H1743-322 and GX 339-4 can be interpreted based on our model.

Impact of radius and skew angle on areal density in heat assisted magnetic recording hard disk drives

NASA Astrophysics Data System (ADS)

Cordle, Michael; Rea, Chris; Jury, Jason; Rausch, Tim; Hardie, Cal; Gage, Edward; Victora, R. H.

2018-05-01

This study aims to investigate the impact that factors such as skew, radius, and transition curvature have on areal density capability in heat-assisted magnetic recording hard disk drives. We explore a "ballistic seek" approach for capturing in-situ scan line images of the magnetization footprint on the recording media, and extract parametric results of recording characteristics such as transition curvature. We take full advantage of the significantly improved cycle time to apply a statistical treatment to relatively large samples of experimental curvature data to evaluate measurement capability. Quantitative analysis of factors that impact transition curvature reveals an asymmetry in the curvature profile that is strongly correlated to skew angle. Another less obvious skew-related effect is an overall decrease in curvature as skew angle increases. Using conventional perpendicular magnetic recording as the reference case, we characterize areal density capability as a function of recording position.

Combining hard and soft magnetism into a single core-shell nanoparticle to achieve both hyperthermia and image contrast

PubMed Central

Yang, Qiuhong; Gong, Maogang; Cai, Shuang; Zhang, Ti; Douglas, Justin T; Chikan, Viktor; Davies, Neal M; Lee, Phil; Choi, In-Young; Ren, Shenqiang; Forrest, M Laird

2015-01-01

Background A biocompatible core/shell structured magnetic nanoparticles (MNPs) was developed to mediate simultaneous cancer therapy and imaging. Methods & results A 22-nm MNP was first synthesized via magnetically coupling hard (FePt) and soft (Fe3O4) materials to produce high relative energy transfer. Colloidal stability of the FePt@Fe3O4 MNPs was achieved through surface modification with silane-polyethylene glycol (PEG). Intravenous administration of PEG-MNPs into tumor-bearing mice resulted in a sustained particle accumulation in the tumor region, and the tumor burden of treated mice was a third that of the mice in control groups 2 weeks after a local hyperthermia treatment. In vivo magnetic resonance imaging exhibited enhanced T2 contrast in the tumor region. Conclusion This work has demonstrated the feasibility of cancer theranostics with PEG-MNPs. PMID:26606855

Thermal annealing and transient electronic excitations induced interfacial and magnetic effects on Pt/Co/Pt trilayer

NASA Astrophysics Data System (ADS)

Sehdev, Neeru; Medwal, Rohit; Malik, Rakesh; Kandasami, Asokan; Kanjilal, Dinakar; Annapoorni, S.

2018-04-01

Present study investigates the importance of thermal annealing and transient electronic excitations (using 100 MeV oxygen ions) in assisting the interfacial atomic diffusion, alloy composition, and magnetic switching field distributions in Pt/Co/Pt stacked trilayer. X-ray diffraction analysis reveals that thermal annealing results in the formation of the face centered tetragonal L1°CoPt phase. The Rutherford back scattering spectra shows a trilayer structure for as-deposited and as-irradiated films. Interlayer mixing on the thermally annealed films further improves by electronic excitations produced by high energy ion irradiation. Magnetically hard face centered tetragonal CoPt alloy retains its hard phase after ion irradiation and reveals an enhancement in the structural ordering and magnetic stability. Enhancement in the homogeneity of alloy composition and its correlation with the magnetic switching field is evident from this study. A detailed investigation of the contributing parameters shows that the magnetic switching behaviour varies with the type of thermal annealing, transient electronic excitations of ion beams and combination of these processes.

Magnetic exchange bias of more than 1 Tesla in a natural mineral intergrowth.

PubMed

McEnroe, Suzanne A; Carter-Stiglitz, Brian; Harrison, Richard J; Robinson, Peter; Fabian, Karl; McCammon, Catherine

2007-10-01

Magnetic exchange bias is a phenomenon whereby the hysteresis loop of a 'soft' magnetic phase is shifted by an amount H(E) along the applied field axis owing to its interaction with a 'hard' magnetic phase. Since the discovery of exchange bias fifty years ago, the development of a general theory has been hampered by the uncertain nature of the interfaces between the hard and soft phases, commonly between an antiferromagnetic phase and a ferro- or ferrimagnetic phase. Exchange bias continues to be the subject of investigation because of its technological applications and because it is now possible to manipulate magnetic materials at the nanoscale. Here we present the first documented example of exchange bias of significant magnitude (>1 T) in a natural mineral. We demonstrate that exchange bias in this system is due to the interaction between coherently intergrown magnetic phases formed through a natural process of phase separation during slow cooling over millions of years. Transmission electron microscopy studies show that these intergrowths have a known crystallographic orientation with a known crystallographic structure and that the interfaces are coherent.

Synthesis and magnetic properties of cobalt-iron/cobalt-ferrite soft/hard magnetic core/shell nanowires

NASA Astrophysics Data System (ADS)

Leandro Londoño-Calderón, César; Moscoso-Londoño, Oscar; Muraca, Diego; Arzuza, Luis; Carvalho, Peterson; Pirota, Kleber Roberto; Knobel, Marcelo; Pampillo, Laura Gabriela; Martínez-García, Ricardo

2017-06-01

A straightforward method for the synthesis of CoFe2.7/CoFe2O4 core/shell nanowires is described. The proposed method starts with a conventional pulsed electrodeposition procedure on alumina nanoporous template. The obtained CoFe2.7 nanowires are released from the template and allowed to oxidize at room conditions over several weeks. The effects of partial oxidation on the structural and magnetic properties were studied by x-ray spectrometry, magnetometry, and scanning and transmission electron microscopy. The results indicate that the final nanowires are composed of 5 nm iron-cobalt alloy nanoparticles. Releasing the nanowires at room conditions promoted surface oxidation of the nanoparticles and created a CoFe2O4 shell spinel-like structure. The shell avoids internal oxidation and promotes the formation of bi-magnetic soft/hard magnetic core/shell nanowires. The magnetic properties of both the initial single-phase CoFe2.7 nanowires and the final core/shell nanowires, reveal that the changes in the properties from the array are due to the oxidation more than effects associated with released processes (disorder and agglomeration).

Synthesis and magnetic properties of cobalt-iron/cobalt-ferrite soft/hard magnetic core/shell nanowires.

PubMed

Londoño-Calderón, César Leandro; Moscoso-Londoño, Oscar; Muraca, Diego; Arzuza, Luis; Carvalho, Peterson; Pirota, Kleber Roberto; Knobel, Marcelo; Pampillo, Laura Gabriela; Martínez-García, Ricardo

2017-06-16

A straightforward method for the synthesis of CoFe 2.7 /CoFe 2 O 4 core/shell nanowires is described. The proposed method starts with a conventional pulsed electrodeposition procedure on alumina nanoporous template. The obtained CoFe 2.7 nanowires are released from the template and allowed to oxidize at room conditions over several weeks. The effects of partial oxidation on the structural and magnetic properties were studied by x-ray spectrometry, magnetometry, and scanning and transmission electron microscopy. The results indicate that the final nanowires are composed of 5 nm iron-cobalt alloy nanoparticles. Releasing the nanowires at room conditions promoted surface oxidation of the nanoparticles and created a CoFe 2 O 4 shell spinel-like structure. The shell avoids internal oxidation and promotes the formation of bi-magnetic soft/hard magnetic core/shell nanowires. The magnetic properties of both the initial single-phase CoFe 2.7 nanowires and the final core/shell nanowires, reveal that the changes in the properties from the array are due to the oxidation more than effects associated with released processes (disorder and agglomeration).

Influence of samarium substitution on the structural and magnetic properties of M-type hexagonal ferrites

NASA Astrophysics Data System (ADS)

Yasmin, Nazia; Mirza, Misbah; Muhammad, Safdar; Zahid, Maria; Ahmad, Mukhtar; Awan, M. S.; Muhammad, Altaf

2018-01-01

The M-type hexagonal ferrites with chemical formula SrFe12-xSmxO19 (x = 0, 0.01, 0.02, 0.03) were synthesized via sol-gel method. We studied the effects of substitution of rare earth on the structural and magnetic temperament of M-type hexaferrites. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) strategies are employed for the systematical examination of micrographs and structures of the samples. The magnetic particularities are studied by the use of vibrating sample magnetometery. The M-H loops are used to investigate the hard magnetic behavior of all the samples. The substantial value of coercivity (>1 kOe) for all the samples shows that the particular sample is permanent magnet and reveals the hard magnetic action. It is observed that values of saturation magnetization (Mr) and remanence (Ms) decline with increasing the rare earth ions substitution. This decrease may follow spin canting and the magnetic dilution, which results in dislocation of superexchange interactions. The improvement in Hc may be because of large anisotropy of magnetocrystalline, where ion anisotropy of Fe2+ ion on the 2a site probably overriding in all hexaferrites series. The synthesized composites were useful for applications in magnetic microwave absorbing materials.

LC and ferromagnetic resonance in soft/hard magnetic microwires

NASA Astrophysics Data System (ADS)

Tian, Bin; Vazquez, Manuel

2015-12-01

The magnetic behavior of soft/hard biphase microwires is introduced here. The microwires consist of a Co59.1Fe14.8Si10.2B15.9 soft magnetic nucleus and a Co90Ni10 hard outer shell separated by an intermediate insulating Pyrex glass microtube. By comparing the resistance spectrums of welding the ends of metallic core (CC) or welding the metallic core and outer shell (CS) to the connector, it is found that one of the two peaks in the resistance spectrum is because the LC resonance depends on the inductor and capacitors in which one is the capacitor between the metallic core and outer shell, and the other is between the outer shell and connector. Correspondingly, another peak is for the ferromagnetic resonance of metallic core. After changing the capacitance of the capacitors, the frequency of LC resonance moves to high frequency band, and furthermore, the peak of LC resonance in the resistance spectrum disappeared. These magnetostatically coupled biphase systems are thought to be of large potential interest as sensing elements in sensor devices.

Periodically microstructured composite films made by electric- and magnetic-directed colloidal assembly

PubMed Central

Demirörs, Ahmet Faik; Courty, Diana; Libanori, Rafael; Studart, André R.

2016-01-01

Living organisms often combine soft and hard anisotropic building blocks to fabricate composite materials with complex microstructures and outstanding mechanical properties. An optimum design and assembly of the anisotropic components reinforces the material in specific directions and sites to best accommodate multidirectional external loads. Here, we fabricate composite films with periodic modulation of the soft–hard microstructure by simultaneously using electric and magnetic fields. We exploit forefront directed-assembly approaches to realize highly demanded material microstructural designs and showcase a unique example of how one can bridge colloidal sciences and composite technology to fabricate next-generation advanced structural materials. In the proof-of-concept experiments, electric fields are used to dictate the position of the anisotropic particles through dielectrophoresis, whereas a rotating magnetic field is used to control the orientation of the particles. By using such unprecedented control over the colloidal assembly process, we managed to fabricate ordered composite microstructures with up to 2.3-fold enhancement in wear resistance and unusual site-specific hardness that can be locally modulated by a factor of up to 2.5. PMID:27071113

Precessional Switching of Thin Nanomagnets with Uniaxial Anisotropy

NASA Astrophysics Data System (ADS)

Devolder, Thibaut; Schumacher, Hans Werner; Chappert, Claude

This review describes the evolution of the magnetization of uniaxial thin magnets when subjected to fast-rising magnetic-field pulses. We report detailed "all-electrical" experimental investigations of precessional switching on soft uniaxial micrometer-sized thin magnets, and we discuss them using a comprehensive, mostly analytical framework. General criteria are derived for the analytical assessment of the switching ability of any arbitrary set of experimental parameters. For this, we start from the Landau-Lifshitz equation and first consider the precessional switching in a much idealized macrospin, easy-plane loss-free system. We then test the main outputs of this model with time-resolved experiments on advanced Magnetic Random Access Memories (MRAM) cells. Using applied fields above the anisotropy field H k , we prove the quasiperiodic nature of the magnetization trajectory and we demonstrate experimental conditions ensuring a sub-200 ps ballistic magnetization reversal. We then upgrade our model accuracy by taking into account the uniaxial anisotropy and the behavior in hard-axis fields of the order of H k . We derive a simple though reliable estimate of the switching speed; its limiting factors highlight the experimental poor switching reproducibility when close to the minimal hard-axis reversal field H k /2. The latter field does not correspond to the minimal energy cost of the reversal, whose prospective evolution in the future generations of MRAM is predicted. Small departures from the macrospin state are discussed. The effect of damping is modeled using perturbation theory. Finite damping alters the precessional motion periodicity and puts some constraints on the field rise time. A special focus is dedicated to the relaxation-dominated precessional switching: the minimal hard-axis field triggering the switching is shown to be above H k /2 by an extra field cost linked to the damping constant times the square root of M S H k . Finally, the selective addressing and the direct-write of a magnetic cell with combined easy-axis and hard-axis fields are studied. We introduce the concept of bounce and revisit the dynamical astroid to derive the related characteristic reversal durations and their margins. We propose a field timing that is immune to the delay jitter between the combined addressing fields. We finish by investigating briefly the challenges and the promises of the "precessional" strategy for future MRAM generations.

Young Stellar Objects from Soft to Hard X-rays

NASA Astrophysics Data System (ADS)

Güdel, Manuel

2009-05-01

Magnetically active stars are the sites of efficient particle acceleration and plasma heating, processes that have been studied in detail in the solar corona. Investigation of such processes in young stellar objects is much more challenging due to various absorption processes. There is, however, evidence for violent magnetic energy release in very young stellar objects. The impact on young stellar environments (e.g., circumstellar disk heating and ionization, operation of chemical networks, photoevaporation) may be substantial. Hard X-ray devices like those carried on Simbol-X will establish a basis for detailed studies of these processes.

Magnetic catalysis and inverse magnetic catalysis in (2 +1 )-dimensional gauge theories from holographic models

NASA Astrophysics Data System (ADS)

Rodrigues, Diego M.; Capossoli, Eduardo Folco; Boschi-Filho, Henrique

2018-06-01

We study the deconfinement phase transition in (2 +1 )-dimensional holographic S U (N ) gauge theories in the presence of an external magnetic field from the holographic hard and soft wall models. We obtain exact solutions for the critical temperature of the deconfinement transition for any range of magnetic field. As a consequence, we find a critical magnetic field (Bc), in which the critical temperature (Tc) vanishes; for B Bc we have a magnetic catalysis.

Optical Characterization of Pulse Laser Deposition of Thin Film of Hard Materials Using RHEED and AFM Techniques (DURIP)

DTIC Science & Technology

2011-09-26

determine g-factor of the atomic system, it is convenient experimentally to fix 0 and to find the resonance magnetic field Hres corresponding to the...given frequency ( Hres = res/). In ferromagnetic materials, there exist strong internal anisotropic magnetic fields, which are caused by the magnetic

Effect of crystallization annealing under loading on the magnetic properties and the structure of a soft magnetic FeSiNbCuB alloy doped with chromium

NASA Astrophysics Data System (ADS)

Ershov, N. V.; Fedorov, V. I.; Chernenkov, Yu. P.; Lukshina, V. A.; Shishkin, D. A.

2017-09-01

The changes of quasi-static magnetic hysteresis loops and X-ray diffraction patterns of the Fe73.5Si13.5B9Nb3Cu1 doped to 10 at % chromium instead of iron have been studied to elucidate the influence of the thermomechanical treatment consisting of annealing and cooling of the alloy under the tensile stress (tensile-stress annealing (TSA)) on the magnetic properties and the structure of these alloys. It is shown that the treatment results in the induction of the magnetic anisotropy of the hard axis type at which the magnetization reversal along the direction of applying the external stress during annealing is hampered. The energy of the induced magnetic anisotropy decreases as the chromium content increases. During TSA, the nanocrystal lattices are deformed, and the deformation is retained after cooling. The interplanar spacings increase along the extension direction and decrease in the transverse direction. The deformation anisotropy is observed for crystallographic directions. The anisotropic deformation of the bcc lattice of nanocrystals with high content of the ordered Fe3Si phase characterized by a negative magnetoelastic interaction is the cause of formation of the state with the transverse magnetic anisotropy of the hard axis type.

Vectorial magnetometry with the magneto-optic Kerr effect applied to Co/Cu/Co trilayer structures

NASA Astrophysics Data System (ADS)

Daboo, C.; Bland, J. A. C.; Hicken, R. J.; Ives, A. J. R.; Baird, M. J.; Walker, M. J.

