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Sample records for anisotropic magnetoresistive sensor

  1. Space magnetometer based on an anisotropic magnetoresistive hybrid sensor

    NASA Astrophysics Data System (ADS)

    Brown, P.; Whiteside, B. J.; Beek, T. J.; Fox, P.; Horbury, T. S.; Oddy, T. M.; Archer, M. O.; Eastwood, J. P.; Sanz-Hernández, D.; Sample, J. G.; Cupido, E.; O'Brien, H.; Carr, C. M.

    2014-12-01

    We report on the design and development of a low resource, dual sensor vector magnetometer for space science applications on very small spacecraft. It is based on a hybrid device combining an orthogonal triad of commercial anisotropic magnetoresistive (AMR) sensors with a totem pole H-Bridge drive on a ceramic substrate. The drive enables AMR operation in the more sensitive flipped mode and this is achieved without the need for current spike transmission down a sensor harness. The magnetometer has sensitivity of better than 3 nT in a 0-10 Hz band and a total mass of 104 g. Three instruments have been launched as part of the TRIO-CINEMA space weather mission, inter-calibration against the International Geomagnetic Reference Field model makes it possible to extract physical signals such as field-aligned current deflections of 20-60 nT within an approximately 45 000 nT ambient field.

  2. Space magnetometer based on an anisotropic magnetoresistive hybrid sensor.

    PubMed

    Brown, P; Whiteside, B J; Beek, T J; Fox, P; Horbury, T S; Oddy, T M; Archer, M O; Eastwood, J P; Sanz-Hernández, D; Sample, J G; Cupido, E; O'Brien, H; Carr, C M

    2014-12-01

    We report on the design and development of a low resource, dual sensor vector magnetometer for space science applications on very small spacecraft. It is based on a hybrid device combining an orthogonal triad of commercial anisotropic magnetoresistive (AMR) sensors with a totem pole H-Bridge drive on a ceramic substrate. The drive enables AMR operation in the more sensitive flipped mode and this is achieved without the need for current spike transmission down a sensor harness. The magnetometer has sensitivity of better than 3 nT in a 0-10 Hz band and a total mass of 104 g. Three instruments have been launched as part of the TRIO-CINEMA space weather mission, inter-calibration against the International Geomagnetic Reference Field model makes it possible to extract physical signals such as field-aligned current deflections of 20-60 nT within an approximately 45,000 nT ambient field. PMID:25554336

  3. Defect detection in aluminum laser welds using an anisotropic magnetoresistive sensor array

    SciTech Connect

    Allweins, K.; Kreutzbruck, M. von; Gierelt, G.

    2005-05-15

    For the detection of defects in aluminum laser welds an anisotropic magnetoresistive (AMR) sensor array was implemented in an eddy current testing system. The reliability of weld testing is strongly influenced by the texture of the laser weld whose field response significantly superimposes the defect's magnetic signature. A finite-element model was used to determine the influence of the weld's topology on the detection of defects such as porosities and inclusions hosted in the aluminum matrix. When using an AMR sensor array with field sensitivity of better than 1 nT/{radical}Hz defects with a radius smaller than 100 {mu}m could be detected and classified.

  4. Giant magnetoresistive sensor

    DOEpatents

    Stearns, Daniel G.; Vernon, Stephen P.; Ceglio, Natale M.; Hawryluk, Andrew M.

    1999-01-01

    A magnetoresistive sensor element with a three-dimensional micro-architecture is capable of significantly improved sensitivity and highly localized measurement of magnetic fields. The sensor is formed of a multilayer film of alternately magnetic and nonmagnetic materials. The sensor is optimally operated in a current perpendicular to plane mode. The sensor is useful in magnetic read/write heads, for high density magnetic information storage and retrieval.

  5. Recent Developments of Magnetoresistive Sensors for Industrial Applications

    PubMed Central

    Jogschies, Lisa; Klaas, Daniel; Kruppe, Rahel; Rittinger, Johannes; Taptimthong, Piriya; Wienecke, Anja; Rissing, Lutz; Wurz, Marc Christopher

    2015-01-01

    The research and development in the field of magnetoresistive sensors has played an important role in the last few decades. Here, the authors give an introduction to the fundamentals of the anisotropic magnetoresistive (AMR) and the giant magnetoresistive (GMR) effect as well as an overview of various types of sensors in industrial applications. In addition, the authors present their recent work in this field, ranging from sensor systems fabricated on traditional substrate materials like silicon (Si), over new fabrication techniques for magnetoresistive sensors on flexible substrates for special applications, e.g., a flexible write head for component integrated data storage, micro-stamping of sensors on arbitrary surfaces or three dimensional sensing under extreme conditions (restricted mounting space in motor air gap, high temperatures during geothermal drilling). PMID:26569263

  6. Recent Developments of Magnetoresistive Sensors for Industrial Applications.

    PubMed

    Jogschies, Lisa; Klaas, Daniel; Kruppe, Rahel; Rittinger, Johannes; Taptimthong, Piriya; Wienecke, Anja; Rissing, Lutz; Wurz, Marc Christopher

    2015-01-01

    The research and development in the field of magnetoresistive sensors has played an important role in the last few decades. Here, the authors give an introduction to the fundamentals of the anisotropic magnetoresistive (AMR) and the giant magnetoresistive (GMR) effect as well as an overview of various types of sensors in industrial applications. In addition, the authors present their recent work in this field, ranging from sensor systems fabricated on traditional substrate materials like silicon (Si), over new fabrication techniques for magnetoresistive sensors on flexible substrates for special applications, e.g., a flexible write head for component integrated data storage, micro-stamping of sensors on arbitrary surfaces or three dimensional sensing under extreme conditions (restricted mounting space in motor air gap, high temperatures during geothermal drilling). PMID:26569263

  7. Anisotropic magnetoresistance dominant in a three terminal Hanle measurement

    NASA Astrophysics Data System (ADS)

    Malec, Christopher; Miller, Michael M.; Johnson, Mark

    2016-02-01

    Experiments are performed on mesoscopic nonlocal lateral spin valves with aluminum channels and Permalloy electrodes. Four-terminal magnetoresistance and Hanle measurements characterize the spin accumulation with results that compare well with published work. Three-terminal Hanle measurements of the Permalloy/aluminum (Py/Al) interfaces show bell-shaped curves that can be fit to Lorentzians. These curves are three orders of magnitude larger than the spin accumulation. Using anisotropic magnetoresistance measurements of individual Permalloy electrodes, we demonstrate that the three-terminal measurements are dominated by anisotropic magnetoresistance effects unrelated to spin accumulation.

  8. Ballistic Anisotropic Magnetoresistance of Single-Atom Contacts.

    PubMed

    Schöneberg, J; Otte, F; Néel, N; Weismann, A; Mokrousov, Y; Kröger, J; Berndt, R; Heinze, S

    2016-02-10

    Anisotropic magnetoresistance, that is, the sensitivity of the electrical resistance of magnetic materials on the magnetization direction, is expected to be strongly enhanced in ballistic transport through nanoscale junctions. However, unambiguous experimental evidence of this effect is difficult to achieve. We utilize single-atom junctions to measure this ballistic anisotropic magnetoresistance (AMR). Single Co and Ir atoms are deposited on domains and domain walls of ferromagnetic Fe layers on W(110) to control their magnetization directions. They are contacted with nonmagnetic tips in a low-temperature scanning tunneling microscope to measure the junction conductances. Large changes of the magnetoresistance occur from the tunneling to the ballistic regime due to the competition of localized and delocalized d-orbitals, which are differently affected by spin-orbit coupling. This work shows that engineering the AMR at the single atom level is feasible. PMID:26783634

  9. Anisotropic giant magnetoresistance in NbSb₂

    DOE PAGESBeta

    Wang, Kefeng; Graf, D.; Li, Lijun; Wang, Limin; Petrovic, C.

    2014-12-05

    We report large transverse magnetoreistance (the magnetoresistant ratio ~ 1.3 × 10⁵% in 2 K and 9 T field, and 4.3 × 10⁶% in 0.4 K and 32 T field, without saturation) and field-induced metal semiconductor-like transition in NbSb₂. Magnetoresistance is significantly suppressed but the metal-semiconductor-like transition persists when the current is along the ac-plane. The sign reversal of the Hall resistivity and Seebeck coefficient in the field, plus the electronic structure reveal the coexistence of a small number of holes with very high mobility and a large number of electrons with low mobility. The large MR is attributed tomore » the change of the Fermi surface induced by the magnetic field in addition to the high mobility metal.« less

  10. Highly sensitive anisotropic magnetoresistance magnetometer for Eddy-current nondestructive evaluation.

    PubMed

    He, D F; Tachiki, M; Itozaki, H

    2009-03-01

    Using a commercially available anisotropic magnetoresistance (AMR) sensor of HMC1001, we developed a sensitive magnetometer. It could operate in amplifier mode or feedback mode. The magnetic field sensitivity of the AMR sensor was about 3.2 mV/V G. When the AMR sensor was biased by a voltage of 24 V, the magnetic field resolutions of the AMR magnetometer were about 12 pT/square root(Hz) at 1 kHz and 20 pT/square root(Hz) at 100 Hz. We used the AMR magnetometer for Eddy-current nondestructive evaluation in unshielded environment. PMID:19334957

  11. Anisotropic Magnetoresistance State Space of Permalloy Nanowires with Domain Wall Pinning Geometry

    PubMed Central

    Corte-León, Héctor; Nabaei, Vahid; Manzin, Alessandra; Fletcher, Jonathan; Krzysteczko, Patryk; Schumacher, Hans W.; Kazakova, Olga

    2014-01-01

    The domain wall-related change in the anisotropic magnetoresistance in L-shaped permalloy nanowires is measured as a function of the magnitude and orientation of the applied magnetic field. The magnetoresistance curves, compiled into so-called domain wall magnetoresistance state space maps, are used to identify highly reproducible transitions between domain states. Magnetic force microscopy and micromagnetic modelling are correlated with the transport measurements of the devices in order to identify different magnetization states. Analysis allows to determine the optimal working parameters for specific devices, such as the minimal field required to switch magnetization or the most appropriate angle for maximal separation of the pinning/depinning fields. Moreover, the complete state space maps can be used to predict evolution of nanodevices in magnetic field without a need of additional electrical measurements and for repayable initialization of magnetic sensors into a well-specified state. PMID:25116470

  12. Interfacial contribution to thickness dependent in-plane anisotropic magnetoresistance

    NASA Astrophysics Data System (ADS)

    Tokaç, M.; Wang, M.; Jaiswal, S.; Rushforth, A. W.; Gallagher, B. L.; Atkinson, D.; Hindmarch, A. T.

    2015-12-01

    We have studied in-plane anisotropic magnetoresistance (AMR) in cobalt films with overlayers having designed electrically interface transparency. With an electrically opaque cobalt/overlayer interface, the AMR ratio is shown to vary in inverse proportion to the cobalt film thickness; an indication that in-plane AMR is a consequence of anisotropic scattering with both volume and interfacial contributions. The interface scattering anisotropy opposes the volume scattering contribution, causing the AMR ratio to diminish as the cobalt film thickness is reduced. An intrinsic interface effect explains the significantly reduced AMR ratio in ultra-thin films.

  13. Anomalously large anisotropic magnetoresistance in a perovskite manganite

    PubMed Central

    Li, Run-Wei; Wang, Huabing; Wang, Xuewen; Yu, X. Z.; Matsui, Y.; Cheng, Zhao-Hua; Shen, Bao-Gen; Plummer, E. Ward; Zhang, Jiandi

    2009-01-01

    The signature of correlated electron materials (CEMs) is the coupling between spin, charge, orbital and lattice resulting in exotic functionality. This complexity is directly responsible for their tunability. We demonstrate here that the broken symmetry, through cubic to orthorhombic distortion in the lattice structure in a prototype manganite single crystal, La0.69Ca0.31MnO3, leads to an anisotropic magneto-elastic response to an external field, and consequently to remarkable magneto-transport behavior. An anomalous anisotropic magnetoresistance (AMR) effect occurs close to the metal-insulator transition (MIT) in the system, showing a direct correlation with the anisotropic field-tuned MIT in the system and can be understood by means of a simple phenomenological model. A small crystalline anisotropy stimulates a “colossal” AMR near the MIT phase boundary of the system, thus revealing the intimate interplay between magneto- and electronic-crystalline couplings. PMID:19706504

  14. Insensitivity of tunneling anisotropic magnetoresistance to non-magnetic electrodes

    SciTech Connect

    Wang, Y. Y.; Song, C. Wang, G. Y.; Zeng, F.; Pan, F.

    2013-11-11

    Ferromagnetic electrodes play a crucial role in magnetoresistance effect and spin injection, whereas the essential features of non-magnetic metal electrodes in spintronics are commonly ignored except for their electrical conductivity. Here, we verify that the room-temperature tunneling anisotropic magnetoresistance (TAMR) behavior in antiferromagnet-based [Pt/Co]/IrMn/AlO{sub x}/metal (metal = Pt, Au, Cu, Al) junctions is insensitive to the top metal electrodes. Similar out-of-plane signals are detected for different electrodes, in contrast to the varied shapes of in-plane TAMR curves which are most likely attributed to the differences in the multidomain structure of the magnetic electrode. This would add a different dimension to spintronics.

  15. Angular dependence of anisotropic magnetoresistance in magnetic systems

    SciTech Connect

    Zhang, Steven S.-L. Zhang, Shufeng

    2014-05-07

    Anisotropic magnetoresistance (AMR), whose physical origin is attributed to the combination of spin dependent scattering and spin orbital coupling (SOC), usually displays simple angular dependence for polycrystalline ferromagnetic metals. By including generic spin dependent scattering and spin Hall (SH) terms in the Ohm's law, we explicitly show that various magneto-transport phenomena such as anomalous Hall (AH), SH, planar Hall (PH) and AMR could be quantitatively related for bulk polycrystalline ferromagnetic metals. We also discuss how AMR angular dependence is affected by the presence of interfacial SOC in magnetic layered structure.

  16. Gamma Irradiation of Magnetoresistive Sensors for Planetary Exploration

    PubMed Central

    Sanz, Ruy; Fernández, Ana B.; Dominguez, Jose A.; Martín, Boris; Michelena, Marina D.

    2012-01-01

    A limited number of Anisotropic Magnetoresistive (AMR) commercial-off-the-shelf (COTS) magnetic sensors of the HMC series by Honeywell, with and without integrated front-end electronics, were irradiated with gamma rays up to a total irradiation dose of 200 krad (Si), following the ESCC Basic Specification No. 22900. Due to the magnetic cleanliness required for these tests a special set-up was designed and successfully employed. Several parameters of the sensors were monitored during testing and the results are reported in this paper. The authors conclude that AMR sensors without front-end electronics seem to be robust against radiation doses of up to 200 krad (Si) with a dose rate of 5 krad (Si)/hour and up to a resolution of tens of nT, but sensors with an integrated front-end seem to be more vulnerable to radiation. PMID:22666039

  17. Anisotropic magnetoresistivity in structured elastomer composites: modelling and experiments.

    PubMed

    Mietta, José Luis; Tamborenea, Pablo I; Martin Negri, R

    2016-08-14

    A constitutive model for the anisotropic magnetoresistivity in structured elastomer composites (SECs) is proposed. The SECs considered here are oriented pseudo-chains of conductive-magnetic inorganic materials inside an elastomer organic matrix. The pseudo-chains are formed by fillers which are simultaneously conductive and magnetic dispersed in the polymer before curing or solvent evaporation. The SEC is then prepared in the presence of a uniform magnetic field, referred to as Hcuring. This procedure generates the pseudo-chains, which are preferentially aligned in the direction of Hcuring. Electrical conduction is present in that direction only. The constitutive model for the magnetoresistance considers the magnetic pressure, Pmag, induced on the pseudo-chains by an external magnetic field, H, applied in the direction of the pseudo-chains. The relative changes in conductivity as a function of H are calculated by evaluating the relative increase of the electron tunnelling probability with Pmag, a magneto-elastic coupling which produces an increase of conductivity with magnetization. The model is used to adjust experimental results of magnetoresistance in a specific SEC where the polymer is polydimethylsiloxane, PDMS, and fillers are microparticles of magnetite-silver (referred to as Fe3O4[Ag]). Simulations of the expected response for other materials in both superparamagnetic and blocked magnetic states are presented, showing the influence of the Young's modulus of the matrix and filler's saturation magnetization. PMID:27418417

  18. Influence of local anisotropic magnetoresistance on the total magnetoresistance of mesoscopic NiFe rings

    NASA Astrophysics Data System (ADS)

    Buntinx, Dieter; Volodin, Alexander; van Haesendonck, Chris

    2004-12-01

    The magnetoresistance of mesoscopic NiFe rings is studied by low temperature magnetotransport measurements and numerical simulations. In order not to disturb the magnetic states in the electrical transport measurements, nonmagnetic gold wires are attached to individual rings. The simulations compute the change in resistance that is caused by the anisotropic magnetoresistance (AMR) effect and are based on a combination of magnetostatics for the magnetic domain configuration and electrostatics for the current distribution. Measurements as well as simulations reveal the presence of two stable “onion” states at remanence and a stable “vortex” state near the switching fields. Moreover, a quantitative comparison between experiment and simulation is possible without the use of any free fitting parameters. Apart from the AMR effect, no additional domain wall resistance has to be introduced for the onion state. In the switching region, experiment and simulation reveal the presence of a “stressed vortex” configuration which plays a key role in the quantitative description of the magnetoresistance. The switching behavior of the NiFe rings can be modified by introducing a wedge shaped notch at the expected position of one of the domain walls in the onion state of the rings.

  19. Giant Magnetoresistive Sensors for DNA Microarray

    PubMed Central

    Xu, Liang; Yu, Heng; Han, Shu-Jen; Osterfeld, Sebastian; White, Robert L.; Pourmand, Nader; Wang, Shan X.

    2009-01-01

    Giant magnetoresistive (GMR) sensors are developed for a DNA microarray. Compared with the conventional fluorescent sensors, GMR sensors are cheaper, more sensitive, can generate fully electronic signals, and can be easily integrated with electronics and microfluidics. The GMR sensor used in this work has a bottom spin valve structure with an MR ratio of 12%. The single-strand target DNA detected has a length of 20 bases. Assays with DNA concentrations down to 10 pM were performed, with a dynamic range of 3 logs. A double modulation technique was used in signal detection to reduce the 1/f noise in the sensor while circumventing electromagnetic interference. The logarithmic relationship between the magnetic signal and the target DNA concentration can be described by the Temkin isotherm. Furthermore, GMR sensors integrated with microfluidics has great potential of improving the sensitivity to 1 pM or below, and the total assay time can be reduced to less than 1 hour. PMID:20824116

  20. 360 degree domain walls monitored by anisotropic magnetoresistance measurements

    NASA Astrophysics Data System (ADS)

    Nam, Chunghee; Ross, C. A.

    2013-03-01

    This study investigates the electrical observation of the formation of a 360° magnetic domain wall (360DW) in an elliptical Co ring structure. Because the 360DW consists of two 180° domain walls, a decrease in resistance is observed in the switching process due to anisotropic magnetoresistance (AMR). Certain AMR measurements exhibit an increase in the resistance in the switching process, indicating that a flux-closure vortex state is formed without first forming a 360DW state. The difference between the 360DW and vortex state in the switching process reflects differences in the DW depinning mechanism from the onion state. The minor loop of the AMR measurements is also dependent on the initial magnetic configuration between the 360DW and the vortex state.

  1. Interlayer transverse magnetoresistance in the presence of an anisotropic pseudogap

    NASA Astrophysics Data System (ADS)

    Smith, M. F.; McKenzie, Ross H.

    2009-12-01

    The interlayer magnetoresistance of a quasi-two-dimensional layered metal with a d -wave pseudogap is calculated semiclassically. An expression for the interlayer resistivity as a function of the strength and direction of the magnetic field, the magnitude of the pseudogap, temperature, and scattering rate is obtained. We find that the pseudogap, by introducing low-energy nodal quasiparticle contours, smooths the dependence on field direction in a manner characteristic of its anisotropy. We thus propose that interlayer resistance measurements under a strong field of variable orientation can be used to fully characterize an anisotropic pseudogap. The general result is applied to the case of a magnetic field parallel to the conducting layers using a model band structure appropriate for overdoped Tℓ2201 .

  2. Linearization strategies for high sensitivity magnetoresistive sensors

    NASA Astrophysics Data System (ADS)

    Silva, Ana V.; Leitao, Diana C.; Valadeiro, João; Amaral, José; Freitas, Paulo P.; Cardoso, Susana

    2015-10-01

    Ultrasensitive magnetic field sensors envisaged for applications on biomedical imaging require the detection of low-intensity and low-frequency signals. Therefore linear magnetic sensors with enhanced sensitivity low noise levels and improved field detection at low operating frequencies are necessary. Suitable devices can be designed using magnetoresistive sensors, with room temperature operation, adjustable detected field range, CMOS compatibility and cost-effective production. The advent of spintronics set the path to the technological revolution boosted by the storage industry, in particular by the development of read heads using magnetoresistive devices. New multilayered structures were engineered to yield devices with linear output. We present a detailed study of the key factors influencing MR sensor performance (materials, geometries and layout strategies) with focus on different linearization strategies available. Furthermore strategies to improve sensor detection levels are also addressed with best reported values of ˜40 pT/√Hz at 30 Hz, representing a step forward the low field detection at room temperature.

  3. Magnetocardiography with sensors based on giant magnetoresistance

    NASA Astrophysics Data System (ADS)

    Pannetier-Lecoeur, M.; Parkkonen, L.; Sergeeva-Chollet, N.; Polovy, H.; Fermon, C.; Fowley, C.

    2011-04-01

    Biomagnetic signals, mostly due to the electrical activity in the body, are very weak and they can only be detected by the most sensitive magnetometers, such as Superconducting Quantum Interference Devices (SQUIDs). We report here biomagnetic recordings with hybrid sensors based on Giant MagnetoResistance (GMR). We recorded magnetic signatures of the electric activity of the human heart (magnetocardiography) in healthy volunteers. The P-wave and QRS complex, known from the corresponding electric recordings, are clearly visible in the recordings after an averaging time of about 1 min. Multiple recordings at different locations over the chest yielded a dipolar magnetic field map and allowed localizing the underlying current sources. The sensitivity of the GMR-based sensors is now approaching that of SQUIDs and paves way for spin electronics devices for functional imaging of the body.

  4. Theoretical Study on Twofold and Fourfold Symmetric Anisotropic Magnetoresistance Effect

    NASA Astrophysics Data System (ADS)

    Kokado, Satoshi; Tsunoda, Masakiyo

    We theoretically study the twofold and fourfold symmetric anisotropic magnetoresistance (AMR) effect [ 1 ] . We first extend our previous model [ 2 ] to a model including the crystal field effect [ 1 ] . Using the model, we next obtain an analytical expression of the AMR ratio, i.e., AMR (ϕ) =C0 +C2 cos (2 ϕ) +C4 cos (4 ϕ) , with C0=C2 -C4 [ 1 ] . Here, ϕ is the relative angle between the magnetization direction and the electric current direction and C2 (C4) is a coefficient of the twofold (fourfold) symmetric term. The coefficients C2 and C4 are expressed by a spin-orbit coupling constant, an exchange field, a crystal field, and s-s and s-d scattering resistivities. Using this expression, we analyze the experimental results for Fe4N [ 3 ] , in which | C2 | and | C4 | increase with decreasing temperature. The experimental results can be reproduced by assuming that the tetragonal distortion increases with decreasing temperature. [ 1 ] S. Kokado et al., J. Phys. Soc. Jpn. 84 (2015) 094710. [ 2 ] S. Kokado et al., J. Phys. Soc. Jpn. 81 (2012) 024705. [ 3 ] M. Tsunoda et al., Appl. Phys. Express 3 (2010) 113003.

  5. Giant single-molecule anisotropic magnetoresistance at room temperature.

    PubMed

    Li, Ji-Jun; Bai, Mei-Lin; Chen, Zhao-Bin; Zhou, Xiao-Shun; Shi, Zhan; Zhang, Meng; Ding, Song-Yuan; Hou, Shi-Min; Schwarzacher, Walther; Nichols, Richard J; Mao, Bing-Wei

    2015-05-13

    We report an electrochemically assisted jump-to-contact scanning tunneling microscopy (STM) break junction approach to create reproducible and well-defined single-molecule spintronic junctions. The STM break junction is equipped with an external magnetic field either parallel or perpendicular to the electron transport direction. The conductance of Fe-terephthalic acid (TPA)-Fe single-molecule junctions is measured and a giant single-molecule tunneling anisotropic magnetoresistance (T-AMR) up to 53% is observed at room temperature. Theoretical calculations based on first-principles quantum simulations show that the observed AMR of Fe-TPA-Fe junctions originates from electronic coupling at the TPA-Fe interfaces modified by the magnetic orientation of the Fe electrodes with respect to the direction of current flow. The present study highlights new opportunities for obtaining detailed understanding of mechanisms of charge and spin transport in molecular junctions and the role of interfaces in determining the MR of single-molecule junctions. PMID:25894840

  6. Gilbert damping and anisotropic magnetoresistance in iron-based alloys

    NASA Astrophysics Data System (ADS)

    Berger, L.

    2016-07-01

    We use the two-current model of Campbell and Fert to understand the compositional dependence of the Gilbert damping parameter in certain iron alloys. In that model, spin-up and spin-down carriers have different resistivities ρ↑ and ρ↓. We emphasize the part of the Gilbert parameter, called Gsf, generated by spin-flip interband processes. Both Gsf and the anisotropic magnetoresistance Δρ are proportional to the square of the spin-orbit parameter, and also proportional to ρ↑. In bcc alloys of iron with V, Cr, Mo, etc. solutes on the left of iron in the periodic table, ρ↑ is increased by a scattering resonance (Gomes and Campbell, 1966, 1968). Then ρ↑, Δρ, and Gsf all exhibit a peak at the same moderate concentration of the solute. We find the best fit between this theory and existing experimental data of Gilbert damping for Fe-V epitaxial films at room temperature (Cheng, 2006; Scheck et al., 2007). At room temperature, the predicted Gsf peak is masked by a background arising from non-flip intraband processes. At elevated temperatures, the peak is expected to become more prominent, and less hidden in the background.

  7. Linear field amplification for magnetoresistive sensors

    NASA Astrophysics Data System (ADS)

    Trindade, I. G.; Fermento, R.; Sousa, J. B.; Chaves, R. C.; Cardoso, S.; Freitas, P. P.

    2008-05-01

    In this article, we describe the fabrication and characterization of a spin valve (SV) magnetoresistive (MR) sensor, located in the gap of two magnetically soft flux guides (FGs) that enhance the sensor magnetic field sensitivity, while keeping in the sensor a quasilinear Barkhausen-noise-free response. Top pinned SV sensors were fabricated into stripes, having lengths of 100μm and widths of 2 and 3μm, by optical lithography and ion-milling etching. The FGs consisted of poles and yokes of an amorphous alloy of Co88.4Zr3.3Nb8.3, prepared by physical vapor deposition and were lithographically defined by a lift-off process. The SV sensor MR responses to applied uniform magnetic fields Ha, when either isolated or located in the gap of two types of FGs, were characterized in terms of the saturation field, coercive force, and sensitivity. The impact of the FG geometry in the magnetic field amplification and sensor response characteristics were studied. Magnetic force microscopy analysis was performed to identify the presence of multidomain states in the FGs and of a remanent field in their gap. SV sensors in the gap of FGs using long poles and having a sensing area of 1000μm2 exhibit a linear sensitivity of 50mV/Oe in the field range of a couple of oersteds. The SV sensor in the gap of magnetically soft FGs exhibits enhanced hysteresis, characterized by a coercive force of approximately 1Oe. Two schemes are proposed to reduce the hysteresis in the sensor response.

  8. Temperature-Dependent Asymmetry of Anisotropic Magnetoresistance in Silicon p-n Junctions

    PubMed Central

    Yang, D. Z.; Wang, T.; Sui, W. B.; Si, M. S.; Guo, D. W.; Shi, Z.; Wang, F. C.; Xue, D. S.

    2015-01-01

    We report a large but asymmetric magnetoresistance in silicon p-n junctions, which contrasts with the fact of magnetoresistance being symmetric in magnetic metals and semiconductors. With temperature decreasing from 293 K to 100 K, the magnetoresistance sharply increases from 50% to 150% under a magnetic field of 2 T. At the same time, an asymmetric magnetoresistance, which manifests itself as a magnetoresistance voltage offset with respect to the sign of magnetic field, occurs and linearly increases with magnetoresistance. More interestingly, in contrast with other materials, the lineshape of anisotropic magnetoresistance in silicon p-n junctions significantly depends on temperature. As temperature decreases from 293 K to 100 K, the width of peak shrinks from 90° to 70°. We ascribe these novel magnetoresistance to the asymmetric geometry of the space charge region in p-n junction induced by the magnetic field. In the vicinity of the space charge region the current paths are deflected, contributing the Hall field to the asymmetric magnetoresistance. Therefore, the observed temperature-dependent asymmetry of magnetoresistance is proved to be a direct consequence of the spatial configuration evolution of space charge region with temperature. PMID:26323495

  9. Temperature-Dependent Asymmetry of Anisotropic Magnetoresistance in Silicon p-n Junctions.

    PubMed

    Yang, D Z; Wang, T; Sui, W B; Si, M S; Guo, D W; Shi, Z; Wang, F C; Xue, D S

    2015-01-01

    We report a large but asymmetric magnetoresistance in silicon p-n junctions, which contrasts with the fact of magnetoresistance being symmetric in magnetic metals and semiconductors. With temperature decreasing from 293 K to 100 K, the magnetoresistance sharply increases from 50% to 150% under a magnetic field of 2 T. At the same time, an asymmetric magnetoresistance, which manifests itself as a magnetoresistance voltage offset with respect to the sign of magnetic field, occurs and linearly increases with magnetoresistance. More interestingly, in contrast with other materials, the lineshape of anisotropic magnetoresistance in silicon p-n junctions significantly depends on temperature. As temperature decreases from 293 K to 100 K, the width of peak shrinks from 90° to 70°. We ascribe these novel magnetoresistance to the asymmetric geometry of the space charge region in p-n junction induced by the magnetic field. In the vicinity of the space charge region the current paths are deflected, contributing the Hall field to the asymmetric magnetoresistance. Therefore, the observed temperature-dependent asymmetry of magnetoresistance is proved to be a direct consequence of the spatial configuration evolution of space charge region with temperature. PMID:26323495

  10. Fractional modeling of the AC large-signal frequency response in magnetoresistive current sensors.

    PubMed

    Ravelo Arias, Sergio Iván; Ramírez Muñoz, Diego; Moreno, Jaime Sánchez; Cardoso, Susana; Ferreira, Ricardo; de Freitas, Paulo Jorge Peixeiro

    2013-01-01

    Fractional calculus is considered when derivatives and integrals of non-integer order are applied over a specific function. In the electrical and electronic domain, the transfer function dependence of a fractional filter not only by the filter order n, but additionally, of the fractional order α is an example of a great number of systems where its input-output behavior could be more exactly modeled by a fractional behavior. Following this aim, the present work shows the experimental ac large-signal frequency response of a family of electrical current sensors based in different spintronic conduction mechanisms. Using an ac characterization set-up the sensor transimpedance function Z(t)(JF) is obtained considering it as the relationship between sensor output voltage and input sensing current, Z(t)(jf)= V(o, sensor)(jf)/I(sensor)(jf). The study has been extended to various magnetoresistance sensors based in different technologies like anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), spin-valve (GMR-SV) and tunnel magnetoresistance (TMR). The resulting modeling shows two predominant behaviors, the low-pass and the inverse low-pass with fractional index different from the classical integer response. The TMR technology with internal magnetization offers the best dynamic and sensitivity properties opening the way to develop actual industrial applications. PMID:24351648

  11. Tunneling Anisotropic Magnetoresistance with Half-Metallic Electrodes

    NASA Astrophysics Data System (ADS)

    Burton, J. D.; Tsymbal, Evgeny Y.

    2015-03-01

    Tunneling anisotropic magnetoresistance (TAMR) is the difference in resistance of a magnetic tunnel junction due to a change in direction of the magnetization of one or both of the magnetic electrodes with respect to the flow of current, i.e. tunnel conductance for magnetization in the plane differs from magnetization out of the plane. The origin of the effect is spin-orbit coupling (SOC). We will present results of first-principles density functional calculations of the TAMR effect in a half-metallic material, i.e. a metal that has free carriers only in one spin channel. In particular we explore the TAMR effect in magnetic tunnel junctions with La0.7Sr0.3MnO3 (LSMO) electrodes and a SrTiO3 (STO) tunneling barrier. We find ~ 500% difference in resistance between magnetization in the plane and out of the plane. This large TAMR effect originates from the half-metallic nature of LSMO: when magnetization is out-of-plane SOC contributions to the transmission comes only from spin-flip scattering, which is still inherently small due to the half-metallicity. For in-plane magnetization, however, there is a large non-spin-flip SOC contribution to the conductance. The spin-flip vs. non-spin-flip dichotomy along with the orbital character of the states on the Fermi surface of LSMO leads to the large TAMR effect. This effect should be a general feature of half-metallic or highly spin-polarized magnetic electrodes and could open the door to enhanced spintronic device functionalities.

  12. Electric field modulation of tunneling anisotropic magnetoresistance in tunnel junctions with antiferromagnetic electrodes

    NASA Astrophysics Data System (ADS)

    Goto, Minori; Nawaoka, Kohei; Miwa, Shinji; Hatanaka, Shohei; Mizuochi, Norikazu; Suzuki, Yoshishige

    2016-08-01

    We present electric field modulation of tunneling anisotropic magnetoresistance (TAMR) in MnIr|MgO|Ta tunnel junctions. TAMR enables direct observation of the antiferromagnetic spin direction at the MnIr|MgO interface. We found that the shape of magnetoresistance (MR) curve can be modulated by an electric field, which can be explained by electric field modulation of the interfacial magnetic anisotropy at MnIr|MgO.

