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1

Negative g factors, berry phases, and magnetic properties of complexes.  

PubMed

It is shown that the sign of the product of three Zeeman splitting factors corresponding to the main magnetic axes defines the sign of the Berry phase of a (pseudo) spin in an applied magnetic field. Ab initio calculations show that g(X)g(Y)g(Z)< 0 is often the case for lanthanide and transition metal complexes, while we prove that it is never achieved in S complexes with dominant second-order magnetic anisotropy. In the case of polynuclear compounds, it is argued that the signs of individual g(i), i=X, Y, Z, on each metal site can be extracted from experiment. PMID:23368351

Chibotaru, L F; Ungur, L

2012-12-14

2

High performance first principles method for complex magnetic properties  

Microsoft Academic Search

The understanding of metallic magnetism is of fundamental importance for a wide range of technological applications ranging from thin film disc drive read heads to bulk magnets used in motors and power generation. In this submission for the Gordon Bell Prize we use the power of massively parallel processing (MPP) computers to perform first principles calculations of large system models

B. Ujfalussy; Xindong Wang; Xiaoguang Zhang; D. M. C. Nicholson; W. A. Shelton; G. M. Stocks; A. Canning; Yang Wang; B. L. Gyorffy

1998-01-01

3

Magnetic and transport properties of Co-Si-B metallic glasses with complex dopants  

NASA Astrophysics Data System (ADS)

The structure, magnetic and resistivity characteristics of Co-Si-B metallic glasses containing complex dopants have been investigated. The intervals of thermal stability of the phases existing in the alloys studied have been determined. The temperature dependences of the resistivity were shown to be essentially nonlinear up to a certain temperature, evidencing for the contribution of several scattering mechanisms. Magnetic and resistivity behavior of these alloys are substantially governed by the phase separation within the region of the amorphous state stability and magnetic clusters formation. In the as-cast alloys these clusters are estimated to contain 2-4 Co atoms. Heat treatment significantly affects the structure and magnetic properties. It leads to increase of the Curie temperature and localized magnetic moment, whereas the crystallization temperature remains almost invariable.

Yarmoshchuk, Yevhenii I.; Nakonechna, Olesya I.; Semenko, Mykhailo P.; Zakharenko, Mykola I.

2014-10-01

4

Coupling strategies to enhance single-molecule magnet properties of erbium-cyclooctatetraenyl complexes.  

PubMed

Two different coupling strategies were employed to create Er(III) single-molecule magnets (SMMs) using high blocking temperature mononuclear precursors. The magnetic properties of three lanthanide-COT complexes, [Er(III)2(COT'')3] (1) (COT'' = 1,4-bis(trimethylsilyl)cyclooctatetraenyl dianion) and K2(THF)4[Ln(III)2(COT)4] (Ln = Gd (2), Er (3); THF = tetrahydrofuran, COT = cyclooctatetraenyl dianion), are reported. Both Er(III) complexes behave as SMMs and exhibit magnetic hysteresis at 12 K in solid state. In solution compound 1 exhibits hysteresis up to 14 K. Ac susceptibility data indicates a 100 s blocking temperature of 12.5 and 12.9 K for [Er(III)2(COT'')3] and K2(THF)4[Er(III)2(COT)4], respectively. Both Er(III) dimers display enhanced SMM properties over their mononuclear analogues due to their linear structure and strictly axial anisotropy. A 4 K increase in the magnetic blocking temperature of [Er(III)2(COT'')3] over the double-decker analogue is attributed to an additional mechanism of magnetization blocking arising from exchange coupling between Er(III) ions. PMID:24805804

Le Roy, Jennifer J; Ungur, Liviu; Korobkov, Ilia; Chibotaru, Liviu F; Murugesu, Muralee

2014-06-01

5

Magnetic properties of variably serpentinized peridotites and their implication for the evolution of oceanic core complexes  

NASA Astrophysics Data System (ADS)

of ultramafic rocks during hydrothermal alteration at mid-ocean ridges profoundly changes the physical, chemical, rheological, and magnetic properties of the oceanic lithosphere. There is renewed interest in this process following the discovery of widespread exposures of serpentinized mantle on the seafloor in slow spreading oceans. Unroofing of mantle rocks in these settings is achieved by displacement along oceanic detachment faults, which eventually results in structures known as oceanic core complexes (OCCs). However, we have limited understanding of the mechanisms of serpentinization at the seafloor and in particular their relationship with the evolution of OCCs. Since magnetite is a direct product of serpentinization, the magnetic properties of variably serpentinized peridotites can provide unique insights into these mechanisms and their evolution in the oceanic lithosphere. Here we present new results from an integrated, rock magnetic, paleomagnetic, and petrological study of variably serpentinized peridotites from the first fossil OCC recognized in an ophiolite. Integration with existing data from mid-ocean ridge-related abyssal peridotites recovered from several scientific ocean drilling sites yields the first magnetic database from peridotites extending across the complete range (0-100%) of degrees of serpentinization. Variations in a range of magnetic parameters with serpentinization, and associated paleomagnetic data, provide: (i) key constraints on the mechanism(s) of serpentinization at mid-ocean ridges; (ii) insights on the potential for serpentinized peridotites to contribute to marine magnetic anomalies; and (iii) evidence that leads to a new conceptual model for the evolution of serpentinization and related remanence acquisition at OCCs.

Maffione, Marco; Morris, Antony; Plümper, Oliver; van Hinsbergen, Douwe J. J.

2014-04-01

6

Magnetism and Magnetic Properties  

NSDL National Science Digital Library

Students will identify properties of magnetism and begin to develop understanding of their practical applications. Students will also begin to develop understanding of the essential nature of Earth's magnetic fields.

Schneck, Roberta

2011-10-13

7

Investigating the pharmacodynamic and magnetic properties of pyrophosphate-bridged coordination complexes  

NASA Astrophysics Data System (ADS)

The multidentate nature of pyrophosphate makes it an attractive ligand for complexation of metal cations. The participation of pyrophosphate in a variety of biological pathways and its metal catalyzed hydrolysis has driven our investigation into its coordination chemistry. We have successfully synthesized a library of binuclear pyrophosphate bridge coordination complexes. The problem of pyrophosphate hydrolysis to phosphate in the presence of divalent metal ions was overcome by incorporating capping ligands such as 1,10-phenanthroline and 2,2'-bipyridine prior to the addition of the pyrophosphate. The magnetic properties of these complexes was investigated and magneto-structural analysis was conducted. The biological abundance of pyrophosphate and the success of metal based drugs such as cisplatin, prompted our investigation of the cytotoxic properties of M(II) pyrophosphate dimeric complexes (where M(II) is CoII, CuII, and NiII) in adriamycin resistant human ovarian cancer cells. Thess compounds were found to exhibit toxicity in the nanomolar to picomolar range. We conducted in vitro stability studies and the mechanism of cytoxicity was elucidated by performing DNA mobility and binding assays, enzyme inhibition assays, and in vitro oxidative stress studies.

Ikotun, Oluwatayo (Tayo) F.

8

Selected spectroscopic and magnetic properties of lanthanide complexes in polyimide XU-218  

NASA Technical Reports Server (NTRS)

Polyimide XU-218 films containing approximately 5 wt pct of Eu(III), Gd(III), Tb(III), and Er(III) were prepared, and the effects of complexing each of the metals with the following four ligands were investigated: N-phenylphthalamate (NPPA), 2,4-pentanedionate (AcAc), 1,3-diphenyl 1,3-propanedionate (DBM), and a new hexa-aza-macrocyclic (MAC) ligand. The tris-chelated complexes of the mononegative ligands NPPA, AcAc, and DBM produced transparent, flexible films, which had magnetic and spectral properties very similar to those of the parent lanthanide complexes, while complexes of MAC showed problems due to the presence of lattice water and yielded dark brittle films. AcAc caused little or no effect on the glass transition temperature (Tg), while NPPA and DBM complexes lowered Tg to 269-290 C, and MAC indicated moisture by inflexion at 95-100 C with a true Tg at 320 C. All lanthanide-containing films were paramagnetic.

Stoakley, D. M.; Shillady, D. D.; Vallarino, L. M.; Gootee, W. A.; Smailes, D. L.

1987-01-01

9

Structural and magnetic properties of cobalt(II) complexes with pyridinecarboxamide ligands  

NASA Astrophysics Data System (ADS)

The synthesis and characterization of two new cobalt(II) coordination compounds with nicotinamide (nia) and isonicotinamide (isn) are reported. The products were characterized magnetically, structurally by single-crystal X-ray diffraction analysis and spectrally by FT-IR spectroscopy. Using the reaction of cobalt(II) acetate tetrahydrate and nicotinamide in methanol we obtained light-red crystals of the mononuclear complex [Co(nia)2(H2O)4](CH3COO)2·2H2O (1). The synthesis in a system cobalt(II) acetate dihydrathe, isonicotinamide and dimethylformamide-methanol mixture gave a new dinuclear coordination compound with the formula [Co2(CH3COO)4(isn)4]·2C3H7NO (2). In both compounds a trans arrangement of pyridinecarboxamide ligands was found. Intermolecular hydrogen bonds in the crystal structures of both complexes are discussed. The magnetic properties were studied between 2 K and 300 K giving the result ?eff = 4.6 BM for 1 and ?eff = 4.7 BM for 2 in the paramagnetic region.

Dojer, Brina; Pevec, Andrej; Belaj, Ferdinand; Jagli?i?, Zvonko; Kristl, Matjaž; Drofenik, Miha

2014-11-01

10

Luminescent, magnetic and ferroelectric properties of noncentrosymmetric chain-like complexes composed of nine-coordinate lanthanide ions.  

PubMed

Reaction of the chiral ligand (-)-4,5-pinenepyridyl-2-pyrazine (L) with Ln(hfac)3·2H2O precursors [hfac(-) = 1,1,1,5,5,5-hexafluoroacetylacetonate, Ln = Sm(3+) (1), Eu(3+) (2), Tb(3+) (3) and Dy(3+) (4)] in methanol solution led to the formation of four noncentrosymmetric lanthanide complexes with the general formula [Ln(hfac)3L]n·H2O. The single-crystal X-ray diffraction analyses revealed that they are isostructural and take a one-dimensional (1D) chain structure based on the Ln(hfac)3L repeating units, in which the nine-coordinate Ln(3+) ions reside in a tricapped trigonal prism (TTP) environment never reported in previous 1D chain lanthanide complexes. The investigations of their photophysical properties showed that complexes 1, and 3 exhibit characteristic emissions of Sm(3+), Eu(3+) and Tb(3+) ions with respective luminescent lifetime values of 0.065, 1.066 and 0.129 ms, while complex 4 does not display any emission. The different luminescent intensities and lifetimes among them were further discussed in detail. Moreover, the magnetic properties of complexes 1-4 were assessed with a special emphasis on the Dy(3+) complex 4. Alternating-current (ac) magnetic susceptibility measurements indicated that field-induced two-step slow magnetic relaxation processes were observed in 4, indicating the single-molecule magnet (SMM) behavior of 4. In addition, the noncentrosymmetric complexes 1-4 crystallizing in the same polar point group (Cs) exhibit both ferroelectric and nonlinear optical properties at room temperature. All these features make them multifunctional crystalline molecule materials. PMID:24002651

Li, Xi-Li; Chen, Chun-Lai; Xiao, Hong-Ping; Wang, Ai-Ling; Liu, Cai-Ming; Zheng, Xianjun; Gao, Li-Jun; Yang, Xiao-Gang; Fang, Shao-Ming

2013-11-21

11

Synthesis, structural analysis, and magnetic properties of ethylmalonate-manganese(II) complexes.  

PubMed

Five manganese(II) complexes of formulas [Mn(2)(Etmal)(2)(H(2)O)(2)(L)](n) (1-4) and {[Mn(Etmal)(2)(H(2)O)][Mn(H(2)O)(4)]}(n) (5) with H(2)Etmal = ethylmalonic acid (1-5) and L = 1,2-bis(4-pyridyl)ethane (bpa) (1), 4,4'-azobispyridine (azpy) (2), 4,4'-bipyridyl (4,4'-bpy) (3), and 1,2-bis(4-pyridyl)ethylene (bpe) (4) were synthesized and structurally characterized by single crystal X-ray diffraction. Their thermal behavior and variable-temperature magnetic properties were also investigated. The structure of the compounds 1-4 consists of corrugated layers of aquamanganese(II) units with intralayer carboxylate-ethylmalonate bridges in the anti-syn (equatorial-equatorial) coordination mode which are linked through bis-monodentate bpa (1), azpy (2), 4,4'-bpy (3), and bpe (4) ligands to build up a three-dimensional (3D) framework. The structure of compound 5 is made up by zigzag chains of manganese(II) ions with a regular alternation of [Mn(H(2)O)(4)](2+) and chiral (either ? or ? enantiomeric forms) [Mn(Etmal)(2)(H(2)O)](2-) units within each chain. In contrast to the bidentate/bis-monodentate coordination mode of the Etmal ligand in 1-4, it adopts the bidentate/monodentate coordination mode in 5 with the bridging carboxylate-ethylmalonate also exhibiting the anti-syn conformation but connecting one equatorial and an axial position from adjacent metal centers. The manganese-manganese separation through the carboxylate-ethylmalonate bridge in 1-5 vary in the range 5.3167(4)-5.5336(7) Å. These values are much shorter than those across the extended bis-monodentate N-donors in 1-4 with longest/shortest values of 11.682(3) (3)/13.9745(9) Å (4). Compounds 1-5 exhibit an overall antiferromagnetic behavior, where the exchange pathway is provided by the carboxylate-ethylmalonate bridge. Monte Carlo simulations based on the classical spin approach (1-5) were used to successfully reproduce the magnetic data of 1-5. PMID:21985395

Déniz, Mariadel; Pasán, Jorge; Ferrando-Soria, Jesús; Fabelo, Oscar; Cañadillas-Delgado, Laura; Yuste, Consuelo; Julve, Miguel; Cano, Joan; Ruiz-Pérez, Catalina

2011-11-01

12

Spectroscopic and magnetic properties of solvatochromic complex of Cu2+ and novel 3H-indolium derivative.  

PubMed

A new solvatochromic complex of copper (II) and 3H-indolium (HQIndol) with the formula (HQIndol)3Cu has been synthesised and characterised by elemental analysis, UV-vis, IR spectroscopies, electron paramagnetic resonance (EPR), and static magnetic susceptibility and conductance measurements. The stoichiometry of complex has been determined as 1:3 (M:L) and the binding constant was calculated to be 5.86×10(16) mol(-1) L at 25 °C in CH3OH. Magnetization measurements indicate that (HQIndol)3Cu sample is paramagnetic with spin S=1/2 for which phase transition from paramagnetic to antiferromagnetic has been registered at TN=2.5 K. The symmetry of the EPR spectrum points to elongated tetragonal octahedral geometry of the complex. Examined heterochelate exhibits solvatochromic properties. Blue shift of the vis absorption band with increased solvent polarity is observed, ???max in examined solvents amounts to 1466 cm(-1). PMID:24495838

G?siorowska, Monika; Typek, Janusz; Soroka, Jacek Adam; Sawicka, Marta Justyna; Wróblewska, Elwira Katarzyna; Guskos, Niko; ?o?nierkiewicz, Grzegorz

2014-04-24

13

Syntheses, structures and magnetic properties of heterobimetallic complexes based on a new tetracyanometalate precursor  

Microsoft Academic Search

A new mononuclear tetracyanometallic complex, (n-Bu4N)[(dbphen)Fe(CN)4] (1, dbphen=5,6-dibromo-1,10-phenanthroline), has been prepared by reacting [(dbphen)FeII(py)2(SCN)2] and KCN in water and further oxidized with chlorine. With the use of 1 as building block, two trinuclear Fe2M complexes, [(dbphen)2Fe2(CN)8Cu(Me3tacn)]·3H2O (2), [(dbphen)2Fe2(CN)8Ni(dabhctd)]·2H2O (3) and a chain complex of squares [(dbphen)2Fe2(CN)8Co(MeOH)2]n (4), have been synthesized and structurally characterized. Magnetic studies show ferromagnetic coupling between FeIII

Ling-Chen Kang; Xin Chen; Cai-Feng Wang; Xin-Hui Zhou; Jing-Lin Zuo; Xiao-Zeng You

2009-01-01

14

Synthesis, structure, magnetic properties and DNA cleavage of binuclear Cu(II) Schiff-base complexes.  

PubMed

Five binuclear Schiff base copper(ii) complexes [Cu(2)(L)(OAc)].3DMF (), [Cu(2)(L)(OAc)](2).3DMF (), [Cu(2)(L)(BNPP)].3CH(3)CN (), [Cu(2)(L)(Fa)].2DMF () and [Cu(2)(L)(Pa)].DMF () (H(3)L = N,N'-bis(3,5-tert-butylsalicylidene-2-hydroxy)-1,3-propanediamine, OAc = acetic acid, BNPP = bis(4-nitrophenyl)phosphate, Fa = 2-tetrahydrofuroic acid, Pa = benzoic acid) have been synthesized and characterized by X-ray single-crystal structure analysis. Variable-temperature magnetic susceptibility studies (2-300 K) indicate the existence of ferromagnetic coupling between the copper(ii) ions in complexes and , and antiferromagnetic coupling in complexes and . The interaction of these complexes with CT-DNA has been studied by using absorption and emission spectral methods. The apparent binding constant (K(app)) values for complexes , , and are 4.67 x 10(5), 9.48 x 10(5), 4.30 x 10(5) and 3.90 x 10(5) M(-1), respectively, which show that the complexes bind to DNA by moderate intercalative binding modes. Furthermore, all these complexes can cleave plasmid DNA to nicked DNA in a sequential manner as the concentrations or reaction times are increased in the absence of reducing agent. Their cleavage activities are promoted in the presence of hydrogen peroxide. The cleavage mechanisms between the complexes and plasmid DNA are likely to involve singlet oxygen (1)O(2) and OH as reactive oxygen species. PMID:19290371

Kou, Yingying; Tian, Jinlei; Li, Dongdong; Gu, Wen; Liu, Xin; Yan, Shiping; Liao, Daizheng; Cheng, Peng

2009-04-01

15

22-Azametallacrown-8 complex with a triazole-bridged ligand: synthesis, structure and magnetic properties.  

PubMed

Reaction of Mn(OAc)2·4H2O with the H2L ligand affords a new manganese 22-MC-8 azametallacrown [Mn8(?3-O)2(?3-OH)2(?2-OH)2(L)6(OAc)2(OH2)4]·2DMF (H2L = 3-(2-oxyphenyl)-5-(pyrazin-2-yl)-1,2,4-triazole). The structural analysis of the complex reveals that the azaMC ring possesses -[Mn-O-Mn-N-N-Mn-N-N-Mn-N-N]- connectivity. The magnetic behavior of the complex shows the dominant antiferromagnetic interactions between the manganese ions with S = 4 and the frequency-dependent out-of-phase signal. PMID:25315719

Yang, Hua; Yao, Qing-Xia; Li, Yun-Wu; Li, Da-Cheng; Dou, Jian-Min

2014-10-28

16

Scaling properties of composite information measures and shape complexity for hydrogenic atoms in parallel magnetic and electric fields  

NASA Astrophysics Data System (ADS)

The scaling properties of various composite information-theoretic measures (Shannon and Rényi entropy sums, Fisher and Onicescu information products, Tsallis entropy ratio, Fisher-Shannon product and shape complexity) are studied in position and momentum spaces for the non-relativistic hydrogenic atoms in the presence of parallel magnetic and electric fields. Such measures are found to be invariant at the fixed values of the scaling parameters given by s1={B?3(4}/{Z2m2e} and s2={F?4(4}/{Z3em2}. Numerical results which support the validity of the scaling properties are shown by choosing the representative example of the position space shape complexity. Physical significance of the resulting scaling behavior is discussed.

González-Férez, R.; Dehesa, J. S.; Patil, S. H.; Sen, K. D.

2009-12-01

17

Structural, Magnetic and Electronic Properties of the Sr2CoNbO6 Complex Perovskite  

NASA Astrophysics Data System (ADS)

We report a study of crystallographic parameters of the Sr2CoNbO6 double perovskite obtained from Rietveld analysis of X-ray diffraction data and electronic properties predictions using the density functional theory (DFT). The Sr2CoNbO6 material was prepared by the citrate precursor method. Diffraction analysis reveal that this material crystallizes in a structure which is tetragonal with lattice parameters a = 5.5960(3) Å and c = 7.9881(1) Å (space group I4/m). The density of states of Sr2CoNbO6 tetragonal distorted structure was calculated using DFT within the generalized gradient approximation. Results predict the semiconductor characteristics of this material which is majority due to the 3d-Co orbital with a energy gap of 0.2 eV. Structural lattice parameters obtained from the Rietveld refinement present a matching of 97% with that obtained from the Structure Prediction Diagnostic Software and 98% with the theoretical DFT results. Measurements of magnetization as a function of temperature evidence the occurrence of a magnetic ordering transition at T = 220 K and a marked irreversibility with a blocking temperature of 250 K for applied fields up to 100 Oe, which disappears for higher fields. Electronic paramagnetic resonance experiments evidence that the valence Co3+ is the most possible in the synthesized material.

Rendón Ramírez, J. M.; Almanza M., O. A.; Cardona, R.; Landínez Téllez, D. A.; Roa-Rojas, J.

2013-11-01

18

Magnetic properties of variably serpentinized peridotites and their implication for remanence acquisition during the evolution of oceanic core complexes  

NASA Astrophysics Data System (ADS)

Serpentinization of olivine-rich, mafic and ultramafic rocks during hydrothermal alteration is a process that profoundly changes the physical, rheological, magnetic and chemical properties of the oceanic lithosphere. There has recently been renewed interest in this process following the discovery that seafloor exposures of serpentinized upper mantle peridotites are widespread along modern slow- and ultra-slow-spreading ridges. One important mechanism for unroofing of mantle rocks in these settings is displacement along oceanic detachment fault systems, leading to the development of uplifted and rotated footwall sections known as oceanic core complexes (OCCs). However, difficulties inherent in direct sampling and observation of abyssal peridotites have limited our knowledge of the mechanisms of serpentinization, particularly during early stages of alteration. Hence, the progress of reactions with time, the amount, size and main features of reaction by-products (i.e. magnetite), and the progressive evolution of serpentinization at OCCs, remain only partially understood. Here we present the results of an integrated, rock magnetic, paleomagnetic and petrological study of 144 variably serpentinized peridotites from a recently documented fossil OCC preserved in the Mirdita ophiolite of Albania. Integration with existing data from peridotites recovered from several Deep Sea Drilling Project (DSDP) and Ocean Drilling Project (ODP) sites provides the first complete magnetic database for variably (0-100%) serpentinized peridotites. We show that major reactions and changes in magnetic properties occur at ~60% serpentinization, likely triggered by a dramatic permeability increase, and that the grain-size of newly formed magnetite increases progressively with serpentinization, leading to variation in the stability of components of magnetization acquired at different times. In the context of OCCs, we propose that serpentinization (and associated remanence acquisition) initiates at the detachment surface and migrates into the footwall during unroofing and tilting, potentially continuing once the OCC has become inactive. This conceptual model for the progression of serpentinization reconciles evidence that suggests that the timing of acquisition of serpentinization-related remanences relative to footwall rotation varies between different OCCs. In this model, rocks adjacent to the main detachment surface will acquire early-stage remanences that record substantial footwall rotation, whereas rocks deeper in the footwall may become magnetized after near or complete rotation.

maffione, M.; Morris, A.; Plümper, O.; Van Hinsbergen, D. J.

2013-12-01

19

Synthesis, crystal structure and magnetic properties of a nickel(III) maleonitriledithiolate complex using  

E-print Network

and dried under vacuum. Yield: 90% (Found: C, 57.98; H in the fields of conducting and magnetic materials, dyes, non-linear optics, catalysis and others [1Cl2$6H2O, Na2mnt and [MeBzBzim]I in H2O. A red precipitate given was filtered off, washed by water

Gao, Song

20

Relationships between Electron Density and Magnetic Properties in Water-Bridged Dimetal Complexes.  

PubMed

The electron densities in two analogous dimetallic transition metal compounds, namely, [M2(?-OH2)((t)BuCOO)4((t)BuCOOH)2(C5H5N)2] (M = Co(1), Ni(2)), were determined from combined X-ray and neutron single-crystal diffraction at 100 K. Excellent correspondence between the thermal parameters from X- and N-derived atomic displacement parameters is found, indicating high-quality X-ray data and a successful separation of thermal and electronic effects. Topological analysis of electron densities derived from high-resolution X-ray diffraction, as well as density functional theory calculations, shows no direct metal-metal bonding in either compound, while the total energy density at the bond critical points suggests stronger metal-oxygen interactions for the Ni system, in correspondence with its shorter bond distances. The analysis also allows for estimation of the relative strength of binding of terminal and bridging ligands to the metals, showing that the bridging water molecule is more strongly bound than terminal carboxylic acid, but less so than bridging carboxylates. Recently, modeling of magnetic and spectroscopic data in both of these systems has shown weak ferromagnetic interactions between the metal atoms. Factors related to large zero-field splitting effects complicate the magnetic analysis in both compounds, albeit to a much greater degree in 1. The current results support the conclusion drawn from previous magnetic and spectroscopic measurements that there is no appreciable direct communication between metal centers. PMID:25330274

Overgaard, Jacob; Walsh, James P S; Hathwar, Venkatesha R; Jørgensen, Mads R V; Hoffman, Christina; Platts, Jamie A; Piltz, Ross; Winpenny, Richard E P

2014-11-01

21

Syntheses, structures, and magnetic properties of heterobimetallic complexes based on tetracyanometallic building blocks  

Microsoft Academic Search

Two tetracyanometalate building blocks, [Fe(5,5?-dmbipy)(CN)4]? (2) and [Fe(4,4?-dmbipy)(CN)4]? (3) (5,5?-dmbipy=5,5?-dimethyl-2,2?-bipyridine; 4,4?-dmbipy=4,4?-dimethyl-2,2?-bipyridine), and two cyano-bridged heterobimetallic complexes, [Cu2(bpca)2(H2O)2Fe2(5,5?-dmbipy)2(CN)8]·2[Cu(bpca)Fe(5,5?-dmbipy)(CN)4]·4H2O (4) and [Cu(bpca)Fe(4,4?-dmbipy)(CN)4]n (5) (bpca=bis(2-pyridylcarbonyl)amidate), have been synthesized and structurally characterized. Complex 4 contains two dinuclear and one tetranuclear heterobimetallic clusters in an asymmetric unit whereas the structure of complex 5 features a one-dimensional heterobimetallic zigzag chain. The Cu(II) ion is penta-coordinated in

He-Rui Wen; Cai-Feng Wang; Zi-Yi Du; Jing-Lin Zuo

2008-01-01

22

Synthesis, structures and magnetic properties of nickel bis(dithiolene) complexes with [Fe(qsal)2  

Microsoft Academic Search

Two new compounds containing the possible Fe(III) spin-crossover cation, [Fe(qsal)2] (qsalH = N-(8-quinolyl)salicylaldimine), and nickel bis(dithiolene) anions have been synthesized. Both are 1 : 1 salts [Fe(qsal)2][Ni(dddt)2] · CH3CN · CH3OH (1) and [Fe(qsal)2][Ni(pddt)2] (2) (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate; pddt = 6,7-dihydro-5H-1,4-dithiepin-2,3-dithiolate). They have been characterized by X-ray crystal structure determination, elemental analysis, UV-Vis spectra and magnetic susceptibility measurements. The UV–Vis

Xiao-Ming Li; Yong Ji; Cai-Feng Wang; Jing-Lin Zuo; Xiao-Zeng You

2009-01-01

23

Structure and magnetic properties of a chiral dinuclear copper(II) complex assembled from a bpca- anion  

NASA Astrophysics Data System (ADS)

A novel chiral dinuclear Cu(II) cluster [Cu2(bpca)(bpy)(H2O)(NO3)3] (1) (bpca- is the anion of bis(2-pyridylcarbonyl)amine and bpy is 2,2?-bipyridine), was synthesized and characterized. Single crystal X-ray diffraction analysis showed that the two Cu(II) ions in complex 1 are sitting in a distorted octahedral arrangement and bridged by the organic spacer bpca-. Hydrogen bonding links neighboring dinuclear units into a three-dimensional framework. Inversion crystallographic symmetry gives dimers as either ? or ? isomers. Racemization of complex 1 was confirmed by circular dichroism (CD) spectroscopy. The temperature dependence of the magnetic susceptibility for complex 1 in the range 2-300 K indicates the presence of ferromagnetic Cu⋯Cu exchange. The data fitting gave the magnetic coupling constant J = 8.08 cm-1.

Lu, Zhengliang; Lu, Jing; Huang, Ximing; Liu, Cai-Ming; Fan, Chunhua; Nie, Yong; Sun, Guoxin

2014-05-01

24

Synthesis, crystal structure, magnetic property and oxidative DNA cleavage activity of an octanuclear copper(II) complex  

E-print Network

. Introduction Identifying molecules that intercalate into DNA helices has attracted considerable interest overSynthesis, crystal structure, magnetic property and oxidative DNA cleavage activity binds to double-stranded supercoiled plasmid DNA giving a Kapp value of 1.2 · 107 M�1 and displays

Gao, Song

25

Synthesis, crystal structures and magnetic properties of one-and two-dimensional copper(II) complexes bridged by succinate q  

E-print Network

) Succinic acid (0.118 g, 1 mmol) was dissolved in a solution of NaOH (0.008 g, 2 mmol) in H2O (4 mSynthesis, crystal structures and magnetic properties of one- and two-dimensional copper(II) complexes bridged by succinate q Siau Gek Ang a,*, Bai Wang Sun a , Song Gao b a Department of Chemistry

Gao, Song

26

Preparation of ?-Fe 2 O 3 nanopowders by direct thermal decomposition of Fe-urea complex: reaction mechanism and magnetic properties  

Microsoft Academic Search

In this work, a novel method of producing maghemite (?-Fe2O3) nanopowders has been developed, which can be performed by the direct thermal decomposition of an Fe–urea complex ([Fe(CON2H4)6](NO3)3) in a single step. The reaction mechanism, particle morphology, and the magnetic properties of the ?-Fe2O3 nanopowders have been studied by using thermogravimetric (TG), differential scanning calorimetry (DSC), fourier transformed\\u000a infrared (FTIR)

S. Zhao; H. Y. Wu; L. Song; O. Tegus; S. Asuha

2009-01-01

27

Switching of single-molecule magnetic properties of TbIII -porphyrin double-decker complexes and observation of their supramolecular structures on a carbon surface.  

PubMed

Double-decker complexes based on single-molecule magnets (SMMs) are a class of highly promising molecules for applications in molecular spintronics, wherein control of both the ligand oxidative states and the 2D supramolecular structure on carbon materials is of great importance. This study focuses on the synthesis and study of 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP)-Tb(III) double-decker complexes with different electronic structures comprising protonated, anionic, and radical forms. Magnetic susceptibility measurements revealed that only the anionic and radical forms of the OEP-Tb(III) double-decker complexes exhibited SMM properties. The barrier heights for magnetic moment reversal were estimated to be 207 and 215?cm(-1) for the anionic and radical forms, respectively. Scanning tunneling microscopy (STM) investigations revealed that these OEP-Tb(III) complexes form well-ordered monolayers upon simple dropcasting from dilute dichloromethane solutions. All three complexes form an isomorphic pseudo-hexagonal 2D pattern, regardless of the differences in the electronic structures of their porphyrin-Tb cores. This finding is of interest for SMM technology as ultrathin films of these materials undergoing chemical transformations will not require any detrimental reorganization. Finally, we demonstrate self-assembly of the protonated 5,15-bisdodecylporphyrin (BDP)-Tb(III) double-decker complex as an example of successful supramolecular design to achieve controlled alignment of SMM-active sites. PMID:25042020

Inose, Tomoko; Tanaka, Daisuke; Tanaka, Hirofumi; Ivasenko, Oleksandr; Nagata, Toshi; Ohta, Yusuke; De Feyter, Steven; Ishikawa, Naoto; Ogawa, Takuji

2014-09-01

28

Ab initio calculation of anisotropic magnetic properties of complexes. I. Unique definition of pseudospin Hamiltonians and their derivation.  

PubMed

A methodology for the rigorous nonperturbative derivation of magnetic pseudospin Hamiltonians of mononuclear complexes and fragments based on ab initio calculations of their electronic structure is described. It is supposed that the spin-orbit coupling and other relativistic effects are already taken fully into account at the stage of quantum chemistry calculations of complexes. The methodology is based on the establishment of the correspondence between the ab initio wave functions of the chosen manifold of multielectronic states and the pseudospin eigenfunctions, which allows to define the pseudospin Hamiltonians in the unique way. Working expressions are derived for the pseudospin Zeeman and zero-field splitting Hamiltonian corresponding to arbitrary pseudospins. The proposed calculation methodology, already implemented in the SINGLE_ANISO module of the MOLCAS-7.6 quantum chemistry package, is applied for a first-principles evaluation of pseudospin Hamiltonians of several complexes exhibiting weak, moderate, and very strong spin-orbit coupling effects. PMID:22897260

Chibotaru, L F; Ungur, L

2012-08-14

29

Chondrule magnetic properties  

NASA Technical Reports Server (NTRS)

The topics discussed include the following: chondrule magnetic properties; chondrules from the same meteorite; and REM values (the ratio for remanence initially measured to saturation remanence in 1 Tesla field). The preliminary field estimates for chondrules magnetizing environments range from minimal to a least several mT. These estimates are based on REM values and the characteristics of the remanence initially measured (natural remanence) thermal demagnetization compared to the saturation remanence in 1 Tesla field demagnetization.

Wasilewski, P. J.; Obryan, M. V.

1994-01-01

30

Limiting nuclearity in formation of polynuclear metal complexes through [2 + 3] cycloaddition: synthesis and magnetic properties of tri- and pentanuclear metal complexes.  

PubMed

A tridentate ligand p-chloro-2-{(2-(dimethylamino)ethylimino)methyl}phenol (HL) was used to generate an octahedral nickel complex [Ni(L)Cl(H2O)2] 1 which was further converted into a square-planar nickel complex [Ni(L)(N3)] 2. The [2 + 3] cycloaddition reaction between metal coordinated azide 2 and different organonitriles under microwave irradiation afforded tri- and pentanuclear nickel(II) complexes 4a-4c. Reaction with benzonitrile and 3-cyano pyridine furnished the trinuclear species [Ni3L2(5-phenyltetrazolato)4(DMF)2] 4a and [Ni3L2{5-(3-pyridyl)-tetrazolato}4(DMF)2]·2H2O 4b, respectively. The nickel centers were found to be linearly disposed to each other and the complex is formed by a 2,3-tetrazolate bridge and a phenoxo bridge between central and terminal nickel atoms. Compound 2 when treated with 1,2-dicyanobenzene under identical conditions furnished a pentanuclear complex [Ni5L4{5-(2-cyanophenyl)-tetrazolato}4(OH)2(H2O)2]·3H2O·DMF 4c. In this pentanuclear compound two dimeric nickel units are connected to the central nickel center by a ?3-hydroxo bridge and a tetrazolate ligand operating via a relatively rare 1,2,3-bridging mode. The compounds were characterized by IR, elemental analysis, thermogravimetric analysis and single crystal X-ray crystallography. The magnetic susceptibility data for compounds 4a-4c show dominant antiferromagnetic interactions between the nickel centers for all the complexes. DFT calculations were performed to investigate the magnetic parameter in one of the complexes 4b by a broken symmetry approach. PMID:24722585

Saha, Manideepa; Nasani, Rajendar; Das, Mriganka; Mahata, Arup; Pathak, Biswarup; Mobin, Shaikh M; Carrella, Luca M; Rentschler, Eva; Mukhopadhyay, Suman

2014-06-01

31

Magnetization of rare earth\\/cobalt permanent magnets subsequent to assembly in complex rotor structures  

Microsoft Academic Search

The object of this program was to demonstrate the feasibility of magnetizing large rare earth\\/cobalt permanent magnets subsequent to their assembly in complex rotor structures. A safe demagnetization (to near zero remanence) technique was optimized and demonstrated on individual magnets with insignificant detrimental affect on the magnet physical properties. Magnetic finite element analysis was completed which optimized the winding location

D. N. Taneja; R. C. Webb; D. L. Martin

1982-01-01

32

Synthesis, crystal structure, magnetic property and DFT calculations of an unusual dinuclear ?2-alkoxido bridged iron(III) complex.  

PubMed

A new dinuclear di(?-alkoxido) bridged complex [Fe2L2] (1) (H3L = N,N'-bis{1-(2-hydroxyphenyl)-ethylidene}-2-hydroxy-1,3-propanediamine) has been synthesized and characterized. The structure of 1 consists of a centrosymmetric dimer where two crystallographically equivalent metal ions are asymmetrically bridged by two alkoxido oxygen atoms. In the structure, each ligand coordinates to one Fe(III) centre and consequently the imino nitrogen atoms are in cis positions, which is rather unusual for this ligand. Variable-temperature magnetic susceptibility measurements of the complex indicate that the two iron(III) centres are antiferromagnetically coupled (J = -17.46 cm(-1)). The exchange mechanism has been investigated by means of DFT calculations. In addition, the theoretical study has been also used to rationalize the unusual coordination mode of the Schiff base ligand. Moreover, the influence of the weak forces or solvent molecules present in the solid-state structure for the conformational change is also analysed theoretically. This theoretical calculation incorporates two more similar structures, [Fe2L]·CH2Cl2 (2) and [Fe2L'2]·2CH3CN (3) (H3L' = N,N'-bis(salicylidene)-1,3,-diaminopropan-2-ol), for a comparative study. Complex 2 has been reported previously in the literature with the usual binding mode of the ligands. We have repeated its synthesis and recrystallized it from another solvent (acetonitrile) to get complex 3 which is isostructural with 2 but has acetonitrile as solvent molecule. PMID:23846248

Biswas, Rituparna; Diaz, Carmen; Bauzá, Antonio; Frontera, Antonio; Ghosh, Ashutosh

2013-09-14

33

Two molecular wheels 12-MC-6 complexes: Synthesis, structure and magnetic property of [Co(?2-SEt)2]6 and [Fe(?2-SEt)2]6  

NASA Astrophysics Data System (ADS)

The syntheses and structures of two ethyl mercaptan molecular wheels complexes, [M(?2-SCH2CH3)2]6 (M=Fe, Co), have been reported. Each metal atom is surrounded by four S atoms of the ?2-SCH2CH3 ligands in a distorted square plane fashion. The edge-sharing S4 square planes connect with each other to form a ring. Six metal atoms are located at the vertices of an almost hexagon, with M···M separations in the range of 2.903(1)~2.936(2) Å for Fe and 2.889(2)~2.962(2) Å for Co. The diameter of the ring, defined as the average distance between two opposing metal atoms, is 5.850(1) Å for Fe and 5.780(1) Å for Co, respectively. The magnetic property behaves of cobalt(II) cluster complex is studied.

Wang, Jing; Jian, Fangfang; Huang, Baoxin; Bai, Zhengshuai

2013-08-01

34

Synthesis, structural and magnetic properties of oxo-, chloroacetato-bridged tetra-nuclear iron(III) complex  

NASA Astrophysics Data System (ADS)

Oxo- and chloroacetato-bridged tetra-nuclear iron(III) complex [Fe4O2(ClCH2COO)8(bpy)2]·H2O, where bpy = 2,2'-bipyridine, has been synthesized and characterized on the basis of X-ray crystallography, elemental analysis, cyclic voltammetric, UV-vis and IR spectroscopic techniques. X-ray diffraction analysis reveals that the complex crystallizes in the monoclinic space group P2/n with a = 9.629(5) Å, b = 13.742(5), c = 20.437(5) Å, ? = ? = 90.000(5)°, ? = 99.792(5)°, V = 2664.9(18) Å3 and Z = 2. The tetra-nuclear entity consists of a [Fe4(?3-O)2]8+ unit comprising four FeIII atoms with a "butterfly" arrangement. Each pair of iron(III) atoms occupy the "hinge" or "body" sites, and "wing-tip" sites, respectively. It undergoes two stepwise one electron reductions, one is quasi-reversible at E1/2 = +0.061 V vs Ag/AgCl (?Ep = 0.082 V) and the other is irreversible at EP.C = -0.38 V at a scan rates 0.1 V s-1. Variable-temperature magnetic susceptibility data reveals strong antiferromagnetic exchange interactions among the four high-spin FeIII ions. The exchange coupling constant Jbb (body-body interaction) is indeterminate due to prevailing spin frustration, but the 'wing-body' antiferromagnetic interaction (Jwb) was evaluated as -115 cm-1, using the spin Hamiltonion model H = -Jwb (S1?S2 + S2?S1 + S1'?S2' + S2'?S1) -Jbb(S2?S2').

Dutta, Amit Kumar; Maji, Swarup Kumar; Dutta, Supriya; Robert Lucas, C.; Adhikary, Bibhutosh

2012-12-01

35

A dinuclear copper(II) complex with adeninate bridge ligands and prominent DNA cleavage activity. Structural and spectroscopic characterization and magnetic properties.  

PubMed

A new dinuclear copper(II) complex has been synthesized and structurally characterized: [Cu(mu-ade)(tolSO3)(phen)]2.2H2O (Hade = adenine, tolSO3- = toluenesulfonate anion). Its magnetic properties and electronic paramagnetic resonance (EPR) spectra have been studied in detail. The compound has two metal centers bridged by two adeninate NCN groups. The coordination geometry of the copper(II) ions in the dinuclear entity is distorted square pyramidal, with the four equatorial positions occupied by two phenanthroline N atoms and two N atoms from different adenine molecules. The axial position is occupied by one sulfonate O atom. Magnetic susceptibility data show antiferromagnetic behavior with an estimated exchange constant of -2J = 65 cm-1. The EPR spectrum has been obtained at both X- and Q-band frequencies; a study at different temperatures has been carried out at the latter. Above 20 K, the Q-band spectra are characteristic of S = 1 species with a small zero-field splitting parameter (D = 0.0970 cm-1). A detailed study of the DNA-complex interaction has been performed. The title complex efficiently cleaves the pUC18 plasmid in the presence of reducing agents. Both the kinetics and the mechanism of the cleavage reaction are examined and described herein. PMID:17630687

García-Giménez, José Luis; Alzuet, Gloria; Gonzalez-Alvarez, Marta; Castiñeiras, Alfonso; Liu-Gonzalez, Malva; Borras, Joaquín

2007-08-20

36

Ionic pair complexes with well-separated columnar stack structure based on [Pt(mnt)2]- ions showing unusual magnetic transition: syntheses, crystal structures, and magnetic properties.  