1993-05-01

We describe an arrangement in which the magnetization components parallel and perpendicular to the applied field are both determined from longitudinal magneto-optic Kerr effect measurements. This arrangement differs from the usual procedures in that the same optical geometry is used but the magnet geometry altered. This leads to two magneto-optic signals which are directly comparable in magnitude thereby giving the in-plane magnetization vector directly. We show that it is of great value to study both in-plane magnetization vector components when studying coupled structures where significant anisotropies are also present. We discuss simulations which show that it is possible to accurately determine the coupling strength in such structures by examining the behavior of the component of magnetization perpendicular to the applied field in the vicinity of the hard in-plane anisotropy axis. We illustrate this technique by examining the magnetization and magnetic anisotropy behavior of ultrathin Co/Cu(111)/Co (dCu=20 Å and 27 Å) trilayer structures prepared by molecular beam epitaxy, in which coherent rotation of the magnetization vector is observed when the magnetic field B is applied along the hard in-plane anisotropy axis, with the magnitude of the magnetization vector constant and close to its bulk value. Results of micromagnetic calculations closely reproduce the observed parallel and perpendicular magnetization loops, and yield strong uniaxial magnetic anisotropies in both layers, while the interlayer coupling appears to be absent or negligible in comparison with the anisotropy strengths.

Design and analysis of an unconventional permanent magnet linear machine for energy harvesting

NASA Astrophysics Data System (ADS)

Zeng, Peng

This Ph.D. dissertation proposes an unconventional high power density linear electromagnetic kinetic energy harvester, and a high-performance two-stage interface power electronics to maintain maximum power abstraction from the energy source and charge the Li-ion battery load with constant current. The proposed machine architecture is composed of a double-sided flat type silicon steel stator with winding slots, a permanent magnet mover, coil windings, a linear motion guide and an adjustable spring bearing. The unconventional design of the machine is that NdFeB magnet bars in the mover are placed with magnetic fields in horizontal direction instead of vertical direction and the same magnetic poles are facing each other. The derived magnetic equivalent circuit model proves the average air-gap flux density of the novel topology is as high as 0.73 T with 17.7% improvement over that of the conventional topology at the given geometric dimensions of the proof-of-concept machine. Subsequently, the improved output voltage and power are achieved. The dynamic model of the linear generator is also developed, and the analytical equations of output maximum power are derived for the case of driving vibration with amplitude that is equal, smaller and larger than the relative displacement between the mover and the stator of the machine respectively. Furthermore, the finite element analysis (FEA) model has been simulated to prove the derived analytical results and the improved power generation capability. Also, an optimization framework is explored to extend to the multi-Degree-of-Freedom (n-DOF) vibration based linear energy harvesting devices. Moreover, a boost-buck cascaded switch mode converter with current controller is designed to extract the maximum power from the harvester and charge the Li-ion battery with trickle current. Meanwhile, a maximum power point tracking (MPPT) algorithm is proposed and optimized for low frequency driving vibrations. Finally, a proof-of-concept unconventional permanent magnet (PM) linear generator is prototyped and tested to verify the simulation results of the FEA model. For the coil windings of 33, 66 and 165 turns, the output power of the machine is tested to have the output power of 65.6 mW, 189.1 mW, and 497.7 mW respectively with the maximum power density of 2.486 mW/cm3.

Micromagnetic structure in Co-alloy thin films and its correlation with microstructure

NASA Astrophysics Data System (ADS)

Tang, Kai

The development of magnetic hard disk recording has resulted in an increase of recording density in an accelerated pace. How to maintain the increasingly smaller bits with low noise presents a tremendous challenge to the recording media, which requires detailed study of micromagnetic structure of the media to understand the noise mechanism, and elucidation of the correlation between the micromagnetic structure and microstructure to systematically develop media materials and tailor their microstructure. Lorentz transmission electron microscopy (LTEM) is a high-resolution magnetic imaging technique. However, it requires uniformly thin specimens, which cannot be produced by conventional TEM specimen preparation methods. Consequently, its application to real computer magnetic hard disks has been limited. In this dissertation, a combined dimpling and chemical etching method is introduced to prepare specimens directly from the unmodified hard disks with the typical C/Co alloy/Cr/NiP/Al (substrate) structure. The specimens typically have 2000 μmsp2 or larger electron transparent areas of Co alloy/Cr films with uniform thickness, which are suitable for LTEM observation. This method is applicable to disks with both smooth and mechanically textured substrates. In this work, LTEM has been employed to study recorded patterns in real hard disks. Magnetic recording was performed on a standard spin stand. Bits of densities from 15 to 100 kfci were examined with head skew angles of 0sp° and 20sp°, respectively. We also compared tracks recorded on dc-erased disks with those on as-deposited disks. We observed magnetic ripples within the tracks and the inter-track regions, magnetic vortices of 0.1-0.2 mum in diameter at the bit-transitions, and curved magnetic domain walls in the track-edge regions resulting from the "dog-bone" shaped head field profile. Our results also indicate that the micromagnetic structure at the track edges is influenced by head skew and magnetization direction in the inter-track regions. The LTEM results are combined with MFM observations to provide further understanding. The study has concentrated on isotropic media on smooth substrates since low head-to-medium spacing required by high recording density demonstrates the need for this type of media. The recorded tracks are remanent magnetic states after a strong (head) magnetic field was applied. We also examined an ac-erased state, in which the effect of external field is removed. Magnetic vortices are identified, in which small crystal grains form magnetic clusters and these clusters then form closed-fluxed vortices. The size of these vortices is estimated to be around 1.0-1.5 mum, about 10 times larger than that found in the bit-transition regions. The smaller vortex sizes in the bit-transition regions may result from constraints from adjacent bits as well as the difference in magnetic processes generating these states. (Abstract shortened by UMI.)

A Reconfigurable Omnidirectional Soft Robot Based on Caterpillar Locomotion.

PubMed

Zou, Jun; Lin, Yangqiao; Ji, Chen; Yang, Huayong

2018-04-01

A pneumatically powered, reconfigurable omnidirectional soft robot based on caterpillar locomotion is described. The robot is composed of nine modules arranged as a three by three matrix and the length of this matrix is 154 mm. The robot propagates a traveling wave inspired by caterpillar locomotion, and it has all three degrees of freedom on a plane (X, Y, and rotation). The speed of the robot is about 18.5 m/h (two body lengths per minute) and it can rotate at a speed of 1.63°/s. The modules have neodymium-iron-boron (NdFeB) magnets embedded and can be easily replaced or combined into other configurations. Two different configurations are presented to demonstrate the possibilities of the modular structure: (1) by removing some modules, the omnidirectional robot can be reassembled into a form that can crawl in a pipe and (2) two omnidirectional robots can crawl close to each other and be assembled automatically into a bigger omnidirectional robot. Omnidirectional motion is important for soft robots to explore unstructured environments. The modular structure gives the soft robot the ability to cope with the challenges of different environments and tasks.

Testing the Model of Oscillating Magnetic Traps

NASA Astrophysics Data System (ADS)

Szaforz, Ż.; Tomczak, M.

2015-01-01

The aim of this paper is to test the model of oscillating magnetic traps (the OMT model), proposed by Jakimiec and Tomczak ( Solar Phys. 261, 233, 2010). This model describes the process of excitation of quasi-periodic pulsations (QPPs) observed during solar flares. In the OMT model energetic electrons are accelerated within a triangular, cusp-like structure situated between the reconnection point and the top of a flare loop as seen in soft X-rays. We analyzed QPPs in hard X-ray light curves for 23 flares as observed by Yohkoh. Three independent methods were used. We also used hard X-ray images to localize magnetic traps and soft X-ray images to diagnose thermal plasmas inside the traps. We found that the majority of the observed pulsation periods correlates with the diameters of oscillating magnetic traps, as was predicted by the OMT model. We also found that the electron number density of plasma inside the magnetic traps in the time of pulsation disappearance is strongly connected with the pulsation period. We conclude that the observations are consistent with the predictions of the OMT model for the analyzed set of flares.

A magnetic model for low/hard state of black hole binaries

NASA Astrophysics Data System (ADS)

Wang, Ding-Xiong

2015-08-01

A magnetic model for low/hard state (LHS) of black hole X-ray binaries (BHXBs), H1743-322 and GX 339-4, is proposed based on the transportation of magnetic field from a companion into an accretion disc around a black hole (BH). This model consists of a truncated thin disc with an inner advection-dominated accretion flow (ADAF). The spectral profiles of the sources are fitted in agreement with the data observed at four different dates corresponding to the rising stage of the LHS. In addition, the association of the LHS with quasi-steady jet is modelled based on the transportation of magnetic field, where the Blandford-Znajek (BZ) and Blandford-Payne (BP) processes are invoked to drive the jets from BH and inner ADAF. It turns out that the steep radio-X-ray correlations observed in H1743-322 and GX 339-4 can be interpreted based on our model. It is suggested that large-scale magnetic field can be regarded as the second parameter for governing the state transitions in some BHXBs.

Shaping Si, NiCo, and glass substrates via stresses in the coatings

NASA Astrophysics Data System (ADS)

Wang, Xiaoli; Yao, Youwei; Ye, Shi; Liu, Tianchen; Assoufid, Lahsen; Cao, Jian; Ulmer, M. P.

2016-09-01

Here we report progress toward the fabrication of adaptive or active Si X-ray mirrors via a two step process. The first step is to curve a Si flat and then coat it with Terfenol-D that will allow the shape control via the application of a magnetic field. The goal is to create a mirror whose local (a few mm-length scale) slope can be changed and left for several hours or more. The current work described here was done in on Si to demonstrate the ability to produce the initial curvature, and in parallel, work to on magnetically hard NiCo 5 cm x 5 cm square plus on a glass sample. The glass sample was used a proto-type to model making changes in two different locations on a mirror. The NiCo sample was used to show that a magnetic field can be retained in a magnetically hard substrate such that the magnetically induced stress in the Terfenol-D was able to maintain a deformation for as long as time permitted to make the measurement which was 71 hours.

Controlling the shapes of coated silicon substrates via magnetic fields, a progress report

NASA Astrophysics Data System (ADS)

Ulmer, Melville P.; Coppejans, Rocco; Buchholz, David B.; Cao, Jian; Wang, Xiaoli; Mercado, Alejandro M.; Qian, Jun; Assoufid, Lahsen; O'Donnell, Allison E.; Condron, Kyle S.; Harpt, Benjamin E.

2017-08-01

We describe our progress in developing a method for correcting residual figure errors in X-ray mirrors. The technology has applications to both synchrotron radiation beamlines and X-ray astronomy. Our concept is to develop mirrors that are on the order of a millimeter thick. A magnetic smart material (MSM) is deposited onto the mirror substrate (silicon) and coated with a magnetically hard material. The shape of the mirror can be controlled by applying an external magnetic field to the mirror. This causes the MSM to expand or contract, thereby applying a magnetostrictive stress to the mirror and changing its shape. The shape change is maintained after the field has been removed by the magnetic hard material, which retains part of the field and prevents the MSM from relaxing. Here we present the results of shaping 200 µm thick silicon (100) 14 × 2 mm cantilevers and 50 × 50 × 0.1 mm substrates. We demonstrate that not only can a sizable deflection be created, but it can also be retained for ˜ 60 hours.

Study of structural and magnetic properties of melt spun Nd2Fe13.6Zr0.4B ingot and ribbon

NASA Astrophysics Data System (ADS)

Amin, Muhammad; Siddiqi, Saadat A.; Ashfaq, Ahmad; Saleem, Murtaza; Ramay, Shahid M.; Mahmood, Asif; Al-Zaghayer, Yousef S.

2015-12-01

Nd2Fe13.6Zr0.4B hard magnetic material were prepared using arc-melting technique on a water-cooled copper hearth kept under argon gas atmosphere. The prepared samples, Nd2Fe13.6Zr0.4B ingot and ribbon are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) for crystal structure determination and morphological studies, respectively. The magnetic properties of the samples have been explored using vibrating sample magnetometer (VSM). The lattice constants slightly increased due to the difference in the ionic radii of Fe and that of Zr. The bulk density decreased due to smaller molar weight and low density of Zr as compared to that of Fe. Ingot sample shows almost single crystalline phase with larger crystallite sizes whereas ribbon sample shows a mixture of amorphous and crystalline phases with smaller crystallite sizes. The crystallinity of the material was highly affected with high thermal treatments. Magnetic measurements show noticeable variation in magnetic behavior with the change in crystallite size. The sample prepared in ingot type shows soft while ribbon shows hard magnetic behavior.

Effect of magnetic and density fluctuations on the propagation of lower hybrid waves in tokamaks

NASA Astrophysics Data System (ADS)

Vahala, George; Vahala, Linda; Bonoli, Paul T.

1992-12-01

Lower hybrid waves have been used extensively for plasma heating, current drive, and ramp-up as well as sawteeth stabilization. The wave kinetic equation for lower hybrid wave propagation is extended to include the effects of both magnetic and density fluctuations. This integral equation is then solved by Monte Carlo procedures for a toroidal plasma. It is shown that even for magnetic/density fluctuation levels on the order of 10-4, there are significant magnetic fluctuation effects on the wave power deposition into the plasma. This effect is quite pronounced if the magnetic fluctuation spectrum is peaked within the plasma. For Alcator-C-Mod [I. H. Hutchinson and the Alcator Group, Proceedings of the IEEE 13th Symposium on Fusion Engineering (IEEE, New York, 1990), Cat. No. 89CH 2820-9, p. 13] parameters, it seems possible to be able to infer information on internal magnetic fluctuations from hard x-ray data—especially since the effects of fluctuations on electron power density can explain the hard x-ray data from the JT-60 tokamak [H. Kishimoto and JT-60 Team, in Plasma Physics and Controlled Fusion (International Atomic Energy Agency, Vienna, 1989), Vol. I, p. 67].

Hard X-ray Sources for the Mexican Synchrotron Project

NASA Astrophysics Data System (ADS)

Reyes-Herrera, Juan

2016-10-01

One of the principal tasks for the design of the Mexican synchrotron was to define the storage ring energy. The main criteria for choosing the energy come from studying the electromagnetic spectrum that can be obtained from the synchrotron, because the energy range of the spectrum that can be obtained will determine the applications available to the users of the future light source. Since there is a public demand of hard X-rays for the experiments in the synchrotron community users from Mexico, in this work we studied the emission spectra from some hard X-ray sources which could be the best options for the parameters of the present Mexican synchrotron design. The calculations of the flux and the brightness for one Bending Magnet and four Insertion Devices are presented; specifically, for a Superconducting Bending Magnet (SBM), a Superconducting Wiggler (SCW), an In Vacuum Short Period Undulator (IV-SPU), a Superconducting Undulator (SCU) and for a Cryogenic Permanent Magnet Undulator (CPMU). Two commonly available synchrotron radiation programs were used for the computation (XOP and SRW). From the results, it can be concluded that the particle beam energy from the current design is enough to have one or more sources of hard X-rays. Furthermore, a wide range of hard X-ray region can be covered by the analyzed sources, and the choice of each type should be based on the specific characteristics of the X-ray beam to perform the experiments at the involved beamline. This work was done within the project Fomix Conacyt-Morelos ”Plan Estrategico para la construccion y operación de un Sincrotron en Morelos” (224392).

Figures of Merit for Magnetic Recording Media

NASA Astrophysics Data System (ADS)

Skomski, Ralph; Sellmyer, D. J.

2007-03-01

Since the first nucleation-field calculations for hard-soft nanostructures with multilayered [1] and arbitrary [2] geometries, exchange-spring magnets have attracted much attention in various areas of magnetism, including magnetic recording. Ultrahigh storage densities correspond to the strong-coupling limit, realized on small length scales and described by volume-averaged anisotropies. Second-order perturbation theory yields finite-size corrections that describe a partial decoupling of the phases. Since soft phases reduce the nucleation field, nanostructuring can be used to reduce the coercivity Hc while maintaining the energy barrier EB. However, the ratio EB/Hc is an ill-defined figure of merit, because the comparison with the Stoner-Wohlfarth model requires the introduction of a particle volume, as contrasted to an area. By using elongated particles with a continuous anisotropy gradient, it is possible to reduce the coercivity by a factor scaling as the bit size divided by the domain-wall width of the hard phase. However, with decreasing bit size this effect becomes less pronounced. In the strong-coupling limit, thermal stability yields a maximum storage density of order γ/kBT, where γ is the domain-wall energy of the hard phase. - This research is supported by NSF MRSEC, INSIC, and NCMN. [1] S. Nieber and H. Kronm"uller, phys. stat. sol. (b) 153, 367 (1989). [2] R. Skomski and J. M. D. Coey, Phys. Rev. B 48, 15812 (1993).

Influence of low-temperature nitriding on the strain-induced martensite and laser-quenched austenite in a magnetic encoder made from 304L stainless steel.