  13. Fractional Modeling of the AC Large-Signal Frequency Response in Magnetoresistive Current Sensors

    PubMed Central

    Arias, Sergio Iván Ravello; Muñoz, Diego Ramírez; Moreno, Jaime Sánchez; Cardoso, Susana; Ferreira, Ricardo; de Freitas, Paulo Jorge Peixeiro

    2013-01-01

    Fractional calculus is considered when derivatives and integrals of non-integer order are applied over a specific function. In the electrical and electronic domain, the transfer function dependence of a fractional filter not only by the filter order n, but additionally, of the fractional order α is an example of a great number of systems where its input-output behavior could be more exactly modeled by a fractional behavior. Following this aim, the present work shows the experimental ac large-signal frequency response of a family of electrical current sensors based in different spintronic conduction mechanisms. Using an ac characterization set-up the sensor transimpedance function Zt(if) is obtained considering it as the relationship between sensor output voltage and input sensing current, Zt(jf)=Vo,sensor(jf)/Isensor(jf). The study has been extended to various magnetoresistance sensors based in different technologies like anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), spin-valve (GMR-SV) and tunnel magnetoresistance (TMR). The resulting modeling shows two predominant behaviors, the low-pass and the inverse low-pass with fractional index different from the classical integer response. The TMR technology with internal magnetization offers the best dynamic and sensitivity properties opening the way to develop actual industrial applications. PMID:24351648

  14. Lateral flow immunoassay using magnetoresistive sensors

    NASA Astrophysics Data System (ADS)

    Taton, Kristin; Johnson, Diane; Guire, Patrick; Lange, Erik; Tondra, Mark

    2009-05-01

    Magnetic particles have been adapted for use as labels in biochemical lateral flow strip tests. Standard gold particle lateral flow assays are generally qualitative; however, with magnetic particles, quantitative results can be obtained by using electronic detection systems with giant magnetoresistive (GMR) sensors. As described here, these small integrated sensor chips can detect the presence of magnetic labels in capture spots whose volume is approximately 150 μm×150 μm×150 μm. The range of linear detection is better than two orders of magnitude; the total range is up to four orders of magnitude. The system was demonstrated with both indirect and sandwich enzyme-linked immunosorbent assays (ELISAs) for protein detection of rabbit IgG and interferon-γ, respectively, achieving detection of 12 pg/ml protein. Ultimately, the goal is for the detector to be fully integrated into the lateral flow strip backing to form a single consumable item that is interrogated by a handheld electronic reader.

  15. The MAGIC of CINEMA: first in-flight science results from a miniaturised anisotropic magnetoresistive magnetometer

    NASA Astrophysics Data System (ADS)

    Archer, M. O.; Horbury, T. S.; Brown, P.; Eastwood, J. P.; Oddy, T. M.; Whiteside, B. J.; Sample, J. G.

    2015-06-01

    We present the first in-flight results from a novel miniaturised anisotropic magnetoresistive space magnetometer, MAGIC (MAGnetometer from Imperial College), aboard the first CINEMA (CubeSat for Ions, Neutrals, Electrons and MAgnetic fields) spacecraft in low Earth orbit. An attitude-independent calibration technique is detailed using the International Geomagnetic Reference Field (IGRF), which is temperature dependent in the case of the outboard sensor. We show that the sensors accurately measure the expected absolute field to within 2% in attitude mode and 1% in science mode. Using a simple method we are able to estimate the spacecraft's attitude using the magnetometer only, thus characterising CINEMA's spin, precession and nutation. Finally, we show that the outboard sensor is capable of detecting transient physical signals with amplitudes of ~ 20-60 nT. These include field-aligned currents at the auroral oval, qualitatively similar to previous observations, which agree in location with measurements from the DMSP (Defense Meteorological Satellite Program) and POES (Polar-orbiting Operational Environmental Satellites) spacecraft. Thus, we demonstrate and discuss the potential science capabilities of the MAGIC instrument onboard a CubeSat platform.

  16. Giant Magnetoresistive (GMR) Sensor Microelectromechanical System (MEMS) Device

    NASA Technical Reports Server (NTRS)

    Ramesham, R.

    1999-01-01

    The measurement of acceleration has been accomplished using several technologies in high-reliability applications such as guidance control, detonation, and shock/vibration measurement. Electromechanical, piezoelectric, piezoresistive, and capacitive acceleration sensors are available and the literature pertinent to giant magnetoresistive sensors (GMR) for the above applications are scanty.

  17. Extremely large and significantly anisotropic magnetoresistance in ZrSiS single crystals

    NASA Astrophysics Data System (ADS)

    Lv, Yang-Yang; Zhang, Bin-Bin; Li, Xiao; Yao, Shu-Hua; Chen, Y. B.; Zhou, Jian; Zhang, Shan-Tao; Lu, Ming-Hui; Chen, Yan-Feng

    2016-06-01

    Recently, the extremely large magnetoresistance (MR) observed in transition metal telluride, like WTe2, attracted much attention because of the potential applications in magnetic sensor. Here, we report the observation of extremely large magnetoresistance as 3.0 × 104% measured at 2 K and 9 T magnetic field aligned along [001]-ZrSiS. The significant magnetoresistance change (˜1.4 × 104%) can be obtained when the magnetic field is titled from [001] to [011]-ZrSiS. These abnormal magnetoresistance behaviors in ZrSiS can be understood by electron-hole compensation and the open orbital of Fermi surface. Because of these superior MR properties, ZrSiS may be used in the magnetic sensors.

  18. Tuning magnetic nanostructures and flux concentrators for magnetoresistive sensors

    NASA Astrophysics Data System (ADS)

    Yin, Xiaolu; Liu, Yen-Fu; Ewing, Dan; Ruder, Carmen K.; De Rego, Paul J.; Edelstein, A. S.; Liou, Sy-Hwang

    2015-09-01

    The methods for the optimization of the magnetoresistive (MR) sensors are to reduce sources of noises, to increase the signal, and to understand the involved fundamental limitations. The high-performance MR sensors result from important magnetic tunnel junction (MTJ) properties, such as tunneling magnetoresistance ratio (TMR), coercivity (Hc), exchange coupling field (He), domain structures, and noise properties as well as the external magnetic flux concentrators. All these parameters are sensitively controlled by the magnetic nanostructures, which can be tuned by varying junction free layer nanostructures, geometry, and magnetic annealing process etc. In this paper, we discuss some of efforts that an optimized magnetic sensor with a sensitivity as high as 5,146 %/mT. This sensitivity is currently the highest among all MR-type sensors that have been reported. The estimated noise of our magnetoresistive sensor is 47 pT/Hz1/2 at 1 Hz. This magnetoresistance sensor dissipates only 100 μW of power while operating under an applied voltage of 1 V at room temperature.

  19. Detection of magnetic resonance signals using a magnetoresistive sensor

    DOEpatents

    Budker, Dmitry; Pines, Alexander; Xu, Shoujun; Hilty, Christian; Ledbetter, Micah P; Bouchard, Louis S

    2013-10-01

    A method and apparatus are described wherein a micro sample of a fluidic material may be assayed without sample contamination using NMR techniques, in combination with magnetoresistive sensors. The fluidic material to be assayed is first subject to pre-polarization, in one embodiment, by passage through a magnetic field. The magnetization of the fluidic material is then subject to an encoding process, in one embodiment an rf-induced inversion by passage through an adiabatic fast-passage module. Thereafter, the changes in magnetization are detected by a pair of solid-state magnetoresistive sensors arranged in gradiometer mode. Miniaturization is afforded by the close spacing of the various modules.

  20. Anisotropic giant magnetoresistance in NbSb2

    PubMed Central

    Wang, Kefeng; Graf, D.; Li, Lijun; Wang, Limin; Petrovic, C.

    2014-01-01

    The magnetic field response of the transport properties of novel materials and then the large magnetoresistance effects are of broad importance in both science and application. We report large transverse magnetoreistance (the magnetoresistant ratio ~ 1.3 × 105% in 2 K and 9 T field, and 4.3 × 106% in 0.4 K and 32 T field, without saturation) and field-induced metal-semiconductor-like transition, in NbSb2 single crystal. Magnetoresistance is significantly suppressed but the metal-semiconductor-like transition persists when the current is along the ac-plane. The sign reversal of the Hall resistivity and Seebeck coefficient in the field, plus the electronic structure reveal the coexistence of a small number of holes with very high mobility and a large number of electrons with low mobility. The large MR is attributed to the change of the Fermi surface induced by the magnetic field which is related to the Dirac-like point, in addition to orbital MR expected for high mobility metals. PMID:25476239

  1. Tunnel anisotropic magnetoresistance in CoFeB|MgO|Ta junctions

    SciTech Connect

    Hatanaka, S.; Miwa, S. Matsuda, K.; Nawaoka, K.; Tanaka, K.; Morishita, H.; Goto, M.; Mizuochi, N.; Shinjo, T.; Suzuki, Y.

    2015-08-24

    We found that CoFeB|MgO|Ta tunnel junctions exhibit tunnel anisotropic magnetoresistance (TAMR) at room temperature. The tunnel junctions exhibit positive magnetoresistance with the application of a magnetic field normal to the film plane. The dependencies on the applied magnetic field angle and MgO thickness reveal that the magnetoresistance originates from the TAMR, caused by the spin polarization and the spin-orbit interaction at the CoFeB|MgO interface. We also found that the TAMR can be used to detect ferromagnetic resonance in the CoFeB. This detection method could be useful for the characterization of nanomagnets that are free from the spin-transfer effect and the stray field of a reference layer, unlike conventional magnetic tunnel junctions.

  2. Biasing materials for anisotropic magnetoresistive and spin-valve read heads

    NASA Astrophysics Data System (ADS)

    Devasahayam, Adrian Joshua

    As recording densities rapidly rise, traditional inductive heads are no longer suited for read-back of data due to their lower signal levels and lower sensitivities. Dedicated heads, optimized for read-back, using the anisotropic magnetoresistive (AMR) and giant magnetoresistive (GMR) effects are more attractive. The output signal from devices based on both of these phenomena is, however, susceptible to noise arising from domain wall motion in the sensor element. One of the more common methods of suppressing this `Barkhausen noise' employs the exchange coupling between antiferromagnetic and ferromagnetic layers to ensure that the ferromagnetic sensor is in a single domain state. Another popular method uses the magnetostatic fields from permanent magnets to saturate the sensor. An additional, and increasingly important, application for exchange biasing materials is for pinning one of the ferromagnetic layers in a spin-valve type of sensor. FeMn has traditionally filled the role of exchange biasing material, but due to its poor corrosion resistance and poor thermal stability, it is proving inadequate. Thus, there is great interest in the storage industry for a suitable replacement. In this thesis, the performance of CoNiO, NiO, NiMn and IrMn as exchange biasing materials and CoCrPt as a permanent magnet has been evaluated. The significant material properties investigated were biasing fields, thermal stability, thickness effects and corrosion resistance. The oxide materials had excellent corrosion resistance, but NiO had poor exchange fields and CoNiO had a poor blocking temperature. NiMn had the best exchange field with an interfacial exchange coupling of 0.25 erg/cm2, but it required high temperature annealing in order to realize this. It also had good thermal and corrosion resistance properties. IrMn was found to have a good combination of these properties, the weakest being its corrosion resistance, which was nevertheless better than FeMn. Spin-valves fabricated

  3. A Magnetoresistive Tactile Sensor for Harsh Environment Applications.

    PubMed

    Alfadhel, Ahmed; Khan, Mohammed Asadullah; Cardoso, Susana; Leitao, Diana; Kosel, Jürgen

    2016-01-01

    A magnetoresistive tactile sensor is reported, which is capable of working in high temperatures up to 140 °C. Hair-like bioinspired structures, known as cilia, made out of permanent magnetic nanocomposite material on top of spin-valve giant magnetoresistive (GMR) sensors are used for tactile sensing at high temperatures. The magnetic nanocomposite, consisting of iron nanowires incorporated into the polymer polydimethylsiloxane (PDMS), is very flexible, biocompatible, has high remanence, and is also resilient to antagonistic sensing ambient. When the cilia come in contact with a surface, they deflect in compliance with the surface topology. This yields a change of the GMR sensor signal, enabling the detection of extremely fine features. The spin-valve is covered with a passivation layer, which enables adequate performance in spite of harsh environmental conditions, as demonstrated in this paper for high temperature. PMID:27164113

  4. A Magnetoresistive Tactile Sensor for Harsh Environment Applications

    PubMed Central

    Alfadhel, Ahmed; Khan, Mohammed Asadullah; Cardoso, Susana; Leitao, Diana; Kosel, Jürgen

    2016-01-01

    A magnetoresistive tactile sensor is reported, which is capable of working in high temperatures up to 140 °C. Hair-like bioinspired structures, known as cilia, made out of permanent magnetic nanocomposite material on top of spin-valve giant magnetoresistive (GMR) sensors are used for tactile sensing at high temperatures. The magnetic nanocomposite, consisting of iron nanowires incorporated into the polymer polydimethylsiloxane (PDMS), is very flexible, biocompatible, has high remanence, and is also resilient to antagonistic sensing ambient. When the cilia come in contact with a surface, they deflect in compliance with the surface topology. This yields a change of the GMR sensor signal, enabling the detection of extremely fine features. The spin-valve is covered with a passivation layer, which enables adequate performance in spite of harsh environmental conditions, as demonstrated in this paper for high temperature. PMID:27164113

  5. Anisotropic properties of molecular beam epitaxy-grown colossal magnetoresistance manganite thin films

    SciTech Connect

    ODonnell, J.; Onellion, M.; Rzchowski, M.S.; Eckstein, J.N.; Bozovic, I.

    1997-04-01

    We show that both the magnetoresistance and magnetism in tetragonal MBE-grown films of La{sub 1{minus}x}Ca{sub x}MnO{sub 3} show anisotropic effects that depend on both temperature and magnetic field. We show that the {open_quotes}colossal{close_quotes} magnetoresistance depends on the angle between the magnetization and the transport current and that the size of this effect is temperature-dependent. Below the Curie temperature this results in an unusual upturn in the magnetoresistance for small magnetic fields normal to the plane of the film as the magnetization rotates out of the plane. Low-field hysteresis of the in-plane magnetoresistance is also observed, and also shows an anisotropy with respect to the current and magnetization directions. We also find an in-plane biaxial magnetocrystalline anisotropy with easy axes along the {l_brace}100{r_brace} (Mn{endash}O) crystal directions, and evidence for {ital c}-axis magnetocrystalline anisotropy. {copyright} {ital 1997 American Institute of Physics.}

  6. Voltage-controlled oxide barriers in organic/hybrid spin valves based on tunneling anisotropic magnetoresistance

    NASA Astrophysics Data System (ADS)

    Grünewald, M.; Homonnay, N.; Kleinlein, J.; Schmidt, G.

    2014-11-01

    Resistive switching, i.e., the remanent (reversible) change of a device's resistance, is a widely investigated phenomenon as it holds the prospect for realizing high density memory devices. Resistive switching has also been observed in organic semiconductors; however, a clear understanding of the underlying physics could not yet be obtained. Possible options are for example interface effects at the electrodes or the formation and destruction of filaments. Here we present resistive switching in an organic spin valve based on tunneling anisotropic magnetoresistance. Similar to experiments in conventional spin-valve devices with two ferromagnetic electrodes we observe a modulation of the magnetoresistance by the electrical switching. However, as the magnetoresistance effect's origin is unambiguously clear, which is not always the case for effects in conventional structures, it can be exploited to prove that a tunnel barrier exists at the interface between the ferromagnetic oxide electrode and the organic semiconductor. Furthermore our experiments reveal that this barrier is reversibly modified during the switching, which causes both the change in magnetoresistance and total device resistance. Quantitative analysis indicates that the barrier is situated in the oxide layer. A phenomenological model provides a full description of the microscopic processes involved in the resistive switching.

  7. Handheld, giant magnetoresistive-sensor-based eddy current probes

    NASA Astrophysics Data System (ADS)

    Brady, S. K.; Palmer, D. D.

    2012-05-01

    The minimum crack length detectable with conventional eddy current probes increases dramatically as the thickness of metal through which the inspection is performed increases. The skin depth phenomenon is unavoidable, and demands low frequency inspection, hindering sensitivity. However, one time derivative introduced by Faraday's Law can be avoided by using giant magnetoresistive sensors to detect eddy currents instead of conventional coils, improving sensitivity. The theory will be explained, along with some probe designs and the observed benefits in sensitivity.

  8. Anisotropic and strong negative magnetoresistance in the three-dimensional topological insulator Bi2Se3

    NASA Astrophysics Data System (ADS)

    Wiedmann, S.; Jost, A.; Fauqué, B.; van Dijk, J.; Meijer, M. J.; Khouri, T.; Pezzini, S.; Grauer, S.; Schreyeck, S.; Brüne, C.; Buhmann, H.; Molenkamp, L. W.; Hussey, N. E.

    2016-08-01

    We report on high-field angle-dependent magnetotransport measurements on epitaxial thin films of Bi2Se3 , a three-dimensional topological insulator. At low temperature, we observe quantum oscillations that demonstrate the simultaneous presence of bulk and surface carriers. The magnetoresistance of Bi2Se3 is found to be highly anisotropic. In the presence of a parallel electric and magnetic field, we observe a strong negative longitudinal magnetoresistance that has been considered as a smoking gun for the presence of chiral fermions in a certain class of semimetals due to the so-called axial anomaly. Its observation in a three-dimensional topological insulator implies that the axial anomaly may be in fact a far more generic phenomenon than originally thought.

  9. Anisotropic magnetoresistance and current-perpendicular-to-plane giant magnetoresistance in epitaxial NiMnSb-based multilayers

    NASA Astrophysics Data System (ADS)

    Kwon, B.; Sakuraba, Y.; Sukegawa, H.; Li, S.; Qu, G.; Furubayashi, T.; Hono, K.

    2016-01-01

    We fabricated (001)-oriented C1b-NiMnSb epitaxial films on MgO substrate by a magnetron sputtering system and systematically investigated the structure, magnetic property, and anisotropic magnetoresistance (AMR) effect. NiMnSb film was deposited using a stoichiometric NiMnSb target which has Mn-deficient (Mn ˜ 28.7 at. %) off-stoichiometric composition ratio. We have investigated bulk spin-polarization in NiMnSb films by measuring AMR on the basis of recent study for half-metallic L21-Heusler compounds. Although the negative sign of AMR ratio, which is indicative of half-metallic nature, was observed in the single layer NiMnSb films, the magnitude of AMR ratio (-0.10% at RT) was about half of the largest value reported for half-metallic L21-Heusler compounds. The current-perpendicular-to-plane (CPP) giant magnetoresistance (GMR) devices of NiMnSb/Ag/NiMnSb show MR ratio of 13.2% at 10 K and 4.2% at 300 K, which is higher than the previous result for NiMnSb/Cu/NiMnSb CPP-GMR devices [Caballero et al., J. Magn. Magn. Mater. 198-199, 55 (1999)], but much less than the CPP-GMR using L21-Heusler electrodes. The reduction of intrinsic bulk spin-polarization originating from the Mn-deficiency in NiMnSb layer is expected to be the main reason for small MR values.

  10. Tunnelling anisotropic magnetoresistance at La0.67Sr0.33MnO3-graphene interfaces

    NASA Astrophysics Data System (ADS)

    Phillips, L. C.; Lombardo, A.; Ghidini, M.; Yan, W.; Kar-Narayan, S.; Hämäläinen, S. J.; Barbone, M.; Milana, S.; van Dijken, S.; Ferrari, A. C.; Mathur, N. D.

    2016-03-01

    Using ferromagnetic La0.67Sr0.33MnO3 electrodes bridged by single-layer graphene, we observe magnetoresistive changes of ˜32-35 MΩ at 5 K. Magneto-optical Kerr effect microscopy at the same temperature reveals that the magnetoresistance arises from in-plane reorientations of electrode magnetization, evidencing tunnelling anisotropic magnetoresistance at the La0.67Sr0.33MnO3-graphene interfaces. Large resistance switching without spin transport through the non-magnetic channel could be attractive for graphene-based magnetic-sensing applications.

  11. Large anisotropic magnetoresistance across the Schottky interface in all oxide ferromagnet/semiconductor heterostructures

    NASA Astrophysics Data System (ADS)

    Li, P.; Guo, B. L.; Bai, H. L.

    2011-06-01

    Over 80% fourfold symmetric anisotropic magnetoresistance (AMR) across the interface is observed in epitaxial Fe3O4 (001)/Nb:SrTiO3 (001) heterostructures, while the twofold symmetric AMR across the interface in epitaxial Fe3O4 (111)/ZnO (0001) heterostructures is rather small. The large AMR across the interface is considered to be induced by the assistance of magnetocrystalline anisotropic energy for the transport electrons while the applied voltage bias is near the height of Schottky barrier, which is further verified by the fact that a larger critical current is needed for the maximum AMR in the Fe3O4 (001)/Nb:SrTiO3 (001) heterostructures with heavier Nb-doping.

  12. Temperature dependence of anisotropic magnetoresistance in antiferromagnetic Sr{sub 2}IrO{sub 4}

    SciTech Connect

    Wang, C.; Seinige, H.; Tsoi, M.; Cao, G.; Zhou, J.-S.; Goodenough, J. B.

    2015-05-07

    Temperature-dependent magnetotransport properties of the antiferromagnetic semiconductor Sr{sub 2}IrO{sub 4} are investigated with point-contact devices. The point-contact technique allows to probe very small volumes and, therefore, to look for electronic transport on a microscopic scale. Point-contact measurements with single crystals of Sr{sub 2}IrO{sub 4} were intended to see whether the additional local resistance associated with a small contact area between a sharpened Cu tip and the antiferromagnet shows magnetoresistance (MR) such as that seen in bulk crystals. Point-contact measurements at liquid nitrogen temperature revealed large MRs (up to 28%) for modest magnetic fields (250 mT) applied within an IrO{sub 2} (ab) plane with angular dependence showing a crossover from four-fold to two-fold symmetry with an increasing magnetic field. Point contact measurement exhibits distinctive anisotropic magnetoresistance (AMR) in comparison to a bulk experiment, imposing intriguing questions about the mechanism of AMR in this material. Temperature-dependent MR measurements show that the MR falls to zero at the Neel temperature, but the temperature dependence of the MR ratio differs qualitatively from that of the resistivity. This AMR study helps to unveil the entanglement between electronic transport and magnetism in Sr{sub 2}IrO{sub 4} while the observed magnetoresistive phenomena can be potentially used to sense the antiferromagnetic order parameter in spintronic applications.

  13. Magnetoresistive performance and comparison of supermagnetic nanoparticles on giant magnetoresistive sensor-based detection system

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Wang, Yi; Tu, Liang; Feng, Yinglong; Klein, Todd; Wang, Jian-Ping

    2014-07-01

    Giant magnetoresistive (GMR) biosensors have emerged as powerful tools for ultrasensitive, multiplexed, real-time electrical readout, and rapid biological/chemical detection while combining with magnetic particles. Finding appropriate magnetic nanoparticles (MNPs) and its influences on the detection signal is a vital aspect to the GMR bio-sensing technology. Here, we report a GMR sensor based detection system capable of stable and convenient connection, and real-time measurement. Five different types of MNPs with sizes ranging from 10 to 100 nm were investigated for GMR biosensing. The experiments were accomplished with the aid of DNA hybridization and detection architecture on GMR sensor surface. We found that different MNPs markedly affected the final detection signal, depending on their characteristics of magnetic moment, size, and surface-based binding ability, etc. This work may provide a useful guidance in selecting or preparing MNPs to enhance the sensitivity of GMR biosensors, and eventually lead to a versatile and portable device for molecular diagnostics.

  14. Tunneling anisotropic magnetoresistance effect of single adatoms on a noncollinear magnetic surface.

    PubMed

    Caffrey, Nuala M; Schröder, Silke; Ferriani, Paolo; Heinze, Stefan

    2014-10-01

    The tunneling anisotropic magnetoresistance (TAMR) effect demonstrates the sensitivity of spin-polarized electron transport to the orientation of the magnetization with respect to the crystallographic axes. As the TAMR effect requires only a single magnetic electrode, in contrast to the tunneling magnetoresistance effect, it offers an attractive route to alternative spintronic applications. In this work we consider the TAMR effect at the single-atom limit by investigating the anisotropy of the local density of states (LDOS) in the vacuum above transition-metal adatoms adsorbed on a noncollinear magnetic surface, the monolayer of Mn on W(1 1 0). This surface presents a cycloidal spin spiral ground state with an angle of 173° between neighboring spins and thus allows a quasi-continuous exploration of the angular dependence of the TAMR of adsorbed adatoms using scanning tunneling microscopy. Using first-principle calculations, we investigate the TAMR of Co, Rh and Ir adatoms on Mn/W(1 1 0) and relate our results to the magnetization-direction-dependent changes in the LDOS. The anisotropic effect is found to be enhanced dramatically on the adsorption of heavy transition-metal atoms, with values of up to 50% predicted from our calculations. This effect will be measurable even with a non-magnetic STM tip. PMID:25212899

  15. Imaging Ferromagnetic Tracers with a Magnetoresistive Sensors Array

    NASA Astrophysics Data System (ADS)

    Leyva, Juan A.; Carneiro, Antonio A. O.; Murta, Luís O.; Baffa, O.

    2006-09-01

    The aim of this work was to study the feasibility to obtain images from a distribution of ferromagnetic tracers using a magnetoresistive multichannel sensor array (MRA). A magnetic imaging system formed by a linear array composed of 12 magnetoresistive sensors (Honeywell HMC 1001) was constructed covering a scanning area of (16×18) cm2. The signal was pre-processed for off-set correction and interpolation to generate a matrix of (256×256). The point spread function of the MRA was evaluated and the sensors were spaced accordingly. The magnetic images were generated by mapping the response of the MRA at short distances from the presence of a magnetite powder dispersed in planar phantoms with different shapes. The phantoms were magnetized by a pulse field of approximately 80 mT produced by a Helmholtz coil. Using the Wiener filtering, the magnetic source images were obtained. We conclude that this biomagnetic method can be successfully used to generate planar functional images of the gastrointestinal tract using magnetic markers in the near field.

  16. Anisotropic magnetoresistance and piezoresistivity in structured Fe3O4-silver particles in PDMS elastomers at room temperature.

    PubMed

    Mietta, José L; Ruiz, Mariano M; Antonel, P Soledad; Perez, Oscar E; Butera, Alejandro; Jorge, Guillermo; Negri, R Martín

    2012-05-01

    ) increases exponentially when a pressure, P, is applied, and the magnitude of the change strongly depends on what direction P is exerted (anisotropic piezoresistivity). In addition, at a fixed pressure, σ increases exponentially in the presence of an external magnetic field (H) only when the field H is applied in the collinear direction with respect to the electrical flux, J. Excellent fits of the experimental data σ versus H and P were achieved using a model that considers the intergrain electron transport where an H-dependent barrier was considered in addition to the intrinsic intergrain resistance in a percolation process. The H-dependent barrier decreases with the applied field, which is attributed to the increasing match of spin-polarization in the silver covers between grains. The effect is anisotropic (i.e., the sensitivity of the magnetoresistive effect is dependent on the relative orientation between H and the current flow J). In the case of Fe(3)O(4)@ Ag, when H and J are parallel to the needles in the PDMS matrix, we obtain changes in σ up to 50% for fields of 400 mT and with resistances on the order of 1-10 Ω. Magnetoresistive and magnetoelastic properties make these materials very interesting for applications in flexible electronics, electronic skins, anisotropic pressure, and magnetic field sensors. PMID:22475548

  17. Tunnelling anisotropic magnetoresistance due to antiferromagnetic CoO tunnel barriers

    PubMed Central

    Wang, K.; Sanderink, J. G. M.; Bolhuis, T.; van der Wiel, W. G.; de Jong, M. P.

    2015-01-01

    A new approach in spintronics is based on spin-polarized charge transport phenomena governed by antiferromagnetic (AFM) materials. Recent studies have demonstrated the feasibility of this approach for AFM metals and semiconductors. We report tunneling anisotropic magnetoresistance (TAMR) due to the rotation of antiferromagnetic moments of an insulating CoO layer, incorporated into a tunnel junction consisting of sapphire(substrate)/fcc-Co/CoO/AlOx/Al. The ferromagnetic Co layer is exchange coupled to the AFM CoO layer and drives rotation of the AFM moments in an external magnetic field. The results may help pave the way towards the development of spintronic devices based on AFM insulators. PMID:26486931

  18. Four-fold symmetric anisotropic magnetoresistance of single-crystalline Ni(001) film

    SciTech Connect

    Xiao, X.; Li, J. X.; Ding, Z.; Wu, Y. Z.

    2015-11-28

    Temperature, current-direction, and film-thickness dependent anisotropic magnetoresistance measurements were performed on single-crystalline face-centered-cubic nickel films. An additional four-fold symmetry was confirmed besides the typical two-fold term even at room temperature. The angular-dependent longitudinal resistivity resolves into a two-fold term, which varies as a function of current direction, and a four-fold term, which is isotropically independent of current direction. The experimental results are interpreted well using an expression based on the phenomenological model. Both the two- and four-fold terms vary inversely proportional to film thickness, indicating that interfacial scattering can significantly influence the spin-dependent transport properties.

  19. Stability of standing spin wave in permalloy thin film studied by anisotropic magnetoresistance effect

    SciTech Connect

    Yamanoi, K.; Yokotani, Y.; Cui, X.; Yakata, S.; Kimura, T.

    2015-12-21

    We have investigated the stability for the resonant spin precession under the strong microwave magnetic field by a specially developed detection method using the anisotropic magnetoresistance effect. The electrically separated excitation and detection circuits enable us to investigate the influence of the heating effect and the nonuniform spin dynamics independently. The large detecting current is found to induce the field shift of the resonant spectra because of the Joule heating. From the microwave power dependence, we found that the linear response regime for the standing spin wave is larger than that for the ferromagnetic resonance. This robust characteristic of the standing spin wave is an important advantage for the high power operation of the spin-wave device.

  20. Spin pumping and anisotropic magnetoresistance voltages in magnetic bilayers: Theory and experiment

    NASA Astrophysics Data System (ADS)

    Azevedo, A.; Vilela-Leão, L. H.; Rodríguez-Suárez, R. L.; Lacerda Santos, A. F.; Rezende, S. M.

    2011-04-01

    We investigate experimentally and theoretically the dc voltage generated in ferromagnetic and nonmagnetic metal bilayers under ferromagnetic resonance. The voltage is given by a superposition of the contributions from spin pumping (VSP) and anisotropic magnetoresistance (VAMR). A theoretical model is presented that separately determines VSP and VAMR as a function of the applied static field intensity as well the in-plane angle. The model is used to interpret a detailed set of data obtained in a series of Ni81Fe19/Pt samples excited by in-plane ferromagnetic resonance. The results show excellent agreement between theory and the measured voltages as a function of the Permalloy and Pt layer thicknesses. Our findings show that the quantitative separation of both effects is crucial to the interpretation of experiments and the determination of the spin Hall angle and spin-diffusion length.

  1. Tunneling Anisotropic Magnetoresistance in Fe Nanoparticles Embedded in MgO Matrix

    NASA Astrophysics Data System (ADS)

    Pham, T. V.; Miwa, S.; Suzuki, Y.

    2016-05-01

    The tunnel magnetoresistance (TMR) effect is related to the relative orientation of the magnetizations of the two ferromagnetic electrodes in magnetic tunnel junctions (MTJs). The tunnel anisotropic magnetoresistance (TAMR) effect is related to the orientation of the magnetization with respect to the current direction or the crystallographic axes. Beyond the TMR, the TAMR is not only present in MTJs in which both electrodes are ferromagnetic but may also appear in tunnel structures with a single magnetic electrode. We investigated the magnetotransport properties in an Au/MgO/Fe nanoparticles/MgO/Cu tunnel junction. We found that both the TMR and TAMR can appear in tunnel junctions with Fe nanoparticles embedded in an MgO matrix. The TMR is attributed to spin-dependent tunneling between Fe nanoparticles, so the device resistance depends on the magnetization directions of adjacent Fe nanoparticles. The TAMR is attributed to the interfacial spin-orbit interaction, so the device resistance depends on each magnetization direction of an Fe nanoparticle. This is the first observation of the TAMR in Fe nanoparticles embedded in an MgO matrix.

  2. Temperature and bias dependence of anisotropic magnetoresistance in antiferromagnetic Sr2IrO4

    NASA Astrophysics Data System (ADS)

    Seinige, Heidi; Wang, Cheng; Cao, Gang; Zhou, Jian-Shi; Goodenough, John B.; Tsoi, Maxim

    2015-03-01

    We study anisotropic magnetoresistance (AMR) in antiferromagnetic (AFM) Mott insulator Sr2IrO4. Such AMR is a promising candidate for monitoring the magnetic order parameter in AFM spintronics. Here we present temperature- and electrical bias-dependent measurements of the point-contact AMR in single crystals of Sr2IrO4. The point-contact technique allows to probe very small volumes and, therefore, look for electronic transport in Sr2IrO4 on a microscopic scale. Point-contact measurements at liquid nitrogen temperature revealed a large negative magnetoresistance (MR) for magnetic fields applied within IrO2 a-b plane and electric currents flowing perpendicular to the plane. The observed MR decreases with increasing temperature and falls to zero at TNéel ~ 240 K. Interestingly, the temperature dependence of MR ratios differs qualitatively from that of the resistivity. The point-contact measurements also show a strong dependence of MR on the dc bias applied to the contact. The latter can be associated with correlations between electronic transport and magnetic order in Sr2IrO4. This work was supported in part by C-SPIN, one of six centers of STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA, and by NSF Grants DMR-1207577, DMR-1265162 and DMR-1122603.