PubMed

Three ion pair complexes, [4-R-benzylpyridinium][bis(maleodinitriledithiolato)platinum(III)] (abbreviated as [RBzPy][Pt(mnt)(2)]; R = Cl (1), Br (2), or NO(2) (3)), have been synthesized. The cations and anions stack into well-separated columns in the solid state, and the Pt(III) ions form a 1-D zigzag chain within a [Pt(mnt)(2)](-) column through Pt...S, S...S, and Pt...S...Pt interactions. The chain is uniform in 1 and 2, while it alternates in 3. Unusual magnetic phase transitions from paramagnetism to diamagnetism were observed in these three complexes at approximately 275 K for 1, approximately 269 K for 2, and approximately 184 K for 3. These phase transitions were also found in DSC measurements for 1 and 2. The overall magnetic behaviors for 1-3 indicate the presence of antiferromagnetic exchange interactions in the high-temperature phase and spin-gapped systems in the low-temperature phase. Below 50 K, 2 exhibits weak ferromagnetism. The spontaneous moments are nearly repressed by a field of 1.0 T. The crystal structure of 2 at 173 K reveals that there are two crystallographically independent [Pt(mnt)(2)](-) entries in an asymmetric unit. These two crystallographically independent [Pt(mnt)(2)](-) entries satisfy the spin-canting condition, and the EPR spectra measured at room temperature exhibit anisotropic character. Therefore, the weak ferromagnetic behavior in the low-temperature region for 2 can be attributed to the spin-canting phenomenon. PMID:15074975

Ren, X M; Okudera, H; Kremer, R K; Song, Y; He, C; Meng, Q J; Wu, P H

2004-04-19

37

Synthesis and magnetic properties of a new family of macrocyclic M(II)3Ln(III) complexes: insights into the effect of subtle chemical modification on single-molecule magnet behavior.  

PubMed

Thirteen tetranuclear mixed-metal complexes of the hexaimine macrocycle (L(Pr))(6-) have been prepared in a one-pot 3:1:3:3 reaction of copper(II) acetate hydrate, the appropriate lanthanide(III) nitrate hydrate, 1,4-diformyl-2,3-dihydroxybenzene (1), and 1,3-diaminopropane. The resulting family of copper(II)-lanthanide(III) macrocyclic complexes has the general formula Cu(II)(3)Ln(III)(L(Pr))(NO(3))(3)·solvents (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Tb, Ho, Er, Tm, or Yb). X-ray crystal structure determinations carried out on [Cu(3)Ce(L(Pr))(NO(3))(3)(MeOH)(3)] and [Cu(3)Dy(L(Pr))(NO(3))(3)(MeOH)(3)] confirmed that the large Ln(III) ion is bound in the central O(6) site and the three square pyramidal Cu(II) ions in the outer N(2)O(2) sites (apical donor either nitrate anion or methanol molecule) of the Schiff base macrocycle. Only the structurally characterized Cu(3)Tb complex, reported earlier, is a single-molecule magnet (SMM): the other 12 complexes do not exhibit an out-of-phase ac susceptibility signal or hysteresis of magnetization in a dc field. Ab initio calculations allowed us to rationalize the observed magnetic properties, including the significant impact of subtle chemical modification on SMM behavior. Broken-symmetry density functional theory (BS-DFT) calculations show there is a subtle structural balance as to whether the Cu···Cu exchange coupling is ferro- or antiferromagnetic. Of the family of 13 magnetically characterized tetranuclear Cu(II)(3)Ln(III) macrocyclic complexes prepared, only the Tb(III) complex is an SMM: the theoretical reasons for this are discussed. PMID:23004914

Feltham, Humphrey L C; Clérac, Rodolphe; Ungur, Liviu; Vieru, Veacheslav; Chibotaru, Liviu F; Powell, Annie K; Brooker, Sally

2012-10-15

38

Complexing properties of some pyrimidines.  

PubMed

The synthesis of transition metal barbiturate, and thiobarbiturate complexes containing different functional groups of variable electronic character with CoII, NiII, CuII, PdII, and PtII have been prepared. The stereochemistry and the mode of bonding of the complexes were determined by elemental analysis and electronic and vibrational spectra together with their magnetic moment values. Electronic spin resonance of copper complexes were recorded. The Racah parameter of some cobalt and nickel complexes were calculated. Some of the complexes are of mixed stereochemistry. All the PdII or PtII complexes are of square planar geometries. PMID:16440987

Masoud, Mamdouh S; Haggag, Sawsan S; Khalil, Ekram A

2006-01-01

39

A 3D complex containing novel 2D Cu{sup II}-azido layers: Structure, magnetic properties and effects of 'Non-innocent' reagent  

SciTech Connect

A novel copper-azido coordination polymer, [Cu{sub 2}(N{sub 3}){sub 3}(L)]{sub n} (1, HL=pyrazine-2-carboxylic acid), has been synthesized by hydrothermal reaction with 'Non-innocent' reagent in the aqueous solution. In the reaction system, Cu{sup II} ions are avoided to reduce to Cu{sup I} ions due to the existence of Nd{sup III}. It is found that the complex is a 3D structure based on two double EO azido bridged trimmers and octahedron Cu{sup II} ions, in which the azide ligands take on EO and {mu}{sub 1,1,3} mode to form Cu{sup II}-azido 2D layers, furthermore L ligands pillar 2D layers into an infinite 3D framework with the Schlaefli symbol of {l_brace}4;6{sup 2}{r_brace}4{l_brace}4{sup 2};6{sup 12};8{sup 10};10{sup 4}{r_brace}{l_brace}4{sup 2};6{sup 4}{r_brace}. Magnetic studies revealed that the interactions between the Cu{sup II} ions in the trimmer are ferromagnetic for the Cu-N-Cu angle nearly 98 Degree-Sign , while the interactions between the trimmer and octahedron Cu{sup II} ion are antiferromgantic and result in an antiferromagnetic state. - Graphical abstract: A 3D complex containing novel 2D Cu{sup II}-azido layers, [Cu{sub 2}(N{sub 3}){sub 3}(L)]{sub n} (HL=pyrazine-2-carboxylic acid), was synthesized by hydrothermal reaction and exhibit interesting structure and magnetic properties. Highlights: Black-Right-Pointing-Pointer 'Non-innocent' reagents plays a key role in the process of formation of this complex. Black-Right-Pointing-Pointer 2D layer is formed only by Cu{sup II} ions and azido ligands. Black-Right-Pointing-Pointer Pyrazine-2-carboxylate ligands reinforce 2D layers and pillar them into an infinite 3D framework. Black-Right-Pointing-Pointer Magnetic study indicates that alternating FM-AF coupling exists in the complex.

Gao, Xue-Miao; Guo, Qian [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China)] [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Zhao, Jiong-Peng, E-mail: horryzhao@yahoo.com [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China)] [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Liu, Fu-Chen, E-mail: fuchenliutj@yahoo.com [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China) [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Lanzhou Petrochemical College of Vocational Technology, Lanzhou 730060 (China)

2012-12-15

40

Coligand-regulated assembly, fluorescence, and magnetic properties of Co(II) and Cd(II) complexes with a non-coplanar dicarboxylate  

SciTech Connect

A non-coplanar dicarboxylate ndca (H{sub 2}ndca=5-norbornene-2,3-dicarboxylic acid), combining with various dipyridyl-typed tectons, constructs six Cd(II)/Co(II) coordination polymers under hydrothermal conditions, namely [Co(ndca)(H{sub 2}O)]{sub n} (1), ([Co(ndca)(bpe)(H{sub 2}O)]·H{sub 2}O){sub n} (2), [Co(ndca)(bpa){sub 0.5}(H{sub 2}O)]{sub n} (3), [Cd(ndca)(bpe)(H{sub 2}O)]{sub n} (4), ([Cd(ndca)(bpa)(H{sub 2}O)]·0.5H{sub 2}O){sub n} (5), and ([Cd(ndca)(bpp) (H{sub 2}O)]·H{sub 2}O){sub n} (6) (bpe=1,2-di(4-pyridyl)ethylene, bpa=1,2-bi(4-pyridyl)ethane, and bpp=1,3-bis(4-pyridyl)propane). All these compounds contain various metal(II)–carboxylate motifs, including carboxylate binuclear (2, 4, 5), carboxylate chain (1, 6) and carboxylate layer (3), which are further extended by dipyridyl-typed coligands to afford a vast diversity of the structures with 2D pyknotic layers (1, 6), 2D open layer (5), 2D?3D interpenetrated networks (2,4), and 3D pillared-layer framework (3), respectively. In addition, fluorescent spectra of Cd(II) complexes and magnetic properties of Co(II) complexes are also given. - Graphical abstract: Six various cadmium(II)/cobalt(II)–organic frameworks were constructed by 5-norbornene-2,3-dicarboxylic acid and different bis(pyridine) rod-like tectons, and Cd (II) complexes exhibit blue–violet emissions, whereas Co (II) complexes show antiferromagnetic behaviours. Display Omitted.

Xin, Ling-Yun [College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471022 (China); Liu, Guang-Zhen, E-mail: gzliuly@126.com [College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471022 (China); Ma, Lu-Fang [College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471022 (China); Wang, Li-Ya [College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471022 (China); College of Chemistry and Pharmacy Engineering, Nanyang Normal University, Nanyang 473061 (China)

2013-10-15

41

Structurally Diverse Copper(II) Complexes of Polyaza Ligands Containing 1,2,3-Triazoles: Site Selectivity and Magnetic Properties  

E-print Network

Structurally Diverse Copper(II) Complexes of Polyaza Ligands Containing 1,2,3-Triazoles: Site mimetics.7,8 In the past few years, 1,2,3-triazole has also been recognized as a potent hydrogen-bond donor,2,3- triazole as a functionally versatile molecule. In conjunction with the synthetic prowess of the Cu

Weston, Ken

42

Magnetic Properties of Single Crystal Nickel Nanowires  

NASA Astrophysics Data System (ADS)

Toward the goal of understanding magnetism in confined dimensions, we have synthesized Nickel nanowires (NWs) by chemical vapor deposition and characterized their magnetic properties. By tuning chemical vapor deposition synthesis parameters, we can controllably synthesize a variety of morphologically dissimilar Ni products onto untreated amorphous SiO2||Si substrates [1]. These structures include polycrystalline core-shell NWs, single-crystal cubes, in-plane wires, and vertically-oriented single crystal arrays. To probe the magnetic properties of individual NWs, we combined magneto-transport, XPEEM, and magnetic modeling. For polycrystalline NWs, the magnetic properties are dominated by shape anisotropy. However, for single-crystal NWs, there is a competition between the shape anisotropy along the (001) direction and magneto-crystalline anisotropy along the (111) direction. This gives rise to complex magnetic stripe domain patterns along the wires, interesting magneto-transport properties, and novel reversal modes not typically observed in magnetic wires. [4pt] [1] K.T. Chan, J.J. Kan, E.E. Fullerton, et al., "Oriented Growth of Single-Crystal Ni Nanowires onto Amorphous SiO2," Nano Letters, Oct. 2010

Kan, Jimmy; Chan, Keith; Shipton, Erik; Fullerton, Eric

2011-03-01

43

Magnetism of the oceanic crust: Evidence from ophiolite complexes  

Microsoft Academic Search

The magnetic properties of six ophiolite complexes from around the world, ranging in age from Jurassic to Miocene, are presented. An emphasis is placed in our study on the petrologic and isotopic data from these ophiolite complexes in order to determine first whether the rock samples presently available represent the pristine ocean crust or whether they have been altered subaerially

Subir K. Banerjee

1980-01-01

44

Metal(II) Nicotinamide Complexes Containing Succinato, Succinate and Succinic Acid: Synthesis, Crystal Structures, Magnetic, Thermal, Antimicrobial and Fluorescent Properties  

Microsoft Academic Search

Four novel divalent transitional metal succinates (suc) with nicotinamide (nia), {[M(?-suc)(H2O)2(nia)2]·2H2O}\\u000a n\\u000a [M = Mn (1), Ni (2)], [Cu(suc)(nia)2] (3) and [Ni(H2O)4(nia)2](suc)·(H2suc) (4), have been synthesized and characterized by elemental analyses, IR and TG-DTA. X-ray analyses of 2 and 4 reveal that they crystallize in a triclinic space group $$ P\\\\bar{1}. $$ Complex 2 is a 1-D coordination polymer, in which the

Selcuk DemirVeysel; Veysel T. Yilmaz; Bahtiyar Sariboga; Orhan Buyukgungor; Jerzy Mrozinski

2010-01-01

45

Magnetic Properties of Diabase Dikes  

Microsoft Academic Search

A study has been made of the magnetic properties of several diabase dikes of Precambrian age from the Canadian shield. These dikes are of widely differing ages and belong to several swarms having widely different strike directions. It was found that the direction of reinanent magnetization of the various dikes was quite widely scattered before they were demagnetized in a-c

D. W. Strangway

1961-01-01

46

Magnetic Properties in Nondestructive Testing  

E-print Network

' and `soft' magnetic materials. Curie (1898) found a relationship between magnetic behaviour and carbon properties over time, which he related to slow metallurgical changes. Such re- lationships suggestedB/dH, is the differential permeability, µ ; the maximum value of this usually occurs at H = HC and is denoted µmax

Cambridge, University of

47

Synthesis, structures, luminescence\\/magnetic properties of complexes of the M\\/1-hydroxybenzotriazole, M = cobalt, nickel, silver, zinc and copper  

Microsoft Academic Search

Five novel complexes, Co(OBt)2·7H2O (1) (OBt=1-hydroxybenzotriazole ion), Ni3(OBt)6·6H2O (2), [Ag(OBt)(HOBt)]n (3), [Zn(OBt)2]n (4) and [Cu2(OBt)4·3H2O]n (5) were synthesized by hydrothermal method and characterized by elemental analysis, IR spectroscopy, TGA, XRPD, and single-crystal X-ray diffraction. The results from single-crystal X-ray diffraction indicate that 1–5 are zero-dimensional (0D), zero-dimensional, one-dimensional (1D), and three-dimensional (3D) frameworks, respectively. In particular, 3 is twin crystal;

Zhong-Qiang Zhang; Ru-Dan Huang; Lan-Jun Dong; Yan-Qing Xu; Li-Qiong Yu; Zhi-Wei Jiao; Chang-Wen Hu

2009-01-01

48

Magnetic modeling of the Bushveld Igneous Complex  

Microsoft Academic Search

Magnetic modeling of the 2.06 Ga Bushveld Complex presents special challenges due a variety of magnetic effects. These include strong remanence in the Main Zone and extremely high magnetic susceptibilities in the Upper Zone, which exhibit self-demagnetization. Recent palaeomagnetic results have resolved a long standing discrepancy between age data, which constrain the emplacement to within 1 million years, and older

S. J. Webb; J. Cole; S. A. Letts; C. Finn; T. H. Torsvik; M. D. Lee

2009-01-01

49

Tuning the Magnetic Properties of Nanoparticles  

PubMed Central

The tremendous interest in magnetic nanoparticles (MNPs) is reflected in published research that ranges from novel methods of synthesis of unique nanoparticle shapes and composite structures to a large number of MNP characterization techniques, and finally to their use in many biomedical and nanotechnology-based applications. The knowledge gained from this vast body of research can be made more useful if we organize the associated results to correlate key magnetic properties with the parameters that influence them. Tuning these properties of MNPs will allow us to tailor nanoparticles for specific applications, thus increasing their effectiveness. The complex magnetic behavior exhibited by MNPs is governed by many factors; these factors can either improve or adversely affect the desired magnetic properties. In this report, we have outlined a matrix of parameters that can be varied to tune the magnetic properties of nanoparticles. For practical utility, this review focuses on the effect of size, shape, composition, and shell-core structure on saturation magnetization, coercivity, blocking temperature, and relaxation time. PMID:23912237

Kolhatkar, Arati G.; Jamison, Andrew C.; Litvinov, Dmitri; Willson, Richard C.; Lee, T. Randall

2013-01-01

50

Hydroxide-bridged cubane complexes of nickel(II) and cadmium(II): magnetic, EPR, and unusual dynamic properties.  

PubMed

The reactions of M(ClO4)2·xH2O (M = Ni(II) or Cd(II)) and m-bis[bis(1-pyrazolyl)methyl]benzene (Lm) in the presence of triethylamine lead to the formation of hydroxide-bridged cubane compounds of the formula [M4(?3-OH)4(?-Lm)2(solvent)4](ClO4)4, where solvent = dimethylformamide, water, acetone. In the solid state the metal centers are in an octahedral coordination environment, two sites are occupied by pyrazolyl nitrogens from Lm, three sites are occupied by bridging hydroxides, and one site contains a weakly coordinated solvent molecule. A series of multinuclear, two-dimensional and variable-temperature NMR experiments showed that the cadmium(II) compound in acetonitrile-d3 has C2 symmetry and undergoes an unusual dynamic process at higher temperatures (?GLm‡ = 15.8 ± 0.8 kcal/mol at 25 °C) that equilibrates the pyrazolyl rings, the hydroxide hydrogens, and cadmium(II) centers. The proposed mechanism for this process combines two motions in the semirigid Lm ligand termed the “Columbia Twist and Flip:” twisting of the pyrazolyl rings along the Cpz–Cmethine bond and 180° ring flip of the phenylene spacer along the CPh–Cmethine bond. This dynamic process was also followed using the spin saturation method, as was the exchange of the hydroxide hydrogens with the trace water present in acetonitrile-d3. The nickel(II) analogue, as shown by magnetic susceptibility and electron paramagnetic resonance measurements, has an S = 4 ground state, and the nickel(II) centers are ferromagnetically coupled with strongly nonaxial zero-field splitting parameters. Depending on the Ni–O–Ni angles two types of interactions are observed: J1 = 9.1 cm(–1) (97.9 to 99.5°) and J2 = 2.1 cm(–1) (from 100.3 to 101.5°). “Broken symmetry” density functional theory calculations performed on a model of the nickel(II) compound support these observations. PMID:24750135

Reger, Daniel L; Pascui, Andrea E; Pellechia, Perry J; Smith, Mark D; Jezierska, Julia; Ozarowski, Andrew

2014-05-01

51

Molecular mechanics description of the stabilized effects in (ethylenediamine-N,N?-diacetato)chromate(III) dinuclear complex bridged by pyrazole-3,5-dicarboxylate: DFT calculations of magnetic properties  

NASA Astrophysics Data System (ADS)

The mononuclear chromium(III) complex containing quadridentate ligand ethylenediamine- N, N'-diacetate (edda) and the corresponding dinuclear complex bridged by pyrazole-3,5-dicarboxylate (pzdc) are investigated by molecular mechanics calculations. Conformational analysis has been performed using the consistent force field (CFF) method, with the parameters developed previously for edta-type complexes and supplemented with new parameters for dinuclear system. These calculations indicated that many properties of [Cr 2(edda) 2(?-pzdc)] - system can be explained by steric effects. Density functional theory (DFT) was applied to describe the magnetic couplings in [Cr 2(edda) 2(?-pzdc)] -.

Grubiši?, Sonja; Gruden-Pavlovi?, Maja; Radanovi?, Dušanka D.; Peri?, Marko; Niketi?, Svetozar R.

2009-02-01

52

Probing the magnetic and magnetothermal properties of M(ii)-Ln(iii) complexes (where M(ii) = Ni or Zn; Ln(iii) = La or Pr or Gd).  

PubMed

We establish the coordination potential of the Schiff base ligand (2-methoxy-6-[(E)-2'-hydroxymethyl-phenyliminomethyl]-phenolate (H2L)) via the isolation of various M(ii)-Ln(iii) complexes (where M(ii) = Ni or Zn and Ln(iii) = La or Pr or Gd). Single crystals of these five complexes were isolated and their solid state structures were determined by single crystal X-ray diffraction. Structural determination revealed molecular formulae of [NiGd(HL)2(NO3)3] (), [NiPr(HL)2(NO3)3] () and [Ni2La(HL)4(NO3)](NO3)2 (), [Zn2Gd(HL)4(NO3)](NO3)2 (), and [Zn2Pr(HL)4(NO3)](NO3)2 (). Complexes and were found to be neutral heterometallic dinuclear compounds, whereas were found to be linear heterometallic trinuclear cationic complexes. Direct current (dc) magnetic susceptibility and magnetization measurements conclusively revealed that complexes and possess a spin ground state of S = 9/2 and 7/2 respectively. Empirically calculated ??MT derived from the variable temperature susceptibility data for all complexes undoubtedly indicates that the Ni(ii) ion is coupled ferromagnetically with the Gd(iii) ion, and antiferromagnetically with the Pr(iii) ion in and respectively. The extent of the exchange interaction for was estimated by fitting the magnetic susceptibility data using the parameters (g = 2.028, S = 9/2, J = 1.31 cm(-1) and zJ = +0.007), supporting the phenomenon observed in an empirical approach. Similarly using a HDVV Hamiltonian, the magnetic data of and were fitted, yielding parameters g = 2.177, D = 3.133 cm(-1), J = -0.978 cm(-1), (for ) and g = 1.985, D = 0.508 cm(-1) (for ). The maximum change in magnetic entropy (-?Sm) estimated from the isothermal magnetization data for was found to be 5.7 J kg(-1) K(-1) (?B = 7 Tesla) at 7.0 K, which is larger than the -?Sm value extracted from of 3.5 J kg(-1) K(-1) (?B = 7 Tesla) at 15.8 K, revealing the importance of the exchange interaction in increasing the overall ground state of a molecule for better MCE efficiency. PMID:25330279

Ahmed, Naushad; Das, Chinmoy; Vaidya, Shefali; Srivastava, Anant Kumar; Langley, Stuart K; Murray, Keith S; Shanmugam, Maheswaran

2014-11-01

53

Magnetic Backgrounds from Generalised Complex Manifolds  

E-print Network

The magnetic backgrounds that physically give rise to spacetime noncommutativity are generally treated using noncommutative geometry. In this article we prove that also the theory of generalised complex manifolds contains the necessary elements to generate B-fields geometrically. As an example, the Poisson brackets of the Landau model (electric charges on a plane subject to an external, perperdicularly applied magnetic field) are rederived using the techniques of generalised complex manifolds.

J. M. Isidro

2005-03-04

54

Four mu4-oxo-bridged copper(II) complexes: magnetic properties and catalytic applications in liquid phase partial oxidation reactions.  

PubMed

Four copper(II) complexes, [Cu(4)(O)(L(n))(2)(CH(3)COO)(4)] with N(2)O-donor Schiff-base ligands, where HL(1) = 4-methyl-2,6-bis(cyclohexylmethyliminomethyl)phenol for complex 1, HL(2) = 4-methyl-2,6-bis(phenylmethyliminomethyl)phenol for complex 2 x CH(3)CN, HL(3) = 4-methyl-2,6-bis(((3-tri-fluoromethyl)phenyl)methyliminomethyl)phenol for complex 3, HL(4) = 4-methyl-2,6-bis(((4-tri-fluoromethyl)phenyl)methyliminomethyl)phenol for complex 4, were synthesized and characterized by elemental analysis, FT-IR, UV-vis spectroscopy and finally by single crystal X-ray diffraction study. X-Ray analysis reveals that all of these are mu(4)-oxo-bridged tetrameric copper(II) complexes. Four copper atoms arrange themselves around an oxygen atom tetrahedrally. Magnetic susceptibility measurements show the existence of very strong antiferromagnetic coupling among these ions (J = -210.1 to -271.3 cm(-1)), mediated by the oxygen atoms. Catalysis of the epoxidation of cyclohexene, styrene, alpha-methylstyrene and trans-stilbene by these complexes has been carried out homogeneously as well as heterogeneously by immobilizing the metal complexes over 2D-hexagonal mesoporous silica. The results obtained in both the catalytic conditions show that the olefins are converted to the respective epoxides in good yield together with high selectivity. PMID:19859610

Roy, Partha; Nandi, Mahasweta; Manassero, Mario; Riccó, Mauro; Mazzani, Marcello; Bhaumik, Asim; Banerjee, Pradyot

2009-11-21

55

Properties and biomedical applications of magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles have a number of unique properties, making them promising agents for applications in medicine including magnetically targeted drug delivery, magnetic hyperthermia, magnetic resonance imaging, and radiation therapy. They are biocompatible and can also be coated with biocompatible surfactants, which may be further functionalized with optically and therapeutically active molecules. These nanoparticles can be manipulated with non-invasive external magnetic field to produce heat, target specific site, and monitor their distribution in vivo. Within this framework, we have investigated a number of biomedical applications of these nanoparticles. We synthesized a thermosensitive microgel with iron oxide adsorbed on its surface. An alternating magnetic field applied to these nanocomposites heated the system and triggered the release of an anticancer drug mitoxantrone. We also parameterized the chain length dependence of drug release from dextran coated iron oxide nanoparticles, finding that both the release rate and equilibrium release fraction depend on the molecular mass of the surfactant. Finally, we also localized dextran coated iron oxide nanoparticles labeled with tat peptide to the cell nucleus, which permits this system to be used for a variety of biomedical applications. Beyond investigating magnetic nanoparticles for biomedical applications, we also studied their magnetohydrodynamic and dielectric properties in solution. Magnetohydrodynamic properties of ferrofluid can be controlled by appropriate selection of surfactant and deielctric measurement showed magnetodielectric coupling in this system. We also established that some complex low temperature spin structures are suppressed in Mn3O4 nanoparticles, which has important implications for nanomagnetic devices. Furthermore, we explored exchange bias effects in Ni-NiO core-shell nanoparticles. Finally, we also performed extensive magnetic studies in nickel metalhydride (NiMH) batteries to determine the size of Ni clusters, which plays important role on catalyzing the electrochemical reaction and powering Ni-MH batteries.

Regmi, Rajesh Kumar

56

Syntheses, crystal structures, MMCT and magnetic properties of four one-dimensional cyanide-bridged complexes comprised of M(II)-CN-Fe(III) (M = Fe, Ru, Os).  

PubMed

Four new one-dimensional (1D) zigzag chain cyanide-bridged complexes [cis-M(II)(L)2(CN)2Fe(III)(salen)](PF6) (M = Fe, L = bpy, ; M = Fe, L = phen, ; M = Ru, L = bpy, ; M = Os, L = bpy, ) (bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline, salen = N,N'-ethylenebis(salicylideneaminato) dianion) have been synthesized and structurally as well as magnetically characterized, especially and are mixed-valence complexes. Fortunately, the crystals of complexes , and suitable for single-crystal X-ray diffraction analysis were obtained. In addition, the electronic absorption spectra indicate the existence of the MMCT (metal-to-metal charge transfer) bands in complexes . The temperature dependent magnetic susceptibilities reveal that the Fe(iii)-Fe(iii) exchange coupling separated by a diamagnetic cyanidometal -NC-M(ii)-CN- bridge is weakly ferromagnetic for , but weakly anti-ferromagnetic for . Moreover, the specific heat measurements suggest complexes exhibit a phase transition at 2.8 K, 2.7 K and 2.6 K, respectively. PMID:25337674

Wang, Yong; Ma, Xiao; Hu, Shengmin; Wen, Yuehong; Xue, Zhenzhen; Zhu, Xiaoquan; Zhang, Xudong; Sheng, Tianlu; Wu, Xintao

2014-11-01

57

Burnt clay magnetic properties and palaeointensity determination  

NASA Astrophysics Data System (ADS)

Burnt clay structures found in situ are the most valuable materials for archaeomagnetic studies. From these materials the full geomagnetic field vector described by inclination, declination and intensity can be retrieved. The reliability of the obtained directional results is related to the precision of samples orientation and the accuracy of characteristic remanence determination. Palaeointensity evaluations depend on much more complex factors - stability of carried remanent magnetization, grain-size distribution of magnetic particles and mineralogical transformations during heating. In the last decades many efforts have been made to shed light over the reasons for the bad success rate of palaeointensity experiments. Nevertheless, sometimes the explanation of the bad archaeointensity results with the magnetic properties of the studied materials is quite unsatisfactory. In order to show how difficult is to apply a priory strict criteria for the suitability of a given collection of archaeomagnetic materials, artificial samples formed from four different baked clays are examined. Two of the examined clay types were taken from clay deposits from different parts of Bulgaria and two clays were taken from ancient archaeological baked clay structures from the Central part of Bulgaria and the Black sea coast, respectively. The samples formed from these clays were repeatedly heated in known magnetic field to 700oC. Different analyses were performed to obtain information about the mineralogical content and magnetic properties of the samples. The obtained results point that all clays reached stable magnetic mineralogy after the repeated heating to 700oC, the main magnetic mineral is of titano/magnetite type and the magnetic particles are predominantly with pseudo single domain grain sizes. In spite that, the magnetic properies of the studied clays seem to be very similar, reliable palaeointensity results were obtained only from the clays coming from clay deposits. The palaeointensity experiments for the samples formed from the ancient baked clays completely failed to give relibable results.

Avramova, Mariya; Lesigyarski, Deyan

2014-05-01

58

Synthesis, crystal structures and magnetic properties of cyanide- and phenolate-bridged [M(III)NiII]2 tetranuclear complexes (M=Fe and Cr).  

PubMed

The binuclear complex NiII2L(H2O)2(ClO4)2(1) and the neutral tetranuclear bimetallic compounds [{M(III)(phen)(CN)4}2{NiII2L(H2O)2}].2CH3CN with M=Fe (2) and Cr (3)[H2L=11,23-dimethyl-3,7,15,19-tetraazatricyclo[19.3.1.1(9,13)]hexacosa-2,7,9,11,13(26),14,19,21(25),22,24-decaene-25,26-diol] have been synthesized and the structures of and determined by single crystal X-ray diffraction. and are isostructural compounds whose structure is made up of centrosymmetric binuclear cations [Ni2(L)(H2O)2]2+ and two peripheral [M(phen)(CN)4]- anions [M=Fe (2) and Cr (3)] acting as monodentate ligands towards the nickel atoms through one of their four cyanide nitrogen atoms. The environment of the metal atoms in 2 and 3 is six-coordinated: two phen-nitrogen and four cyanide-carbon atoms at the iron and chromium atoms and a water molecule, one cyanide-nitrogen and two phenolate-oxygens and two imine-nitrogens from the binucleating ligand L2- at the nickel atom build distorted octahedral surroundings. The values of the FeNi and CrNi separations through the single cyanide bridge are 5.058(1) and 5.174(2)A respectively, whereas the Ni-Ni distances across the double phenolate bridge are 3.098(2)(2) and 3.101(1) A (3). The magnetic properties of have been investigated in the temperature range 1.9-290 K. The magnetic behaviour of corresponds to that of an antiferromagnetically coupled nickel(II) dimer with J=-61.0(1) cm-1, the Hamiltonian being defined as H=-J S(A).S(B). An overall antiferromagnetic behaviour is observed for and with a low-lying singlet spin state. The values of the intramolecular magnetic couplings are J(Fe-Ni)=+17.4(1) cm-1 and J(Ni-Ni(a))=-44.4(1) cm-1 for and J(Cr-Ni)=+11.8(1) cm-1 and J(Ni-Ni(a))=-44.6(1) cm-1 for [H=-J(M-Ni)(S(M).S(Ni)+S(Ma).S(Nia))-J(Ni-Nia)S(Ni)S(Nia)]. Theoretical calculations using methods based on density functional theory (DFT) have been employed on in order to analyze the efficiency of the exchange pathways involved and also to substantiate the exchange coupling parameters. PMID:15824772

Toma, Liviu; Toma, Luminita Marilena; Lescouëzec, Rodrigue; Armentano, Donatella; De Munno, Giovanni; Andruh, Marius; Cano, Joan; Lloret, Francesc; Julve, Miguel

2005-04-21

59

Calculation of the energy loss in giant magnetic impedance elements using the complex magnetic permeability spectra  

NASA Astrophysics Data System (ADS)

The giant magnetic impedance (GMI) effect in ferromagnetic materials has been investigated for sensing applications. The GMI properties were evaluated via numerical solution of the complex magnetic permeability of the material. MATLAB simulation was carried out to study the frequency dependence of magnetic permeability via obtaining solutions of the Landau-Lifshitz-Gilbert (LLG) and the Maxwell's equations. The results indicate that the complex magnetic permeability peaks at a frequency of 6 GHz, corresponding to the ferromagnetic resonant (FMR) frequency, where the energy loss is maximum. A variation of the Gilbert damping parameter (?) associated with the LLG equation inversely affects this peak value. The area under the curve of complex magnetic permeability, calculated through counting the number of pixels within the image, provides an estimate of the average energy loss density within the material and appears to be consistent with the variation of the peak intensity.

Rustemaj, Driton; Mukherjee, Debashis

2013-01-01

60

Complex magnetic and electronic transport properties of (La,Gd){sub 1{minus}x}Sr{sub x}MnO{sub 3+{delta}} perovskites  

SciTech Connect

The magnetic and transport properties of (La,Gd){sub 1{minus}x}Sr{sub x}MnO{sub 3+{delta}} (x=0.15, 0.2, 0.25, and 0.3) with a fixed tolerance factor t=0.913 are studied. Special attention is paid to the postannealing effects of the compounds. Two magnetic transitions are observed in samples x=0.2 and 0.25 which are single phase in structure according to powder x-ray diffraction. Different effects on the two resulting states are produced by the postannealing. Accompanying the weakening of the state at lower temperature, the magnetic ordering of high-temperature state is enhanced substantially by the introduction of excess oxygen due to annealing the samples in O{sub 2}. One typical paramagnetic{endash}ferromagnetic transition occurs in samples x=0.15 and 0.3. There is a strong indication that the magnetic states in x=0.15 and 0.3 are, respectively, the developments of the high- and low-temperature states in x=0.2 (or x=0.25). The occurrence of two metal{endash}semiconductor transitions in x=0.15{endash}0.25 and their responses to postannealing suggest magnetic heterogeneity in the compound. By assuming the coexistence of vacancy-rich and vacancy-deficient domains in the compounds, these observations can be understood qualitatively. {copyright} {ital 1997 American Institute of Physics.}

Sun, J.R.; Rao, G.H.; Liang, J.K.; Shen, B.G. [State Key Laboratory for Magnetism, Institute of Physics and Center for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100080, Peoples Republic of (China)] [State Key Laboratory for Magnetism, Institute of Physics and Center for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100080, Peoples Republic of (China); Wong, H.K. [Department of Physics, The Chinese University of Hong Kong (Hong Kong)] [Department of Physics, The Chinese University of Hong Kong (Hong Kong)

1997-12-01

61

A novel single pot synthesis of binuclear copper(II) complexes of macrocyclic and macroacyclic compartmental ligands: Structures and magnetic properties  

NASA Astrophysics Data System (ADS)

Two binuclear copper(II) complexes one (complex 1) with a macrocyclic ligand (H 2L1) and other (complex 2) with a macroacyclic (end-off type) compartmental ligand (HL2) have been synthesized from single pot template synthesis involving copper(II) nitrate, 1,2-diaminoethane, 4-methyl-2,6-diformylphenol, and sodium azide. Structure analysis of complex 1 reveals that there are actually two half molecules present in the asymmetric unit and so two complexes (molecule-I and molecule-II) are present in unit cell, although they show slight differences. The two Cu(II) centers are in distorted square pyramidal coordination environment with two endogenous phenoxo bridges provided by the phenolate of H 2L1 having Cu-Cu separations of 2.9133(10) Å and 2.9103(10) in the two molecules. In complex 2 the coordination environments around two Cu(II) centers are asymmetric, Cu1 is in distorted square pyramidal environment whereas, the coordination environment around Cu2 is distorted octahedral. The two Cu(II) centers in complex 2 are connected by two different kinds of bridges, one is endogenous phenoxo bridge provided by the phenolate of the ligand HL2 and the other is exogenous azido bridge (? -1,1 type) with Cu-Cu distance of 3.032(10) Å. Variable temperature magnetic studies show that two Cu(II) centers in both the complexes are strongly antiferromagnetically coupled with J = -625 ± 5 cm -1 and J = -188.6 ± 1 cm -1 for complex 1 and 2, respectively.

Chattopadhyay, Tanmay; Banu, Kazi Sabnam; Banerjee, Arpita; Ribas, Joan; Majee, Adinath; Nethaji, Munirathinam; Das, Debasis

2007-05-01

62

Effect of sintering process on the magnetic and mechanical properties of sintered Nd-Fe-B magnets  

NASA Astrophysics Data System (ADS)

The magnetic and mechanical properties of sintered Nd-Fe-B magnets prepared by different sintering processes were investigated. The results showed that the intrinsic coercivity and fracture toughness of sintered Nd-Fe-B magnets first increased, and then declined with increasing annealing temperature. The optimum magnetic properties and fracture toughness of sintered Nd-Fe-B magnets were obtained at the annealing temperature of 540 °C. Sintering temperature increasing from 1047 °C to 1071 °C had hardly effect on the magnetic properties of sintered Nd-Fe-B magnets. The variation of Vickers hardness and fracture toughness was not the same with increasing sintering temperature, and the effect of sintering temperature on the mechanical properties was complex and irregular. The reasons for the variation on magnetic and mechanical properties were analyzed, and we presumed that the effect of microstructure on the mechanical properties was more sensitive than the magnetic properties through analyzing the microstructure of sintered Nd-Fe-B magnets.

Hu, Z. H.; Qu, H. J.; Zhao, J. Q.; Yan, C. J.; Liu, X. M.

2014-11-01

63

Hydrothermal syntheses, structures, and magnetic properties of two new Mn(II) complexes with biphenyl-2,3,3?,5?-tetracarboxylic acid  

NASA Astrophysics Data System (ADS)

Two metal-organic frameworks [Mn4(bptc)2(bpy)2]n (1) (H4bptc = biphenyl-2,3,3?,5?-tetra-carboxylic acid, bpy = 2, 2?-dipyridine) with Mn4 clusters and {[Mn2(bptc)2(H2O)8]?4H2O}(2) were obtained through hydrothermal reaction. X-ray diffraction analysis shows that both complexes 1 and 2 crystallize in the Triclinic system, space group of P-1. The Mn(II) ions have two kinds of coordination mode in complex 1, one is five- coordinated and the other is six-coordinated. Mn(2) ion is bridged to neighboring Mn(2)A(A:1 - x, 1 - y, 2 - z) by two ?2-Ocarboxyl atoms to afford a {Mn}4 cluster together with another two symmetrical Mn(1) and Mn(1)a. The {Mn}4 clusters are further connected through the bptc4- ligands each other, giving rise to a 2D network. There is a Mn2O2 parallelogram-core in every {Mn}4 cluster, and to the best of our knowledge this is the first time observed. Complex 2 consists of the dinuclear manganese (II) unit, which is further linked by hydrogen bonds to form a 3D framework structure. Magnetic measurements show there is a weak anti-ferromagnetic interaction in complex 1. Moreover, the IR, element analysis, and thermal stability of the two complexes have been investigated systemically.

Li, Rong-Fang; Liu, Xin-Fang; Zhang, Tian; Zhang, Xiao-Yu; Feng, Xun

2014-10-01

64

Magnetic properties of ferromagnetic ilmenites  

Microsoft Academic Search

Summary Magnetic and crystallographic properties of solid solutionsxFeTiO3. (1?x) Fe2O3 of hematite (Fe2O3) and ilmenite (FeTiO3), which have rhombohedral crystal structure, are examined in detail for the whole range of 0 ?x ? 1. Samples examined are mineral grains separated out from natural rocks and artificially synthesized ones. The minerals of the hematite-ilmenite series for 0.55x are ferromagnetic and their

T. Nagata; S. Akimoto

1956-01-01

65

New poly-iron(II) complexes of N4O dinucleating Schiff bases and pseudohalides: syntheses, structures, and magnetic and Mössbauer properties.  

PubMed

Six dinuclear ferrous complexes including [Fe2(acpypentO)(O2CMe)(NCS)2] (1), [Fe2(acpypentO)(O2CMe)(NCSe)2] (2), [Fe2(acpypentO)(NCO)3] (3), ([Fe2(acpybutO)(O2CMe)(NCS)2] (5), [Fe2(acpybutO)(O2CMe)(NCO)2] (6), and [Fe2(acpybutO)(O2CMe)(N3)2] (7), one tetranuclear (bis-dinuclear) ferrous compound, [Fe4(acpypentO)2(N3)6] (4), and one mononuclear ferrous compound, [Fe(acpybutOH)(NCS)2] (8), have been prepared, and their structures and magnetic and Mössbauer properties have been studied (acpybutOH = 1,4-bis[[2-pyridyl(1-ethyl]imino)]butane-2-ol and acpypentOH = 1,5-bis[[2-pyridyl(1-ethyl]imino)]pentane-3-ol). The X-ray diffraction analyses yielded the following results: 1 (C23H26Fe2N6O3S2, monoclinic, P2(1)/n, a = 8.0380(7) A, b = 12.4495(8) A, c = 27.358(2) A, beta = 92.180(10) degrees, V = 2735.7(4) A(3), Z = 4) is a dinuclear species in which the unequivalent high-spin (HS) Fe(II) sites are bridged by the alkoxo oxygen atom of the symmetrical acpypentO- Schiff base and one syn-syn acetato anion; 3 (C22H23Fe2N7O4, triclinic, Ponemacr;, a = 8.4152(10) A, b = 9.1350(10) A, c = 17.666(2) A, alpha = 97.486(14) degrees, beta = 100.026(14) degrees, gamma = 113.510(13) degrees, V = 1195.9(2) A3, Z = 2) is a dinuclear species in which the unequivalent HS Fe(II) sites are bridged by the alkoxo oxygen atom of the symmetrical acpypentO- Schiff base and one end-on NCO anion; 4-MeOH (C39H50Fe4N26O3, triclinic, Ponemacr;, a = 9.1246(11) A, b = 10.2466(11) A, c = 14.928(2) A, alpha = 91.529(15) degrees, beta = 101.078(16) degrees, gamma = 106.341(14) degrees, V = 1309.6(3) A3, Z = 1) is a bis-dinuclear species in which the unequivalent HS Fe(II) sites are bridged by the alkoxo oxygen atom of the symmetrical acpypentO- Schiff base and one end-on N(3)(-) anion, and the symmetry related Fe(II) sites are bridged by two end-on N3- anions; 8-MeOH (C21H26FeN6O2S2, triclinic, Ponemacr;, a = 8.7674(9) A, b = 12.0938(13) A, c = 12.2634(14) A, alpha = 106.685(14) degrees, beta = 93.689(14) degrees, gamma = 108.508(13) degrees, V = 1163.7(2) A3, Z = 2) is a mononuclear species in which the octahedral low-spin (LS) Fe(II) site is in an N6 environment provided by the four N atoms of the protonated asymmetrical acpybutOH Schiff base and two thiocyanato anions. The Mössbauer spectra of all dinuclear species (1-3 and 5-7), and of the bis-dinuclear compound 4, evidence two distinct HS Fe(II) sites while the Mössbauer spectra of the mononuclear compound 8 evidence a LS Fe(II) site over the 80-300 K temperature range. The temperature dependence of the magnetic susceptibility was fitted with J = -13.7 cm(-1), D = -1.8 cm(-1), and g = 2.096 for 1; J = 3.0 cm(-1), D(1) = 1.6 cm(-1), E(1) = -0.35 cm(-1) (lambda(1) = 0.22), D2 = - 12.2 cm(-1), E2 = 1.1 cm(-1) (lambda2 = 0.09), and g = 2.136 for 3; and J(1) = - 0.09 cm(-1), J(2) = 15.9 cm(-1), D(1) = 5.7 cm(-1), D(2) = 12.1 cm(-1), and g = 1.915 for 4. The nature of the ground state in 3 and 4 was confirmed by simulation of the magnetization curves at 2 and 5 K. The intradinuclear interaction through the central O(alkoxo) of the acpypentO- ligand and one pseudohalide bridges is ferromagnetic in 3 (end-on cyanato) while it is very weakly antiferromagnetic in 4 (end-on azido). The interdinuclear interaction through two end-on azido bridges (4) is ferromagnetic as expected. In agreement with the symmetry of the two iron sites of complexes 3 and 4, the fits show that D2 (tetragonal pyramid) is larger than D1 (distorted trigonal bipyramid (3) or distorted octahedron (4)). PMID:14966997

Boudalis, Athanassios K; Clemente-Juan, Juan-Modesto; Dahan, Françoise; Tuchagues, Jean-Pierre

2004-02-23

66

Controlling Magnetism of a Complex Metallic System Using Atomic Individualism  

NASA Astrophysics Data System (ADS)

When the complexity of a metallic compound reaches a certain level, a specific location in the structure may be critically responsible for a given fundamental property of a material while other locations may not play as much of a role in determining such a property. The first-principles theory has pinpointed a critical location in the framework of a complex intermetallic compound—Gd5Ge4—that resulted in a controlled alteration of the magnetism of this compound using precise chemical tools.