PubMed

Leskovšek, Vojteh; Godec, Matjaž; Kogej, Peter

2016-08-05

We have investigated the possibility of producing a magnetic encoder by an innovative process. Instead of turning grooves in the encoder bar for precise positioning, we incorporated the information in 304L stainless steel by transforming the austenite to martensite after bar extrusion in liquid nitrogen and marking it with a laser, which caused a local transformation of martensite back into austenite. 304L has an excellent corrosion resistance, but a low hardness and poor wear resistance, which limits its range of applications. However, nitriding is a very promising way to enhance the mechanical and magnetic properties. After low-temperature nitriding at 400 °C it is clear that both ε- and α'-martensite are present in the deformed microstructure, indicating the simultaneous stress-induced and strain-induced transformations of the austenite. The effects of a laser surface treatment and the consequent appearance of a non-magnetic phase due to the α' → γ transformation were investigated. The EDS maps show a high concentration of nitrogen in the alternating hard surface layers of γN and α'N (expanded austenite and martensite), but no significantly higher concentration of chromium or iron was detected. The high surface hardness of this nitride layer will lead to steels and encoders with better wear and corrosion resistance.

Influence of low-temperature nitriding on the strain-induced martensite and laser-quenched austenite in a magnetic encoder made from 304L stainless steel

PubMed Central

Leskovšek, Vojteh; Godec, Matjaž; Kogej, Peter

2016-01-01

We have investigated the possibility of producing a magnetic encoder by an innovative process. Instead of turning grooves in the encoder bar for precise positioning, we incorporated the information in 304L stainless steel by transforming the austenite to martensite after bar extrusion in liquid nitrogen and marking it with a laser, which caused a local transformation of martensite back into austenite. 304L has an excellent corrosion resistance, but a low hardness and poor wear resistance, which limits its range of applications. However, nitriding is a very promising way to enhance the mechanical and magnetic properties. After low-temperature nitriding at 400 °C it is clear that both ε- and α′-martensite are present in the deformed microstructure, indicating the simultaneous stress-induced and strain-induced transformations of the austenite. The effects of a laser surface treatment and the consequent appearance of a non-magnetic phase due to the α′ → γ transformation were investigated. The EDS maps show a high concentration of nitrogen in the alternating hard surface layers of γN and α′N (expanded austenite and martensite), but no significantly higher concentration of chromium or iron was detected. The high surface hardness of this nitride layer will lead to steels and encoders with better wear and corrosion resistance. PMID:27492862

d -zero magnetism in nanoporous amorphous alumina membranes

NASA Astrophysics Data System (ADS)

Esmaeily, Amir Sajad; Venkatesan, M.; Sen, S.; Coey, J. M. D.

2018-05-01

Nanoporous alumina membranes produced by mild or hard anodization have a controllable pore surface area up to 400 times that of the membrane itself. They exhibit a temperature-independent and almost anhysteretic saturating response to a magnetic field up to temperatures of 300 K or more. The magnetism, which cannot be explained by the ˜1 ppm of transition-metal impurities present in the membranes, increases with the area of the open nanopores, reaching values of 0.6 Bohr magnetons per square nanometer for mild anodization and 8 Bohr magnetons per square nanometer for the faster hard anodization process. Crystallization of the membrane or treatment with salicylic acid can destroy 90% of the magnetism. The effect is therefore linked with the surfaces of the open pores in the amorphous A l2O3 . Possible explanations in terms of electrons associated with oxygen vacancies (F or F+ centers) are considered. It is concluded that the phenomenon involved is likely to be saturating giant orbital paramagnetism, rather than any sort of collective ferromagnetic spin order.

HARD X-RAY ASYMMETRY LIMITS IN SOLAR FLARE CONJUGATE FOOTPOINTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daou, Antoun G.; Alexander, David, E-mail: agdaou@rice.edu, E-mail: dalex@rice.edu

2016-11-20

The transport of energetic electrons in a solar flare is modeled using a time-dependent one-dimensional Fokker–Planck code that incorporates asymmetric magnetic convergence. We derive the temporal and spectral evolution of the resulting hard X-ray (HXR) emission in the conjugate chromospheric footpoints, assuming thick target photon production, and characterize the time evolution of the numerically simulated footpoint asymmetry and its relationship to the photospheric magnetic configuration. The thick target HXR asymmetry in the conjugate footpoints is found to increase with magnetic field ratio as expected. However, we find that the footpoint HXR asymmetry saturates for conjugate footpoint magnetic field ratios ≥4.more » This result is borne out in a direct comparison with observations of 44 double-footpoint flares. The presence of such a limit has not been reported before, and may serve as both a theoretical and observational benchmark for testing a range of particle transport and flare morphology constraints, particularly as a means to differentiate between isotropic and anisotropic particle injection.« less

Mechanical and electrical properties of low temperature phase MnBi

NASA Astrophysics Data System (ADS)

Jiang, Xiujuan; Roosendaal, Timothy; Lu, Xiaochuan; Palasyuk, Olena; Dennis, Kevin W.; Dahl, Michael; Choi, Jung-Pyung; Polikarpov, Evgueni; Marinescu, Melania; Cui, Jun

2016-01-01

Low temperature phase (LTP) manganese bismuth (MnBi) is a promising rare-earth-free permanent magnet material due to its high intrinsic coercivity and large positive temperature coefficient. While scientists are making progress on fabricating bulk MnBi magnets, engineers have begun considering MnBi magnets for motor applications. Physical properties other than magnetic ones could significantly affect motor design. Here, we report results of our investigation on the mechanical and electrical properties of bulk LTP MnBi and their temperature dependence. A MnBi ingot was prepared using an arc melting technique and subsequently underwent grinding, sieving, heat treatment, and cryomilling. The resultant powders with a particle size of ˜5 μm were magnetically aligned, cold pressed, and sintered at a predefined temperature. Micro-hardness testing was performed on a part of original ingot and we found that the hardness of MnBi was 109 ± 15 HV. The sintered magnets were subjected to compressive testing at different temperatures and it was observed that a sintered MnBi magnet fractured when the compressive stress exceeded 193 MPa at room temperature. Impedance spectra were obtained using electrochemical impedance spectroscopy at various temperatures and we found that the electrical resistance of MnBi at room temperature was about 6.85 μΩ m.

Building blocks for correlated superconductors and magnets

DOE PAGES

Sarrao, J. L.; Ronning, F.; Bauer, E. D.; ...

2015-04-01

Recent efforts at Los Alamos to discover strongly correlated superconductors and hard ferromagnets are reviewed. While serendipity remains a principal engine of materials discovery, design principles and structural building blocks are beginning to emerge that hold potential for predictive discovery. In addition, successes over the last decade with the so-called “115” strongly correlated superconductors are summarized, and more recent efforts to translate these insights and principles to novel hard magnets are discussed. While true “materials by design” remains a distant aspiration, progress is being made in coupling empirical design principles to electronic structure simulation to accelerate and guide materials designmore » and synthesis.« less

Physics of the saturation of particle acceleration in relativistic magnetic reconnection

NASA Astrophysics Data System (ADS)

Kagan, Daniel; Nakar, Ehud; Piran, Tsvi

2018-05-01

We investigate the saturation of particle acceleration in relativistic reconnection using two-dimensional particle-in-cell simulations at various magnetizations σ. We find that the particle energy spectrum produced in reconnection quickly saturates as a hard power law that cuts off at γ ≈ 4σ, confirming previous work. Using particle tracing, we find that particle acceleration by the reconnection electric field in X-points determines the shape of the particle energy spectrum. By analysing the current sheet structure, we show that physical cause of saturation is the spontaneous formation of secondary magnetic islands that can disrupt particle acceleration. By comparing the size of acceleration regions to the typical distance between disruptive islands, we show that the maximum Lorentz factor produced in reconnection is γ ≈ 5σ, which is very close to what we find in our particle energy spectra. We also show that the dynamic range in Lorentz factor of the power-law spectrum in reconnection is ≤40. The hardness of the power law combined with its narrow dynamic range implies that relativistic reconnection is capable of producing the hard narrow-band flares observed in the Crab nebula but has difficulty producing the softer broad-band prompt gamma-ray burst emission.

Phase formation kinetics, hardness and magnetocaloric effect of sub-rapidly solidified LaFe11.6Si1.4 plates during isothermal annealing

NASA Astrophysics Data System (ADS)

Dai, Yuting; Xu, Zhishuai; Luo, Zhiping; Han, Ke; Zhai, Qijie; Zheng, Hongxing

2018-05-01

High-temperature phase transition behavior and intrinsic brittleness of NaZn13-type τ1 phase in La-Fe-Si magnetocaloric materials are two key problems from the viewpoint of materials production and practical applications. In the present work, the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation was introduced to quantitatively characterize the formation kinetics of τ1 phase in sub-rapidly solidified LaFe11.6Si1.4 plates during the isothermal annealing process. Avrami index was estimated to be 0.43 (∼0.5), which suggests that the formation of τ1 phase is in a diffusion-controlled one-dimensional growth mode. Meanwhile, it is found that the Vickers hardness as a function of annealing time for sub-rapidly solidified plates also agrees well with the JMAK equation. The Vickers hardness of τ1 phase was estimated to be about 754. Under a magnetic field change of 30 kOe, the maximum magnetic entropy change was about 22.31 J/(kg·K) for plates annealed at 1323 K for 48 h, and the effective magnetic refrigeration capacity reached 191 J/kg.

Exchange-coupling of hard and soft magnetic sublattices and magnetic anomalies in mixed spinel NiFe0.75Cr1.25O4 nanoparticles

NASA Astrophysics Data System (ADS)

Lyubutin, I. S.; Starchikov, S. S.; Baskakov, A. O.; Gervits, N. E.; Lin, Chun-Rong; Tseng, Yaw-Teng; Lee, Wen-Jen; Shih, Kun-Yauh

2018-04-01

A set of single-crystalline nanoparticles (NPs) of nickel-chromium ferrite NiFe0.75Cr1.25O4 with a cubic spinel structure were synthesized and investigated. The NPs size can be varied from about 5 to 50 nm by the final annealing of the precursor at different temperatures. The distribution of cations over the tetrahedral (A) and the octahedral [B] sites (Fe0.75 Ni0.25) [Ni0.75 Cr1.25] O4 was established from the magnetic and Mössbauer measurements. In large NPs, the magnetic structure at low temperatures is close to the collinear antiferromagnetic (AFM) structure of the Neel type; and the total magnetic moment Mtot of the ferrite coincides with the direction of the B-sublattice moment. Several size-dependent magnetic anomalies were revealed. Three types of magnetic ions present in the A- and B- sublattices cause the competition of AFM and FM exchange interactions resulting in the highly frustrated magnetic ordering and the occurrence of canted magnetic structure in the octahedral B-sublattice. The frustrated structure is very flexible and significantly subjected to temperature and applied field. It results in several magnetic anomalies observed, including the occurrence of magnetic compensation, abnormal behavior of ZFC and FC magnetization curves and hysteresis loops. It was shown that magnetic anomalies can be explained in terms of exchange coupling of "soft" and "hard" magnetic B- and A-sublattices. This effect in the (Fe0.75 Ni0.25) [Ni0.75Cr1.25] O4 NPs can be considered as an atomic-scale analog of a similar effect observed in two-phase exchange-coupled alloys developed for permanent magnets and for the perpendicular recoding media.

49 CFR 225.37 - Magnetic media transfer and electronic submission.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Form (Form FRA F 6180.99); and (3) A notarized hard copy of the Railroad Injury and Illness Summary....99) which is submitted to an FRA-designated computer; and (2) A notarized hard copy of the Railroad... reporting data for the reports identified in paragraph (a) of this section in a year-to-date file format as...

Resonant Inverse Compton Scattering Spectra from Highly Magnetized Neutron Stars

NASA Astrophysics Data System (ADS)

Wadiasingh, Zorawar; Baring, Matthew G.; Gonthier, Peter L.; Harding, Alice K.

2018-02-01

Hard, nonthermal, persistent pulsed X-ray emission extending between 10 and ∼150 keV has been observed in nearly 10 magnetars. For inner-magnetospheric models of such emission, resonant inverse Compton scattering of soft thermal photons by ultrarelativistic charges is the most efficient production mechanism. We present angle-dependent upscattering spectra and pulsed intensity maps for uncooled, relativistic electrons injected in inner regions of magnetar magnetospheres, calculated using collisional integrals over field loops. Our computations employ a new formulation of the QED Compton scattering cross section in strong magnetic fields that is physically correct for treating important spin-dependent effects in the cyclotron resonance, thereby producing correct photon spectra. The spectral cutoff energies are sensitive to the choices of observer viewing geometry, electron Lorentz factor, and scattering kinematics. We find that electrons with energies ≲15 MeV will emit most of their radiation below 250 keV, consistent with inferred turnovers for magnetar hard X-ray tails. More energetic electrons still emit mostly below 1 MeV, except for viewing perspectives sampling field-line tangents. Pulse profiles may be singly or doubly peaked dependent on viewing geometry, emission locale, and observed energy band. Magnetic pair production and photon splitting will attenuate spectra to hard X-ray energies, suppressing signals in the Fermi-LAT band. The resonant Compton spectra are strongly polarized, suggesting that hard X-ray polarimetry instruments such as X-Calibur, or a future Compton telescope, can prove central to constraining model geometry and physics.

Experimental Evidence of Dipolar Interaction in Bilayer Nanocomposite Magnets

DTIC Science & Technology

2010-11-25

corporated to improve experimental systems. However, re- ported bulk nanocomposite magnets exhibit (BH)max val- ues that are far below the...Appl Phys A DOI 10.1007/s00339-010-6073-6 Experimental evidence of dipolar interaction in bilayer nanocomposite magnets A.J. Zambano · H. Oguchi · I...Abstract We use magnetic thin film hard/non/soft-mag- netic trilayer systems to probe the nature of the hard–soft phase interaction and the role

A MEMS sensor for AC electric current

NASA Astrophysics Data System (ADS)

Leland, Eli Sidney

This manuscript describes the development of a new MEMS sensor for the measurement of AC electric current. The sensor is comprised of a MEMS piezoelectric cantilever with a microscale permanent magnet mounted to the cantilever's free end. When placed near a wire carrying AC current, the magnet couples to the oscillating magnetic field surrounding the wire, causing the cantilever to deflect, and piezoelectric coupling produces a sinusoidal voltage proportional to the current in the wire. The sensor is itself passive, requiring no power supply to operate. It also operates on proximity and need only be placed near a current carrier in order to function. The sensor does not need to encircle the current carrier and it therefore can measure current in two-wire zip-cords without necessitating the separation of the two conductors. Applications for tins sensor include measuring residential and commercial electricity use and monitoring electric power distribution networks. An analytical model describing the behavior of the current sensor was developed. This model was also adapted to describe the power output of an energy scavenger coupled to a wire carrying AC current. A mesoscale sensor exhibited a sensitivity of 75 mV/A when measuring AC electric current in a zip-cord. A mesoscale energy scavenger produced 345 muW when coupled to a zip-cord carrying 13 A. MEMS current sensors were fabricated from aluminum nitride piezoelectric cantilevers and composite permanent magnets. The cantilevers were fabricated using a four-mask process. Microscale permanent magnets were dispenser-printed using NdFeB magnetic powder with an epoxy binder. The MEMS AC current sensor was interfaced with amplification circuitry and packaged inside an almninum enclosure. The sensor was also integrated with a mesoscale energy scavenger and power conditioning circuitry to create a fully self-powered current sensor. Unamplified sensitivity of the sensor was 0.1-1.1 mV/A when measuring currents in single wires and zip-cords. The self-powered current sensor operated at a 0.6% duty cycle when coupled to the zip-cord of a 1500 W space heater drawing 13 A. The self-powered sensor's energy scavenger transferred energy to a 10 mF storage capacitor at a rate of 69 muJ/s.

Depositing spacing layers on magnetic film with liquid phase epitaxy

NASA Technical Reports Server (NTRS)

Moody, J. W.; Shaw, R. W.; Sanfort, R. M.

1975-01-01

Liquid phase epitaxy spacing layer is compatible with systems which are hard-bubble proofed by use of second magnetic garnet film as capping layer. Composite is superior in that: circuit fabrication time is reduced; adherence is superior; visibility is better; and, good match of thermal expansion coefficients is provided.

Perpendicular magnetic recording—Its development and realization—

PubMed Central

IWASAKI, Shun-ichi

2009-01-01

The principle of conventional magnetic recording is that magnetic fields are applied parallel to the plane of the magnetic medium. As described in this paper, the invention and development of a new method of placing the magnetized information perpendicular to the plane of the magnetic recording medium is presented. The yield in the mass production of high-density hard disk drives (HDDs) for perpendicular recording is much higher than that of HDDs for conventional recording. Consequently, it is estimated that as many as 75% of the 500 million HDDs to be shipped this year will use this technology. PMID:19212097

Low coordinated mononuclear erbium(iii) single-molecule magnets with C3v symmetry: a method for altering single-molecule magnet properties by incorporating hard and soft donors.