  3. Large and Anisotropic Linear Magnetoresistance in Single Crystals of Black Phosphorus Arising From Mobility Fluctuations.

    PubMed

    Hou, Zhipeng; Yang, Bingchao; Wang, Yue; Ding, Bei; Zhang, Xiaoming; Yao, Yuan; Liu, Enke; Xi, Xuekui; Wu, Guangheng; Zeng, Zhongming; Liu, Zhongyuan; Wang, Wenhong

    2016-01-01

    Black Phosphorus (BP) is presently attracting immense research interest on the global level due to its high mobility and suitable band gap for potential application in optoelectronics and flexible devices. It was theoretically predicted that BP has a large direction-dependent electrical and magnetotransport anisotropy. Investigations on magnetotransport of BP may therefore provide a new platform for studying the nature of electron transport in layered materials. However, to the best of our knowledge, magnetotransport studies, especially the anisotropic magnetoresistance (MR) effect in layered BP, are rarely reported. Here, we report a large linear MR up to 510% at a magnetic field of 7 Tesla in single crystals of BP. Analysis of the temperature and angle dependence of MR revealed that the large linear MR in our sample originates from mobility fluctuations. Furthermore, we reveal that the large linear MR of layered BP in fact follows a three-dimensional behavior rather than a two-dimensional one. Our results have implications to both the fundamental understanding and magnetoresistive device applications of BP. PMID:27030141

  4. Large and Anisotropic Linear Magnetoresistance in Single Crystals of Black Phosphorus Arising From Mobility Fluctuations

    NASA Astrophysics Data System (ADS)

    Hou, Zhipeng; Yang, Bingchao; Wang, Yue; Ding, Bei; Zhang, Xiaoming; Yao, Yuan; Liu, Enke; Xi, Xuekui; Wu, Guangheng; Zeng, Zhongming; Liu, Zhongyuan; Wang, Wenhong

    2016-03-01

    Black Phosphorus (BP) is presently attracting immense research interest on the global level due to its high mobility and suitable band gap for potential application in optoelectronics and flexible devices. It was theoretically predicted that BP has a large direction-dependent electrical and magnetotransport anisotropy. Investigations on magnetotransport of BP may therefore provide a new platform for studying the nature of electron transport in layered materials. However, to the best of our knowledge, magnetotransport studies, especially the anisotropic magnetoresistance (MR) effect in layered BP, are rarely reported. Here, we report a large linear MR up to 510% at a magnetic field of 7 Tesla in single crystals of BP. Analysis of the temperature and angle dependence of MR revealed that the large linear MR in our sample originates from mobility fluctuations. Furthermore, we reveal that the large linear MR of layered BP in fact follows a three-dimensional behavior rather than a two-dimensional one. Our results have implications to both the fundamental understanding and magnetoresistive device applications of BP.

  5. Long phase coherence length and anisotropic magnetoresistance in MgZnO thin film

    SciTech Connect

    Lv, Meng; Xu, Yonggang; Yu, Guolin Lin, Tie; Hu, Gujin; Chu, Junhao; Wang, Hao; Zhang, Huahan; Dai, Ning

    2015-04-21

    We comprehensively investigate magnetotransport properties of MgZnO thin film grown on ZnO substrate by molecular-beam epitaxy. We measure the weak localization effect and extract the electron phase coherence length by fitting to a three-dimensional weak localization theory and by analyzing the different changing rate of the magnetoresistance, results of which are in good agreement with each other. The phase coherence length ranges from 38.4±1    nm at 50 K to 99.8±3.6 nm at 1.4  K, almost the same as that of ZnO nanoplates and In-doped ZnO nanowires, and its temperature dependence is found to scale as T{sup −3/4}. Meanwhile, we study the anisotropic magnetoresistance resulting from the geometric effect as well as the Lorentz force induced path-length effect, which will be enhanced in higher magnetic fields.

  6. Large and Anisotropic Linear Magnetoresistance in Single Crystals of Black Phosphorus Arising From Mobility Fluctuations

    PubMed Central

    Hou, Zhipeng; Yang, Bingchao; Wang, Yue; Ding, Bei; Zhang, Xiaoming; Yao, Yuan; Liu, Enke; Xi, Xuekui; Wu, Guangheng; Zeng, Zhongming; Liu, Zhongyuan; Wang, Wenhong

    2016-01-01

    Black Phosphorus (BP) is presently attracting immense research interest on the global level due to its high mobility and suitable band gap for potential application in optoelectronics and flexible devices. It was theoretically predicted that BP has a large direction-dependent electrical and magnetotransport anisotropy. Investigations on magnetotransport of BP may therefore provide a new platform for studying the nature of electron transport in layered materials. However, to the best of our knowledge, magnetotransport studies, especially the anisotropic magnetoresistance (MR) effect in layered BP, are rarely reported. Here, we report a large linear MR up to 510% at a magnetic field of 7 Tesla in single crystals of BP. Analysis of the temperature and angle dependence of MR revealed that the large linear MR in our sample originates from mobility fluctuations. Furthermore, we reveal that the large linear MR of layered BP in fact follows a three-dimensional behavior rather than a two-dimensional one. Our results have implications to both the fundamental understanding and magnetoresistive device applications of BP. PMID:27030141

  7. Magnetoresistive performance and comparison of supermagnetic nanoparticles on giant magnetoresistive sensor-based detection system

    PubMed Central

    Wang, Wei; Wang, Yi; Tu, Liang; Feng, Yinglong; Klein, Todd; Wang, Jian-Ping

    2014-01-01

    Giant magnetoresistive (GMR) biosensors have emerged as powerful tools for ultrasensitive, multiplexed, real-time electrical readout, and rapid biological/chemical detection while combining with magnetic particles. Finding appropriate magnetic nanoparticles (MNPs) and its influences on the detection signal is a vital aspect to the GMR bio-sensing technology. Here, we report a GMR sensor based detection system capable of stable and convenient connection, and real-time measurement. Five different types of MNPs with sizes ranging from 10 to 100 nm were investigated for GMR biosensing. The experiments were accomplished with the aid of DNA hybridization and detection architecture on GMR sensor surface. We found that different MNPs markedly affected the final detection signal, depending on their characteristics of magnetic moment, size, and surface-based binding ability, etc. This work may provide a useful guidance in selecting or preparing MNPs to enhance the sensitivity of GMR biosensors, and eventually lead to a versatile and portable device for molecular diagnostics. PMID:25043673

  8. Magnetoresistive-superconducting mixed sensors for biomagnetic applications

    NASA Astrophysics Data System (ADS)

    Pannetier-Lecoeur, M.; Fermon, C.; Dyvorne, H.; Jacquinot, J. F.; Polovy, H.; Walliang, A. L.

    2010-05-01

    When coupled to a giant magnetoresistive (GMR) sensor, a superconducting loop containing a constriction can be a very sensitive magnetometer. It has thermal noise levels of few fT/sqrt(Hz), comparable to low- Tc SQUID noise, with a flat frequency response. These mixed sensors are good candidates for detection of weak biomagnetic signals, like a cardiac or neuronal signature. Furthermore, being sensitive to the flux, mixed sensors can be used for nuclear magnetic resonance (NMR) detection and Magnetic Resonance Imaging (MRI) especially at low fields. They are very robust and accept strong RF pulses with a very short recovery time compared to tuned RF coils, which allow measurements of broad signals (short relaxation time or multiple resonances). We will first present the last generation sensors having a noise level of 3 fT/sqrt(Hz) and we will show signals measured at low frequency (magnetocardiography-magnetoencephalography range) and at higher frequency (NMR signals). The use of additional flux transformers for improving the signal-to-noise will be discussed. Finally, we will present perspectives for low-field MRI, which can be combined with neural signal detection (MEG), especially for brain anatomy and temporal response on the same experimental setup.

  9. Strain-induced anisotropic low-field magnetoresistance of La-Sr-Mn-O thin films

    NASA Astrophysics Data System (ADS)

    Choi, Kyung-Ku; Taniyama, Tomoyasu; Yamazaki, Yohtaro

    2001-12-01

    Sputtered La0.71Sr0.29Mn1.01O3-δ (LSMO) thin films on (001) SrTiO3, polycrystalline yttria-stabilized zirconia (YSZ) and (112¯0) sapphire substrates demonstrate the distinctive low-field magnetoresistance (MR) correlated with the microstructure and the strain of the films. The epitaxial LSMO film on (001) SrTiO3 shows the in-plane magnetic anisotropy with [110] easy axis and the attendant anisotropic MR. The polycrystalline films on YSZ and sapphire substrates with grain sizes from 20 to 60 nm exhibit different anisotropic feature of transport: the isotropic MR of the film on YSZ and the large anisotropy on sapphire substrates. Moreover, in the (112¯0) film plane of sapphire substrate, the [1¯100]SAP magnetic easy axis appears due to a large tensile stress, and the longitudinal MR becomes pronounced along the [0001]SAP hard axis. This implies that the anisotropy of the low-field MR is attributed to the stress induced by the thermal expansion mismatch between film and substrate. These results emphasize that the low-field MR in the polycrystalline manganite can be advanced by the strain induced magnetic anisotropy.

  10. Integrated giant magnetoresistance bridge sensors with transverse permanent magnet biasing

    NASA Astrophysics Data System (ADS)

    Ku, Wanjun; Silva, F.; Bernardo, J.; Freitas, P. P.

    2000-05-01

    Two types of giant magnetoresistance (GMR) multilayer bridge sensors with integrated permanent magnet biasing are demonstrated. These sensors differ from previous designs where external permanent magnets were used. The bridges consist of four active GMR multilayer elements at the first antiferromagnetic coupling peak of a NiFe/[NiFe/CoFe/Cu]10 structure (GMR=18%). Bridge linearization is obtained by creating opposite biasing fields of equal amplitude (±200 Oe) in contiguous GMR elements of the bridge structure. This is achieved either by using pairs of permanent magnets with the same Mrt value (14 memu/cm2) but different coercivities (type I bridge, Hc1=1400 Oe, Hc2=800 Oe), or by using a single type of permanent magnet and placing the GMR sensor either under the magnet, or on its side (type II bridge). Linear ranges of ±200 Oe with field sensitivities of 0.3 mV/(V×Oe) were obtained in these bridges.

  11. Unexploded ordnance detection using imaging giant magnetoresistive (GMR) sensor arrays

    SciTech Connect

    Chaiken, A., LLNL

    1997-05-06

    False positive detections account for a great part of the expense associated with unexploded ordnance (UXO) remediation. Presently fielded systems like pulsed electromagnetic induction systems and cesium-vapor magnetometers are able to distinguish between UXO and other metallic ground clutter only with difficulty. The discovery of giant magnetoresistance (GMR) has led to the development of a new generation of integrated-circuit magnetic sensors that are far more sensitive than previously available room-temperature-operation electronic devices. The small size of GMR sensors makes possible the construction of array detectors that can be used to image the flux emanating from a ferrous object or from a non-ferrous object with eddy currents imposed by an external coil. The purpose of a GMR-based imaging detector would be to allow the operator to easily distinguish between UXO and benign objects (like shrapnel or spent bullets) that litter formerly used defense sites (FUDS). In order to demonstrate the potential of a GMR-based imaging technology, a crude magnetic imaging system has been constructed using commercially available sensors. The ability to roughly determine the outline and disposition of magnetic objects has been demonstrated. Improvements to the system which are necessary to make it into a high-performance UXO detector are outlined.

  12. Magnetization reversal in individual Py and CoFeB nanotubes locally probed via anisotropic magnetoresistance and anomalous Nernst effect

    NASA Astrophysics Data System (ADS)

    Baumgaertl, K.; Heimbach, F.; Maendl, S.; Rueffer, D.; Fontcuberta i Morral, A.; Grundler, D.

    2016-03-01

    Using anisotropic magnetoresistance in a multi-probe configuration and local heating with a scanning laser, we investigate the magnetization reversal of individual permalloy (Py) and CoFeB nanotubes with spatial resolution. Nanocrystalline Py and amorphous CoFeB nanotubes are found to reverse via domain wall movement and chirality switching, respectively. Our experiments provide an understanding of the role of microstructure and magnetic anisotropy in the switching of ferromagnetic nanotubes at room temperature.

  13. Fabrication and Characterization of Giant Magnetoresistive (GMR) Sensor Microelectromechanical System (MEMS) Device

    NASA Technical Reports Server (NTRS)

    Ramesham, R.; Olivas, J.; Stokes, S.; Wilson, W.; Generazio, E.

    1999-01-01

    This paper discusses the fabrication aspects of a sensor device that is based on a sputter deposited multilayer giant magnetoresistive (GMR) sensor. The device consists of a micromachined microstructure (membrane), GMR sensor, and a sputtered hard magnetic thin film element on to microstructure.

  14. Tunneling anisotropic magnetoresistance in a magnetic tunnel junction with half-metallic electrodes

    NASA Astrophysics Data System (ADS)

    Burton, J. D.; Tsymbal, Evgeny Y.

    2016-01-01

    Tunneling anisotropic magnetoresistance (TAMR) is the difference in resistance of a magnetic tunnel junction due to a change in magnetization direction of one or both magnetic electrodes with respect to the flow of current. We present the results of first-principles density functional calculations of the TAMR effect in magnetic tunnel junctions with L a0.7S r0.3Mn O3 (LSMO) electrodes and a SrTi O3 (STO) tunneling barrier. We find an ˜500 % difference in resistance between magnetization in the plane and out of the plane. This large TAMR effect originates from the half-metallic nature of LSMO: When magnetization is out of plane spin-orbit coupling (SOC) contributions to the transmission come only from spin-flip scattering, which is intrinsically small due to the half-metallicity. For in-plane magnetization, however, there is a large non-spin-flip SOC contribution to the conductance. The large magnitude of the effect stems from the additional fact that there is an inherent polar discontinuity between LSMO and STO which leads to quasilocalized states at the interface whose influence on tunneling is strongly dependent on the magnetization orientation.

  15. Strongly Anisotropic Ballistic Magnetoresistance in Compact Three-Dimensional Semiconducting Nanoarchitectures

    NASA Astrophysics Data System (ADS)

    Ortix, Carmine; Chang, Ching-Hao; van den Brink, Jeroen

    2015-03-01

    In this talk, I will show that in non-magnetic semiconducting bilayer or multilayer thin film systems rolled-up into compact quasi-one-dimensional nanoarchitectures, the ballistic magnetoresistance is very anisotropic: conductances depend strongly on the direction of an externally applied magnetic field. This phenomenon originates from the curved open geometry of rolled-up nanotubes, which leads to a tunability of the number of one-dimensional magnetic subbands crossing the Fermi energy. The experimental significance of this phenomenon is illustrated by a sizable anisotropy that scales with the inverse of the number of windings, and persists up to a critical temperature that can be strongly enhanced by increasing the strength of the external magnetic field or the characteristic radius of curvature, and can reach room temperature. The financial support of the Future and Emerging Technologies (FET) programme within the Seventh Framework Programme for Research of the European Commission, under FET-Open Grant Number: 618083 (CNTQC), is gratefully acknowledged.

  16. Transverse anisotropic magnetoresistance effects in pseudo-single-crystal γ'-Fe4N thin films

    NASA Astrophysics Data System (ADS)

    Kabara, Kazuki; Tsunoda, Masakiyo; Kokado, Satoshi

    2016-05-01

    Transverse anisotropic magnetoresistance (AMR) effects, for which magnetization is rotated in an orthogonal plane to the current direction, were investigated at various temperatures, in order to clarify the structural transformation from a cubic to a tetragonal symmetry in a pseudo-single-crystal Fe4N film, which is predicted from the usual in-plane AMR measurements by the theory taking into account the spin-orbit interaction and crystal field splitting of 3d bands. According to a phenomenological theory of AMR, which derives only from the crystal symmetry, a cos 2θ component ( C2 tr ) exists in transverse AMR curves for a tetragonal system but does not for a cubic system. In the Fe4N film, the C2 tr shows a positive small value (0.12%) from 300 K to 50 K. However, the C2 t r increases to negative value below 50 K and reaches to -2% at 5 K. The drastic increasing of the C2 tr demonstrates the structural transformation from a cubic to a tetragonal symmetry below 50 K in the Fe4N film. In addition, the out-of-plane and in-plane lattice constants (c and a) were precisely determined with X-ray diffraction at room temperature using the Nelson-Riely function. As a result, the positive small C2 t r above 50 K is attributed to a slightly distorted Fe4N lattice (c/a = 1.002).

  17. Multiple-stable anisotropic magnetoresistance memory in antiferromagnetic MnTe.

    PubMed

    Kriegner, D; Výborný, K; Olejník, K; Reichlová, H; Novák, V; Marti, X; Gazquez, J; Saidl, V; Němec, P; Volobuev, V V; Springholz, G; Holý, V; Jungwirth, T

    2016-01-01

    Commercial magnetic memories rely on the bistability of ordered spins in ferromagnetic materials. Recently, experimental bistable memories have been realized using fully compensated antiferromagnetic metals. Here we demonstrate a multiple-stable memory device in epitaxial MnTe, an antiferromagnetic counterpart of common II-VI semiconductors. Favourable micromagnetic characteristics of MnTe allow us to demonstrate a smoothly varying zero-field antiferromagnetic anisotropic magnetoresistance (AMR) with a harmonic angular dependence on the writing magnetic field angle, analogous to ferromagnets. The continuously varying AMR provides means for the electrical read-out of multiple-stable antiferromagnetic memory states, which we set by heat-assisted magneto-recording and by changing the writing field direction. The multiple stability in our memory is ascribed to different distributions of domains with the Néel vector aligned along one of the three magnetic easy axes. The robustness against strong magnetic field perturbations combined with the multiple stability of the magnetic memory states are unique properties of antiferromagnets. PMID:27279433

  18. Multiple-stable anisotropic magnetoresistance memory in antiferromagnetic MnTe

    NASA Astrophysics Data System (ADS)

    Kriegner, D.; Výborný, K.; Olejník, K.; Reichlová, H.; Novák, V.; Marti, X.; Gazquez, J.; Saidl, V.; Němec, P.; Volobuev, V. V.; Springholz, G.; Holý, V.; Jungwirth, T.

    2016-06-01

    Commercial magnetic memories rely on the bistability of ordered spins in ferromagnetic materials. Recently, experimental bistable memories have been realized using fully compensated antiferromagnetic metals. Here we demonstrate a multiple-stable memory device in epitaxial MnTe, an antiferromagnetic counterpart of common II-VI semiconductors. Favourable micromagnetic characteristics of MnTe allow us to demonstrate a smoothly varying zero-field antiferromagnetic anisotropic magnetoresistance (AMR) with a harmonic angular dependence on the writing magnetic field angle, analogous to ferromagnets. The continuously varying AMR provides means for the electrical read-out of multiple-stable antiferromagnetic memory states, which we set by heat-assisted magneto-recording and by changing the writing field direction. The multiple stability in our memory is ascribed to different distributions of domains with the Néel vector aligned along one of the three magnetic easy axes. The robustness against strong magnetic field perturbations combined with the multiple stability of the magnetic memory states are unique properties of antiferromagnets.

  19. Multiple-stable anisotropic magnetoresistance memory in antiferromagnetic MnTe

    PubMed Central

    Kriegner, D.; Výborný, K.; Olejník, K.; Reichlová, H.; Novák, V.; Marti, X.; Gazquez, J.; Saidl, V.; Němec, P.; Volobuev, V. V.; Springholz, G.; Holý, V.; Jungwirth, T.

    2016-01-01

    Commercial magnetic memories rely on the bistability of ordered spins in ferromagnetic materials. Recently, experimental bistable memories have been realized using fully compensated antiferromagnetic metals. Here we demonstrate a multiple-stable memory device in epitaxial MnTe, an antiferromagnetic counterpart of common II–VI semiconductors. Favourable micromagnetic characteristics of MnTe allow us to demonstrate a smoothly varying zero-field antiferromagnetic anisotropic magnetoresistance (AMR) with a harmonic angular dependence on the writing magnetic field angle, analogous to ferromagnets. The continuously varying AMR provides means for the electrical read-out of multiple-stable antiferromagnetic memory states, which we set by heat-assisted magneto-recording and by changing the writing field direction. The multiple stability in our memory is ascribed to different distributions of domains with the Néel vector aligned along one of the three magnetic easy axes. The robustness against strong magnetic field perturbations combined with the multiple stability of the magnetic memory states are unique properties of antiferromagnets. PMID:27279433

  20. Electrical detection of ferromagnetic resonance in ferromagnet/n-GaAs heterostructures by tunneling anisotropic magnetoresistance

    SciTech Connect

    Liu, C.; Boyko, Y.; Geppert, C. C.; Christie, K. D.; Stecklein, G.; Crowell, P. A.; Patel, S. J.; Palmstrøm, C. J.

    2014-11-24

    We observe a dc voltage peak at ferromagnetic resonance (FMR) in samples consisting of a single ferromagnetic (FM) layer grown epitaxially on the n-GaAs (001) surface. The FMR peak is detected as an interfacial voltage with a symmetric line shape and is present in samples based on various FM/n-GaAs heterostructures, including Co{sub 2}MnSi/n-GaAs, Co{sub 2}FeSi/n-GaAs, and Fe/n-GaAs. We show that the interface bias voltage dependence of the FMR signal is identical to that of the tunneling anisotropic magnetoresistance (TAMR) over most of the bias range. Furthermore, we show how the precessing magnetization yields a dc FMR signal through the TAMR effect and how the TAMR phenomenon can be used to predict the angular dependence of the FMR signal. This TAMR-induced FMR peak can be observed under conditions where no spin accumulation is present and no spin-polarized current flows in the semiconductor.

  1. On the importance of sensor height variation for detection of magnetic labels by magnetoresistive sensors

    NASA Astrophysics Data System (ADS)

    Henriksen, Anders Dahl; Wang, Shan Xiang; Hansen, Mikkel Fougt

    2015-07-01

    Magnetoresistive sensors are widely used for biosensing by detecting the signal from magnetic labels bound to a functionalized area that usually covers the entire sensor structure. Magnetic labels magnetized by a homogeneous applied magnetic field weaken and strengthen the applied field when they are over and outside the sensor area, respectively, and the detailed origin of the sensor signal in experimental studies has not been clarified. We systematically analyze the signal from both a single sensor stripe and an array of sensor stripes as function of the geometrical parameters of the sensor stripes as well as the distribution of magnetic labels over the stripes. We show that the signal from sensor stripes with a uniform protective coating, contrary to conventional wisdom in the field, is usually dominated by the contribution from magnetic labels between the sensor stripes rather than by the labels on top of the sensor stripes because these are at a lower height. We therefore propose a shift of paradigm to maximize the signal due to magnetic labels between sensor stripes. Guidelines for this optimization are provided and illustrated for an experimental case from the literature.

  2. Temperature and thickness dependence of tunneling anisotropic magnetoresistance in exchange-biased Py/IrMn/MgO/Ta stacks

    NASA Astrophysics Data System (ADS)

    Reichlová, H.; Novák, V.; Kurosaki, Y.; Yamada, M.; Yamamoto, H.; Nishide, A.; Hayakawa, J.; Takahashi, H.; Maryško, M.; Wunderlich, J.; Marti, X.; Jungwirth, T.

    2016-07-01

    We investigate the thickness and temperature dependence of a series of Ni{}0.8Fe{}0.2/Ir{}0.2Mn{}0.8 bilayer samples with varying thickness ratio of the ferromagnet/antiferromagnet ({{t}}{{FM}}/{{t}}{{AFM}}) in order to explore the exchange coupling strengths in tunneling anisotropic magnetoresistance (TAMR) devices. Specific values of {{t}}{{FM}}/{{t}}{{AFM}} lead to four distinct scenarios with specific electric responses to moderate magnetic fields. The characteristic dependence of the measured TAMR signal on applied voltage allows us to confirm its persistence up to room temperature despite an overlapped contribution by a thermal magnetic noise.

  3. Magnetic anisotropy and anisotropic magnetoresistance in strongly phase separated manganite thin films

    NASA Astrophysics Data System (ADS)

    Kandpal, Lalit M.; Singh, Sandeep; Kumar, Pawan; Siwach, P. K.; Gupta, Anurag; Awana, V. P. S.; Singh, H. K.

    2016-06-01

    The present study reports the impact of magnetic anisotropy (MA) on magnetotransport properties such as the magnetic transitions, magnetic liquid behavior, glass transition and anisotropic magnetoresistance (AMR) in epitaxial film (thickness 42 nm) of strongly phase separated manganite La5/8-yPryCa3/8MnO3 (y≈0.4). Angle dependent magnetization measurement confirms the out-of-plane magnetic anisotropy with the magnetic easy axes aligned in the plane of the film and the magnetic hard axis along the normal to the film plane. The more prominent divergence between the zero filed cooled (ZFC) and field cooled warming (FCW) and the stronger hysteresis between the field cooled cooling (FCC) and FCW magnetization for H ∥ shows the weakening of the magnetic liquid along the magnetic hard axis. The peak at Tp≈42 K in FCW magnetization, which characterizes the onset of spin freezing shifts down to Tp≈18 K as the field direction is switched from the easy axes (H ∥) to the hard axis (H ⊥). The glass transition, which appears at Tg≈28 K for H ∥ disappears for H ⊥. The easy axis magnetization (M∣∣) appears to saturate around H~20 kOe, but the hard axis counterpart (M⊥) does not show such tendency even up to H=50 kOe. MA appears well above the ferromagnetic (FM) transition at T≈170 K, which is nearly the same as the Neel temperature (TN) of M⊥ - T . The temperature dependent resistivity measured at H=10 kOe applied along the easy axis (ρ|| - T) and the hard axis (ρ⊥ - T) shows insulator metal transition (IMT) at ≈106 K and ≈99 K in the cooling cycle, respectively. The large difference between ρ⊥ - T and ρ|| - T during the cooling cycle and in the vicinity of IMT results in huge AMR of ≈-142% and -115%. The observed properties have been explained in terms of the MA induced variation in the relative fraction of the coexisting magnetic phases.

  4. Flux concentration and modulation based magnetoresistive sensor with integrated planar compensation coils

    NASA Astrophysics Data System (ADS)

    Tian, Wugang; Hu, Jiafei; Pan, Mengchun; Chen, Dixiang; Zhao, Jianqiang

    2013-03-01

    1/f noise is one of the main noise sources of magnetoresistive (MR) sensors, which can cause intrinsic detection limit at low frequency. To suppress this noise, the solution of flux concentration and vertical motion modulation (VMM) has been proposed. Magnetic hysteresis in MR sensors is another problem, which degrades their response linearity and detection ability. To reduce this impact, the method of pulse magnetization and magnetic compensation field with integrated planar coils has been introduced. A flux concentration and VMM based magnetoresistive prototype sensor with integrated planar coils was fabricated using microelectromechanical-system technology. The response linearity of the prototype sensors is improved from 0.8% to 0.12%. The noise level is reduced near to the thermal noise level, and the low-frequency detection ability of the prototype sensor is enhanced with a factor of more than 80.

  5. Optimization of magnetoresistive sensor current for on-chip magnetic bead detection using the sensor self-field

    NASA Astrophysics Data System (ADS)

    Henriksen, Anders Dahl; Rizzi, Giovanni; Østerberg, Frederik Westergaard; Hansen, Mikkel Fougt

    2015-04-01

    We investigate the self-heating of magnetoresistive sensors used for measurements on magnetic beads in magnetic biosensors. The signal from magnetic beads magnetized by the field due to the sensor bias current is proportional to the bias current squared. Therefore, we aim to maximize the bias current while limiting the sensor self-heating. We systematically characterize and model the Joule heating of magnetoresistive sensors with different sensor geometries and stack compositions. The sensor heating is determined using the increase of the sensor resistance as function of the bias current. The measured temperature increase is in good agreement with a finite element model and a simple analytical thermal model. The heat conductance of our system is limited by the 1 μm thick electrically insulating silicon dioxide layer between the sensor stack and the underlying silicon wafer, thus the heat conductance is proportional to the sensor area and inversely proportional to the oxide thickness. This simple heat conductance determines the relationship between bias current and sensor temperature, and we show that 25 μm wide sensor on a 1 μm oxide can sustain a bias current of 30 mA for an allowed temperature increase of 5 °C. The method and models used are generally applicable for thin film sensor systems. Further, the consequences for biosensor applications of the present sensor designs and the impact on future sensor designs are discussed.

  6. Development and Application of Wide Bandwidth Magneto-Resistive Sensor Based Eddy Current Probe

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A.; Simpson, John

    2010-01-01

    The integration of magneto-resistive sensors into eddy current probes can significantly expand the capabilities of conventional eddy current nondestructive evaluation techniques. The room temperature solid-state sensors have typical bandwidths in the megahertz range and resolutions of tens of microgauss. The low frequency sensitivity of magneto-resistive sensors has been capitalized upon in previous research to fabricate very low frequency eddy current sensors for deep flaw detection in multilayer conductors. In this work a modified probe design is presented to expand the capabilities of the device. The new probe design incorporates a dual induction source enabling operation from low frequency deep flaw detection to high frequency high resolution near surface material characterization. Applications of the probe for the detection of localized near surface conductivity anomalies are presented. Finite element modeling of the probe is shown to be in good agreement with experimental measurements.

  7. Lab-on-chip cytometry based on magnetoresistive sensors for bacteria detection in milk.

    PubMed

    Fernandes, Ana C; Duarte, Carla M; Cardoso, Filipe A; Bexiga, Ricardo; Cardoso, Susana; Freitas, Paulo P

    2014-01-01

    Flow cytometers have been optimized for use in portable platforms, where cell separation, identification and counting can be achieved in a compact and modular format. This feature can be combined with magnetic detection, where magnetoresistive sensors can be integrated within microfluidic channels to detect magnetically labelled cells. This work describes a platform for in-flow detection of magnetically labelled cells with a magneto-resistive based cell cytometer. In particular, we present an example for the validation of the platform as a magnetic counter that identifies and quantifies Streptococcus agalactiae in milk. PMID:25196163

  8. Lab-on-Chip Cytometry Based on Magnetoresistive Sensors for Bacteria Detection in Milk

    PubMed Central

    Fernandes, Ana C.; Duarte, Carla M.; Cardoso, Filipe A.; Bexiga, Ricardo.; Cardoso, Susana.; Freitas, Paulo P.

    2014-01-01

    Flow cytometers have been optimized for use in portable platforms, where cell separation, identification and counting can be achieved in a compact and modular format. This feature can be combined with magnetic detection, where magnetoresistive sensors can be integrated within microfluidic channels to detect magnetically labelled cells. This work describes a platform for in-flow detection of magnetically labelled cells with a magneto-resistive based cell cytometer. In particular, we present an example for the validation of the platform as a magnetic counter that identifies and quantifies Streptococcus agalactiae in milk. PMID:25196163

  9. On-chip magnetic bead-based DNA melting curve analysis using a magnetoresistive sensor

    NASA Astrophysics Data System (ADS)

    Rizzi, Giovanni; Østerberg, Frederik W.; Henriksen, Anders D.; Dufva, Martin; Hansen, Mikkel F.

    2015-04-01

    We present real-time measurements of DNA melting curves in a chip-based system that detects the amount of surface-bound magnetic beads using magnetoresistive magnetic field sensors. The sensors detect the difference between the amount of beads bound to the top and bottom sensor branches of the differential sensor geometry. The sensor surfaces are functionalized with wild type (WT) and mutant type (MT) capture probes, differing by a single base insertion (a single nucleotide polymorphism, SNP). Complementary biotinylated targets in suspension couple streptavidin magnetic beads to the sensor surface. The beads are magnetized by the field arising from the bias current passed through the sensors. We demonstrate the first on-chip measurements of the melting of DNA hybrids upon a ramping of the temperature. This overcomes the limitation of using a single washing condition at constant temperature. Moreover, we demonstrate that a single sensor bridge can be used to genotype a SNP.

  10. Giant Magnetoresistive Sensors and Magnetic Labels for Chip-Scale Detection of Immunosorbent Assays

    SciTech Connect

    Rachel Lora Millen

    2005-12-17

    The combination of giant magnetoresistive sensors, magnetic labeling strategies, and biomolecule detection is just beginning to be explored. New readout methods and assay formats are necessary for biomolecules detection to flourish. The work presented in this dissertation describes steps toward the creation of a novel detection method for bioassays utilizing giant magnetoresistive sensors as the readout method. The introduction section contains a brief review of some of the current methods of bioassay readout. The theoretical underpinnings of the giant magnetoresistive effect are also discussed. Finally, the more prominent types of giant magnetoresistive sensors are described, as well as their complicated fabrication. Four data chapters follow the introduction; each chapter is presented as a separate manuscript, either already published or soon to be submitted. Chapter 1 presents research efforts toward the production of a bioassay on the surface of a gold-modified GMR sensor. The testing of this methodology involved the capture of goat a-mouse-coated magnetic nanoparticles on the mouse IgG-modified gold surface. The second, third and fourth chapters describe the utilization of a self-referenced sample stick for scanning across the GMR sensor. The sample stick consisted of alternating magnetic reference and bioactive gold addresses. Chapter 2 is concerned with the characterization of both the scanning readout method and the binding and detection of streptavidin-coated magnetic particles to a biotinylated surface. Chapter 3 advances the sample stick readout with the use of the system for detection of a sandwich immunoassay with rabbit IgG proteins. Finally, simultaneous detection of three IgG proteins is demonstrated in Chapter 4. The dissertation is concluded with a brief summary of the research presented and a discussion of the possible future applications and direction of this work.