Mudryk, Y.; Paudyal, D.; Pecharsky, V. K.; Gschneidner, K. A., Jr.; Misra, S.; Miller, G. J.

2010-08-01

67

Properties of asymmetric magnetic reconnection  

SciTech Connect

Properties of magnetic reconnection are investigated in two-dimensional, resistive magnetohydrodynamic (MHD) simulations of current sheets separating plasmas with different magnetic field strengths and densities. Specific emphasis is on the influence of the external parameters on the reconnection rate. The effect of the dissipation in the resistive MHD model is separated from this influence by evaluating resistivity dependence together with the dependence on the background parameters. Two scenarios are considered, which may be distinguished as driven and nondriven reconnection. In either scenario, the maximum reconnection rate (electric field) is found to depend on appropriate hybrid expressions based on a magnetic field strength and an Alfven speed derived from the characteristic values in the two inflow regions. The scaling compares favorably with an analytic formula derived recently by Cassak and Shay [Phys. Plasmas 14, 102114 (2007)] applied to the regime of fast reconnection. An investigation of the energy flow and conversion in the vicinity of the reconnection site revealed a significant role of enthalpy flux generation, in addition to the expected conversion of Poynting flux to kinetic energy flux. This enthalpy flux generation results from Ohmic heating as well as adiabatic, that is, compressional heating. The latter is found more important when the magnetic field strengths in the two inflow regions are comparable in magnitude.

Birn, J.; Borovsky, J. E. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Hesse, M. [NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States)

2008-03-15

68

Preparation of molecule-based magnets from metal thiocyanate complexes  

NASA Astrophysics Data System (ADS)

The study of magnetism has enabled many technological applications that are ubiquitous in our daily life. Presently, most of the magnetic applications use metal/metal oxide magnets, which are readily available. In the last few decades, research has focused on a new class of magnetic materials, molecule-based magnets. This class of materials has diverse physical and chemical properties, which can be controlled by synthetic methods. Utilizing a variety of metals and ligands, researchers can control and fine tune various aspects of these magnetic materials, such as structural connections and possibly magnetic properties. Tetracyanoethylene (TCNE) is widely used in the preparation of molecule-based magnets due to its unique electronic and connectivity properties. TCNE has multiple binding sites, which gives it a diverse range of structural connectivity. Also, TCNE can be reduced easily to form a radical anion, which facilitates spin communication between metal centers allowing isolation of magnetically ordered systems such as V(TCNE)2 (a room temperature molecule-based magnet). M-TCNE magnets are prepared from solvated MII complexes or a metal carbonyl and TCNE in dichloromethane. The reaction involves the oxidation of the MII to MIII and the reduction of TCNE. More coordinating solvents used to prepare TCNE molecule-based magnets facilitate the dimerization of the radical TCNE, which does not allow for long-range ordering. The work presented herein will show the synthesis of MII thiocyanate complexes and their reaction with TCNE radical anion to yield M(TCNE)[C4(CN)8]1/2, which is obtained through ligand substitution between TCNE and thiocyanate. The development of new MII thiocyanate complexes through MII(NCMe)x(BF4)2 (x = 4, 6) in acetone, acetonitrile, and tetrahydrofuran will be the focus of Chapter 2. Also, in Chapter 2, structural and magnetic characterization will be discussed. Few of the metal thiocyanate complexes exhibit antiferromagnetic ordering at temperatures ranging from 8 to 50 K. Next the use of iron, manganese, and cobalt thiocyanate complexes for the preparation of M(TCNE)[C4(CN) 8]1/2 will be presented in Chapter 3. In Chapter 4, the effects of acetone and acetonitrile in the preparation of M-TCNE systems will be presented and structural and magnetic properties will be discussed. Mixed metal molecule-based magnets of the composition of M'xM''1-x (TCNE)[C4(CN)8]1/2 (M', M'' = Fe, Mn, Co) will be explored in Chapter 5. The metal composition ratios, coercive field, and critical temperature (T c) will be considered. Chapter 6 will cover some concluding remarks and some future directions towards the design and synthesis of new molecule-based magnets.

Shurdha, Endrit

69

Magnetization of rare earth\\/cobalt permanent magnets subsequent to assembly in complex rotor structures. Final report Jul 79Aug 81  

Microsoft Academic Search

The object of this program was to demonstrate the feasibility of magnetizing large rare earth\\/cobalt permanent magnets subsequent to their assembly in complex rotor structures. A safe demagnetization (to near zero remanence) technique was optimized and demonstrated on individual magnets with insignificant detrimental affect on the magnet physical properties. Magnetic finite element analysis was completed which optimized the winding location

D. N. Taneja; R. C. Webb; D. L. Martin

1982-01-01

70

Electronic and magnetic properties of nanographite ribbons  

Microsoft Academic Search

Electronic and magnetic properties of ribbon-shaped nanographite systems with zigzag and armchair edges in a magnetic field are investigated by using a tight binding model. One of the most remarkable features of these systems is the appearance of edge states, strongly localized near zigzag edges. The edge state in magnetic field, generating a rational fraction of the magnetic flux (\\\\phi=

Katsunori Wakabayashi; Mitsutaka Fujita; Hiroshi Ajiki; Manfred Sigrist

1999-01-01

71

Magnetic properties of ultra-small goethite nanoparticles  

NASA Astrophysics Data System (ADS)

Goethite (?-FeOOH) is a common nanocrystalline antiferromagnetic mineral. However, it is typically difficult to study the properties of isolated single-crystalline goethite nanoparticles, because goethite has a strong tendency to form particles of aggregated nanograins often with low-angle grain boundaries. This nanocrystallinity leads to complex magnetic properties that are dominated by magnetic fluctuations in interacting grains. Here we present a study of the magnetic properties of 5.7 nm particles of goethite by use of magnetization measurements, inelastic neutron scattering and Mössbauer spectroscopy. The ‘ultra-small’ size of these particles (i.e. that the particles consist of one or only a few grains) allows for more direct elucidation of the particles' intrinsic magnetic properties. We find from ac and dc magnetization measurements a significant upturn of the magnetization at very low temperatures most likely due to freezing of spins in canted spin structures. From hysteresis curves we estimate the saturation magnetization from uncompensated magnetic moments to be ?s = 0.044 A m2 kg-1 at room temperature. Inelastic neutron scattering measurements show a strong signal from excitations of the uniform mode (q = 0 spin waves) at temperatures of 100-250 K and Mössbauer spectroscopy studies show that the magnetic fluctuations are dominated by ‘classical’ superparamagnetic relaxation at temperatures above ˜170 K. From the temperature dependence of the hyperfine fields and the excitation energy of the uniform mode we estimate a magnetic anisotropy constant of around 1.0 × 105 J m-3.

Brok, E.; Frandsen, C.; Madsen, D. E.; Jacobsen, H.; Birk, J. O.; Lefmann, K.; Bendix, J.; Pedersen, K. S.; Boothroyd, C. B.; Berhe, A. A.; Simeoni, G. G.; Mørup, S.

2014-09-01

72

Modeling Magnetic Properties in EZTB  

NASA Technical Reports Server (NTRS)

A software module that calculates magnetic properties of a semiconducting material has been written for incorporation into, and execution within, the Easy (Modular) Tight-Binding (EZTB) software infrastructure. [EZTB is designed to model the electronic structures of semiconductor devices ranging from bulk semiconductors, to quantum wells, quantum wires, and quantum dots. EZTB implements an empirical tight-binding mathematical model of the underlying physics.] This module can model the effect of a magnetic field applied along any direction and does not require any adjustment of model parameters. The module has thus far been applied to study the performances of silicon-based quantum computers in the presence of magnetic fields and of miscut angles in quantum wells. The module is expected to assist experimentalists in fabricating a spin qubit in a Si/SiGe quantum dot. This software can be executed in almost any Unix operating system, utilizes parallel computing, can be run as a Web-portal application program. The module has been validated by comparison of its predictions with experimental data available in the literature.

Lee, Seungwon; vonAllmen, Paul

2007-01-01

73

Magnetic properties in graphene-graphane superlattices  

E-print Network

The magnetic properties of graphene-graphane superlattices with zigzag interfaces and separately varying widths are investigated by first-principles density functional calculations. It is demonstrated that magnetic states ...

Lee, Joo-Hyoung

74

Magnetic properties of hydrothermally recrystallized magnetite crystals  

Microsoft Academic Search

The discrepancy between the magnetic hysteresis properties of magnetite crystals that are precipitated from solution and of crushed sifted grains (larger than 300 nm) is not an inherent property of magnetite but is caused by the highly stressed state of crushed material and by adhering finer fragments. The size trends of magnetic properties exhibited by submicron-size precipitated grains continue in

Franz Heider; David J. Dunlop; Naoji Sugiura

1987-01-01

75

Topological defects and textures in complex magnets  

NASA Astrophysics Data System (ADS)

Magnetic materials support an astounding array of ordered phases, but some of the most interesting phenomena occur when conventional magnetic order is suppressed in the presence of competing interactions. Such frustrated magnets come in many forms, both classical and quantum. In this thesis I study three cases of frustrated magnetism---artificial spin ice, skyrmion crystals in chiral magnets, and the Kitaev honeycomb model, an exactly solvable quantum spin liquid. Spin ice is a phase of geometrically frustrated ferromagnets that is best known for giving rise to emergent magnetic monopoles. Spin ice on the kagome lattice finds its mesoscopic counterpart in artificial spin ice---a honeycomb network of single domain magnetic nanowires. In the first part of this work I present a model of magnetization reversal in artificial spin ice that is mediated by the magnetic charges moving through the system. The dynamics is dissipative and is influenced strongly by quenched disorder and Coulomb interactions between the charges. A skyrmion is a topologically stable magnetic texture where magnetization points in every possible direction on the sphere. Although it is tempting to think of such objects as regular point particles when solving for their low-energy dynamics, we found that due to their non-trivial topology, one has to take into account the geometric Berry phase---the time derivative term in the Lagrangian that is linear in velocity. Combining that with the elastic potential energy of a crystal, we arrive at the low-frequency spin wave spectrum for skyrmion crystals, which has two branches: a "magnetophonon" branch with a quadratic dispersion and a cyclotron branch with a finite frequency in the long-wavelength limit. Anyons are exotic quasiparticles with fractional exchange statistics that are conjectured to exist in two dimensional systems exhibiting topological order. Non-Abelian anyons are of particular interest due to their potential applications in quantum computing. The gapped phase of Kitaev's honeycomb model gives rise to Abelian anyons that are magnetic fluxes going through lattice plaquettes. In this work I demonstrate that introducing dislocations into the model enriches its properties by binding a zero energy Majorana mode to each defect. Majoranas from a dislocation pair can be combined into a non-local fermion mode that is created or annihilated whenever a flux winds around a dislocation. The nature of the flux itself also changes in this process, reflecting the non-Abelian exchange statistics associated with the dislocations.

Petrova, Olga

76

Thermodynamic properties of a magnetically modulated graphene  

E-print Network

The effect of magnetic modulation on thermodynamic properties of a graphene monolayer in presence of a constant perpendicular magnetic field is reported here. One-dimensional spatial electric or magnetic modulation lifts the degeneracy of the Landau levels and converts into bands and their band width oscillates with magnetic field leading to Weiss-type oscillation in the thermodynamic properties. The effect of magnetic modulation on thermodynamic properties of a graphene sheet is studied and then compared with electrically modulated graphene and magnetically modulated conventional two-dimensional electron gas (2DEG). We observe Weiss-type and de Haas-van Alphen (dHvA) oscillations at low and high magnetic field, respectively. There is a definite phase difference in Weiss-type oscillations in thermodynamic quantities of magnetically modulated graphene in compare to electrically modulated graphene. On the other hand, the phase remains same and amplitude of the oscillation is large when compared with the magneti...

Islam, SK Firoz; Ghosh, Tarun Kanti

2011-01-01

77

A 3D complex containing novel 2D CuII-azido layers: Structure, magnetic properties and effects of “Non-innocent” reagent  

NASA Astrophysics Data System (ADS)

A novel copper-azido coordination polymer, [Cu2(N3)3(L)]n (1, HL=pyrazine-2-carboxylic acid), has been synthesized by hydrothermal reaction with “Non-innocent” reagent in the aqueous solution. In the reaction system, CuII ions are avoided to reduce to CuI ions due to the existence of NdIII. It is found that the complex is a 3D structure based on two double EO azido bridged trimmers and octahedron CuII ions, in which the azide ligands take on EO and ?1,1,3 mode to form CuII-azido 2D layers, furthermore L ligands pillar 2D layers into an infinite 3D framework with the Schläfli symbol of {4;62}4{42;612;810;104}{42;64}. Magnetic studies revealed that the interactions between the CuII ions in the trimmer are ferromagnetic for the Cu-N-Cu angle nearly 98°, while the interactions between the trimmer and octahedron CuII ion are antiferromgantic and result in an antiferromagnetic state.

Gao, Xue-Miao; Guo, Qian; Zhao, Jiong-Peng; Liu, Fu-Chen

2012-12-01

78

Magnetic Properties of Intermetallic Uranium Compounds.  

National Technical Information Service (NTIS)

Magnetic properties of intermetallic uranium compounds have been investigated. The magnetic properties were studied at zero pressure in fields up to 35T. Their pressure dependences were investigated at pressures up to 8kbar in fields up to 10T. Specific h...

P. H. Frings

1984-01-01

79

Magnetic properties of HoTiGe  

Microsoft Academic Search

The magnetic properties of the compound HoTiGe have been studied by means of magnetization measurements at different temperatures and fields. The results show that the material displays an antiferromagnetic-to-paramagnetic phase transition in low fields and a field-induced antiferromagnetic-to-ferromagnetic transition at higher field strengths. From the magnetization data, the magnetic sublattice exchange coupling constants n11 and n12 have been determined based

O. Tegus; E. H. Bruck; J. C. P. Klaasse; K. H. J. Buschow; F. R. de Boer

2001-01-01

80

Two molecular wheels 12-MC-6 complexes: Synthesis, structure and magnetic property of [Co(?{sub 2}-SEt){sub 2}]{sub 6} and [Fe(?{sub 2}-SEt){sub 2}]{sub 6}  

SciTech Connect

The syntheses and structures of two ethyl mercaptan molecular wheels complexes, [M(?{sub 2}-SCH{sub 2}CH{sub 3}){sub 2}]{sub 6} (M=Fe, Co), have been reported. Each metal atom is surrounded by four S atoms of the ?{sub 2}-SCH{sub 2}CH{sub 3} ligands in a distorted square plane fashion. The edge-sharing S{sub 4} square planes connect with each other to form a ring. Six metal atoms are located at the vertices of an almost hexagon, with M···M separations in the range of 2.903(1)?2.936(2) Å for Fe and 2.889(2)?2.962(2) Å for Co. The diameter of the ring, defined as the average distance between two opposing metal atoms, is 5.850(1) Å for Fe and 5.780(1) Å for Co, respectively. The magnetic property behaves of cobalt(II) cluster complex is studied. Highlights: • Two new ethyl mercaptan cyclic hexanuclear complexes were reported. • The crystal structures shown center formation of M{sub 6}S{sub 12} molecular wheels. • The Co{sub 6} ring cluster complex represents as weak ferromagnet.

Wang, Jing [New Materials and Function Coordination Chemistry Laboratory, Qingdao University of Science and Technology, Qingdao, Shandong 266042 (China); Jian, Fangfang, E-mail: ffj2003@163169.net [New Materials and Function Coordination Chemistry Laboratory, Qingdao University of Science and Technology, Qingdao, Shandong 266042 (China); Huang, Baoxin [Microscale Science Institute, Weifang Colledge, Weifang 261061, PR China. (China); Bai, Zhengshuai [New Materials and Function Coordination Chemistry Laboratory, Qingdao University of Science and Technology, Qingdao, Shandong 266042 (China)

2013-08-15

81

The effect of intrinsic magnetic properties on permanent magnet repulsion  

Microsoft Academic Search

Magnetic repulsion is currently under active consideration as a means for providing quiet, frictionless suspension for future tracked ground transportation vehicles and for providing high-reliability, long-lived, friction-free bearings for unique new devices and components. Analytical and experimental results indicate that the superior intrinsic magnetic properties of certain members of a new class of permanent magnet materials, the rare-earth-cobalts (including PrCo5and

JAMES B. Y. TSUI; DAVID J. IDEN; KARL J. STRNAT; ANTHONY J. EVERS

1972-01-01

82

Thermodynamic properties of a magnetically modulated graphene  

E-print Network

The effect of magnetic modulation on thermodynamic properties of a graphene monolayer in presence of a constant perpendicular magnetic field is reported here. One-dimensional spatial electric or magnetic modulation lifts the degeneracy of the Landau levels and converts into bands and their band width oscillates with magnetic field leading to Weiss-type oscillation in the thermodynamic properties. The effect of magnetic modulation on thermodynamic properties of a graphene sheet is studied and then compared with electrically modulated graphene and magnetically modulated conventional two-dimensional electron gas (2DEG). We observe Weiss-type and de Haas-van Alphen (dHvA) oscillations at low and high magnetic field, respectively. There is a definite phase difference in Weiss-type oscillations in thermodynamic quantities of magnetically modulated graphene in compare to electrically modulated graphene. On the other hand, the phase remains same and amplitude of the oscillation is large when compared with the magnetically modulated 2DEG. Explicit asymptotic expressions of density of states and the Helmholtz free energy are provided to understand the phase and amplitude of the Weiss-type oscillations qualitatively. We also study thermodynamic properties when both electric and magnetic modulations are present. The Weiss-type oscillations still exist when the modulations are out-of-phase.

SK Firoz Islam; Naveen K. Singh; Tarun Kanti Ghosh

2011-07-15

83

Optical and Magnetic Properties of Dust Grains  

E-print Network

The optical and magnetic properties of dust grains are reviewed, as they relate to the problem of interstellar grain alignment. Grain geometry plays an important role in determining the optical properties, and scattering and absorption of starlight will produce radiative torques which may drive grains to suprathermal rates of rotation in interstellar clouds; these radiative torques appear likely to play an active role in the alignment process. The likely magnetic properties of grains are discussed, with particular attention to the imaginary part of the magnetic susceptibility.

B. T. Draine

1996-03-13

84

Properties of Simulated Magnetized Galaxy Clusters  

E-print Network

We study the evolution of magnetized clusters in a cosmological environment using magneto-hydro dynamical simulations. Large scale flows and merging of subclumps generate shear flows leading to Kelvin-Helmholtz instabilities, which, in addition to the compression of the gas where the magnetic field is frozen in, further amplify the magnetic field during the evolution of the cluster. Therefore, well-motivated initial magnetic fields of $^{1/2}=10^{-9} {\\rm G}$ reach the observed $\\sim\\mu{\\rm G}$ field strengths in the cluster cores at $z=0$. These magnetized clusters can be used to study the final magnetic field structure, the dynamical importance of magnetic fields for the interpretation of observed X-Ray properties, and help to constrain further processes in galaxy clusters like the population of relativistic particles giving rise to the observed radio halos or the behavior of magnetized cooling flows.

Klaus Dolag

2000-10-07

85

Magnetic Properties of Organic Coated Gold Surfaces  

NASA Astrophysics Data System (ADS)

We review here our recent results of experimental observation of room temperature magnetism in gold nanoparticles (NPs) and thin films. Capping gold surfaces with certain organic molecules leads to the appearance of magnetism at room temperature. The surface bonds between the organic molecules and Au atoms give rise to magnetic moments. These magnetic moments are blocked along the bond direction showing huge anisotropy. In the case of atomically flat surfaces, the magnetic moments are giants. An explanation of this orbital ferromagnetism is given. These results point out the possibility to observe magnetism at nanoscale in materials without typical magnetic atoms (transition metals and rare earths), and are of fundamental value to understand the magnetic properties of surfaces.

de La Venta, J.; Fernandez Pinel, E.; Garcia, M. A.; Crespo, P.; Hernando, A.; de La Fuente, O. Rodriguez; de Julián Fernández, C.; Fernández, A.; Penadés, S.

86

Electrical properties of chain microstructure magnetic emulsions in magnetic field  

E-print Network

The work deals with the experimental study of the emulsion whose dispersion medium is a magnetic fluid while the disperse phase is formed by a glycerin-water mixture. It is demonstrated that under effect of a magnetic field chain aggregates form from the disperse phase drops. Such emulsion microstructure change affects its macroscopic properties. The emulsion dielectric permeability and specific electrical conductivity have been measured. It is demonstrated that under the effect of relatively weak external magnetic fields (~ 1 kA/m) the emulsion electrical parameters may change several fold. The work theoretically analyzes the discovered regularities of the emulsion electrical properties.

Arthur Zakinyan; Yuri Dikansky; Marita Bedzhanyan

2014-02-05

87

Magnetic and optoelectronic properties of gold nanocluster-thiophene assembly.  

PubMed

Nanohybrids consisting of Au nanocluster and polythiophene nanowire assemblies exhibit unique thermal-responsive optical behaviors and charge-transfer controlled magnetic and optoelectronic properties. The ultrasmall Au nanocluster enhanced photoabsorption and conductivity effectively improves the photocurrent of nanohybrid based photovoltaics, leading to an increase of power conversion efficiency by 14?% under AM 1.5 illumination. In addition, nanohybrids exhibit electric field controlled spin resonance and magnetic field sensing behaviors, which open up the potential of charge-transfer complex system where the magnetism and optoelectronics interact. PMID:24853729

Qin, Wei; Lohrman, Jessica; Ren, Shenqiang

2014-07-01

88

Zero-field slow magnetic relaxation in a uranium(III) complex with a radical ligand.  

PubMed

[U(Tp(Me2))2(bipy?)], a uranium(III) complex with a radical bipyridine ligand which has magnetic properties with contributions from both the ligand and the metal, presents slow relaxation of the magnetisation at low temperatures, already under zero static magnetic field, and energy barriers slightly above the non-radical analogues. PMID:25056758

Coutinho, Joana T; Antunes, Maria A; Pereira, Laura C J; Marçalo, Joaquim; Almeida, Manuel

2014-09-14

89

Correlation properties of magnetosheath magnetic field fluctuations  

Microsoft Academic Search

The magnetosheath is characterized by a variety of low-frequency fluctuations, but their features and sources are different. Taking advantage of multipoint magnetic field measurements of the Cluster spacecraft, we present a statistical study to reveal properties of waves. We compute cross-correlation coefficients of magnetic field strengths as measured by pairs of the Cluster spacecraft and determine the correlation length of

O. Gutynska; J. Šafránková; Z. N?me?ek

2009-01-01

90

Magnetic properties of some opal-based nanocomposites  

NASA Astrophysics Data System (ADS)

Nanoparticles of complex titanium, cobalt, and manganese oxides with ilmenite and spinel structure have been synthesized in pores of an opal. The particle composition has been determined by X-ray diffraction analysis. The magnetic properties of the obtained nanocomposites with different particles embedded in pores have been studied. The temperature dependences of the dc and ac magnetizations in the range from 2 to 300 K have been measured. It has been shown that the magnetic ordering in all the nanocomposites studied emerges at temperatures above 150 K, which not in all cases can be related directly to the properties of the materials identified by X-ray diffraction. The appearance of peaks in the ZFC susceptibility and ac magnetization curves below 50 K is assigned to disordering and frustration in nanoparticles of titanates of the type of CoTiO3, NiTiO3, and Co2TiO4.

Lee, M. K.; Charnaya, E. V.; Tien, C.; Samoilovich, M. I.; Chang, L. J.; Mikushev, V. M.

2013-03-01

91

Unsymmetrical Bimetallic Complexes with MII-(?-OH)-MII Cores (MIIMIII = FeIIFeIII, MnIIFeIII, MnIIMnIII): Structural, Magnetic, and Redox Properties  

PubMed Central

Heterobimetallic cores are important unit within the active sites of metalloproteins, but are often difficult to duplicate in synthetic systems. We have developed a synthetic approach for the preparation of a complex with a MnII–(?-OH)–FeIII core, in which the metal centers have different coordination environments. Structural and physical data support the assignment of this complex as a heterobimetallic system. Comparison with the analogous homobimetallic complexes, those containing MnII–(?-OH)–MnIII and FeII–(?-OH)–FeIII cores, further supports this assignment. PMID:23992041

Sano, Yohei; Weitz, Andrew C.; Ziller, Joseph W.; Hendrich, Michael P.; Borovik, A.S.

2013-01-01

92

Magnetic Properties of the Proton and Neutron  

SciTech Connect

The magnetic moment and magnetic polarisability are important fundamental properties of particles such as the proton. They describe the interaction with and response to an applied magnetic field. The ability to calculate values for these observables from the first principles of QCD at the quark level is at the leading edge of lattice QCD research. An overview of how these calculations are performed on the lattice is presented. A quantised magnetic field is applied to the periodic space-time lattice using the background-field method. Values of the magnetic moment and magnetic polarisability for the proton and neutron are reported using this method. These values are calculated on a large lattice, allowing for a reasonably small magnetic field strength, making these the world's first quantitative results.

Primer, Thomas; Kamleh, Waseem; Leinweber, Derek B. [Special Research Centre for the Subatomic Structure of Matter, School of Chemistry and Physics, University of Adelaide (Australia)

2011-05-24

93

Ultrasonic properties of EMG-605 magnetic liquid  

NASA Astrophysics Data System (ADS)

The study of ultrasonic properties of water-based magnetic fluid EMG-605 is presented. The measurements of velocity and attenuation of ultrasound were carried out as a function of temperature, frequency, magnetic field strength and the angle between the wave and the direction of magnetic liquid. The model takes into account mutual interaction of magnetic clusters giving skeleton"s stiffness and interaction of clusters with free liquid producing attenuation and dispersion of waves for transversally isotropic system. A good agreement between experimental data and the predictions of theoretical model was obtained.

Hornowski, Tomasz

2005-03-01

94

Magnetic anisotropy in the excited states of low symmetry lanthanide complexes.  

PubMed

Ab initio investigation of multiplet spectrum of lanthanides in archetypal coordination geometries shows an unexpected regular structure consisting of (i) mirror symmetry of anisotropic magnetic properties of doublet states, (ii) high magnetic axiality of low-lying and high-lying doublets, comparable to complexes with ideal axial symmetry, and (iii) the strong rotation of the anisotropy axes of individual doublets. The obtained high axiality of the ground doublet states explains the SMM behaviour of low-symmetry lanthanide complexes. PMID:22027865

Ungur, Liviu; Chibotaru, Liviu F

2011-12-01

95

Magnetic property and thermal analysis of a Mn(II) complex with [Mn(CO2)]n chains based on 4,4?-bis(1H-imidazol-1-yl-methyl)biphenyl  

NASA Astrophysics Data System (ADS)

Magnetic coordination polymers have attracted considerable interest due to their novel structures and potential applications. In this paper, one new 2D magnetic manganese coordination polymer {[Mn(bimb)(OBA)]}n (1) was synthesized under solvothermal conditions based on 4,4?-bis(1H-imidazol-1-yl-methyl)biphenyl (bimb) and 4,4?-oxybis(benzoate) (H2OBA). Complex 1 contains [Mn(CO2)]n 1D chains and magnetic susceptibility measurements indicate that compound 1 exhibits an antiferromagnetic coupling interaction. In addition, complex 1 exhibits solid-state photoluminescence and high thermal stability.

Zhang, Ming-Dao; Zheng, Bao-Hui; Wang, Zhe; Jiao, Yan; Chen, Min-Dong

2014-11-01

96

Magnetic properties of Ni fine particles  

NASA Astrophysics Data System (ADS)

Magnetic properties of Ni fine particles, 3 nm in diameter, dispersed in an oil by a surface-active agent were examined by magnetization and Mössbauer measurements. From the magnetization measurements, the particles were found superparamagnetic at temperatures above about 40 K. The saturation magnetization at 4.2 K was reduced to 50% of that of bulk Ni. Mössbauer effect was measured for 57Fe-doped Ni particles and it was shown that the particles were not oxidized. A component ascribed to surface atoms was detected in the Mössbauer spectrum. The hyperfine field of 57Fe at 4.2 K was found to be smaller than that in bulk Ni correspondingly to the reduction of the magnetization. The Ni magnetic moment is considered to be reduced in the fine particles.

Furubayashi, T.; Nakatani, I.

1990-05-01

97

Irreversible magnetic properties of carbon nanoparticles  

NASA Astrophysics Data System (ADS)

Magnetic properties of powder and glassy samples with carbon nanoparticles. not intentionally doped and doped with Ag, Au and Co, are investigated at temperatures T ~ 3 — 300 K in magnetic fields B up to 5 T. Magnetization M (T) exhibits in low fields of B = 1 — 50 mT a strong irreversibility, which is suppressed above B ~ 1 T. The high-temperature (T ~ 200 — 300 K) dependence of M on B demonstrates a saturation above B ~ 2 T. Magnetic hysteresis is observed already at 300 K. exhibiting a power-law temperature decay of the coercive field. Analysis of the experimental data suggests a concentration of the magnetization close to the surface of the carbon nanoparticles. This is consistent with the origin of magnetism in nanocarbon due to intrinsic surface defects. Deviations of macroscopic and microscopic parameters in the Co-doped sample from those in the other samples imply an influence of the Co ions and/or clusters.

Lähderanta, E.; Lashkul, A. V.; Lisunov, K. G.; Zherebtsov, D. A.; Galimov, D. M.; Titkov, A. N.

2013-01-01

98

Molecular and all solid DFT studies of the magnetic and chemical bonding properties within KM[Cr(CN)$_6$] (M = V, Ni) complexes  

E-print Network

A study at both the molecular and extended solid level in the framework DFT is carried out for KM[Cr(CN)$_6$] (M = V, Ni). From molecular calculations, the exchange parameters J are obtained, pointing to the expected magnetic ground states, i.e., antiferromagnetic for M = V with J = -296.5 cm$^{-1}$ and ferromagnetic for M = Ni with J = +40.5 cm$^{-1}$. From solid state computations the same ground states and J magnitudes are confirmed from energy differences. Furthermore an analysis of the site projected density of states and of the chemical bonding is developed in which the cyanide ion linkage is analyzed addressing some isomerism aspects.

L. Kabalan; S. F. Matar; C. Desplanches; J. F. Létard; M. Zakhour

2008-02-25

99

Crystal field and magnetic properties  

NASA Technical Reports Server (NTRS)

Magnetization and magnetic susceptibility measurements have been made in the temperature range 1.3 to 4.2 K on powdered samples of ErH3. The susceptibility exhibits Curie-Weiss behavior from 4.2 to 2 K, and intercepts the negative temperature axis at theta = 1.05 + or - 0.05 K, indicating that the material is antiferromagnetic. The low field effective moment is 6.77 + or - 0.27 Bohr magnetons per ion. The magnetization exhibits a temperature independent contribution, the slope of which is (5 + or - 1.2) x 10 to the -6th Weber m/kg Tesla. The saturation moment is 3.84 + or - 1 - 0.15 Bohr magnetons per ion. The results can be qualitatively explained by the effects of crystal fields on the magnetic ions. No definitive assignment of a crystal field ground state can be given, nor can a clear choice between cubically or hexagonally symmetric crystal fields be made. For hexagonal symmetry, the first excited state is estimated to be 86 to 100 K above the ground state. For cubic symmetry, the splitting is on the order of 160 to 180 K.

Flood, D. J.

1977-01-01

100

Magnetic properties of the Esquel Pallasite  

NASA Astrophysics Data System (ADS)

Pallasites are stony-iron meteorites consisting mainly of olivine crystals suspended in an iron-nickel matrix. One hypothesis holds that pallasites are formed from the intrusion of a liquid iron-nickel core into the solid silicate mantle of a parent body. The magnetic properties of the olivine crystals could help provide insight into the veracity of this explanation. The olivine crystals may contain magnetic inclusions that record useful information regarding magnetic fields present in the parent body. The best recorders of magnetic information are single domain in nature; domain structure of magnetic inclusions can be examined by recording their hysteresis properties. Olivine crystals were separated from a sample of the Esquel pallasite. Crystal fragments were often stained or coated with non-olivine minerals, which required cleaning to remove. An Alternating Gradient Force Magnetometer (AGFM) was used to measure magnetic hysteresis properties, and a Superconducting Quantum Interface Device Cryogenic Rock Magnetometer was used to measure the natural remanent magnetization of the samples. Preliminary data indicate single domain carriers in select olivine crystals that carry records of strong ancient fields. This is a presentation of preliminary results collected during a summer REU at the University of Rochester.

Erickson, A. M.; Tarduno, J. A.; Cottrell, R. D.

2009-12-01

101

Tailoring Magnetic Properties in Bulk Nanostructured Solids  

NASA Astrophysics Data System (ADS)

Important magnetic properties and behaviors such as coercivity, remanence, susceptibility, energy product, and exchange coupling can be tailored by controlling the grain size, composition, and density of bulk magnetic materials. At nanometric length scales the grain size plays an increasingly important role since magnetic domain behavior and grain boundary concentration determine bulk magnetic behavior. This has spurred a significant amount of work devoted to developing magnetic materials with nanometric features (thickness, grain/crystallite size, inclusions or shells) in 0D (powder), 1D (wires), and 2D (thin films) materials. Large 3D nanocrystalline materials are more suitable for many applications such as permanent magnets, magneto-optical Faraday isolators etc. Yet there are relatively few successful demonstrations of 3D magnetic materials with nanoscale influenced properties available in the literature. Making dense 3D bulk materials with magnetic nanocrystalline microstructures is a challenge because many traditional densification techniques (HIP, pressureless sintering, etc.) move the microstructure out of the "nano" regime during densification. This dissertation shows that the Current Activated Pressure Assisted Densification (CAPAD) method, also known as spark plasma sintering, can be used to create dense, bulk, magnetic, nanocrystalline solids with varied compositions suited to fit many applications. The results of my research will first show important implications for the use of CAPAD for the production of exchange-coupled nanocomposite magnets. Decreases in grain size were shown to have a significant role in increasing the magnitude of exchange bias. Second, preferentially ordered bulk magnetic materials were produced with highly anisotropic material properties. The ordered microstructure resulted in changing magnetic property magnitudes (ex. change in coercivity by almost 10x) depending on the relative orientation (0° vs. 90°) of an externally applied magnetic field to the sample. Third, a dense magneto-optical material (rare earth oxide) was produced that rotates transmitted polarized light under an externally applied magnetic field, called the Faraday Effect. The magnitude of the rare earth oxide Faraday Effect surpasses that of the current market leader (terbium gallium garnet) in Faraday isolators by ˜2.24x.

Morales, Jason Rolando

102

Synthesis, crystal structure, magnetic property and oxidative DNA cleavage activity of an octanuclear copper(II) complex showing water-perchlorate helical network.  

PubMed

A new octanuclear copper(II) complex has been synthesized and structurally characterized by X-ray crystallography: [Cu(8)(HL)(4)(OH)(4)(H(2)O)(2)(ClO(4))(2)].(ClO(4))(2).2H(2)O (1) (H(3)L=2,6-bis(hydroxyethyliminoethyl)-4-methyl phenol). The complex is formed by the linkage of two terminal bimetallic cationic units and a tetranuclear mu(3)-hydroxo bridged dicubane core by a very short intramolecular hydrogen bond (O-H...O, 1.48(3)A and the angle 175 degrees). The coordination sphere of the terminal copper atoms is square pyramidal, the apical positions being occupied by water and a perchlorate ion. Complex 1 self-assembles to form a new type of water-perchlorate helical network [(H(2)O)(2)(ClO(4))](infinity) involving oxygen atoms of coordinated perchlorate ion and the two lattice water molecules through hydrogen-bonding interaction. The variable temperature-dependent susceptibility measurement (2-300K) of 1 reveals a strong antiferromagnetic coupling, J(1)=-220cm(-1) and J(2)=-98cm(-1) (J(1) and J(2) representing the exchange constant within [Cu(2+)](4) and [Cu(2+)](2) units, respectively). The complex binds to double-stranded supercoiled plasmid DNA giving a K(app) value of 1.2x10(7)M(-1) and displays efficient oxidative cleavage of supercoiled DNA in the presence of H(2)O(2) following a hydroxyl radical pathway. PMID:17045341

Dhara, Koushik; Ratha, Jagnyeswar; Manassero, Mario; Wang, Xin-Yi; Gao, Song; Banerjee, Pradyot

2007-01-01

103

Electrostatic complexation of polyelectrolyte and magnetic nanoparticles: from wild clustering to controllable magnetic wires  

NASA Astrophysics Data System (ADS)

We present the electrostatic complexation between polyelectrolytes and charged nanoparticles. The nanoparticles in solution are ?-Fe2O3 (maghemite) spheres with 8.3 nm diameter and anionic surface charges. The complexation was monitored using three different formulation pathways such as direct mixing, dilution, and dialysis. In the first process, the hybrids were obtained by mixing stock solutions of polymers and nanoparticles. A `destabilization state' with sharp and intense maximum aggregation was found at charges stoichiometry (isoelectric point). While on the two sides of the isoelectric point, `long-lived stable clusters state' (arrested states) were observed. Dilution and dialysis processes were based on controlled desalting kinetics according to methods developed in molecular biology. Under an external magnetic field ( B = 0.3 T), from dialysis at isoelectric point and at arrested states, cationic polyelectrolytes can `paste' these magnetic nanoparticles (NPs) together to yield irregular aggregates (size of 100 ?m) and regular rod-like aggregates, respectively. These straight magnetic wires were fabricated with diameters around 200 nm and lengths comprised between 1 ?m and 0.5 mm. The wires can have either positive or negative charges on their surface. After analyzing their orientational behavior under an external rotating field, we also showed that the wires made from different polyelectrolytes have the same magnetic property. The recipe used a wide range of polyelectrolytes thereby enhancing the versatility and applied potentialities of the method. This simple and general approach presents significant perspective for the fabrication of hybrid functional materials.

Yan, Minhao; Qu, Li; Fan, Jiangxia; Ren, Yong

2014-05-01

104

Multiple Regulated Assembly, Crystal Structures and Magnetic Properties of Porous Coordination Polymers with Flexible Ligands  

E-print Network

of the lattice water molecules during the heat treatment. Complex 2 can be re- Introduction Porous coordinationFULL PAPER Multiple Regulated Assembly, Crystal Structures and Magnetic Properties of Porous,[c] and Lin-Pei Jin*[a] Keywords: Cobalt / Coordination polymers / Magnetic properties / Nickel / Porous

Gao, Song

105

Magnetic circular dichroism of porphyrin lanthanide m(3+) complexes.  

PubMed

Lanthanide complexes exhibit interesting spectroscopic properties yielding many applications as imaging probes, natural chirality amplifiers, and therapeutic agents. However, many properties are not fully understood yet. Therefore, we applied magnetic circular dichroism (MCD) spectroscopy, which provides enhanced information about the underlying electronic structure to a series of lanthanide compounds. The metals in the M(3+) state included Y, La, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu; the spectra were collected for selected tetraphenylporphin (TPP) and octaethylporphin (OEP) complexes in chloroform. While the MCD and UV-VIS absorption spectra were dominated by the porphyrin signal, metal binding significantly modulated them. MCD spectroscopy was found to be better suited to discriminate between various species than absorption spectroscopy alone. The main features and trends in the lanthanide series observed in MCD and absorption spectra of the complexes could be interpreted at the Density Functional Theory (DFT) level, with effective core potentials on metal nuclei. The sum over state (SOS) method was used for simulation of the MCD intensities. The combination of the spectroscopy and quantum-chemical computations is important for understanding the interactions of the metals with the organic compounds. Chirality 26:655-662, 2014. © 2014 Wiley Periodicals, Inc. PMID:25116761

Andrushchenko, Valery; Padula, Daniele; Zhivotova, Elena; Yamamoto, Shigeki; Bou?, Petr

2014-10-01

106

Copper(II) and zinc(II) complexes with Schiff-base ligands derived from salicylaldehyde and 3-methoxysalicylaldehyde: Synthesis, crystal structures, magnetic and luminescence properties  

Microsoft Academic Search

The following Schiff bases were employed as ligands in synthesizing copper(II) and zinc(II) complexes: N-[(2-pyridyl)-methyl]-salicylimine (Hsalampy), N-[2-(N,N-dimethyl-amino)-ethyl]-salicylimine (Hsaldmen), and N-[(2-pyridyl)-methyl]-3-methoxy-salicylimine (Hvalampy). The first two ligands were obtained by reacting salicylaldehyde with 2-aminomethyl-pyridyne and N,N-dimethylethylene diamine, respectively, while the third one results from the condensation of 3-methoxysalicylaldehyde with 2-aminomethyl-pyridine. Four new coordination compounds were synthesized and structurally characterized: [Cu(salampy)(H2O)(ClO4)] 1, [Cu2(salampy)2(H2trim)2

Catalin Maxim; Traian D. Pasatoiu; Victor Ch. Kravtsov; Sergiu Shova; Christopher A. Muryn; Richard E. P. Winpenny; Floriana Tuna; Marius Andruh

2008-01-01

107

Magnetic properties of colloidal cobalt nanoclusters  

NASA Astrophysics Data System (ADS)

Co nanoclusters were synthesized by an inverse-micelle chemical route. The magnetic and microstructural properties of the nanoparticles have been analyzed as a function of the surfactant (AOT and DEHP) and the drying method. Microstructural analysis has been performed by TEM and XANES; magnetic properties have been studied by hysteresis loops and zero-field cooling - field cooling (ZFC-FC) curves. TEM images show 2 to 4 nm sized particles spherical in shape. XANES measurements point out a significant presence of Co3O4with metallic Co and some Co2+ bound to the surfactant. The presence of antiferromagnetic Co3O4 explains the magnetic transition observed at low T in both ZFC-FC measurements and hysteresis loops. Finally, the presence of magnetic interactions explains the bigger effective cluster size obtained from hysteresis loops fits (6-10 nm) compared to the sizes observed by TEM (2-4 nm).

Torchio, R.; Meneghini, C.; Mobilio, S.; Capellini, G.; García Prieto, A.; Alonso, J.; Fdez-Gubieda, M. L.; Turco Liveri, V.; Longo, A.; Ruggirello, A. M.; Neisius, T.