PubMed

Zhang, Haitao; Nakanishi, Ryo; Katoh, Keiichi; Breedlove, Brian K; Kitagawa, Yasutaka; Yamashita, Masahiro

2018-01-02

Structures and magnetic characteristics of two three-coordinate erbium(iii) compounds with C 3v geometry, tris(2,6-di-tert-butyl-p-cresolate)erbium, Er(dbpc) 3 (1) and tris(bis(trimethylsilyl)methyl)erbium, Er(btmsm) 3 (2), were determined. Both underwent temperature-dependent slow magnetic relaxation processes in the absence of an external magnetic field. As a result of the differences in the coordination environment, they exhibit different energy barriers and quantum tunneling of magnetization (QTM) constants.

Energetic electrons, hard x-ray emission and MHD activity studies in the IR-T1 tokamak.

PubMed

Agah, K Mikaili; Ghoranneviss, M; Elahi, A Salar

2015-01-01

Determinations of plasma parameters as well as the Magnetohydrodynamics (MHD) activity, energetic electrons energy and energy confinement time are essential for future fusion reactors experiments and optimized operation. Also some of the plasma information can be deduced from these parameters, such as plasma equilibrium, stability, and MHD instabilities. In this contribution we investigated the relation between energetic electrons, hard x-ray emission and MHD activity in the IR-T1 Tokamak. For this purpose we used the magnetic diagnostics and a hard x-ray spectroscopy in IR-T1 tokamak. A hard x-ray emission is produced by collision of the runaway electrons with the plasma particles or limiters. The mean energy was calculated from the slope of the energy spectrum of hard x-ray photons.

Radio wave heating of the corona and electron precipitation during flares

NASA Technical Reports Server (NTRS)

Melrose, D. B.; Dulk, G. A.

1982-01-01

Electron-cyclotron masers, excited while energy release is occurring in a flaring magnetic loop, are likely to generate extremely intense radiation at decimeter wavelengths. The energy in the radiation can be comparable with that in the electrons associated with hard X-ray bursts, i.e., a significant fraction of the total energy in the flare. Essentially all of the radio energy is likely to be reabsorbed by gyroresonance absorption, either near the emitting region or at some distance away in neighboring loops. Enhanced diffusion of fast electrons caused by the maser can lead to precipitation at the maximum possible rate, and hence account for hard X-ray emission from the footpoints of the magnetic loops.

Composite nanoplatelets combining soft-magnetic iron oxide with hard-magnetic barium hexaferrite

NASA Astrophysics Data System (ADS)

Primc, D.; Makovec, D.

2015-01-01

By coupling two different magnetic materials inside a single composite nanoparticle, the shape of the magnetic hysteresis can be engineered to meet the requirements of specific applications. Sandwich-like composite nanoparticles composed of a hard-magnetic Ba-hexaferrite (BaFe12O19) platelet core in between two soft-magnetic spinel iron oxide maghemite (γ-Fe2O3) layers were synthesized using a new, simple and inexpensive method based on the co-precipitation of Fe3+/Fe2+ ions in an aqueous suspension of hexaferrite core nanoparticles. The required close control of the supersaturation of the precipitating species was enabled by the controlled release of the Fe3+ ions from the nitrate complex with urea ([Fe((H2N)2C&z.dbd;O)6](NO3)3) and by using Mg(OH)2 as a solid precipitating agent. The platelet Ba-hexaferrite nanoparticles of different sizes were used as the cores. The controlled coating resulted in an exclusively heterogeneous nucleation and the topotactic growth of the spinel layers on both basal surfaces of the larger hexaferrite nanoplatelets. The direct magnetic coupling between the core and the shell resulted in a strong increase of the energy product |BH|max. Ultrafine core nanoparticles reacted with the precipitating species and homogeneous product nanoparticles were formed, which differ in terms of the structure and composition compared to any other compound in the BaO-Fe2O3 system.By coupling two different magnetic materials inside a single composite nanoparticle, the shape of the magnetic hysteresis can be engineered to meet the requirements of specific applications. Sandwich-like composite nanoparticles composed of a hard-magnetic Ba-hexaferrite (BaFe12O19) platelet core in between two soft-magnetic spinel iron oxide maghemite (γ-Fe2O3) layers were synthesized using a new, simple and inexpensive method based on the co-precipitation of Fe3+/Fe2+ ions in an aqueous suspension of hexaferrite core nanoparticles. The required close control of the supersaturation of the precipitating species was enabled by the controlled release of the Fe3+ ions from the nitrate complex with urea ([Fe((H2N)2C&z.dbd;O)6](NO3)3) and by using Mg(OH)2 as a solid precipitating agent. The platelet Ba-hexaferrite nanoparticles of different sizes were used as the cores. The controlled coating resulted in an exclusively heterogeneous nucleation and the topotactic growth of the spinel layers on both basal surfaces of the larger hexaferrite nanoplatelets. The direct magnetic coupling between the core and the shell resulted in a strong increase of the energy product |BH|max. Ultrafine core nanoparticles reacted with the precipitating species and homogeneous product nanoparticles were formed, which differ in terms of the structure and composition compared to any other compound in the BaO-Fe2O3 system. Electronic supplementary information (ESI) available: Synthesis (ESI #1) and properties (ESI #2) of the barium hexaferrite core nanoparticles, TEM of the nanoparticles synthesized under an excessive supersaturation (ESI #3), and magnetic properties of physical mixtures of the hard-magnetic hexaferrite and the soft-magnetic spinel ferrite (ESI #4). See DOI: 10.1039/c4nr05854b

The effects of the cathode array on emitted hard x-ray from a small plasma focus device

NASA Astrophysics Data System (ADS)

Piriaei, D.; Mahabadi, T. D.; Javadi, S.; Ghoranneviss, M.

2017-08-01

In this study, the effects of the cathode array variations on emitted hard x-rays from a small Mather type plasma focus device (450 J) were investigated. The gradual elimination of the cathode rods inside the cathode array of the device lowered the quality and quantity of the emitted hard x-rays at different pressure values of argon gas. We theorized that the variations of the cathode array were able to change some discharge parameters that could vary the number of the energetic runaway electrons generated during the pinch phase which were responsible for the created features of the emitted hard x-rays. On the other hand, we hypothesized that the removal of the cathode rods could influence the current sheath dynamics during all the phases of a shot including its average axial velocity which was demonstrated by using two axial magnetic probes. We also theorized that cathode rod omission from the cathode array could also increase the initial inductance and the impedance of the system, and the impurities inside the plasma during the pinch phase which could lead to the growth of the instabilities. Moreover, by using the wavelet technique and studying the Mirnov signals, it was shown that the decrease of the cathode rod number increased the plasma magnetic field fluctuations or instabilities (MHD activities) that adversely affected the pinch quality, and reduced the emitted hard x-rays.

The magnetic properties and microstructure of Co-Pt thin films using wet etching process.

PubMed

Lee, Chang-Hyoung; Cho, Young-Lae; Lee, Won-Pyo; Suh, Su-Jeong

2014-11-01

Perpendicular magnetic recording (PMR) is a promising candidate for high density magnetic recording and has already been applied to hard disk drive (HDD) systems. However, media noise still limits the recording density. To reduce the media noise and achieve a high signal-to-noise ratio (SNR) in hard disk media, the grains of the magnetic layer must be magnetically isolated from each other. This study examined whether sputter-deposited Co-Pt thin films can have adjacent grains that are physically isolated. To accomplish this, the effects of the sputtering conditions and wet etching process on magnetic properties and the microstructure of the films were investigated. The film structure was Co-Pt (30 nm)/Ru (30 nm)/NiFe (10 nm)/Ta (5 nm). The composition of the Co-Pt thin films was Co-30.7 at.% Pt. The Co-Pt thin films were deposited in Ar gas at 5, 10, 12.5, and 15 mTorr. Wet etching process was performed using 7% nitric acid solution at room temperature. These films had high out-of-plane coercivity of up to 7032 Oe, which is twice that of the as-deposited film. These results suggest that wet etched Co-Pt thin films have weaker exchange coupling and enhanced out-of-plane coercivity, which would reduce the medium noise.

CoPtB(O) alloy films as new perpendicular recording media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayashi, K.; Hayakawa, M.; Ohmori, H.

In search of new hard magnetic materials with high saturation magnetization and large coercivity, a comprehensive study was made on numerous Co- and CoPt-base crystalline alloys by means of sputtering techniques. It revealed that a newly found CoPtB(O) alloy system possessed excellent hard magnetic properties with remarkably large perpendicular coercivity and high saturation magnetization. This new alloy film, deposited onto room temperature substrates, shows the magnetic properties of 4{pi}{ital M}{sub {ital s}}=12 kG, {ital H}{sup {perpendicular}}{sub {ital c}}=4000 Oe, and perpendicular anisotropy field {ital H}{sub {ital k}}=22 kOe. These values are superior to those of prevailing materials such as CoCrmore » perpendicular and CoPt or CoNi longitudinal recording media. The typical composition is Co{sub 69}Pt{sub 20}B{sub 6}O{sub 5} (at. %), and oxygen plays a momentous role on the coercivity in this alloy film. As a magnetic recording medium, a write/read experiment of this film shows that the readout signal has a +9 dB peak-to-peak amplitude compared with that of metal particle tape at 1 {mu}m wavelength and has +10 dB compared with that of a CoCr perpendicular medium at 0.5 {mu}m wavelength.« less

Structural, mechanical and magnetic study on galvanostatic electroplated nanocrystalline NiFeP thin films

NASA Astrophysics Data System (ADS)

Kalaivani, A.; Senguttuvan, G.; Kannan, R.

2018-03-01

Nickel based alloys has a huge applications in microelectronics and micro electromechanical systems owing to its superior soft magnetic properties. With the advantages of simplicity, cost-effectiveness and controllable patterning, electroplating processes has been chosen to fabricate thin films in our work. The soft magnetic NiFeP thin film was successfully deposited over the surface of copper plate through galvanostatic electroplating method by applying constant current density of 10 mA cm-2 for a deposition rate for half an hour. The properties of the deposited NiFeP thin films were analyzed by subjecting it into different physio-chemical characterization such as XRD, SEM, EDAX, AFM and VSM. XRD pattern confirms the formation of NiFeP particles and the structural analysis reveals that the NiFeP particles were uniformly deposited over the surface of copper substrate. The surface roughness analysis of the NiFeP films was done using AFM analysis. The magnetic studies and the hardness of the thin film were evaluated from the VSM and hardness test. The NiFeP thin films possess lower coercivity with higher magnetization value of 69. 36 × 10-3 and 431.92 Gauss.

Low temperature structural transitions in dipolar hard spheres: The influence on magnetic properties

NASA Astrophysics Data System (ADS)

Ivanov, A. O.; Kantorovich, S. S.; Rovigatti, L.; Tavares, J. M.; Sciortino, F.

2015-06-01

We investigate the structural chain-to-ring transition at low temperature in a gas of dipolar hard spheres (DHS). Due to the weakening of entropic contribution, ring formation becomes noticeable when the effective dipole-dipole magnetic interaction increases. It results in the redistribution of particles from usually observed flexible chains into flexible rings. The concentration (ρ) of DHS plays a crucial part in this transition: at a very low ρ only chains and rings are observed, whereas even a slight increase of the volume fraction leads to the formation of branched or defect structures. As a result, the fraction of DHS aggregated in defect-free rings turns out to be a non-monotonic function of ρ. The average ring size is found to be a slower increasing function of ρ when compared to that of chains. Both theory and computer simulations confirm the dramatic influence of the ring formation on the ρ-dependence of the initial magnetic susceptibility (χ) when the temperature decreases. The rings due to their zero total dipole moment are irresponsive to a weak magnetic field and drive to the strong decrease of the initial magnetic susceptibility.

Assessment of Retained Austenite in AISI D2 Tool Steel Using Magnetic Hysteresis and Barkhausen Noise Parameters

NASA Astrophysics Data System (ADS)

Kahrobaee, Saeed; Kashefi, Mehrdad

2015-03-01

Inaccurate heat treatment process could result in excessive amount of retained austenite, which degrades the mechanical properties, like strength, wear resistance, and hardness of cold work tool steel parts. Thus, to control the mechanical properties, quantitative measurement of the retained austenite is a critical step in optimizing the heat-treating parameters. X-ray diffraction method is the most frequently used technique for this purpose. This technique is, however, destructive and time consuming. Furthermore, it is not applicable to 100% quality inspection of industrial parts. In the present paper, the influence of austenitizing temperature on the retained austenite content and hardness of AISI D2 tool steel has been studied. Additionally, nondestructive magnetic hysteresis parameters of the samples including coercivity, magnetic saturation, and maximum differential permeability as well as their magnetic Barkhausen noise features (RMS peak voltage and peak position) have been investigated. The results revealed direct relations between magnetic saturation, differential permeability, and MBN peak amplitude with increasing austenitizing temperature due to the retained austenite formation. Besides, both parameters of coercivity and peak position had an inverse correlation with the retained austenite fraction.

EDITORIAL: Invited papers from ISAMMA 2010 (Sendai, Japan, 12-16 July 2010) Invited papers from ISAMMA 2010 (Sendai, Japan, 12-16 July 2010)

NASA Astrophysics Data System (ADS)

Takahashi, M.; Saito, H.

2011-02-01

This cluster issue of Journal of Physics D: Applied Physics contains a collection of papers based on invited talks given at the 2nd International Symposium on Advanced Magnetic Materials and Applications 2010 (ISAMMA 2010) held from 12-16 July 2010 in Sendai, Japan. ISAMMA is the first consolidated symposium of three independent symposia held in the Asian region. ISPMM (International Symposium on Physics of Magnetic Materials) of Japan started in 1987 in Sendai, and was held six times: Beijing (1992), Seoul (1995), Sendai (1998), Taipei (2001) and Singapore (2005). ISAMT (International Symposium of Advanced Magnetic Technology) of Taiwan and SOMMA (International Symposium on Magnetic Materials and Applications) of Korea both began in 1999 and were each held five times up to 2005. ISAMMA was established as a new international symposium which will be held every three years in Asia. The concept of this unified international symposium was mainly led by Professor M Takahashi, Conference Chair of ISAMMA 2010. The first memorial symposium, ISAMMA 2007, was held in Jeju Island, Korea, during the period from 28 May to 1 June 2007. The main purpose and scope of ISAMMA is to provide an opportunity for scientists and engineers from all over the world to meet in Asia to discuss recent advances in the study of magnetic materials and their physics, spin-related phenomena and materials. The categories of ISAMMA 2010 were: fundamental properties of magnetic materials; hard/soft magnetic materials and applications; spintronics materials and devices; structured materials; multi functional magnetic materials; spin dynamics and micromagnetics; magnetic storage; materials for applications (sensors, high-frequency, power, and bio/medical devices); magnetic imaging and characterization. The scientific programme began on Tuesday 13 July 2010 with the opening remark by the Symposium Chairman. The conference was attended by 511 participants from 23 countries, with about 40 per cent from overseas. The programme involved 4 plenary talks, 37 invited talks, 85 contributed talks and 352 posters. All submitted papers were reviewed in order to meet the standards of Journal of Physics D: Applied Physics and Journal of Physics: Conference Series. We are grateful to all participants for their valuable contributions and active discussions. We gratefully acknowledge the financial support of 17 Japanese companies and 7 Japanese foundations. Invited papers from ISAMMA 2010 Contents Current status and recent topics of rare-earth permanent magnets S Sugimoto Alloying effect on the magnetic properties of RFeB-type bulk magnets H W Chang, C C Hsieh, J Y Gan, Y T Cheng, M F Shih and W C Chang Coercivity distributions in Nd-Fe-B sintered magnets produced by the grain boundary diffusion process H Nakamura, K Hirota, T Ohashi and T Minowa Recent progress in high Bs Fe-based nanocrystalline soft magnetic alloys M Ohta and Y Yoshizawa Electric-field effects on magnetic anisotropy in Pd/Fe/Pd(0 0 1) surface Shinya Haraguchi, Masahito Tsujikawa, Junpei Gotou and Tatsuki Oda Gate modulation of spin precession in a semiconductor channel Hyun Cheol Koo, Jae Hyun Kwon, Jonghwa Eom, Joonyeon Chang, Suk Hee Han and Mark Johnson Ferromagnetic resonance of epitaxial Fe nanodots grown on MgO measured using coplanar waveguides M Mizuguchi and K Takanashi Switching phase diagrams of current-induced magnetization switching in asymmetric MgO-based magnetic tunnel junctions Seung-Young Park, Jae-Ho Han, Se-Chung Oh, Jang-Eun Lee, Kyung-Tae Nam, Hyun-Woo Lee, Younghun Jo and Kyung-Jin Lee Temperature dependence of spin-dependent transport properties of Co2MnSi-based current-perpendicular-to-plane magnetoresistive devices Y Sakuraba, K Izumi, S Bosu, K Saito and K Takanashi Adsorbate-induced spin-polarization enhancement of Fe3O4(0 0 1) A Pratt, M Kurahashi, X Sun and Y Yamauchi Antiferromagnetic coupling between spinel ferrite and α-Fe layers in Fe3-δO4/MgO/Fe(0 0 1) epitaxial films Hideto Yanagihara, Yuta Toyoda and Eiji Kita Monte Carlo simulations of the magnetocaloric effect in magnetic Ni-Mn-X (X = Ga, In) Heusler alloys V D Buchelnikov, V V Sokolovskiy, S V Taskaev, V V Khovaylo, A A Aliev, L N Khanov, A B Batdalov, P Entel, H Miki and T Takagi Changes in electronic states and magnetic free energy in La1-zCez(FexSi1-x)13 magnetic refrigerants A Fujita, S Fujieda and K Fukamichi Garnet composite films with Au particles fabricated by repetitive formation for enhancement of Faraday effect H Uchida, Y Mizutani, Y Nakai, A A Fedyanin and M Inoue Control of magnetic domain wall displacement using spin current in small in-plane magnetic field in Permalloy nanowires Yoshihiko Togawa, Takashi Kimura, Ken Harada, Akira Tonomura and Yoshichika Otani Magnetic-field tunable transmittance in a ferrofluid-filled silicon nitride photonic crystal slab H M Lee, L Horng and J C Wu Evaluation of a miniature magnetostrictive actuator using Galfenol under tensile stress Toshiyuki Ueno, Hidemitsu Miura and Sotoshi Yamada Sub-nm resolution depth profiling of the magnetic structure of thin films by the depth-resolved x-ray magnetic circular dichroism technique K Amemiya and M Sakamaki

Modification of the structural and magnetic properties of granular FePt films by seed layer conditioning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wicht, S., E-mail: s.wicht@ifw-dresden.de; TU Dresden, Institut für Werkstoffwissenschaft, Helmholtzstraße 10, D-01069 Dresden; Neu, V.