  11. Measuring brain activity with magnetoresistive sensors integrated in micromachined probe needles

    NASA Astrophysics Data System (ADS)

    Amaral, José; Gaspar, João; Pinto, Vitor; Costa, Tiago; Sousa, Nuno; Cardoso, Susana; Freitas, Paulo

    2013-05-01

    An alternative neuroscience tool for magnetic field detection is described in this work, providing both micrometer-scale spatial resolution and high sensitivity to detect the extremely small magnetic fields (nT range) induced by the ionic currents flowing within electrically active neurons. The system combines an array of magnetoresistive sensors incorporated on micro-machined Si probes capable of being inserted within the brain current sources. The Si-etch based micromachining process for neural probes is demonstrated in the manufacture of a probe with 15 magnetoresistive sensors in the tip of each shaft. The probe shafts are formed by double-sided deep reactive ion etching on a double-side polished silicon wafer. The shafts typically have the dimensions 1.2 mm × 40 μm × 300 μm and end in chisel-shaped tips with an incorporated magnetoresistive sensor with dimensions of 30 μm × 2 μm. An accompanying interconnect flexible cable is glued and wirebonded enabling precise and flexible positioning of the probes in the neural tissue. Our analyses showed sharply defined probes and probe tips. The electrical and magnetic behavior of the sensors was verified, and a preliminary test with brain slices were performed.

  12. Anisotropic magnetoresistance in tetragonal La{sub 1{minus}{ital x}}Ca{sub {ital x}}MnO{sub {delta}} thin films

    SciTech Connect

    Eckstein, J.N.; Bozovic, I.; ODonnell, J.; Onellion, M.; Rzchowski, M.S.

    1996-08-01

    We have fabricated thin films of La{sub 1{minus}{ital x}}Ca{sub {ital x}}MnO{sub {delta}} with tetragonal symmetry. For low temperatures and magnetic fields the measured magnetoresistance is anisotropic: initially positive for applied magnetic field perpendicular to the film plane and negative for field applied parallel to the film plane. At high temperatures the magnetoresistance is negative for all fields and field orientations. We also observe an in-plane magnetoresistance anisotropy with an angular dependence corresponding to that observed in transition metal ferromagnets. We suggest an interpretation requiring a substantial spin-orbit interaction in the material. {copyright} {ital 1996 American Institute of Physics.}

  13. Magnetic Field Sensors Based on Giant Magnetoresistance (GMR) Technology: Applications in Electrical Current Sensing

    PubMed Central

    Reig, Candid; Cubells-Beltran, María-Dolores; Muñoz, Diego Ramírez

    2009-01-01

    The 2007 Nobel Prize in Physics can be understood as a global recognition to the rapid development of the Giant Magnetoresistance (GMR), from both the physics and engineering points of view. Behind the utilization of GMR structures as read heads for massive storage magnetic hard disks, important applications as solid state magnetic sensors have emerged. Low cost, compatibility with standard CMOS technologies and high sensitivity are common advantages of these sensors. This way, they have been successfully applied in a lot different environments. In this work, we are trying to collect the Spanish contributions to the progress of the research related to the GMR based sensors covering, among other subjects, the applications, the sensor design, the modelling and the electronic interfaces, focusing on electrical current sensing applications. PMID:22408486

  14. Magnetic Field Sensors Based on Giant Magnetoresistance (GMR) Technology: Applications in Electrical Current Sensing.

    PubMed

    Reig, Candid; Cubells-Beltran, María-Dolores; Muñoz, Diego Ramírez

    2009-01-01

    The 2007 Nobel Prize in Physics can be understood as a global recognition to the rapid development of the Giant Magnetoresistance (GMR), from both the physics and engineering points of view. Behind the utilization of GMR structures as read heads for massive storage magnetic hard disks, important applications as solid state magnetic sensors have emerged. Low cost, compatibility with standard CMOS technologies and high sensitivity are common advantages of these sensors. This way, they have been successfully applied in a lot different environments. In this work, we are trying to collect the Spanish contributions to the progress of the research related to the GMR based sensors covering, among other subjects, the applications, the sensor design, the modelling and the electronic interfaces, focusing on electrical current sensing applications. PMID:22408486

  15. Low field anisotropic colossal magnetoresistance in Sm0.53Sr0.47MnO3 thin films

    NASA Astrophysics Data System (ADS)

    Srivastava, Manoj K.; Singh, M. P.; Kaur, Amarjeet; Razavi, F. S.; Singh, H. K.

    2011-12-01

    Sm0.53Sr0.47MnO3 (SSMO) thin films (thicknesses ˜200 nm) were deposited by on-axis dc magnetron sputtering on the single crystal LSAT (001) substrates. These films are oriented along the out of plane c-direction. The ferromagnetic and insulator-metal transition occurs at TC ˜ 96 and TIM ˜ 91 K, respectively. The magnetization easy axis is observed to lie in the plane of the film while the magnetic hard axis is found to be along the normal to this. The magnetotransport of the SSMO films, which was measured as a function of angle (θ) between the magnetic field (H) and plane of the film, shows colossal anisotropy. Magnetoresistance (MR) decreases drastically as θ increases from 0° (H//easy axis) to 90° (H//hard axis). The out-of-plane anisotropic MR is as high as 88% at H = 3.6 kOe and 78 K. The colossal anisotropy has been explained in terms of the magnetic anisotropies at play and the magnetic domain motion in applied magnetic field.

  16. Nanoparticle-Structured Highly Sensitive and Anisotropic Gauge Sensors.

    PubMed

    Zhao, Wei; Luo, Jin; Shan, Shiyao; Lombardi, Jack P; Xu, Yvonne; Cartwright, Kelly; Lu, Susan; Poliks, Mark; Zhong, Chuan-Jian

    2015-09-16

    The ability to tune gauge factors in terms of magnitude and orientation is important for wearable and conformal electronics. Herein, a sensor device is described which is fabricated by assembling and printing molecularly linked thin films of gold nanoparticles on flexible microelectrodes with unusually high and anisotropic gauge factors. A sharp difference in gauge factors up to two to three orders of magnitude between bending perpendicular (B(⊥)) and parallel (B(||)) to the current flow directions is observed. The origin of the unusual high and anisotropic gauge factors is analyzed in terms of nanoparticle size, interparticle spacing, interparticle structure, and other parameters, and by considering the theoretical aspects of electron conduction mechanism and percolation pathway. A critical range of resistivity where a very small change in strain and the strain orientation is identified to impact the percolation pathway in a significant way, leading to the high and anisotropic gauge factors. The gauge anisotropy stems from molecular and nanoscale fine tuning of interparticle properties of molecularly linked nanoparticle assembly on flexible microelectrodes, which has important implication for the design of gauge sensors for highly sensitive detection of deformation in complex sensing environment or on complex curved surfaces such as wearable electronics and skin sensors. PMID:26037089

  17. Development of a Magneto-Resistive Angular Position Sensor for Space Mechanisms

    NASA Technical Reports Server (NTRS)

    Hahn, Robert; Schmidt, Tilo; Seifart, Klaus; Olberts, Bastian; Romera, Fernando

    2016-01-01

    Magnetic microsystems in the form of magneto-resistive (MR) sensors are firmly established in automobiles and industrial applications. They are used to measure travel, angle, electrical current, or magnetic fields. MR technology opens up new sensor possibilities in space applications and can be an enabling technology for optimal performance, high robustness and long lifetime at reasonable costs. In some science missions, the technology is already applied, however, the designs are proprietary and case specific, for instance in case of the angular sensors used for JPL/NASA's Mars rover Curiosity [1]. Since 2013 HTS GmbH and Sensitec GmbH have teamed up to develop and qualify a standardized yet flexible to use MR angular sensor for space mechanisms. Starting with a first assessment study and market survey performed under ESA contract, a very strong industry interest in novel, contactless position measurement means was found. Currently a detailed and comprehensive development program is being performed by HTS and Sensitec. The objective of this program is to advance the sensor design up to Engineering Qualification Model level and to perform qualification testing for a representative space application. The paper briefly reviews the basics of magneto-resistive effects and possible sensor applications and describes the key benefits of MR angular sensors with reference to currently operational industrial and space applications. The key applications and specification are presented and the preliminary baseline mechanical and electrical design will be discussed. An outlook on the upcoming development and test stages as well as the qualification program will be provided.

  18. Report on demonstration project: imaging detection of unexploded ordinance using giant magnetoresistive sensor arrays

    SciTech Connect

    Chaiken, A., LLNL

    1996-09-01

    The goal of the project was to demonstrate the feasibility of the detection of buried unexploded ordnance (UXO) using giant magnetoresistive (GMR) sensor arrays. 3x3 and 5x5 arrays of off-the-shelf GMR sensors were purchased from Nonvolatile Electronics (NVE) and were interfaced with a data acquisition card and a personal computer. Magnetic images were obtained from a number of ferrous objects, such as threadstock, bolts, and rebar. These images can be interpreted in terms of the remanent magnetic state of the objects. The ability of the GMR sensor approach to discriminate among magnetic objects is assessed and the design of a more realistic UXO detection system is discussed.

  19. Self-sensing atomic force microscopy cantilevers based on tunnel magnetoresistance sensors

    NASA Astrophysics Data System (ADS)

    Tavassolizadeh, Ali; Meier, Tobias; Rott, Karsten; Reiss, Günter; Quandt, Eckhard; Hölscher, Hendrik; Meyners, Dirk

    2013-04-01

    Here, we introduce self-sensing cantilevers for atomic force microscopy (AFM) based on tunnel magnetoresistance (TMR) sensors. These TMR sensors are integrated into the AFM cantilevers and consist of a magnetically stable layer and a sensing magnetostrictive CoFeB layer separated by a MgO tunneling barrier and can be as small as 10 μm × 10 μm. Their TMR values and resistance-area products are about 121% and 61 kΩμm2, respectively. A comparison of AFM data simultaneously obtained with a self-sensing cantilever with a 37 μm × 37 μm large TMR sensor and the conventional optical beam deflection method revealed the same data quality.

  20. Exchange Bias Tuning for Magnetoresistive Sensors by Inclusion of Non-Magnetic Impurities

    PubMed Central

    Sharma, Parikshit Pratim; Albisetti, Edoardo; Monticelli, Marco; Bertacco, Riccardo; Petti, Daniela

    2016-01-01

    The fine control of the exchange coupling strength and blocking temperature ofexchange bias systems is an important requirement for the development of magnetoresistive sensors with two pinned electrodes. In this paper, we successfully tune these parameters in top- and bottom-pinned systems, comprising 5 nm thick Co40Fe40B20 and 6.5 nm thick Ir22Mn78 films. By inserting Ru impurities at different concentrations in the Ir22Mn78 layer, blocking temperatures ranging from 220 °C to 100 °C and exchange bias fields from 200 Oe to 60 Oe are obtained. This method is then applied to the fabrication of sensors based on magnetic tunneling junctions consisting of a pinned synthetic antiferromagnet reference layer and a top-pinned sensing layer. This work paves the way towards the development of new sensors with finely tuned magnetic anisotropies. PMID:27384565

  1. Exchange Bias Tuning for Magnetoresistive Sensors by Inclusion of Non-Magnetic Impurities.

    PubMed

    Sharma, Parikshit Pratim; Albisetti, Edoardo; Monticelli, Marco; Bertacco, Riccardo; Petti, Daniela

    2016-01-01

    The fine control of the exchange coupling strength and blocking temperature ofexchange bias systems is an important requirement for the development of magnetoresistive sensors with two pinned electrodes. In this paper, we successfully tune these parameters in top- and bottom-pinned systems, comprising 5 nm thick Co40Fe40B20 and 6.5 nm thick Ir22Mn78 films. By inserting Ru impurities at different concentrations in the Ir22Mn78 layer, blocking temperatures ranging from 220 °C to 100 °C and exchange bias fields from 200 Oe to 60 Oe are obtained. This method is then applied to the fabrication of sensors based on magnetic tunneling junctions consisting of a pinned synthetic antiferromagnet reference layer and a top-pinned sensing layer. This work paves the way towards the development of new sensors with finely tuned magnetic anisotropies. PMID:27384565

  2. Magnetoresistive sensors for angle, position, and electrical current measurement in demanding environments

    NASA Astrophysics Data System (ADS)

    Doms, Marco; Slatter, Rolf

    2014-06-01

    Nowadays, magnetoresistive (MR) sensors are used in a wide range of applications. In general, the MR-effect describes the change of the electrical resistance in an external magnetic field. MR sensors are not only used for measuring magnetic fields and rotational or linear motion, but also for non-contact switching applications and furthermore for highly dynamic current measurement. This is largely the result of increasingly complex demands on the sensors for e.g. high performance electrical drives. The sensors must not only be accurate and dynamic, but must also be robust under difficult operating conditions and exhibit very high reliability. Due to their physical working principle and their small size, MR sensors are especially suited to work in harsh environments like high or low temperature, radiation, pressure or mechanical shock. This paper describes the principle of operation, manufacturing process and benefits of MR sensors. This will be followed by a description of practical application examples from the automotive, oil and gas, renewable energy and space fields, where MR sensors are successfully applied in very small envelopes at very low /very high temperatures, under high pressure, high mechanical loading and under strong radiation.

  3. Apparatus and method for imaging metallic objects using an array of giant magnetoresistive sensors

    DOEpatents

    Chaiken, Alison

    2000-01-01

    A portable, low-power, metallic object detector and method for providing an image of a detected metallic object. In one embodiment, the present portable low-power metallic object detector an array of giant magnetoresistive (GMR) sensors. The array of GMR sensors is adapted for detecting the presence of and compiling image data of a metallic object. In the embodiment, the array of GMR sensors is arranged in a checkerboard configuration such that axes of sensitivity of alternate GMR sensors are orthogonally oriented. An electronics portion is coupled to the array of GMR sensors. The electronics portion is adapted to receive and process the image data of the metallic object compiled by the array of GMR sensors. The embodiment also includes a display unit which is coupled to the electronics portion. The display unit is adapted to display a graphical representation of the metallic object detected by the array of GMR sensors. In so doing, a graphical representation of the detected metallic object is provided.

  4. Fabrication of micro accelerometer and magnetoresistive sensor directly on a ceramic substrate

    NASA Astrophysics Data System (ADS)

    Aoyagi, Seiji

    2012-06-01

    Micro-electro-mechanical systems (MEMS) sensors have movable parts: thus, it is difficult to handle them at fabrication because of the possibility of fracture. If a MEMS sensor could be fabricated not only on a silicon substrate but also on a ceramic substrate, which can be used for a package of the end product, the above-mentioned problem about handling would be solved, and its fabrication cost would be reduced. In this presentation, as demonstrations of the sensors directly fabricated on a ceramic package, an accelerometer and a magnetoresistive (MR) sensor are focused on. A micro accelerometer is proposed, which consists of a proof mass and ferroelectric substrate under it. A screen-printed barium titanate (BTO) film on an alumina substrate was employed as ferroelectrics. The sensitivity of the fabricated accelerometer was 0.1 pF g‑1. A triaxis MR sensor is proposed, which detects not only x- and y-axes' magnetic field intensities but also that of the z-axis. Namely, not only azimuth but also angle of elevation of the sensor can be detected from triaxis components of the geomagnetic field. A permalloy (FeNi) plate is stood aside from the MR element. The plate distorts magnetic field and generates the x- (or y-) component from the originally z-directional field. A triaxis geomagnetic field was successfully detected by the fabricated sensor.

  5. Anisotropic magnetoresistance of epitaxial Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3} film

    SciTech Connect

    Chen, X. G.; Yang, Y. B.; Wang, C. S.; Liu, S. Q.; Zhang, Y.; Han, J. Z.; Yang, Y. C.; Yang, J. B.

    2014-01-28

    The magnetic field and temperature dependent anisotropic magnetoresistance (AMR) of the epitaxial grown Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3} thin films was investigated. It was found that the magnetoresistance exhibited the characteristics of magnetic polaron hopping. A two-fold symmetric AMR occurred in the ferromagnetic region (∼220 K < T < ∼150 K), while a four-fold symmetric AMR appeared under a high magnetic field in the antiferromagnetic orbital ordered region (T < ∼150 K). The angular dependence of the resistance showed a hysteresis effect under magnetic field at low temperature. It is believed that these phenomena are attributed to the spin canting effect, which originates from the melting of orbital ordering under the external magnetic field in the antiferromagnetic region.

  6. Giant Magnetoresistance Sensors: A Review on Structures and Non-Destructive Eddy Current Testing Applications

    PubMed Central

    Rifai, Damhuji; Abdalla, Ahmed N.; Ali, Kharudin; Razali, Ramdan

    2016-01-01

    Non-destructive eddy current testing (ECT) is widely used to examine structural defects in ferromagnetic pipe in the oil and gas industry. Implementation of giant magnetoresistance (GMR) sensors as magnetic field sensors to detect the changes of magnetic field continuity have increased the sensitivity of eddy current techniques in detecting the material defect profile. However, not many researchers have described in detail the structure and issues of GMR sensors and their application in eddy current techniques for nondestructive testing. This paper will describe the implementation of GMR sensors in non-destructive testing eddy current testing. The first part of this paper will describe the structure and principles of GMR sensors. The second part outlines the principles and types of eddy current testing probe that have been studied and developed by previous researchers. The influence of various parameters on the GMR measurement and a factor affecting in eddy current testing will be described in detail in the third part of this paper. Finally, this paper will discuss the limitations of coil probe and compensation techniques that researchers have applied in eddy current testing probes. A comprehensive review of previous studies on the application of GMR sensors in non-destructive eddy current testing also be given at the end of this paper. PMID:26927123

  7. Giant Magnetoresistance Sensors: A Review on Structures and Non-Destructive Eddy Current Testing Applications.

    PubMed

    Rifai, Damhuji; Abdalla, Ahmed N; Ali, Kharudin; Razali, Ramdan

    2016-01-01

    Non-destructive eddy current testing (ECT) is widely used to examine structural defects in ferromagnetic pipe in the oil and gas industry. Implementation of giant magnetoresistance (GMR) sensors as magnetic field sensors to detect the changes of magnetic field continuity have increased the sensitivity of eddy current techniques in detecting the material defect profile. However, not many researchers have described in detail the structure and issues of GMR sensors and their application in eddy current techniques for nondestructive testing. This paper will describe the implementation of GMR sensors in non-destructive testing eddy current testing. The first part of this paper will describe the structure and principles of GMR sensors. The second part outlines the principles and types of eddy current testing probe that have been studied and developed by previous researchers. The influence of various parameters on the GMR measurement and a factor affecting in eddy current testing will be described in detail in the third part of this paper. Finally, this paper will discuss the limitations of coil probe and compensation techniques that researchers have applied in eddy current testing probes. A comprehensive review of previous studies on the application of GMR sensors in non-destructive eddy current testing also be given at the end of this paper. PMID:26927123

  8. An efficient biosensor made of an electromagnetic trap and a magneto-resistive sensor.

    PubMed

    Li, Fuquan; Kosel, Jürgen

    2014-09-15

    Magneto-resistive biosensors have been found to be useful because of their high sensitivity, low cost, small size, and direct electrical output. They use super-paramagnetic beads to label a biological target and detect it via sensing the stray field. In this paper, we report a new setup for magnetic biosensors, replacing the conventional "sandwich" concept with an electromagnetic trap. We demonstrate the capability of the biosensor in the detection of E. coli. The trap is formed by a current-carrying microwire that attracts the magnetic beads into a sensing space on top of a tunnel magneto-resistive sensor. The sensor signal depends on the number of beads in the sensing space, which depends on the size of the beads. This enables the detection of biological targets, because such targets increase the volume of the beads. Experiments were carried out with a 6 µm wide microwire, which attracted the magnetic beads from a distance of 60 μm, when a current of 30 mA was applied. A sensing space of 30 µm in length and 6 µm in width was defined by the magnetic sensor. The results showed that individual E. coli bacterium inside the sensing space could be detected using super-paramagnetic beads that are 2.8 µm in diameter. The electromagnetic trap setup greatly simplifies the device and reduces the detection process to two steps: (i) mixing the bacteria with magnetic beads and (ii) applying the sample solution to the sensor for measurement, which can be accomplished within about 30 min with a sample volume in the µl range. This setup also ensures that the biosensor can be cleaned easily and re-used immediately. The presented setup is readily integrated on chips via standard microfabrication techniques. PMID:24727202

  9. Fabrication and local laser heating of freestanding Ni{sub 80}Fe{sub 20} bridges with Pt contacts displaying anisotropic magnetoresistance and anomalous Nernst effect

    SciTech Connect

    Brandl, F.; Grundler, D.

    2014-04-28

    In spin caloritronics, ferromagnetic samples subject to relatively large in-plane temperature gradients ∇T have turned out to be extremely interesting. We report on a preparation technique that allows us to create freely suspended permalloy/Pt hybrid structures where a scanning laser induces ∇T on the order of a few K/μm. We observe both the anisotropic magnetoresistance at room temperature and the magnetic field dependent anomalous Nernst effect under laser heating. The technique is promising for the realization of device concepts considered in spin caloritronics based on suspended ferromagnetic nanostructures with electrical contacts.

  10. In-plane tunneling anisotropic magnetoresistance in (Ga,Mn)As/GaAs Esaki diodes in the regime of the excess current

    SciTech Connect

    Shiogai, J.; Ciorga, M. Utz, M.; Schuh, D.; Bougeard, D.; Weiss, D.; Kohda, M.; Nitta, J.; Nojima, T.

    2015-06-29

    We investigate the angular dependence of the tunneling anisotropic magnetoresistance in (Ga,Mn)As/n-GaAs spin Esaki diodes in the regime where the tunneling process is dominated by the excess current through midgap states in (Ga,Mn)As. We compare it to similar measurements performed in the regime of band-to-band tunneling. Whereas the latter show biaxial symmetry typical for magnetic anisotropy observed in (Ga,Mn)As samples, the former is dominated by uniaxial anisotropy along the 〈110〉 axes.

  11. A current sensor based on the giant magnetoresistance effect: design and potential smart grid applications.

    PubMed

    Ouyang, Yong; He, Jinliang; Hu, Jun; Wang, Shan X

    2012-01-01

    Advanced sensing and measurement techniques are key technologies to realize a smart grid. The giant magnetoresistance (GMR) effect has revolutionized the fields of data storage and magnetic measurement. In this work, a design of a GMR current sensor based on a commercial analog GMR chip for applications in a smart grid is presented and discussed. Static, dynamic and thermal properties of the sensor were characterized. The characterizations showed that in the operation range from 0 to ±5 A, the sensor had a sensitivity of 28 mV·A(-1), linearity of 99.97%, maximum deviation of 2.717%, frequency response of −1.5 dB at 10 kHz current measurement, and maximum change of the amplitude response of 0.0335%·°C(-1) with thermal compensation. In the distributed real-time measurement and monitoring of a smart grid system, the GMR current sensor shows excellent performance and is cost effective, making it suitable for applications such as steady-state and transient-state monitoring. With the advantages of having a high sensitivity, high linearity, small volume, low cost, and simple structure, the GMR current sensor is promising for the measurement and monitoring of smart grids. PMID:23202221

  12. A Current Sensor Based on the Giant Magnetoresistance Effect: Design and Potential Smart Grid Applications

    PubMed Central

    Ouyang, Yong; He, Jinliang; Hu, Jun; Wang, Shan X.

    2012-01-01

    Advanced sensing and measurement techniques are key technologies to realize a smart grid. The giant magnetoresistance (GMR) effect has revolutionized the fields of data storage and magnetic measurement. In this work, a design of a GMR current sensor based on a commercial analog GMR chip for applications in a smart grid is presented and discussed. Static, dynamic and thermal properties of the sensor were characterized. The characterizations showed that in the operation range from 0 to ±5 A, the sensor had a sensitivity of 28 mV·A−1, linearity of 99.97%, maximum deviation of 2.717%, frequency response of −1.5 dB at 10 kHz current measurement, and maximum change of the amplitude response of 0.0335%·°C−1 with thermal compensation. In the distributed real-time measurement and monitoring of a smart grid system, the GMR current sensor shows excellent performance and is cost effective, making it suitable for applications such as steady-state and transient-state monitoring. With the advantages of having a high sensitivity, high linearity, small volume, low cost, and simple structure, the GMR current sensor is promising for the measurement and monitoring of smart grids. PMID:23202221

  13. Investigation of contactless detection using a giant magnetoresistance sensor for detecting prostate specific antigen.

    PubMed

    Sun, Xuecheng; Zhi, Shaotao; Lei, Chong; Zhou, Yong

    2016-08-01

    This paper presents a contactless detection method for detecting prostate specific antigen with a giant magnetoresistance sensor. In contactless detection case, the prostate specific antigen sample preparation was separated from the sensor that prevented the sensor from being immersed in chemical solvents, and made the sensor implementing in immediately reuse without wash. Experimental results showed that applied an external magnetic field in a range of 50 Oe to 90 Oe, Dynabeads with a concentration as low as 0.1 μg/mL can be detected by this system and could give an approximate quantitation to the logarithmic of Dynabeads concentration. Sandwich immunoassay was employed for preparing PSA samples. The PSA capture was implemented on a gold film modified with a self-assembled monolayer and using biotinylated secondary antibody against PSA and streptavidinylated Dynabeads. With DC magnetic field in the range of 50 to 90 Oe, PSA can be detected with a detection limit as low as 0.1 ng/mL. Samples spiked with different concentrations of PSA can be distinguished clearly. Due to the contactless detection method, the detection system exhibited advantages such as convenient manipulation, reusable, inexpensive, small weight. So, this detection method was a promising candidate in biomarker detection, especially in point of care detection. PMID:27379844

  14. Magnetoresistance sensitivity mapping of the localized response of contiguous and lead-overlaid sensors

    NASA Astrophysics Data System (ADS)

    Sankar, Sandra

    2003-06-01

    Magnetoresistance sensitivity mapping (MSM) was used to investigate the local response of magnetic recording sensors without convolution of the writer, magnetic media and data channel. From a 2D map of the local sensor response, the intrinsic pulse shape and magnetic track profile are readily obtained. Pulse-width is a concern for high data rate since if pulse-width is too broad, individual transitions become difficult to distinguish. Track profiles are important because due to the small difference between magnetic write-width and magnetic read-width, side reading will lead to an increase in noise. Three experiments are discussed: the dependence of the pulse-width (PW50) of the standard contiguous junction (CJ) design on shield-to-shield spacing; a comparison of the pulse shape of lead-overlaid (LOL) and CJ designs; and a comparison of the magnetic track profile (including track-width and skirt ratio) of LOL and CJ designs. The LOL design offers an increased sensitivity; however, as seen from MSM, the penalties are broadening of the track and pulse profiles. These are a direct result of the finite current in the lead overlay region and an increased shield-to-shield spacing in that region. The MSM image shows a curvature, which is associated with the topography of the top shield due to the lead overlay.

  15. A Non-Invasive Thermal Drift Compensation Technique Applied to a Spin-Valve Magnetoresistive Current Sensor

    PubMed Central

    Moreno, Jaime Sánchez; Muñoz, Diego Ramírez; Cardoso, Susana; Berga, Silvia Casans; Antón, Asunción Edith Navarro; de Freitas, Paulo Jorge Peixeiro

    2011-01-01

    A compensation method for the sensitivity drift of a magnetoresistive (MR) Wheatstone bridge current sensor is proposed. The technique was carried out by placing a ruthenium temperature sensor and the MR sensor to be compensated inside a generalized impedance converter circuit (GIC). No internal modification of the sensor bridge arms is required so that the circuit is capable of compensating practical industrial sensors. The method is based on the temperature modulation of the current supplied to the bridge, which improves previous solutions based on constant current compensation. Experimental results are shown using a microfabricated spin-valve MR current sensor. The temperature compensation has been solved in the interval from 0 °C to 70 °C measuring currents from −10 A to +10 A. PMID:22163748

  16. Anisotropic magnetoresistance of individual CoFeB and Ni nanotubes with values of up to 1.4% at room temperature

    NASA Astrophysics Data System (ADS)

    Rüffer, Daniel; Slot, Marlou; Huber, Rupert; Schwarze, Thomas; Heimbach, Florian; Tütüncüoglu, Gözde; Matteini, Federico; Russo-Averchi, Eleonora; Kovács, András; Dunin-Borkowski, Rafal; Zamani, Reza R.; Morante, Joan R.; Arbiol, Jordi; Fontcuberta i Morral, Anna; Grundler, Dirk

    2014-07-01

    Magnetic nanotubes (NTs) are interesting for magnetic memory and magnonic applications. We report magnetotransport experiments on individual 10 to 20 μm long Ni and CoFeB NTs with outer diameters ranging from 160 to 390 nm and film thicknesses of 20 to 40 nm. The anisotropic magnetoresistance (AMR) effect studied from 2 K to room temperature (RT) amounted to 1.4% and 0.1% for Ni and CoFeB NTs, respectively, at RT. We evaluated magnetometric demagnetization factors of about 0.7 for Ni and CoFeB NTs having considerably different saturation magnetization. The relatively large AMR value of the Ni nanotubes is promising for RT spintronic applications. The large saturation magnetization of CoFeB is useful in different fields such as magnonics and scanning probe microscopy using nanotubes as magnetic tips.

  17. Tunneling anisotropic magnetoresistance in La2/3Sr1/3MnO3/LaAlO3/Pt tunnel junctions

    NASA Astrophysics Data System (ADS)

    Galceran, R.; Balcells, Ll.; Pomar, A.; Konstantinović, Z.; Bagués, N.; Sandiumenge, F.; Martínez, B.

    2016-04-01

    The magnetotransport properties of La2/3Sr1/3MnO3(LSMO)/ LaAlO3(LAO)/Pt tunneling junctions have been analyzed as a function of temperature and magnetic field. The junctions exhibit magnetoresistance (MR) values of about 37%, at H=90 kOe at low temperature. However, the temperature dependence of MR indicates a clear distinct origin than that of conventional colossal MR. In addition, tunneling anisotropic MR (TAMR) values around 4% are found at low temperature and its angular dependence reflects the expected uniaxial anisotropy. The use of TAMR response could be an alternative of much easier technological implementation than conventional MTJs since only one magnetic electrode is required, thus opening the door to the implementation of more versatile devices. However, further studies are required in order to improve the strong temperature dependence at the present stage.

  18. Magnetic properties and anisotropic magnetoresistance of antiperovskite nitride Mn{sub 3}GaN/Co{sub 3}FeN exchange-coupled bilayers

    SciTech Connect

    Sakakibara, H. Ando, H.; Kuroki, Y.; Kawai, S.; Ueda, K.; Asano, H.

    2015-05-07

    Epitaxial bilayers of antiferromagnetic Mn{sub 3}GaN/ferromagnetic Co{sub 3}FeN with an antiperovskite structure were grown by reactive magnetron sputtering, and their structural, magnetic, and electrical properties were investigated. Exchange coupling with an exchange field H{sub ex} of 0.4 kOe at 4 K was observed for Mn{sub 3}GaN (20 nm)/Co{sub 3}FeN (5 nm) bilayers. Negative anisotropic magnetoresistance (AMR) effect in Co{sub 3}FeN was observed and utilized to detect magnetization reversal in exchange-coupled Mn{sub 3}GaN/Co{sub 3}FeN bilayers. The AMR results showed evidence for current-induced spin transfer torque in antiferromagnetic Mn{sub 3}GaN.

  19. The Front-End Readout as an Encoder IC for Magneto-Resistive Linear Scale Sensors.

    PubMed

    Tran, Trong-Hieu; Chao, Paul Chang-Po; Chien, Ping-Chieh

    2016-01-01

    This study proposes a front-end readout circuit as an encoder chip for magneto-resistance (MR) linear scales. A typical MR sensor consists of two major parts: one is its base structure, also called the magnetic scale, which is embedded with multiple grid MR electrodes, while another is an "MR reader" stage with magnets inside and moving on the rails of the base. As the stage is in motion, the magnetic interaction between the moving stage and the base causes the variation of the magneto-resistances of the grid electrodes. In this study, a front-end readout IC chip is successfully designed and realized to acquire temporally-varying resistances in electrical signals as the stage is in motions. The acquired signals are in fact sinusoids and co-sinusoids, which are further deciphered by the front-end readout circuit via newly-designed programmable gain amplifiers (PGAs) and analog-to-digital converters (ADCs). The PGA is particularly designed to amplify the signals up to full dynamic ranges and up to 1 MHz. A 12-bit successive approximation register (SAR) ADC for analog-to-digital conversion is designed with linearity performance of ±1 in the least significant bit (LSB) over the input range of 0.5-2.5 V from peak to peak. The chip was fabricated by the Taiwan Semiconductor Manufacturing Company (TSMC) 0.35-micron complementary metal oxide semiconductor (CMOS) technology for verification with a chip size of 6.61 mm², while the power consumption is 56 mW from a 5-V power supply. The measured integral non-linearity (INL) is -0.79-0.95 LSB while the differential non-linearity (DNL) is -0.68-0.72 LSB. The effective number of bits (ENOB) of the designed ADC is validated as 10.86 for converting the input analog signal to digital counterparts. Experimental validation was conducted. A digital decoder is orchestrated to decipher the harmonic outputs from the ADC via interpolation to the position of the moving stage. It was found that the displacement measurement error is within

  20. Slow Oscillations of In-plane Magnetoresistance in Strongly Anisotropic Quasi-Two-Dimensional Rare-Earth Tritellurides

    NASA Astrophysics Data System (ADS)

    Sinchenko, A. A.; Grigoriev, P. D.; Monceau, P.; Lejay, P.; Zverev, V. N.

    2016-04-01

    The slow oscillations of intralayer magnetoresistance in the quasi-2D metallic compounds TbTe_3 and GdTe_3 have been observed for the first time. These oscillations do not originate from small Fermi-surface pockets, as revealed usually by Shubnikov-de Haas oscillations, but from the entanglement of close frequencies due to a finite interlayer transfer integral t_z , either between the two Te planes forming a bilayer or between two adjacent bilayers, which allows to estimate its values. For TbTe_3 and GdTe_3 , we obtain the estimate t_ z≈ 1 meV.