2010-01-01

108

Ordered Magnetic Nanostructures. Fabrication and Properties  

Microsoft Academic Search

Abstract The fabrication,methods,and,physical properties,of ordered,magnetic,nanostructures,with,dimensions,on the submicron to nanometer scale are reviewed. First, various types of nanofabrication techniques are described, and their capabilities and limitations in achieving magnetic nanostructures are discussed. Specifically, we address electron beam lithography, X-ray lithography, laser interference lithography, scanning probe lithography, step growth methods, nanoimprint, shadowmasks, radiation damage, self-assembled structures, and the use of nanotemplates. Then

J. I. Martin; J. Nogues; Kai Liu; J. L. Vicent; Ivan K. Schuller

2003-01-01

109

Magnetic properties of ultrafine iron particles  

Microsoft Academic Search

The magnetic and morphological properties of fine Fe particles have been studied. Ultrafine particles of Fe were prepared using a vapor deposition technique under an argon atmosphere. The argon pressure was varied from 0.5 to 8 Torr during evaporation, and samples with a median diameter in the range 50-200 Å were obtained having a log-normal distribution. The dependence of magnetic

S. Gangopadhyay; G. C. Hadjipanayis; B. Dale; C. M. Sorensen; K. J. Klabunde; V. Papaefthymiou; A. Kostikas

1992-01-01

110

Magnetic Properties of a Rotating Superconductor  

Microsoft Academic Search

The magnetic properties of a superconductive lead sphere have been studied through the measurement of the voltage induced between the axis and the periphery of the sphere rotated as a Faraday disk at constant speed in an axial magnetic field. Measurements were made in the range 0-10,800 r.p.m. The data are consistent in all details, including critical field and the

Aaron Wexler; W. S. Corak

1950-01-01

111

New cyanide-bridged Mn(III)-M(III) heterometallic dinuclear complexes constructed from [M(III)(AA)(CN)4]- building blocks (M = Cr and Fe): synthesis, crystal structures and magnetic properties.  

PubMed

Three Mn(III)-M(III) (M = Cr and Fe) dinuclear complexes have been obtained by assembling [Mn(III)(SB)(H(2)O)](+) and [M(III)(AA)(CN)(4)](-) ions, where SB is the dianion of the Schiff-base resulting from the condensation of 3-methoxysalicylaldehyde with ethylenediamine (3-MeOsalen(2-)) or 1,2-cyclohexanediamine (3-MeOsalcyen(2-)): [Mn(3-MeOsalen)(H(2)O)(µ-NC)Cr(bipy)(CN)(3)]·2H(2)O (1), [Mn(3-MeOsalen)(H(2)O)(µ-NC)Cr(ampy)(CN)(3)][Mn(3-MeOsalen)(H(2)O)(2)]ClO(4)·2H(2)O (2) and [Mn(3-MeOsalcyen)(H(2)O)(µ-NC)Fe(bpym)(CN)(3)]·3H(2)O (3) (bipy = 2,2'-bipyridine, ampy = 2-aminomethylpyridine and bpym = 2,2'-bipyrimidine). The [M(AA)(CN)(4)](-) unit in 1-3 acts as a monodentate ligand towards the manganese(III) ion through one of its four cyanide groups. The manganese(III) ion in 1-3 exhibits an elongated octahedral stereochemistry with the tetradentate SB building the equatorial plane and a water molecule and a cyanide-nitrogen atom filling the axial positions. Remarkably, the neutral mononuclear complex [Mn(3-MeOsalen)(H(2)O)(2)]ClO(4) co-crystallizes with the heterobimetallic unit in 2. The values of the Mn(III)-M(III) distance across the bridging cyanide are 5.228 (1), 5.505 (2) and 5.265 Å (3). The packing of the neutral heterobimetallic units in the crystal is governed by the self-complementarity of the [Mn(SB)(H(2)O)](+) moieties, which interact each other through hydrogen bonds established between the aqua ligand from one fragment with the set of phenolate- and methoxy-oxygens from the adjacent one. The magnetic properties of the three complexes have been investigated in the temperature range 1.9-300 K. Weak antiferromagnetic interactions between the Mn(III) and M(III) ions across the cyanido bridge were found: J(MnM) = -5.6 (1), -0.63 (2) and -2.4 cm(-1) (3) the Hamiltonian being defined as H = -JS(Mn)·S(M). Theoretical calculations based on density functional theory (DFT) have been used to substantiate both the nature and magnitude of the exchange interactions observed and also to analyze the dependence of the magnetic coupling on the structural parameters within the Mn(III)-N-C-M(III) motif in 1-3. PMID:21442115

Nastase, Silviu; Maxim, Catalin; Andruh, Marius; Cano, Joan; Ruiz-Pérez, Catalina; Faus, Juan; Lloret, Francesc; Julve, Miguel

2011-05-14

112

Stability Properties of Magnetic Tower Jets  

E-print Network

Stability properties of ``magnetic tower'' jets propagating in the gravitationally stratified background have been examined by performing three-dimensional magnetohydrodynamic simulations. The current-carrying, Poynting flux-dominated magnetic tower jet, which possesses a highly wound helical magnetic field, is subject to the current-driven instability (CDI). We find that, under general physical conditions including small perturbations in the initial background profiles, the propagating magnetic tower jets develop the non-axisymmetric, $m=1$ kink mode of the CDI. The kink mode grows on the local Alfv\\'en crossing time scale. In addition, two types of kink modes appear in the system. At the central region where external thermal pressure confinement is strong, only the internal kink mode is excited and will grow. A large distance away from the central region where the external thermal pressure becomes low, the external kink mode is observed. As a result, the exterior of magnetic tower jets will be deformed into a large-scale wiggled structure. We also discuss extensively the different physical processes that contribute to the overall stability properties of the magnetic tower jets. Specifically, when the jet propagates in an initially unperturbed background, we find that they can survive the kink mode beyond the point predicted by the well-known Kruskal-Shafranov (K-S) criterion. The stabilization in this case comes mainly from the dynamical relaxation of magnetic twists during the propagation of magnetic towers; the magnetic pitch is reduced and the corresponding K-S critical wavelength becomes longer as the tower jet proceeds. Furthermore, we show that the pressure-driven and Kelvin-Helmholtz instabilities do not occur in the magnetic tower jets.

Masanori Nakamura; Hui Li; Shengtai Li

2006-08-31

113

Classification of Complex Networks Based on Topological Properties  

E-print Network

Classification of Complex Networks Based on Topological Properties Burcu Kantarci and Vincent Labatut Computer Science Department Galatasaray University Istanbul, Turkey Abstract--Complex networks. Keywords--Complex Networks; Topological Measures, Properties Comparison, Cluster Analysis. I. INTRODUCTION

Paris-Sud XI, Université de

114

Emergent properties of magnetic materials  

Microsoft Academic Search

In Tolstoy's War and Peace, history is presented as a tapestry spun from the daily interactions of large numbers of individuals. Even if one understands individuals, it is very difficult to predict history. Similarly, the interactions of large numbers of electrons give rise to properties that one would not initially guess from their microscopic interactions. During the course of my

William Davis Ratcliff II

2003-01-01

115

Diluted magnetic semiconductors: Actual structure and magnetic and transport properties  

Microsoft Academic Search

An experimental investigation is conducted into electrical-transport, magnetic, optical, and structural properties of GaAs-based\\u000a diluted-magnetic-semiconductor heterostructures containing a Ga1?x\\u000a In\\u000a x\\u000a As quantum well and a Mn delta layer 0.5–1.8 ML thick, separated by a GaAs spacer of thickness 3 nm. Ferromagnetic features\\u000a are observed in the electrical transport and the Hall effect, which involve the flow of holes across

M. A. Chuev; B. A. Aronzon; E. M. Pashaev; M. V. Koval’chuk; I. A. Subbotin; V. V. Rylkov; V. V. Kvardakov; P. G. Medvedev; B. N. Zvonkov; O. V. Vikhrova

2008-01-01

116

Magnetic properties of pelagic marine carbonates  

NASA Astrophysics Data System (ADS)

Pelagic carbonates are deposited far from the continents, usually at water depths of 3,000-6,000 m, at rates slower than 10 cm/kyr. Pelagic carbonates are globally important and have yielded many outstanding paleomagnetic records both from ocean drilling and analysis of outcrops from tectonically uplifted sedimentary sequences. Recent recognition of the widespread preservation of biogenic magnetite has fundamentally changed our understanding of the magnetic properties of pelagic carbonates. We review evidence concerning the range of magnetic minerals typically preserved in these sediments, the effects of magnetic mineral diagenesis on paleomagnetic and environmental magnetic records carried by pelagic carbonates and what they tell us about the environments concerned. Despite recent advances, much remains to be discovered. We are only at early stages of understanding how biogenic magnetite gives rise to paleomagnetic signals and whether it is responsible for a poorly understood biogeochemical remanent magnetization. Recently developed techniques hold much potential for testing how different species of magnetotactic bacteria, which produce different magnetite morphologies, respond to changing nutrient and oxygenation conditions and whether it will be possible to develop proxies for ancient nutrient conditions from well calibrated modern records of such processes. A tantalizing link between giant magnetofossils and Paleogene hyperthermal events needs to be tested and much more needs to be learned about the relationship between climate and the organisms that biomineralized these giant magnetite particles. Despite being studied for over 70 years, the magnetic properties of pelagic carbonates hold many secrets that await discovery.

Roberts, A. P.; Florindo, F.; Chang, L.; Jovane, L.; Heslop, D.; Larrasoaña, J.

2013-05-01

117

Magnetic properties of Martian surface material  

NASA Technical Reports Server (NTRS)

The hypothesis that the magnetic properties of the Martian surface material are due to the production of a magnetic phase in the clay mineral nontronite by transient shock heating is examined. In the course of the investigation a magnetic material is produced with rather unusual properties. Heating from 900 C to 1000 C, of natural samples of nontronite leads first to the production of what appears to be Si doped maghemite gamma (-Fe2O3). Although apparently metastable, the growth of gamma -Fe2O3 at these temprtures is unexpected, and its relative persistence of several hours at 1000 C is most surprising. Continued annealing of this material for longer periods promote the crystallization of alpha Fe2O3 and cristobalite (high temperature polymorph of SiO2). All available data correlate this new magnetic material with the cristobalite hence our naming it magnetic ferri cristobalite. Formation of this magnetic cristobalite, however, may require topotactic growth from a smectite precursor.

Hargraves, R. B.

1984-01-01

118

A study on the magnetic properties of two-phase particulate magnetic composites  

Microsoft Academic Search

The magnetic properties of two-phase particulate magnetic composites with a hard ferromagnetic component are studied theoretically and experimentally. The magnetic properties considered here are phase-distribution sensitive properties, including remanence, coercivity and the shape of hysteresis loop. These properties depend mainly on the properties of its constituents, volume fractions, phase distribution, packing fraction and orientation distribution for anisotropic particles. With fixed

Keun-Long Wang; Shu-En Hsu; J. Chen

1982-01-01

119

Magnetic properties of dispersed magnetite powders  

Microsoft Academic Search

Measurements have been made of coercive force, susceptibility, isothermal remanence, thermoremanence and thermal and alternating field demagnetization of annealed magnetite powders in nine size ranges from 1·5 ? to 120 ?. The samples were dispersed in plaster to occupy a few per cent by volume of the specimens and thus to simulate the magnetic properties of rocks. The results are

L. G. Parry

1965-01-01

120

Magnetic Properties of Dy in Pb  

SciTech Connect

Superconductivity can be induced at high temperatures in Pb{sub 2}Sr{sub 2}RCu{sub 3}O{sub 8} (R - rare earth) by partially doping Ca{sup 2+} for R{sup 3+}. In order to understand the interplay between magnetism and superconductivity, the magnetic properties of the parent compounds, Pb{sub 2}Sr{sub 2}RCu{sub 3}O{sub 8}, have been studied. The work presented here includes magnetic susceptibility and specific heat measurements on R=Dy and extends the previous studies on R=Ce, Pr, Tb, Ho and Er. Specific heat experiments suggest that the Dy ions order antiferromagnetically with an ordering temperature of 1.3K. The magnetic susceptibility data are in good agreement with the susceptibility calculated using crystal field parameters that are extrapolated from previous modeling of the R=Er and Ho analogs of this series.

Skanthakumar, S.; Soderholm, L.; Movshovich, R.

1999-07-10

121

Magnetic dipole discharges. I. Basic properties  

SciTech Connect

A simple discharge is described which uses a permanent magnet as a cold cathode and the metallic chamber wall as an anode. The magnet's equator is biased strongly negative, which produces secondary electrons due to the impact of energetic ions. The emitted electrons are highly confined by the strong dipolar magnetic field and the negative potential in the equatorial plane of the magnet. The emitted electrons ionize near the sheath and produce further electrons, which drift across field lines to the anode while the nearly unmagnetized ions are accelerated back to the magnet. A steady state discharge is maintained at neutral pressures above 10{sup ?3} mbar. This is the principle of magnetron discharges, which commonly use cylindrical and planar cathodes rather than magnetic dipoles as cathodes. The discharge properties have been investigated in steady state and pulsed mode. Different magnets and geometries have been employed. The role of a background plasma has been investigated. Various types of instabilities have been observed such as sheath oscillations, current-driven turbulence, relaxation instabilities due to ionization, and high frequency oscillations created by sputtering impulses, which are described in more detail in companion papers. The discharge has also been operated in reactive gases and shown to be useful for sputtering applications.

Stenzel, R. L.; Urrutia, J. M. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)] [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States); Teodorescu-Soare, C. T.; Ionita, C.; Schrittwieser, R. [Institute for Ion Physics and Applied Physics, University of Innsbruck, A-6020 Innsbruck (Austria)] [Institute for Ion Physics and Applied Physics, University of Innsbruck, A-6020 Innsbruck (Austria)

2013-08-15

122

Complexity and Diffusion of Magnetic Flux Surfaces in Anisotropic Turbulence  

NASA Astrophysics Data System (ADS)

The complexity of magnetic flux surfaces is investigated analytically and numerically in static homogeneous magnetic turbulence. Magnetic surfaces are computed to large distances in magnetic fields derived from a reduced magnetohydrodynamic model. The question addressed is whether one can define magnetic surfaces over large distances when turbulence is present. Using a flux surface spectral analysis, we show that magnetic surfaces become complex at small scales, experiencing an exponential thinning that is quantified here. The computation of a flux surface is of either exponential or nondeterministic polynomial complexity, which has the conceptual implication that global identification of magnetic flux surfaces and flux exchange, e.g., in magnetic reconnection, can be intractable in three dimensions. The coarse-grained large-scale magnetic flux experiences diffusive behavior. The link between the diffusion of the coarse-grained flux and field-line random walk is established explicitly through multiple scale analysis. The Kubo number controls both large and small scale limits. These results have consequences for interpreting processes such as magnetic reconnection and field-line diffusion in astrophysical plasmas.

Servidio, S.; Matthaeus, W. H.; Wan, M.; Ruffolo, D.; Rappazzo, A. F.; Oughton, S.

2014-04-01

123

Magnetic properties of heterotrophic bacteria (abstract)  

NASA Astrophysics Data System (ADS)

The magnetic properties (magnetic susceptibility and saturation magnetization) of six species of heterotrophic bacteria were studied: alcaligenes faecalis 81, arthrobacter globiformis BKM 685, bacillus cereus 8, leptothrix pseudo-ochracea D-405, proteus vulgaris 14, and seliberia stellata. It has been shown that the magnetic properties of bacteria depend on (1) the peculiarity of the micro-organism (species-specific and connected with cultivation conditions); (2) the source of the iron in the media. Most of the bacteria are diamagnetic in media with a minimum of iron (??=-7.2-0.3×10-6 sm3/g). The spore forming species (bacillus cereus) has increased diamagnetism. Usually the bacteria are paramagnetic in iron-containing media because they concentrate into Fe compounds. The paramagnetism of the iron-concentrating species (anthrobacter globiformis -?par=2.4×10-6, leptothrix pseudo-ochtracea ?par=11.0×10-6 and seliberia stellata ?par=3.2×10-6 sm3/g) depends, in general, on magnetically ordered compounds. Iron compounds not accumulated by proteus vulgaris and these species are always diamagnetic .

Verkhovceva, Nadezda V.; Glebova, Irina N.; Romanuk, Anatoly V.

1994-05-01

124

Magnetic properties of pelagic marine carbonates  

NASA Astrophysics Data System (ADS)

Pelagic carbonates are deposited far from continents, usually at water depths of 3000-6000 m, at rates below 10 cm/kyr, and are a globally important sediment type. Recent advances, with recognition of widespread preservation of biogenic magnetite (the inorganic remains of magnetotactic bacteria), have fundamentally changed our understanding of the magnetic properties of pelagic carbonates. We review evidence for the magnetic minerals typically preserved in pelagic carbonates, the effects of magnetic mineral diagenesis on paleomagnetic and environmental magnetic records of pelagic carbonates, and what magnetic properties can tell us about the open-ocean environments in which pelagic carbonates are deposited. We also discuss briefly late diagenetic remagnetisations recorded by some carbonates. Despite recent advances in our knowledge of these phenomena, much remains undiscovered. We are only at early stages of understanding how biogenic magnetite gives rise to paleomagnetic signals in sediments and whether it carries a poorly understood biogeochemical remanent magnetisation. Recently developed techniques have potential for testing how different magnetotactic bacterial species, which produce different magnetite morphologies, respond to changing nutrient and oxygenation conditions. Future work needs to test whether it is possible to develop proxies for ancient nutrient conditions from well-calibrated modern magnetotactic bacterial occurrences. A tantalizing link between giant magnetofossils and Paleogene hyperthermal events needs to be tested; much remains to be learned about the relationship between climate and the organisms that biomineralised these large and novel magnetite morphologies. Rather than being a well-worn subject that has been studied for over 60 years, the magnetic properties of pelagic carbonates hold many secrets that await discovery.

Roberts, Andrew P.; Florindo, Fabio; Chang, Liao; Heslop, David; Jovane, Luigi; Larrasoaña, Juan C.

2013-12-01

125

Correcting Aberrations in Complex Magnet Systems for Muon Cooling Channels  

SciTech Connect

Designing and simulating complex magnet systems needed for cooling channels in both neutrino factories and muon colliders requires innovative techniques to correct for both chromatic and spherical aberrations. Optimizing complex systems, such as helical magnets for example, is also difficult but essential. By using COSY INFINITY, a differential algebra based code, the transfer and aberration maps can be examined to discover what critical terms have the greatest influence on these aberrations.

J.A. Maloney, B. Erdelyi, A. Afanaciev, R.P. Johnson, Y.S. Derbenev, V.S. Morozov

2011-03-01

126

Measuring Viscosity with a Levitating Magnet: Application to Complex Fluids  

ERIC Educational Resources Information Center

As an experimental project proposed to students in fourth year of university, a viscometer was developed, consisting of a small magnet levitating in a viscous fluid. The viscous force acting on the magnet is directly measured: viscosities in the range 10-10[superscript 6] mPa s are obtained. This experiment is used as an introduction to complex

Even, C.; Bouquet, F.; Remond, J.; Deloche, B.

2009-01-01

127

PHYSICAL PROPERTIES OF COMPLEX C HALO CLOUDS  

SciTech Connect

Observations from the Galactic Arecibo L-band Feed Array H I (GALFA-H I) Survey of the tail of Complex C are presented and the halo clouds associated with this complex are cataloged. The properties of the Complex C clouds are compared to clouds cataloged at the tail of the Magellanic Stream to provide insight into the origin and destruction mechanism of Complex C. Magellanic Stream and Complex C clouds show similarities in their mass distributions (slope = -0.7 and -0.6 log (N( log (mass)))/ log (mass), respectively) and have a common line width of 20-30 km s{sup -1} (indicative of a warm component), which may indicate a common origin and/or physical process breaking down the clouds. The clouds cataloged at the tail of Complex C extend over a mass range of 10{sup 1.1}-10{sup 4.8} M{sub sun}, sizes of 10{sup 1.2}-10{sup 2.6} pc, and have a median volume density and pressure of 0.065 cm{sup -3} and (P/k) = 580 K cm{sup -3}. We do not see a prominent two-phase structure in Complex C, possibly due to its low metallicity and inefficient cooling compared to other halo clouds. Assuming that the Complex C clouds are in pressure equilibrium with a hot halo medium, we find a median halo density of 5.8 x 10{sup -4} cm{sup -3}, which given a constant distance of 10 kpc is at a z-height of {approx}3 kpc. Using the same argument for the Stream results in a median halo density of 8.4 x 10-{sup 5} (60 kpc/d) cm{sup -3}. These densities are consistent with previous observational constraints and cosmological simulations. We also assess the derived cloud and halo properties with three-dimensional grid simulations of halo H I clouds and find that the temperature is generally consistent within a factor of 1.5 and the volume densities, pressures, and halo densities are consistent within a factor of three.

Hsu, W.-H. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Putman, M. E.; Peek, J. E. G. [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Heitsch, F.; Clark, S. E. [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 (United States); Stanimirovic, S., E-mail: wenhsin@umich.edu [Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706-1582 (United States)

2011-02-15

128

Tuning electronic and magnetic properties of silicene with magnetic superhalogens.  

PubMed

Due to its compatibility with the well-developed Si-based semiconductor industry, silicene has attracted considerable attention. Using density functional theory we show for the first time that the recently synthesized superhalogen MnCl3 can be used to tune the electronic and magnetic properties of silicene, from semi-metallic to semiconducting with a wide range of band gaps, as well as from nonmagnetic to ferromagnetic (or antiferromagnetic) by changing the coverage of the superhalogen molecules. The electronic properties can be further modulated when a superhalogen and a halogen are used synergistically. The present study indicates that because of the large electron affinity and rich structural diversity superhalogen molecules have advantages over the conventional halogen atoms in modulating the material properties of silicene. PMID:25144623

Zhao, Tianshan; Zhang, Shunhong; Wang, Qian; Kawazoe, Yoshiyuki; Jena, Puru

2014-10-01

129

Remanent magnetic properties of unbrecciated eucrites  

NASA Technical Reports Server (NTRS)

This study examines the remanent magnetic properties of five unbrecciated eucrites, ranging from the coarse-grained cumulate Moore County to the quenched melt rock ALH 81001 in order to assess the strength of the magnetic field associated with their parent body during their formation. Two of the meteorites are judged as unlikely to have preserved their primary thermal remanence because of large variations in subsample remanence intensity and direction (Ibitira), and lack of NRM resistance to AF and thermal demagnetization (PCA 82502). The lack of a strong (greater than 0.01 mT) magnetizing field during their cooling on the eucrite parent body is inferred from the low normalized NRM intensities for subsamples of ALH 81001 and Yamato 791195.

Cisowski, Stanley M.

1991-01-01

130

Sintered soft magnetic materials. Properties and applications  

NASA Astrophysics Data System (ADS)

A comparison is presented of the characteristics and production requirements of a variety of materials used to produce sintered soft magnetic parts. These include pure iron, phosphorous-iron, silicon-iron, nickel-iron, and cobalt-iron, together with new coated materials based on encapsulated iron powders. In these bonded materials an organic and/or inorganic insulator is used to coat the metallic powder particles giving a magnetic composite. The suitability of the different materials for use in both direct and alternating current applications is reviewed, and examples are provided of their application in both the automotive and other sectors. The results of a comparative study of motors using stators and rotors based on both conventional laminated materials and the insulated iron powders are presented, in which the new materials show advantages of reduced hysteresis losses at high frequencies, and isotropy of magnetic properties. Nevertheless, the applications of these materials in electrical motors requires the modification of existing designs.

Bas, J. A.; Calero, J. A.; Dougan, M. J.

2003-01-01

131

Magnetic properties of cyclically deformed austenite  

NASA Astrophysics Data System (ADS)

In meta-stable austenitic stainless steels, low cycle fatigue deformation is accompanied by a partial stress/strain-induced solid state phase transformation of paramagnetic ?(fcc) austenite phase to ferromagnetic ?/(bcc) martensite. The measured characteristic of magnetic properties, which are the saturation magnetization, susceptibility, coercivity, retentivity, and the area under the magnetic hysteresis loop are sensitive to the total strain amplitude imposed and the corresponding material behaviour. The morphologies and nucleation characteristics of deformation induced martensites (i.e., ?(hcp), ?/(bcc)) have been investigated through analytical transmission electron microscope. It has been observed that deformation induced martensites can nucleate at a number of sites (i.e., shear band intersections, isolated shear bands, shear band-grain boundary intersection, grain boundary triple points, etc.) through multiple transformation sequences: ?(fcc)??(hcp), ?(fcc)??(hcp)??/(bcc), ?(fcc)? deformation twin ??/(bcc) and ?(fcc)??/(bcc).

Das, Arpan

2014-06-01

132

Magnetic properties of fine SFMO particles: Superparamagnetism  

NASA Astrophysics Data System (ADS)

Magnetic properties of fine Sr2FeMoO6 (SFMO) powders were systematically studied and superparamagnetism was observed. The SFMO samples were prepared using a citrate-gel method and were characterized by X-ray diffraction (XRD), ferromagnetic resonance (FMR) and Mössbauer spectroscopy. The XRD measurements showed that the powders are nearly pure and the Rietveld refinement gave particle sizes of 31 and 197 nm and antisite disorders of 10 and 15%, respectively. The 197 nm crystallite size sample has a TC=415 K and a magnetic moment of 3.0 ?B/f.u. Several measurements made by SQUID magnetometer, FMR and Mössbauer spectroscopy showed that the 31 nm crystallite sample behaves superparamagnetically with blocking temperature TB=35 K and it has a reduced saturation magnetization of 1.0 ?B/f.u. at 5 K and effective paramagnetic moment of 3.0 ?B.

Suominen, T.; Raittila, J.; Salminen, T.; Schlesier, K.; Lindén, J.; Paturi, P.

2007-02-01

133

Properties of Magnetic Reconnection as a function of magnetic shear  

NASA Astrophysics Data System (ADS)

Observations of reconnection events at the Earth's magnetopause and in the solar wind show that reconnection occurs for a large range in magnetic shear angles extending to the very low shear limit 1. Here we report a fully kinetic study of the influence of the magnetic shear on details of reconnection such as its structure and rate. In previous work, we found that the electron diffusion region bifurcates into two or more distinct layers in regimes with weak magnetic shear2, a new feature that may be observable by NASA's up-coming Magnetospheric Multiscale mission. In this work, we have systematically extended the study to lower shear cases and found a new regime, where the reconnection electric field becomes much smaller and the properties of the reconnection changes significantly. We will discuss the role of various physics mechanisms in determining the observed scaling of the reconnection rate, including the dispersive properties of the waves in the system, the dissipation mechanisms and the tearing instability. 1 J. T. Goslings and T. D. Phan. APJL 763, L39, 2013 2 Yi-Hsin Liu et al. Phys. Rev. Lett. 110 , 265004, 2013

Liu, Y.; Daughton, W. S.; Karimabadi, H.; Li, H.; Gary, S. P.; Guo, F.

2013-12-01

134

Effects of magnetic atoms on the properties of ternary superconductors  

SciTech Connect

Until recently it has been commonly accepted that small impurities of magnetic atoms were severely detrimental to superconductivity, and that superconductivity and long-range magnetic ordering could not occur in the same materials. In known binary and pseudo-binary compounds, this is still the case. However, many recent experiments on ternary superconductors have shown that the effects of magnetism are considerably more complex. In some cases, the addition of magnetic atoms has been found to enhance superconducting properties by increasing the superconducting critical field, without significantly lowering the transition temperature. In many cases, compounds will show both superconducting and long range magnetic ordering transitions. The destruction of superconductivity by ferromagnetic ordering and the coexistence of superconductivity with antiferromagnetic ordering is now well established. Hyperfine interaction measurements have played a significant role in the investigations of these materials, including measurement of the magnitude of the exchange interaction between rare-earth spin and conduction electron spin, elucidation of the mechanism for critical field enhancement, specification of crystalline field ground states, and studies of the nature of magnetic ordering.

Dunlap, B.D.; Shenoy, G.K.

1980-01-01

135

Topological complexity and tangential discontinuity in magnetic fields  

SciTech Connect

This is a study of the topological magnetostatic problem. A magnetic field embedded in a perfectly conducting fluid and rigidly anchored at its boundary has a specific topology invariant for all time. Subject to that topology, the force-free state of such a field generally requires the presence of tangential discontinuities (TDs). This property proposed and demonstrated by Parker [Spontaneous Current Sheets in Magnetic Fields (Oxford University Press, New York, 1994)] is explained in terms of (i) the overdetermined nature of the magnetostatic partial differential equations nonlinearly coupled to the integral equations imposing the field topology and (ii) the hyperbolic nature of the partial differential equation for the twist function {alpha} of the force-free field. The mathematical analysis elucidates a basic incompatibility between preserving a complex field topology and attaining equilibrium, if analyticity is assumed. Physics avoids this incompatibility via TD formation as a natural consequence of perfect conductivity. The study relates TD formation to topological complexity in two-dimensional and three-dimensional fields, as well as the topological connectivity and geometric shape of the field domain. Mathematical points made are given physical interpretations, but important topological concepts for understanding spontaneous TDs have remained incomplete. As an application, examples are presented to define twisted and untwisted potential fields found in simply and multiply connected domains, clarifying a confusion in several recent publications. Appendix A treats the expression of the frozen-in condition by a continuum of conserved, total generalized helicities. Appendix B reports briefly on concurrent developments showing that a published objection to the theory of spontaneous TDs is based upon a misunderstanding of the theory.

Janse, A. M. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, 0315 Oslo (Norway) and Advanced Study Program, National Center for Atmospheric Research, P.O. Box 3000, 3090 Center Green, Boulder, Colorado 80301 (United States); Low, B. C. [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, 3080 Center Green, Boulder, Colorado 80301 (United States); Parker, E. N. [Department of Physics, University of Chicago, 5720 South Ellis Avenue, Chicago, Illinois 60637 (United States)

2010-09-15

136

The emergence of complex behaviours in molecular magnetic materials.  

PubMed

Molecular magnetism is considered an area where magnetic phenomena that are usually difficult to demonstrate can emerge with particular clarity. Over the years, however, less understandable systems have appeared in the literature of molecular magnetic materials, in some cases showing features that hint at the spontaneous emergence of global structures out of local interactions. This ingredient is typical of a wider class of problems, called complex behaviours, where the theory of complexity is currently being developed. In this perspective we wish to focus our attention on these systems and the underlying problematic that they highlight. We particularly highlight the emergence of the signatures of complexity in several molecular magnetic systems, which may provide unexplored opportunities for physical and chemical investigations. PMID:25072189

Goss, Karin; Gatteschi, Dante; Bogani, Lapo

2014-09-14

137

??Complexation Studied by Fluorescence Technique: Application in Desulfurization of Petroleum Product using Magnetic ??Complexation Sorbents  

Microsoft Academic Search

Magnetic ??complexation sorbents were studied for petroleum product desulfurization by fluorescent technique. The ability of metal cation to form ??complexation decreases in the order following: Cu>Ni>Co>Al. The order is consistent with that of desulfurization performance of their corresponding magnetic sorbents (??Al2O3?Cu(I)>??Al2O3?Ni(II)>??Al2O3?Co(II)>??Al2O3). Both ??complexation strength and desulfurization performance of the sorbents increase with temperature. The adsorptive performances of magnetic ??Al2O3?Cu(I) sorbent

Guobin Shan; Huaiying Zhang; Huizhou Liu; Jianmin Xing

2005-01-01

138

Aluminium complexes in methanol–water mixture as studied by 27Al NMR nuclear magnetic resonance  

Microsoft Academic Search

27Al NMR spectroscopy can be used for study of coordination and solvation in both aqueous and non-aqueous solutions. Various octahedral and tetrahedral aluminium complexes have been proved to exist in solution by 1H and 27Al NMR spectroscopy. 27Al nuclear magnetic resonance (NMR) spectroscopy also can be used to determine thermodynamic properties of complexes in the solution. The formation of [Al(OH)4?n(CH3OH)n](n?1)+

Abdolraouf Samadi-Maybodi

2006-01-01

139

Magnetic Properties of Pt-Co Alloys  

NASA Astrophysics Data System (ADS)

Pt-Co alloys have been investigated by diverse methods to study their magnetic and chemical properties. Magnetization measurements gave originally a value of 2.0 Bohr magnetons for the Co moment, but large magnetically polarized zones were also measured with a size of 3.4 Bohr magnetons, this indicated that part of the magnetization was dispersed among Pt atoms, with a small moment in each atom and, therefore, these polarization zones covered several angstroms producing “giant moments” due to the size of its range. Later, diffuse neutron scattering measurements on Pt-Co alloys gave a value of 2.08 Bohr magnetons for the Co moment and 3.26 Bohr magnetons for the magnetization clouds. However, the diffuse scattering measurements have other components their cross sections, besides the polarization clouds and the Co average moment. There are, for example, non-elastic contributions, elastic dispersion due to thermal fluctuations and, for concentrations with a Curie temperature near the experimental one, critical scattering is observed, formed by localized regions that start polarizing before the transition to ferromagnetism happens. The calculations of the correlation were made by Monte Carlo simulation methods and the critical scattering was analyzed using the Ornstein-Zernicke formalism, obtaining the average range of the polarization of these localized zones. From the nuclear diffuse neutron scattering, the atomic short-range order parameters were also obtained.

Parra, Rixio; Gonzalez, Aleida

1999-11-01

140

Magnetic properties and microstructure of bulk Nd-Fe-B magnets solidified in magnetic field  

NASA Astrophysics Data System (ADS)

The Nd-Fe-B bulk magnets with a slab shape of 0.9 × 4 × 15 mm3 were prepared by injection casting into a copper mold. The effects of applying a magnetic field during the casting process on the magnetic properties and microstructure of Nd9.5Fe71.5Ti2.5Zr0.5Cr1B14.5C0.5 alloy have been studied. The results show that the sample cast with magnetic field has a stronger (00L) texture of Nd2Fe14B phase with the c-axis perpendicular to the slab plane than the sample cast without magnetic field. The intensity of the texture weakens from surface to inner region of the bulk magnets. Applying a magnetic field during the casting process is helpful to refine the grain size effectively. As a result, the magnetic properties are improved from Br = 5.8 kG, iHc = 6.5 kOe, and (BH)max = 5.9 MGOe for thesample cast without magnetic field to Br = 6.1 kG, iHc = 10.3 kOe, and (BH)max = 7.3 MGOe for the sample cast with a 3.7 kOe magnetic field.

Wang, C.; Lai, Y. S.; Hsieh, C. C.; Chang, W. C.; Chang, H. W.; Sun, A. C.

2011-04-01

141

Flares and Their Underlying Magnetic Complexity  

NASA Astrophysics Data System (ADS)

SphinX (Solar PHotometer IN X-rays), a full-disk-integrated spectrometer, observed 137 flare-like/transient events with active region (AR) 11024 being the only AR on disk. The Hinode X-Ray Telescope (XRT) and Solar Optical Telescope observe 67 of these events and identified their location from 12:00 UT on July 3 through 24:00 UT 2009 July 7. We find that the predominant mechanisms for flares observed by XRT are (1) flux cancellation and (2) the shearing of underlying magnetic elements. Point- and cusp-like flare morphologies seen by XRT all occur in a magnetic environment where one polarity is impeded by the opposite polarity and vice versa, forcing the flux cancellation process. The shearing is either caused by flux emergence at the center of the AR and separation of polarities along a neutral line or by individual magnetic elements having a rotational motion. Both mechanisms are observed to contribute to single- and multiple-loop flares. We observe that most loop flares occur along a large portion of a polarity inversion line. Point- and cusp-like flares become more infrequent as the AR becomes organized with separation of the positive and negative polarities. SphinX, which allows us to identify when these flares occur, provides us with a statistically significant temperature and emission scaling law for A and B class flares: EM = 6.1 × 1033 T 1.9±0.1.

Engell, Alexander J.; Siarkowski, Marek; Gryciuk, Magda; Sylwester, Janusz; Sylwester, Barbara; Golub, Leon; Korreck, Kelly; Cirtain, Jonathan

2011-01-01

142

Modeling the magnetic properties and Mössbauer spectra of multifunctional magnetic materials obtained by insertion of a spin-crossover Fe(III) complex into bimetallic oxalate-based ferromagnets.  

PubMed

In this article, we present a theoretical microscopic approach to describe the magnetic and spectroscopic behavior of multifunctional hybrid materials which demonstrate spin crossover and ferromagnetic ordering. The low-spin to high-spin transition is considered as a cooperative phenomenon that is driven by the interaction of the electronic shells of the Fe ions with the full symmetric deformation of the local surrounding that is extended over the crystal lattice via the acoustic phonon field. The proposed model is applied to the analysis of the series [Fe(III)(sal2-trien)] [Mn(II)Cr(III)(ox)3]·solv, in short 1·solv, where solv = CH2Cl2, CH2Br2, and CHBr3. PMID:24224547

Ostrovsky, S M; Reu, O S; Palii, A V; Clemente-León, M; Coronado, E; Waerenborgh, J C; Klokishner, S I

2013-12-01

143

Magnetic properties of Mg-ferrite nanoparticles  

NASA Astrophysics Data System (ADS)

MgFe 2O 4 nanoparticles encapsulated in amorphous SiO 2 were prepared by means of a wet chemical method, and the magnetic properties were studied. The diameters of these particles were estimated from X-ray diffraction patterns as ranging from 3 to 8 nm. Magnetization measurements were carried out for each sample under a ±50 kOe field. The blocking temperature, Tb, was determined to be around 30 K from the temperature dependence of both the field-cooled (FC) and the zero-field-cooled (ZFC) magnetization. The M- H curve indicated the presence of ferromagnetic behavior with hysteresis below the blocking temperature, Tb. A large coercive force of about 1000 Oe was found at 5 K. Heat treatment was carried out for the prepared samples using an electric furnace in air. A clear difference in magnetization was found between the quenched samples and annealed samples. This phenomenon suggests that the Mg 2+ ions in the spinel structure would be randomly distributed into both the A- and the B-site.

Ichiyanagi, Y.; Kubota, M.; Moritake, S.; Kanazawa, Y.; Yamada, T.; Uehashi, T.

2007-03-01

144

Structural and magnetic properties in bidimensional manganites  

NASA Astrophysics Data System (ADS)

The Lny-xCa2-xMnO4 series, with a K2NiF4 structure, has been studied by neutron powder diffraction and electron microscopy in connection with the magnetic and transport properties. We report here the results of the structural and magnetic study of two compounds, Pr0.25Ca1.75MnO4 and Ho0.08Ca1.92MnO4, for which the Mn valency is 3.75 and 3.92 respectively and consequently that show different magnetic and transport behaviours. At room temperature (RT), the average structure of both compounds is orthorhombic with lattice parameters ap? , 12Å, ap? , and Cmca space group. With decreasing temperature, the Ho0.08Ca1.92MnO4 compound exhibits two magnetic phase transitions: antiferromagnetism appears at TN 165K and ferromagnetism at TC 75K. The two phases coexist below TC without any structural transition. The Pr0.25Ca1.75MnO4 compound exhibits charge ordering below TCO 275K, characterised by superlattice reflections clearly evidenced by electron diffraction. Neutron diffraction pattern refinements show a partial structural transition from Cmca (RT) to C2/c (low temperature) around the charge-ordering temperature and antiferromagnetism below TN 150K.

Autret, C.; André, G.; Bourée, F.; Martin, C.; Hervieu, M.; Maignan, A.; Retoux, R.; Raveau, B.

145

Complex magnetic fields breathe life into fluids.  

PubMed

The vast majority of materials research exploits equilibrium or quasi-equilibrium processes to produce inert materials. In contrast, living systems depend on far-from-equilibrium kinetic processes that require a continuous flux of energy to persist and perform useful tasks. The Greek god Hephaestus forged metal automatons that he miraculously animated to perform the tasks of living creatures. Is something like this actually possible? Here we show that subjecting magnetic fluids suspended in an immiscible liquid to uniform, multidimensional, time-dependent magnetic fields, generates a variety of life-like collective dynamics, including various forms of locomotion, swarming and feeding, that are sustained by the continuous injection of energy via the applied field. These leaderless emergent behaviors occur autonomously, without human guidance, and are quite surprising. Such self-healing, remotely-powered fluid automatons could be used as an extraction/separation technology to efficiently purify water by scavenging toxic chemicals and microorganisms, or alternatively enable the controlled release of chemicals. Other possible applications include vigorous fluid mixing and even microdroplet manipulation for microfluidic bioassays. PMID:25318082

Solis, Kyle J; Martin, James E

2014-10-30

146

Magnetic properties of periodically organized cobalt frameworks  

NASA Astrophysics Data System (ADS)

Periodically organized magnetic cobalt frameworks have been fabricated by a combination of colloidal self-assembly and electrochemical deposition. The ordered cobalt frameworks have a closed-packed face-centered-cubic inverse opal structure and are fabricated as micrometer-thick films. The size and density of the cobalt crystallites that compose the cobalt frameworks can be modified by a thermal annealing step following the electrodeposition. Comparison of the magnetic properties (studied by magneto-optical Kerr effect (MOKE) spectroscopy) of as-deposited and annealed samples reveals strong impact of the annealing process. Fitting the obtained MOKE response to a modified Langevin model reveals optimum values of coercivity, pinning site density, and inter-domain coupling for samples that are thermally annealed at 440 °C.

Hukic-Markosian, Golda; Zhai, Yaxin; Montanari, Danielle E.; Ott, Steven; Braun, Adrianne; Sun, Dali; Vardeny, Zeev V.; Bartl, Michael H.

2014-07-01

147

Magnetic properties of Gd3+ ions in the spatially distributed DNA molecules  

NASA Astrophysics Data System (ADS)

Magnetic properties of DNA liquid-crystal dispersions are experimentally investigated by SQUID magnetometer. The magnetic susceptibility of pure DNA and DNA doped by La, and Gd is measured in the region 4.2-300 K. The total magnetic moment is represented as a sum of the paramagnetic part and negative diamagnetic part. The number of paramagnetic Gd3+ ions is calculated in a good agreement with the number of phosphate complexes. The temperature dependence of magnetic susceptibility indicates the presence of interaction between Gd3+ magnetic moments, which is discussed in terms of long-range RKKY-type exchange in one-dimensional metals.

Nikiforov, V. N.; Kuznetsov, V. D.; Yevdokimov, Yu. M.; Irkhin, V. Yu.

2014-11-01

148

Energetic and Magnetic Properties of Palladium Clusters  

NASA Astrophysics Data System (ADS)

The structural, energetic and magnetic properties of palladium clusters from 2 to 55 atoms were calculated using Density Functional method with plane wave basis set. The results show that the binding energies increase rapidly from 0.595 eV to 1.60 eV within 4 atoms, then gradually to 2.79 eV with 55 atoms. The calculated bulk cohesive energy is 3.68 eV. For a given number of atoms, the binding energies of small palladium clusters are strongly dependent on their configurations. The three-dimensional packing with the highest density has the largest energy, while the linear arrangement has the smallest one. Although the binding energies of both linear and planar arrangements are small, these structures are stable in the absence of external fields. The binding energies of linear and planar arrangements increase slowly with increasing of the number of atoms, from 0.595 to 1.0 eV for linear and 1.18 to 1.8 eV for planar configurations, respectively. Tetrahedron for Pd_4, triangular bipyramid for Pd_5, octahedron for Pd6 and icosahedron for Pd_13 are found to be the most stable cluster structures. The fact that some other three-dimensional Pd5 and Pd6 clusters tend to transform to triangular bipyramid and octahedron was discovered and discussed. We also found that the square conformation is rather stable and some new packing styles containing square skeletons which differ from that of the bulk are examined. The magnetic property of these clusters was calculated and discussed. Some non-magnetic and high magnetic stacking patterns are predicted. an attachment.