2015-01-07

The steadily increasing amount of digital information necessitates the availability of reliable high capacity magnetic data storage. Here, future hard disk drives with extended areal storage densities beyond 1.0 Tb/in{sup 2} are envisioned by using high anisotropy granular and chemically L1{sub 0}-ordered FePt (002) perpendicular media within a heat-assisted magnetic recording scheme. Perpendicular texturing of the [001] easy axes of the individual grains can be achieved by using MgO seed layers. It is therefore investigated, if and how an Ar{sup +} ion irradiation of the MgO seed layer prior to the deposition of the magnetic material influences the MgO surfacemore » properties and hereby the FePt [001] texture. Structural investigations reveal a flattening of the seed layer surface accompanied by a change in the morphology of the FePt grains. Moreover, the fraction of small second layer particles and the degree of coalescence of the primarily deposited FePt grains strongly increases. As for the magnetic performance, this results in a reduced coercivity along the magnetic easy axis (out of plane) and in enhanced hard axis (in-plane) remanence values. The irradiation induced changes in the magnetic properties of the granular FePt-C films are traced back to the accordingly modified atomic structure of the FePt-MgO interface region.« less

Minnealloy: a new magnetic material with high saturation flux density and low magnetic anisotropy

NASA Astrophysics Data System (ADS)

Mehedi, Md; Jiang, Yanfeng; Suri, Pranav Kumar; Flannigan, David J.; Wang, Jian-Ping

2017-09-01

We are reporting a new soft magnetic material with high saturation magnetic flux density, and low magnetic anisotropy. The new material is a compound of iron, nitrogen and carbon, α‧-Fe8(NC), which has saturation flux density of 2.8  ±  0.15 T and magnetic anisotropy of 46 kJ m-3. The saturation flux density is 27% higher than pure iron, a widely used soft magnetic material. Soft magnetic materials are very important building blocks of motors, generators, inductors, transformers, sensors and write heads of hard disk. The new material will help in the miniaturization and efficiency increment of the next generation of electronic devices.

Radiation damage studies of soft magnetic metallic glasses irradiated with high-energy heavy ions

NASA Astrophysics Data System (ADS)

Pavlovič, Márius; Miglierini, Marcel; Mustafin, Edil; Ensinger, Wolfgang; Šagátová, Andrea; Šoka, Martin

2015-01-01

Some soft magnetic metallic glasses are considered for use in magnetic cores of accelerator radio frequency cavities. Due to losses of the circulating ion beam, they may be exposed to irradiation by different ions at different energies. This paper presents data and review results of irradiation experiments concerning the influence of high-energy heavy ions on magnetic susceptibility of VITROPERM®-type metallic glasses. Samples of the VITROPERM® magnetic ribbons were irradiated by Au, Xe and U ions at 11.1 MeV/A (per nucleon) and 5.9 MeV/A, respectively. Irradiation fluences from 1 × 1011 up to 1 × 1013 ions/cm2 were applied. In case of the Au and U ions, the total fluence was accumulated in one beamtime, whereas two separate beamtimes were used to accumulate the final fluence in case of the Xe ions. Relative change in the samples' magnetic susceptibility after and before irradiation was evaluated as a function of the irradiation fluence. The irradiation experiments were performed with the UNILAC accelerator at GSI Helmholtzzentrum für Schwerionenforschung GmbH. They were simulated in SRIM2010 in order to obtain ionization densities (electronic stopping, dE/dx) and dpa (displacements per atom) caused by the ion beams in the sample material. This paper focuses mainly on the results collected in experiments with the Xe ions and compares them with data obtained in earlier experiments using Au and U ions. Radiation hardness of VITROPERM® is compared with radiation hardness of VITROVAC® that was studied in previous experiments. The VITROPERM® samples showed less drop in magnetic susceptibility in comparison with the VITROVAC® ones, and this drop occurred at higher fluences. This indicates higher radiation hardness of VITROPERM® compared with VITROVAC®. In addition, heavier ions cause bigger change in magnetic susceptibility than the lighter ones. The effect can be roughly scaled with electronic stopping, which suggests that the main mechanism of radiation damage is associated with swift electrons generated in the material via ionization by primary heavy ions.

Microwave, soft and hard X-ray imaging observations of two solar flares

NASA Technical Reports Server (NTRS)

Kundu, M. R.; Erskine, F. T.; Schmahl, E. J.; Machado, M. E.; Rovira, M. G.

1984-01-01

A set of microwave and hard X-ray observations of two flares observed simultaneously with the Very Large Array (VLA) and the Solar Maximum Mission Hard X-ray Imaging Spectrometer (SMM-HXIS) are presented. The LVA was used at 6 cm to map the slowly varying and burst components in three neighboring solar active regions (Boulder Nos. 2522, 2530, and 2519) from approximately 14:00 UT until 01:00 UT on June 24-25, 1980. Six microwave bursts less than 30 sfu were observed, and for the strongest of these, two-dimensional 'snapshot' (10 s) maps with spatial resolution of 5 in. were synthesized. HXIS data show clear interconnections between regions 2522 and 2530. The X-ray observations present a global picture of flaring activity, while the VLA data show the complexity of the small magnetic structures associated with the impulsive phase phenomena. It is seen that energy release did not occur in a single isolated magnetic structure, but over a large area of intermingled loop structures.

Reconnection, Particle Acceleration, and Hard X-ray Emission in Eruptive Solar Flares

NASA Astrophysics Data System (ADS)

Martens, Petrus C.

1998-11-01

The frequent occurrence of Hard X-ray emission from the top of flaring loops was one of the discoveries by the Hard X-ray telescope on board the Japanese Yohkoh satellite. I will show how the combined effect of magnetic field convergence and pitch- angle scattering of non-thermal electrons injected at the top of the loop results in the generation of looptop sources with properties akin to those observed by Yohkoh. In addition it is shown that the injection of proton beams in the loop legs, expected from theory, reproduces the observed high temperature ``ridges" in the loop legs by mirroring and energy loss through collisions. I will interpret these numerical results as supporting the now widely accepted model of an erupting magnetic flux tube generating a reconnecting current sheet in its wake, where most of the energy release takes place. The strong similarity with the reconnection observed in the MRX experiment in Princeton will be analyzed in detail.

Mapping hard magnetic recording disks by TOF-SIMS

NASA Astrophysics Data System (ADS)

Spool, A.; Forrest, J.

2008-12-01

Mapping of hard magnetic recording disks by TOF-SIMS was performed both to produce significant analytical results for the understanding of the disk surface and the head disk interface in hard disk drives, and as an example of a macroscopic non-rectangular mapping problem for the technique. In this study, maps were obtained by taking discrete samples of the disk surface at set intervals in R and Θ. Because both in manufacturing, and in the disk drive, processes that may affect the disk surface are typically circumferential in nature, changes in the surface are likely to be blurred in the Θ direction. An algorithm was developed to determine the optimum relative sampling ratio in R and Θ. The results confirm what the experience of the analysts suggested, that changes occur more rapidly on disks in the radial direction, and that more sampling in the radial direction is desired. The subsequent use of statistical methods principle component analysis (PCA), maximum auto-correlation factors (MAF), and the algorithm inverse distance weighting (IDW) are explored.

Helicity-dependent all-optical switching in hybrid metal-ferromagnet structures for ultrafast magnetic data storage

NASA Astrophysics Data System (ADS)

Cheng, Feng

The emerging Big Data era demands the rapidly increasing need for speed and capacity of storing and processing information. Standalone magnetic recording devices, such as hard disk drives (HDDs), have always been playing a central role in modern data storage and continuously advancing. Recognizing the growing capacity gap between the demand and production, industry has pushed the bit areal density in HDDs to 900 Giga-bit/square-inch, a remarkable 450-million-fold increase since the invention of the first hard disk drive in 1956. However, the further development of HDD capacity is facing a pressing challenge, the so-called superparamagnetic effect, that leads to the loss of information when a single bit becomes too small to preserve the magnetization. This requires new magnetic recording technologies that can write more stable magnetic bits into hard magnetic materials. Recent research has shown that it is possible to use ultrafast laser pulses to switch the magnetization in certain types of magnetic thin films. Surprisingly, such a process does not require an externally applied magnetic field that always exists in conventional HDDs. Furthermore, the optically induced magnetization switching is extremely fast, up to sub-picosecond (10 -12 s) level, while with traditional recording method the deterministic switching does not take place shorter than 20 ps. It's worth noting that the direction of magnetization is related to the helicity of the incident laser pulses. Namely, the right-handed polarized laser pulses will generate magnetization pointing in one direction while left-handed polarized laser pulses generate magnetization pointing in the other direction. This so-called helicity-dependent all-optical switching (HD-AOS) phenomenon can be potentially used in the next-generation of magnetic storage systems. In this thesis, I explore the HD-AOS phenomenon in hybrid metal-ferromagnet structures, which consist of gold and Co/Pt multilayers. The experiment results show that such CoPtAu hybrid structures have stable HD-AOS phenomenon over a wild range of repetition rates and peak powers. A macroscopic three-temperature model is developed to explain the experiment results. In order to reduce the magnetic bit size and power consumption to transform future magnetic data storage techniques, I further propose plasmonic-enhanced all-optical switching (PE-AOS) by utilizing the unique properties of the tight field confinement and strong local field enhancement that arise from the excitation of surface plasmons supported by judiciously designed metallic nanostructures. The preliminary results on PE-AOS are presented. Finally, I provide a discussion on the future work to explore the underline mechanism of the HD-AOS phenomenon in hybrid metal-ferromagnetic thin films. Different materials and plasmonic nanostructures are also proposed as further work.

First-principles investigation of Cr-doped Fe2B: Structural, mechanical, electronic and magnetic properties

NASA Astrophysics Data System (ADS)

Wei, Xiang; Chen, Zhiguo; Zhong, Jue; Wang, Li; Wang, Yipeng; Shu, Zhongliang

2018-06-01

The structural, mechanical, electronic and magnetic properties of Fe8-xCrxB4 (x = 0, 0.25, 0.5, 1, 2, 3, 4, 5, 6, 7 and 8) have been investigated by first-principles calculation. It was found that the calculated structural parameters are well consistent with available experimental data. Moreover, all studied compounds are thermodynamically stable phases. On the whole, the moduli of the compounds firstly increase and then decrease with the increase of Cr concentration, whereas the variation of hardness exhibits more fluctuations. All Cr-doped Fe2B have better ductility than Fe2B except Fe2Cr6B4 and Fe5Cr3B4. Interestingly, Fe4Cr4B4 is of not only the slightly larger hardness, but also much better ductility than Fe2B. As the Cr concentration is lower than 20 wt%, the hardness of Cr-doped Fe2B slightly decreases with increasing Cr, whereas the sharply increased hardness of (Fe, Cr)2B in Fe-B alloys or boriding layer should be attributed to the multiple alloying effects resulting from Cr and the other alloying elements. The electronic structures revealed that the Fe-B and/or Cr-B bonds are mainly responsible for their mechanical properties, and the M-N (M = Fe or Cr, N = Fe or Cr) bonds in 〈2 2 0〉 and 〈1 1 3〉 orientations show covalent character. Additionally, the magnetic moments (Ms) of the compounds do not monotonically decrease with increasing Cr.

From Compass to Hard Drive--Integrated Activities for Studying Magnets

ERIC Educational Resources Information Center

Dean, J.; Allwood, D. A.

2014-01-01

We describe a range of practical activities that allows students to investigate the properties and applications of magnets. The activities can be used in isolation or used together to build a rounded understanding of the subject area. The activities include simple demonstrations using common or inexpensive equipment, hands-on experiments for small…

Perpendicular magnetic anisotropy in granular multilayers of CoPd alloyed nanoparticles

NASA Astrophysics Data System (ADS)

Vivas, L. G.; Rubín, J.; Figueroa, A. I.; Bartolomé, F.; García, L. M.; Deranlot, C.; Petroff, F.; Ruiz, L.; González-Calbet, J. M.; Pascarelli, S.; Brookes, N. B.; Wilhelm, F.; Chorro, M.; Rogalev, A.; Bartolomé, J.

2016-05-01

Co-Pd multilayers obtained by Pd capping of pre-deposited Co nanoparticles on amorphous alumina are systematically studied by means of high-resolution transmission electron microscopy, x-ray diffraction, extended x-ray absorption fine structure, SQUID-based magnetometry, and x-ray magnetic circular dichroism. The films are formed by CoPd alloyed nanoparticles self-organized across the layers, with the interspace between the nanoparticles filled by the non-alloyed Pd metal. The nanoparticles show atomic arrangements compatible with short-range chemical order of L 10 strucure type. The collective magnetic behavior is that of ferromagnetically coupled particles with perpendicular magnetic anisotropy, irrespective of the amount of deposited Pd. For increasing temperature three magnetic phases are identified: hard ferromagnetic with strong coercive field, soft-ferromagnetic as in an amorphous asperomagnet, and superparamagnetic. Increasing the amount of Pd in the system leads to both magnetic hardness increment and higher transition temperatures. Magnetic total moments of 1.77(4) μB and 0.45(4) μB are found at Co and Pd sites, respectively, where the orbital moment of Co, 0.40(2) μB, is high, while that of Pd is negligible. The effective magnetic anisotropy is the largest in the capping metal series (Pd, Pt, W, Cu, Ag, Au), which is attributed to the interparticle interaction between de nanoparticles, in addition to the intraparticle anisotropy arising from hybridization between the 3 d -4 d bands associated to the Co and Pd chemical arrangement in a L 10 structure type.

An exceptionally bright flare from SGR 1806-20 and the origins of short-duration gamma-ray bursts.

PubMed

Hurley, K; Boggs, S E; Smith, D M; Duncan, R C; Lin, R; Zoglauer, A; Krucker, S; Hurford, G; Hudson, H; Wigger, C; Hajdas, W; Thompson, C; Mitrofanov, I; Sanin, A; Boynton, W; Fellows, C; von Kienlin, A; Lichti, G; Rau, A; Cline, T

2005-04-28

Soft-gamma-ray repeaters (SGRs) are galactic X-ray stars that emit numerous short-duration (about 0.1 s) bursts of hard X-rays during sporadic active periods. They are thought to be magnetars: strongly magnetized neutron stars with emissions powered by the dissipation of magnetic energy. Here we report the detection of a long (380 s) giant flare from SGR 1806-20, which was much more luminous than any previous transient event observed in our Galaxy. (In the first 0.2 s, the flare released as much energy as the Sun radiates in a quarter of a million years.) Its power can be explained by a catastrophic instability involving global crust failure and magnetic reconnection on a magnetar, with possible large-scale untwisting of magnetic field lines outside the star. From a great distance this event would appear to be a short-duration, hard-spectrum cosmic gamma-ray burst. At least a significant fraction of the mysterious short-duration gamma-ray bursts may therefore come from extragalactic magnetars.