  1. Giant magnetoresistive sensor array for sensitive and specific multiplexed food allergen detection.

    PubMed

    Ng, Elaine; Nadeau, Kari C; Wang, Shan X

    2016-06-15

    Current common allergen detection methods, including enzyme-linked immunosorbent assays (ELISAs) and dip-stick methods, do not provide adequate levels of sensitivity and specificity for at-risk allergic patients. A method for performing highly sensitive and specific detection of multiple food allergens is thus imperative as food allergies are becoming increasingly recognized as a major healthcare concern, affecting an estimated 4% of the total population. We demonstrate first instance of sensitive and specific multiplexed detection of major peanut allergens Ara h 1 and Ara h 2, and wheat allergen Gliadin using giant magnetoresistive (GMR) sensor arrays. Commercialized ELISA kits for Ara h 1 and Ara h 2 report limits of detection (LODs) at 31.5 ng/mL and 0.2 ng/mL, respectively. In addition, the 96-well-based ELISA developed in-house for Gliadin was found to have a LOD of 40 ng/mL. Our multiplexed GMR-based assay demonstrates the ability to perform all three assays on the same chip specifically and with sensitivities at LODs about an order of magnitude lower than those of 96-well-based ELISAs. LODs of GMR-based assays developed for Ara h 1, Ara h 2, and Gliadin were 7.0 ng/mL, 0.2 ng/mL, and 1.5 ng/mL, respectively, with little to no cross-reactivity. These LODs are clinically important as some patients could react strongly against such low allergen levels. Given the limitations of current industrial detection technology, multiplexed GMR-based assays provide a method for highly sensitive and specific simultaneous detection of any combination of food-product allergens, thus protecting allergic patients from life-threatening events, including anaphylaxis, by unintentional consumption. PMID:26859787

  2. High-resolution imaging with two-axis orthogonal magneto-resistive sensor based eddy current probe

    NASA Astrophysics Data System (ADS)

    Wincheski, Buzz; Simpson, John; Seebo, Jeffery P.; Powell, Jessica

    2012-05-01

    A two-channel magneto-resistive sensor with an embedded, single-strand eddy current inducer has been fabricated and tested for applications including sensory material characterization and the analysis of intermittent contact along compression boundaries and fatigue cracks. A rapid scanning technique has also been implemented to enable high-resolution imaging of relatively large areas in modest times. Applications of the probe for high-resolution imaging of calibration artifacts and sensory materials are presented. Finite element modeling of the probe is also presented and compared with experimental measurements with good agreement.

  3. On the development of a magnetoresistive sensor for blade tip timing and blade tip clearance measurement systems

    NASA Astrophysics Data System (ADS)

    Tomassini, R.; Rossi, G.; Brouckaert, J.-F.

    2014-05-01

    The accurate control of the gap between static and rotating components is vital to preserve the mechanical integrity and ensure a correct functioning of any rotating machinery. Moreover, tip leakage above the airfoil tip results in relevant aerodynamic losses. One way to measure and to monitor blade tip gaps is by the so-called Blade Tip Clearance (BTC) technique. Another fundamental phenomenon to control in the turbomachines is the vibration of the blades. For more than half a century, this has been performed by installing strain gauges on the blades and using telemetry to transmit the signals. The Blade Tip Timing (BTT) technique, (i.e. measuring the blade time of arrival from the casing at different angular locations with proximity sensors) is currently being adopted by all manufacturers as a replacement for the classical strain gauge technique because of its non-intrusive character. This paper presents a novel magnetoresistive sensor for blade tip timing and blade tip clearance systems, which offers high temporal and high spatial resolution simultaneously. The sensing element adopted is a Wheatstone bridge of Permalloy elements. The principle of the sensor is based on the variation of magnetic field at the passage of ferromagnetic objects. Two different configurations have been realized, a digital and an analogue sensor. Measurements of tip clearance have been performed in an high speed compressor and the calibration curve is reported. Measurements of blade vibration have been carried out in a dedicated calibration bench; results are presented and discussed. The magnetoresistive sensor is characterized by high repeatability, low manufacturing costs and measurement accuracy in line with the main probes used in turbomachinery testing. The novel sensor has great potential and is capable of fulfilling the requirements for a simultaneous BTC and BTT measurement system.

  4. Angle dependence on the anisotropic magnetoresistance amplitude of a single-contacted Ni nanowire subjected to a thermo-mechanical strain

    NASA Astrophysics Data System (ADS)

    Melilli, G.; Madon, B.; Wegrowe, J.-E.; Clochard, M.-C.

    2015-12-01

    The effects of thermoelastic and piezoelectric strain of an active track-etched β-PVDF polymer matrix on an electrodeposited single-contacted Ni nanowire (NW) are investigated at the nanoscale by measuring the change of magnetization (i.e. using the inverse magnetostriction effect). The magnetization state is measured locally by anisotropic magnetoresistance (AMR). The ferromagnetic NW plays thus the role of a mechanical probe that allows the effects of mechanical strain to be characterized and described qualitatively and quantitatively. The inverse magnetostriction was found to be responsible for a quasi-disappearance of the AMR signal for a variation of the order of ΔT ≈ 10 K. In other terms, the variation of the magnetization due to the stress compensates the effect of external magnetic field applied on the NW resistance. The induced stress field in a single Ni NW was found 1000 time higher than the bulk stress field (due to thermal expansion measured on the PVDF). This amplification could be attributed to three nanoscopic effects: (1) a stress mismatch between the Ni NW and the membrane, (2) a non-negligible role of the surface tension on Ni NW Young modulus, and (3) the possibility of non-linear stress-strain law. We investigate here the role of these different contributions using track-etched polymer membranes irradiated at various angles (αirrad) leading to, after electrodeposition, embedded Ni NWs of different orientations.

  5. Determination of magnetic anisotropy constants and domain wall pinning energy of Fe/MgO(001) ultrathin film by anisotropic magnetoresistance

    PubMed Central

    Hu, Bo; He, Wei; Ye, Jun; Tang, Jin; Zhang, Yong-Sheng; Ahmad, Syed Sheraz; Zhang, Xiang-Qun; Cheng, Zhao-Hua

    2015-01-01

    It is challenging to determine domain wall pinning energy and magnetic anisotropy since both coherent rotation and domain wall displacement coexist during magnetization switching process. Here, angular dependence anisotropic magnetoresistance (AMR) measurements at different magnetic fields were employed to determine magnetic anisotropy constants and domain wall pinning energy of Fe/MgO(001) ultrathin film. The AMR curves at magnetic fields which are high enough to ensure the coherent rotation of magnetization indicate a smooth behavior without hysteresis between clockwise (CW) and counter-clockwise (CCW) rotations. By analyzing magnetic torque, the magnetic anisotropy constants can be obtained. On the other hand, the AMR curves at low fields show abrupt transitions with hysteresis between CW and CCW rotations, suggesting the presence of multi-domain structures. The domain wall pinning energy can be obtained by analyzing different behaviors of AMR. Our work suggests that AMR measurements can be employed to figure out precisely the contributions of magnetic anisotropy and domain wall pinning energy, which is still a critical issue for spintronics. PMID:26369572

  6. Ultra-Sensitive Magnetoresistive Displacement Sensing Device

    NASA Technical Reports Server (NTRS)

    Olivas, John D. (Inventor); Lairson, Bruce M. (Inventor); Ramesham, Rajeshuni (Inventor)

    2003-01-01

    An ultrasensitive displacement sensing device for use in accelerometers, pressure gauges, temperature transducers, and the like, comprises a sputter deposited, multilayer, magnetoresistive field sensor with a variable electrical resistance based on an imposed magnetic field. The device detects displacement by sensing changes in the local magnetic field about the magnetoresistive field sensor caused by the displacement of a hard magnetic film on a movable microstructure. The microstructure, which may be a cantilever, membrane, bridge, or other microelement, moves under the influence of an acceleration a known displacement predicted by the configuration and materials selected, and the resulting change in the electrical resistance of the MR sensor can be used to calculate the displacement. Using a micromachining approach, very thin silicon and silicon nitride membranes are fabricated in one preferred embodiment by means of anisotropic etching of silicon wafers. Other approaches include reactive ion etching of silicon on insulator (SOI), or Low Pressure Chemical Vapor Deposition of silicon nitride films over silicon substrates. The device is found to be improved with the use of giant magnetoresistive elements to detect changes in the local magnetic field.

  7. A High-Spin Rate Measurement Method for Projectiles Using a Magnetoresistive Sensor Based on Time-Frequency Domain Analysis.

    PubMed

    Shang, Jianyu; Deng, Zhihong; Fu, Mengyin; Wang, Shunting

    2016-01-01

    Traditional artillery guidance can significantly improve the attack accuracy and overall combat efficiency of projectiles, which makes it more adaptable to the information warfare of the future. Obviously, the accurate measurement of artillery spin rate, which has long been regarded as a daunting task, is the basis of precise guidance and control. Magnetoresistive (MR) sensors can be applied to spin rate measurement, especially in the high-spin and high-g projectile launch environment. In this paper, based on the theory of a MR sensor measuring spin rate, the mathematical relationship model between the frequency of MR sensor output and projectile spin rate was established through a fundamental derivation. By analyzing the characteristics of MR sensor output whose frequency varies with time, this paper proposed the Chirp z-Transform (CZT) time-frequency (TF) domain analysis method based on the rolling window of a Blackman window function (BCZT) which can accurately extract the projectile spin rate. To put it into practice, BCZT was applied to measure the spin rate of 155 mm artillery projectile. After extracting the spin rate, the impact that launch rotational angular velocity and aspect angle have on the extraction accuracy of the spin rate was analyzed. Simulation results show that the BCZT TF domain analysis method can effectively and accurately measure the projectile spin rate, especially in a high-spin and high-g projectile launch environment. PMID:27322266

  8. A High-Spin Rate Measurement Method for Projectiles Using a Magnetoresistive Sensor Based on Time-Frequency Domain Analysis

    PubMed Central

    Shang, Jianyu; Deng, Zhihong; Fu, Mengyin; Wang, Shunting

    2016-01-01

    Traditional artillery guidance can significantly improve the attack accuracy and overall combat efficiency of projectiles, which makes it more adaptable to the information warfare of the future. Obviously, the accurate measurement of artillery spin rate, which has long been regarded as a daunting task, is the basis of precise guidance and control. Magnetoresistive (MR) sensors can be applied to spin rate measurement, especially in the high-spin and high-g projectile launch environment. In this paper, based on the theory of a MR sensor measuring spin rate, the mathematical relationship model between the frequency of MR sensor output and projectile spin rate was established through a fundamental derivation. By analyzing the characteristics of MR sensor output whose frequency varies with time, this paper proposed the Chirp z-Transform (CZT) time-frequency (TF) domain analysis method based on the rolling window of a Blackman window function (BCZT) which can accurately extract the projectile spin rate. To put it into practice, BCZT was applied to measure the spin rate of 155 mm artillery projectile. After extracting the spin rate, the impact that launch rotational angular velocity and aspect angle have on the extraction accuracy of the spin rate was analyzed. Simulation results show that the BCZT TF domain analysis method can effectively and accurately measure the projectile spin rate, especially in a high-spin and high-g projectile launch environment. PMID:27322266

  9. Remote sensor response study in the regime of the microwave radiation-induced magnetoresistance oscillations

    SciTech Connect

    Ye, Tianyu; Mani, R. G.; Wegscheider, W.

    2013-11-04

    A concurrent remote sensing and magneto-transport study of the microwave excited two dimensional electron system (2DES) at liquid helium temperatures has been carried out using a carbon detector to remotely sense the microwave activity of the 2D electron system in the GaAs/AlGaAs heterostructure during conventional magneto-transport measurements. Various correlations are observed and reported between the oscillatory magnetotransport and the remotely sensed reflection. In addition, the oscillatory remotely sensed signal is shown to exhibit a power law type variation in its amplitude, similar to the radiation-induced magnetoresistance oscillations.

  10. Tunable three-axis magnetoresistance sensor with a spin-polarised current

    NASA Astrophysics Data System (ADS)

    Chang, Jui-Hang; Chang, Ching-Ray

    2015-10-01

    A three-axis magnetic tunnel junction sensor with three ferromagnetic layers to achieve a linear and hysteresis-free response is proposed and studied analytically. We show that the orientation of the easy axis of the sensor and the sensitivity are tunable by changing the density of a injected spin-polarised current. Additionally, the sensors integrated in a full Wheatstone bridge can have perpendicular and transverse sensing capability in different initial magnetisation arrangements. A value of 0.35% TMR/Oe is observed in sensing the perpendicular field. These findings indicate that a three-axis sensor can be fabricated more easily on a flat substrate.

  11. Plasmonic nanoparticles sensors utilizing hybrid modes, electrical excitation, and anisotropic particles

    NASA Astrophysics Data System (ADS)

    Dathe, Andre; Kliuiev, Pavel; Jatschka, Jacqueline; Hübner, Uwe; Ziegler, Mario; Thiele, Matthias; Trautmann, Steffen; Wirth, Janina; Garwe, Frank; Csaki, Andrea; Stranik, Ondrej; Fritzsche, Wolfgang

    2015-08-01

    Surface Plasmon Resonance (SPR) in metallic nanostructures is an optical effect that can be exploited for the detection of small molecules. There is a broad range of metallic nanostructures supporting different SPR modes, and nanostructures can be even geometrically combined leading to the creation of new hybridised SPR modes. In our study, we investigated the properties of a hybridised SPR mode (gap modes GM) created by the placement of metallic nanoparticles onto metallic layers and its use as a sensitive sensor. A tunneling current passing through a metal-insulator-semiconductor structure can generate supported SPR modes that can be scattered through GM, which was experimentally confirmed. Moreover, we were able to experimentally follow the degradation of anisotropic (silver nanoprism) nanoparticles under ambient conditions in real time. Using atomic force microscopy and optical spectroscopy we observed an anisotropic corrosion that is starting from the tips of the nanoparticles.

  12. Enhanced response and sensitivity of self-corrugated graphene sensors with anisotropic charge distribution

    PubMed Central

    Yol Jeong, Seung; Jeong, Sooyeon; Won Lee, Sang; Tae Kim, Sung; Kim, Daeho; Jin Jeong, Hee; Tark Han, Joong; Baeg, Kang-Jun; Yang, Sunhye; Seok Jeong, Mun; Lee, Geon-Woong

    2015-01-01

    We introduce a high-performance molecular sensor using self-corrugated chemically modified graphene as a three dimensional (3D) structure that indicates anisotropic charge distribution. This is capable of room-temperature operation, and, in particular, exhibiting high sensitivity and reversible fast response with equilibrium region. The morphology consists of periodic, “cratered” arrays that can be formed by condensation and evaporation of graphene oxide (GO) solution on interdigitated electrodes. Subsequent hydrazine reduction, the corrugated edge area of the graphene layers have a high electric potential compared with flat graphene films. This local accumulation of electrons interacts with a large number of gas molecules. The sensitivity of 3D-graphene sensors significantly increases in the atmosphere of NO2 gas. The intriguing structures have several advantages for straightforward fabrication on patterned substrates, high-performance graphene sensors without post-annealing process. PMID:26053892

  13. Enhanced response and sensitivity of self-corrugated graphene sensors with anisotropic charge distribution

    NASA Astrophysics Data System (ADS)

    Yol Jeong, Seung; Jeong, Sooyeon; Won Lee, Sang; Tae Kim, Sung; Kim, Daeho; Jin Jeong, Hee; Tark Han, Joong; Baeg, Kang-Jun; Yang, Sunhye; Seok Jeong, Mun; Lee, Geon-Woong

    2015-06-01

    We introduce a high-performance molecular sensor using self-corrugated chemically modified graphene as a three dimensional (3D) structure that indicates anisotropic charge distribution. This is capable of room-temperature operation, and, in particular, exhibiting high sensitivity and reversible fast response with equilibrium region. The morphology consists of periodic, “cratered” arrays that can be formed by condensation and evaporation of graphene oxide (GO) solution on interdigitated electrodes. Subsequent hydrazine reduction, the corrugated edge area of the graphene layers have a high electric potential compared with flat graphene films. This local accumulation of electrons interacts with a large number of gas molecules. The sensitivity of 3D-graphene sensors significantly increases in the atmosphere of NO2 gas. The intriguing structures have several advantages for straightforward fabrication on patterned substrates, high-performance graphene sensors without post-annealing process.

  14. The Preliminary Study Of Giant Magnetoresistance Sensor For Detection Of Oxygen In Human Blood

    NASA Astrophysics Data System (ADS)

    Ramli, Ramli; Muhtadi, Almas Hilman; Sahdan, Muhammad Fauzi; Haryanto, Freddy; Khairurrijal; Djamal, Mitra

    2010-12-01

    In recent years, there has been great progress for applications of nanomaterials in medicine field. Human body consists of many atoms and they can be treated like as nanomaterials. One of them is oxygen. Oxygen is always found in the human blood. Its concentration in human blood gives information about the metabolism in the body. The purpose of this study was to look for a possibility for developing tool to detect the concentration of oxygen in blood. In this study, the giant-magneto-resistance (GMR) sensor is implemented. The GMR sensor has many attractive features, for example: reduced size, low-power consumption, low price, as compared to other magnetic sensors and its electric and magnetic properties can be varied in very wide range. In this experiment, we developed the structure of GMR materials NiCoFe/Cu/NiCoFe sandwich as a GMR sensor. The NiCoFe/Cu/NiCoFe sandwiches were grown onto Si (111) substrates by the dc-opposed target magnetron sputtering (dc-OTMS) technique. The sputtering targets were NiCoFe and Cu. To achieve the aims of this study, the blood transports in human will be simulated using a simple experimental model. This model has some parameters representing those in blood transport. Furthermore, the nanomagnetic material will be made as a contaminant particle in blood. Using this material some properties of the transport will be investigated.

  15. Pulsed magnetic field measurement system based on colossal magnetoresistance-B-scalar sensors for railgun investigation.

    PubMed

    Stankevič, T; Medišauskas, L; Stankevič, V; Balevičius, S; Żurauskienė, N; Liebfried, O; Schneider, M

    2014-04-01

    A high pulsed magnetic field measurement system based on the use of CMR-B-scalar sensors was developed for the investigations of the electrodynamic processes in electromagnetic launchers. The system consists of four independent modules (channels) which are controlled by a personal computer. Each channel is equipped with a CMR-B-scalar sensor connected to the measurement device-B-scalar meter. The system is able to measure the magnitude of pulsed magnetic fields from 0.3 T to 20 T in the range from DC up to 20 kHz independently of the magnetic field direction. The measurement equipment circuit is electrically separated from the ground and shielded against low and high frequency electromagnetic noise. The B-scalar meters can be operated in the presence of ambient pulsed magnetic fields with amplitudes up to 0.2 T and frequencies higher than 1 kHz. The recorded signals can be transmitted to a personal computer in a distance of 25 m by means of a fiber optic link. The system was tested using the electromagnetic railgun RAFIRA installed at the French-German Research Institute of Saint-Louis, France. PMID:24784635

  16. Magnetoresistance of Bloch-wall-type magnetic structures induced in NiFe/CoSm exchange-spring bilayers

    NASA Astrophysics Data System (ADS)

    Mibu, K.; Nagahama, T.; Shinjo, T.; Ono, T.

    1998-09-01

    The magnetoresistance originating from magnetic structures with gradually rotating magnetic moments, like a Bloch wall, was investigated using soft-magnetic (NiFe)/hard-magnetic (CoSm) bilayers, whose magnetic structures were well characterized. The magnetoresistance was measured with an electric current in the film plane; the magnetoresistance in this geometry corresponds to that due to a current parallel to a Bloch wall. The main feature of the magnetoresistance curves was ruled by the anisotropic magnetoresistance. It was found that a giant magnetoresistance-type effect coexisted; the effect was very small in comparison with the anisotropic magnetoresistance effect.

  17. Magnetoresistive magnetometer for space science applications

    NASA Astrophysics Data System (ADS)

    Brown, P.; Beek, T.; Carr, C.; O'Brien, H.; Cupido, E.; Oddy, T.; Horbury, T. S.

    2012-02-01

    Measurement of the in situ dc magnetic field on space science missions is most commonly achieved using instruments based on fluxgate sensors. Fluxgates are robust, reliable and have considerable space heritage; however, their mass and volume are not optimized for deployment on nano or picosats. We describe a new magnetometer design demonstrating science measurement capability featuring significantly lower mass, volume and to a lesser extent power than a typical fluxgate. The instrument employs a sensor based on anisotropic magnetoresistance (AMR) achieving a noise floor of less than 50 pT Hz-1/2 above 1 Hz on a 5 V bridge bias. The instrument range is scalable up to ±50 000 nT and the three-axis sensor mass and volume are less than 10 g and 10 cm3, respectively. The ability to switch the polarization of the sensor's easy axis and apply magnetic feedback is used to build a driven first harmonic closed loop system featuring improved linearity, gain stability and compensation of the sensor offset. A number of potential geospace applications based on the initial instrument results are discussed including attitude control systems and scientific measurement of waves and structures in the terrestrial magnetosphere. A flight version of the AMR magnetometer will fly on the TRIO-CINEMA mission due to be launched in 2012.

  18. Development of micronic GMR-magnetoresistive sensors for non-destructive sensing applications (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Jaffrès, Henri; LeMaitre, Yves; Collin, Sophie; Nguyen Vandau, Frédéric; Sergeeva-Chollet, Natalia; Decitre, Jean-Marc

    2015-09-01

    We will present our last development of GMR-based magnetic sensors devoted to sensing application for non-destructive control application. In these first realizations, we have chosen a so-called shape anisotropy - exchange biased strategy to fulfill the field-sensing criteria in the μT range in devices made of micronic single elements. Our devices realized by optical lithography, and whose typical sizes range from 150 μm x 150 μm to 500 μm x 500 μm elements, are made of trilayers GMR-based technology and consist of several circuitries of GMR elements of different lengths, widths and gaps. To obtain a full sensing linearity and reversibility requiring a perpendicular magnetic arrangement between both sensitive and hard layer, the magnetization of the latter have been hardened by pinning it with an antiferromagnetic material. The specific geometry of the design have been engineered in order to optimize the magnetic response of the soft layer via the different magnetic torques exerted on it essentially played by the dipolar fields or shape anisotropy, and the external magnetic field to detect. The smaller dimensions in width and in gap are then respectively of 2 μm and 3 μm to benefit of the full shape anisotropy formatting the magnetic response.

  19. Magnetoresistivity and acoustoelectronic effects in a tilted magnetic field in p-Si/SiGe/Si structures with an anisotropic g factor

    SciTech Connect

    Drichko, I. L. Smirnov, I. Yu.; Suslov, A. V.; Mironov, O. A.; Leadley, D. R.

    2010-09-15

    Magnetoresistivity {rho}{sub xx} and {rho}{sub xy} and the acoustoelectronic effects are measured in p-Si/SiGe/Si with an impurity concentration p = 1.99 x 10{sup 11} cm{sup -2} in the temperature range 0.3-2.0 K and an tilted magnetic field up to 18 T. The dependence of the effective g factor on the angle of magnetic field tilt {theta} to the normal to the plane of a two-dimensional p-Si/SiGe/Si channel is determined. A first-order ferromagnet-paramagnet phase transition is observed in the magnetic fields corresponding to a filling factor {nu} = 2 at {theta} {approx} 59{sup o}-60{sup o}.

  20. Evaluation of magnetic flux distribution from magnetic domains in [Co/Pd] nanowires by magnetic domain scope method using contact-scanning of tunneling magnetoresistive sensor

    SciTech Connect

    Okuda, Mitsunobu Miyamoto, Yasuyoshi; Miyashita, Eiichi; Hayashi, Naoto

    2014-05-07

    Current-driven magnetic domain wall motions in magnetic nanowires have attracted great interests for physical studies and engineering applications. The magnetic force microscope (MFM) is widely used for indirect verification of domain locations in nanowires, where relative magnetic force between the local domains and the MFM probe is used for detection. However, there is an occasional problem that the magnetic moments of MFM probe influenced and/or rotated the magnetic states in the low-moment nanowires. To solve this issue, the “magnetic domain scope for wide area with nano-order resolution (nano-MDS)” method has been proposed recently that could detect the magnetic flux distribution from the specimen directly by scanning of tunneling magnetoresistive field sensor. In this study, magnetic domain structure in nanowires was investigated by both MFM and nano-MDS, and the leakage magnetic flux density from the nanowires was measured quantitatively by nano-MDS. Specimen nanowires consisted from [Co (0.3)/Pd (1.2)]{sub 21}/Ru(3) films (units in nm) with perpendicular magnetic anisotropy were fabricated onto Si substrates by dual ion beam sputtering and e-beam lithography. The length and the width of the fabricated nanowires are 20 μm and 150 nm. We have succeeded to obtain not only the remanent domain images with the detection of up and down magnetizations as similar as those by MFM but also magnetic flux density distribution from nanowires directly by nano-MDS. The obtained value of maximum leakage magnetic flux by nano-MDS is in good agreement with that of coercivity by magneto-optical Kerr effect microscopy. By changing the protective diamond-like-carbon film thickness on tunneling magnetoresistive sensor, the three-dimensional spatial distribution of leakage magnetic flux could be evaluated.

  1. Quantum magnetoresistance

    SciTech Connect

    Abrikosov, A.A.

    1998-08-01

    An explanation is proposed of the unusual magnetoresistance, linear in magnetic field and positive, observed recently in nonstoichiometric silver chalcogenides. The idea is based on the assumption that these substances are basically gapless semiconductors with a linear energy spectrum. Most of the excess silver atoms form metallic clusters which are doping the remaining material to a very small carrier concentration, so that even in a magnetic field as low as 10 Oe, only one Landau band participates in the conductivity. {copyright} {ital 1998} {ital The American Physical Society}

  2. Evolution and sign control of square-wave-like anisotropic magneto-resistance in spatially confined La0.3Pr0.4Ca0.3MnO3/LaAlO3(001) manganite thin films

    NASA Astrophysics Data System (ADS)

    Alagoz, H. S.; Jeon, J.; Keating, S.; Chow, K. H.; Jung, J.

    2016-04-01

    We investigated magneto-transport properties of a compressively strained spatially confined La0.3Pr0.4Ca0.3MnO3 (LPCMO) thin film micro-bridge deposited on LaAlO3. Angular dependence of the magneto-resistance R(θ) of this bridge, where θ is the angle between the magnetic field and the current directions in the film plane, exhibits sharp positive and negative percolation jumps near TMIT. The sign and the magnitude of these jumps can be tuned using the magnetic field. Such behavior has not been observed in LPCMO micro-bridges subjected to tensile strain, indicating a correlation between the type of the lattice strain, the distribution of electronic domains, and the anisotropic magneto-resistance in spatially confined manganite systems.

  3. Magnetoresistance of quasi-Bloch-wall induced in NiFe/CoSm exchange-spring bilayers

    NASA Astrophysics Data System (ADS)

    Mibu, K.; Nagahama, T.; Ono, T.; Shinjo, T.

    1998-01-01

    The magnetoresistance (MR) originating from a magnetic structure with continuous rotation of magnetic moments was studied using soft-magnetic/hard-magnetic bilayers. The feature of the MR curves was explained with anisotropic magnetoresistance (AMR) applying to twisted magnetic structures. The giant magnetoresistance (GMR)-type effect was found to be very small compared with the AMR effect.

  4. Monte Carlo calculations of the magnetoresistance in magnetic multilayer structures with giant magnetoresistance effects

    NASA Astrophysics Data System (ADS)

    Prudnikov, V. V.; Prudnikov, P. V.; Romanovskiy, D. E.

    2016-06-01

    A Monte Carlo study of trilayer and spin-valve magnetic structures with giant magnetoresistance effects is carried out. The anisotropic Heisenberg model is used for description of magnetic properties of ultrathin ferromagnetic films forming these structures. The temperature and magnetic field dependences of magnetic characteristics are considered for ferromagnetic and antiferromagnetic configurations of these multilayer structures. The methodology for determination of the magnetoresistance by the Monte Carlo method is introduced; this permits us to calculate the magnetoresistance of multilayer structures for different thicknesses of the ferromagnetic films. The calculated temperature dependence of the magnetoresistance agrees very well with the experimental results measured for the Fe(0 0 1)–Cr(0 0 1) multilayer structure and CFAS–Ag–CFAS–IrMn spin-valve structure based on the half-metallic Heusler alloy Co2FeAl0.5Si0.5.

  5. Simulation of Eddy Current Inspection Including Magnetic Field Sensor such as a Giant Magneto-Resistance Over Planar Stratified Media Components with Embedded Flaws

    NASA Astrophysics Data System (ADS)

    Prémel, Denis; Decitre, J. M.; Pichenot, G.

    2011-06-01

    The ECT inspection of a conductive component consists in detecting the perturbation of the induced currents due to a flaw. Among new detectors, Giant Magneto-Resistance (GMR) or Giant Magnetic Impedance sensors, which are sensitive to the magnetic field above the surface of the component, have shown growing interest due to their high performances with respect to classical bobbin coils. In this communication, we present a numerical model based on the volume integral approach which allows computing the components of the perturbed magnetic field due to a given notch embedded in a planar stratified media. Though the inducer may be chosen arbitrary in a list of potential exciting coils, rectangular coils or current foils are very useful for generating a uniform current flow orientated perpendicularly to the length of the flaw. This paper presents firstly some numerical results considering two kinds of distinct numerical models, and then some experimental results will be presented for different kinds of practical applications. This numerical model results in new computation facilities which have been translated into new functionalities in the last version of the CIVA software.

  6. On-Chip Magnetic Bead Manipulation and Detection Using a Magnetoresistive Sensor-Based Micro-Chip: Design Considerations and Experimental Characterization.

    PubMed

    Gooneratne, Chinthaka P; Kodzius, Rimantas; Li, Fuquan; Foulds, Ian G; Kosel, Jürgen

    2016-01-01

    The remarkable advantages micro-chip platforms offer over cumbersome, time-consuming equipment currently in use for bio-analysis are well documented. In this research, a micro-chip that includes a unique magnetic actuator (MA) for the manipulation of superparamagnetic beads (SPBs), and a magnetoresistive sensor for the detection of SPBs is presented. A design methodology, which takes into account the magnetic volume of SPBs, diffusion and heat transfer phenomena, is presented with the aid of numerical analysis to optimize the parameters of the MA. The MA was employed as a magnetic flux generator and experimental analysis with commercially available COMPEL™ and Dynabeads(®) demonstrated the ability of the MA to precisely transport a small number of SPBs over long distances and concentrate SPBs to a sensing site for detection. Moreover, the velocities of COMPEL™ and Dynabead(®) SPBs were correlated to their magnetic volumes and were in good agreement with numerical model predictions. We found that 2.8 μm Dynabeads(®) travel faster, and can be attracted to a magnetic source from a longer distance, than 6.2 μm COMPEL™ beads at magnetic flux magnitudes of less than 10 mT. The micro-chip system could easily be integrated with electronic circuitry and microfluidic functions, paving the way for an on-chip biomolecule quantification device. PMID:27571084

  7. Magnetoresistive chip cytometer.

    PubMed

    Loureiro, J; Andrade, P Z; Cardoso, S; da Silva, C L; Cabral, J M; Freitas, P P

    2011-07-01

    Although conventional state-of-the-art flow cytometry systems provide rapid and reliable analytical capacities, they are bulky, expensive and complex. To overcome these drawbacks modern flow cytometers have been developed with enhanced portability for on-site measurements. Unlike external fluorescent/optical detectors, magnetoresistive sensors are micro-fabricated, can be integrated within microfluidic channels, and can detect magnetically labelled cells. This work describes the real-time detection of single magnetically labelled cells with a magnetoresistive based cell cytometer. For Kg1-a cells magnetically labelled with 50 nm CD34 microbeads (Milteny) flowing through a 150 μm wide, 14 μm high microchannel, with speeds around 1 cm s(-1), bipolar signals with an average amplitude of 10-20 μV were observed corresponding to cell events. The number of cells counted by the spin valve cytometer has been compared with that obtained with a hemocytometer. Both methods agree within the respective error bars. PMID:21562656

  8. Extraordinary magnetoresistance: sensing the future

    NASA Astrophysics Data System (ADS)

    Hewett, Thomas H.; Kusmartsev, Feodor V.