Zhang, Wenqin; Ge, Qingfeng; Wang, Lichang

2002-03-01

149

Modeling graphene: Magnetic, transport and optical properties  

NASA Astrophysics Data System (ADS)

Graphene, with its unique linear dispersion near the Fermi energy, has attracted great attention since its successful isolation from highly oriented pyrolytic graphite in 2004. Many important properties have been identified in graphene, including a remarkably high mobility at room temperature, an unusual quantum hall effect, and an ambipolar electric field effect. It has been proposed as a candidate for many applications, such as optical modulators, spintronic devices, and solar cells. Understanding the fundamental properties of graphene is therefore important. In this dissertation, I present a study of transport, magnetism and optical properties of graphene. In the first chapter, I introduce the electronic properties of mono layer and few layer graphene. In the second chapter, I present low temperature transport measurements in few layer graphene. An electric-field induced semimetal-to-metal transition is observed based on the temperature dependence of the resistance for different applied gate voltages. At small gate voltages the resistance decreases with increasing temperature due to the increase in carrier concentration resulting from thermal excitation of electron-hole pairs, as it is characteristic of a semimetal. At large gate, voltages excitations of electron-hole pairs are suppressed, and the resistance increases with increasing temperature because of the decrease in mean free path due to electron-phonon scattering, as is characteristic of a metal. The electron and hole mobilities are almost equal, so there is approximate electron-hole symmetry. The data are analyzed according to two different theoretical models for few-layer graphene. A simple two band (STB) model, two overlapping bands with quadratic energy-versus-momentum dispersion relations, is used to explain the experimental observations. The best fitting parameter for the overlap energy is found to be 16 meV. However, at low temperatures, the STB suggests that the conductivity is gate independent in the small gate voltage regime, which is not observed in the data. By considering frustration of the electronic potential due to impurities from the substrate, a Gaussian-distribution puddle model can successfully describe the observed transport behavior in the low temperature, small gate voltage regime. In the third chapter, I investigate the effects of point and line defects in monolayer graphene within the framework of the Hubbard model, using a self-consistent mean field theory. These defects are found to induce characteristic patterns into the electronic density of states and cause non-uniform distributions of magnetic moments in the vicinity of the impurity sites. Specifically, defect induced resonances in the local density of states are observed at energies close to the Dirac points. The magnitudes of the frequencies of these resonance states are shown to decrease with the strength of the scattering potential, whereas their amplitudes decay algebraically with increasing distance from the defect. For the case of defect clusters, we observe that with increasing defect cluster size the local magnetic moments in the vicinity of the cluster center are strongly enhanced. Furthermore, non-trivial impurity induced magnetic patterns are observed in the presence of line defects: zigzag line defects are found to introduce stronger-amplitude magnetic patterns than armchair line defects. When the scattering strength of these topological defects is increased, the induced patterns of magnetic moments become more strongly localized. In the fourth chapter, I theoretically study the electronic properties properties in graphene dots under mechanical deformation, using both tight binding lattice model and effective Dirac model. We observed an edge state, which is tunned by an effective quantum well originating from a strain-induced gauge field. Applying a uniaxial strain along the zigzag or armchair directions enhances or dampens the edge state due to the development of edge quantum wells. When an arc bending deformation is applied, the inner and outer edges of graphene dot

Chang, Yi Chen

150

A measurement setup for acquiring the local magnetic properties of plastically deformed soft magnetic materials  

SciTech Connect

This paper introduces a new measurement setup for extraction of the local magnetic properties. With the help of finite element method simulations, modifications are made on the previous double-C-yoke method. Small dimension measuring coils are applied in the stray field produced by the magnetic circuit to evaluate the local magnetic properties of the specified part of the specimen. Through the measurements with the plastically deformed materials at different temperatures, it indicates that the magnetic properties of soft magnetic materials are quite sensitive to plastic straining. After high-temperature thermal treatment on the plastically deformed specimen, the local magnetic properties exhibit an obvious recovery.

Bi Shasha [Chair of Sensor Technology, University Erlangen-Nuremberg, 91052 Erlangen (Germany); Department of Control Science and Engineering, Tongji University, Shanghai (China); Sutor, Alexander; Lerch, Reinhard [Chair of Sensor Technology, University Erlangen-Nuremberg, 91052 Erlangen (Germany); Xiao Yunshi [Department of Control Science and Engineering, Tongji University, Shanghai (China)

2011-04-01

151

Magnetic properties of some rare-earth nanostuctured aluminates  

NASA Astrophysics Data System (ADS)

Nanocrystalline single-phase RAlO3 (R = Nd, Sm, Eu, Dy, Gd) has been prepared by modified Pechini's method. Malic acid has been used for the first time as a new complexing agent in the sol-gel process. It has facilited a low temperature synthesis of the compound. The characterization of the nanoparticles has been carried out by different methods. Using Physical Property Measurement System (PPMS-9 QD) the temperature and magnetic dependency of the susceptibility and magnetization of the nanostuctured aluminates were measured. The obtained results were compared with the existing ones for the single crystals and powder specimens of the same aluminates. The differences observed have been discussed in the framework of the molecular field theory for a two-sublattice system.

Lovchinov, V.; Petrov, D.; Simeonova, P.; Angelov, B.

2010-11-01

152

Magnetic properties of Ni2N  

NASA Astrophysics Data System (ADS)

A powder sample of body-centered tetragonal Ni2N in a single phase was prepared by a high rate-type triode dc reactive sputtering and the magnetic properties have been reinvestigated. It is confirmed that Ni2N is not a ferromagnet. However, the material is not a simple paramagnet either and shows a weak spin-glass-like behavior at low temperatures with a freezing temperature of about 8 K. Posible origins of the behavior are discussed. Band-structure calculations are reported to see the stability of the nonmagnetic ground state of bct Ni2N against lattice expansion and appearance of nitrogen vacancies.

Nishihara, H.; Suzuki, K.; Umetsu, R. Y.; Kanomata, T.; Kaneko, T.; Zhou, M. Y.; Tsujikawa, M.; Shirai, M.; Sakon, T.; Wada, T.; Terashima, K.; Imada, S.

2014-09-01

153

Magnetic properties of an AISI 420 martensitic stainless steel  

Microsoft Academic Search

The magnetic properties (coercive force, saturation and residual magnetization, and Curie temperature) of an AISI 420 steel were measured for different heat treatment conditions (quenching and tempering). The results show that the material is magnetically softer in the annealed condition and after oil quenching an increase of coercive force (MHc) and residual induction (Br) and a decrease of saturation magnetization

S. S. M. Tavares; D. Fruchart; S. Miraglia; D. Laborie

2000-01-01

154

Physica B 398 (2007) 430433 Magnetic properties of frustrated Y-doped GdInCu4  

E-print Network

effects may lead to magnetic frustration mechanism in complex materials such as heavy Fermion systems [4-sharing tetrahedral lattice which may lead to geometrical frustration [3]. Combining ESR of Gd3þ and magneticPhysica B 398 (2007) 430­433 Magnetic properties of frustrated Y-doped GdInCu4 J.G.S. Duque, E

Miranda, Eduardo

155

L-tyrosinatonickel(II) complex: synthesis and structural, spectroscopic, magnetic, and biological properties of 2{[Ni(L-Tyr)2(bpy)]}·3H2O·CH3OH.  

PubMed

The complex 2{[Ni(L-Tyr)2(bpy)]}·3H2O·CH3OH [1, where L-Tyr = L-tyrosine; bpy = 2,2'-bipyridine (2,2'-bpy)] was obtained in crystalline form and characterized by X-ray and spectroscopic (FT-IR, NIR-vis-UV, and HFEPR) and magnetic methods. The complex crystallized in the hexagonal system with a = b = 12.8116(18) Å, c = 30.035(6) Å, and space group P3221. The six-coordination sphere around the Ni(2+) ion is formed by two N and two O L-tyrosinato atoms and completed by two N atoms of the 2,2'-bpy molecule. Neighboring [Ni(L-Tyr)2(bpy)] units are joined via weak hydrogen bonds, which create a helical polymeric chain. The coordinated atoms form a strongly distorted cis-NiN2N2'O2 octahedral chromophore. The solid-state electronic spectrum of complex 1 was analyzed assuming D2h symmetry, and the observed bands were assigned to (3)B1g ? (3)Ag, (3)B1g ? (3)B3g, (3)B1g ? (3)B2g, (3)B1g ? (3)B3g, (3)B1g ? (3)B1g, and (3)B1g ? (3)B2g transitions for the I and II d-d bands, respectively. The crystal-field parameters found for D2h symmetry are Dq = 1066 cm(-1), Ds = 617 cm(-1), Dt = -93 cm(-1), B22 = 7000 cm(-1), and Racah B = 812 cm(-1). Magnetic studies revealed the occurrence of hydrogen-bonded metal pairs. The spin Hamiltonian parameters D = -3.262 cm(-1) and E = -0.1094 cm(-1), determined from high-field, high-frequency electron paramagnetic resonance spectra, together with a weak antiferromagnetic exchange parameter J = -0.477 cm(-1), allowed us to reproduce the powder magnetic susceptibility and field-dependent magnetization of the complex. The biological activity of 1 has been tested by using the Fusarium solani, Penicillium verrucosum, and Aspergillus flavus fungi strains and Escherichia coli, Pseudomonas fluorescens, Serratia marcescens, and Bacillus subtilis bacterial strains. PMID:23534408

Wojciechowska, Agnieszka; G?gor, Anna; Duczmal, Marek; Staszak, Zbigniew; Ozarowski, Andrzej

2013-04-15

156

COMPLEX IDENTIFICATION OF THERMOPHYSICAL PROPERTIES OF ANISOTROPIC COMPOSITE MATERIAL  

Microsoft Academic Search

The statement and solution algorithm of a two-dimensional thermal conductivity inverse problem on complex identification of thermophysical properties of anisotropic complex material is presented. An experimental facility for carrying out thermophysical research has been worked out. The problem of optimal designing of temperature measurements has been solved in the course of the experiment. Data on the complex of thermophysical properties

O. M. ALIFANOV; Y. JARNY

157

Magnetic properties of a SnO2 quantum dot  

NASA Astrophysics Data System (ADS)

By using first-principles calculations, the magnetic properties of a SnO2 quantum dot (QD) are investigated. It is found that dangling bonds (DBs) are equated with Co (Ni) dopants, which can induce magnetic moments in SnO2 QDs. Thus, the QD shows very abundant variation of the magnetic properties by combining dopants with DBs. The changes of magnetic moments can be explained well by a carrier modulation model.

Zhang, Yong; Tang, Li-Ming; Tang, Zhen-Kun; Ning, Feng; Chen, Ke-Qiu

2013-09-01

158

Effect of an Oscillating Magnetic Field on the Release Properties of Magnetic Collagen Gels  

E-print Network

Effect of an Oscillating Magnetic Field on the Release Properties of Magnetic Collagen Gels Vania M properties of collagen gels containing magnetic nanoparticles and microparticles and fluorescent drug analogues. Collagen gels were prepared through fibrillogenesis of collagen in the presence of iron oxide

Spinu, Leonard

159

Magnetic Properties of the Chelyabinsk meteorite  

NASA Astrophysics Data System (ADS)

The Chelyabinsk meteorite (the fall of February 15, 2013; Russia) is a LL5 ordinary chondrite. Numerous (thousands) stones fell as a shower to the south and the south-west of the city of Chelyabinsk. The stones consist of two intermixed lithologies, with the majority (2/3) being a light lithology with a typical chondritic texture and shock stage S4 (~30 GPa). The second lithology (1/3) is an impact melt breccia (IMB) consisting of blackened chondrite fragments embedded in a fine-grained matrix. We investigated the magnetic properties of the meteorite stones collected immediately after the fall by the expedition of the Vernadsky Institute, Moscow. The low-field magnetic susceptibility (?0) of 174 fragments (135 chondritic and 39 IMB) weighing >3 g was measured. Each sample was measured three times in mutually perpendicular directions to average anisotropy. Also hysteresis loops (saturation magnetization Ms, coercivity Bc) and back-field remanence demagnetization curves (coercivity of remanence Bcr) in the temperature range from 10K to 700°C and other characteristics of some pieces (NRM, SIRM with their thermal and alternating field demagnetization spectra) were acquired. The mean log?0 is 4.57×0.09 (s.d.) for the light lithology and 4.65×0.09 (s.d.) (×10-9 m3/kg) for the IMB, indicating that IMB is slightly richer in metal than the light chondritic lithology. According to [1], Chelyabinsk is three times more magnetic than the average LL5 fall, but similar to other metal-rich LL5 (e.g., Paragould, Aldsworth, Bawku, Richmond), as well as L/LL chondrites (e.g., Glanerbrug, Knyahinya, Qidong). The estimation of metal content from the Ms value gives 3.7 wt.% for the light fragments and 4.1 wt.% for IMB whereas the estimation from ?0 yields overestimated contents, e.g., 6.9 wt.% for the light lithology. Thermomagnetic curves Ms(T) up to 800°C identify the main magnetic carriers at room temperature (T0) and above as taenite and kamacite (no tetrataenite found), in accordance with mineralogical data. Additional magnetic analyses [2] confirm the absence of tetrataenite and show that metal grains are primarily multidomain and magnetically soft (Bc<2 mT and Bcr<23 mT) at T0. However, at temperatures <75 K, the magnetic remanence of the Chelyabinsk chondrite is dominated by high coercivity chromite with much higher Bcr (606 mT for the light lithology and 157 mT for IMB). These results are consistent with previously published data on ordinary chondrites [3]. Acknowledgments: This research was funded by a U.S. National Science Foundation IRM Visiting Fellowship. References: [1] Rochette P. et al. 2003. MAPS 38: 251-268. [2] Bezaeva N.S. et al. 2013. Geochem. Int. 51(7): 568-574. [3] Gattacceca J. et al. 2011. Geoph. Res. Lett. 38: L10203.

Bezaeva, N. S.; Badyukov, D. D.; Nazarov, M. A.; Rochette, P.; Feinberg, J. M.

2013-12-01

160

Magnetic properties of double perovskite La2BMnO6 (B = Ni or Co) nanoparticles  

SciTech Connect

Double perovskite La2BMnO6 (B = Ni and Co) nanoparticles with average particle size of ~50 nm were synthesized using a facile, environmentally friendly, scalable molten-salt reaction at 700 °C in air. Their structural and morphological properties were characterized by x-ray diffraction and transmission electron microscopy. Magnetic properties were evaluated using dc magnetic M-T and M-H, and ac magnetic susceptibility versus frequency, temperature, and field. The magnetization curve shows a paramagnetic-ferromagnetic transition at TC ~275 and 220 K for La2NiMnO6 (LNMO) and La2CoMnO6 (LCMO) nanoparticles, respectively. ac susceptibility revealed that the LCMO had a single magnetic transition indicative of Co2+-O2--Mn4+ ordering, whereas the LNMO showed more complex magnetic behavior suggesting a re-entrant spin glass.

Mao, Yuanbing; Parsons, Jason; McCloy, John S.

2013-03-31

161

Magnetic properties of graphene quantum dots  

NASA Astrophysics Data System (ADS)

Using the tight-binding approximation we calculated the diamagnetic susceptibility of graphene quantum dots (GQDs) of different geometrical shapes and characteristic sizes of 2-10 nm, when the magnetic properties are governed by the electron edge states. Two types of edge states can be discerned: the zero-energy states (ZESs), located exactly at the zero-energy Dirac point, and the dispersed edge states (DESs), with the energy close but not exactly equal to zero. DESs are responsible for a temperature-independent diamagnetic response, while ZESs provide a temperature-dependent spin paramagnetism. Hexagonal, circular, and randomly shaped GQDs contain mainly DESs, and, as a result, they are diamagnetic. The edge states of the triangular GQDs are of ZES type. These dots reveal the crossover between spin paramagnetism, dominating for small dots and at low temperatures, and orbital diamagnetism, dominating for large dots and at high temperatures.

Espinosa-Ortega, T.; Luk'yanchuk, I. A.; Rubo, Y. G.

2013-05-01

162

nanowires: structural characterizations, optical and magnetic properties  

NASA Astrophysics Data System (ADS)

In this paper, 1D single-crystalline MnO2 nanowires have been successfully synthesized by hydrothermal method using KMnO4 and (NH4)2S2O8 as raw materials. X-ray diffraction patterns and high-resolution TEM images reveal pure tetragonal MnO2 phase with diameters of 15-20 nm. Photoluminescence studies exhibited a strong ultraviolet (UV) emission band at 380 nm, blue emission at 452 nm and an extra weak defect-related green emission at 542 nm. UV-visible spectrophotometery was used to determine the absorption behavior of nanostructured MnO2 and a direct optical band gap of 2.5 eV was acquired by Davis-Mott model. The magnetic properties of the products have been evaluated using vibrating sample magnetometer, which showed that MnO2 nanowires exhibited a superparamagnetic behavior at room temperature. The magnetization versus temperature curve of the as-obtained MnO2 nanowires shows that antiferromagnetic transition temperature is 99 K.

Toufiq, Arbab Mohammad; Wang, Fengping; Javed, Qurat-ul-ain; Li, Quanshui; Li, Yan

2014-09-01

163

Matching Martian Magnetic Anomalies and Snc Magnetic Properties  

Microsoft Academic Search

Understanding the origin of Martian magnetic anomalies is a major challenge for Martian studies, both in terms of planetary geodynamics and of magnetic petrology. Present models require a crustal magnetization of 15-30 A\\/m with a thickness of 20-50 km [e.g. 1]. SNC meteorites are the only material available to make a magnetominer- alogical model for this crustal magnetization. Here will

P. Rochette; V. Sautter; F. Brunet; V. Chevrier; J. P. Lorand

2002-01-01

164

Magnetic properties modeling of soft magnetic composite materials using two-dimensional vector hybrid hysteresis model  

NASA Astrophysics Data System (ADS)

A 2-D vector hybrid hysteresis model for a soft magnetic composite (SMC) material is established, which is combined with classical Preisach model and Stoner-Wohlfarth (S-W) model. The rotational magnetic properties of SMC materials were studied using the vector model, and the computed results were compared with the experimental measurement. It is shown that the vector hybrid model can effectively simulate the rotational magnetic properties under low magnetization fields.

Li, Dandan; Liu, Fugui; Li, Yongjian; Zhao, Zhigang; Zhang, Changgeng; Yang, Qingxin

2014-05-01

165

Magnetic Properties of Lunar Geologic Terranes: New Statistical Results  

NASA Technical Reports Server (NTRS)

We use global magnetic field data and digitized geologic maps to determine the magnetic properties of lunar terranes. Average fields vary by a factor of 100 from demagnetized impact basins and craters to strongly magnetized antipodal regions. Additional information is contained in the original extended abstract.

Halekas, J. S.; Mitchell, D. L.; Lin, R. P.; Frey, S.; Hood, L. L.; Acuna, M. H.; Binder, A.

2002-01-01

166

Ground State Magnetic Properties of Fe Nanoislands on Cu(111)  

NASA Astrophysics Data System (ADS)

We investigate magnetic properties of Fe nanoislands on Cu(111) in the relaxed structure within the density functional theory. We observe that the nanoislands exhibit the ferromagnetic properties with large magnetic moment. We find that the change in the magnetic moment of each Fe atom is induced by deposition on Cu(111) and structure relaxation of Fe nanoislands. Moreover, we examine the stability of ferromagnetic states of Fe nanoislands by performing the total energy calculations.

Kishi, Tomoya; David, Melanie; Diño, Wilson Agerico; Nakanishi, Hiroshi; Kasai, Hideaki; Komori, Fumio

2005-11-01

167

Soft Magnetic Properties of FeN\\/FeBN Multilayers  

Microsoft Academic Search

stract-The magnetic and structural properties of multilayered FeN\\/FeBN films prepared by dual-target sputtering were investigated. Laminating FeBN films with FeN films increases the electrical resistivity (R) by up to 200 ¿¿-cm, decreases slightly the saturation magnetization and results in excellent soft magnetic properties (coercivity ¿0.2 Oe and permeability ¿1000) over a wide range of film thickness combinations; this despite the

S. Ohnuma; F. Matsumoto; H. Fujimori; T. Masumoto

1992-01-01

168

Redox-active porous coordination polymers prepared by trinuclear heterometallic pivalate linking with the redox-active nickel(II) complex: synthesis, structure, magnetic and redox properties, and electrocatalytic activity in organic compound dehalogenation in heterogeneous medium.  

PubMed

Linking of the trinuclear pivalate fragment Fe2CoO(Piv)6 by the redox-active bridge Ni(L)2 (compound 1; LH is Schiff base from hydrazide of 4-pyridinecarboxylic acid and 2-pyridinecarbaldehyde, Piv(-) = pivalate) led to formation of a new porous coordination polymer (PCP) {Fe2CoO(Piv)6}{Ni(L)2}1.5 (2). X-ray structures of 1 and 2 were determined. A crystal lattice of compound 2 is built from stacked 2D layers; the Ni(L)2 units can be considered as bridges, which bind two Fe2CoO(Piv)6 units. In desolvated form, 2 possesses a porous crystal lattice (SBET = 50 m(2) g(-1), VDR = 0.017 cm(3) g(-1) estimated from N2 sorption at 78 K). At 298 K, 2 absorbed a significant quantity of methanol (up to 0.3 cm(3) g(-1)) and chloroform. Temperature dependence of molar magnetic susceptibility of 2 could be fitted as superposition of ?MT of Fe2CoO(Piv)6 and Ni(L)2 units, possible interactions between them were taken into account using molecular field model. In turn, magnetic properties of the Fe2CoO(Piv)6 unit were fitted using two models, one of which directly took into account a spin-orbit coupling of Co(II), and in the second model the spin-orbit coupling of Co(II) was approximated as zero-field splitting. Electrochemical and electrocatalytic properties of 2 were studied by cyclic voltammetry in suspension and compared with electrochemical and electrocatalytic properties of a soluble analogue 1. A catalytic effect was determined by analysis of the catalytic current dependency on concentrations of the substrate. Compound 1 possessed electrocatalytic activity in organic halide dehalogenation, and such activity was preserved for the Ni(L)2 units, incorporated into the framework of 2. In addition, a new property occurred in the case of 2: the catalytic activity of PCP depended on its sorption capacity with respect to the substrate. In contrast to homogeneous catalysts, usage of solid PCPs may allow selectivity due to porous structure and simplify separation of product. PMID:24779588

Lytvynenko, A S; Kolotilov, S V; Kiskin, M A; Cador, O; Golhen, S; Aleksandrov, G G; Mishura, A M; Titov, V E; Ouahab, L; Eremenko, I L; Novotortsev, V M

2014-05-19

169

Physical properties of novel magnetic heterostructures  

NASA Astrophysics Data System (ADS)

There is an ongoing interest in studying the novel magnetic systems, such as giant magnetoresistance structures (GMR), magnetic dilute semiconductors and various magnetic nanostructures. In the first part of my dissertation I present the results of our work concerning the possibility of using ferromagnetic metallic manganites as basic elements for various GMR heterostructures. I start by studying the phase diagram of manganites using the general band approach. As it turns out, the basic properties of manganites to a large extent are determined by cooperative Jahn-Teller effects and the Hund's rule coupling. The transition from insulating antiferromagnetic to metallic ferromagnetic state at critical doping concentration xcr is treated by means of the percolation theory. Using two-band approach in the frame of variational mean field theory we provide an estimate for the value of the Curie temperature in doped manganites. Then using the double exchange (DE) model via degenerate orbitals and the tight-binding approximation we study the magnetoconductivity of a canted A-phase of pseudo-cubic manganites. It is argued that the model is applicable in a broad concentration range for manganites A1-xB xMnO3 with the tolerance factor, t, close to one. As for the substitutional disorder, scattering on random Jahn-Teller distortions of MnO6 octahedra is chosen. We emphasize an intimate correlation between the carrier concentration and resistivity value of metallic manganites. Magnetoresistance as a function of magnetization is calculated for a canted A-phase for both in-plane and out-of-plane current directions. A contact between two manganite phases is considered and structure of the transition region near the contact is discussed. Numerical calculations show charge re-distribution near the contact and a large screening length of the order of five inter-atomic distances. We employed our results to interpret data obtained in recent experiments on La0.4Sr0.6MnO 3/La0.55Sr0.45MnO3 superlattices. We also briefly discuss the relative importance of the cooperative Jahn-Teller distortions, double exchange mechanism and super-exchange interactions for the formation of the A-phase at increasing Sr concentrations x > 0.45 in La1-xSr xMnO3 to suggest that the Jahn-Teller contraction of octahedra, c/a < 1, plays a prevailing role. The second part of my thesis deals with the analysis of magnetotransport properties of ferromagnetic nanowires. The problems associated with spin-accumulation effects near the domain walls boundaries are studied in detail. In order to explain the large values of magnetoresistance due to domain wall scattering in ferromagnetic nanowires we suggest the realization of "linear domain walls".

Dzero, Maxim O.

170

Silver-perfluorodecanethiolate complexes having superhydrophobic, antifouling, antibacterial properties.  

PubMed

Silver-perfluorodecanethiolate complexes having superhydrophobic, antifouling, antibacterial properties were prepared by a reaction of silver nitrate with perfluorodecanethiol. When the silver nitrate to perfluorodecanethiol molar ratio was 1/2, silver-perfluorodecanethiolate complexes having hierarchical micro-/nano-sized wire shapes were obtained, and they showed superhydrophobic and antifouling properties. After UV irradiation, silver nanoparticles were generated on the wires and exhibited antibacterial properties. PMID:22018531

Chung, Jae-Seung; Kim, Byoung Gak; Shim, Soojin; Kim, Seong-Eun; Sohn, Eun-Ho; Yoon, Jeyong; Lee, Jong-Chan

2012-01-15

171

Magnetic properties of self-assembled Fe nanoislands on BaTiO3(001)  

NASA Astrophysics Data System (ADS)

The coercivity and saturation magnetization of ultrathin films of Fe on a BaTiO3(001) single crystal substrate have been determined using magneto-optic Kerr effect (MOKE) and X-ray magnetic circular dichroism (XMCD) as a function of annealing temperature. Films deposited at room temperature exhibit bulk-like properties, whereas with increasing annealing temperature coercivity increases and saturation magnetization decreases. Investigations with scanning electron microscopy (SEM) and low-energy electron diffraction (LEED) reveal that annealing causes a morphology transformation from a continuous flat film, which completely covers the substrate, to nanoislands via self-assembled growth. The morphology and size of the islands imply stronger pinning of domain walls or complex magnetic structures as the origin of their particular magnetic properties.

Govind, R. K.; Hari Babu, V.; Chiang, C.-T.; Magnano, E.; Bondino, F.; Denecke, R.; Schindler, K.-M.

2013-11-01

172

Synthesis, Characterization, In Vitro Cytotoxicity, and Apoptosis-Inducing Properties of Ruthenium(II) Complexes  

PubMed Central

Two new Ru(II) complexes, [Ru(bpy)2(FAMP)](ClO4)2 1 and 2, are synthesized and characterized by elemental analysis, electrospray mass spectrometry, and 1H nuclear magnetic resonance. The in vitro cytotoxicities and apoptosis-inducing properties of these complexes are extensively studied. Complexes 1 and 2 exhibit potent antiproliferative activities against a panel of human cancer cell lines. The cell cycle analysis shows that complexes 1 and 2 exhibit effective cell growth inhibition by triggering G0/G1 phase arrest and inducing apoptosis by mitochondrial dysfunction. The in vitro DNA binding properties of the two complexes are investigated by different spectrophotometric methods and viscosity measurements. PMID:24804832

Xu, Li; Zhong, Nan-Jing; Xie, Yang-Yin; Huang, Hong-Liang; Jiang, Guang-Bin; Liu, Yun-Jun

2014-01-01

173

Complex Dielectric Properties of Sulfate-Reducing Bacteria Suspensions  

Microsoft Academic Search

Sulfate-reducing bacteria (SRB) can potentially enhance the remediation of heavy metals in the subsurface. Previous geophysical research has demonstrated the sensitivity of electrical measurements to SRB mediated mineral transformation in porous media. However, the inherent dielectric properties of SRB and their direct contribution to the electrical properties of porous media are poorly understood. We studied the complex dielectric properties of

Chi Zhang; Lee Slater; Camelia Prodan

2012-01-01

174

Magnetic properties of intermediate-mass stars  

E-print Network

Magnetic fields play an important role in producing and modifying the photospheric chemical peculiarities of intermediate-mass main sequence stars. This article discusses the basic theory and methods of measurement used to detect and characterise stellar magnetic fields, and reviews our current knowledge of selected characteristics of magnetic fields in intermediate-mass stars.

G. A. Wade

2006-01-26

175

Magnetic and elastic properties in the paramagnetic state of NdIn 3 antiferromagnet  

NASA Astrophysics Data System (ADS)

The cubic AuCu 3 type system NdIn 3 exhibits complex magnetic structures at low temperature. Immediately below the Néel temperature, TN = 6 K, the spins assume a sine wave modulated arrangement; for 5.5 K > T > 4.7 K, the modulation tends towards a square wave. Finally, below 4.7 K, a simple commensurate structure is stabilized. We first confirm here the complex magnetic phase diagram by means of resistivity measurements. In order to quantitatively understand the low temperature properties, the crystalline electric field is determined by inelastic neutron spectroscopy. An extensive study of the magnetic, magnetoelastic and quadrupolar properties in the paramagnetic phase by magnetization, ultrasonic velocity and parastriction measurements is then presented. The values of one-ion magnetoelastic coefficients agree with previous determinations in isomorphous systems. Quadrupolar pair interactions are found to be positive for the tetragonal symmetry lowering mode, in agreement with the symmetry of collinear magnetic structures. However the only quadrupolar model fails to coherently describe the whole set of paramagnetic properties, in particular the third order magnetic susceptibility. The existence of two-ion magnetoelasticity is then discussed in relation to the ultrasonic velocity and parastriction results. The description of the magnetic phase diagrams will be reported elsewhere.

Amara, M.; Morin, P.; Rouchy, J.

1994-02-01

176

Improved Electrical Insulation of Rare Earth Permanent Magnetic Materials With High Magnetic Properties  

Microsoft Academic Search

Rare earth permanent magnetic materials are typical electrical conductor, and their magnetic properties will decrease because of the eddy current effect, so it is difficult to keep them stable for a long enough time under a high frequency AC field. In the present study, as far as rare earth permanent magnets are concerned, for the first time, rare earth permanent

Ying CHANG; Da-peng WANG; Wei LI; Wei PAN; Xiao-jun YU; Min QI

2009-01-01

177

Viking magnetic properties investigation - Preliminary results  

NASA Technical Reports Server (NTRS)

Three permanent-magnet arrays are aboard the Viking lander. By sol 35, one array, fixed on a photometric reference test chart on top of the lander, has clearly attracted magnetic particles from airborne dust; two other magnet arrays, one strong and one weak, incorporated in the backhoe of the surface sampler, have both extracted considerable magnetic mineral from the surface as a result of nine insertions associated with sample acquisition. The loose Martian surface material around the landing site is judged to contain 3 to 7 per cent highly magnetic mineral which, pending spectrophotometric study, is thought to be mainly magnetite.

Hargraves, R. B.; Collinson, D. W.; Spitzer, C. R.

1976-01-01

178

Six-Coordinate Lanthanide Complexes: Slow Relaxation of Magnetization in the Dysprosium(III) Complex.  

PubMed

A series of six-coordinate lanthanide complexes {(H3 O)[Ln(NA)2 ]?H2 O}n (H2 NA=5-hydroxynicotinic acid; Ln=Gd(III) (1?Gd); Tb(III) (2?Tb); Dy(III) (3?Dy); Ho(III) (4?Ho)) have been synthesized from aqueous solution and fully characterized. Slow relaxation of the magnetization was observed in 3?Dy. To suppress the quantum tunneling of the magnetization, 3?Dy diluted by diamagnetic Y(III) ions was also synthesized and magnetically studied. Interesting butterfly-like hysteresis loops and an enhanced energy barrier for the slow relaxation of magnetization were observed in diluted 3?Dy. The energy barrier (?? ) and pre-exponential factor (?0 ) of the diluted 3?Dy are 75?K and 4.21×10(-5) ?s, respectively. This work illustrates a successful way to obtain low-coordination-number lanthanide complexes by a framework approach to show single-ion-magnet-like behavior. PMID:25297951

Na, Bo; Zhang, Xue-Jing; Shi, Wei; Zhang, Yi-Quan; Wang, Bing-Wu; Gao, Chen; Gao, Song; Cheng, Peng

2014-11-24

179

Magnetic and microstructural properties of some lodestones  

NASA Technical Reports Server (NTRS)

A lodestone is an iron ore that behaves as a permanent magnet. A protolodestone is an iron ore capable of being charged sufficiently strongly to behave as a permanent magnet. In the present paper, important criteria are established which distinguish lodestones from other iron ores. Magnetic hysteresis-loop data provide evidence that the massive pieces of lodestone behave magnetically as fine intergrowths rather than coarse multidomain material. This means that the iron ores have been magnetically hardened. The nature and scale of the hardening microstructure is illustrated by photo micrographs. The mechanism of charging the protolodestone appears to be either transient magnetic fields with lightning-discharge currents, or presently obscure aspects of magnetization intensity enhancement associated with maghemitization of massive iron ores.

Wasilewski, P. J.

1977-01-01

180

FeNi-based magnetic layered nanostructures: Magnetic properties and giant magnetoimpedance  

NASA Astrophysics Data System (ADS)

Magnetic properties and the magnetoimpedance (MI) effect were studied for a series of [Fe20Ni80/Ti]n/Fe20Ni80 (n=0 to 5) nanostructures, prepared by dc magnetron sputtering. The thickness of the FeNi layers was selected as 170 nm in order to avoid the appearance of the "transcritical" state that takes place for thicker layers. First, the influence of the Ti layer thickness was determined for n=1 trilayers, with Ti layers ranging from 2 to 20 nm. The minimum coercivity corresponded to a Ti layer of about 6 nm. Second, the magnetic properties and MI responses were studied for different [FeNi/Ti]n/FeNi structures at a fixed Ti layer thickness of 6 nm. The complex impedance was measured for a frequency range of 1-300 MHz. The highest value of the MI was obtained in the sample [FeNi/Ti]5/FeNi with the largest total thickness.

Kurlyandskaya, G. V.; Svalov, A. V.; Fernandez, E.; Garcia-Arribas, A.; Barandiaran, J. M.

2010-05-01

181

Intrinsic and extrinsic magnetic properties of the naturally layered manganites  

SciTech Connect

Structural and magnetic properties of the two-layered Ruddlesden-Popper phase SrO(La{sub 1{minus}x}Sr{sub x}MnO{sub 3}){sub 2} with x = 0.3--0.5 are highlighted. Intrinsic properties of these naturally layered manganites include a colossal magnetoresistance, a composition-dependent magnetic anisotropy, and almost no remanence. Above the Curie temperature there is a non-vanishing extrinsic magnetization attributed to intergrowths (stacking faults in the layered structure). These lattice imperfections consist of additional or missing manganite layers, as observed in transmission electron microscopy. Their role in influencing the properties of the host material is highlighted.

Berger, A.; Mitchell, J. F.; Miller, D. J.; Jiang, J. S.; Bader, S. D.

1999-11-30

182

Magnetic properties and magnetic structure of HoTiGe and ErTiGe  

Microsoft Academic Search

We have studied the crystal structure, magnetic structure and magnetic properties of the tetragonal compounds HoTiGe and ErTiGe by means of neutron diffraction and magnetic measurements. The neutron-diffraction measurements were made in the range from 1.7 K to temperatures above the corresponding magnetic-ordering temperatures (TN=88 and 41 K, respectively). Both compounds have a simple antiferromagnetic structure with a propagation vector

K. Prokes; O. Tegus; E. H. Bruck; J. C. P. Klaasse; F. R de Boer; K. H. J. Buschow

2002-01-01

183

Viking magnetic properties investigation - Further results  

NASA Technical Reports Server (NTRS)

The amounts of magnetic particles held on the reference test chart and backhoe magnets on lander 2 and lander 1 are comparable, indicating the presence of an estimated 3 to 7 percent by weight of relatively pure, strongly magnetic particles in the soil at the lander 2 sampling site. Preliminary spectrophotometric analysis of the material held on the backhoe magnets on lander 1 indicates that its reflectance characteristics are indistinguishable from material within a sampling trench with which it has been compared. The material on the RTC magnet shows a different spectrum, but it is suspected that the difference is the result of a reflectance contribution from the magnesium metal covering on the magnet. It is argued that the results indicate the presence, now or originally, of magnetite, which may be titaniferous.

Hargraves, R. B.; Collinson, D. W.; Arvidson, R. E.; Spitzer, C. R.

1976-01-01

184

Induction of Biogenic Magnetization and Redox Control by a Component of the Target of Rapamycin Complex 1 Signaling Pathway  

PubMed Central

Most organisms are simply diamagnetic, while magnetotactic bacteria and migratory animals are among organisms that exploit magnetism. Biogenic magnetization not only is of fundamental interest, but also has industrial potential. However, the key factor(s) that enable biogenic magnetization in coordination with other cellular functions and metabolism remain unknown. To address the requirements for induction and the application of synthetic bio-magnetism, we explored the creation of magnetism in a simple model organism. Cell magnetization was first observed by attraction towards a magnet when normally diamagnetic yeast Saccharomyces cerevisiae were grown with ferric citrate. The magnetization was further enhanced by genetic modification of iron homeostasis and introduction of ferritin. The acquired magnetizable properties enabled the cells to be attracted to a magnet, and be trapped by a magnetic column. Superconducting quantum interference device (SQUID) magnetometry confirmed and quantitatively characterized the acquired paramagnetism. Electron microscopy and energy-dispersive X-ray spectroscopy showed electron-dense iron-containing aggregates within the magnetized cells. Magnetization-based screening of gene knockouts identified Tco89p, a component of TORC1 (Target of rapamycin complex 1), as important for magnetization; loss of TCO89 and treatment with rapamycin reduced magnetization in a TCO89-dependent manner. The TCO89 expression level positively correlated with magnetization, enabling inducible magnetization. Several carbon metabolism genes were also shown to affect magnetization. Redox mediators indicated that TCO89 alters the intracellular redox to an oxidized state in a dose-dependent manner. Taken together, we demonstrated that synthetic induction of magnetization is possible and that the key factors are local redox control through carbon metabolism and iron supply. PMID:22389629

Nishida, Keiji; Silver, Pamela A.

2012-01-01

185

Induction of biogenic magnetization and redox control by a component of the target of rapamycin complex 1 signaling pathway.  

PubMed

Most organisms are simply diamagnetic, while magnetotactic bacteria and migratory animals are among organisms that exploit magnetism. Biogenic magnetization not only is of fundamental interest, but also has industrial potential. However, the key factor(s) that enable biogenic magnetization in coordination with other cellular functions and metabolism remain unknown. To address the requirements for induction and the application of synthetic bio-magnetism, we explored the creation of magnetism in a simple model organism. Cell magnetization was first observed by attraction towards a magnet when normally diamagnetic yeast Saccharomyces cerevisiae were grown with ferric citrate. The magnetization was further enhanced by genetic modification of iron homeostasis and introduction of ferritin. The acquired magnetizable properties enabled the cells to be attracted to a magnet, and be trapped by a magnetic column. Superconducting quantum interference device (SQUID) magnetometry confirmed and quantitatively characterized the acquired paramagnetism. Electron microscopy and energy-dispersive X-ray spectroscopy showed electron-dense iron-containing aggregates within the magnetized cells. Magnetization-based screening of gene knockouts identified Tco89p, a component of TORC1 (Target of rapamycin complex 1), as important for magnetization; loss of TCO89 and treatment with rapamycin reduced magnetization in a TCO89-dependent manner. The TCO89 expression level positively correlated with magnetization, enabling inducible magnetization. Several carbon metabolism genes were also shown to affect magnetization. Redox mediators indicated that TCO89 alters the intracellular redox to an oxidized state in a dose-dependent manner. Taken together, we demonstrated that synthetic induction of magnetization is possible and that the key factors are local redox control through carbon metabolism and iron supply. PMID:22389629

Nishida, Keiji; Silver, Pamela A

2012-01-01

186

Magnetically Regulated Star Formation in 3D: The Case of Taurus Molecular Cloud Complex  

E-print Network

We carry out three-dimensional MHD simulations of star formation in turbulent, magnetized clouds, including ambipolar diffusion and feedback from protostellar outflows. The calculations focus on relatively diffuse clouds threaded by a strong magnetic field capable of resisting severe tangling by turbulent motions and retarding global gravitational contraction in the cross-field direction. They are motivated by observations of the Taurus molecular cloud complex (and, to a lesser extent, Pipe Nebula), which shows an ordered large-scale magnetic field, as well as elongated condensations that are generally perpendicular to the large-scale field. We find that stars form in earnest in such clouds when enough material has settled gravitationally along the field lines that the mass-to-flux ratios of the condensations approach the critical value. Only a small fraction (of order 1% or less) of the nearly magnetically-critical, condensed material is turned into stars per local free-fall time, however. The slow star formation takes place in condensations that are moderately supersonic; it is regulated primarily by magnetic fields, rather than turbulence. The quiescent condensations are surrounded by diffuse halos that are much more turbulent, as observed in the Taurus complex. Strong support for magnetic regulation of star formation in this complex comes from the extremely slow conversion of the already condensed, relatively quiescent C$^{18}$O gas into stars, at a rate two orders of magnitude below the maximum, free-fall value. We analyze the properties of dense cores, including their mass spectrum, which resembles the stellar initial mass function.

Fumitaka Nakamura; Zhi-Yun Li

2008-04-26

187

A study on the magnetic properties of two-phase particulate magnetic composites  

NASA Astrophysics Data System (ADS)

The magnetic properties of two-phase particulate magnetic composites with a hard ferromagnetic component are studied theoretically and experimentally. The magnetic properties considered here are phase-distribution sensitive properties, including remanence, coercivity and the shape of hysteresis loop. These properties depend mainly on the properties of its constituents, volume fractions, phase distribution, packing fraction and orientation distribution for anisotropic particles. With fixed packing fraction and orientation distribution, the magnetic properties of the two phase mixture can be calculated in terms of its component properties, volume fractions and phase distribution. Here, the component properties include not only remanence Br and coercivity Hc but also a variable m which is the rate of change of magnetic induction B with respect to field intensity H. For two-phase systems satisfying B - H relation of the type B = Br + mH where m is a constant, the equations for calculating the magnetic properties Br, Hc, etc., in terms of m are derived. The method for calculating m is also developed for the cases of parallel and series distributions. Bounds for m-values were also established. A modified Landauer's type equation is developed to calculate m-values in terms of the component properties of the mixture. Experiments were conducted to verify the theoretical calculations. Good agreements between the theoretical calculations and experimental results were obtained.

Wang, Keun-Long; Hsu, Shu-en; Chen, J.