Exchange spring in A1/L1{sub 0} FePt composite and its application in magnetic force microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Guoqing, E-mail: gqli@swu.edu.cn; Zhu, Yanyan, E-mail: zhubai@swu.edu.cn; Zhang, Yong

2015-02-23

This paper reported fabrication of Fe{sub x}Pt{sub 100-x} films with (001) epitaxy on MgO(100) substrates. The atomic percentage of Fe was changed within the range of x = 10–85 in order to search the optimal atomic ratio for achieving both high and isotropic-like coercivity. It was found that the Fe{sub 60}Pt{sub 40} film exhibited large coercivities exceeding 5 kOe along both in-plane and out-of-plane directions due to the formation of A1/L1{sub 0} FePt composite. A penta-domain model for hard/soft/hard exchange spring system was proposed to interpret the anomalous magnetization behaviors observed in Fe{sub 60}Pt{sub 40} sample. By using Fe{sub 60}Pt{sub 40} asmore » the magnetic coating layer on a probe of magnetic force microscope, the flux changes at a linear density of 1000 kfci could be readily observed at a resolution of ∼13 nm.« less

Zinc enhanced hard disk media

DOEpatents

Zou, Jie; Lambeth, David N.; Laughlin, David E.

2002-01-01

The present invention provides a magnetic recording media incorporating Zn containing layers in close proximity to a magnetic layer to provide media having increased coercivity and lower noise. The Zn containing layer can be incorporated in a rotating, translating or stationary recording media to operate in conjunction with magnetic transducing heads for recording and reading of magnetic data, as well as other applications. The magnetic recording medium of the invention preferably includes a Co or Co alloy film magnetic layer, underlayer structures to promote epitaxial crystalline structure in the magnetic layer, and a Zn containing layer to promote isolation between the magnetic grains. The medium can further include seed layers, underlayers, intermediate layers, and overlayers. The process of manufacture includes promoting diffusion of Zn to the magnetic layer grain boundaries.

Progressive magnetic softening of ferromagnetic layers in multilayer ferromagnet-nonmagnet systems and the role of granularity

NASA Astrophysics Data System (ADS)

Sahu, Siddharth S.; Siva, Vantari; Pradhan, Paresh C.; Nayak, Maheswar; Senapati, Kartik; Sahoo, Pratap K.

2017-06-01

We report a study of the structural and magnetic behavior of the topmost magnetic layer in a ferromagnet-nonmagnet (Co-Au) multilayer system. Glancing angle X-ray diffraction measurements performed on a series of multilayers showed a gradual decrease in the grain size of the topmost magnetic layer with the increasing number of bilayers. Concurrently, the magnetic hardness and magneto-crystalline anisotropy of the top Co layer were found to decrease, as observed by magneto-optical Kerr effect measurements. This magnetic softening has been discussed in the light of Herzer's random anisotropy model. Micromagnetic simulations of the multilayer system also corroborated these observations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doose, Charles; Jain, Animesh

The APS-U is planned to be a 4th generation hard X-ray light source utilizing a multi-bend achromat (MBA) magnet lattice. The MBA lattice will be installed in the existing APS storage ring enclosure. The stored electron beam will circulate clockwise when viewed from above. The X-ray beamlines will for the most part exit at the same source points as the present APS. This document defines the signs and conventions related to the APS-U MBA magnets. Included in this document are: the local magnet coordinate system, definitions of mechanical and magnetic centers, definitions of multipole field errors, magnetic roll angle, andmore » magnet polarities.« less

Properties of highly frustrated magnetic molecules studied by the finite-temperature Lanczos method

NASA Astrophysics Data System (ADS)

Schnack, J.; Wendland, O.

2010-12-01

The very interesting magnetic properties of frustrated magnetic molecules are often hardly accessible due to the prohibitive size of the related Hilbert spaces. The finite-temperature Lanczos method is able to treat spin systems for Hilbert space sizes up to 109. Here we first demonstrate for exactly solvable systems that the method is indeed accurate. Then we discuss the thermal properties of one of the biggest magnetic molecules synthesized to date, the icosidodecahedron with antiferromagnetically coupled spins of s = 1/2. We show how genuine quantum features such as the magnetization plateau behave as a function of temperature.

Particle/fluid simulations of an eruptive flare: Identifying the field-aligned currents responsible for the hard x-rays

NASA Astrophysics Data System (ADS)

Winglee, R. M.

1994-09-01

While magnetohydrodynamics (MHD) can provide a reasonable description of the overall magnetic reconnection that is believed to drive flares, additional, and often separate processes have to be envoked to in order to explain the electron acceleration that is responsible for many of the observed flare emissions. A new model that incorporates the dynamic coronal current sheets, the reconnection site, and possible electron acceleration processes is developed through the use of two-dimensional particle and modified two-fluid simulations. The specific example of an eruptive flare driven by the coalescence of flux tubes supported by prescribed photospheric current elements is evaluated. It is shown that the electrons and ions have differential trajectories through the coronal current sheet which leads to the development of additonal plasma currents that flow around the surface of the current sheet. These surface currents are explicitly neglected in MHD but they are vital to the flare dynamics because they divert current from the coronal current sheet into the chromosphere, producing an effective resistivity that aids the development of fast reconnection. Because the surface currents are in the plane of the magnetic field, electrons in them experience strong acceleration and can account for the observed hard X-ray emissions. Model predictions are compared with observed time profiles of hard X-ray emissions and Doppler shifts seen in soft X-ray line emissions and are able to account for such features as (1) the asymmetry in the rise and decay time of the hard X-rays, (2) the apparent delay between the largest Doppler shifts and the hard X-ray peak, and (3) the relatively low intensity of the blue-shifted component. The use of particle and fluid simulations is important because it provides different, but complementary treatments of the electron acceleration, the global magnetic morphology, and the flare current system.

Hard template synthesis of metal nanowires

PubMed Central

Kawamura, Go; Muto, Hiroyuki; Matsuda, Atsunori

2014-01-01

Metal nanowires (NWs) have attracted much attention because of their high electron conductivity, optical transmittance, and tunable magnetic properties. Metal NWs have been synthesized using soft templates such as surface stabilizing molecules and polymers, and hard templates such as anodic aluminum oxide, mesoporous oxide, carbon nanotubes. NWs prepared from hard templates are composites of metals and the oxide/carbon matrix. Thus, selecting appropriate elements can simplify the production of composite devices. The resulting NWs are immobilized and spatially arranged, as dictated by the ordered porous structure of the template. This avoids the NWs from aggregating, which is common for NWs prepared with soft templates in solution. Herein, the hard template synthesis of metal NWs is reviewed, and the resulting structures, properties and potential applications are discussed. PMID:25453031

Hard template synthesis of metal nanowires

NASA Astrophysics Data System (ADS)

Kawamura, Go; Muto, Hiroyuki; Matsuda, Atsunori

2014-11-01

Metal nanowires (NWs) have attracted much attention because of their high electron conductivity, optical transmittance and tunable magnetic properties. Metal NWs have been synthesized using soft templates such as surface stabilizing molecules and polymers, and hard templates such as anodic aluminum oxide, mesoporous oxide, carbon nanotubes. NWs prepared from hard templates are composites of metals and the oxide/carbon matrix. Thus, selecting appropriate elements can simplify the production of composite devices. The resulting NWs are immobilized and spatially arranged, as dictated by the ordered porous structure of the template. This avoids the NWs from aggregating, which is common for NWs prepared with soft templates in solution. Herein, the hard template synthesis of metal NWs is reviewed, and the resulting structures, properties and potential applications are discussed.

Hard template synthesis of metal nanowires.

PubMed

Kawamura, Go; Muto, Hiroyuki; Matsuda, Atsunori

2014-01-01

Metal nanowires (NWs) have attracted much attention because of their high electron conductivity, optical transmittance, and tunable magnetic properties. Metal NWs have been synthesized using soft templates such as surface stabilizing molecules and polymers, and hard templates such as anodic aluminum oxide, mesoporous oxide, carbon nanotubes. NWs prepared from hard templates are composites of metals and the oxide/carbon matrix. Thus, selecting appropriate elements can simplify the production of composite devices. The resulting NWs are immobilized and spatially arranged, as dictated by the ordered porous structure of the template. This avoids the NWs from aggregating, which is common for NWs prepared with soft templates in solution. Herein, the hard template synthesis of metal NWs is reviewed, and the resulting structures, properties and potential applications are discussed.

Magnetization of Paraffin-Based Magnetic Nanocolloids

NASA Astrophysics Data System (ADS)

Dikanskii, Yu. I.; Ispiryan, A. G.; Kunikin, S. A.; Radionov, A. V.

2018-01-01

Using paraffin-based magnetic nanocolloids as an example, the reasons for maxima in the temperature dependence of the magnetic susceptibility of magnetic colloids have been discussed. The behavior of these dependences in a wide temperature interval has been analyzed for colloids in solid and liquid states. It has been concluded that the maximum observed at the melting point of paraffin can be attributed to freezing Brownian degrees of freedom in magnetite coarse particles, the magnetic moment of which is intimately related to the solid matrix. The second main maximum, which arises in the solid state, is explained by the superparamagnetic-magnetically hard transition of most fine particles at lower temperatures. It has been noted that the flatness of this maximum results from the polydispersity of the magnetic nanoparticle ensemble.

An Arduino-Based Magnetometer

ERIC Educational Resources Information Center

McCaughey, Mike

2017-01-01

An Arduino-based system with a triple axis magnetometer chip may be used to plot both the strength and direction of the magnetic field of a magnet directly on a sheet of paper. Before taking measurements, it is necessary either to correct for or to eliminate soft and hard iron effects. The same sensor may be used to determine the presence of soft…

Reliability and validity of quantifying absolute muscle hardness using ultrasound elastography.

PubMed

Chino, Kentaro; Akagi, Ryota; Dohi, Michiko; Fukashiro, Senshi; Takahashi, Hideyuki

2012-01-01

Muscle hardness is a mechanical property that represents transverse muscle stiffness. A quantitative method that uses ultrasound elastography for quantifying absolute human muscle hardness has been previously devised; however, its reliability and validity have not been completely verified. This study aimed to verify the reliability and validity of this quantitative method. The Young's moduli of seven tissue-mimicking materials (in vitro; Young's modulus range, 20-80 kPa; increments of 10 kPa) and the human medial gastrocnemius muscle (in vivo) were quantified using ultrasound elastography. On the basis of the strain/Young's modulus ratio of two reference materials, one hard and one soft (Young's moduli of 7 and 30 kPa, respectively), the Young's moduli of the tissue-mimicking materials and medial gastrocnemius muscle were calculated. The intra- and inter-investigator reliability of the method was confirmed on the basis of acceptably low coefficient of variations (≤6.9%) and substantially high intraclass correlation coefficients (≥0.77) obtained from all measurements. The correlation coefficient between the Young's moduli of the tissue-mimicking materials obtained using a mechanical method and ultrasound elastography was 0.996, which was equivalent to values previously obtained using magnetic resonance elastography. The Young's moduli of the medial gastrocnemius muscle obtained using ultrasound elastography were within the range of values previously obtained using magnetic resonance elastography. The reliability and validity of the quantitative method for measuring absolute muscle hardness using ultrasound elastography were thus verified.

Reliability and Validity of Quantifying Absolute Muscle Hardness Using Ultrasound Elastography

PubMed Central

Chino, Kentaro; Akagi, Ryota; Dohi, Michiko; Fukashiro, Senshi; Takahashi, Hideyuki

2012-01-01

Muscle hardness is a mechanical property that represents transverse muscle stiffness. A quantitative method that uses ultrasound elastography for quantifying absolute human muscle hardness has been previously devised; however, its reliability and validity have not been completely verified. This study aimed to verify the reliability and validity of this quantitative method. The Young’s moduli of seven tissue-mimicking materials (in vitro; Young’s modulus range, 20–80 kPa; increments of 10 kPa) and the human medial gastrocnemius muscle (in vivo) were quantified using ultrasound elastography. On the basis of the strain/Young’s modulus ratio of two reference materials, one hard and one soft (Young’s moduli of 7 and 30 kPa, respectively), the Young’s moduli of the tissue-mimicking materials and medial gastrocnemius muscle were calculated. The intra- and inter-investigator reliability of the method was confirmed on the basis of acceptably low coefficient of variations (≤6.9%) and substantially high intraclass correlation coefficients (≥0.77) obtained from all measurements. The correlation coefficient between the Young’s moduli of the tissue-mimicking materials obtained using a mechanical method and ultrasound elastography was 0.996, which was equivalent to values previously obtained using magnetic resonance elastography. The Young’s moduli of the medial gastrocnemius muscle obtained using ultrasound elastography were within the range of values previously obtained using magnetic resonance elastography. The reliability and validity of the quantitative method for measuring absolute muscle hardness using ultrasound elastography were thus verified. PMID:23029231

Design and operation of a bio-inspired micropump based on blood-sucking mechanism of mosquitoes

NASA Astrophysics Data System (ADS)

Leu, Tzong-Shyng; Kao, Ruei-Hung

2018-05-01

The study is to develop a novel bionic micropump, mimicking blood-suck mechanism of mosquitos with a similar efficiency of 36%. The micropump is produced by using micro-electro-mechanical system (MEMS) technology, PDMS (polydimethylsiloxane) to fabricate the microchannel, and an actuator membrane made by Fe-PDMS. It employs an Nd-FeB permanent magnet and PZT to actuate the Fe-PDMS membrane for generating flow rate. A lumped model theory and the Taguchi method are used for numerical simulation of pulsating flow in the micropump. Also focused is to change the size of mosquito mouth for identifying the best waveform for the transient flow processes. Based on computational results of channel size and the Taguchi method, an optimization actuation waveform is identified. The maximum pumping flow rate is 23.5 μL/min and the efficiency is 86%. The power density of micropump is about 8 times of that produced by mosquito’s suction. In addition to using theoretical design of the channel size, also combine with Taguchi method and asymmetric actuation to find the optimization actuation waveform, the experimental result shows the maximum pumping flowrate is 23.5 μL/min and efficiency is 86%, moreover, the power density of micropump is 8 times higher than mosquito’s.

Nature's engineering: Giant magnetic exchange bias > 1T in a natural mineral

NASA Astrophysics Data System (ADS)

McEnroe, S. A.; Carter-Stiglitz, B.; Harrison, R. J.; Robinson, P.; McCammon, C.

2006-12-01

Magnetic exchange bias is a phenomenon whereby the hysteresis loop of a "soft" magnetic phase is shifted along the applied field axis by an amount of exchange due to interaction with a "hard" magnetic phase. Exchange bias is the subject of intense experimental and theoretical investigation because of its widespread technological applications and recent advances in manipulating nanoscale materials. Understanding the physical origin of exchange bias has been hampered, by the general uncertainty in the crystal and magnetic structure of the interface between hard and soft phases. Here we discuss a natural sample that has one of the largest exchange biases ever reported, nearly 1 Tesla (T) in a 1.5 T field and is the first documented example of exchange bias of this magnitude in a natural mineral. We demonstrate that exchange bias in this system is due to the interaction between coherently intergrown magnetic phases, formed through a natural process of phase separation during slow cooling. These extreme properties are found in a sample of titanohematite (15- 19 percent Ti-substitution ) from the 1 Gyr metamorphic rocks of the Modum district, south Norway. Low temperature magnetic measurements demonstrate the nature of the giant exchange bias. Transmission electron microscopy, electron microprobe analyses combined with Mossbauer measurements, at room and low temperature, are used to identify the interacting phases. The titanohematite contain ilmenite lamellae which are mostly sub-unit cell size. Fe-rutile is also present as an intergrowth phase.

Investigation of Thermo-Magnetic Processing in Application to Heavy Duty Truck Suspension Components

DOE Office of Scientific and Technical Information (OSTI.GOV)

Makiewicz, Kurt; Yurek, Theodore; Farrell, Brian

2016-04-19

Thermomagnetic processing (TMP) was examined as a methodology for increasing transformation rate during heat treatment in steel tubes. Two potential benefits were investigated, reduced energy consumption and improved mechanical properties. It is possible to reduce energy consumption with TMP by allowing tempering at lower temperatures and shorter times. Improved mechanical properties are possible by allowing a more copious distribution of fine carbides during tempering of martensite. Improved mechanical properties are also possible by quenching under a magnetic field after austenitization by formation of martensitic twins. The experiments in this work allowed for the following conclusions: the samples could not bemore » quenched fast enough to transform the entire wall thickness to martensite; the knee of the Continuous Cooling Curve (CCT) curve was shifted to the left when quenching following austenitizing in a magnetic field. The magnetic field during tempering did enhance the kinetics and allowed fine carbides to form. Since the through wall thickness was not hardened, the bulk mechanical properties were unaffected by the magnetic field. Hardness measurements after hardening showed that hardening in a magnetic field >0.5T resulted in a significant reduction in hardness. Combined with the inadequate cooling rate it was not possible to properly harden the samples. Tempering at 600 C without a magnetic field resulted in no formation of carbides, but tempering at 600 C and 450 C with a 1-2T field resulted in carbide formation in all samples.« less

Characterisation of case depth in induction-hardened medium carbon steels based on magnetic minor hysteresis loop measurement technique

NASA Astrophysics Data System (ADS)

He, Cunfu; Yang, Meng; Liu, Xiucheng; Wang, Xueqian; Wu, Bin

2017-11-01

The magnetic hysteresis behaviours of ferromagnetic materials vary with the heat treatment-induced micro-structural changes. In the study, the minor hysteresis loop measurement technique was used to quantitatively characterise the case depth in two types of medium carbon steels. Firstly, high-frequency induction quenching was applied in rod samples to increase the volume fraction of hard martensite to the soft ferrite/pearlite (or sorbite) in the sample surface. In order to determine the effective and total case depth, a complementary error function was employed to fit the measured hardness-depth profiles of induction-hardened samples. The cluster of minor hysteresis loops together with the tangential magnetic field (TMF) were recorded from all the samples and the comparative study was conducted among three kinds of magnetic parameters, which were sensitive to the variation of case depth. Compared to the parameters extracted from an individual minor loop and the distortion factor of the TMF, the magnitude of three-order harmonic of TMF was more suitable to indicate the variation in case depth. Two new minor-loop coefficients were introduced by combining two magnetic parameters with cumulative statistics of the cluster of minor-loops. The experimental results showed that the two coefficients monotonically linearly varied with the case depth within the carefully selected magnetisation region.