    2012-06-01

    Simulations utilising the finite element method (FEM) have been produced in order to investigate aspects of circular extraordinary magnetoresistance (EMR) devices. The effect of three specific features on the resultant magnetoresistance were investigated: the ratio of the metallic to semiconducting conductivities ( σ M / σ S ); the semiconductor mobility; and the introduction of an intermediate region at the semiconductormetal interface in order to simulate a contact resistance. In order to obtain a large EMR effect the conductivity ratio ( σ M / σ S ) is required to be larger than two orders of magnitude; below this critical value the resultant magnetoresistance effect is dramatically reduced. Large mobility semiconductors exhibit larger EMR values for a given field (below saturation) and reduce the magnetic field required to produce saturation of the magnetoresistance. This is due to a larger Hall angle produced at a given magnetic field and is consistent with the mechanism of the EMR effect. Since practical magnetic field sensors are required to operate at low magnetic fields, high mobility semiconductors are required in the production of more sensitive EMR sensors. The formation of a Schottky barrier at the semiconductor-metal interface has been modelled with the introduction of a contact resistance at the semiconductor-metal interface. Increasing values of contact resistance are found to reduce the EMR effect with it disappearing altogether for large values. This has been shown explicitly by looking at the current flow in the system and is consistent with the mechanism of the EMR effect. The interface resistance was used to fit the simulated model to existing experimental data. The best fit occurred with an interface with resistivity of 1.55×10-4 m (overestimate). The EMR effect holds great potential with regard to its future application to magnetic field sensors. The design of any such devices should incorporate high mobility materials (such as graphene

  9. Extraordinary magnetoresistance: sensing the future

    NASA Astrophysics Data System (ADS)

    Hewett, Thomas; Kusmartsev, Feodor

    2012-06-01

    Simulations utilising the finite element method (FEM) have been produced in order to investigate aspects of circular extraordinary magnetoresistance (EMR) devices. The effect of three specific features on the resultant magnetoresistance were investigated: the ratio of the metallic to semiconducting conductivities (σ M/σ S); the semiconductor mobility; and the introduction of an intermediate region at the semiconductormetal interface in order to simulate a contact resistance. In order to obtain a large EMR effect the conductivity ratio (σ M/σ S) is required to be larger than two orders of magnitude; below this critical value the resultant magnetoresistance effect is dramatically reduced. Large mobility semiconductors exhibit larger EMR values for a given field (below saturation) and reduce the magnetic field required to produce saturation of the magnetoresistance. This is due to a larger Hall angle produced at a given magnetic field and is consistent with the mechanism of the EMR effect. Since practical magnetic field sensors are required to operate at low magnetic fields, high mobility semiconductors are required in the production of more sensitive EMR sensors. The formation of a Schottky barrier at the semiconductor-metal interface has been modelled with the introduction of a contact resistance at the semiconductor-metal interface. Increasing values of contact resistance are found to reduce the EMR effect with it disappearing altogether for large values. This has been shown explicitly by looking at the current flow in the system and is consistent with the mechanism of the EMR effect. The interface resistance was used to fit the simulated model to existing experimental data. The best fit occurred with an interface with resistivity of 1.55×10-4 m (overestimate). The EMR effect holds great potential with regard to its future application to magnetic field sensors. The design of any such devices should incorporate high mobility materials (such as graphene) along

  10. Strong spin-orbit coupling and Zeeman spin splitting in angle dependent magnetoresistance of Bi{sub 2}Te{sub 3}

    SciTech Connect

    Dey, Rik Pramanik, Tanmoy; Roy, Anupam; Rai, Amritesh; Guchhait, Samaresh; Sonde, Sushant; Movva, Hema C. P.; Register, Leonard F.; Banerjee, Sanjay K.; Colombo, Luigi

    2014-06-02

    We have studied angle dependent magnetoresistance of Bi{sub 2}Te{sub 3} thin film with field up to 9 T over 2–20 K temperatures. The perpendicular field magnetoresistance has been explained by the Hikami-Larkin-Nagaoka theory alone in a system with strong spin-orbit coupling, from which we have estimated the mean free path, the phase coherence length, and the spin-orbit relaxation time. We have obtained the out-of-plane spin-orbit relaxation time to be small and the in-plane spin-orbit relaxation time to be comparable to the momentum relaxation time. The estimation of these charge and spin transport parameters are useful for spintronics applications. For parallel field magnetoresistance, we have confirmed the presence of Zeeman effect which is otherwise suppressed in perpendicular field magnetoresistance due to strong spin-orbit coupling. The parallel field data have been explained using both the contributions from the Maekawa-Fukuyama localization theory for non-interacting electrons and Lee-Ramakrishnan theory of electron-electron interactions. The estimated Zeeman g-factor and the strength of Coulomb screening parameter agree well with the theory. Finally, the anisotropy in magnetoresistance with respect to angle has been described by the Hikami-Larkin-Nagaoka theory. This anisotropy can be used in anisotropic magnetic sensor applications.

  11. Electronic structure basis for the extraordinary magnetoresistance in WTe2.

    PubMed

    Pletikosić, I; Ali, Mazhar N; Fedorov, A V; Cava, R J; Valla, T

    2014-11-21

    The electronic structure basis of the extremely large magnetoresistance in layered nonmagnetic tungsten ditelluride has been investigated by angle-resolved photoelectron spectroscopy. Hole and electron pockets of approximately the same size were found at low temperatures, suggesting that carrier compensation should be considered the primary source of the effect. The material exhibits a highly anisotropic Fermi surface from which the pronounced anisotropy of the magnetoresistance follows. A change in the Fermi surface with temperature was found and a high-density-of-states band that may take over conduction at higher temperatures and cause the observed turn-on behavior of the magnetoresistance in WTe2 was identified. PMID:25479512

  12. Electronic Structure Basis for the Extraordinary Magnetoresistance in WTe2

    NASA Astrophysics Data System (ADS)

    Pletikosić, I.; Ali, Mazhar N.; Fedorov, A. V.; Cava, R. J.; Valla, T.

    2014-11-01

    The electronic structure basis of the extremely large magnetoresistance in layered nonmagnetic tungsten ditelluride has been investigated by angle-resolved photoelectron spectroscopy. Hole and electron pockets of approximately the same size were found at low temperatures, suggesting that carrier compensation should be considered the primary source of the effect. The material exhibits a highly anisotropic Fermi surface from which the pronounced anisotropy of the magnetoresistance follows. A change in the Fermi surface with temperature was found and a high-density-of-states band that may take over conduction at higher temperatures and cause the observed turn-on behavior of the magnetoresistance in WTe2 was identified.

  13. Giant Coulomb blockade magnetoresistance

    SciTech Connect

    Zhang, Xiaoguang; Wen, Z. C.; Wei, H. X.; Han, Prof. X. F.

    2010-01-01

    We show that the Coulomb blockade voltage can be made to depend strongly on the electron spin in a thin magnetic granular layer inserted in the middle of an insulating layer of a tunnel junction. This strong spin dependence is predicted from the spin-dependent inter-granular conductance through any of the following effects within the granular layer, giant magnetoresistance (GMR), tunneling magnetoresistance (TMR), colossal magnetoresistance (CMR), or GMR through a polymer spacer. The resulting Coulomb blockade magnetoresistance (CBMR) ratio can exceed the magnetoresistance ratio of the granular layer itself by orders of magnitude. Unlike other magenetoresistance effects, the CBMR effect does not require magnetic electrodes.

  14. Anisotropic magnetoresistance in the organic superconductor {beta}{sup {double_prime}}-(BEDT-TTF){sub 2}SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3}

    SciTech Connect

    Su, X.; Zuo, F.; Schlueter, J.A.; Williams, J.M.; Nixon, P.G.; Winter, R.W.; Gard, G.L.

    1999-02-01

    In this paper, we report transport measurements of interlayer magnetoresistance with field parallel and perpendicular to the current direction in an all organic superconductor {beta}{sup {double_prime}}-(BEDT-TTF){sub 2}SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3}. For H{parallel}I, the isothermal magnetoresistance R(H) at low temperatures (T{le}T{sub c}) displays a peak effect as a function of field. For H{perpendicular}I, R(H) increases monotonically with increasing field. The results are very analogous to the interlayer magnetoresistance in {kappa}-(BEDT-TTF){sub 2}X compounds. The observation of the peak effect or negative magnetoresistance in different systems for H{parallel}I{perpendicular} plane suggests that it is intrinsic to the layered organic superconductors. For H{perpendicular}I, the large positive magnetoresistance is in a general agreement with a two band model for charge transport. {copyright} {ital 1999} {ital The American Physical Society}

  15. OPTICAL FIBRES AND FIBREOPTIC SENSORS: Polarisation reflectometry of anisotropic optical fibres

    NASA Astrophysics Data System (ADS)

    Konstantinov, Yurii A.; Kryukov, Igor'I.; Pervadchuk, Vladimir P.; Toroshin, Andrei Yu

    2009-11-01

    Anisotropic, polarisation-maintaining fibres have been studied using a reflectometer and integrated optic polariser. Linearly polarised pulses were launched into the fibre under test at different angles between their plane of polarisation and the main optical axis of the fibre. A special procedure for the correlation analysis of these reflectograms is developed to enhance the reliability of the information about the longitudinal optical uniformity ofanisotropic fibres.

  16. Study of anisotropic magnetoresistance in the thermodynamic fluctuation regime of single crystals of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x}

    SciTech Connect

    Heine, G.; Lang, W. |; Wang, Xiao-Lin

    1996-11-01

    Measurements of the in-plane and out-of-plane magnetoresistance in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x} single crystals with a critical temperature T{sub c} = 93 K are reported for temperatures between T{sub c} and 200 K and in magnetic fields up to 13 T. Both the transverse and the longitudinal in-plane magnetoresistance are positive and originate entirely from the suppression of superconducting fluctuations by the magnetic field. The longitudinal out-of-plane magnetoresistance is negative at all temperatures and magnetic fields. As possible origins two recent models are discussed, the reduction of the quasiparticle density of states due to condensation into superconducting fluctuations and thermally activated transport over an interplane pseudogap.

  17. An in-depth noise model for giant magnetoresistance current sensors for circuit design and complementary metal–oxide–semiconductor integration

    SciTech Connect

    Roldán, A. Roldán, J. B.; Reig, C.; Cardoso, S.; Cardoso, F.; Ferreira, R.; Freitas, P. P.

    2014-05-07

    Full instrumentation bridges based on spin valve of giant magnetoresistance and magnetic tunnel junction devices have been microfabricated and experimentally characterized from the DC and noise viewpoint. A more realistic model of these devices was obtained in this work, an electrical and thermal model previously developed have been improved in such a way that noise effects are also included. We have implemented the model in a circuit simulator and reproduced the experimental measurements accurately. This provides a more realistic and complete tool for circuit design where magnetoresistive elements are combined with well-known complementary metal–oxide–semiconductor modules.

  18. An in-depth noise model for giant magnetoresistance current sensors for circuit design and complementary metal-oxide-semiconductor integration

    NASA Astrophysics Data System (ADS)

    Roldán, A.; Roldán, J. B.; Reig, C.; Cardoso, S.; Cardoso, F.; Ferreira, R.; Freitas, P. P.

    2014-05-01

    Full instrumentation bridges based on spin valve of giant magnetoresistance and magnetic tunnel junction devices have been microfabricated and experimentally characterized from the DC and noise viewpoint. A more realistic model of these devices was obtained in this work, an electrical and thermal model previously developed have been improved in such a way that noise effects are also included. We have implemented the model in a circuit simulator and reproduced the experimental measurements accurately. This provides a more realistic and complete tool for circuit design where magnetoresistive elements are combined with well-known complementary metal-oxide-semiconductor modules.

  19. Magnetoresistance in nanostructured Tb/Ti and Tb/Si multilayers

    SciTech Connect

    Svalov, A. V.; Kurlyandskaya, G. V.; Vas'kovskiy, V. O.; Sorokin, A. N.; Diercks, D.

    2011-01-15

    Magnetic, magnetoresistive and structural properties were studied for [Tb/Ti]{sub n} and [Tb/Si]{sub n} multilayers which were prepared by rf-sputtering. The thickness of the Tb layers varied from 1.5 to 12 nm. The thickness of 2 nm nonmagnetic spacers of Ti or Si was kept constant. Both anisotropic and isotropic magnetoresistance was observed in [Tb/Ti]{sub n} and [Tb/Si]{sub n} multilayers. A decrease in the thickness of the terbium layers led to a decrease in the anisotropic contribution to the total magnetoresistance. The negative isotropic magnetoresistanse in [Tb/Ti]{sub n} and [Tb/Si]{sub n} multilayers can be attributed to the giant magnetoresistance (GMR) and/or high field isotropic magnetoresistance. The structure of the samples of both types enabled the existence of the GMR effect.

  20. Magnetoresistance of single Permalloy circular rings

    NASA Astrophysics Data System (ADS)

    Vavassori, P.; Busato, A.; Chiapatti, A.; di Bona, A.; Valeri, S.; Metlushko, V.; Ilic, B.

    2007-09-01

    We have measured magnetoresistance in single, 1 μm external diameter, Permalloy (Ni 80Fe 20) circular rings with varied inner hole diameter of 150, 300, and 600 nm and film thickness of 25 nm. The Permalloy ring structures and the 10-nm-thick, 250-nm-wide Au nanocontacts were fabricated on a SiO 2/Si substrate using e-beam lithography. Using a four contact geometry we studied the dependence of the magnetoresistance on the direction of the applied field. The experimental data are explained by considering only the conventional anisotropic magnetoresistance effect. Numerical simulations of the current distribution within the samples combined with micromagnetic simulations of the field dependent magnetization profile, yield good agreement with the experimental data. Upon increasing the inner hole diameter (viz. decreasing the ring width) the magnetoresistance measurements show a transition of the reversal process from the "vortex nucleation-displacement-annihilation" sequence to the "onion state-reversed onion state" sequence, typical of narrow nanorings.

  1. Magnetoresistance in single crystalline chromium sulfides

    NASA Astrophysics Data System (ADS)

    Lee, K. D.; Won, C. J.; Song, K. M.; Hur, N.

    2011-03-01

    We studied the anisotropic magnetic and magnetotransport properties of Cr2S3 single crystals grown by using the vapor transport method. Large magnetoresistance of ˜ 46% was observed in 9 T magnetic field applied perpendicular to the c axis near the Néel temperature TN ≈ 118 K. Comparison of electric and magnetic properties of Cr2S3 crystals with different sulfur deficiencies suggested that the electron doping by the sulfur deficiency does not contribute to weak ferromagnetism. The correlation between the field-dependent magnetization and resistivity was analyzed by the polaron hopping model of magnetotransport in Cr2S3.

  2. Magnetoresistance of nanosized magnetic configurations in single nanowires

    NASA Astrophysics Data System (ADS)

    Wegrowe, J.-E.; Gilbert, S.; Doudin, B.; Ansermet, J.-Ph.

    1998-03-01

    The problem of studying spin configurations at nanoscopic level is that magnetic measurements at this scale cannot be performed using usual magnetometers. We have shown that anisotropic magnetoresistance (AMR) measured with micro-contacts allows spin configurations of a single nanowire to be studied in details. The nanowires are diameter 50 nm and length 6000 nm and are produced by a combination of electrodeposition in track-etched membrane templates and sputtering technics. Magnetoresistance of well-defined spin configurations in single nanowires, like Curling magnetization reversal modes or domain wall, are measured.

  3. Spin Hall magnetoresistance induced by a nonequilibrium proximity effect.

    PubMed

    Nakayama, H; Althammer, M; Chen, Y-T; Uchida, K; Kajiwara, Y; Kikuchi, D; Ohtani, T; Geprägs, S; Opel, M; Takahashi, S; Gross, R; Bauer, G E W; Goennenwein, S T B; Saitoh, E

    2013-05-17

    We report anisotropic magnetoresistance in Pt|Y(3)Fe(5)O(12) bilayers. In spite of Y(3)Fe(5)O(12) being a very good electrical insulator, the resistance of the Pt layer reflects its magnetization direction. The effect persists even when a Cu layer is inserted between Pt and Y(3)Fe(5)O(12), excluding the contribution of induced equilibrium magnetization at the interface. Instead, we show that the effect originates from concerted actions of the direct and inverse spin Hall effects and therefore call it "spin Hall magnetoresistance." PMID:25167435

  4. Magnetoresistive nanosensors: controlling magnetism at the nanoscale.

    PubMed

    Leitao, Diana C; Silva, Ana V; Paz, Elvira; Ferreira, Ricardo; Cardoso, Susana; Freitas, Paulo P

    2016-01-29

    The ability to detect the magnetic fields that surround us has promoted vast technological advances in sensing techniques. Among those, magnetoresistive sensors display an unpaired spatial resolution. Here, we successfully control the linear range of nanometric sensors using an interfacial exchange bias sensing layer coupling. An effective matching of material properties and sensor geometry improves the nanosensor performance, with top sensitivities of 3.7% mT(-1). The experimental results are well supported by 3D micromagnetic and magneto-transport simulations. PMID:26658286

  5. Magnetoresistive nanosensors: controlling magnetism at the nanoscale

    NASA Astrophysics Data System (ADS)

    Leitao, Diana C.; Silva, Ana V.; Paz, Elvira; Ferreira, Ricardo; Cardoso, Susana; Freitas, Paulo P.

    2016-01-01

    The ability to detect the magnetic fields that surround us has promoted vast technological advances in sensing techniques. Among those, magnetoresistive sensors display an unpaired spatial resolution. Here, we successfully control the linear range of nanometric sensors using an interfacial exchange bias sensing layer coupling. An effective matching of material properties and sensor geometry improves the nanosensor performance, with top sensitivities of 3.7% mT-1. The experimental results are well supported by 3D micromagnetic and magneto-transport simulations.

  6. Giant Magnetoresistance: Basic Concepts, Microstructure, Magnetic Interactions and Applications.

    PubMed

    Ennen, Inga; Kappe, Daniel; Rempel, Thomas; Glenske, Claudia; Hütten, Andreas

    2016-01-01

    The giant magnetoresistance (GMR) effect is a very basic phenomenon that occurs in magnetic materials ranging from nanoparticles over multilayered thin films to permanent magnets. In this contribution, we first focus on the links between effect characteristic and underlying microstructure. Thereafter, we discuss design criteria for GMR-sensor applications covering automotive, biosensors as well as nanoparticular sensors. PMID:27322277

  7. Giant Magnetoresistance: Basic Concepts, Microstructure, Magnetic Interactions and Applications

    PubMed Central

    Ennen, Inga; Kappe, Daniel; Rempel, Thomas; Glenske, Claudia; Hütten, Andreas

    2016-01-01

    The giant magnetoresistance (GMR) effect is a very basic phenomenon that occurs in magnetic materials ranging from nanoparticles over multilayered thin films to permanent magnets. In this contribution, we first focus on the links between effect characteristic and underlying microstructure. Thereafter, we discuss design criteria for GMR-sensor applications covering automotive, biosensors as well as nanoparticular sensors. PMID:27322277

  8. Magnetoresistive Flux Focusing Eddy Current Flaw Detection

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A. (Inventor); Namkung, Min (Inventor); Simpson, John W. (Inventor)

    2005-01-01

    A giant magnetoresistive flux focusing eddy current device effectively detects deep flaws in thick multilayer conductive materials. The probe uses an excitation coil to induce eddy currents in conducting material perpendicularly oriented to the coil s longitudinal axis. A giant magnetoresistive (GMR) sensor, surrounded by the excitation coil, is used to detect generated fields. Between the excitation coil and GMR sensor is a highly permeable flux focusing lens which magnetically separates the GMR sensor and excitation coil and produces high flux density at the outer edge of the GMR sensor. The use of feedback inside the flux focusing lens enables complete cancellation of the leakage fields at the GMR sensor location and biasing of the GMR sensor to a location of high magnetic field sensitivity. In an alternate embodiment, a permanent magnet is positioned adjacent to the GMR sensor to accomplish the biasing. Experimental results have demonstrated identification of flaws up to 1 cm deep in aluminum alloy structures. To detect deep flaws about circular fasteners or inhomogeneities in thick multi-layer conductive materials, the device is mounted in a hand-held rotating probe assembly that is connected to a computer for system control, data acquisition, processing and storage.

  9. Magnetoresistive flux focusing eddy current flaw detection

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A. (Inventor); Namkung, Min (Inventor); Simpson, John W. (Inventor)

    2005-01-01

    A giant magnetoresistive flux focusing eddy current device effectively detects deep flaws in thick multilayer conductive materials. The probe uses an excitation coil to induce eddy currents in conducting material perpendicularly oriented to the coil's longitudinal axis. A giant magnetoresistive (GMR) sensor, surrounded by the excitation coil, is used to detect generated fields. Between the excitation coil and GMR sensor is a highly permeable flux focusing lens which magnetically separates the GMR sensor and excitation coil and produces high flux density at the outer edge of the GMR sensor. The use of feedback inside the flux focusing lens enables complete cancellation of the leakage fields at the GMR sensor location and biasing of the GMR sensor to a location of high magnetic field sensitivity. In an alternate embodiment, a permanent magnet is positioned adjacent to the GMR sensor to accomplish the biasing. Experimental results have demonstrated identification of flaws up to 1 cm deep in aluminum alloy structures. To detect deep flaws about circular fasteners or inhomogeneities in thick multilayer conductive materials, the device is mounted in a hand-held rotating probe assembly that is connected to a computer for system control, data acquisition, processing and storage.

  10. Magnetoresistance studies of multilayers including hard magnetic CoSm layers

    NASA Astrophysics Data System (ADS)

    Mibu, K.; Nagahama, T.; Shinjo, T.

    1996-04-01

    Cobalt-samarium alloy films were prepared by alternate deposition of Co and Sm in the presence of an external magnetic field to obtain thin magnetic layers with large in-plane coercive fields. These anisotropic CoSm layers were used as hard magnetic layers of noncoupled-type magnetoresistance multilayers or as pinning layers of spin-valve structures. Large magnetoresistance changes up to 4.6% were attained in the CoSm/Co/Cu/NiFe system.

  11. Anomalous electronic structure and magnetoresistance in TaAs2.

    PubMed

    Luo, Yongkang; McDonald, R D; Rosa, P F S; Scott, B; Wakeham, N; Ghimire, N J; Bauer, E D; Thompson, J D; Ronning, F

    2016-01-01

    The change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. Density functional calculations find that TaAs2 is a new topological semimetal [ℤ2 invariant (0;111)] without Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions. PMID:27271852

  12. Anomalous electronic structure and magnetoresistance in TaAs2

    NASA Astrophysics Data System (ADS)

    Luo, Yongkang; McDonald, R. D.; Rosa, P. F. S.; Scott, B.; Wakeham, N.; Ghimire, N. J.; Bauer, E. D.; Thompson, J. D.; Ronning, F.

    2016-06-01

    The change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. Density functional calculations find that TaAs2 is a new topological semimetal [ℤ2 invariant (0;111)] without Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions.

  13. Electronic structure basis for the extraordinary magnetoresistance in WTe2

    DOE PAGESBeta

    Pletikosić, I.; Ali, Mazhar N.; Fedorov, A. V.; Cava, R. J.; Valla, T.

    2014-11-19

    The electronic structure basis of the extremely large magnetoresistance in layered non-magnetic tungsten ditelluride has been investigated by angle-resolved photoelectron spectroscopy. Hole and electron pockets of approximately the same size were found at the Fermi level, suggesting that carrier compensation should be considered the primary source of the effect. The material exhibits a highly anisotropic, quasi one-dimensional Fermi surface from which the pronounced anisotropy of the magnetoresistance follows. As a result, a change in the Fermi surface with temperature was found and a high-density-of-states band that may take over conduction at higher temperatures and cause the observed turn-on behavior ofmore » the magnetoresistance in WTe₂ was identified.« less

  14. Anomalous electronic structure and magnetoresistance in TaAs2

    PubMed Central

    Luo, Yongkang; McDonald, R. D.; Rosa, P. F. S.; Scott, B.; Wakeham, N.; Ghimire, N. J.; Bauer, E. D.; Thompson, J. D.; Ronning, F.

    2016-01-01

    The change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. Density functional calculations find that TaAs2 is a new topological semimetal [ℤ2 invariant (0;111)] without Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions. PMID:27271852

  15. Anomalous electronic structure and magnetoresistance in TaAs2

    DOE PAGESBeta

    Luo, Yongkang; McDonald, R. D.; Rosa, P. F. S.; Scott, B.; Wakeham, N.; Ghimire, N. J.; Bauer, E. D.; Thompson, J. D.; Ronning, F.

    2016-01-01

    We report that the change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. In conclusion, density functional calculations find that TaAs2 is a new topological semimetal [Z2 invariant (0;111)] withoutmore » Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions.« less

  16. Magnetization reversal in permalloy ferromagnetic nanowires investigated with magnetoresistance measurements

    NASA Astrophysics Data System (ADS)

    Oliveira, A. B.; Rezende, S. M.; Azevedo, A.

    2008-07-01

    The magnetization reversal process in single Permalloy (Ni81Fe19) nanowires has been investigated by magnetoresistance measurements as a function of the angle between the applied field and the wire direction. The Permalloy nanostructures fabricated on an ultrathin film by atomic force microscopy consist of two large rectangular pads connected by a nanowire with the shape of a long thin narrow tape. For each field direction in the plane of the film the dependence of the magnetoresistance on the field value exhibits two main contributions: one from the pads and one from the nanowire. The contribution from the pads is due to a usual anisotropic magnetoresistance characteristic of coherent magnetization rotation, whereas the contribution from the nanowire is an abrupt transition at the switching field. The dependence of the switching field on the in-plane field angle is quantitatively described by a model of nucleation field with the buckling magnetization rotation mode.

  17. Systematic Angular Study of Magnetoresistance in Permalloy Connected Kagome Artificial Spin Ice

    NASA Astrophysics Data System (ADS)

    Park, Jungsik; Le, Brian; Watts, Justin; Leighton, Chris; Samarth, Nitin; Schiffer, Peter

    Artificial spin ices are nanostructured two-dimensional arrays of ferromagnetic elements, where frustrated interactions lead to unusual collective magnetic behavior. Here we report a room-temperature magnetoresistance study of connected permalloy (Ni81Fe19) kagome artificial spin ice networks, wherein the direction of the applied in-plane magnetic field is systematically varied. We measure both the longitudinal and transverse magnetoresistance in these structures, and we find certain transport geometries of the network show strong angular sensitivity - even small variations in the applied field angle lead to dramatic changes of the magnetoresistance response. We also investigate the magnetization reversal of the networks using magnetic force microscopy (MFM), demonstrating avalanche behavior in the magnetization reversal. The magnetoresistance features are analyzed using an anisotropic magnetoresistance (AMR) model. Supported by the US Department of Energy. Work at the University of Minnesota was supported by Seagate Technology, NSF MRSEC, and a Marie Curie International Outgoing Fellowship within the 7th European Community Framework Programme.

  18. The magnetization process and magnetoresistance of exchange-spring bilayer systems

    NASA Astrophysics Data System (ADS)

    Nagahama, T.; Mibu, K.; Shinjo, T.

    1998-01-01

    A perfectly reversible magnetization process was observed in NiFe/CoSm bilayers. During this process, the magnetic moments in the soft magnetic layer (NiFe) are pinned at the interface with the hard magnetic layer (CoSm), so that the direction of the magnetic moment distributes successively like a Bloch wall. The characteristic reversible magnetization process is explained by an atomic layer model. The magnetoresistance also exhibits a reversible change reflecting the magnetization process. The basic feature of the reversible magnetoresistance curve is understood to be anisotropic magnetoresistance.

  19. Giant positive magnetoresistance in metallic VOx thin films

    NASA Astrophysics Data System (ADS)

    Rata, A. D.; Kataev, V.; Khomskii, D.; Hibma, T.

    2003-12-01

    We report on giant positive magnetoresistance (MR) effect observed in VOx thin films, epitaxially grown on SrTiO3 substrate. The MR effect depends strongly on temperature and oxygen content and is anisotropic. At low temperatures its magnitude reaches 70% in a magnetic field of 5 T. Strong electron-electron interactions in the presence of strong disorder may qualitatively explain the results. An alternative explanation, related to a possible magnetic instability, is also discussed.

  20. Magnetoresistance of heavy and light metal/ferromagnet bilayers

    SciTech Connect

    Avci, Can Onur; Garello, Kevin; Mendil, Johannes; Ghosh, Abhijit; Blasakis, Nicolas; Gabureac, Mihai; Trassin, Morgan; Fiebig, Manfred; Gambardella, Pietro

    2015-11-09

    We studied the magnetoresistance of normal metal (NM)/ferromagnet (FM) bilayers in the linear and nonlinear (current-dependent) regimes and compared it with the amplitude of the spin-orbit torques and thermally induced electric fields. Our experiments reveal that the magnetoresistance of the heavy NM/Co bilayers (NM = Ta, W, and Pt) is phenomenologically similar to the spin Hall magnetoresistance (SMR) of YIG/Pt, but has a much larger anisotropy of the order of 0.5%, which increases with the atomic number of the NM. This SMR-like behavior is absent in light NM/Co bilayers (NM = Ti and Cu), which present the standard anisotropic magnetoresistance expected from polycrystalline FM layers. In the Ta, W, and Pt/Co bilayers, we find an additional magnetoresistance directly proportional to the current and to the transverse component of the magnetization. This so-called unidirectional SMR, of the order of 0.005%, is largest in W and correlates with the amplitude of the antidamping spin-orbit torque. The unidirectional SMR is below the accuracy of our measurements in YIG/Pt.

  1. Features of the electric-field distribution in anisotropic semiconductor wafers in a transverse magnetic field

    SciTech Connect

    Filippov, V. V.; Bormontov, E. N.

    2013-07-15

    A macroscopic model of the Hall effects and magnetoresistance in anisotropic semiconductor wafers is developed. The results obtained by solving the electrodynamic boundary problem allow the potential and eddy currents in anisotropic semiconductors to be calculated at different current-contact locations, depending on the parameters of the sample material's anisotropy. The results of this study are of great practical importance for investigating the physical properties of anisotropic semiconductors and simulating the electron-transport phenomena in devices based on anisotropic semiconductors.

  2. Large, non-saturating magnetoresistance in WTe2.

    PubMed

    Ali, Mazhar N; Xiong, Jun; Flynn, Steven; Tao, Jing; Gibson, Quinn D; Schoop, Leslie M; Liang, Tian; Haldolaarachchige, Neel; Hirschberger, Max; Ong, N P; Cava, R J

    2014-10-01

    Magnetoresistance is the change in a material's electrical resistance in response to an applied magnetic field. Materials with large magnetoresistance have found use as magnetic sensors, in magnetic memory, and in hard drives at room temperature, and their rarity has motivated many fundamental studies in materials physics at low temperatures. Here we report the observation of an extremely large positive magnetoresistance at low temperatures in the non-magnetic layered transition-metal dichalcogenide WTe2: 452,700 per cent at 4.5 kelvins in a magnetic field of 14.7 teslas, and 13 million per cent at 0.53 kelvins in a magnetic field of 60 teslas. In contrast with other materials, there is no saturation of the magnetoresistance value even at very high applied fields. Determination of the origin and consequences of this effect, and the fabrication of thin films, nanostructures and devices based on the extremely large positive magnetoresistance of WTe2, will represent a significant new direction in the study of magnetoresistivity. PMID:25219849

  3. Large, non-saturating magnetoresistance in WTe2

    NASA Astrophysics Data System (ADS)

    Ali, Mazhar N.; Xiong, Jun; Flynn, Steven; Tao, Jing; Gibson, Quinn D.; Schoop, Leslie M.; Liang, Tian; Haldolaarachchige, Neel; Hirschberger, Max; Ong, N. P.; Cava, R. J.

    2014-10-01

    Magnetoresistance is the change in a material's electrical resistance in response to an applied magnetic field. Materials with large magnetoresistance have found use as magnetic sensors, in magnetic memory, and in hard drives at room temperature, and their rarity has motivated many fundamental studies in materials physics at low temperatures. Here we report the observation of an extremely large positive magnetoresistance at low temperatures in the non-magnetic layered transition-metal dichalcogenide WTe2: 452,700 per cent at 4.5 kelvins in a magnetic field of 14.7 teslas, and 13 million per cent at 0.53 kelvins in a magnetic field of 60 teslas. In contrast with other materials, there is no saturation of the magnetoresistance value even at very high applied fields. Determination of the origin and consequences of this effect, and the fabrication of thin films, nanostructures and devices based on the extremely large positive magnetoresistance of WTe2, will represent a significant new direction in the study of magnetoresistivity.

  4. Large, Tunable Magnetoresistance in Nonmagnetic III-V Nanowires.

    PubMed

    Li, Sichao; Luo, Wei; Gu, Jiangjiang; Cheng, Xiang; Ye, Peide D; Wu, Yanqing

    2015-12-01

    Magnetoresistance, the modulation of resistance by magnetic fields, has been adopted and continues to evolve in many device applications including hard-disk, memory, and sensors. Magnetoresistance in nonmagnetic semiconductors has recently raised much attention and shows great potential due to its large magnitude that is comparable or even larger than magnetic materials. However, most of the previous work focus on two terminal devices with large dimensions, typically of micrometer scales, which severely limit their performance potential and more importantly, scalability in commercial applications. Here, we investigate magnetoresistance in the impact ionization region in InGaAs nanowires with 20 nm diameter and 40 nm gate length. The deeply scaled dimensions of these nanowires enable high sensibility with less power consumption. Moreover, in these three terminal devices, the magnitude of magnetoresistance can be tuned by the transverse electric field controlled by gate voltage. Large magnetoresistance between 100% at room temperature and 2000% at 4.3 K can be achieved at 2.5 T. These nanoscale devices with large magnetoresistance offer excellent opportunity for future high-density large-scale magneto-electric devices using top-down fabrication approaches, which are compatible with commercial silicon platform. PMID:26561728

  5. Advanced giant magnetoresistance technology for measurement applications

    NASA Astrophysics Data System (ADS)

    Weiss, Roland; Mattheis, Roland; Reiss, Günter

    2013-08-01

    Giant magnetoresistance (GMR) sensors are considered one of the first real applications of nanotechnology. They consist of nm-thick layered structures where ferromagnetic metals are sandwiched by nonmagnetic metals. Such multilayered films produce a large change in resistance (typically 10 to 20%) when subjected to a magnetic field, compared with a maximum change of a few per cent for other types of magnetic sensors. This technology has been intensively used in read heads for hard disk drives and now increasingly finds applications due to the high sensitivity and signal-to-noise ratio. Additionally these sensors are compatible with miniaturization and thus offer a high spatial resolution combined with a frequency range up to the 100 MHz regime and simple electronic conditioning. In this review, we first discuss the basics of the underlying magnetoresistance effects in layered structures and then present three prominent examples for future applications: in the field of current sensing the new GMR sensors offer high bandwidth and good accuracy in a space-saving open loop measurement configuration. In rotating systems they can be used for multiturn angle measurements, and in biotechnology the detection of magnetic particles enables the quantitative measurement of biomolecule concentrations.

  6. Magnetoresistive Emulsion Analyzer

    PubMed Central

    Lin, Gungun; Baraban, Larysa; Han, Luyang; Karnaushenko, Daniil; Makarov, Denys; Cuniberti, Gianaurelio; Schmidt, Oliver G.