1982-11-01

188

Single-molecule magnets based on rare earth complexes with chelating benzimidazole-substituted nitronyl nitroxide radicals.  

PubMed

Three rare earth-nitronyl nitroxide radical complexes [Ln(tfa)(3)(NIT-BzImH)] (Ln(III) = Gd 1, Tb 2, Dy 3; tfa = trifluoroacetylacetonate; NIT-BzImH = 2-(2'-benzimidazolyl)-4,4,5,5-tetramethylimidazolyl-1-oxyl-3-oxide) have been successfully prepared and structurally characterized. X-Ray crystallographic analysis reveals that all three complexes are isomorphous. Their crystal structures consist of mononuclear molecule units in which lanthanide(III) is 8-coordinated to one NIT-BzImH and three trifluoroacetylacetonate ligands. The NIT-BzImH acts as a bidentate ligand via its nitrogen atom of the imidazole ring and the oxygen atom of the N-O group. The magnetic properties of complexes 1-3 were studied. All the three complexes exhibit ferromagnetic Ln(III)-radical coupling. AC magnetic susceptibility studies of 2 and 3 show slow magnetic relaxation suggesting that they behave as SMMs. PMID:23051718

Hu, Peng; Zhu, Mei; Mei, Xuelan; Tian, Haixia; Ma, Yue; Li, Licun; Liao, Daizheng

2012-12-28

189

Tuning the photophysical properties of amidophosphine complexes of copper  

E-print Network

A series of monomeric copper complexes that allow for the tuning of the emission properties is reported. Luminescence lifetimes up to 150 [mu]s are observed in benzene solution at ambient temperature, which are comparable ...

Mickenberg, Seth F. (Seth Fox)

2009-01-01

190

Properties of Magnetic Neutral Lines and Filament Formation  

NASA Astrophysics Data System (ADS)

Chromospheric filaments form at a boundary (neutral lines) between opposite polarity magnetic fields. Both the total length of neutral lines and the number of filaments vary with solar cycle. However, our analysis indicates that the cycle variation in filaments is not due to the change in the total length of neutral lines. It is likely due to change in magnetic properties of neutral lines. In present study we compare properties of magnetic polarity inversion lines that have filaments above them and those without filaments, and investigate how these properties change during the solar cycle. Our results show that the gradient as well as convergence/divergence of magnetic field across neutral lines are not the major factors that determine the places of filament formation. We discuss the role of canceling magnetic features in filament formation and their cycle variation.

Karachik, N.; Pevtsov, A. A.

2011-12-01

191

Bimetallic anionic formyl complexes: synthesis and properties  

SciTech Connect

Three bimetallic anionic complexes, (2) lithium + dimanganese nonacarbonyl formyl/sup -/, (3) lithium + rhenium manganese nonacarbonyl formyl/sup -/, and (4) lithium + cisdirhenium nonacarbonyl formyl, are prepared by the reaction of lithium triethylboron hydride with the corresponding neutral metal carbonyl dimers, dimanganese decacarbonyl and manganese rhenium decarbonyl. 2 has a half-life of ca 8 min at room temperature, 4 is stable for days and is easily isolated as a tetrahydrofuran solvate. When 2 - 4 are treated with electrophiles such as benzaldehyde, iron pentacarbonyl, n-octyl iodide, hydride transfer occurs to produce benzyl alcohol, lithium + iron tetracarbonyl formyl/sup -/ complex, and octane, respectively. 3 is the weakest hydride donor. Reaction of 4 with methyl iodide produces ca 52% methane. The only identifiable product from the pyrolysis of 4 is dirhenium decacarbonyl; photolysis of 4 produces lithium + dirhenium nonacarbonyl hydride. 1 figure.

Tam, W.; Marsi, M.; Gladysz, J.A.

1983-05-11

192

EM Properties of Magnetic Minerals at RADAR Frequencies  

NASA Technical Reports Server (NTRS)

Previous missions to Mars have revealed that Mars surface is magnetic at DC frequency. Does this highly magnetic surface layer attenuate RADAR energy as it does in certain locations on Earth? It has been suggested that the active magnetic mineral on Mars is titanomaghemite and/or titanomagnetite. When titanium is incorporated into a maghemite or magnetite crystal, the Curie temperature can be significantly reduced. Mars has a wide range of daily temperature fluctuations (303K - 143K), which could allow for daily passes through the Curie temperature. Hence, the global dust layer on Mars could experience widely varying magnetic properties as a function of temperature, more specifically being ferromagnetic at night and paramagnetic during the day. Measurements of EM properties of magnetic minerals were made versus frequency and temperature (300K- 180K). Magnetic minerals and Martian analog samples were gathered from a number of different locations on Earth.

Stillman, D. E.; Olhoeft, G. R.

2005-01-01

193

Iron cyclopentadienone complexes: discovery, properties, and catalytic reactivity.  

PubMed

Iron cyclopentadienone complexes have recently received particular attention in organic chemistry. This is due to their easy synthesis from simple and cheap materials, air-water stability, and most importantly for their unique catalytic features arising from the presence of a non-innocent ligand, triggering powerful redox properties. Herein we discuss the properties of such complexes from synthetic and mechanistic points of view, and their applications in original redox-neutral transformations in both racemic and enantioselective series. PMID:24644277

Quintard, Adrien; Rodriguez, Jean

2014-04-14

194

Correlation Between Domain Behavior and Magnetic Properties of Materials  

SciTech Connect

Correlation between length scales in the field of magnetism has long been a topic of intensive study. The long-term desire is simple: to determine one theory that completely describes the magnetic behavior of matter from an individual atomic particle all the way up to large masses of material. One key piece to this puzzle is connecting the behavior of a material's domains on the nanometer scale with the magnetic properties of an entire large sample or device on the centimeter scale. In the first case study involving the FeSiAl thin films, contrast and spacing of domain patterns are clearly related to microstructure and stress. Case study 2 most clearly demonstrates localized, incoherent domain wall motion switching with field applied along an easy axis for a square hysteresis loop. In case study 3, axis-specific images of the complex Gd-Si-Ge material clearly show the influence of uniaxial anisotropy. Case study 4, the only study with the sole intent of creating domain structures for imaging, also demonstrated in fairly simple terms the effects of increasing stress on domain patterns. In case study 5, it was proven that the width of magnetoresistance loops could be quantitatively predicted using only MFM. When all of the case studies are considered together, a dominating factor seems to be that of anisotropy, both magneticrostaylline and stress induced. Any quantitative bulk measurements heavily reliant on K coefficients, such as the saturation fields for the FeSiAl films, H{sub c} in cases 1, 3, and 5, and the uniaxial character of the Gd{sub 5}(Si{sub 2}Ge{sub 2}), transferred to and from the domain scale quite well. In-situ measurements of domain rotation and switching, could also be strongly correlated with bulk magnetic properties, including coercivity, M{sub s}, and hysteresis loop shape. In most cases, the qualitative nature of the domain structures, when properly considered, matched quite well to what might have been expected from theory and calculation, and provided such information in a matter of minutes. In fact, typical characterization in each of these studies was far more complete and reliable with domain imagery to back it up--especially the single crystal and applied field pictures. In these simple cases, it appears that domain imagery may be close to standing alone in magnetic characterization. The surprises in the 10 nm CoFeHfO film, the complexity seen in the polycrystalline Gd-Si-Ge sample and the broad range predictions of the K{sub 1} of the same reinforce the unreliability of making concrete statements based purely on domain imagery of any type, but it may be possible to create standards similar to the types used in optical microscopy for metallography in these complex cases.

Jeffrey Scott Leib

2003-05-31

195

High temperature permeameter for measuring magnetic properties  

NASA Technical Reports Server (NTRS)

Instrument for measuring magnetic permeability of materials undergoing heat treatment as method for monitoring stress relief and tempering is described. Procedure is based on magnetic potentiometer principle with yoke compensating coils to cancel effects of reluctance of yoke and joint gaps. Instrument is heated with specimen being heat treated.

Barranger, J. P.

1972-01-01

196

Magnetic Properties and Structure of Oxyhemoglobin  

Microsoft Academic Search

A review of the published evidence reinforces the conclusion reached by Pauling and Coryell in 1936 (Proc. Natl. Acad. Sci. USA 22, 210-216) that oxyhemoglobin in blood or in solution at 20 degrees has zero magnetic moment and fails to support a recent contradictory suggestion based on magnetic susceptibility of frozen samples at temperatures below 250 K. Predicted values of

Linus Pauling

1977-01-01

197

Complex conductivity of UTX compounds in high magnetic fields  

SciTech Connect

We have performed rf-skin depth (complex-conductivity) and magnetoresistance measurements of anti ferromagnetic UTX compounds (T=Ni and X=Al, Ga, Ge) in applied magnetic fields up to 60 T applied parallel to the easy directions. The rf penetration depth was measured by coupling the sample to the inductive element of a resonant tank circuit and then, measuring the shifts in the resonant frequency {Delta}f of the circuit. Shifts in the resonant frequency {Delta}f are known to be proportional to the skin depth of the sample and we find a direct correspondence between the features in {Delta}f and magnetoresistance. Several first-order metamagnetic transitions, which are accompanied by a drastic change in {Delta}f, were observed in these compounds. In general, the complex-conductivity results are consistent with magnetoresistance data.

Mielke, Charles H [Los Alamos National Laboratory; Mcdonald, Ross D [Los Alamos National Laboratory; Zapf, Vivien [Los Alamos National Laboratory; Altarawneh, M M [Los Alamos National Laboratory; Lacerda, A [Los Alamos National Laboratory; Alsmadi, A M [HASHEMITE UNIV; Alyones, S [HASHEMITE UNIV; Chang, S [NIST; Adak, S [NMSU; Kothapalli, K [NMSU; Nakotte, H [NMSU

2009-01-01

198

Complex conductivity of UTX compounds in high magnetic fields  

SciTech Connect

We have performed Resonance Frequency (RF) skin depth (complex-conductivity) and magnetoresistance measurements of antiferromagnetic UTX compounds (T Ni, and X := AI, Ga, Ge) in applied magnetic fields up to 60 T applied parallel to the easy directions. The RF penetration depth was measured by coupling the sample to the inductive element of a resonant tank circuit and then, measuring the shifts in the resonant frequency {Delta}f of the circuit. Shifts in the resonant frequency {Delta}f are known to be proportional to the skin depth of the sample and we find a direct correspondence between the features in {Delta}f and magnetoresistance. Several first-order metamagnetic transitions, which are accompanied by a drastic change in {Delta}f, were observed in these compounds. In general, the complex-conductivity results are consistent with magnetoresistance data.

Lacerda, Alex Hugo [Los Alamos National Laboratory; Mielke, Charles H [Los Alamos National Laboratory; Mc Donald, Ross D [Los Alamos National Laboratory

2008-01-01

199

Structural and dynamical properties of complex networks  

NASA Astrophysics Data System (ADS)

Recent years have witnessed a substantial amount of interest within the physics community in the properties of networks. Techniques from statistical physics coupled with the widespread availability of computing resources have facilitated studies ranging from large scale empirical analysis of the worldwide web, social networks, biological systems, to the development of theoretical models and tools to explore the various properties of these systems. Following these developments, in this dissertation, we present and solve for a diverse set of new problems, investigating the structural and dynamical properties of both model and real world networks. We start by defining a new metric to measure the stability of network structure to disruptions, and then using a combination of theory and simulation study its properties in detail on artificially generated networks; we then compare our results to a selection of networks from the real world and find good agreement in most cases. In the following chapter, we propose a mathematical model that mimics the structure of popular file-sharing websites such as Flickr and CiteULike and demonstrate that many of its properties can solved exactly in the limit of large network size. The remaining part of the dissertation primarily focuses on the dynamical properties of networks. We first formulate a model of a network that evolves under the addition and deletion of vertices and edges, and solve for the equilibrium degree distribution for a variety of cases of interest. We then consider networks whose structure can be manipulated by adjusting the rules by which vertices enter and leave the network. We focus in particular on degree distributions and show that, with some mild constraints, it is possible by a suitable choice of rules to arrange for the network to have any degree distribution we desire. In addition we define a simple local algorithm by which appropriate rules can be implemented in practice. Finally, we conclude our dissertation with a game theory model on social networks that tracks the dynamical evolution of a group of interacting agents such as diplomats or political lobbyists seeking to rise to a position of influence, by balancing competing interests.

Ghoshal, Gourab

200

Viking magnetic properties experiment - Extended mission results  

NASA Technical Reports Server (NTRS)

The backhoe magnets on Viking Lander (VL) 2 were successfully cleaned, followed by a test involving successive insertions of the cleaned backhoe into the surface. Rapid saturation of the magnets confirmed evidence from primary mission results that the magnetic mineral in the Martian surface is widely distributed, most probably in the form of composite particles of magnetic and nonmagnetic minerals. An image of the VL 2 backhoe taken via the X4 magnifying mirror demonstrates the fine-grained nature of the attracted magnetic material. The presence of maghemite and its occurrence as a pigment in, or a thin coating on, all mineral particles or as discrete, finely divided and widely distributed crystallites, are consistent with data from the inorganic analysis experiments and with laboratory simulations of results of the biology experiments on Mars.

Hargraves, R. B.; Collinson, D. W.; Arvidson, R. E.; Cates, P. M.

1979-01-01

201

Magnetic properties of dense holographic QCD  

E-print Network

We investigate the Sakai-Sugimoto model at nonzero baryon chemical potential in a background magnetic field both in the confined phase and in the deconfined phase with restored chiral symmetry. In this case the 8-brane Chern-Simons term becomes important. In the confined phase it generates a gradient of the pseudo-scalar "pion", which carries a non-vanishing baryon charge. Above a critical value of the chemical potential there is a second order phase transition to a mixed phase which includes also ordinary baryonic matter. However, at fixed baryon charge density the matter is purely "pion"-gradient above a critical magnetic field. In the deconfined chiral-symmetric phase at nonzero chemical potential the magnetic field induces an axial current. We also compute the magnetization of the baryonic matter and find that it is paramagnetic in all three phases but with nonlinear behavior at large magnetic field.

Oren Bergman; Gilad Lifschytz; Matthew Lippert

2008-06-02

202

Magnetic properties of fine NiO Particles  

Microsoft Academic Search

The partial thermo-remanent magnetizations and the apparent susceptibility have been obtained on fine NiO particle in connection with physicochemical properties. The results are interpreted with Néels model of fine antiferromagnetic particles.

P. Mollard; P. Briane; P. Germi; F. Fievet

1978-01-01

203

Giant crystal-electric-field effect and complex magnetic behavior in single-crystalline CeRh3Si2  

NASA Astrophysics Data System (ADS)

Single-crystalline CeRh3Si2 was investigated by means of x-ray diffraction, magnetic susceptibility, magnetization, electrical resistivity, and specific-heat measurements carried out in wide temperature and magnetic field ranges. Moreover, the electronic structure of the compound was studied at room temperature by cerium core-level x-ray photoemission spectroscopy (XPS). The physical properties were analyzed in terms of crystalline electric field and compared with results of ab initio band-structure calculations performed within the density-functional theory approach. The compound was found to crystallize in the orthorhombic unit cell of the ErRh3Si2 type (space group Imma No.74, Pearson symbol: oI24 ) with the lattice parameters a=7.1330(14)Å , b=9.7340(19)Å , and c=5.6040(11)Å . Analysis of the magnetic and XPS data revealed the presence of well-localized magnetic moments of trivalent cerium ions. All the physical properties were found to be highly anisotropic over the whole temperature range studied and influenced by exceptionally strong crystalline electric field with the overall splitting of the 4f1 ground multiplet exceeding 5700 K. Antiferromagnetic order of the cerium magnetic moments at TN=4.70(1)K and their subsequent spin rearrangement at Tt=4.48(1)K manifest themselves as distinct anomalies in the temperature characteristic of all the physical properties investigated and exhibit complex evolution in an external magnetic field. A tentative magnetic B-T phase diagram, constructed for B parallel to the b axis being the easy magnetization direction, shows very complex magnetic behavior of CeRh3Si2 , similar to that recently reported for an isostructural compound CeIr3Si2 . The electronic band-structure calculations corroborated the antiferromagnetic ordering of the cerium magnetic moments and well-reproduced the experimental XPS valence-band spectrum.

Pikul, A. P.; Kaczorowski, D.; Gajek, Z.; St?pie?-Damm, J.; ?lebarski, A.; Werwi?ski, M.; Szajek, A.

2010-05-01

204

Magnetic properties of Ni substituted Y-type barium ferrite  

NASA Astrophysics Data System (ADS)

Y-type barium hexaferrite is attractive material for various applications, such as high frequency antennas and RF devices, because of its interesting magnetic properties. Especially, Ni substituted Y- type hexaferrites have higher magnetic ordering temperature than other Y-type. We have investigated macroscopic and microscopic properties of Y-type barium hexaferrite. Ba2Co2-xNixFe12O22 (x = 0, 0.5, 1.0, 1.5, and 2.0) samples are prepared by solid-state reaction method and studied by X-ray diffraction (XRD), vibrating sample magnetometer, and Mössbauer spectroscopy, as well as a network analyzer for high frequency characteristics. The XRD pattern is analyzed by Rietveld refinement method and confirms the hexagonal structure with R-3m. The hysteresis curve shows ferrimagnetic behavior. Saturation magnetization (Ms) decreases with Ni contents. Ni2+, which preferentially occupies the octahedral site with up-spin sub-lattice, has smaller spin value S of 1 than Co2+ having S = 3/2. The zero-field-cooled (ZFC) measurement of Ba2Co1.5Ni0.5Fe12O22 shows that Curie and spin transition temperatures are found to be 718 K and 209 K, respectively. The Curie temperature TC is increased with Ni contents, while TS is decreased with Ni. The Mössbauer spectra were measured at various temperatures and fitted by using a least-squares method with six sextet of six Lorentzian lines for Fe sites, corresponding to the 3bVI, 6cIV*, 6cVI, 18hVI, 6cIV, and 3aIV sites at below TC. From Mössbauer measurements, we confirmed the spin state of Fe ion to be Fe3+ and obtained the isomer shift (?), magnetic hyperfine field (Hhf), and the occupancy ratio of Fe ions at six sub-lattices. The complex permeability and permittivity are measured between 100 MHz and 4 GHz, suggesting that Y-type barium hexaferrite is promising for antenna applications in UHF band.

Won, Mi Hee; Kim, Chul Sung

2014-05-01

205

Nonlinear optical properties of the magnetized QED Vacuum  

Microsoft Academic Search

New processes associated with the nonlinear optical properties of the electromagnetic vacuum, as predicted by quantum electrodynamics are described. We consider the presence of a static and a rotating magnetic field. The cases of harmonic generation and two different types of sideband cascades are considered. First order and second order effects with respect to the external magnetic field are discussed

J. T. Mendonca

2007-01-01

206

Magnetic properties of sedimentary greigite (Fe 3S 4)  

Microsoft Academic Search

New data are presented here that document the previously poorly known magnetic characteristics of sedimentary greigite (Fe3S4). Several diagnostic magnetic properties can be used in conjunction to rapidly screen sediments to detect the presence of greigite. Such discriminants are necessary because greigite displays a similar (or higher) range of coercivities compared to most ferrimagnetic minerals and the commonly used method

Andrew P. Roberts

1995-01-01

207

Magnetic properties of glass-coated amorphous and nanocrystalline microwires  

Microsoft Academic Search

The magnetic properties of Fe- and Co-based amorphous and nanocrystalline glass-coated microwires are reviewed. Such wires are composed of a metallic amorphous nucleus (3 to 20 ?m diameter) and an insulating glass cover (2 to 12 ?m thick). Interest is mainly focused on samples exhibiting squared hysteresis loops (magnetically bistable) which exhibit positive magnetostriction (bistability can be observed for 2

M. Vázquez; A. P. Zhukov

1996-01-01

208

Mechanical property and dimensional stability of substrates for magnetic tapes  

Microsoft Academic Search

We have performed a comparative study on mechanical property and dimensional stability of substrates for magnetic tapes. The substrates include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and aromatic polyamide (ARAMID), which could be used for linear-type magnetic tapes for computer data storage. We have demonstrated that ARAMID is the most attractive substrate and that PET has the advantage of considerably

T. Higashioji; T. Tsunekawa; B. Bhushan

2003-01-01

209

Electronic and magnetic properties of Am and Cm  

SciTech Connect

A review of the present status of the analyses of the optical spectra of Am and Cm in various oxidation states is given. From these analyses, the magnetic properties of the ground states of these ions can be determined. These predicted values are compared with the various magnetic measurements available.

Edelstein, N.

1985-02-01

210

Synthesis, structures, and magnetic properties of a family of 3d-4f [Na2Fe6Ln2] complexes (Ln = Y, Gd and Dy): effect of ligands on the connection of inorganic subunits.  

PubMed

A family of 3d-4f heterometallic compounds [Na(2)Fe(III)(6)Dy(III)(2)(N(3))(4)(HL)(4)(CH(3)O)(4)(PhCO(2))(6)] (1, H(4)L = 2-{[(2-hydroxy-3-methoxyphenyl)methylene]amino}-2-(hydroxymethyl)-1,3-propanediol), [Na(2)Fe(III)(6)Dy(III)(2)(N(3))(4)(L')(4)(CH(3)O)(4)(PhCO(2))(6)(H(2)O)] (2, H(3)L' = (E)-2-ethyl-2-(2-hydroxy-3-methoxybenzylideneamino)propane-1,3-diol), [Na(2)Fe(III)(6)Dy(III)(2)(N(3))(4)(L')(4)(CH(3)O)(4)(Bu(t)CO(2))(6)] (3) [Na(2)Fe(III)(6)Y(III)(2)(N(3))(4)(L')(4)(CH(3)O)(4)(PhCO(2))(6)(H(2)O)] (4), and [Na(2)Fe(III)(6)Gd(III)(2)(N(3))(4)(L')(4)(CH(3)O)(4)(PhCO(2))(6)(CH(3)OH)(2)] (5) have been prepared using Schiff-base ligands, trinuclear iron precursor complexes, azides and lanthanide nitrates as reactants. In compounds 1 and 2, the structure of the [Na(2)Fe(III)(6)Dy(III)(2)] cluster forms a couple of cis,trans-isomers with substitution of methyl for a free hydroxyl group which belongs to the Schiff-base ligand. When the pivalates are employed instead of bulkier benzoates, the trans-[Na(2)Fe(III)(6)Dy(III)(2)] clusters act as network nodes in the formation of rhombic grid-like layered structures in compound 2. Compounds 2, 4 and 5 have similar metallic cores, only with different crystal solvent molecules. The magnetic measurements on all the compounds indicate dominant antiferromagnetic interactions between the metal centers. PMID:23114511

Zhou, Qi; Yang, Fen; Liu, Dan; Peng, Yu; Li, Guanghua; Shi, Zhan; Feng, Shouhua

2013-01-28

211

Hard magnetic properties of FePd nanoparticles  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles FexPd100-x (x = 42, 50, 55, 60, 63) with small size of around 5-10 nm were prepared by sonochemistry from palladium acetate and iron acetate. The compositions x can be controlled by changing the ratio of the above precursor chemicals. Under the effect of annealing at various temperatures from 450 °C to 650 °C, structure change was observed and samples show hard magnetic properties with high coercivity up to 2.1 kOe. Magnetic properties of samples were then systematically discussed in dependence of x and annealing temperatures. International Workshop on Advanced Materials and Nanotechnology 2012 (IWAMN 2012).

Thi Thanh Van, Nguyen; Thanh Trung, Truong; Hoang Nam, Nguyen; Dang Phu, Nguyen; Hoang Hai, Nguyen; Hoang Luong, Nguyen

2013-10-01

212

Coordination properties of hydralazine Schiff base. Synthesis and equilibrium studies of some metal ion complexes  

NASA Astrophysics Data System (ADS)

In the present study, a new ligand is prepared by condensation of hydralazine (1-Hydralazinophthalazine) with 2-butanon-3-oxime. The acid-base equilibria of the schiff-base and the complex formation equilibria with the metal ions as Cu(II), Ni(II), Co(II), Cd(II), Mn(II) and Zn(II) are investigated potentiometrically. The stability constants of the complexes are determined and the concentration distribution diagrams of the complexes are evaluated. The effect of metal ion properties as atomic number, ionic radius, electronegativity and ionization potential are investigated. The isolated solid complexes are characterized by conventional chemical and physical methods. The potential coordination sites are assigned using the i.r. and 1H NMR spectra. The structures of the isolated solid complexes are proposed on the basis of the spectral and magnetic studies.

Shoukry, Azza A.; Shoukry, Mohamed M.

2008-08-01

213

The Search for Molecular-Based Magnets: Synthesis and Magnetic Properties of New Low-Dimensional Magnetic Materials.  

NASA Astrophysics Data System (ADS)

Magnetism has interested physicists for decades, but magnetism through molecules is quite recent. One of the active areas of molecular magnetism is the design of new materials with unusual, but predictable magnetic properties. We show how simple orbital considerations permit the description of unpaired electrons in molecular complexes, allow us to foresee their interactions through molecular bridges, and to obtain molecular-based magnetic systems. The synthesis, structure and magnetic properties of linear chain 4-cyanopyridine complexes: (Cu(4-CNpy) _4H_2O) (ClO _4)_2, Cu(4-CNpy) _2Br_2 and M(4-CNpy) _2 Cl_2 (M = Cu, Ni, Co, Fe and Mn) are reported. All compounds in the 4-CNpy series crystallize in the monoclinic system. Crystallographic data for { (Cu(4-CNpy) _4H_2O) (ClO _4)_2})n Space Group P2 _1/c with a = 13.225(3) A, b = 10.567(2) A, c = 20.522(3) A; beta = 99.71(2) ^circ; V = 2826.7(9) A ^3; Z = 4, D_{rm cal} = 1.640Mg/m^3; mu = 3.430 mm^{ -1}. The compound contains planar CuL _4 units with the ligands bonded to copper ions through the ring nitrogen. These units are weakly linked into chains through semicoordinate bonds between the nitrile nitrogen and an adjacent copper ion via the axial sites. The magnetic data shows no interactions down to 2.0 K. Crystallographic data for (Cu(4-CNpy) _2Cl_2) n: Space Group P2_1/n with a = 3.779(2) A, b = 25.711(12) A, c = 7.104(4) A; beta = 95.98(4)^circ; V = 686.5(4) A^3; Z = 2, D_{ rm cal} = 1.658 Mg/m^3 ; mu = 25.177 mm^ {-1}. Crystallographic data for (Mn(4 -CNpy)_2Cl_2) n: Space Group P2_{rm 1} /c with a = 3.700(2) A, b = 7.198(2) A, c = 26.520(5) A; beta = 92.13(4)^ circ; V = 705.8(4) A^3; Z = 2, D_{rm cal} = 1.572 Mg/m^3; mu = 1.303 mm^{-1}. Both compounds have similar structure, consisting of chains of metal ions bibridged by chlorides with the 4-CNpy ligands coordinated to the metal ions in the axial sites through the pyridine nitrogens. Infrared spectra and powder X-ray diffraction patterns indicate that the remaining compounds form an isostructural series. However, the different space group indicate the the chains pack together in different patterns. Antiferromagnetic exchange (Cu,Mn) or ferromagnetic exchange (Ni,Co,Fe) exists within the chains and antiferromagnetic interactions between the chains are observed. The copper data have been fit to the model of an S = 1/2 Heisenberg antiferromagnetic linear chain with an exchange constant of J/k = -13.7(2) K. The nickel data have been fit to the model of an S = 1 ferromagnetic Heisenberg linear chain with an exchange constant J/k = +4.8(2) K. The cobalt data have been fit to the model of an S = 1/2 ferromagnetic Ising linear chain with an exchange constant J/k = +6.6(2) K. The iron data have not been successfully to fit to any model. The manganese data have been fit to an S = 5n antiferromagnetic Heisenberg linear chain model with an exchange constant J/k = -0.57(1) K. The Ni, Co and Fe compounds order antiferromagnetically at 7.2(2) K, 2.1(2) K, and 4.6(2) K respectively. (Abstract shortened by UMI.).

Zhang, Wanru

1995-01-01

214

QSPR Prediction of the Stability Constants of Gadolinium(III) Complexes for Magnetic Resonance Imaging.  

PubMed

Gadolinium(III) complexes constitute the largest class of compounds used as contrast agents for Magnetic Resonance Imaging (MRI). A quantitative structure-property relationship (QSPR) machine-learning based method is applied to predict the thermodynamic stability constants of these complexes (log KGdL), a property commonly associated with the toxicity of such organometallic pharmaceuticals. In this approach, the log KGdL value of each complex is predicted by a graph machine, a combination of parametrized functions that encodes the 2D structure of the ligand. The efficiency of the predictive model is estimated on an independent test set; in addition, the method is shown to be effective (i) for estimating the stability constants of uncharacterized, newly synthesized polyamino-polycarboxylic compounds and (ii) for providing independent log KGdL estimations for complexants for which conflicting or questionable experimental data were reported. The exhaustive database of log KGdL values for 158 complexants, reported for potential application as contrast agents for MRI and used in the present study, is available in the Supporting Information (122 primary literature sources). PMID:25181704

Dioury, Fabienne; Duprat, Arthur; Dreyfus, Gérard; Ferroud, Clotilde; Cossy, Janine

2014-10-27

215

Gd doped Au nanoclusters: Molecular magnets with novel properties  

NASA Astrophysics Data System (ADS)

The structural, magnetic, and optical properties of subnanometer AuN and AuN-1Gd1 gas phase clusters (N = 2 to 8) are systematically investigated in the framework of (time-dependent) density functional theory, using the B3LYP hybrid exchange correlation functional. The size dependent evolution of the gap between the highest occupied and lowest unoccupied molecular orbitals, the magnetism, and the absorption spectra are studied. The simultaneous appearance of large magnetic moments, significant band gaps, and plasmon resonances in the visible spectral region leads to novel multi-functional nanomaterials for applications in drug delivery, magnetic resonance imaging, and photo-responsive agents.

Mokkath, Junais Habeeb; Schwingenschlögl, Udo

2014-01-01

216

Synthesis and Properties of Ortho-Nitro-Fe Complex  

SciTech Connect

Ortho-Nitro-Fe complex (Transition metal complex) has synthesized by chemical route method and properties of made complex has characterized by X-Ray diffraction (XRD), Moessbauer spectroscopy, Fourier transformation infra-red spectroscopy (FTIR) and X-Ray photoelectron spectroscopy (XPS). XRD analysis shows that sample is crystalline in nature and having particle size in the range of few nano meters. Moessbauer spectroscopy at room temperature shows the oxidation state of Iron (central metal ion) after complaxasion. FTIR spectra of the complex confirms the coordination of metal ion with ligand.

Mishra, A.; Mishra, Niyati; Sharma, R.; Jain, G.; Ninama, S.; Awate, R. [School of Physics, Devi Ahilya University, Khandwa Road, Indore, 45200 (India)

2011-07-15

217

Magnetic resonance for downhole complex-lithology earth formation evaluation  

NASA Astrophysics Data System (ADS)

Many petroleum-bearing reservoirs are known as complex-lithology, complex-mineralogy earth formations where the existing nuclear magnetic resonance (NMR) analysis models require modification and extension to work properly. This paper discusses the effects of mineralogy variation in complex-lithology formation rocks that will cause NMR response variations. In particular, the existence of iron-rich authigenic clays and the nonquartz grains in siliciclastics affect the surface relaxivity and the internal field inhomogeneity. Using a simplified pore-lining clay model, we estimated that the magnitude of the internal gradient in siliciclastics is comparable with or greater than that of the instrument-generated field gradient common to the currently used NMR logging tools. To account for these effects for reservoir fluid identification and quantification from NMR data, an inversion model is created, which includes the mean susceptibility of the grain minerals, the correlation between pore size and the relaxation time of the wetting-phase fluid in the pores and the geometric restriction to the fluid molecular diffusion.

Chen, Songhua; Li, Lilong; Zhang, Gigi; Chen, Jason

2011-08-01

218

COMPLEXATION IN ION EXCHANGER PHASE. PROPERTIES AND APPLICATION OF ION EXCHANGER COMPLEXES  

Microsoft Academic Search

This paper reviews the properties of complex forming ion exchangers (CFIE) and those of the ion exchanger complexes (IEC) with transition metal ions. It is mainly dedicated to the development of a novel approach in characterizing IEC which is based on the consideration of CFIE as three-dimensional polymeric ligands. The approach is illustrated by the results obtained by studying the

Valentina D. Kopylova

1998-01-01

219

Magnetic properties of ErN films  

NASA Astrophysics Data System (ADS)

We report a magnetization study of stoichiometric ErN nanocrystalline films grown on Si and protected by a GaN passivating layer. According to the temperature dependence of the resistivity the films are heavily doped semiconductors. Above 100 K the magnetization data fit well to a Curie-Weiss behavior with a moment expected within the free-ion ErJ={15}/{2} multiplet. Below 50 K the Curie-Weiss plot steepens to an effective moment corresponding to that in the crystal-field determined quartet ground state, and develops a clear paramagnetic Curie-Weiss temperature of about 4.5 K. Zero-field- and field-cooled magnetization curves and the AC susceptibility firmly establish a ferromagnetic ground state within that multiplet below a Curie temperature of 6.3±0.7 K. Due to the (1 1 1) texture of the film the comparison between the magnetization behavior, when the field is applied parallel and perpendicular to the film plane, gives new information about the magnetic structure. An arrangement of the moments according to the model derived from neutron diffraction for bulk HoN is strongly suggested.

Meyer, C.; Ruck, B. J.; Preston, A. R. H.; Granville, S.; Williams, G. V. M.; Trodahl, H. J.

2010-07-01

220

Magnetic properties of feroxyhyte (?-FeOOH)  

NASA Astrophysics Data System (ADS)

Magnetization curves and high-field Mössbauer spectra are used to deduce a model for the magnetic order in synthetic samples of ?-FeOOH (feroxyhyte), which takes account of the changes in magnetization when the samples are heated at 105 °C. Feroxyhyte is essentially a planar antiferromagnet with the net sublattice moments aligned parallel or antiparallel to c. Each particle acquires a net moment due to the very small number of layers along the c-direction, and the presence of surface steps causing the formation of ferrimagnetic domains with an odd number of layers. There is some spin canting which is related to the crystallinity of the sample. The decrease in magnetization following heating is mainly due to an increase in the extent of antiferromagnetic coupling between the closely packed ferrimagnetic particles, but changes in the spin canting within the bulk may also contribute. A typical, rather well crystallized specimen has magnetization ?=14 JT-1 kg-1 and Curie temperature T c=455 K.

Koch, C. Bender; Oxborrow, C. A.; Mørup, S.; Madsen, M. B.; Quinn, A. J.; Coey, J. M. D.

1995-07-01

221

Properties of magnetic double perovskites, silicide intermetallics and molybdenum-doped vanadium dioxide  

NASA Astrophysics Data System (ADS)

Chemists and condensed matter physicists alike have long searched for compounds that can shed light on electronic behavior in solids. Electronic behavior is usually assessed by two straightforward ways: conductivity and magnetism. The interactions that determine magnetic states give clues as to the lattice contribution and the atomic orbital interactions. This thesis investigates three systems for their electronic, magnetic, and structural properties: firstly, three double perovskites with very similar structures but different magnetic properties; secondly, a family of compounds with a cubic structure that theoretically should superconduct but doesn't; and lastly, the effects of molybdenum on the structure, magnetic, and electronic properties of VO2. Two new compounds, La2NiVO6 and La2CoVO 6 were synthesized along with the previously studied La2CoTiO 6. While all three compounds have the double perovskite structure, they exhibit very different magnetic properties. Only La2CoTiO 6 was found to have an ordered magnetic structure, the result of the transition metals ordering. The other two compounds had antiferromagnetic interactions, but with Ni and V mixed on a site and Co and V mixed on a site, neither exhibited long-range magnetic ordering. From theory, M6Ni16Si7 (M=Mg, Sc, Ti, Nb, or Ta), should be superconducting. These five compounds were synthesized, and their magnetic and electronic properties were measured with surprisingly consistent magnetic behavior over the wide range of electron counts. Measurements revealed no superconductivity, contrary to expectations. VO2 has a rather unique metal-insulator transition that occurs just above room temperature, which has been studied for decades. The insulator phase of VO2 contains V-V dimers and little magnetic activity is expected. By adding Mo, local magnetic states are created by disrupting these V-V dimers. For every Mo4+ added, an equal number of V 4+ ions displayed a magnetic moment, indicating the breaking up of V-V pairs. Doping also results in an increase in the density of states coinciding with a decrease in the number of magnetic moments on the lattice. These results suggest that chemical manipulation of simple systems, like VO2, provide an excellent framework for the development and testing of modern ideas about complex electronic matter and state-of-the-art theoretical treatments of correlated electron systems.

Holman, Katherine Leigh

222

Probing magnetic interactions in columnar phases of a paramagnetic gold dithiolene complex  

E-print Network

Probing magnetic interactions in columnar phases of a paramagnetic gold dithiolene complex Romain radical gold dithiolene complex exhibits a hexagonal columnar mesophase, as confirmed by optical in such a complex was analyzed by EPR. Temperature dependent magnetization measurements reveal that the global

Paris-Sud XI, Université de

223

Magnetic properties of rare-earth metallofullerenes  

SciTech Connect

Bulk amounts of La C[sub 82] and Gd C[sub 82] have been isolated in pure form from various hollow fullerenes. Magnetization data for these powder samples, an isolated La C[sub 82] isomer and a Gd C[sub 82] isomer, have been obtained employing a SQUID magnetometer at temperatures ranging from 3 to 300 K. For La C[sub 82] the inverse susceptibility as a function of temperature follows a Curie-Weiss law. The effective magnetic moment per La C[sub 82] is 0.38 [mu][sub B]. For Gd C[sub 32] the magnetization data fall on a universal curve which is fitted to a Brillouin function in correspondence with the Gd[sup 3+] free ion ground state values of J = 3.38 and g = 2. 33 refs., 6 figs.

Funasaka, Hideyuki; Sugiyama, Kenji; Yamamoto, Kazunori; Takahashi, Takeshi (Power Reactor and Nuclear Fuel Development Corp., Tokai (Japan))

1995-02-16

224

Observing and quantifying the solar wind signature of the magnetically complex corona.  

NASA Astrophysics Data System (ADS)

The solar wind exhibits fluctuations over a broad range of timescales characteristic of magnetohydrodynamic (MHD) turbulence evolving in the presence of structures of coronal origin. In- situ spacecraft observations of plasma parameters are at minute (or below) resolution for intervals spanning the solar cycle and provide a large number of samples for statistical studies. The magnetic field power spectrum typically has two characteristic components, an inertial range of turbulence over several orders of magnitude with approximately Kolmogorov power law and at lower frequencies, an approximately '1/f' energy containing range believed to be of direct coronal origin. We focus on the behaviour of in- situ observations of fluctuations in the inner heliosphere as a function of solar cycle and solar wind speed; that is, with respect to coronal structure and dynamics. We employ a recently developed technique that sensitively distinguishes between fractal and multifractal scaling in the timeseries. Our working hypothesis is that since the latter can be characteristic of local MHD turbulence, the former maps more directly to features of coronal origin. We find a strong correlation between the scaling properties of magnetic energy density fluctuations and the magnetic complexity of the coronal magnetic fields. At solar maximum in the ecliptic, where the in- situ observations can be dominated by slow solar wind, the magnetic energy density as seen by WIND and ACE shows a fractal signature, whereas at minimum it is multifractal. This is corroborated by ULLYSES polar observations at solar minimum in quiet, fast solar wind where again, multifractal scaling is found. This high magnetic complexity in the corona corresponds to fractal, rather than multifractal scaling in magnetic energy density; remarkably, this fractal signature dominates the full dynamic range of observations, extending across timescales typically identified with both the '1/f' and 'inertial range'. The correlation of behaviour of other bulk plasma parameters observed in- situ with the magnetic complexity of the coronal will also be discussed. Since we are able to quantify scaling exponents, our results provide constraints on models for the solar wind. In particular, the fractal signature which we discuss here can be captured by a nonlinear Fokker Planck model, with the prospect of a quantitative mapping back to the corona.

Hnat, B.; Chapman, S. C.; Kiyani, K. H.; Nicol, R. M.

2008-12-01

225

Vacuum properties of sintered SmCo/sub 5/ magnets  

SciTech Connect

There are many desirable applications of powerful, rare-earth permanent magnets made of sintered SmCo/sub 5/ material within vacuum systems. One application is the use of large numbers of SmCo/sub 5/ magnets to provide the undulating magnetic field in a free-electron-laser wiggler structure. Tests were conducted at Los Alamos to determine the suitability of SmCo/sub 5/ magnets in a vacuum environment of approx. 10/sup -6/ torr. The vacuum performances of the wiggler system, with and without the SmCo/sub 5/ magnets (having approx. 11% of the total surface area) installed, were essentially identical. These tests indicate that SmCo/sub 5/ magnets have good vacuum properties and are suitable for use in many vacuum systems.

Warren, R.W.; DePaula, R.F.; Hansborough, L.D.

1981-12-01

226

Magnetization reversal in amorphous gadolinium-cobalt films with a radial gradient of magnetic properties  

Microsoft Academic Search

The integral characteristics of magnetization switching in amorphous gadolinium-cobalt films with perpendicular anisotropy\\u000a are studied by visualizing the domain structure and measuring magnetooptic hysteresis loops. The films have a radial gradient\\u000a of magnetic properties that is due to a spatially nonuniform thermal field. Magnetization switching in those film areas where\\u000a the domain wall motion depends only on the coercive force

V. E. Ivanov; G. S. Kandaurova

2004-01-01

227

Magnetic properties of a magnetic impurity in a strongly correlated electronic system  

Microsoft Academic Search

With use of a quantum Monte Carlo method, we investigate the magnetic properties of a substitutional magnetic impurity in a strongly correlated electronic system, i.e., the Wolff model with an on-site repulsive interaction between conduction electrons. It is found that the magnetic susceptibility at the impurity-site decreases at low temperatures with increase in the interaction strength. Furthermore, dependence of the

S. Yunoki; Y. Mizuno; S. Maekawa

1997-01-01

228

Repetitive transcranial magnetic stimulation to SMA worsens complex movements in Parkinson's disease  

E-print Network

Repetitive transcranial magnetic stimulation to SMA worsens complex movements in Parkinson the therapeutic potential of repetitive transcranial magnetic stimulation (rTMS) for Parkinson's disease (PD analysis, timed motor performance tests, United Parkinson's Disease Rating Scale (UPDRS), patient self

Pullman, Seth L.

229

Magnetic Properties of Some Divalent Europium Compounds  

Microsoft Academic Search

The compounds of divalent europium form an attractive series for magnetic investigations because the magnetic ions are in S states and the crystal structures are generally simple. Moreover, true ferromagnetism, which is quite unusual in compounds, has been observed in EuO by Matthias, Bozorth, and Van Vleck.We have prepared samples of EuS, EuSe, EuTe, EuCO3, EuTiO3, EuZrO3, EuSO4, and EuCl2,

T. R. McGuire; B. E. Argyle; M. W. Shafer; J. S. Smart

1963-01-01

230

Magnetic properties of a metal-organic network Fe,,N3...2,,4,4 -bpy... Tan Yuen and C. L. Lin  

E-print Network

Magnetic properties of a metal-organic network Fe,,N3...2,,4,4 -bpy... Tan Yuen and C. L. Lin of Chemistry, Rutgers University, Camden, New Jersey 08102 The results of magnetic susceptibility, isothermal magnetization, and heat capacity measurements on a newly discovered iron complex with mixed ligands Fe(N3

Li, Jing

231

Structural and photophysical properties of rare-earth complexes encapsulated into surface modified mesoporous silica nanoparticles.  