Effect of ball-milling surfactants on the interface chemistry in hot-compacted SmCo5 magnets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, WF; Sepehri-Amin, H; Zheng, LY

2012-11-01

Anisotropic SmCo5 nanoflakes prepared by high-energy ball-milling with surfactants have great potential in applications for high-performance nanocomposite magnets. For such "nanocomposite" applications, the surface structure and chemistry of nanoflakes are crucial for achieving high coercivity. In this study, hot-pressed samples from anisotropic SmCo5 nanoflakes, ball-milled with different surfactants, oleic acid (OA) and oleylamine (OY), were investigated. Interface layers between the SmCo5 nanoflakes were found to consist of samarium oxides and a soft magnetic Co phase. These surface layers contribute to the degradation of hard magnetic performance, which is confirmed by scanning transmission electron microscopy-energy dispersive X-ray spectroscopy analysis of themore » cross-section of a single flake ball-milled with OA. Samples milled with OY show a much thinner interface layer in compacted samples, which means that the surface degradation during ball-milling with OY is much less than that with OA. The results show clearly that the choice of proper surfactant and the control of processing parameters are the key factors for improving the surface condition of the nanoflakes and the resulting hard magnetic properties. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.« less

Failure Analysis and Magnetic Evaluation of Tertiary Superheater Tube Used in Gas-Fired Boiler

NASA Astrophysics Data System (ADS)

Mohapatra, J. N.; Patil, Sujay; Sah, Rameshwar; Krishna, P. C.; Eswarappa, B.

2018-02-01

Failure analysis was carried out on a prematurely failed tertiary superheater tube used in gas-fired boiler. The analysis includes a comparative study of visual examination, chemical composition, hardness and microstructure at failed region, adjacent and far to failure as well as on fresh tube. The chemistry was found matching to the standard specification, whereas the hardness was low in failed tube compared to the fish mouth opening region and the fresh tube. Microscopic examination of failed sample revealed the presence of spheroidal carbides of Cr and Mo predominantly along the grain boundaries. The primary cause of failure is found to be localized heating. Magnetic hysteresis loop (MHL) measurements were carried out to correlate the magnetic parameters with microstructure and mechanical properties to establish a possible non-destructive evaluation (NDE) for health monitoring of the tubes. The coercivity of the MHL showed a very good correlation with microstructure and mechanical properties deterioration enabling a possible NDE technique for the health monitoring of the tubes.

Magnetization reversal mechanisms in hybrid resin-bonded Nd Fe B magnets

NASA Astrophysics Data System (ADS)

Plusa, D.; Dospial, M.; Slusarek, B.; Kotlarczyk, U.

2006-11-01

The magnetic properties of isotropic epoxy resin-bonded magnets prepared by mixing a hard magnetic powder made from melt quenched Nd-Fe-Co-B ribbons and a soft magnetic iron powder have been examined. The magnetization reversal processes and the magnetic parameters have been studied by the measurement of the virgin magnetization curves, the major and minor hysteresis loops and sets of recoil curves. From these recoil curves the field dependence of the reversible and irreversible magnetization components during the magnetization and demagnetization processes has been derived. The remanence relationship was used to study the nature of magnetic interaction between the grains. A study of interaction domains was conducted using optical microscopy. Groups of domains, each over several grains, were observed. It was found that the reversal process in the samples investigated involves the rotation of magnetization vectors in the iron powder grains and pinning of domain walls at the MQP-B grain boundaries.

Disorder induced magnetism and electrical conduction in La doped Ca2FeMoO6 double perovskite

NASA Astrophysics Data System (ADS)

Poddar, Asok; Bhowmik, R. N.; Muthuselvam, I. Panneer

2010-11-01

We report the magnetism and electrical transport properties of La doped Ca2FeMoO6 double perovskite. Reduction in magnetic moment, nonmonotonic variation in magnetic ordering temperature (TC), increasing magnetic hardness, low temperature resistivity upturn, and loss of metallic conductivity are some of the major changes that we observed due to La doping induced disorder in double perovskite structure. The increase in magnetic disorder in La doped samples and its effect on TC is more consistent with the mean field theory. The modification in electronic band structure due to La doping is understood by establishing a correlation between the temperature dependence of electrical conductivity and thermoelectric power.

Magnetic and structural characterization of ultra-thin Fe (222) films

NASA Astrophysics Data System (ADS)

Loving, Melissa G.; Brown, Emily E.; Rizzo, Nicholas D.; Ambrose, Thomas F.

2018-05-01

Varied thickness body centered cubic (BCC) ultrathin Fe films (10-50Å) have been sputter deposited onto Si (111) substrates. BCC Fe with the novel (222) texture was obtained by H- terminating the Si (111) starting substrate then immediately depositing the magnetic films. Structural results derived from grazing incidence x-ray diffraction and x-ray reflectivity confirm the crystallographic texture, film thickness, and interface roughness. Magnetic results indicate that Fe (222) exhibits soft magnetic switching (easy axis), high anisotropy (hard axis), which is maintained across the thickness range, and a positive magnetostriction (for the thicker film layers). The observed soft magnetic switching in this system makes it an ideal candidate for future magnetic memory development as well as other microelectronics applications that utilize magnetic materials.

Exploration of dysprosium: the most critical element for Japan

NASA Astrophysics Data System (ADS)

Watanabe, Y.

2012-04-01

Dysprosium (Dy), one of the heavy rare earth elements, is used mainly as an additive for NdFeB permanent magnets which are installed in various modern industrial products such as voice coil motors in computers, factory automation machinery, hybrid and electric vehicles, home electronics, and wind turbine, to improve heat resistance of the magnets. Dy has been produced about 2,000t per year from the ores from ion adsorption type deposits in southern China. However, the produced amount of Dy was significantly reduced in 2011 in China due to reservation of heavy rare earth resources and protection of natural environment, resulting in soaring of Dy price in the world. In order to respond the increasing demand of Dy, unconventional supply sources are inevitably developed, in addition to heavy rare earth enriched ion adsorption type deposits outside China. Heavy rare earth elements including Dy are dominantly hosted in xenotime, fergusonite, zircon, eudialyte, keiviite, kainosite, iimoriite, etc. Concentration of xenotime is found in placer deposits in Malaysia and India, hydrothermal deposits associated with unconformity-type uranium mineralization (Athabasca basin in Canada, Western Australia), iron-oxide fluorite mineralization (South Africa) and Sn-bearing alkaline granite (Brazil). Zircon and fergusontie concentration is found as igneous and hydrothermal products in peralkaline syenite, alkaline granite and pegmatite (e.g., Nechalacho in Canada). Eudialyte concentration is found in some peralkaline syenite bodies in Greenland, Canada, Sweden and Russia. Among these sources, large Dy resources are estimated in the deposits hosted in peralkaline rocks (Nechalacho: 79,000t, Kvanefjeld: 49,000t, Norra Karr: 15,700t, etc.) compared to the present demand of Dy. Thus, Dy will be supplied from the deposits associated with peralkaline and alkaline deposits in future instead of ion adsorption type deposits in southern China.

An energy harvesting converter to power sensorized total human knee prosthesis

NASA Astrophysics Data System (ADS)

Luciano, V.; Sardini, E.; Serpelloni, M.; Baronio, G.

2014-02-01

Monitoring the internal loads acting in a total knee prosthesis (TKP) is fundamental aspect to improve their design. One of the main benefits of this improvement is the longer duration of the tibial inserts. In this work, an electromagnetic energy harvesting system, which is implantable in a TKP, is presented. This is conceived for powering a future implantable system that is able to monitor the loads (and, possibly, other parameters) that could influence the working conditions of a TKP in real-time. The energy harvesting system (EHS) is composed of two series of NdFeB magnets, positioned into each condyle, and a coil that is placed in a pin of the tibial insert and connected to an implantable power management circuit. The magnetic flux variation and the induced voltage are generated by the knee's motion. A TKP prototype has been realized in order to reproduce the knee mechanics and to test the EHS performance. In the present work, the experimental results are obtained by adopting a resistive load of 2.2 kΩ, in order to simulate a real implanted autonomous system with a current consumption of 850 µA and voltage of 2 V. The tests showed that, after 7 to 30 s of walking with a gait cycle frequency of about 1.0 Hz, the EHS can generate an energy of about 70 μJ, guaranteeing a voltage between 2 and 1.4 V every 7.6 s. With this prototype we can verify that it is possible to power for 16 ms a circuit having a power consumption of 1.7 mW every 7.6 s. The proposed generator is a viable solution to power an implanted electronic system that is conceived for measuring and transmitting the TKP load parameters.

Assessment of recovery and recrystallisation behaviours of cold rolled IF steel through non-destructive electromagnetic characterisation

NASA Astrophysics Data System (ADS)

Roy, Rajat K.; Dutta, Siuli; Panda, Ashis K.; Rajinikanth, V.; Das, Swapan K.; Mitra, Amitava; Strangwood, M.; Davis, Claire L.

2018-07-01

The recovery and recrystallisation behaviours of cold rolled IF steel have been investigated by destructive (optical microscopy and hardness) and non-destructive electromagnetic sensor, (which allows direct measurement of strip samples with no surface preparation) techniques. The onset and completion of recrystallisation are clearly monitored through destructive techniques of optical microscopy and hardness measurements. The nucleation of new recrystallised grains is observed in the sample annealed at 600 °C/15 min, while completion of recrystallisation takes place at 700 °C/15 min. The destructive techniques are not very accurate in monitoring recovery, for example, changes in hardness of <20% are seen. In contrast, the magnetic properties of annealed steel show the onsets of both recovery and recrystallisation, with recovery accounting for ≈60% change in the coercivity value. Therefore, the measurement of magnetic softening through an electromagnetic sensor acts a crucial role for understanding recovery and recrystallisation behaviours of steels during industrial processing. The present investigation is aimed not only for controlling product quality but also saving characterisation time through off line monitoring during steel processing at industry.

Measurements of Surfactant Squeeze-out Using Magnetically-Levitated Liquid Bridges

NASA Technical Reports Server (NTRS)

Rosenblatt, Charles

2004-01-01

Liquid bridges: Columns of liquid supported by two solid surfaces. These are generally opposing right circular cylinders in 0g. For a cylindrical bridge of length L and diameter d, in zero g, the maximum slenderness ratio Lambda [L/d] = pi [Rayleigh]. In the presence of gravity the cylindrical shape of an axisymmetric bridge tends to deform. Fluid has a volumetric magnetic susceptibility X. Magnetic levitation has numerous applications in studies of fluids, "soft" and "hard" condensed matter physics, and biophysics

Control of magnetic anisotropy in (Ga,Mn)as by lithography-induced strain relaxation.

PubMed

Wenisch, J; Gould, C; Ebel, L; Storz, J; Pappert, K; Schmidt, M J; Kumpf, C; Schmidt, G; Brunner, K; Molenkamp, L W

2007-08-17

We report control of magnetic anisotropy in epitaxial (Ga,Mn)As by anisotropic strain relaxation in patterned structures. The strain in the structures is characterized using reciprocal space mapping by x-ray techniques. The magnetic anisotropy before patterning of the layer, which shows biaxial easy axes along [100] and [010], is replaced by a hard axis in the direction of large elastic strain relaxation and a uniaxial easy axis in the direction where pseudomorphic conditions are retained.

Flare activity, sunspot motions, and the evolution of vector magnetic fields in Hale region 17244

NASA Technical Reports Server (NTRS)

Neidig, Donald F.; Hagyard, Mona J.; Machado, Marcos E.; Smith, Jesse B., Jr.

1986-01-01

The magnetic and dynamical circumstances leading to the 1B/M4 flare of November 5, 1980 are studied, and a strong association is found between the buildup of magnetic shear and the onset of flare activity within the active region. The development of shear, as observed directly in vector magnetograms, is consistent in detail with the dynamical history of the active region and identifies the precise location of the optical and hard-X-ray kernels of the flare emission.

(BRI) Direct and Inverse Design Optimization of Magnetic Alloys with Minimized Use of Rare Earth Elements

DTIC Science & Technology

2016-02-02

Earths ”, MS&T15-Materials Science and Technology 2015 Conference, Columbus, Ohio, October 4-8, 2015. 3. Dulikrvich, G.S., Reddy, S., Orlande, H.R.B...Schwartz, J.and Koch, C.C., “Multi-Objective Design and Optimization of Hard Magnetic Alloys Free of Rare Earths ”, MS&T15-Materials Science and Technology...AFRL-AFOSR-VA-TR-2016-0091 (BRI) Direct and Inverse Design Optimization of Magnetic Alloys with Minimized Use of Rare Earth Elements George

Effects of Surface Roughness and Aging on the Electrical Contact Resistance and Residual Stress in Gold-Nickel-Copper Connector Materials

DTIC Science & Technology

2014-12-01

with nickel coatings can result in compressive stresses, and the deposition of gold with small amounts of cobalt increase the coating hardness/wear...magnetic metal. In the literature, there are a few different approaches to allow for the sputter deposition of magnetic materials including: doping ...the target (i.e., nickel doped with vanadium, typically on the order of 7- 9% [19]) to the point that it is no longer magnetic, heating the target

Correlative Magnetic Imaging of Heat-Assisted Magnetic Recording Media in Cross Section Using Lorentz TEM and MFM

DOE PAGES

Kim, Taeho Roy; Phatak, Charudatta; Petford-Long, Amanda K.; ...

2017-10-23

In order to increase the storage density of hard disk drives, a detailed understanding of the magnetic structure of the granular magnetic layer is essential. Here, we demonstrate an experimental procedure of imaging recorded bits on heat-assisted magnetic recording (HAMR) media in cross section using Lorentz transmission electron microscopy (TEM). With magnetic force microscopy and focused ion beam (FIB), we successfully targeted a single track to prepare cross-sectional TEM specimens. Then, we characterized the magnetic structure of bits with their precise location and orientation using Fresnel mode of Lorentz TEM. Here, this method can promote understanding of the correlation betweenmore » bits and their material structure in HAMR media to design better the magnetic layer.« less

Correlative Magnetic Imaging of Heat-Assisted Magnetic Recording Media in Cross Section Using Lorentz TEM and MFM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Taeho Roy; Phatak, Charudatta; Petford-Long, Amanda K.

In order to increase the storage density of hard disk drives, a detailed understanding of the magnetic structure of the granular magnetic layer is essential. Here, we demonstrate an experimental procedure of imaging recorded bits on heat-assisted magnetic recording (HAMR) media in cross section using Lorentz transmission electron microscopy (TEM). With magnetic force microscopy and focused ion beam (FIB), we successfully targeted a single track to prepare cross-sectional TEM specimens. Then, we characterized the magnetic structure of bits with their precise location and orientation using Fresnel mode of Lorentz TEM. Here, this method can promote understanding of the correlation betweenmore » bits and their material structure in HAMR media to design better the magnetic layer.« less

Spatial distribution characteristics of magnetization in exchange-coupled bilayers with mutually orthogonal anisotropies

NASA Astrophysics Data System (ADS)

Xiang, Y.; Chen, C. W.

2017-05-01

The magnetization distribution of a bilayer exchange spring system with mutually orthogonal anisotropies was investigated by micromagnetic simulation. Results showed that the spatial change rate of the magnetization direction could be engineered by varying the material parameters, layer thicknesses, and magnetic field. When no magnetic field is applied, this angular change rate is determined by three parameter ratios: a ratio of the exchange energy and anisotropy constants of both layers and two thickness ratios of both layers. If these three ratios are kept invariant, the ratio of the angular change of the soft layer over the hard layer will remain the same. When a magnetic field is applied, two more ratios concerning the magnetic field should be added to determine the spatial angular change of the magnetization direction.

An Arduino-Based Magnetometer

NASA Astrophysics Data System (ADS)

McCaughey, Mike

2017-05-01

An Arduino-based system with a triple axis magnetometer chip may be used to plot both the strength and direction of the magnetic field of a magnet directly on a sheet of paper. Before taking measurements, it is necessary either to correct for or to eliminate soft and hard iron effects. The same sensor may be used to determine the presence of soft iron effects.