    2013-01-01

    We realize a magnetoresistive emulsion analyzer capable of detection, multiparametric analysis and sorting of ferrofluid-containing nanoliter-droplets. The operation of the device in a cytometric mode provides high throughput and quantitative information about the dimensions and magnetic content of the emulsion. Our method offers important complementarity to conventional optical approaches involving ferrofluids, and paves the way to the development of novel compact tools for diagnostics and nanomedicine including drug design and screening. PMID:23989504

  7. Magnetoresistive emulsion analyzer.

    PubMed

    Lin, Gungun; Baraban, Larysa; Han, Luyang; Karnaushenko, Daniil; Makarov, Denys; Cuniberti, Gianaurelio; Schmidt, Oliver G

    2013-01-01

    We realize a magnetoresistive emulsion analyzer capable of detection, multiparametric analysis and sorting of ferrofluid-containing nanoliter-droplets. The operation of the device in a cytometric mode provides high throughput and quantitative information about the dimensions and magnetic content of the emulsion. Our method offers important complementarity to conventional optical approaches involving ferrofluids, and paves the way to the development of novel compact tools for diagnostics and nanomedicine including drug design and screening. PMID:23989504

  8. Magnetoresistance of Au films

    DOE PAGESBeta

    Zhang, D. L.; Song, X. H.; Zhang, X.; Zhang, Xiaoguang

    2014-12-10

    Measurement of the magnetoresistance (MR) of Au films as a function of temperature and film thickness reveals a strong dependence on grain size distribution and clear violation of the Kohler s rule. Using a model of random resistor network, we show that this result can be explained if the MR arises entirely from inhomogeneity due to grain boundary scattering and thermal activation of grain boundary atoms.

  9. Magnetoresistance of Au films

    SciTech Connect

    Zhang, D. L.; Song, X. H.; Zhang, X; Zhang, Xiaoguang

    2014-01-01

    Measurement of the magnetoresistance (MR) of Au films as a function of temperature and film thickness reveals a strong dependence on grain size distribution and clear violation of the Kohler s rule. Using a model of random resistor network, we show that this result can be explained if the MR arises entirely from inhomogeneity due to grain boundary scattering and thermal activation of grain boundary atoms.

  10. Planar Hall magnetoresistive aptasensor for thrombin detection.

    PubMed

    Sinha, B; Ramulu, T S; Kim, K W; Venu, R; Lee, J J; Kim, C G

    2014-09-15

    The use of aptamer-based assays is an emerging and attractive approach in disease research and clinical diagnostics. A sensitive aptamer-based sandwich-type sensor is presented to detect human thrombin using a planar Hall magnetoresistive (PHR) sensor in cooperation with superparamagnetic labels. A PHR sensor has the great advantages of a high signal-to-noise ratio, a small offset voltage and linear response in the low-field region, allowing it to act as a high-resolution biosensor. In the system presented here, the sensor has an active area of 50 µm × 50 µm with a 10-nm gold layer deposited onto the sensor surface prior to the binding of thiolated DNA primary aptamer. A polydimethylsiloxane well of 600-µm radius and 1-mm height was prepared around the sensor surface to maintain the same specific area and volume for each sensor. The sensor response was traced in real time upon the addition of streptavidin-functionalized magnetic labels on the sensor. A linear response to the thrombin concentration in the range of 86 pM-8.6 µM and a lower detection limit down to 86 pM was achieved by the proposed present method with a sample volume consumption of 2 µl. The proposed aptasensor has a strong potential for application in clinical diagnosis. PMID:24727201

  11. Electronic structure origins of the extremely large magnetoresistance in tungsten ditelluride

    NASA Astrophysics Data System (ADS)

    Pletikosic, Ivo; Ali, Mazhar; Cava, Robert; Valla, Tonica

    2015-03-01

    WTe2 is a layered transition metal dichalcogenide showing a structural reduction to one-dimensional tellurium-surrounded tungsten chains. The material exhibits an extremely large positive anisotropic magnetoresistance of a few million percent that increases as the square of the field and shows no saturation up to 60 T. We explored the possible electronic structure origins of the magnetoresistance by means of angle-resolved photoelectron spectroscopy (ARPES) and found electron and hole pockets of equal size along the direction of tungsten chains, forming a highly anisotropic quasi-twodimensional Fermi surface. The perfect carrier compensation at low temperatures has been identified as the primary source of the magnetoresistive effect, and the change of the Fermi surface shape as well as a high-density-of-states band slightly below the Fermi level recognized as the cause of its diminishing at rising temperatures.

  12. Shape-coupled magnetoresistive structures: a new approach to higher sensitivity

    NASA Astrophysics Data System (ADS)

    Dyuzhev, N. A.; Yurov, A. S.; Preobrazhenskii, R. Yu.; Mazurkin, N. S.; Chinenkov, M. Yu.

    2016-05-01

    A new type of anisotropic magnetoresistive structures is proposed in which the shape of ferromagnetic elements repeats the shape of nonmagnetic conducting shunts. The results of numerical simulations with allowance for inhomogeneous magnetization distribution showed that these shape-coupled structures exhibit a significant (~70%) increase in sensitivity as compared to that of classical barber-pole structures.

  13. Theory of magnetoresistance due to lattice dislocations in face-centred cubic metals

    NASA Astrophysics Data System (ADS)

    Bian, Q.; Niewczas, M.

    2016-06-01

    A theoretical model to describe the low temperature magneto-resistivity of high purity copper single and polycrystals containing different density and distribution of dislocations has been developed. In the model, magnetoresistivity tensor is evaluated numerically using the effective medium approximation. The anisotropy of dislocation-induced relaxation time is considered by incorporating two independent energy bands with different relaxation times and the spherical and cylindrical Fermi surfaces representing open, extended and closed electron orbits. The effect of dislocation microstructure is introduced by means of two adjustable parameters corresponding to the length and direction of electron orbits in the momentum space, which permits prediction of magnetoresistance of FCC metals containing different density and distribution of dislocations. The results reveal that dislocation microstructure influences the character of the field-dependent magnetoresistivity. In the orientation of the open orbits, the quadratic variation in magnetoresistivity changes to quasi-linear as the density of dislocations increases. In the closed orbit orientation, dislocations delay the onset of magnetoresistivity saturation. The results indicate that in the open orbit orientations of the crystals, the anisotropic relaxation time due to small-angle dislocation scattering induces the upward deviation from Kohler's rule. In the closed orbit orientations Kohler's rule holds, independent of the density of dislocations. The results obtained with the model show good agreement with the experimental measurements of transverse magnetoresistivity in deformed single and polycrystal samples of copper at 2 K.

  14. Spin Hall magnetoresistance in ultra thin Pt/LSMO

    NASA Astrophysics Data System (ADS)

    Lei, Na; Bai, Yu; Ding, Zhao; Shao, Jian; Wei, Wengang; Yin, Lifeng; Wu, Yizheng; Shen, Jian

    Spin Hall magnetoresistance (SMR) in a non-/ ferro- magnetic (NM/FM) bilayer is an angular dependence of resistance of the NM layer on the magnetization of FM layer. It provides an easy approach to the spin Hall effect in a simple bilayer system, however similar effects mixed in the system and might complicated the data analysis and interpretation. Here we present a case of ultra thin Pt/LSMO, in which LSMO (bellow 7 unit cells) layer is an insulating magnetic oxide with Curie temperature of 120K. Below 120K, our results clearly show the coexistence of the anisotropic magnetoresistance (AMR) and SMR effects. However, far away above Curie temperature, where the LSMO is paramagnetic, the magnetoresistance doesn't disappear but even increase, which is distinct from the case of Pt/YIG. Here it is neither SMR nor AMR, and an additional mechanism is required. Anomalous Hall effect was also performed, which is consistent with SMR measurement. We propose some physical pictures which could attribute to this magnetoresistance in paramagnetic state.

  15. Reversible magnetization process and magnetoresistance of soft-magnetic (NiFe) /hard-magnetic (CoSm) bilayers

    NASA Astrophysics Data System (ADS)

    Mibu, K.; Nagahama, T.; Shinjo, T.

    1996-10-01

    The magnetization process and magnetoresistance were studied for soft-magnetic (NiFe)/hard-magnetic (CoSm) bilayers. In the course of the magnetization reversal, the magnetic moments in the soft magnetic layer rotate reversibly, while they are pinned by the hard magnetic layer at the interface; consequently, the direction of the magnetic moment distributes successively as in a Bloch wall. The magnetoresistance also shows a reversible change, reflecting the magnetization process. The change is explained by means of the anisotropic magnetoresistance due to angle distributed magnetic moments.

  16. Nanoscale dissipation and magnetoresistive 1/f noise in spin valves

    NASA Astrophysics Data System (ADS)

    Diao, Zhu; Nowak, E. R.; Haughey, K. M.; Coey, J. M. D.

    2011-09-01

    Spatial correlations of 1/f noise in yoke-shaped, giant magnetoresistance spin valve sensors are reported. An upper bound of 135 nm, corresponding to a magnetic volume of <105 nm3, is determined for the lateral size of the magnetic fluctuators responsible for the magnetoresistive 1/f noise in regions where the resistance susceptibility is large. The normalized noise power is found to scale inversely with the separation between voltage taps along the arm of the yoke, also consistent with a local noise mechanism. The magnetoresistive 1/f noise is associated with quasiequilibrium fluctuations in the micromagnetic structure having a length scale set by the disorder formed during the deposition and processing of the materials stack.

  17. Noncontact vibration measurements using magnetoresistive sensing elements

    NASA Astrophysics Data System (ADS)

    Tomassini, R.; Rossi, G.

    2016-06-01

    Contactless instrumentations is more and more used in turbomachinery testing thanks to the non-intrusive character and the possibility to monitor all the components of the machine at the same time. Performances of blade tip timing (BTT) measurement systems, used for noncontact turbine blade vibration measurements, in terms of uncertainty and resolution are strongly affected by sensor characteristics and processing methods. The sensors used for BTT generate pulses, used for precise measurements of turbine blades time of arrival. Nowadays proximity sensors used in this application are based on optical, capacitive, eddy current and microwave measuring principle. Pressure sensors has been also tried. This paper summarizes the results achieved using a novel instrumentation based on the magnetoresistive sensing elements. The characterization of the novel probe has been already published. The measurement system was validated in test benches and in a real jet-engine comparing different sensor technologies. The whole instrumentation was improved. The work presented in this paper focuses on the current developments. In particular, attention is given to the data processing software and new sensor configurations.

  18. Spin Hall magnetoresistance in ferromagnetic insulator/normal metal hybrids

    NASA Astrophysics Data System (ADS)

    Althammer, Matthias

    2014-03-01

    Pure spin currents, i.e. the net flow of spin angular momentum without an accompanying charge current, represent a new paradigm for spin transport and spintronics. We have experimentally studied a new type of magnetoresistance effect, which arises from the interaction of charge and spin current flows in ferromagnetic insulator/normal metal hybrid structures. In more detail, we measured the resistance of yttrium iron garnet(YIG)/Pt, YIG/nonferromagnet/Pt, nickel ferrite/Pt, and magnetite/Pt hybrid structures as a function of the magnitude and the orientation of an external magnetic field. The resistance changes observed can be quantitatively traced back to the combined action of spin Hall and inverse spin Hall effect in the Pt metal layer, and are thus termed spin Hall magnetoresistance (SMR) [ 1 , 2 ] . We show that the SMR is qualitatively different from the conventional anisotropic magnetoresistance effect arising in magnetic metals. From the magnetoresistance measurements in YIG/Au/Pt and YIG/Cu/Pt structures and from x-ray magnetic circular dichroism measurements on YIG/Pt heterostructures we exclude a static proximity magnetization in Pt as the origin of the magnetoresistance, in contrast to the mechanism proposed by Huang et al. [ 3 ] . Furthermore, the SMR enables us to quantify the spin Hall angle as a function of temperature in our Pt layers. In addition, we analyze the anomalous Hall type contribution of the SMR to quantify the imaginary part of the spin mixing conductance. Financial support by the DFG via SPP 1538 (project no. GO 944/4) and the Nanoinitiative Munich (NIM) is gratefully acknowledged.

  19. Transversal magnetoresistance in Weyl semimetals

    NASA Astrophysics Data System (ADS)

    Klier, J.; Gornyi, I. V.; Mirlin, A. D.

    2015-11-01

    We explore theoretically the magnetoresistivity of three-dimensional Weyl and Dirac semimetals in transversal magnetic fields within two alternative models of disorder: (i) short-range impurities and (ii) charged (Coulomb) impurities. Impurity scattering is treated using the self-consistent Born approximation. We find that an unusual broadening of Landau levels leads to a variety of regimes of the resistivity scaling in the temperature-magnetic field plane. In particular, the magnetoresistance is nonmonotonous for the white-noise disorder model. For H →0 the magnetoresistance for short-range impurities vanishes in a nonanalytic way as H1 /3. In the limits of strongest magnetic fields H , the magnetoresistivity vanishes as 1 /H for pointlike impurities, while it is linear and positive in the model with Coulomb impurities.

  20. Anomalous oscillatory magnetoresistance in superconductors

    NASA Astrophysics Data System (ADS)

    Kunchur, Milind N.; Dean, Charles L.; Ivlev, Boris I.

    2016-08-01

    We report oscillatory magnetoresistance in various superconducting films, with a magnetic-field period Δ B ˜0.1 T that is essentially independent of sample dimensions, temperature, transport current, and the magnitude and orientation of the magnetic field, including magnetic fields oriented parallel to the film plane. The characteristics of these oscillations seem hard to reconcile with previously established mechanisms for oscillations in magnetoresistance, suggesting the possibility of another type of physical origin.

  1. Magnetoresistive smart fluid (marsonpol) and devices

    NASA Astrophysics Data System (ADS)

    Reji, John; Suresh, G.; Narayanadas, D. J.

    2003-10-01

    Magnetorheological fluid, Electrorheological fluid and ferro fluids are the smart fluids known today. These fluids are either electrically conductive or non conductive. They do not exhibit variable electrical resistance or switching behavior. Of recent interest to researchers has been the development of new types of magnetoresistive materials. Such materials can be of large practical importance, as they will change their electrical resistance in the presence of a magnetic field. However, most materials only exhibit appreciable magnetoresistance under extreme conditions, such as high magnetic fields or low temperatures. A smart fluid whose electrical resistance can be varied by several orders of magnitude under nominal level of magnetic field is reported in this paper (designated MARSONPOL). In the absence of a magnetic field the fluid is an insulator having electrical resistance in the order of 108 ohm-meter and in the presence of a magnetic field the resistance of the material reduces to less than 1 ohm-meter, at room temperature of 30°C. The sharp and reversible change in resistivity makes the material transform from an insulator to conductor, rendering properties characteristic of either state, within a fraction of a second. Fluids with such characteristics are not reported in the literature making this development a breakthrough and opening up potentials for the development of several smart devices. One such device is the magnetic field sensor probe currently under development at NPOL. A capsule of MARSONPOL forms the basic sensor element. Depending on the strength of the Magnetic field, the electrical resistivity of the capsule undergoes changes. The present paper will discuss details of the smart fluid as well as features of the magnetic field sensor.

  2. Magnetization process modeling of anisotropic magnetoresistive permalloy films

    NASA Astrophysics Data System (ADS)

    Hauser, H.; Fulmek, P. L.

    2003-01-01

    The results of model calculations by the Jiles-Atherton approach and the energetic model (EM) of ferromagnetic hysteresis are discussed. In contrast to other phenomenological models, the EM parameters are calculated directly from the angle of the magnetization with respect to the easy axis. The transversal Kerr-effect is used to determine the magnetic properties of thin ferromagnetic permalloy films with uniaxial anisotropy.

  3. Temperature dependence of the magnetoresistance in Co/Re superlattices on Al2O3 (112¯0)

    NASA Astrophysics Data System (ADS)

    Charlton, T.; Lederman, D.

    2001-03-01

    Using a patterned hcp [Co (17 Å)/Re (7Å)]20 antiferromagnetically coupled superlattice, with the c axis in the film plane, magnetoresistance (MR) measurements were made in the temperature range between 5 K and room temperature. The MR was simulated and decomposed into its anisotropic magnetoresistance (AMR) and giant magnetoresistance (GMR) components using the magnetization as a function of angle determined from neutron reflectivity experiments. We find that the GMR is anisotropic and has a different temperature dependence than the AMR when I⊥c and a similar dependence when I||c, where I is the applied current. This implies that interface spin-dependent scattering plays a more significant role when I⊥c than when I||c.

  4. Temperature dependence of magnetoresistance in GdFeCo/Pt heterostructure

    NASA Astrophysics Data System (ADS)

    Okuno, Takaya; Kim, Kab-Jin; Tono, Takayuki; Kim, Sanghoon; Moriyama, Takahiro; Yoshikawa, Hiroki; Tsukamoto, Arata; Ono, Teruo

    2016-07-01

    The temperature dependence of magnetoresistance is investigated in ferrimagnetic GdFeCo/Pt heterostructures. An anomalous Hall effect (AHE) shows a monotonic behavior in temperature even across the magnetization compensation temperature T M, implying that the FeCo moment is responsible for the magnetotransport properties. An anisotropic magnetoresistance (AMR) exhibits a steep increase at low temperatures, which we ascribe to the contribution of a weak antilocalization in an amorphous GdFeCo layer. A spin Hall magnetoresistance (SMR) is found to exist in ferrimagnet/Pt systems and shows a moderate temperature dependence, in contrast to the SMR in YIG/Pt where a significant temperature dependence was observed. These results provide a basic understanding of the magnetotransport in amorphous ferrimagnets/heavy metal heterostructures.

  5. Anomalous magnetoresistance in the spinel superconductor LiTi2O4.

    PubMed

    Jin, K; He, G; Zhang, X; Maruyama, S; Yasui, S; Suchoski, R; Shin, J; Jiang, Y; Yu, H S; Yuan, J; Shan, L; Kusmartsev, F V; Greene, R L; Takeuchi, I

    2015-01-01

    LiTi2O4 is a unique compound in that it is the only known spinel oxide superconductor. The lack of high quality single crystals has thus far prevented systematic investigations of its transport properties. Here we report a careful study of transport and tunnelling spectroscopy in epitaxial LiTi2O4 thin films. An unusual magnetoresistance is observed which changes from nearly isotropic negative to prominently anisotropic positive as the temperature is decreased. We present evidence that shows that the negative magnetoresistance likely stems from the suppression of local spin fluctuations or spin-orbit scattering centres. The positive magnetoresistance suggests the presence of an orbital-related state, also supported by the fact that the superconducting energy gap decreases as a quadratic function of magnetic field. These observations indicate that the spin-orbital fluctuations play an important role in LiTi2O4 in a manner similar to high-temperature superconductors. PMID:25990638

  6. Anomalous electronic structure and magnetoresistance in TaAs2

    SciTech Connect

    Luo, Yongkang; McDonald, R. D.; Rosa, P. F. S.; Scott, B.; Wakeham, N.; Ghimire, N. J.; Bauer, E. D.; Thompson, J. D.; Ronning, F.

    2016-01-01

    We report that the change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. In conclusion, density functional calculations find that TaAs2 is a new topological semimetal [Z2 invariant (0;111)] without Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions.

  7. Nonlocal ordinary magnetoresistance in indium arsenide

    NASA Astrophysics Data System (ADS)

    Liu, Pan.; Yuan, Zhonghui.; Wu, Hao.; Ali, S. S.; Wan, Caihua.; Ban, Shiliang.

    2015-07-01

    Deflection of carriers by Lorentz force results in an ordinary magnetoresistance (OMR) of (μB)2 at low field. Here we demonstrate that the OMR in high mobility semiconductor InAs could be enhanced by measurement geometry where two probes of voltmeter were both placed on one outer side of two probes of current source. The nonlocal OMR was 3.6 times as large as the local one, reaching 1.8×104% at 5 T. The slope of the linear field dependence of the nonlocal OMR was improved from 12.6 T-1 to 45.3 T-1. The improvement was ascribed to polarity-conserved charges accumulating on boundaries in nonlocal region due to Hall effect. This InAs device with nonlocal geometry could be competitive in B-sensors due to its high OMR ratio, linear field dependence and simple structure.

  8. Comparison of a prototype magnetoresistive biosensor to standard fluorescent DNA detection.

    PubMed

    Schotter, J; Kamp, P B; Becker, A; Pühler, A; Reiss, G; Brückl, H

    2004-05-15

    We present a comparative analysis of a magnetoresistive biosensor to standard fluorescent DNA detection. The biosensor consists of giant magnetoresistive (GMR) type Cu/Ni(80)Fe(20) multilayers in the second antiferromagnetic coupling maximum. Each of the 206 elements of the magnetoresistive biosensor is patterned into a spiral-shaped line that can cover the area of a typical DNA spot (70 microm diameter). The probe DNA is assembled on top of the sensor elements in different concentrations ranging from 16 pg/microl to 10 ng/microl. Complementary biotin-labeled analyte DNA is hybridized to the probe DNA at a concentration of 10 ng/microl. A number of different commercially available magnetic microspheres are investigated to determine the most appropriate markers. The experimental comparison shows that the relative sensitivity of the magnetoresistive biosensor is superior to the fluorescent detection at low probe DNA concentrations. PMID:15046745

  9. Using granular C0-AI2O3 spacer for optimization of functional parameters of the FeMn/Fe20Ni80 magnetoresistive films

    NASA Astrophysics Data System (ADS)

    Gorkovenko, A. N.; Lepalovskij, V. N.; Adanakova, O. A.; Vas'kovskiy, V. O.

    2016-03-01

    In this paper we studied the possibility of tailoring the functional properties of the multilayer magnetoresistive medium with unidirectional anisotropy and the anisotropic magnetoresistance effect (AMR). Objects of the research were composite Co-Al2O3 films and Ta/Fe20Ni80/Fe50Mn50/Fe20Ni80/Co-Al2O3/Fe20Ni80/Ta multilayers structures obtained by magnetron sputtering and selectively subjected vacuum annealing. Structure, magnetic and magnetoresistive properties of the films in the temperature range 77÷440 K were investigated.

  10. Pure spin-Hall magnetoresistance in Rh/Y3Fe5O12 hybrid.

    PubMed

    Shang, T; Zhan, Q F; Ma, L; Yang, H L; Zuo, Z H; Xie, Y L; Li, H H; Liu, L P; Wang, B M; Wu, Y H; Zhang, S; Li, Run-Wei

    2015-01-01

    We report an investigation of anisotropic magnetoresistance (AMR) and anomalous Hall resistance (AHR) of Rh and Pt thin films sputtered on epitaxial Y(3)Fe(5)O(12) (YIG) ferromagnetic insulator films. For the Pt/YIG hybrid, large spin-Hall magne toresistance (SMR) along with a sizable conventional anisotropic magnetoresistance (CAMR) and a nontrivial temperature dependence of AHR were observed in the temperature range of 5-300 K. In contrast, a reduced SMR with negligible CAMR and AHR was found in Rh/YIG hybrid. Since CAMR and AHR are characteristics for all ferromagnetic metals, our results suggest that the Pt is likely magnetized by YIG due to the magnetic proximity effect (MPE) while Rh remains free of MPE. Thus the Rh/YIG hybrid could be an ideal model system to explore physics and devices associated with pure spin current. PMID:26639108

  11. CPP magnetoresistance of magnetic multilayers: A critical review

    NASA Astrophysics Data System (ADS)

    Bass, Jack

    2016-06-01

    review is designed to provide a history of how knowledge of CPP-MR parameters grew, to give credit for discoveries, to explain how combining theory and experiment has enabled extraction of quantitative information about these parameters, but also to make clear that progress was not always direct and to point out where disagreements still exist. To limit its length, the review considers only collinear orientations of the moments of adjacent F-layers. To aid readers looking for specific information, we have provided an extensive table of contents and a detailed summary. Together, these should help locate over 100 figures plus 17 tables that collect values of individual parameters. In 1997, CIP-MR replaced anisotropic MR (AMR) as the sensor in read heads of computer hard drives. In principle, the usually larger CPP-MR was a contender for the next generation read head sensor. But in 2003, CIP-MR was replaced by the even larger Tunneling MR (TMR), which has remained the read-head sensor ever since. However, as memory bits shrink to where the relatively large specific resistance AR of TMR gives too much noise and too large an R to impedance match as a read-head sensor, the door is again opened for CPP-MR. We will review progress in finding techniques and F-alloys and F/N pairs to enhance the CPP-MR, and will describe its present capabilities.

  12. Magnetoresistive-based static tester for actuators

    NASA Astrophysics Data System (ADS)

    Borme, J.; Freitas, A. S.; Cardoso, S.; Almeida, J. M.; Chaves, R. C.; Freitas, P. P.

    2008-04-01

    A static tester for precision actuators is proposed. It is intended to test the functioning of future actuators to be used in hard drive read heads. The design allows a simple fabrication of a nanometer-scale position measurement system that can measure lateral, vertical, and angular displacements. The tester consists of (a) a reference magnetic layer of CoCrPt, (150×100μm2, 600nm thick) and (b) a sequence of four spin-valve sensors. The tested sensors have crossed anisotropies, 6.9% magnetoresistance with a linear response, 0.5%/mT sensitivity, coercive field less than 0.1mT and resistance of 1680Ω in the parallel state. A noise level of 6nV/√Hz was measured at thermal background for 0.2mA of applied current. The lateral displacement is measured by the two spin valves in the center. While the magnetic element is passing over these sensors, the measured signal on each of them varies in opposite directions, allowing a precise measurement of the center position. The two outer spin valves are sensitive to the angular orientation of the magnetic element. The relative movements of the spin valves and magnetic element are controlled by computer using piezoelectric crystals and step motors. Since the sensors are measuring the in-plane component of the field, the signal measured decreases rapidly with sensor-to-plane distance. An appropriate range for flight height is about 30μm. Simulations of the signal are in agreement with measurements.

  13. Anisotropic universe with anisotropic sources

    SciTech Connect

    Aluri, Pavan K.; Panda, Sukanta; Sharma, Manabendra; Thakur, Snigdha E-mail: sukanta@iiserb.ac.in E-mail: snigdha@iiserb.ac.in

    2013-12-01

    We analyze the state space of a Bianchi-I universe with anisotropic sources. Here we consider an extended state space which includes null geodesics in this background. The evolution equations for all the state observables are derived. Dynamical systems approach is used to study the evolution of these equations. The asymptotic stable fixed points for all the evolution equations are found. We also check our analytic results with numerical analysis of these dynamical equations. The evolution of the state observables are studied both in cosmic time and using a dimensionless time variable. Then we repeat the same analysis with a more realistic scenario, adding the isotropic (dust like dark) matter and a cosmological constant (dark energy) to our anisotropic sources, to study their co-evolution. The universe now approaches a de Sitter space asymptotically dominated by the cosmological constant. The cosmic microwave background anisotropy maps due to shear are also generated in this scenario, assuming that the universe contains anisotropic matter along with the usual (dark) matter and vacuum (dark) energy since decoupling. We find that they contribute dominantly to the CMB quadrupole. We also constrain the current level of anisotropy and also search for any cosmic preferred axis present in the data. We use the Union 2 Supernovae data to this extent. An anisotropy axis close to the mirror symmetry axis seen in the cosmic microwave background data from Planck probe is found.

  14. On-chip magnetoresistive detection of resonance in microcantilevers

    NASA Astrophysics Data System (ADS)

    Patil, S. B.; Guedes, A.; Freitas, P. P.; Cardoso, S.; Chu, V.; Conde, J. P.

    2009-07-01

    Magnetoresistive spin-valve sensors were used to provide on-chip detection of the mechanical resonance of a thin silicon microelectromechanical systems cantilever. The spin-valve sensor was placed underneath the free end of the cantilever. A CoCrPt thin-film permanent magnet was placed on top of the amorphous silicon/Al cantilever. The cantilever was electrostatically actuated and its deflection creates a change in the magnetic field that can be sensed by the spin-valve sensor. The resonance frequency of the structure in the megahertz range is detected by the measurement of the spin-valve sensor output. Minimum deflection detection limit is determined to be 0.06 Å/Hz1/2.

  15. Giant magnetoresistance materials for magnetic recording technology

    SciTech Connect

    Heffner, R.H.; Adams, C.D.; Brosha, E.L.

    1997-12-01

    This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). This work focused on a class of transition-metal-oxide (TMO) materials (LaMnO{sub 3} doped with Ca, Ba, or Sr) that exhibits an insulator-to-metal transition near a ferromagnetic phase transition temperature. This yields a very large magnetoresistance; thus these materials may have important uses as magnetic sensors in a variety of applications, ranging from automobiles to read heads for magnetic storage. In addition, the transport current in the ferromagnetic state is likely to be very highly polarized, which means that additional device applications using the phenomena of spin-polarized tunneling can be envisioned. Use of these materials as magnetic sensors depends upon learning to control the synthesis parameters (principally temperature, pressure and composition) to achieve a specific carrier concentration and/or mobility. A second challenge is the high magnetic fields ({ge}1 Tesla) currently required to achieve a large change in resistance. The authors began an investigation of two novel approaches to this field-sensitivity problem, involving the development of multilayer structures of the TMO materials. Finally, they began to explore the use of epitaxial strain as a means of changing the transport properties in thin-film multilayers.

  16. Classical and quantum routes to linear magnetoresistance.

    PubMed

    Hu, Jingshi; Rosenbaum, T F

    2008-09-01

    The hallmark of materials science is the ability to tailor the microstructure of a given material to provide a desired response. Carbon mixed with iron provides the steel of buildings and bridges; impurities sprinkled in silicon single crystals form the raw materials of the electronics revolution; pinning centres in superconductors let them become powerful magnets. Here, we show that either adding a few parts per million of the proper chemical impurities to indium antimonide, a well-known semiconductor, or redesigning the material's structure on the micrometre scale, can transform its response to an applied magnetic field. The former approach is purely quantum mechanical; the latter a classical outgrowth of disorder, turned to advantage. In both cases, the magnetoresistive response--at the heart of magnetic sensor technology--can be converted to a simple, large and linear function of field that does not saturate. Harnessing the effects of disorder has the further advantage of extending the useful applications range of such a magnetic sensor to very high temperatures by circumventing the usual limitations imposed by phonon scattering. PMID:18719705

  17. Optimization of magneto-resistive response of ion-irradiated exchange biased films through zigzag arrangement of magnetization

    SciTech Connect

    Trützschler, Julia; Sentosun, Kadir; McCord, Jeffrey; Langer, Manuel; Fassbender, Jürgen; Mönch, Ingolf; Mattheis, Roland

    2014-03-14

    Exchange coupled ferromagnetic-antiferromagnetic Ni{sub 81}Fe{sub 19}/Ir{sub 23}Mn{sub 77} films with a zigzag alignment of magnetization are prepared by local ion irradiation. The anisotropic magneto-resistive behavior of the magnetic thin film structures is correlated to the magnetic structure and modeled. A unique uniaxial field sensitivity along the net magnetization alignment is obtained through the orthogonally modulated and magnetic domain wall stabilized magnetic ground state. Controlling local thin film magnetization distributions and, thus, the overall magnetization response opens unique ways to tailor the magneto-resistive sensitivity of functional magnetic thin film devices.

  18. Giant tunneling magnetoresistance in silicene

    SciTech Connect

    Wang, Yu; Lou, Yiyi

    2013-11-14

    We have theoretically studied ballistic electron transport in silicene under the manipulation of a pair of ferromagnetic gate. Transport properties like transmission and conductance have been calculated by the standard transfer matrix method for parallel and antiparallel magnetization configurations. It is demonstrated here that, due to the stray field-induced wave-vector filtering effect, remarkable difference in configuration-dependent transport gives rise to a giant tunneling magnetoresistance. In combination with the peculiar buckled structure of silicene and its electric tunable energy gap, the receiving magnetoresistance can be efficiently modulated by the externally-tunable stray field, electrostatic potential, and staggered sublattice potential, providing some flexible strategies to construct silicene-based nanoelectronic device.

  19. Giant magnetoresistance in nanogranular magnets.

    SciTech Connect

    Glatz, A.; Beloborodov, I. S.; Vinokur, V. M.; Materials Science Division; Univ. of Chicago

    2008-05-01

    We study the giant magnetoresistance of nanogranular magnets in the presence of an external magnetic field and finite temperature. We show that the magnetization of arrays of nanogranular magnets has hysteretic behavior at low temperatures leading to a double peak in the magnetoresistance which coalesces at high temperatures into a single peak. We numerically calculate the magnetization of magnetic domains and the motion of domain walls in this system using a combined mean-field approach and a model for an elastic membrane moving in a random medium, respectively. From the obtained results, we calculate the electric resistivity as a function of magnetic field and temperature. Our findings show excellent agreement with various experimental data.

  20. Landau levels and longitudinal magnetoresistance in generalized Weyl semimetals

    NASA Astrophysics Data System (ADS)

    Li, Xiao; Roy, Bitan

    The notion of axial anomaly is a venerable concept in quantum field theory that has received ample attention in condensed matter physics due to the discovery of Weyl materials (WSMs). In such systems Kramers non-degenerate bands touch at isolated points in the Brillouin zone that act as (anti)monopoles of Berry flux, and the monopole number (m) defines the topological invariant of the system. Although so far only simple WSMs (with m = 1) has been found in various inversion and/or time-reversal asymmetric systems, generalized Weyl semimetals with m > 1 can also be found in nature, for example double-Weyl semimetals in HgCr2Se4 and SrSi2 and triple-Weyl semimetals. In this work, we demonstrate the Landau level spectrum in generalized Weyl systems and its ramification on longitudinal magnetotransport measurements. We show that in the quantum limit generalized Weyl semimetals display negative longitudinal magnetoresistance due to the chiral anomaly. Moreover, the magnetoresistance has nontrivial dependence on the relative orientation of the external fields with the crystallographic axis, stemming from underlying anisotropic quasiparticle dispersion in the pristine system. Our theory can thus provide diagnostic tools to pin the quasiparticle properties in Weyl systems.