PubMed

The encapsulation of [Eu(dbm)3phen] into functionalized mesoporous silica nanoparticles (MSN) has been carried out to study the effect of chemical environments on the photoluminescence properties of the rare-earth complex. Surface functionalization was achieved by the reaction of the silanol groups on the surface of mesoporous silica with different organosilylating agents such as (3-aminopropyl)-triethoxysilane (APTES), (3-mercaptopropyl)-trimethoxysilane (MPTMS), and ethoxytrimethylsilane (ETMS). A change in the luminescence properties of the Eu(dbm)3phen complex has been observed on its encapsulation into surface modified mesoporous silica nanoparticles. The modification of photophysical properties is attributed to the interaction of Eu(dbm)3phen with the different chemical environments in the functionalized mesoporous silica nanoparticles (MSN). The luminescence properties of the rare-earth complex in surface-modified MSN increase in the order MSN < MSN-ETMS < MSN-MPTMS < MSN-APTES. The Eu(dbm)3phen complex encapsulated in the functionalized mesoporous silica nanoparticles shows an enhanced luminescence and an increased lifetime compared to the pure rare-earth complex in the solid state and that in unmodified MSN. This implies that some interactions of the lanthanide complexes take place during their incorporation process into the organically modified mesoporous silica nanoparticles. The organically modified mesoporous silica nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR) and N2 adsorption desorption measurements. The luminescence properties of the encapsulated Eu(dbm)3phen were studied in detail. Moreover, the effect of functionalized MSNs on the structural behaviour of the Eu(dbm)3phen was investigated by solid state nuclear magnetic resonance (SSNMR) techniques using an analogous diamagnetic model complex, Y(dbm)3phen, encapsulated into functionalized MSNs. These studies indicate that the encapsulated rare-earth complex shows some interactions with the functional groups anchored on the surface of MSNs. PMID:24874265

Malba, Chandrashekhar; Sudhakaran, Umayal P; Borsacchi, Silvia; Geppi, Marco; Enrichi, Francesco; Natile, Marta Maria; Armelao, Lidia; Finotto, Tiziano; Marin, Riccardo; Riello, Pietro; Benedetti, Alvise

2014-10-14

232

Magnetic Properties of Radiation Damage in Pu  

SciTech Connect

First, we review earlier studies reporting possible magnetic characteristics for radiation defects in Pu. We then report, for {alpha}-Pu, two studies of the excess magnetic susceptibility (EMS) due to radiation damage, as a function of time and temperature. We have observed several annealing stages associated with the EMS of the accumulated self-damage and we report that annealing begins at {approx}31K, while below that temperature the displacement damage from self-irradiation of the Pu alpha particle emission and the U recoil are immobile. A detailed investigation was made of this EMS well below the first annealing stage as a function of temperature (2K < T < 15K) and time in a magnetic field of 2T. A linear increase in magnetic susceptibility is seen as a function of time for all isotherms. The excess susceptibility per alpha decay, determined from a linear fit of the slope of the time dependent EMS, is reasonably described with a Curie-Weiss law exhibiting a small negative Weiss temperature. We conclude by describing some future experiments in light of the present results.

McCall, S; Fluss, M J; Chung, B W; McElfresh, M; Chapline, G; Jackson, D

2004-10-27

233

Preparation and Structural Properties of InIII-H Complexes  

PubMed Central

The use of the tripodal ligands tris[(N'-tert-butylureaylato)-N-ethyl]aminato ([H3buea]3?) and the sulfonamide-based N,N',N"-[2,2',2"-nitrilotris(ethane-2,1-diyl)]tris(2,4,6-trimethylbenzene-sulfonamidato) ([MST]3?) has led to the synthesis of two structurally distinct In(III)–OH complexes. The first example of a five-coordinate indium(III) complex with a terminal hydroxide ligand, K[InIIIH3buea(OH)], was prepared by addition of In(OAc)3 and water to a deprotonated solution of H6buea. X-ray diffraction analysis, as well as FTIR and 1H NMR spectroscopic methods, provided evidence for the formation of a monomeric In(III)–OH complex. The complex contains an intramolecular hydrogen bonding (H-bonding) network involving the In(III)–OH unit and [H3buea]3? ligand, which aided in isolation of the complex. Isotope labeling studies verified the source of the hydroxo ligand as water. Treatment of the [InIIIMST] complex with a mixture of 15-crown-5 ether and NaOH led to isolation of the complex [15-crown-5?NaI-(?-OH)-InIIIMST], whose solid-state structure was confirmed using X-ray diffraction methods. Nuclear magnetic resonance studies on this complex suggest it retains its heterobimetallic structure in solution. PMID:25309019

Sickerman, Nathaniel S.; Henry, Renee M.; Ziller, Joseph W.

2013-01-01

234

Luminescent Cyclometalated Platinum and Palladium Complexes with Novel Photophysical Properties  

NASA Astrophysics Data System (ADS)

Organic light emitting diodes (OLEDs) is a rapidly emerging technology based on organic thin film semiconductors. Recently, there has been substantial investment in their use in displays. In less than a decade, OLEDs have grown from a promising academic curiosity into a multi-billion dollar global industry. At the heart of an OLED are emissive molecules that generate light in response to electrical stimulation. Ideal emitters are efficient, compatible with existing materials, long lived, and produce light predominantly at useful wavelengths. Developing an understanding of the photophysical processes that dictate the luminescent properties of emissive materials is vital to their continued development. Chapter 1 and Chapter 2 provide an introduction to the topics presented and the laboratory methods used to explore them. Chapter 3 discusses a series of tridentate platinum complexes. A synthetic method utilizing microwave irradiation was explored, as well as a study of the effects ligand structure had on the excited state properties. Results and techniques developed in this endeavor were used as a foundation for the work undertaken in later chapters. Chapter 4 introduces a series of tetradentate platinum complexes that share a phenoxy-pyridyl (popy) motif. The new molecular design improved efficiency through increased rigidity and modification of the excited state properties. This class of platinum complexes were markedly more efficient than those presented in Chapter 3, and devices employing a green emitting complex of the series achieved nearly 100% electron-to-photon conversion efficiency in an OLED device. Chapter 5 adapts the ligand structure developed in Chapter 4 to palladium. The resulting complexes exceed reported efficiencies of palladium complexes by an order of magnitude. This chapter also provides the first report of a palladium complex as an emitter in an OLED device. Chapter 6 discusses the continuation of development efforts to include carbazolyl components in the ligand. These complexes possess interesting luminescent properties including ultra-narrow emission and metal assisted delayed fluorescence (MADF) emission.

Turner, Eric

235

Stimuli responsive hybrid magnets: tuning the photoinduced spin-crossover in Fe(III) complexes inserted into layered magnets.  

PubMed

The insertion of a [Fe(sal2-trien)](+) complex cation into a 2D oxalate network in the presence of different solvents results in a family of hybrid magnets with coexistence of magnetic ordering and photoinduced spin-crossover (LIESST effect) in compounds [Fe(III)(sal2-trien)][Mn(II)Cr(III)(ox)3]·CHCl3 (1·CHCl3), [Fe(III)(sal2-trien)][Mn(II)Cr(III)(ox)3]·CHBr3 (1·CHBr3), and [Fe(III)(sal2-trien)][Mn(II)Cr(III)(ox)3]·CH2Br2 (1·CH2Br2). The three compounds crystallize in a 2D honeycomb anionic layer formed by Mn(II) and Cr(III) ions linked through oxalate ligands and a layer of [Fe(sal2-trien)](+) complexes and solvent molecules (CHCl3, CHBr3, or CH2Br2) intercalated between the 2D oxalate network. The magnetic properties and Mössbauer spectroscopy indicate that they undergo long-range ferromagnetic ordering at 5.6 K and a spin crossover of the intercalated [Fe(sal2-trien)](+) complexes at different temperatures T1/2. The three compounds present a LIESST effect with a relaxation temperature TLIESST inversely proportional to T1/2. The isostructural paramagnetic compound, [Fe(III)(sal2-trien)][Zn(II)Cr(III)(ox)3]·CH2Cl2 (2·CH2Cl2) was also prepared. This compound presents a partial spin crossover of the inserted Fe(III) complex as well as a LIESST effect. Finally, spectroscopic characterization of the Fe(III) doped compound [Ga0.99Fe0.01(sal2trien)][Mn(II)Cr(III)(ox)3]·CH2Cl2 (3·CH2Cl2) shows a gradual and complete thermal spin crossover and a LIESST effect on the isolated Fe(III) complexes. This result confirms that cooperativity is not a necessary condition to observe the LIESST effect in an Fe(III) compound. PMID:23676008

Clemente-León, Miguel; Coronado, Eugenio; López-Jordà, Maurici; Waerenborgh, João C; Desplanches, Cédric; Wang, Hongfeng; Létard, Jean-François; Hauser, Andreas; Tissot, Antoine

2013-06-12

236

Petrophysical Properties (Density and Magnetization) of Rocks from the Suhbaatar-Ulaanbaatar-Dalandzadgad Geophysical Profile in Mongolia and Their Implications  

PubMed Central

Petrophysical properties of 585 rock samples from the Suhbaatar-Ulaanbaatar-Dalandzadgad geophysical profile in Mongolia are presented. Based on the rock classifications and tectonic units, petrophysical parameters (bulk density, magnetic susceptibility, intensity of natural remanent magnetization, and Köenigsberger ratio) of these rocks are summarized. Results indicate that (1) significant density contrast of different rocks would result in variable gravity anomalies along the profile; (2) magnetic susceptibility and natural remanent magnetization of all rocks are variable, covering 5-6 orders of magnitude, which would make a variable induced magnetization and further links to complex magnetic anomalies in ground surface; (3) the distribution of rocks with different lithologies controls the pattern of lithospheric magnetic anomaly along the profile. The petrophysical database thus provides not only one of the keys to understand the geological history and structure of the profile, but also essential information for analysis and interpretation of the geophysical (e.g., magnetic and gravity) survey data. PMID:24324382

Gao, Jintian; Gu, Zuowen; Dagva, Baatarkhuu; Tserenpil, Batsaikhan

2013-01-01

237

Reconstructing topological properties of complex networks using the fitness model  

E-print Network

A major problem in the study of complex socioeconomic systems is represented by privacy issues$-$that can put severe limitations on the amount of accessible information, forcing to build models on the basis of incomplete knowledge. In this paper we investigate a novel method to reconstruct global topological properties of a complex network starting from limited information. This method uses the knowledge of an intrinsic property of the nodes (indicated as fitness), and the number of connections of only a limited subset of nodes, in order to generate an ensemble of exponential random graphs that are representative of the real systems and that can be used to estimate its topological properties. Here we focus in particular on reconstructing the most basic properties that are commonly used to describe a network: density of links, assortativity, clustering. We test the method on both benchmark synthetic networks and real economic and financial systems, finding a remarkable robustness with respect to the number of ...

Cimini, Giulio; Musmeci, Nicolò; Puliga, Michelangelo; Gabrielli, Andrea; Garlaschelli, Diego; Battiston, Stefano; Caldarelli, Guido

2014-01-01

238

3D Magnetic Reluctivity Tensor of Soft Magnetic Composite Material  

Microsoft Academic Search

Soft magnetic composite (SMC) materials are particularly suitable for construction of electrical machines with complex structure and 3D magnetic flux. For design and analysis of such 3D flux machines, 3D magnetic properties of the magnetic materials should be properly determined, modeled and applied for calculating the magnetic field distribution, parameters and performance. This paper presents the 3D magnetic property measurement

Y. G. Guo; J. G. Zhu; Z. W. Lin; J. J. Zhong; H. Y. Lu; S. H. Wang

2006-01-01

239

Basic magnetic properties of bituminous coal  

USGS Publications Warehouse

Magnetic susceptibility and other static magnetic parameters have been measured on a number of bituminous coals from various locations in the United States. The paramagnetic Curie constant correlates negatively with carbon concentration on a moisture-free basis. The major contribution to the total paramagnetism comes from the mineral matter rather than from free radicals or broken bonds. Analysis of the data indicates that the specific paramagnetism is generally lower in the mineral matter found in high-ash compared to low-ash coal. A substantial number of the coal specimens tested also had a ferromagnetic susceptibility which appeared to be associated with magnetite. Magnetite and ??-iron spherules, possibly of meteoritic or volcanic origin, were found in several specimens. ?? 1979.

Alexander, C.C.; Thorpe, A.N.; Senftle, F.E.

1979-01-01

240

Magnetic properties of novel epitaxial films  

SciTech Connect

The surface magneto-optic Kerr effect (SMOKE) is used to explore the magnetism of ultra-thin Fe Films extending into the monolayer regime. Both bcc ..cap alpha..-Fe and fcc ..gamma..-Fe single-crystalline, multilayer films are prepared on the bulk-terminated (1 x 1) structures of Au(100) and Cu(100), respectively. The characterizations of epitaxy and growth mode are performed using low energy electron diffraction and Auger electron spectroscopy. Monolayer-range Fe/Au(100) is ferromagnetic with a lower Curie temperature than bulk ..cap alpha..-Fe. The controversial ..gamma..-Fe/Cu(100) system exhibits a striking, metastable, surface magnetic phase at temperatures above room temperature, but does not exhibit bulk ferromagnetism.

Bader, S.D.; Moog, E.R.

1986-09-01

241

Synthesis and magnetic properties of a novel ferrite organogel  

NASA Astrophysics Data System (ADS)

A novel magnetic organogel that can be considered a precursor example of a magnetoresponsive gel is reported. The gel is formed by the bridging of ferrite containing anionic bis(2-ethlhexyl) sodium sulfosuccinate reverse micelles with 2,6-dihydroxynaphthalene (2,6-DHN). The addition of 2,6-DHN leads to a room temperature quotes "freezing in" of the liquid solution to a clear organogel. Ferrite particles in the size range 10-15 nm are doped into the gel network and are thus suspended in the optically clear gel media. The magnetic properties of the gel were measured using a superconducting quantum interference device magnetometer. The results reveal that the gel exhibits superparamagnetic behavior with a blocking temperature of 6 K (at an applied field of 1000 G), and a coercivity of 850 G at 2 K. The ferrites introduced into the gel serve the function of magnetic "seeds" via which magnetic properties are acquired by the gel.

Li, Sichu; John, Vijay T.; Irvin, Glen C.; Rachakonda, Suguna H.; McPherson, Gary L.; O'Connor, Charles J.

1999-04-01

242

Photometric properties of resolved and unresolved magnetic elements  

E-print Network

We investigate the photometric signature of magnetic flux tubes in the solar photosphere. We developed two dimensional, static numerical models of isolated and clustered magnetic flux tubes. We investigated the emergent intensity profiles at different lines-of-sight for various spatial resolutions and opacity models. We found that both geometric and photometric properties of bright magnetic features are determined not only by the physical properties of the tube and its surroundings, but also by the particularities of the observations, including the line/continuum formation height, the spatial resolution and the image analyses techniques applied. We show that some observational results presented in the literature can be interpreted by considering bright magnetic features to be clusters of smaller elements, rather than a monolithic flux tube.

Serena Criscuoli; Mark Rast

2008-12-09

243

Microstructure and magnetic properties of FINEMET nanowires  

NASA Astrophysics Data System (ADS)

FINEMET (Fe73.5Cu1Nb3Si13.5B9) glass-coated nanowires and submicron wires with metallic nucleus diameters (?m) between 100 and 500 nm and the glass coating thickness (tg) of 5 ?m are reported for the first time. The microstructure of annealed ultrathin glass-coated wires evolves into a nanocrystalline one (DO3 nanograins of 10-20 nm embedded into the residual amorphous matrix) after annealing at 550 °C and 600 °C for 60 min. Despite the similar size of the nanograins, the volume occupied by them relative to the total volume increases from 50%-53% after annealing at 550 °C to 63%-65% after annealing at 600 °C, due to the increase in their number. This is reflected in a more accurate manner in the domain wall velocity measurements than in variation of the magnetic characteristics such as M(H), relative magnetic permeability or switching field. The magnetically softest nanocrystalline phase is formed at larger values of annealing temperature (Ta) for thinner wires, since larger temperature is needed to grow a sufficient number of DO3 grains at distances below the exchange length among them.

Chiriac, H.; Corodeanu, S.; Óvári, T.-A.; Lupu, N.

2013-05-01

244

Measured iron-gallium alloy tensile properties under magnetic fields  

NASA Astrophysics Data System (ADS)

Tension testing is used to identify Galfenol material properties under low level DC magnetic bias fields. Dog bone shaped specimens of single crystal Fe100-xGax, where 17<=x<=33, underwent tensile testing along two crystalographic axis orientations, [110] and [100]. The material properties being investigated and calculated from measured quantities are: Young's modulus and Poisson's ratio. Data are presented that demonstrate the dependence of these material properties on applied magnetic field levels and provide a preliminary assessment of the trends in material properties for performance under varied operating conditions. The elastic properties of Fe-Ga alloys were observed to be increasingly anisotropic with rising Ga content for the stoichiometries examined. The largest elastic anisotropies were manifested in [110] Poisson's ratios of as low as -0.63 in one specimen. This negative Poisson's ratio creates a significant in-plane auxetic behavior that could be exploited in applications that capitalize on unique area effects produced under uniaxial loading.

Yoo, Jin-Hyeong; Flatau, Alison B.

2004-07-01

245

Assessment of DNA complexation onto polyelectrolyte-coated magnetic silica nanoparticles  

NASA Astrophysics Data System (ADS)

The polyelectrolyte-DNA complexation method to form magnetoplexes using silica-coated iron oxide magnetic nanoparticles as inorganic substrates is an attractive and promising process in view of the potential applications including magnetofection, DNA extraction and purification, and directed assembly of nanostructures. Herein, we present a systematic physico-chemical study that provides clear evidence of the type of interactions established, reflects the importance of the DNA length, the nanoparticle size and the ionic strength, and permits the identification of the parameters controlling both the stability and the type of magnetoplexes formed. This information can be used to develop targeted systems with properties optimized for the various proposed applications of magnetoplexes.The polyelectrolyte-DNA complexation method to form magnetoplexes using silica-coated iron oxide magnetic nanoparticles as inorganic substrates is an attractive and promising process in view of the potential applications including magnetofection, DNA extraction and purification, and directed assembly of nanostructures. Herein, we present a systematic physico-chemical study that provides clear evidence of the type of interactions established, reflects the importance of the DNA length, the nanoparticle size and the ionic strength, and permits the identification of the parameters controlling both the stability and the type of magnetoplexes formed. This information can be used to develop targeted systems with properties optimized for the various proposed applications of magnetoplexes. Electronic supplementary information (ESI) available: Experimental, description of ITC experiments, Fig. S1-S4, and Tables S1-S3. See DOI: 10.1039/c3nr34358h

Dávila-Ibáñez, Ana B.; Buurma, Niklaas J.; Salgueiriño, Verónica

2013-05-01

246

Aluminium complexes in methanol-water mixture as studied by 27Al NMR nuclear magnetic resonance.  

PubMed

(27)Al NMR spectroscopy can be used for study of coordination and solvation in both aqueous and non-aqueous solutions. Various octahedral and tetrahedral aluminium complexes have been proved to exist in solution by (1)H and (27)Al NMR spectroscopy. (27)Al nuclear magnetic resonance (NMR) spectroscopy also can be used to determine thermodynamic properties of complexes in the solution. The formation of [Al(OH)(4-n)(CH(3)OH)(n)]((n-1)+) (n=1, 2, 3 and 4) species through the reaction of aluminate anion with methanol has been investigated by (27)Al NMR spectroscopy. (27)Al NMR spectra reveal evidence for Al bound to one, two, three and four CH(3)OH, the production of aluminate species is affected by the MeOH/H(2)O. Results obtained from 2D EXSY experiments clearly confirm there are exchanges among the species. PMID:16455290

Samadi-Maybodi, Abdolraouf

2006-07-01

247

Magnetic properties of a mischmetal-cobalt alloy  

Microsoft Academic Search

The magnetic properties of a mischmetal-cobalt alloy are studied. A mischmetal-64% cobalt alloy was melted in induction furnace\\u000a under a protective atmosphere of argon. The melt was solidified in a magnetic field of 7 kOe, and cooled to a temperature\\u000a of 950° C and was thereafter quenched in water. Specimens of suitable dimensions were machined, heat-treated in the temperature\\u000a range

R A Tewari

1980-01-01

248

Magnetic Properties of Gd1-xThxFe3  

Microsoft Academic Search

The pseudo-binary solid solution system Gd1-xThxFe3 has been investigated with respect to magnetic properties. All members of the system exhibit the PuNi3-type structure. The magnetic behavior of materials in the composition range x = 0 to about x = .5 can be understood in terms of a collinear two-sublattice model in which the total gadolinium moment is alligned antiparallel to

J. E. Greedan

1972-01-01

249

Magnetic Properties of Gd1?xThxFe3  

Microsoft Academic Search

The pseudo-binary solid solution system Gd1?xThxFe3 has been investigated with respect to magnetic properties. All members of the system exhibit the PuNi3-type structure. The magnetic behavior of materials in the composition range x = 0 to about x = .5 can be understood in terms of a collinear two-sublattice model in which the total gadolinium moment is alligned antiparallel to

J. E. Greedan

1972-01-01

250

Nonlinear optical properties of the magnetized QED Vacuum  

E-print Network

New processes associated with the nonlinear optical properties of the electromagnetic vacuum, as predicted by quantum electrodynamics are described. We consider the presence of a static and a rotating magnetic field. The cases of harmonic generation and two different types of sideband cascades are considered. First order and second order effects with respect to the external magnetic field are discussed in detail. Possible experimental configurations using ultra-intense lasers are compared with the alternative use of cw lasers in stable optical cavities.

J. T. Mendonca

2007-02-08

251

Nonlinear optical properties of the magnetized QED Vacuum  

E-print Network

New processes associated with the nonlinear optical properties of the electromagnetic vacuum, as predicted by quantum electrodynamics are described. We consider the presence of a static and a rotating magnetic field. The cases of harmonic generation and two different types of sideband cascades are considered. First order and second order effects with respect to the external magnetic field are discussed in detail. Possible experimental configurations using ultra-intense lasers are compared with the alternative use of cw lasers in stable optical cavities.

Mendonça, J T

2007-01-01

252

Fe–FeO Nanocomposites: Preparation, Characterization and Magnetic Properties  

Microsoft Academic Search

\\u000a To date, nano-magnetic materials have gain great attention by the research community due to their importance for future applications.\\u000a A brief introduction of Fe–FeO nanocomposites in the form of particles and thin films is given in the first part of this chapter.\\u000a This includes definition, magnetic properties, preparation, structure and applications. Different preparation methods of Fe–FeO\\u000a are then introduced in

Jamshid Amighian; Morteza Mozaffari; Mehdi Gheisari

253

Magnetic properties of NdFeB-coated rubberwood composites  

NASA Astrophysics Data System (ADS)

Magnetic properties of composites prepared by coating lacquer containing neodymium iron boron (Nd-Fe-B) powders on rubberwood were characterized by vibrating sample magnetometry (VSM), magnetic moment measurements, and attraction tests with an iron-core solenoid. The Nd-Fe-B powders were recycled from electronic wastes by the ball-milling technique. Varying the milling time from 20 to 300 min, the magnetic squareness and the coercive field of the Nd-Fe-B powders were at the minimum when the powders were milled for 130 min. It followed that the coercive field of the magnetic wood composites was increased with the milling time increasing from 130 to 300 min. For the magnetic wood composites using Nd-Fe-B obtained from the same milling time, the magnetic squareness and the coercive field were rather insensitive to the variation of Nd-Fe-B concentration in coating lacquer from 0.43 to 1.00 g/cm3. By contrast, the magnetization and magnetic moment were increased with the Nd-Fe-B concentration increasing. Furthermore, the electrical current in the solenoid required for the attraction of the magnetic wood composites was exponentially reduced with the increase in the amount of Nd-Fe-B used in the coating.

Noodam, Jureeporn; Sirisathitkul, Chitnarong; Matan, Nirundorn; Rattanasakulthong, Watcharee; Jantaratana, Pongsakorn

2013-01-01

254

Tunable dynamic response of magnetic gels: impact of structural properties and magnetic fields  

E-print Network

Ferrogels and magnetic elastomers feature mechanical properties that can be reversibly tuned from outside through magnetic fields. Here we concentrate on the question how their dynamic response can be adjusted. The influence of three factors on the dynamic behavior is demonstrated using appropriate minimal models: first, the orientational memory imprinted into one class of the materials during their synthesis; second, the structural arrangement of the magnetic particles in the materials; and third, the strength of an external magnetic field. To illustrate the latter point, structural data are extracted from a real experimental sample and analyzed. Understanding how internal structural properties and external influences impact the dominant dynamical properties helps to design materials that optimize the requested behavior.

Mitsusuke Tarama; Peet Cremer; Dmitry Y. Borin; Stefan Odenbach; Hartmut Löwen; Andreas M. Menzel

2014-06-26

255

Tunable dynamic response of magnetic gels: Impact of structural properties and magnetic fields  

NASA Astrophysics Data System (ADS)

Ferrogels and magnetic elastomers feature mechanical properties that can be reversibly tuned from outside through magnetic fields. Here we concentrate on the question of how their dynamic response can be adjusted. The influence of three factors on the dynamic behavior is demonstrated using appropriate minimal models: first, the orientational memory imprinted into one class of the materials during their synthesis; second, the structural arrangement of the magnetic particles in the materials; and third, the strength of an external magnetic field. To illustrate the latter point, structural data are extracted from a real experimental sample and analyzed. Understanding how internal structural properties and external influences impact the dominant dynamical properties helps to design materials that optimize the requested behavior.

Tarama, Mitsusuke; Cremer, Peet; Borin, Dmitry Y.; Odenbach, Stefan; Löwen, Hartmut; Menzel, Andreas M.

2014-10-01

256

Growth, structure, morphology, and magnetic properties of Ni ferrite films  

NASA Astrophysics Data System (ADS)

The morphology, structure, and magnetic properties of nickel ferrite (NiFe2O4) films fabricated by radio frequency magnetron sputtering on Si(111) substrate have been investigated as functions of film thickness. Prepared films that have not undergone post-annealing show the better spinel crystal structure with increasing growth time. Meanwhile, the size of grain also increases, which induces the change of magnetic properties: saturation magnetization increased and coercivity increased at first and then decreased. Note that the sample of 10-nm thickness is the superparamagnetic property. Transmission electron microscopy displays that the film grew with a disorder structure at initial growth, then forms spinel crystal structure as its thickness increases, which is relative to lattice matching between substrate Si and NiFe2O4.

Dong, Chunhui; Wang, Gaoxue; Guo, Dangwei; Jiang, Changjun; Xue, Desheng

2013-04-01

257

Growth, structure, morphology, and magnetic properties of Ni ferrite films.  

PubMed

The morphology, structure, and magnetic properties of nickel ferrite (NiFe2O4) films fabricated by radio frequency magnetron sputtering on Si(111) substrate have been investigated as functions of film thickness. Prepared films that have not undergone post-annealing show the better spinel crystal structure with increasing growth time. Meanwhile, the size of grain also increases, which induces the change of magnetic properties: saturation magnetization increased and coercivity increased at first and then decreased. Note that the sample of 10-nm thickness is the superparamagnetic property. Transmission electron microscopy displays that the film grew with a disorder structure at initial growth, then forms spinel crystal structure as its thickness increases, which is relative to lattice matching between substrate Si and NiFe2O4. PMID:23622034

Dong, Chunhui; Wang, Gaoxue; Guo, Dangwei; Jiang, Changjun; Xue, Desheng

2013-01-01

258

Effects of Exsolution Lamellae on Magnetic Properties of Crustal Rocks and Contributions to Remanent Magnetic Anomalies  

NASA Astrophysics Data System (ADS)

Magnetic anomalies from crustal sources are measured over a wide range of scales and elevations, from near-surface to satellites. They reflect magnetic minerals in rocks, which respond to the changing planetary magnetic field. Anomalies are influenced by the geometry of the geological bodies, and magnetic properties of the minerals. Commonly, magnetism of continental crust has been described in terms of bulk ferrimagnetism of minerals, and much attributed to induced magnetization. Though remanent magnetization was crucial for dating the ocean floor, and is important in mineral exploration, its contribution to continental magnetic anomalies is commonly ignored. Over the last decade studying remanent anomalies in crustal rocks, we discovered a new type of remanence, 'lamellar magnetism'. This is due to layers of mixed Fe2+/Fe3+ valence at (001) contacts between exsolution lamellae and hosts of ilmenite and hematite. The mixed-valence contact layers are placed by chemistry between hematite Fe3+ layers and ilmenite Ti4+ layers, where they provide reduction of ionic charge imbalance. Placement requires that the uncompensated spin of contact layers on opposite sides of a lamella be in-phase magnetically. This produces a net ferrimagnetic moment per lamella of ~4 uB per formula unit, regardless of lamella thickness, thus net moment is greatest with the greatest density of magnetically in-phase fine lamellae created during slow cooling. We can show that in-phase magnetization of lamellae is greatly enhanced in foliated samples, where the statistical (001) plane is parallel to the Earth field at the time of exsolution. Strictly speaking, the resulting magnetization is a chemical remanence with very high stability. Lamellar magnetism is responsible for numerous remanent magnetic anomalies in continental rocks we present here. We highlight some bodies with NRMs > 20 A/m which are possible analogs for sources of remanent anomalies on Mars.

McEnroe, S. A.; Robinson, P.; Fabian, K.; Brown, L. L.; Harrison, R. J.

2011-12-01

259

Electrical properties of transition metal hydrogen complexes in silicon  

SciTech Connect

A summary is given on the electrical properties of transition-metal hydrogen complexes in silicon. Contrary to the general understanding, hydrogen leads not only to passivation of deep defect levels but also creates several new levels in the band gap due to electrically active transition-metal complexes. The author presents detailed data for Pt-H complexes and summarize briefly the results on the transition metals Ti, Co, Ni, Pd, and Ag. The introduction of hydrogen at room temperature by wet chemical etching, followed by specific annealing steps allows us to study the formation of the different complexes. In particular, depth profiles of the defect concentrations give an estimate of the number of hydrogen atoms involved in the complexes. Transition-metals binding up to four hydrogen atoms are identified.

Weber, J. [Max-Planck-Inst. fuer Festkoerperforschung, Stuttgart (Germany)

1998-12-31

260

Magnetic neutron spectroscopy of a spin-transition Mn3+ molecular complex  

NASA Astrophysics Data System (ADS)

We have investigated by inelastic neutron scattering (INS), neutron diffraction, and magnetometry the magnetic properties of the mononuclear complex [Mn3+(pyrol)3(tren)] in both high-spin (5E, HS, S =2) and low-spin (3T1, LS, S =1) states. The system presents a spin transition (ST) around 47 K with a small hysteresis width (TST,?=47.5 K and TST,?=46 K) characteristic of an efficient collective transition process. In the HS state, the INS spectrum at 56 K and zero magnetic field is accounted for by a zero-field splitting with D =-5.73(3) cm-1 and |E|=+0.47(2) cm-1 which may be the result of a dynamic Jahn-Teller effect reported in the literature. In the LS state, a single magnetic peak at 4.87 meV is observed, still at zero field. Despite the existence of an unquenched orbital moment (L =1) in the ground 3T1 state, we argue that it may be described by a genuine S =1 spin Hamiltonian owing to the existence of a strong trigonal distortion of the Mn3+ coordination octahedron. The observed peak corresponds to a transition ?M =+1 within the S =1 ground state split by a large single-ion anisotropy term D =+39.3 cm-1. A full spin-Hamiltonian model is proposed based on these first INS results obtained in a thermal ST molecular magnetic system.

Ridier, Karl; Petit, Sylvain; Gillon, Béatrice; Chaboussant, Grégory; Safin, Damir A.; Garcia, Yann

2014-09-01

261

Studying the magnetic properties of CoSi single crystals  

SciTech Connect

The magnetic properties of CoSi single crystals have been measured in a range of temperatures T = 5.5-450 K and magnetic field strengths H {<=} 11 kOe. A comparison of the results for crystals grown in various laboratories allowed the temperature dependence of magnetic susceptibility {chi}(T) = M(T)/H to be determined for a hypothetical 'ideal' (free of magnetic impurities and defects) CoSi crystal. The susceptibility of this ideal crystal in the entire temperature range exhibits a diamagnetic character. The {chi}(T) value significantly increases in absolute value with decreasing temperature and exhibits saturation at the lowest temperatures studied. For real CoSi crystals of four types, paramagnetic contributions to the susceptibility have been evaluated and nonlinear (with respect to the field) contributions to the magnetization have been separated and taken into account in the calculations of {chi}(T).

Narozhnyi, V. N., E-mail: narozhnyivn@gmail.com; Krasnorussky, V. N. [Russian Academy of Sciences, Vereshchagin Institute for High Pressure Physics (Russian Federation)

2013-05-15

262

Properties of hyperonic matter in strong magnetic fields  

E-print Network

We study the effects of strong magnetic fields on the properties of hyperonic matter. We employ the relativistic mean field theory, which is known to provide excellent descriptions of nuclear matter and finite nuclei. The two additional hidden-strangeness mesons, $\\sigma^{\\ast}$ and $\\phi$, are taken into account, and some reasonable hyperon potentials are used to constrain the meson-hyperon couplings, which reflect the recent developments in hypernuclear physics. It is found that the effects of strong magnetic fields become significant only for magnetic field strength $B>5 \\times 10^{18}$ G. The threshold densities of hyperons can be significantly altered by strong magnetic fields. The presence of hyperons makes the equation of state (EOS) softer than that in the case without hyperons, and the softening of the EOS becomes less pronounced with increasing magnetic field strength.

P. Yue; F. Yang; H. Shen

2009-02-21

263

Chiral Properties of Strong Interactions in a Magnetic Background  

E-print Network

We investigate the chiral properties of QCD in presence of a magnetic background field and in the low temperature regime, by lattice numerical simulations of N_f = 2 QCD. We adopt a standard staggered discretization, with a pion mass around 200 MeV, and explore a range of magnetic fields (180 MeV)^2 \\leq|e|B \\leq (700 MeV)^2, in which we study magnetic catalysis, i.e. the increase of chiral symmetry breaking induced by the background field. We determine the dependence of the chiral condensate on the external field, compare our results with existing model predictions and show that a substantial contribution to magnetic catalysis comes from the modified distribution of non-Abelian gauge fields, induced by the magnetic field via dynamical quark loop effects.

Massimo D'Elia; Francesco Negro

2011-03-10

264

Electronic and magnetic properties of MnAu nanoparticles  

NASA Astrophysics Data System (ADS)

Self-consistent ab initio calculations, based on DFT (Density Functional Theory) approach and using FLAPW (Full potential Linear Augmented Plane Wave) method, are performed to investigate both electronic and magnetic properties of the MnAu nanoparticles. Polarized spin is included in calculations within the framework of the antiferromagnetic. The Mn magnetic moments where considered to be along c axes. Obtained data from ab initio calculations are used as input for the high temperature series expansions (HTSEs) calculations to compute other magnetic parameters. The zero-field high temperature static susceptibility series of the magnetic moment (m) and nearest-neighbour Heisenberg and XY models on a MnAu nanoparticles is thoroughly analyzed by means of a power series coherent anomaly method (CAM) for different nanoparticles. The exchanges interactions between the magnetic atoms are obtained for MnAu nanoparticles.

Masrour, R.; Hlil, E. K.; Hamedoun, M.; Benyoussef, A.; Mounkachi, O.; El moussaoui, H.

2014-03-01

265

Magnetic properties of agricultural soil in the Pearl River Delta, South China - Spatial distribution and influencing factor analysis  

NASA Astrophysics Data System (ADS)

Environmental magnetism has been widely applied to soil science due to its speediness, non-destructiveness and cost-effectiveness. However, the magnetic investigation of agricultural soil, so closely related to human activity, is limited, most probably because of its complexity. Here we present a magnetic investigation of 301 agricultural soil samples collected from the Pearl River Delta (PRD, 112°E-115°E and 22°N-24°N), China. The results showed that both low and high coercivity magnetic minerals coexist in agricultural soil. The values of concentration-dependent parameters, low-field susceptibility (?lf), anhysteretic remanence magnetization susceptibility (?ARM), and saturation isothermal remanence magnetization (SIRM) were much higher in the PRD plain than in the surrounding areas. The S-ratio (S- 300) showed a similar spatial pattern to the aforementioned parameters. By contrast, frequency-dependent susceptibility (?fd%) and ?ARM/SIRM were higher in the surrounding hilly and mountainous areas than in the PRD plain. Natural and anthropogenic factors such as parent material, soil type and cultivation methods play important roles in determining agricultural soil magnetic properties. Magnetic minerals were coarser grained and overall indicated higher concentrations in soils from river alluvium and deposited materials. Soils which had suffered long-term water submergence have the lowest magnetic mineral concentration, a result consistent with previous studies. The magnetic properties of agricultural soils are strongly influenced by cultivation methods. Other human activities, such as industrial development and concomitant emitted pollutants, might have had an additional impact on the magnetic properties of agricultural soil.

Bian, Yong; Ouyang, Tingping; Zhu, Zhaoyu; Huang, Ningsheng; Wan, Hongfu; Li, Mingkun

2014-08-01

266

Magnetic properties of superparamagnetic nanoparticles loaded into silicon nanotubes  

NASA Astrophysics Data System (ADS)

In this work, the magnetic properties of silicon nanotubes (SiNTs) filled with Fe3O4 nanoparticles (NPs) are investigated. SiNTs with different wall thicknesses of 10 and 70 nm and an inner diameter of approximately 50 nm are prepared and filled with superparamagnetic iron oxide nanoparticles of 4 and 10 nm in diameter. The infiltration process of the NPs into the tubes and dependence on the wall-thickness is described. Furthermore, data from magnetization measurements of the nanocomposite systems are analyzed in terms of iron oxide nanoparticle size dependence. Such biocompatible nanocomposites have potential merit in the field of magnetically guided drug delivery vehicles.

Granitzer, Petra; Rumpf, Klemens; Gonzalez, Roberto; Coffer, Jeffery; Reissner, Michael

2014-08-01

267

Magnetic Properties of Young Stars in the TW Hydrae Association  

E-print Network

We present an analysis of infrared (IR) echelle spectra of five stars in the TW Hydrae Association (TWA). We model the Zeeman broadening in four magnetic-sensitive \\ion{Ti}{1} lines near $2.2 \\mu$m and measure the value of the photospheric magnetic field averaged over the surface of each star. To ensure that other broadening mechanisms are properly taken into account, we also inspect several magnetically insensitive CO lines near $2.3 \\mu$m and find no excess broadening above that produced by stellar rotation and instrumental broadening, providing confidence in the magnetic interpretation of the width of the \\ion{Ti}{1} lines. We then utilize our results to test the relationship between stellar magnetic flux and X-ray properties and compare the measured fields with equipartition field values. Finally, we use our results and recent results on a large sample of stars in Taurus to discuss the potential evolution of magnetic field properties between the age of Taurus ($\\sim$2 Myrs) and the age of TWA ($\\sim$10 Myrs). We find that the average stellar field strength increases with age; however, the total unsigned magnetic flux decreases as the stars contract onto the main-sequence.

Hao Yang; Christopher M. Johns-Krull; Jeff A. Valenti

2008-09-19

268

New pyridine-2,3,5,6-tetracarboxylato (H4pdtc) complexes: Synthesis, crystal structures and magnetic properties of K2[Mn(H2O)(pdtc)]·3H2O 1, Na2[M3(H2O)6(pdtc)2]·6H2O (M=Mn 2, Co 3)  

NASA Astrophysics Data System (ADS)

Three new pyridine-2,3,5,6-tetracarboxylato (H4pdtc) complexes K2[Mn(H2O)(pdtc)]·3H2O 1, Na2[M3(H2O)6(pdtc)2]·6H2O (M=Mn 2, Co 3) were obtained and characterized by single-crystal X-ray diffraction methods and magnetic measurements. The characteristic building blocks of 1-3 are the pdtc bridged stair-like chains ?1{[M(H2O)](pdtc)3/3}2-, which results from the six-coordinated transition metal atoms bridged by pdtc4- ligands. The infinite chains in 1 are assembled by hydrogen bonds into 2D supramolecular networks, which are held together by (4·82) topological K+-H2O networks to complete 3D architecture. While the stair-like chains in 2 and 3 are interconnected by trans-[M(H2O)4]2+ moieties to 2D polymeric layers, which are bridged by dimeric [Na2(?-H2O)2(H2O)2]2+ moieties to build up 3D framework. The magnetic properties of 1-3 were analyzed on the basis of (i) linear trinuclear M3 models and (ii) the free Mn2+ and Co2+ ions with the zero-field splitting effect and spin-orbit coupling effect, respectively.

Zheng, Yue-Qing; Zhu, Hong-Lin; Lin, Jian-Li; Xu, Wei; Hu, Fang-Hong

2013-05-01

269

Tunable electronic and magnetic properties of WS2 nanoribbons  

NASA Astrophysics Data System (ADS)

Two dimensional transition metal dichalcogenides (TMDs) have attracted great attention because of the versatile electronic structures. The electronic and magnetic properties of the nanoribbons are still not fully understood, which are crucial for their applications in nanodevices. In this work, the detailed atomic structural, electronic, and magnetic properties of the one dimensional WS2 nanoribbons have been carefully explored by first-principles calculations. The results suggest that the single layer WS2 will first transform into direct band gap semiconductor from indirect band gap of bulk one. Interestingly, the properties of WS2 nanoribbons are greatly affected by the type of the edges: Armchair nanoribbons (ANRs) remain nonmagnetic and semiconducting as that of bulk, whereas zigzag nanoribbons (ZNRs) exhibit ferromagnetic and metallic. Further, the electronic properties can be tuned by applying the external strains to WS2 nanoribbons: Band gap of ANRs experiences a direct-indirect-direct transition and the magnetic moment of ZNRs can be easily tuned by the different strains. All these findings suggest that the TMDs nanoribbons may exhibit extraordinary electronic and magnetic properties, and more importantly, such fascinating characters can be precisely modulated by controlling the edge types and applied strains.