Underwater Concrete Inspection Equipment

DTIC Science & Technology

1991-04-01

nondestructive testing of con- crete waterfront structures. One instrument is a magnetic rebar locator that locates rebar in concrete structures and measures the...amount of con- crete cover over the rebar . Another instrument is a rebound hammer that measures the surface hardness of the concrete . The third...development of three specialized instruments for the underwater nondestructive testing or concrete waterfront structures. One instrument is a magnetic rebar

Halbach array type focusing actuator for small and thin optical data storage device

NASA Astrophysics Data System (ADS)

Lee, Sung Q.; Park, Kang-Ho; Paek, Mun Chul

2004-09-01

The small form factor optical data storage devices are developing rapidly nowadays. Since it is designed for portable and compatibility with flesh memory, its components such as disk, head, focusing actuator, and spindle motor should be assembled within 5 mm. The thickness of focusing actuator is within 2 mm and the total working range is +/-100um, with the resolution of less than 1μm. Since the thickness is limited tightly, it is hard to place the yoke that closes the magnetic circuit and hard to make strong flux density without yoke. Therefore, Halbach array is adopted to increase the magnetic flux of one side without yoke. The proposed Halbach array type focusing actuator has the advantage of thin actuation structure with sacrificing less flex density than conventional magnetic array. The optical head unit is moved on the swing arm type tracking actuator. Focusing coil is attached to swing arm, and Halbach magnet array is positioned at the bottom of deck along the tracking line, and focusing actuator exerts force by the Fleming's left hand rule. The dynamics, working range, control resolution of focusing actuator are analyzed and performed.

Adhesion in ceramics and magnetic media

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa

1989-01-01

When a ceramic is brought into contact with a metal or a polymeric material such as a magnetic medium, strong bonds form between the materials. For ceramic-to-metal contacts, adhesion and friction are strongly dependent on the ductility of the metals. Hardness of metals plays a much more important role in adhesion and friction than does the surface energy of metals. Adhesion, friction, surface energy, and hardness of a metal are all related to its Young's modulus and shear modulus, which have a marked dependence on the electron configuration of the metal. An increase in shear modulus results in a decrease in area of contact that is greater than the corresponding increase in surface energy (the fond energy) with shear modulus. Consequently, the adhesion and friction decrease with increasing shear modulus. For ceramics in contact with polymeric magnetic tapes, environment is extremely important. For example, a nitrogen environment reduces adhesion and friction when ferrite contacts polymeric tape, whereas a vacuum environment strengthens the ferrite-to-tape adhesion and increases friction. Adhesion and friction are strongly dependent on the particle loading of the tape. An increase in magnetic particle concentration increases the complex modulus of the tape, and a lower real area of contact and lower friction result.

Stress-relaxation heat treatment in FeSiBNb amorphous alloy: Thermal, microstructure, nanomechanical and magnetic texture measurements

NASA Astrophysics Data System (ADS)

Lashgari, H. R.; Cadogan, J. M.; Kong, C.; Tang, C.; Doherty, C.; Chu, D.; Li, S.

2018-06-01

In the present study, the effect of stress-relaxation treatment (Tstress-relaxation < Tglass transition) on the magnetic texture, nanomechanical properties, and variation of free-volume in FeSiBNb amorphous alloy was investigated using Mössbauer spectroscopy, nanoindentation, dynamic mechanical analysis (DMA), and positron annihilation lifetime spectroscopy (PALS) techniques. It was shown that stress-relaxation treatment slightly improved the magnetic texture by 6% at T ≪Tg due to small-scale displacement of atoms whereas the magnetic texture was deteriorated due to thermal treatment at temperatures around the glass transition point (large-scale displacement of atoms). According to nanoindentation results, the hardness (H) and reduced modulus (Er) of the amorphous ribbon increased by 15% and 13%, respectively, after stress-relaxation treatment at 716 K for 5 min. Increasing the stress-relaxation time from 5 min to 60 min at 716 K resulted in decreases in the hardness and reduced modulus which are attributed to the increase of free-volume defects (increase of τ2 lifetime measured by PALS). Transmission electron microscopy (TEM) showed the formation of extremely fine embryos of α-Fe (3-5 nm in size) after stress-relaxation treatment.

Multi-wavelength Observation of Filament Eruption associated with M-class Flare

NASA Astrophysics Data System (ADS)

Kim, S.; Yurchyshyn, V.; Jiang, C.

2017-12-01

We have investigated a M-class flare associated with filament eruption which developed into a Halo CME. The M-class flare occurred in 2011 August 4. For this study, we used the Nobryama Radioheliograph (NoRH) 17 and 34 GHz, RHESSI Hard X-ray satellite, and Atmo- spheric Imaging Assembly (AIA) and the Heliospheric Magentic Imager(HMI) onboard the Solar Dynamic Observatory (SDO). During the pre-eruption phase, clear nonthermal emission was detected in microwaves of NoRH and hard-X-ray of RHESSI. At the moment that the nonthermal emission start, the nonthermal sources appeared at the one edge of the filament structure on a polarity inversion line, and the slowing rising filament structure in AIA 94A underwent a sudden acceleration on its ascendance. Magnetograms showed converging motion of magnetic elements at the source position of HXR and MW. Based on the results, we conjecture that the plausible trigger of the filament eruption is magnetic reconnections at the HXR source position by converging motion of magnetic elements. In addition, we will discuss on the magnetic flux variation before and after the eruption based on the result of Nonlinear force-free field model.

Note: A simple vibrating orifice monodisperse droplet generator using a hard drive actuator arm

NASA Astrophysics Data System (ADS)

Kosch, Sebastian; Ashgriz, Nasser

2015-04-01

We propose that the rotary voice coil actuators found in magnetic hard drives are fit to supercede loudspeakers as expedient vibration sources in the laboratory setting. A specific use case is the excitation of a liquid jet to induce controlled breakup into monodisperse droplets. Like loudspeakers, which are typically used for prototyping such devices, hard drive actuators are cheap and ubiquitous, but they are less unwieldy and supply greater amplitudes without producing noise. Frequencies between 0 and 17 kHz, and likely beyond, can be reproduced reliably. No machining tools or amplifying electronics are needed for the construction and operation of the presented droplet generator.

Controlled modulation of hard and soft X-ray induced tunneling currents utilizing coaxial metal-insulator-metal probe tips

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cummings, Marvin; Shirato, Nozomi; Kersell, Heath

Here, the effect of a local external electric field on the barrier potential of a tunneling gap is studied utilizing an emerging technique, synchrotron x-ray scanning tunneling microscopy. Here, we demonstrate that the shape of the potential barrier in the tunneling gap can be altered by a localized external electric field, generated by voltages placed on the metallic outer shield of a nanofabricated coaxial metal-insulator-metal tip, resulting in a controlled linear modulation of the tunneling current. Experiments at hard and soft x-ray synchrotron beamlines reveal that both the chemical contrast and magnetic contrast signals measured by the tip can bemore » drastically enhanced, resulting in improved local detection of chemistry and magnetization at the surface.« less

Spatial and temporal characteristics of flare energy release determined from X-ray and radio imaging observations

NASA Technical Reports Server (NTRS)

Hernandez, A. M.; Machado, M. E.; Vilmer, N.; Trottet, G.

1986-01-01

Using the Hard X-ray Imaging Spectrometer (HXIS) from the Solar Maximum Mission Satellite, the morphological aspects and temporal evolution of three major flares which occurred on June 29, 1980 are studied. One of these events, observed at 10:40 UT, is analyzed in particular detail, including Hard X-ray Burst Spectrometer (HXRBS) data and metric wavelength data from the Nancay radioheliograph. The flares occurred during the interaction of two distinct magnetic structures. There is an early onset phase during which there is a weak level of particle acceleration, perhaps accompanied by strong heating within the magnetic interaction region. The impulsive phase of high power energy release is associated with a major interaction between the two structures and accompanied by strong acceleration and heating.

Controlled modulation of hard and soft X-ray induced tunneling currents utilizing coaxial metal-insulator-metal probe tips

DOE PAGES

Cummings, Marvin; Shirato, Nozomi; Kersell, Heath; ...

2017-01-05

Here, the effect of a local external electric field on the barrier potential of a tunneling gap is studied utilizing an emerging technique, synchrotron x-ray scanning tunneling microscopy. Here, we demonstrate that the shape of the potential barrier in the tunneling gap can be altered by a localized external electric field, generated by voltages placed on the metallic outer shield of a nanofabricated coaxial metal-insulator-metal tip, resulting in a controlled linear modulation of the tunneling current. Experiments at hard and soft x-ray synchrotron beamlines reveal that both the chemical contrast and magnetic contrast signals measured by the tip can bemore » drastically enhanced, resulting in improved local detection of chemistry and magnetization at the surface.« less

On the measurement of magnetic viscosity

NASA Astrophysics Data System (ADS)

Serletis, C.; Efthimiadis, K. G.

2012-08-01

This work is an investigation of the experimental method used for measuring the magnetic viscosity in a hard ferromagnetic material, i.e. the recording of the magnetization under constant applied field and temperature, after the material has been magnetically saturated. It investigates how the experimental results are affected by the initial conditions of the method (saturation field, field change rate and field oscillation prior to its stabilization), and by minor variations of field and temperature during the recording. Based on the arising conclusions and the use of a more complex fitting function of measurements, the accuracy and repeatability of experimental results is improved.

Steel characteristics measurement system using Barkhausen jump sum rate and magnetic field intensity and method of using same

DOEpatents

Kohn, Gabriel; Hicho, George; Swartzendruber, Lydon

1997-01-01

A steel hardness measurement system and method of using same are provided for measuring at least one mechanical or magnetic characteristic of a ferromagnetic sample as a function of at least one magnetic characteristic of the sample. A magnetic field generator subjects the sample to a variable external magnetic field. The magnetic field intensity of the magnetic field generated by the magnetic field generating means is measured and a signal sensor is provided for measuring Barkhausen signals from the sample when the sample is subjected to the external magnetic field. A signal processing unit calculates a jump sum rate first moment as a function of the Barkhausen signals measured by the signal sensor and the magnetic field intensity, and for determining the at least one mechanical or magnetic characteristic as a function of the jump sum rate first moment.

Steel characteristics measurement system using Barkhausen jump sum rate and magnetic field intensity and method of using same

DOEpatents

Kohn, G.; Hicho, G.; Swartzendruber, L.

1997-04-08

A steel hardness measurement system and method of using same are provided for measuring at least one mechanical or magnetic characteristic of a ferromagnetic sample as a function of at least one magnetic characteristic of the sample. A magnetic field generator subjects the sample to a variable external magnetic field. The magnetic field intensity of the magnetic field generated by the magnetic field generating means is measured and a signal sensor is provided for measuring Barkhausen signals from the sample when the sample is subjected to the external magnetic field. A signal processing unit calculates a jump sum rate first moment as a function of the Barkhausen signals measured by the signal sensor and the magnetic field intensity, and for determining the at least one mechanical or magnetic characteristic as a function of the jump sum rate first moment. 7 figs.

Reading magnetic ink patterns with magnetoresistive sensors

NASA Astrophysics Data System (ADS)

Merazzo, K. J.; Costa, T.; Franco, F.; Ferreira, R.; Zander, M.; Türr, M.; Becker, T.; Freitas, P. P.; Cardoso, S.

2018-05-01

Information storage and monitoring relies on sensitive transducers with high robustness and reliability. This paper shows a methodology enabling the qualification of magnetic sensors for magnetic pattern readout, in applications different than hard disk magnetic recording. A magnetic tunnel junction MTJ sensor was incorporated in a reader setup for recognition of the magnetization of patterned arrays made of CoCrPt thin films and magnetic ink. The geometry of the sensor (in particular, the footprint and vertical distance to the media) was evaluated for two sensor configurations. The readout conditions were optimized to cope for variable media field intensity, resulting from CoCrPt film or magnetic ink thickness, with fixed reading distance and dimensions of the pattern. The calibration of the ink magnetic signal could be inferred from the analytical calculations carried out to validate the CoCrPt results.

Hard magnetic property enhancement of Co{sub 7}Hf-based ribbons by boron doping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, H. W.; Liao, M. C.; Shih, C. W.

2014-11-10

Hard magnetic property enhancement of melt spun Co{sub 88}Hf{sub 12} ribbons by boron doping is demonstrated. B-doping could not only remarkably enhance the magnetic properties from energy product ((BH){sub max}) of 2.6 MGOe and intrinsic coercivity ({sub i}H{sub c}) of 1.5 kOe for B-free Co{sub 88}Hf{sub 12} ribbons to (BH){sub max} = 7.7 MGOe and {sub i}H{sub c} = 3.1 kOe for Co{sub 85}Hf{sub 12}B{sub 3} ribbons but also improve the Curie temperature (T{sub C}) of 7:1 phase. The (BH){sub max} value achieved in Co{sub 85}Hf{sub 12}B{sub 3} ribbons is the highest in Co-Hf alloy ribbons ever reported, which is about 15% higher thanmore » that of Co{sub 11}Hf{sub 2}B ribbons spun at 16 m/s [M. A. McGuire, O. Rios, N. J. Ghimire, and M. Koehler, Appl. Phys. Lett. 101, 202401 (2012)]. The structural analysis confirms that B enters the orthorhombic Co{sub 7}Hf (7:1) crystal structure as interstitial atoms, forming Co{sub 7}HfB{sub x}, in the as-spun state. Yet B may diffuse out from the 7:1 phase after post-annealing, leading to the reduction of Curie temperature and the magnetic properties. The uniformly refined microstructure with B-doping results in high remanence (B{sub r}) and improves the squareness of demagnetization curve. The formation of interstitial-atom-modified Co{sub 7}HfB{sub x} phase and the microstructure refinement are the main reasons to give rise to the enhancement of hard magnetic properties in the B-containing Co{sub 7}Hf-based ribbons.« less

Hard permanent magnet development trends and their application to A.C. machines

NASA Technical Reports Server (NTRS)

Mildrum, H. F.

1981-01-01

The physical and magnetic properties of Mn-Al-C, Fe-Cr-Co, and RE-TM (rare earth-transition metal intermetallics) in polymer and soft metal bonded or sintered form are considered for ac circuit machine usage. The manufacturing processes for the magnetic materials are reviewed, and the mechanical and electrical properties of the magnetic materials are compared, with consideration given to the reference Alnico magnet. The Mn-Al-C magnets have the same magnetic properties and costs as Alnico units, operate well at low temperatures, but have poor high temperature performance. Fe-Cr-Co magnets also have comparable cost to Alnico magnets, and operate at high or low temperature, but are brittle, expensive, and contain Co. RE-Co magnets possess a high energy density, operate well in a wide temperature range, and are expensive. Recommendation for exploring the rare-earth alternatives are offered.

Magnetic characteristics of CoPd and FePd antidot arrays on nanoperforated Al2O3 templates

NASA Astrophysics Data System (ADS)

Maximenko, A.; Fedotova, J.; Marszałek, M.; Zarzycki, A.; Zabila, Y.

2016-02-01

Hard magnetic antidot arrays show promising results in context of designing of percolated perpendicular media. In this work the technology of magnetic FePd and CoPd antidot arrays fabrication is presented and correlation between surface morphology, structure and magnetic properties is discussed. CoPd and FePd antidot arrays were fabricated by deposition of Co/Pd and Fe/Pd multilayers (MLs) on porous anodic aluminum oxide templates with bowl-shape cell structure with inclined intercellular regions. FePd ordered L10 structure was obtained by successive vacuum annealing at elevated temperatures (530 °C) and confirmed by XRD analysis. Systematic analysis of magnetization curves evidenced perpendicular magnetic anisotropy of CoPd antidot arrays, while FePd antidot arrays revealed isotropic magnetic anisotropy with increased out-of-plane magnetic contribution. MFM images of antidots showed more complicated contrast, with alternating magnetic dots oriented parallel and antiparallel to tip magnetization moment.

Operating characteristics of HTS power supply for and improving temporal stability of coated conductor magnet in liquid helium

NASA Astrophysics Data System (ADS)

Park, D. K.; Kim, Y. J.; Yang, S. E.; Kwon, N. Y.; Lee, H. G.; Ko, T. K.

2009-10-01

High temperature superconducting (HTS) magnets have been studied for insert coils of high field nuclear magnetic resonance (NMR) magnets but the temporal stability required for NMR is hard to achieve due to low index value and high joint resistance. In this research, the HTS power supply with magnets using coated conductor (CC) was investigated and tested in helium cryogenic system. All joints were conducted by soldering after etching stabilizer of the CC to minimize joint resistance. The pumping rate was determined by current amplitude and timing sequential control of heaters and the electromagnet. Operating characteristics were analyzed to enhance charging efficiency and the feasibility of temporally stable CC magnet during persistent mode was studied.