  1. Angle Dependence of the Orbital Magnetoresistance in Bismuth

    NASA Astrophysics Data System (ADS)

    Collaudin, Aurélie; Fauqué, Benoît; Fuseya, Yuki; Kang, Woun; Behnia, Kamran

    2015-04-01

    We present an extensive study of angle-dependent transverse magnetoresistance in bismuth, with a magnetic field perpendicular to the applied electric current and rotating in three distinct crystallographic planes. The observed angular oscillations are confronted with the expectations of semiclassic transport theory for a multivalley system with anisotropic mobility and the agreement allows us to quantify the components of the mobility tensor for both electrons and holes. A quadratic temperature dependence is resolved. As Hartman argued long ago, this indicates that inelastic resistivity in bismuth is dominated by carrier-carrier scattering. At low temperature and high magnetic field, the threefold symmetry of the lattice is suddenly lost. Specifically, a 2 π /3 rotation of magnetic field around the trigonal axis modifies the amplitude of the magnetoresistance below a field-dependent temperature. By following the evolution of this anomaly as a function of temperature and magnetic field, we map the boundary in the (field, temperature) plane separating two electronic states. In the less symmetric state, confined to low temperature and high magnetic field, the three Dirac valleys cease to be rotationally invariant. We discuss the possible origins of this spontaneous valley polarization, including a valley-nematic scenario.

  2. Scanning magnetoresistive microscopy: An advanced characterization tool for magnetic nanosystems

    NASA Astrophysics Data System (ADS)

    Mitin, D.; Grobis, M.; Albrecht, M.

    2016-02-01

    An advanced scanning magnetoresistive microscopy (SMRM) — a robust magnetic imaging and probing technique — will be presented, which utilizes state-of-the-art recording heads of a hard disk drive as sensors. The spatial resolution of modern tunneling magnetoresistive sensors is nowadays comparable to the more commonly used magnetic force microscopes. Important advantages of SMRM are the ability to detect pure magnetic signals directly proportional to the out-of-plane magnetic stray field, negligible sensor stray fields, and the ability to apply local bipolar magnetic field pulses up to 10 kOe with bandwidths from DC up to 1 GHz. Moreover, the SMRM can be further equipped with a heating stage and external magnetic field units. The performance of this method and corresponding best practices are demonstrated by presenting various examples, including a temperature dependent recording study on hard magnetic L10 FeCuPt thin films, imaging of magnetic vortex states in an in-plane magnetic field, and their controlled manipulation by applying local field pulses.

  3. Scanning magnetoresistive microscopy: An advanced characterization tool for magnetic nanosystems.

    PubMed

    Mitin, D; Grobis, M; Albrecht, M

    2016-02-01

    An advanced scanning magnetoresistive microscopy (SMRM) - a robust magnetic imaging and probing technique - will be presented, which utilizes state-of-the-art recording heads of a hard disk drive as sensors. The spatial resolution of modern tunneling magnetoresistive sensors is nowadays comparable to the more commonly used magnetic force microscopes. Important advantages of SMRM are the ability to detect pure magnetic signals directly proportional to the out-of-plane magnetic stray field, negligible sensor stray fields, and the ability to apply local bipolar magnetic field pulses up to 10 kOe with bandwidths from DC up to 1 GHz. Moreover, the SMRM can be further equipped with a heating stage and external magnetic field units. The performance of this method and corresponding best practices are demonstrated by presenting various examples, including a temperature dependent recording study on hard magnetic L1(0) FeCuPt thin films, imaging of magnetic vortex states in an in-plane magnetic field, and their controlled manipulation by applying local field pulses. PMID:26931856

  4. Magnetoresistance of galfenol-based magnetic tunnel junction

    NASA Astrophysics Data System (ADS)

    Gobaut, B.; Vinai, G.; Castán-Guerrero, C.; Krizmancic, D.; Rafaqat, H.; Roddaro, S.; Rossi, G.; Panaccione, G.; Eddrief, M.; Marangolo, M.; Torelli, P.

    2015-12-01

    The manipulation of ferromagnetic layer magnetization via electrical pulse is driving an intense research due to the important applications that this result will have on memory devices and sensors. In this study we realized a magnetotunnel junction in which one layer is made of Galfenol (Fe1-xGax) which possesses one of the highest magnetostrictive coefficient known. The multilayer stack has been grown by molecular beam epitaxy and e-beam evaporation. Optical lithography and physical etching have been combined to obtain 20x20 micron sized pillars. The obtained structures show tunneling conductivity across the junction and a tunnel magnetoresistance (TMR) effect of up to 11.5% in amplitude.

  5. Tunable angular-dependent magnetoresistance correlations in magnetic films and their implications for spin Hall magnetoresistance analysis

    NASA Astrophysics Data System (ADS)

    Zou, L. K.; Zhang, Y.; Gu, L.; Cai, J. W.; Sun, L.

    2016-02-01

    Angular-dependent magnetoresistance (MR) is considered to be intrinsic to spintronic materials, represented by the classical anisotropic MR (AMR) phenomenon and the recently emerged spin Hall MR (SMR). So far, isotropic AMR, AMR with geometric size effect and interfacial effect, and SMR have been treated separately to explain distinct MR correlations observed in various systems. Current study shows all four types of MR correlations can be reproduced in Fe thin films depending on the film thickness, texture, interface, and morphology. Results suggest previous explanations of the thin-film MR correlations are incomplete and it is inappropriate to use a specific MR angular-dependent correlation as the sole criterion in determining the origin of AMR or ascertaining the exclusive existence of SMR.

  6. Enhanced Magnetoresistance in Molecular Junctions by Geometrical Optimization of Spin-Selective Orbital Hybridization.

    PubMed

    Rakhmilevitch, David; Sarkar, Soumyajit; Bitton, Ora; Kronik, Leeor; Tal, Oren

    2016-03-01

    Molecular junctions based on ferromagnetic electrodes allow the study of electronic spin transport near the limit of spintronics miniaturization. However, these junctions reveal moderate magnetoresistance that is sensitive to the orbital structure at their ferromagnet-molecule interfaces. The key structural parameters that should be controlled in order to gain high magnetoresistance have not been established, despite their importance for efficient manipulation of spin transport at the nanoscale. Here, we show that single-molecule junctions based on nickel electrodes and benzene molecules can yield a significant anisotropic magnetoresistance of up to ∼200% near the conductance quantum G0. The measured magnetoresistance is mechanically tuned by changing the distance between the electrodes, revealing a nonmonotonic response to junction elongation. These findings are ascribed with the aid of first-principles calculations to variations in the metal-molecule orientation that can be adjusted to obtain highly spin-selective orbital hybridization. Our results demonstrate the important role of geometrical considerations in determining the spin transport properties of metal-molecule interfaces. PMID:26926769

  7. Static Magnetic Properties of Films Measured by Means of Angular Perturbative Magnetoresistance

    NASA Astrophysics Data System (ADS)

    Oliveira, Alexandre; Melo, Abner; da Costa, Ricardo; Chesman, Carlos

    In this work we introduced a new technique to measure magnetic anisotropies and magnetoelectrical properties, such as Anisotropic Magnetoresistance (AMR) and Giant Magnetoresistance (GMR) amplitudes. The Perturbative Magnetoresistance (PMR) consist of a regular collinear four probe magnetoresistance set up with an AC magnetic field (hac) applied perpendicular to the DC (Hdc) one. hac amplitude is about 1.0 Oe and oscillate at 270 Hz. We successfully interpreted the signal response from the voltage measured by lock-in amplifier and proposed a model based on energy minimization to extract magnetic anisotropies, AMR and GMR amplitudes. Measuring the in-plane angular dependency of PMR signal we were able to identify the usual magnetic anisotropy, such as uniaxial, unidirectional and cubic. Taking into account the perturbative nature of this technique (small hac amplitude and low frequency), we argue that angular PMR can be used to investigate some dynamic magnetic effects where static technique can not provide such information. A distinct feature of angular PMR is the capability to be used in saturated and non-saturated regime, so revealing magnetic properties dependency on applied field strength. We addressed the Rotatable Anisotropy as an example in this work.

  8. Hybrid Molecular and Spin Dynamics Simulations for Ensembles of Magnetic Nanoparticles for Magnetoresistive Systems

    PubMed Central

    Teich, Lisa; Schröder, Christian

    2015-01-01

    The development of magnetoresistive sensors based on magnetic nanoparticles which are immersed in conductive gel matrices requires detailed information about the corresponding magnetoresistive properties in order to obtain optimal sensor sensitivities. Here, crucial parameters are the particle concentration, the viscosity of the gel matrix and the particle structure. Experimentally, it is not possible to obtain detailed information about the magnetic microstructure, i.e., orientations of the magnetic moments of the particles that define the magnetoresistive properties, however, by using numerical simulations one can study the magnetic microstructure theoretically, although this requires performing classical spin dynamics and molecular dynamics simulations simultaneously. Here, we present such an approach which allows us to calculate the orientation and the trajectory of every single magnetic nanoparticle. This enables us to study not only the static magnetic microstructure, but also the dynamics of the structuring process in the gel matrix itself. With our hybrid approach, arbitrary sensor configurations can be investigated and their magnetoresistive properties can be optimized. PMID:26580623

  9. Room Temperature Giant and Linear Magnetoresistance in Topological Insulator Bi2Te3 Nanosheets

    NASA Astrophysics Data System (ADS)

    Wang, Xiaolin; Du, Yi; Dou, Shixue; Zhang, Chao

    2012-06-01

    Topological insulators, a new class of condensed matter having bulk insulating states and gapless metallic surface states, have demonstrated fascinating quantum effects. However, the potential practical applications of the topological insulators are still under exploration worldwide. We demonstrate that nanosheets of a Bi2Te3 topological insulator several quintuple layers thick display giant and linear magnetoresistance. The giant and linear magnetoresistance achieved is as high as over 600% at room temperature, with a trend towards further increase at higher temperatures, as well as being weakly temperature-dependent and linear with the field, without any sign of saturation at measured fields up to 13 T. Furthermore, we observed a magnetic field induced gap below 10 K. The observation of giant and linear magnetoresistance paves the way for 3D topological insulators to be useful for practical applications in magnetoelectronic sensors such as disk reading heads, mechatronics, and other multifunctional electromagnetic applications.

  10. Magnetotransport in metal/insulating-ferromagnet heterostructures: Spin Hall magnetoresistance or magnetic proximity effect

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Ma, L.; Shi, Z.; Fan, W. J.; Zheng, Jian-Guo; Evans, R. F. L.; Zhou, S. M.

    2015-08-01

    We study the anomalous Hall-like effect (AHLE) and the effective anisotropic magnetoresistance (EAMR) in antiferromagnetic γ -IrMn3/Y3Fe5O12(YIG ) and Pt/YIG heterostructures. For γ -IrMn3/YIG , the EAMR and the AHLE resistivity change sign with temperature due to the competition between the spin Hall magnetoresistance (SMR) and the magnetic proximity effect (MPE) induced by the interfacial antiferromagnetic uncompensated magnetic moment. In contrast, for Pt/YIG, the AHLE resistivity changes sign with temperature whereas no sign change is observed in the EAMR. This is because the MPE and the SMR play a dominant role in the AHLE and the EAMR, respectively. As different types of galvanomagnetic properties, the AHLE and the EAMR have proved vital in disentangling the MPE and the SMR in metal/insulating-ferromagnet heterostructures.

  11. Advanced Magnetoresistance Sensing of Rotation Rate for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Avram, Marioara; Volmer, Marius; Avram, Andrei

    2008-06-01

    We propose to build a non-Newtonian fluids viscosimeter, in order to measure the viscosity of biological fluids such as blood. The system is based on a rotating microgear wheel and a magnetoresistive sensor with a non-contacting transduction mechanism to transform the rotor rotation rate into an electrical signal. As the rotor turns, the field from this microscopic magnet will modulate the resistance of a bar of a low coercitivity material such as Permalloy, with an in-plane uniaxial magnetization, placed nearby, close to the rotor flanges. The change in resistivity provides an electrical signal with frequency proportional to the rotation rate, and hence the fluid velocity. The rotor is fabricated from polysilicon and coated with a soft magnetic material. The magnetoresistive sensor is formed of two Wheatstone bridges orientated on the X and Y axes. As the microgear wheel rotates, a tooth passing by the sensing GMR of the Wheatstone bridge changes the magnetic field, thus enabling us to measure the velocity of the gear wheel. The gear wheel has the outer diameter of 200 μm and is obtained by using the cut and refill technique. The basis for fabrication of movable parts is the use of sacrificial layers that act both as spacers and also to keep the parts attached to the silicon wafer during fabrication.

  12. Magnetic field sensor for isotropically sensing an incident magnetic field in a sensor plane

    NASA Technical Reports Server (NTRS)

    Pant, Bharat B. (Inventor); Wan, Hong (Inventor)

    2001-01-01

    A magnetic field sensor that isotropically senses an incident magnetic field. This is preferably accomplished by providing a magnetic field sensor device that has one or more circular shaped magnetoresistive sensor elements for sensing the incident magnetic field. The magnetoresistive material used is preferably isotropic, and may be a CMR material or some form of a GMR material. Because the sensor elements are circular in shape, shape anisotropy is eliminated. Thus, the resulting magnetic field sensor device provides an output that is relatively independent of the direction of the incident magnetic field in the sensor plane.

  13. Magnetoresistance Anisotropy in WTe2

    NASA Astrophysics Data System (ADS)

    Thoutam, Laxman Raju; Wang, Yonglei; Xiao, Zhili; Das, Saptarshi; Luican Mayer, Adina; Divan, Ralu; Crabtree, George W.; Kwok, Wai Kwong

    We report the angle dependence of the magnetoresistance in WTe2. Being a layered material, WTe2 is considered to be electronically two-dimensional (2D). Our results demonstrate that it is in fact 3D with an anisotropy of effective mass as small as 2. We measured the magnetic field dependence of the sample resistance R(H) at various angles between the applied magnetic field with respect to the c-axis of the crystal and found that they can be scaled based on the mass anisotropy, which changes from ~2 to ~5 with decreasing temperature in the Fermi liquid state. We will also discuss the origin of the turn-on temperature behavior in this material.

  14. Competing Mechanisms in Organic Magnetoresistance

    NASA Astrophysics Data System (ADS)

    Koopmans, Bert

    2013-03-01

    A surprisingly large ``organic magnetoresistance'' (OMAR) has been found in both polymers and small molecule organic semiconductors at relatively small applied magnetic fields (~ 5 mT) and at room temperature. Unlike spin-injection devices, where the occurrence of a finite spin polarization of the current is essential for measuring a finite magnetoresistance, OMAR is generally considered to be due to spin correlations between spin carrying particles in the organic material. Although the microscopic mechanisms of hyperfine field induced spin mixing are relatively well understood, it is still intensively debated which particles are involved and how they can affect the current in such a drastic manner. In this presentation recent developments and new insights as to the underlying physics are discussed. Quantitative models will be introduced, based on different pairs of particles and mechanisms, and giving rise to effects at a variety of field scales. It will be discussed how specific device physics causes a non-trivial relation between microscopic spin-dependent reactions and macroscopic device behaviour. Finally, it will be shown how comprehensive studies on especially engineered organic systems, including polymer-fullerene blends and molecular doping, can be used to pinpoint the relevance of different mechanisms in the complementary regimes. The experimentally observed linewidth, sign and amplitude of both ``high-field'' (>100 mT) and ``low-field'' (~ 5 mT) effects, as well as their bias voltage dependence display very pronounced features as a function of fullerene doping. They provide unique fingerprints for which mechanism is of relevance. After careful analysis, this allows for identification of three earlier proposed mechanisms, involving exciton-charge, electron-hole and bipolaron (polarons of like charge) reactions. Present activities are aiming at using this insight for tailoring OMAR response by design.

  15. Large rectification magnetoresistance in nonmagnetic Al/Ge/Al heterojunctions

    NASA Astrophysics Data System (ADS)

    Zhang, Kun; Li, Huan-Huan; Grünberg, Peter; Li, Qiang; Ye, Sheng-Tao; Tian, Yu-Feng; Yan, Shi-Shen; Lin, Zhao-Jun; Kang, Shi-Shou; Chen, Yan-Xue; Liu, Guo-Lei; Mei, Liang-Mo

    2015-09-01

    Magnetoresistance and rectification are two fundamental physical properties of heterojunctions and respectively have wide applications in spintronics devices. Being different from the well known various magnetoresistance effects, here we report a brand new large magnetoresistance that can be regarded as rectification magnetoresistance: the application of a pure small sinusoidal alternating-current to the nonmagnetic Al/Ge Schottky heterojunctions can generate a significant direct-current voltage, and this rectification voltage strongly varies with the external magnetic field. We find that the rectification magnetoresistance in Al/Ge Schottky heterojunctions is as large as 250% at room temperature, which is greatly enhanced as compared with the conventional magnetoresistance of 70%. The findings of rectification magnetoresistance open the way to the new nonmagnetic Ge-based spintronics devices of large rectification magnetoresistance at ambient temperature under the alternating-current due to the simultaneous implementation of the rectification and magnetoresistance in the same devices.

  16. Sensitive giant magnetoresistive-based immunoassay for multiplex mycotoxin detection.

    PubMed

    Mak, Andy C; Osterfeld, Sebastian J; Yu, Heng; Wang, Shan X; Davis, Ronald W; Jejelowo, Olufisayo A; Pourmand, Nader

    2010-03-15

    Rapid and multiplexed measurement is vital in the detection of food-borne pathogens. While highly specific and sensitive, traditional immunochemical assays such as enzyme-linked immunosorbent assays (ELISAs) often require expensive read-out equipment (e.g. fluorescent labels) and lack the capability of multiplex detection. By combining the superior specificity of immunoassays with the sensitivity and simplicity of magnetic detection, we have developed a novel multiplex magnetic nanotag-based detection platform for mycotoxins that functions on a sub-picomolar concentration level. Unlike fluorescent labels, magnetic nanotags (MNTs) can be detected with inexpensive giant magnetoresistive (GMR) sensors such as spin-valve sensors. In the system presented here, each spin-valve sensor has an active area of 90 microm x 90 microm, arranged in an 8 x 8 array. Sample is added to the antibody-immobilized sensor array prior to the addition of the biotinylated detection antibody. The sensor response is recorded in real time upon the addition of streptavidin-linked MNTs on the chip. Here we demonstrate the simultaneous detection of multiple mycotoxins (aflatoxins B(1), zearalenone and HT-2) and show that a detection limit of 50 pg/mL can be achieved. PMID:20047828

  17. Tunable magnetoresistance in an asymmetrically coupled single-molecule junction.

    PubMed

    Warner, Ben; El Hallak, Fadi; Prüser, Henning; Sharp, John; Persson, Mats; Fisher, Andrew J; Hirjibehedin, Cyrus F

    2015-03-01

    Phenomena that are highly sensitive to magnetic fields can be exploited in sensors and non-volatile memories. The scaling of such phenomena down to the single-molecule level may enable novel spintronic devices. Here, we report magnetoresistance in a single-molecule junction arising from negative differential resistance that shifts in a magnetic field at a rate two orders of magnitude larger than Zeeman shifts. This sensitivity to the magnetic field produces two voltage-tunable forms of magnetoresistance, which can be selected via the applied bias. The negative differential resistance is caused by transient charging of an iron phthalocyanine (FePc) molecule on a single layer of copper nitride (Cu2N) on a Cu(001) surface, and occurs at voltages corresponding to the alignment of sharp resonances in the filled and empty molecular states with the Cu(001) Fermi energy. An asymmetric voltage-divider effect enhances the apparent voltage shift of the negative differential resistance with magnetic field, which inherently is on the scale of the Zeeman energy. These results illustrate the impact that asymmetric coupling to metallic electrodes can have on transport through molecules, and highlight how this coupling can be used to develop molecular spintronic applications. PMID:25622229

  18. Magnetoresistance in Boron Carbide junctions

    NASA Astrophysics Data System (ADS)

    Day, Ellen; Sokolov, A.; Baruth, A.; Robertson, B. W.; Adenwalla, S.

    2007-03-01

    The properties of thin insulator layers are crucial to the performance of magnetic tunnel junctions. Commercial requirements are a device with a high tunnel magnetoresistance (TMR) with low cost and high stability. At present the vast majority of barriers are made from amorphous Al2O3 and crystalline MgO. The TMR value depends not only on the spin-dependent electronic structure of the electrodes, but on the metal-insulator interface. Oxide-type barriers may suffer from local vacancies and other type of defects, resulting in oxygen diffusion, making the TMR value unstable with time. We present TMR results obtained on a non-oxide barrier, boron carbide (B10C2) for applications in magnetic tunnel junctions. This low Z inorganic material can be grown by plasma enhanced chemical vapor deposition (PECVD) without pinholes in the ultra thin film regime. PECVD grown boron carbide is an excellent dielectric with resistivities in the range of 10^7 ohm-cm, with a band gap that can be adjusted from 0.7 eV to 1.9 eV by altering the boron to carbon ratio and to band gap values well above 2.7 eV by adding phosphorus. This creates a unique opportunity for experimental study of a broad spectrum of phenomena, related to the dielectric properties of the barrier.

  19. Tunneling magnetoresistive heads for magnetic data storage.

    PubMed

    Mao, Sining

    2007-01-01

    Spintronics is emerging to be a new form of nanotechnologies, which utilizes not only the charge but also spin degree of freedom of electrons. Spin-dependent tunneling transport is one of the many kinds of physical phenomena involving spintronics, which has already found industrial applications. In this paper, we first provide a brief review on the basic physics and materials for magnetic tunnel junctions, followed more importantly by a detailed coverage on the application of magnetic tunneling devices in magnetic data storage. The use of tunneling magnetoresistive reading heads has helped to maintain a fast growth of areal density, which is one of the key advantages of hard disk drives as compared to solid-state memories. This review is focused on the first commercial tunneling magnetoresistive heads in the industry at an areal density of 80 approximately 100 Gbit/in2 for both laptop and desktop Seagate hard disk drive products using longitudinal media. The first generation tunneling magnetoresistive products utilized a bottom stack of tunnel junctions and an abutted hard bias design. The output signal amplitude of these heads was 3 times larger than that of comparable giant magnetoresistive devices, resulting in a 0.6 decade bit error rate gain over the latter. This has enabled high component and drive yields. Due to the improved thermal dissipation of vertical geometry, the tunneling magnetoresistive head runs cooler with a better lifetime performance, and has demonstrated similar electrical-static-discharge robustness as the giant magnetoresistive devices. It has also demonstrated equivalent or better process and wafer yields compared to the latter. The tunneling magnetoresistive heads are proven to be a mature and capable reader technology. Using the same head design in conjunction with perpendicular recording media, an areal density of 274 Gbit/in2 has been demonstrated, and advanced tunneling magnetoresistive heads can reach 311 Gbit/in2. Today, the

  20. Temperature-Dependent Three-Dimensional Anisotropy of the Magnetoresistance in WTe2

    NASA Astrophysics Data System (ADS)

    Thoutam, L. R.; Wang, Y. L.; Xiao, Z. L.; Das, S.; Luican-Mayer, A.; Divan, R.; Crabtree, G. W.; Kwok, W. K.

    2015-07-01

    Extremely large magnetoresistance (XMR) was recently discovered in WTe2 , triggering extensive research on this material regarding the XMR origin. Since WTe2 is a layered compound with metal layers sandwiched between adjacent insulating chalcogenide layers, this material has been considered to be electronically two-dimensional (2D). Here we report two new findings on WTe2 : (1) WTe2 is electronically 3D with a mass anisotropy as low as 2, as revealed by the 3D scaling behavior of the resistance R (H ,θ )=R (ɛθH ) with ɛθ=(cos2θ +γ-2sin2θ )1 /2 , θ being the magnetic field angle with respect to the c axis of the crystal and γ being the mass anisotropy and (2) the mass anisotropy γ varies with temperature and follows the magnetoresistance behavior of the Fermi liquid state. Our results not only provide a general scaling approach for the anisotropic magnetoresistance but also are crucial for correctly understanding the electronic properties of WTe2 , including the origin of the remarkable "turn-on" behavior in the resistance versus temperature curve, which has been widely observed in many materials and assumed to be a metal-insulator transition.

  1. Temperature-Dependent Three-Dimensional Anisotropy of the Magnetoresistance in WTe_{2}.

    PubMed

    Thoutam, L R; Wang, Y L; Xiao, Z L; Das, S; Luican-Mayer, A; Divan, R; Crabtree, G W; Kwok, W K

    2015-07-24

    Extremely large magnetoresistance (XMR) was recently discovered in WTe_{2}, triggering extensive research on this material regarding the XMR origin. Since WTe_{2} is a layered compound with metal layers sandwiched between adjacent insulating chalcogenide layers, this material has been considered to be electronically two-dimensional (2D). Here we report two new findings on WTe_{2}: (1) WTe_{2} is electronically 3D with a mass anisotropy as low as 2, as revealed by the 3D scaling behavior of the resistance R(H,θ)=R(ϵ_{θ}H) with ϵ_{θ}=(cos^{2}θ+γ^{-2}sin^{2}θ)^{1/2}, θ being the magnetic field angle with respect to the c axis of the crystal and γ being the mass anisotropy and (2) the mass anisotropy γ varies with temperature and follows the magnetoresistance behavior of the Fermi liquid state. Our results not only provide a general scaling approach for the anisotropic magnetoresistance but also are crucial for correctly understanding the electronic properties of WTe_{2}, including the origin of the remarkable "turn-on" behavior in the resistance versus temperature curve, which has been widely observed in many materials and assumed to be a metal-insulator transition. PMID:26252701

  2. Electronic structure basis for the extraordinary magnetoresistance in WTe2

    SciTech Connect

    Pletikosić, I.; Ali, Mazhar N.; Fedorov, A. V.; Cava, R. J.; Valla, T.

    2014-11-19

    The electronic structure basis of the extremely large magnetoresistance in layered non-magnetic tungsten ditelluride has been investigated by angle-resolved photoelectron spectroscopy. Hole and electron pockets of approximately the same size were found at the Fermi level, suggesting that carrier compensation should be considered the primary source of the effect. The material exhibits a highly anisotropic, quasi one-dimensional Fermi surface from which the pronounced anisotropy of the magnetoresistance follows. As a result, a change in the Fermi surface with temperature was found and a high-density-of-states band that may take over conduction at higher temperatures and cause the observed turn-on behavior of the magnetoresistance in WTe₂ was identified.

  3. Spin Hall magnetoresistance at high temperatures

    SciTech Connect

    Uchida, Ken-ichi; Qiu, Zhiyong; Kikkawa, Takashi; Iguchi, Ryo; Saitoh, Eiji

    2015-02-02

    The temperature dependence of spin Hall magnetoresistance (SMR) in Pt/Y{sub 3}Fe{sub 5}O{sub 12} (YIG) bilayer films has been investigated in a high temperature range from room temperature to near the Curie temperature of YIG. The experimental results show that the magnitude of the magnetoresistance ratio induced by the SMR monotonically decreases with increasing the temperature and almost disappears near the Curie temperature. We found that, near the Curie temperature, the temperature dependence of the SMR in the Pt/YIG film is steeper than that of a magnetization curve of the YIG; the critical exponent of the magnetoresistance ratio is estimated to be 0.9. This critical behavior of the SMR is attributed mainly to the temperature dependence of the spin-mixing conductance at the Pt/YIG interface.

  4. Magnetoresistance of galfenol-based magnetic tunnel junction

    SciTech Connect

    Gobaut, B.; Vinai, G.; Castán-Guerrero, C.; Krizmancic, D.; Panaccione, G.; Torelli, P.; Rafaqat, H.; Roddaro, S.; Rossi, G.; Eddrief, M.; Marangolo, M.

    2015-12-15

    The manipulation of ferromagnetic layer magnetization via electrical pulse is driving an intense research due to the important applications that this result will have on memory devices and sensors. In this study we realized a magnetotunnel junction in which one layer is made of Galfenol (Fe{sub 1-x}Ga{sub x}) which possesses one of the highest magnetostrictive coefficient known. The multilayer stack has been grown by molecular beam epitaxy and e-beam evaporation. Optical lithography and physical etching have been combined to obtain 20x20 micron sized pillars. The obtained structures show tunneling conductivity across the junction and a tunnel magnetoresistance (TMR) effect of up to 11.5% in amplitude.

  5. Dynamic Vehicle Detection via the Use of Magnetic Field Sensors

    PubMed Central

    Markevicius, Vytautas; Navikas, Dangirutis; Zilys, Mindaugas; Andriukaitis, Darius; Valinevicius, Algimantas; Cepenas, Mindaugas

    2016-01-01

    The vehicle detection process plays the key role in determining the success of intelligent transport management system solutions. The measurement of distortions of the Earth’s magnetic field using magnetic field sensors served as the basis for designing a solution aimed at vehicle detection. In accordance with the results obtained from research into process modeling and experimentally testing all the relevant hypotheses an algorithm for vehicle detection using the state criteria was proposed. Aiming to evaluate all of the possibilities, as well as pros and cons of the use of anisotropic magnetoresistance (AMR) sensors in the transport flow control process, we have performed a series of experiments with various vehicles (or different series) from several car manufacturers. A comparison of 12 selected methods, based on either the process of determining the peak signal values and their concurrence in time whilst calculating the delay, or by measuring the cross-correlation of these signals, was carried out. It was established that the relative error can be minimized via the Z component cross-correlation and Kz criterion cross-correlation methods. The average relative error of vehicle speed determination in the best case did not exceed 1.5% when the distance between sensors was set to 2 m. PMID:26797615

  6. Dynamic Vehicle Detection via the Use of Magnetic Field Sensors.

    PubMed

    Markevicius, Vytautas; Navikas, Dangirutis; Zilys, Mindaugas; Andriukaitis, Darius; Valinevicius, Algimantas; Cepenas, Mindaugas

    2016-01-01

    The vehicle detection process plays the key role in determining the success of intelligent transport management system solutions. The measurement of distortions of the Earth's magnetic field using magnetic field sensors served as the basis for designing a solution aimed at vehicle detection. In accordance with the results obtained from research into process modeling and experimentally testing all the relevant hypotheses an algorithm for vehicle detection using the state criteria was proposed. Aiming to evaluate all of the possibilities, as well as pros and cons of the use of anisotropic magnetoresistance (AMR) sensors in the transport flow control process, we have performed a series of experiments with various vehicles (or different series) from several car manufacturers. A comparison of 12 selected methods, based on either the process of determining the peak signal values and their concurrence in time whilst calculating the delay, or by measuring the cross-correlation of these signals, was carried out. It was established that the relative error can be minimized via the Z component cross-correlation and Kz criterion cross-correlation methods. The average relative error of vehicle speed determination in the best case did not exceed 1.5% when the distance between sensors was set to 2 m. PMID:26797615

  7. Current-perpendicular-to-the-plane giant magnetoresistance in spin-valves with AgSn alloy spacers

    SciTech Connect

    Read, J. C.; Nakatani, T. M.; Smith, Neil; Choi, Y.-S.; York, B. R.; Brinkman, E.; Childress, J. R.

    2015-07-28

    We investigate the use of AgSn alloys as the spacer layer in current-perpendicular-to-the-plane magnetoresistance devices. Alloying with Sn increases resistivity but results in a reasonably long (>10 nm) spin-diffusion length, so large magnetoresistance can be achieved with thin AgSn spacers. Compared to Ag thin films, AgSn forms smaller grain sizes, reduced roughness, and exhibits less interdiffusion upon annealing, resulting in decreased interlayer magnetic coupling in exchange biased spin-valves. AgSn also shows improved corrosion resistance compared to Ag, which is advantageous for nanofabrication, including magnetic recording head sensors. Combining a AgSn spacer with Co-based Heusler alloy ferromagnet in an exchange biased, polycrystalline trilayer thinner than 12 nm results in magnetoresistance values up to 15% at room temperature.

  8. Current-perpendicular-to-the-plane giant magnetoresistance in spin-valves with AgSn alloy spacers

    NASA Astrophysics Data System (ADS)

    Read, J. C.; Nakatani, T. M.; Smith, Neil; Choi, Y.-S.; York, B. R.; Brinkman, E.; Childress, J. R.

    2015-07-01

    We investigate the use of AgSn alloys as the spacer layer in current-perpendicular-to-the-plane magnetoresistance devices. Alloying with Sn increases resistivity but results in a reasonably long (>10 nm) spin-diffusion length, so large magnetoresistance can be achieved with thin AgSn spacers. Compared to Ag thin films, AgSn forms smaller grain sizes, reduced roughness, and exhibits less interdiffusion upon annealing, resulting in decreased interlayer magnetic coupling in exchange biased spin-valves. AgSn also shows improved corrosion resistance compared to Ag, which is advantageous for nanofabrication, including magnetic recording head sensors. Combining a AgSn spacer with Co-based Heusler alloy ferromagnet in an exchange biased, polycrystalline trilayer thinner than 12 nm results in magnetoresistance values up to 15% at room temperature.

  9. Single molecule actuation and detection on a lab-on-a-chip magnetoresistive platform

    NASA Astrophysics Data System (ADS)

    Chaves, R. C.; Bensimon, D.; Freitas, P. P.

    2011-03-01

    On-chip magnetic tweezers based on current loops were integrated with magnetoresistive sensors. Magnetic forces up to 1.0±0.3pN are produced to actuate on DNA anchored to the surface of a flow cell and labeled with micrometer-sized magnetic beads. The levitation of the beads stretches the immobilized DNA. The relative position of the magnetic beads is monitored using spin-valve sensors. A bead vertical displacement resolution of 60nm is derived for DNA molecular motor activity in a tweezer steady current regime.

  10. Large magnetoresistance in non-magnetic silver chalcogenides and new class of magnetoresistive compounds

    DOEpatents

    Saboungi, Marie-Louis; Price, David C. L.; Rosenbaum, Thomas F.; Xu, Rong; Husmann, Anke

    2001-01-01

    The heavily-doped silver chalcogenides, Ag.sub.2+.delta. Se and Ag.sub.2+.delta. Te, show magnetoresistance effects on a scale comparable to the "colossal" magnetoresistance (CMR) compounds. Hall coefficient, magnetoconductivity, and hydrostatic pressure experiments establish that elements of narrow-gap semiconductor physics apply, but both the size of the effects at room temperature and the linear field dependence down to fields of a few Oersteds are surprising new features.