Zhang, Hui; Li, Xi-Bo; Liu, Li-Min

2013-09-01

270

Estimation of hydrothermal deposits location from magnetization distribution and magnetic properties in the North Fiji Basin  

NASA Astrophysics Data System (ADS)

The North Fiji Basin is belong to one of the youngest basins of back-arc basins in the southwest Pacific (from 12 Ma ago). We performed the marine magnetic and the bathymetry survey in the North Fiji Basin for finding the submarine hydrothermal deposits in April 2012. We acquired magnetic and bathymetry datasets by using Multi-Beam Echo Sounder EM120 (Kongsberg Co.) and Overhouser Proton Magnetometer SeaSPY (Marine Magnetics Co.). We conducted the data processing to obtain detailed seabed topography, magnetic anomaly, reduce to the pole(RTP), analytic signal and magnetization. The study areas composed of the two areas(KF-1(longitude : 173.5 ~ 173.7 and latitude : -16.2 ~ -16.5) and KF-3(longitude : 173.4 ~ 173.6 and latitude : -18.7 ~ -19.1)) in Central Spreading Ridge(CSR) and one area(KF-2(longitude : 173.7 ~ 174 and latitude : -16.8 ~ -17.2)) in Triple Junction(TJ). The seabed topography of KF-1 existed thin horst in two grabens that trends NW-SE direction. The magnetic properties of KF-1 showed high magnetic anomalies in center part and magnetic lineament structure of trending E-W direction. In the magnetization distribution of KF-1, the low magnetization zone matches well with a strong analytic signal in the northeastern part. KF-2 area has TJ. The seabed topography formed like Y-shape and showed a high feature in the center of TJ. The magnetic properties of KF-2 displayed high magnetic anomalies in N-S spreading ridge center and northwestern part. In the magnetization distribution of KF-2, the low magnetization zone matches well with a strong analytic signal in the northeastern part. The seabed topography of KF-3 presented a flat and high topography like dome structure at center axis and some seamounts scattered around the axis. The magnetic properties of KF-3 showed high magnetic anomalies in N-S spreading ridge center part. In the magnetization of KF-2, the low magnetization zone mismatches to strong analytic signal in this area. The difference of KF-3 between the low magnetization zones and the analytic signals is considered that the submarine magnetic strength of KF-3 is lower than that of KF-1 and KF-2. The spreading ridges of the study areas showed common Central Anomaly Magnetization Highs (CAMH). As a whole, the previous studies on the structure of this study area (Auzende et al, 1990) support our results of the magnetic properties (Magnetic Anomaly and RTP). We can expect to have the better results by comparing with the other study like geophysics (seismic), geology, and geochemistry in this area. Reference Auzende, J.M., and 29 others, Active Spreading and Hydrothermalism in North Fiji Basin(SW Pacific). Results of Japanese French Cruise Kaiyo 87, Marine Geophysical Researches., 12, 269-283, 1990.

Choi, S.; Kim, C.; Park, C.; Kim, H.

2013-12-01

271

Relevance of magnetic properties of soil in the magnetic observatories to geomagnetic observation  

NASA Astrophysics Data System (ADS)

Annual geomagnetic variations with a maximum amplitude of 5 nT, and in phase with ground temperature variations at a depth of 1-2 m, were observed in the baseline values of fluxgate magnetometers installed at three JMA magnetic observatories. A possible origin of the annual variations is a change in magnetization of the soil due to changes in ground temperature. In order to examine the effect of temperature changes on soil magnetization, we measured the magnetic properties of soil samples collected at the JMA observatories. Magnetization of soil samples in a magnetic field of 0.05 mT ranged within 0.05× 10-3-1.6× 10-3 A m2/kg and the temperature dependence of magnetization ranged within 0.3× 10-6-14× 10-6 A m2/kg °C, except for a sample having an extraordinarily strong magnetization. Based on the measured magnetization, and their temperature dependence, of samples from Memambetsu, which shows the largest values among the samples from the three observatories, we determined the distribution of the geomagnetic field and its annual variation produced by soil magnetization. The maximum amplitude of annual variation in the geomagnetic field is 7 nT, which is consistent with the observed annual variation of the baseline value of the magnetometers.

Mishima, T.; Owada, T.; Moriyama, T.; Ishida, N.; Takahashi, K.; Nagamachi, S.; Yoshitake, Y.; Minamoto, Y.; Muromatsu, F.; Toyodome, S.

2013-04-01

272

Magnetic properties and scale-up of nanostructured cobalt carbide permanent magnetic powders  

NASA Astrophysics Data System (ADS)

CoxC magnetic nanoparticles were successfully synthesized via a modified polyol process without using a rare-earth catalyst during the synthesis process. The present results show admixtures of Co2C and Co3C phases possessing magnetization values exceeding 45 emu/g and coercivity values exceeding 2.3 kOe at room temperature. Moreover, these experiments have illuminated the important role of surfactants, reaction temperature, and reaction duration on the crystallographic structure and magnetic properties of CoxC, while tetraethylene glycol was employed as a reducing agent. The role of the ratios of Co2C and Co3C phases in the admixture magnetic properties is discussed. The crystallographic structure and particle size of the CoxC nanoparticles were characterized by X-ray diffractometry and scanning electron microscopy. Vibrating sample magnetometry was used to determine magnetic properties. Scale-up of synthesis to more than 5 g per batch was demonstrated with no significant degradation of magnetic properties.

Zamanpour, Mehdi; Bennett, Steven; Taheri, Parisa; Chen, Yajie; Harris, Vincent G.

2014-05-01

273

Spectral and Cyanide Binding Properties of the Cytochrome aa 3(600 nm) Complex from Bacillus subtilis  

Microsoft Academic Search

The cytochrome aa3(600 nm) complex, or menaquinol oxidase, fromBacillus subtilisis a member of the cytochrome oxidase superfamily of respiratory membrane protein complexes. We have characterized some spectral properties of this enzyme and its reaction with cyanide. The magnetic circular dichroism (MCD) spectrum of the oxidized enzyme has a single band at 1560 nm in the near-infrared region assigned to bis-histidine-ligated,

Bruce C. Hill; Jim Peterson

1998-01-01

274

Guadiana fault: magnetic and gravity constraints related with the Monchique Alkaline Complex structure (Betic Cordillera foreland)  

NASA Astrophysics Data System (ADS)

Geophysical data are essential to reveal the main crustal deep structures in areas where geological surface observations do not provide enough detailed data. Magnetic anomalies studies help us to constrain the structure of intermediate and basic igneous rocks. Magnetic and gravity surveys have been combined to determine the geometry, position and properties of intermediate igneous intrusive bodies responsible of the magnetic anomalies in the western area of the Betic Cordillera foreland. Furthermore, crustal structure has been characterized revealing the presence of a blind fault: The Guadiana fault. The aeromagnetic data reveal that the southwestern Iberian Peninsula is characterized by an elongated E-W dipole extending 200 km towards the Betic Cordillera external zones. The anomaly is related to the outcropping Monchique Alkaline Complex, characterized by rocks of moderate magnetic susceptibility (0.029 SI) intruding into the metapelitic host rock of the South Portuguese Zone. In this region, new total field magnetic data has been acquired with a GSM 8 proton precession magnetometer with an accuracy of 1 nT at a mean height of 2 m above the topography. Susceptibility measurements were done with an Exploranium KT-9 kappameter. Combined analysis of aeromagnetic and field magnetic anomalies serves to constrain the depth and geometry of this laccolith. Toward the east, the magnetic dipole has a 60 km long N-S sharp step that coincides with the southern part of the Guadiana River (Spain-Portugal southernmost border). In addition, gravity measurements were performed simultaneously with the magnetic data acquisition using a Scintrex Autograv CG-5 gravity meter whose maximum accuracy is 0.001 mGal. This data support the presence of this major discontinuity in the elongated anomalous body, with an E downthrown block, interpreted as the offset produced by a deep N-S crustal fault - The Guadiana Fault. Therefore, the Guadiana River has three long linear segments near its mouth, locally coinciding with a N-S trending joint set, that support the presence of this structure. To date, no evidence of this tectonic discontinuity, coinciding with the Spanish-Portuguese border, has been reported. Magnetic research is essential for understanding the structure of wide regions intruded by intermediate and/or basic igneous rocks.

González-Castillo, Lourdes; Galindo-Zaldívar, Jesús; Ruiz-Constán, Ana; Pedrera, Antonio

2014-05-01

275

Size-dependent magnetic properties of nickel nanochains  

NASA Astrophysics Data System (ADS)

Magnetic properties with three different sizes of Ni nanochains, synthesized by a technique of wet chemical solution, have been investigated experimentally. The sample sizes (average diameter of the nano-particles) are 50, 75, and 150 nm, with a typical length of a few microns. The characterizations by XRD and TEM reveal that the samples consist of Ni nano-particles forming a one-dimensional (1D) chain-like structure. Magnetic properties have been investigated by temperature dependent magnetization M(T) and field dependent magnetization M(H) measurements. The results are explained within the context of the core-shell model. First, the freezing of disordered spins in the shell layer has resulted in a peak structure on the zero-field-cooled (ZFC) M(T) curve. The peak position is identified as the freezing temperature TF. It is well described by the de Almeida-Thouless (AT) equation for the surface spin glass state. Second, the shape anisotropy of the 1D structure has caused a wide separation between the field-cooled (FC) and ZFC M(T) curves. This is mainly attributed to the blocking of the core magnetism by an anisotropy barrier, EA. Third, by the M(H) measurement in the low field region, the open hysteresis loop measured at T = 5 KTF. This indicates that a significant part of the contribution to the magnetic irreversibility at Tmagnetization goes down substantially. These imply that, as the sample size reduces, the effect of shape anisotropy becomes larger in the magnetization reversal process and the contribution to the magnetism from the ferromagnetically ordered core becomes smaller.

He, Lin; Zheng, Wangzhi; Zhou, Wei; Du, Honglin; Chen, Chinping; Guo, Lin

2007-01-01

276

Ferrimagnetic garnet thin films: Growth, structure and some magnetic properties  

Microsoft Academic Search

Ferrimagnetic garnet films, mainly gadolinium iron garnet, were deposited on fused-quartz substrates and subsequently heat-treated. They were studied by optical microscopy, X-ray analysis, and electron microscopy. Magnetic properties were measured and domains observed by employing the Faraday magneto-optic effect. Structure and properties were found to depend on growth parameters established in the heat-treatment step. The role of chemical factors in

M. Oron; I. Barlow; W. F. Traber

1969-01-01

277

Complex interplanetary ejecta and their association to multi-step magnetic storm main phase development  

Microsoft Academic Search

It was observed long time ago that, although the classical definition of magnetic storms is quite simple, a magnetic storm could evolves in a much more complex way. It was recently shown that the main phase of intense magnetic storms usually develops in two or more steps. It occurs as a consequence of several energy injections during the main phase

L. E. Vieira; W. D. Gonzalez; A. L. Clua de Gonzalez; A. dal Lago; E. Echer; F. L. Guarnieri; L. Balmaceda; N. J. Schuch

2003-01-01

278

Magnetic properties of maraging steels in relation to nickel concentration  

SciTech Connect

Magnetic properties of maraging steels have been investigated as a function of nickel concentration. The alloys nickel content varied from 12 to 24 wt pct, while other alloying constituents were kept at a level maintained in the 18Ni-2,400 MPA-grade maraging steel. The magnetic properties were determined following aging for 1 hour in the temperature range of 450 to 750 C. In every alloy investigated, the coercive field increased with aging temperature, reaching a maximum around 670 C {+-} 30 C. The saturation magnetization values were lowest around temperatures where maximum coercive field was observed. The coercive field increased from {approximately}55 to {approximately}175 Oe ({approximately}4,380 to {approximately} 13,900 amp/meter) and the corresponding saturation magnetization decreased from {approximately}18,500 to {approximately}4,000 G ({approximately}1.85 to {approximately}0.4 T) in the alloys containing 12 and 24 wt pct Ni, respectively. The reverted austenite increased from 25 vol pct at 12 wt pct Ni to 10 vol pct at 24 wt pct Ni. The hardness and Charpy impact strength of the alloys have also been determined. An attempt has been made to correlate magnetic properties with different phase transformations occurring in maraging steels.

Ahmed, M.; Nasim, I.; Ayub, H. [Dr. A.Q. Khan Research Labs., Rawalpindi (Pakistan); Hasnain, K. [Quaid-i-Azam Univ., Islamabad (Pakistan)

1995-07-01

279

Magnetic properties prediction of NdFeB magnets by using support vector regression  

NASA Astrophysics Data System (ADS)

A novel model using support vector regression (SVR) combined with particle swarm optimization (PSO) was employed to construct mathematical model for prediction of the magnetic properties of the NdFeB magnets. The leave-one-out cross-validation (LOOCV) test results strongly supports that the generalization ability of SVR is high enough. Predicted results show that the mean absolute percentage error for magnetic remanence Br, coercivity Hcj and maximum magnetic energy product (BH)max are 0.53%, 3.90%, 1.73%, and the correlation coefficient (R2) is as high as 0.839, 0.967 and 0.940, respectively. This investigation suggests that the PSO-SVR is not only an effective and practical method to simulate the properties of NdFeB, but also a powerful tool to optimatize designing or controlling the experimental process.

Cheng, Wende

2014-09-01

280

Transport properties of graphene under periodic and quasiperiodic magnetic superlattices  

NASA Astrophysics Data System (ADS)

We study the transmission of Dirac electrons through the one-dimensional periodic, Fibonacci, and Thue-Morse magnetic superlattices (MS), which can be realized by two different magnetic blocks arranged in certain sequences in graphene. The numerical results show that the transmission as a function of incident energy presents regular resonance splitting effect in periodic MS due to the split energy spectrum. For the quasiperiodic MS with more layers, they exhibit rich transmission patterns. In particular, the transmission in Fibonacci MS presents scaling property and fragmented behavior with self-similarity, while the transmission in Thue-Morse MS presents more perfect resonant peaks which are related to the completely transparent states. Furthermore, these interesting properties are robust against the profile of MS, but dependent on the magnetic structure parameters and the transverse wave vector.

Lu, Wei-Tao; Wang, Shun-Jin; Wang, Yong-Long; Jiang, Hua; Li, Wen

2013-08-01

281

Magnetic property improvement of niobium doped with rare earth elements  

NASA Astrophysics Data System (ADS)

A new idea is proposed by the PKU group to improve the magnetic properties of the Type-II superconductor niobium. Rare earth elements like scandium and yttrium are doped into ingot niobium during the smelting processes. A series of experiments have been done since 2010. The preliminary testing results show that the magnetic properties of niobium materials have changed with different doping elements and proportions while the superconductive transition temperature does not change very much. This method may increase the superheating magnetic field of niobium so as to improve the performance of the niobium cavity, which is a key component of SRF accelerators. A Tesla-type single-cell cavity made of scandium-doped niobium is being fabricated.

Jiang, Tao; He, Fei-Si; Jiao, Fei; He, Fa; Lu, Xiang-Yang; Zhao, Kui; Zhao, Hong-Yun; You, Yu-Song; Chen, Lin

2014-05-01

282

Hard X-ray properties of magnetic cataclysmic S. Scaringi  

E-print Network

Hard X-ray properties of magnetic cataclysmic variables S. Scaringi , A.J. Bird , A.J. Norton , C arising from this hard X-ray selected sample and find that most hard X-ray detected mCVs have Pspin in the context of mCV evolution scenarios. We also present evidence for corre- lations between hard X

Norton, Andrew J.

283

Anisotropic physical properties of SC15 epoxy reinforced with magnetic nanofillers under uniform magnetic field  

Microsoft Academic Search

The mechanical properties of SC-15 epoxy can be significantly enhanced when reinforced with nanofillers. In this study, SC-15\\u000a epoxy is loaded with iron oxide nanoparticles and chemically functionalized single-wall carbon nanotubes and cured in a modest\\u000a magnetic field. Magnetic analysis shows that the iron oxide nanoparticles flocculate to form chains and create a structural\\u000a anisotropy in the system. Measurements of

O. Malkina; H. Mahfuz; K. D. Sorge; V. K. Rangari

2011-01-01

284

Geometric and magnetic properties of Co/Pd system  

NASA Astrophysics Data System (ADS)

We measured geometric and magnetic properties of Co films on the Pd(1 1 1) surface by X-ray photoelectron diffraction (XPD), X-ray magnetic circular dichroism (MCD) at the Co L 2,3 edge, and the surface magneto-optical Kerr effect (SMOKE) measurements. Co thin films are found to grow incoherently with fcc island structure on the smooth Pd(1 1 1) substrate. Comparison of MCD and SMOKE measurements of Co thin films grown on rough and smooth Pd(1 1 1) surfaces suggests that perpendicular remnant magnetization and Co orbital moment are enhanced by the rough interface. Pd capping layer also induces perpendicular orbital moment enhancement. These observations indicate the influence of hybridization between Co 3d and Pd 4d at the interface on the magnetic anisotropy.

Oh, S.-J.; Kim, Wookje; Kim, Wondong; Choi, B.-H.; Kim, Jae-Young; Koh, Hoon; Kim, H.-J.; Park, J.-H.

2001-01-01

285

Magnetic properties of RNi 5-xCu x intermetallics  

NASA Astrophysics Data System (ADS)

The magnetic properties have been studied for the series of RNi 5-xCu x intermetallics with R=Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Lu; x?2.5. Compositional dependences of magnetic susceptibility for the Pauli paramagnets (R=Y, La, Ce, Lu) and the Curie temperature for ferromagnets (R=Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm) have maximum at x=0.2-0.4 and 1, respectively. The substitution of Cu for Ni is accompanied by decreasing spontaneous magnetic moment and increasing coercive force of all ferromagnetic RNi 5-xCu x but GdNi 5-xCu x. These results are explained in the frame of band magnetism, random local crystal field, and domain wall pinning theories.

Kuchin, A. G.; Ermolenko, A. S.; Kulikov, Yu. A.; Khrabrov, V. I.; Rosenfeld, E. V.; Makarova, G. M.; Lapina, T. P.; Belozerov, Ye. V.

2006-08-01

286

Magnetic properties of obliquely evaporated Co thin films  

NASA Astrophysics Data System (ADS)

The magnetic properties of Co thin films obliquely evaporated under silicon and glass substrates are investigated using alternating gradient field magnetometer (AGFM) and magnetic force microscopy (MFM) techniques. The effects of the magnetic layer thickness and the deposition angle are studied. As results, it is found a decrease of the coercive field from 250 Oe, for t = 20 nm, to 95 Oe, for t = 400 nm, and a decrease of the anisotropy field from 1.6 kOe for 20 nm Co thick film, to 0.95 kOe for 200 nm Co thick film. An increase of these fields with the increase of the deposition angle is also found. The easy axis of the saturation magnetization lies in the film plane, whatever is the substrate nature. MFM images reveal well-defined stripe patterns, particularly for the thickest films, where the magnetocrystalline anisotropy is dominant. These results, and others, are presented and discussed.

Kharmouche, Ahmed

2014-10-01

287

Properties- and applications of quasicrystals and complex metallic alloys.  

PubMed

This article aims at an account of what is known about the potential for applications of quasicrystals and related compounds, the so-called family of Complex Metallic Alloys (CMAs‡). Attention is focused at aluminium-based CMAs, which comprise a large number of crystalline compounds and quasicrystals made of aluminium alloyed with transition metals (like Fe or Cu) or normal metals like Mg. Depending on composition, the structural complexity varies from a few atoms per unit cell up to thousands of atoms. Quasicrystals appear then as CMAs of ultimate complexity and exhibit a lattice that shows no periodicity anymore in the usual 3-dimensional space. Properties change dramatically with lattice complexity and turn the metal-type behaviour of simple Al-based crystals into a far more complex behaviour, with a fingerprint of semi-conductors that may be exploited in various applications, potential or realised. An account of the ones known to the author is given in the light of the relevant properties, namely light absorption, reduced adhesion and friction, heat insulation, reinforcement of composites for mechanical devices, and few more exotic ones. The role played by the search for applications of quasicrystals in the development of the field is briefly addressed in the concluding section. PMID:22933085

Dubois, Jean-Marie

2012-10-21

288

Novel thiocyanato complexes with potent cytotoxic and antimicrobial properties.  

PubMed

The aim of the present study was to assess the cytotoxic and antimicrobial properties of seven new thiocyanato complexes: Ni(C(9)H(11)N(2)O)(SCN), Cu(C(9)H(11)N(2)O)(SCN), Pd(C(9)H(11)N(2)O)(SCN), Pt(C(9)H(11)N(2) O) (SCN), K[Ti(C(9)H(11)N(2)O)(SCN)(3)], Au(C(9)H(11)N(2)O)(SCN), and K[V(O)(C(9)H(11)N(2)O)(SCN)] (T(1)-T(7), respectively). All the complexes showed toxicity against brine shrimp nauplii (Artemia salina L.). The titanium-based complex, T(5), exhibited potent toxicity, with a lethal concentration 50% (the concentration of test compound that kills 50% of A. salina) value of 1.59 microg mL(-1). These new complexes also exhibited promising antibacterial and antifungal properties. A macrodilution technique was used to estimate the minimum inhibitory concentrations of the seven bioactive complexes. Minimum inhibitory concentrations were found to be 8-64 microg mL(-1) against the tested bacterial species. PMID:15563758

Hossain, M Shamim; Easmin, Sabina; Islam, M Saidul; Rashid, Mamunur

2004-12-01

289

Synthesis, crystal structures, and magnetic properties of cobalt(II) and nickel(II) complexes of 2,2?-bipyridine-6,6?-dicarboxylate: three three-dimensional networks formed via hydrogen bonding interactions  

Microsoft Academic Search

Three Co(II) and Ni(II) complexes, namely [Co(bpdc)(H2O)2] (1), [Ni(bpdc)(H2O)2] (2), and [Co2(bpdc)2(prz)0.5(H2O)3]·0.5H2O (3) (H2bpdc = 2,2?-bipyridine-6,6?-dicarboxylic acid and prz = piperazine), have been synthesized from H2bpdc and the corresponding metal salts under hydrothermal conditions. The complexes were characterized by physico-chemical\\u000a and spectroscopic methods, as well as by X-ray crystallography. Compounds 1 and 2 both consist of neutral mononuclear molecules, of [Co(bpdc)(H2O)2] and [Ni(bpdc)(H2O)2], respectively.

Jin-Zhong Gu; Dong-Yu Lv; Zhu-Qing Gao; Jian-Zhao Liu; Wei Dou

2011-01-01

290

Magnetic properties of grain oriented electrical steel in model transformer under direct current-biased magnetization  

NASA Astrophysics Data System (ADS)

Iron losses and acoustic noises of the model transformer under DC-biased magnetization were empirically investigated. To clarify the influence of magnetic properties of transformer core materials, two types of grain oriented electrical steels—high permeability grade (HGO) and conventional grade (CGO)—were used as core materials. Iron losses increased with superimposing DC-bias magnetic field (HDC) in both materials, and the iron loss increment in HGO was larger than that in CGO. Acoustic noises increased with increasing HDC in both materials; however, noises emitted from the core of HGO were smaller than those of CGO.

Inoue, Hirotaka; Okabe, Seiji

2014-05-01

291

Measurement of bidirectional optical properties of complex shading devices  

SciTech Connect

A new method of predicting the solar heat gain through complex fenestration systems involving nonspecular layers such as shades or blinds has been examined in a project jointly sponsored by ASHRAE and DOE. In this method, a scanning radiometer is used to measure the bidirectional radiative transmittance and reflectance of each layer of a fenestration system. The properties of systems containing these layers are then built up computationally from the measured layer properties using a transmission/multiple-reflection calculation. The calculation produces the total directional-hemispherical transmittance of the fenestration system and the layer-by-layer absorptances. These properties are in turn combined with layer-specific measurements of the inward-flowing fractions of absorbed solar energy to produce the overall solar heat gain coefficient. This paper describes the method of measuring the spatially averaged bidirectional optical properties using an automated, large-sample gonioradiometer/photometer, termed a ``Scanning Radiometer.`` Property measurements are presented for one of the most optically complex systems in common use, a venetian blind. These measurements will form the basis for optical system calculations used to test the method of determining performance.

Klems, J.H.; Warner, J.L.

1995-01-01

292

Physical constraints on lossy acoustic metamaterials with complex effective properties.  

PubMed

Recent theoretical and experimental work on acoustic metamaterials (AMM) has demonstrated materials that demonstrate many properties, such as negative modulus and density, beyond what is capable using conventional materials. In most cases, AMM are assumed to be passive and causal with frequency dependent losses accounted for via complex modulus and density. Despite the maturity of AMM research, literature concerning the physical constraints on the complex effective constitutive properties for passive, causal AMM is very limited. This work presents the physical limits for the real and imaginary effective dynamic mass density and dynamic compressibility via recourse to restrictions placed on the AMM by conservation of energy, passivity, and causality. We further note that constitutive properties are determined from the effective wavenumber and impedance extracted from simulation or experiment. Although care is normally taken to guarantee that passivity holds for the wavenumber and impedance, assumptions implicit in various homogenization schemes can result in constitutive properties that do not satisfy passivity and causality. This work will therefore also discuss implications on AMM homogenization and extraction of properties due to constraints based on the foundational concepts of conservation of energy, passivity, and causality. [This work was supported by the Office of Naval Research.]. PMID:25235322

Sieck, Caleb F; Haberman, Michael R; Alù, Andrea

2014-04-01

293

Interrelation between Structure Magnetic Properties in La0.5Sr0.5CoO3  

SciTech Connect

Differing anisotropic strain induced from the underlying substrates not only control the long-range structural symmetries in La0.5Sr0.5CoO3 but also impact the magnetic properties of these epitaxial thin films. The two dominant structural distortions: oxygen octahedral tilts and epitaxial strain, however, have complex and non-intuitive effects on the splitting of the t2g states and consequently on magnetization.

Biegalski, Michael D [ORNL] [ORNL; Takamura, Y [University of California, Davis] [University of California, Davis; Mehta, A [Stanford Synchrotron Radiation Lightsource] [Stanford Synchrotron Radiation Lightsource; Gai, Zheng [ORNL] [ORNL; Kalinin, Sergei [Oak Ridge National Laboratory (ORNL)] [Oak Ridge National Laboratory (ORNL); Ambaye, Hailemariam [Spallation Neutron Source] [Spallation Neutron Source; Lauter, Valeria [ORNL] [ORNL; He, Jun [ORNL] [ORNL; Kim, Young Min [ORNL] [ORNL; Borisevich, Albina Y [ORNL] [ORNL; Siemons, Wolter [ORNL] [ORNL; Christen, Hans M [ORNL] [ORNL

2014-01-01

294

Dielectric, magnetic, and microwave absorbing properties of multi-walled carbon nanotubes filled with Sm 2O 3 nanoparticles  

Microsoft Academic Search

This study investigates the dielectric, magnetic, and microwave absorbing properties of Sm2O3-filled multi-walled carbon nanotubes (MWCNTs) synthesized by wet chemical method. The complex permittivity and permeability were measured at a microwave frequency range of 2–18 GHz. Sm2O3 nanoparticles encapsulated in the cavities enhance the magnetic loss of MWCNTs. The calculated results indicate that the bandwith of absorbing peak of the modified

Lan Zhang; Hong Zhu

2009-01-01

295

Structure and luminescence properties of tellurium(IV) complex compounds  

NASA Astrophysics Data System (ADS)

Using the tellurium(IV) complex compounds as an example, we study the interrelation between the geometric structure and spectral luminescence properties. We find that, in the series of compounds of Te(IV), which are characterized by the island octahedral coordination of Te(IV) ions, the luminescence intensity depends on the degree of distortion of the Te(IV) coordination polyhedron, the Stokes shift, and the energy of the luminescence transition. We revealed that the considered series of Te(IV) compounds possess reversible thermochromic properties.

Sedakova, T. V.; Mirochnik, A. G.; Karasev, V. E.

2011-05-01

296

Tetrathiafulvalene-Supported Triple-Decker Phthalocyaninato Dysprosium(III) Complex: Synthesis, Properties and Surface Assembly  

NASA Astrophysics Data System (ADS)

Self-assembly of functional compounds into a prerequisite nanostructure with desirable dimension and morphology by controlling and optimizing intermolecular interaction attracts an extensive research interest for chemists and material scientist. In this work, a new triple-decker sandwich-type lanthanide complex with phthalocyanine and redox-active Schiff base ligand including tetrathiafulvalene (TTF) units has been synthesized, and characterized by single crystal X-ray diffraction analysis, absorption spectra, electrochemical and magnetic measurements. Interestingly, the non-centrosymmetric target complex displays a bias dependent selective adsorption on a solid surface, as observed by scanning tunneling microscopy (STM) at the single molecule level. Density function theory (DFT) calculations are utilized to reveal the formation mechanism of the molecular assemblies, and show that such electrical field dependent selective adsorption is regulated by the interaction between the external electric field and intrinsic molecular properties. Our results suggest that this type of multi-decker complex involving TTF units shows intriguing multifunctional properties from the viewpoint of structure, electric and magnetic behaviors, and fabrication through self-assembly.

Gao, Feng; Zhang, Xue-Mei; Cui, Long; Deng, Ke; Zeng, Qing-Dao; Zuo, Jing-Lin

2014-08-01

297

Tetrathiafulvalene-supported triple-decker phthalocyaninato dysprosium(III) complex: synthesis, properties and surface assembly.  

PubMed

Self-assembly of functional compounds into a prerequisite nanostructure with desirable dimension and morphology by controlling and optimizing intermolecular interaction attracts an extensive research interest for chemists and material scientist. In this work, a new triple-decker sandwich-type lanthanide complex with phthalocyanine and redox-active Schiff base ligand including tetrathiafulvalene (TTF) units has been synthesized, and characterized by single crystal X-ray diffraction analysis, absorption spectra, electrochemical and magnetic measurements. Interestingly, the non-centrosymmetric target complex displays a bias dependent selective adsorption on a solid surface, as observed by scanning tunneling microscopy (STM) at the single molecule level. Density function theory (DFT) calculations are utilized to reveal the formation mechanism of the molecular assemblies, and show that such electrical field dependent selective adsorption is regulated by the interaction between the external electric field and intrinsic molecular properties. Our results suggest that this type of multi-decker complex involving TTF units shows intriguing multifunctional properties from the viewpoint of structure, electric and magnetic behaviors, and fabrication through self-assembly. PMID:25088605

Gao, Feng; Zhang, Xue-Mei; Cui, Long; Deng, Ke; Zeng, Qing-Dao; Zuo, Jing-Lin

2014-01-01

298

Anisotropy of magnetic properties of Fe1+yTe.  

PubMed

The magnetic properties of Fe1+yTe single crystals (y ? 0.1 ÷ 0.18) were studied at temperatures 4.2 ÷ 300 K. At an ambient pressure, with decreasing temperature a drastic drop in ?(T) was confirmed at T ? 60 ÷ 65 K, which appears to be closely related to the antiferromagnetic (AFM) ordering. It is found that the magnitudes of the anisotropy of magnetic susceptibility ?? in the AFM phase are close in the studied samples, whereas the sign of the anisotropy apparently depends on the small variations of the excess iron y in Fe1+yTe samples. The performed DFT calculations of the electronic structure and magnetic properties for the stoichiometric FeTe compound indicate the presence of frustrated AFM ground states. There are very close energies and magnetic moments for the double stripe configurations, with the AFM axes oriented either on the basal plane or along the [0?0?1] direction. Presumably, both these configurations can be realized in Fe1+yTe single crystals, depending on the variations of the excess iron. This can provide different signs of magnetic anisotropy in the AFM phase, presently observed in the Fe1+yTe samples. For these types of AFM configuration, the calculations for the FeTe values of ?? are consistent with our experimental data. PMID:25299131

Grechnev, G E; Panfilov, A S; Fedorchenko, A V; Lyogenkaya, A A; Zhuravleva, I P; Chareev, D A; Nekrasov, A N; Mitrofanova, E S; Volkova, O S; Vasiliev, A N; Eriksson, O

2014-10-29

299

Magnetic properties of nanocrystalline KNbO{sub 3}  

SciTech Connect

Newly synthesized undoped and iron-doped nanoscale powders of KNbO{sub 3} are investigated using magnetic resonance and static magnetization methods in order to determine how the crystal size and doping affect the structure of magnetic defects and material properties. Although the bulk crystals of KNbO{sub 3} are nonmagnetic, the undoped KNbO{sub 3} powder with average particle size of 80?nm exhibits magnetic properties. The ferromagnetic resonance signal and the magnetization curve registered on the powder are thoroughly analyzed. It is concluded that the appearance of the defect driven ferromagnetism in the undoped powder is due to the nano-size of the particles. This effect disappears in the iron-doped KNbO{sub 3} powder with particle sizes above 300?nm. In case of low doping (<1?mol. % Fe), a new electron paramagnetic resonance signal with g{sub eff}?=?4.21 is found out in the KNbO{sub 3}:Fe powder. Such a signal has not been observed in the bulk crystals of KNbO{sub 3}:Fe. We suppose that this signal corresponds to individual paramagnetic Fe{sup 3+} ions having rhombic symmetry.

Golovina, I. S., E-mail: golovina@isp.kiev.ua; Shanina, B. D.; Kolesnik, S. P. [Institute of Semiconductor Physics of NAS of Ukraine, Pr. Nauky 41, 03028 Kyiv (Ukraine); Geifman, I. N. [Quality Engineering Education, Inc., Buffalo Grove, Illinois 60089 (United States); Andriiko, A. A. [National Technical University of Ukraine “KPI”, pr. Peremogy 37, 03056 Kyiv (Ukraine)

2013-11-07

300

Anisotropy of magnetic properties of Fe1+yTe  

NASA Astrophysics Data System (ADS)

The magnetic properties of Fe1+yTe single crystals (y ? 0.1 ÷ 0.18) were studied at temperatures 4.2 ÷ 300 K. At an ambient pressure, with decreasing temperature a drastic drop in ?(T) was confirmed at T ? 60 ÷ 65 K, which appears to be closely related to the antiferromagnetic (AFM) ordering. It is found that the magnitudes of the anisotropy of magnetic susceptibility ?? in the AFM phase are close in the studied samples, whereas the sign of the anisotropy apparently depends on the small variations of the excess iron y in Fe1+yTe samples. The performed DFT calculations of the electronic structure and magnetic properties for the stoichiometric FeTe compound indicate the presence of frustrated AFM ground states. There are very close energies and magnetic moments for the double stripe configurations, with the AFM axes oriented either on the basal plane or along the [0?0?1] direction. Presumably, both these configurations can be realized in Fe1+yTe single crystals, depending on the variations of the excess iron. This can provide different signs of magnetic anisotropy in the AFM phase, presently observed in the Fe1+yTe samples. For these types of AFM configuration, the calculations for the FeTe values of ?? are consistent with our experimental data.

Grechnev, G. E.; Panfilov, A. S.; Fedorchenko, A. V.; Lyogenkaya, A. A.; Zhuravleva, I. P.; Chareev, D. A.; Nekrasov, A. N.; Mitrofanova, E. S.; Volkova, O. S.; Vasiliev, A. N.; Eriksson, O.

2014-10-01

301

Growth and Properties of MnxGa Magnetic Nanostructures  

NASA Astrophysics Data System (ADS)

Rare-Earth (RE) magnets are becoming more expensive and less available for current applications in technology. MnxGa (x=2-3) has previously shown coercivity of 2.5 T, close to that of RE magnets.footnotetextT.J. Nummy, S.P Bennett, T. Cardinal, and D. Heiman, Large Coercivity in Nanostructured Rare-earth-free MnxGa Films, Appl. Phys. Lett. 99, 252506 (2011). In this project, the vapor-liquid-solid (VLS) method was used to grow nanoparticles of MnxGa (x=1-3) with MBE. The goal was to study the magnetic properties as a function of reduced dimensionality. The samples were prepared by depositing a 3-6 nm layer of Au on Si, GaAs, and glass. It was found that the miscibility of Ga and Au is high, but for Mn and Au it is much lower. Therefore, during the growth process Ga was deposited on the gold catalyst followed by Mn deposition. The samples were then annealed at temperatures 100-500 ^oC. Nanostructures, including regions of nanowires, were found using scanning electron microscopy on all samples. The magnetic properties of the nanostructured samples were studied with SQUID magnetometry and found to have a magnetization of 200 emu/cm^3.

Jamer, Michelle; Assaf, Badih A.; Eich, Marius; Moodera, Jagadeesh S.; Heiman, Don

2013-03-01

302

Axisymmetric Flow Properties for Magnetic Elements of Differing Strength  

NASA Technical Reports Server (NTRS)

Aspects of the structure and dynamics of the flows in the Sun's surface shear layer remain uncertain and yet are critically important for understanding the observed magnetic behavior. In our previous studies of the axisymmetric transport of magnetic elements we found systematic changes in both the differential rotation and the meridional flow over the course of Solar Cycle 23. Here we examine how those flows depend upon the strength (and presumably anchoring depth) of the magnetic elements. Line of sight magnetograms obtained by the HMI instrument aboard SDO over the course of Carrington Rotation 2097 were mapped to heliographic coordinates and averaged over 12 minutes to remove the 5-min oscillations. Data masks were constructed based on the field strength of each mapped pixel to isolate magnetic elements of differing field strength. We used Local Correlation Tracking of the unmasked data (separated in time by 1- to 8-hours) to determine the longitudinal and latitudinal motions of the magnetic elements. We then calculated average flow velocities as functions of latitude and longitude from the central meridian for approx 600 image pairs over the 27-day rotation. Variations with longitude indicate and characterize systematic errors in the flow measurements associated with changes in the signal from disk center to limb. Removing these systematic errors reveals changes in the axisymmetric flow properties that reflect changes in flow properties with depth in the surface shear layer.

Rightmire-Upton, Lisa; Hathaway, David H.

2012-01-01

303

Synthesis, properties and reactivity of intramolecular hypercoordinate silicon complexes  

NASA Astrophysics Data System (ADS)

The state of the art of the chemistry of hypercoordinate silicon compounds is analyzed. Published data on the current top-priority approaches to the preparative synthesis of these compounds and on their properties, structures and reactivity are summarized and generalized. Relying on the results obtained by modern physicochemical methods, the possible mechanisms of stereodynamic processes occurring in the coordination units of hypercoordinate silicon complexes are discussed. The bibliography includes 157 references.

Nikolin, A. A.; Negrebetsky, V. V.

2014-09-01

304

Magnetic properties of bio-synthesized zinc ferrite nanoparticles  

SciTech Connect

The magnetic properties of zinc ferrite (Zn-substituted magnetite, Zn{sub y}Fe{sub 1-y}Fe{sub 2}O{sub 4}) formed by a microbial process compared favorably with chemically synthesized materials. A metal reducing bacterium, Thermoanaerobacter, strain TOR-39 was incubated with Zn{sub x}Fe{sub 1-x}OOH (x=0.01, 0.1, and 0.15) precursors and produced nanoparticulate zinc ferrites. Composition and crystalline structure of the resulting zinc ferrites were verified using X-ray fluorescence, X-ray diffraction, transmission electron microscopy, and neutron diffraction. The average composition from triplicates gave a value for y of 0.02, 0.23, and 0.30 with the greatest standard deviation of 0.02. Average crystallite sizes were determined to be 67, 49, and 25 nm, respectively. While crystallite size decreased with more Zn substitution, the lattice parameter and the unit cell volume showed a gradual increase in agreement with previous literature values. The magnetic properties were characterized using a superconducting quantum interference device magnetometer and were compared with values for the saturation magnetization (M{sub s}) reported in the literature. The averaged M{sub s} values for the triplicates with the largest amount of zinc (y=0.30) gave values of 100.1, 96.5, and 69.7 emu/g at temperatures of 5, 80, and 300 K, respectively indicating increased magnetic properties of the bacterially synthesized zinc ferrites.

Yeary, Lucas W [ORNL; Moon, Ji Won [ORNL; Rawn, Claudia J [ORNL; Love, Lonnie J [ORNL; Rondinone, Adam Justin [ORNL; Thompson, James R [ORNL; Chakoumakos, Bryan C [ORNL; Phelps, Tommy Joe [ORNL

2011-01-01

305

Magnetic Properties of High Ti Titanomagnetite Under Pressure  

NASA Astrophysics Data System (ADS)

We present new data on the magnetic properties of titanium-rich titanomagnetite under pressures exceeding 7 GPa. The new data confirm that the piezoremanent response of titanomagnetite increases with Ti concentration; e.g., that lower pressures are needed to increase the magnetic remanence as Ti increases. We will also show results that pressure can transform high-Ti titanomagnetite that is paramagnetic at room temperature into a ferrimagnet. This coincides well with previous work suggesting the Curie temperature of high-Ti titanomagnetite increases about 15 degrees per gigapascal. Finally, we will address the question of the threshold pressure needed to saturate the piezoremanent effect in multidomain titanomagnetite.

Gilder, S. A.; Wei, Q.; Ertel-Ingrisch, W.; Church, N. S.

2013-12-01

306

Magnetic properties of lithographically defined rectangular antidot permalloy arrays  

NASA Astrophysics Data System (ADS)

We have investigated the magnetic properties of rectangular antidot (2×10?m2) arrays embedded into 80nm thick continuous permalloy films with the inter-hole spacing of 2 and 6?m. We observed that the presence of the rectangular hole structures strongly modifies the shape of M-H loops, when compared with the reference continuous film. Specifically, the coercivity increases drastically as the inter-hole spacing is reduced. This is in agreement with our magnetic force microscopy images. Marked changes in both the shape and sign of the magnetoresistance curve were also observed.

Wang, C. C.; Adeyeye, A. O.; Lin, C. C.

2004-05-01

307

Magnetic properties of lithographically defined rectangular antidot permalloy arrays  

NASA Astrophysics Data System (ADS)

We have investigated the magnetic properties of rectangular antidot (2×10 ?m2) arrays embedded into 80 nm thick continuous permalloy films with the inter-hole spacing of 2 and 6 ?m. We observed that the presence of the rectangular hole structures strongly modifies the shape of M- H loops, when compared with the reference continuous film. Specifically, the coercivity increases drastically as the inter-hole spacing is reduced. This is in agreement with our magnetic force microscopy images. Marked changes in both the shape and sign of the magnetoresistance curve were also observed.

Wang, C. C.; Adeyeye, A. O.; Lin, C. C.

308

Aging of magnetic properties in MgO films  

SciTech Connect

In this work we report on the magnetic behavior of MgO thin films prepared by sputtering. A severe aging process of the ferromagnetic properties is detected in magnetic samples exposed to ambient atmosphere. However, ferromagnetism can be successively switched on again by annealing samples in vacuum. We suggest this behavior reflects the key role played by defects in stabilizing ferromagnetism in MgO films and is likely to be closely related to the hydrogen-driven instability of V-type centers in this material.

Balcells, Ll.; Konstantinovic, Z.; Martinez, B. [Instituto de Ciencia de Materiales de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra 08193 (Spain); Beltran, J. I. [Departamento de Fisica Teorica de la Materia Condensada, Universidad Autonoma de Madrid, Madrid 28049 (Spain); Martinez-Boubeta, C. [Departament d'Electronica and IN2UB, Universitat de Barcelona, Barcelona 08028 (Spain); Arbiol, J. [Instituto de Ciencia de Materiales de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra 08193 (Spain); Institucio Catalana de Recerca i Estudis Avancats (ICREA), Barcelona 08010 (Spain)

2010-12-20

309

Hydration effect on solid DNA-didecyldimethylammonium chloride complexes measured using 1H-nuclear magnetic resonance spectroscopy  

NASA Astrophysics Data System (ADS)

Complexes like the studied DNA and didecyldimethylammonium chloride are promising materials for organic electronics and photonics. Water content in this material as the solid state is a key factor for its electronics properties and microstructure. DNA complex was subjected to controlled hydration from gaseous phase and next studied by 1H-nuclear magnetic resonance spectroscopy. Variations of spin-spin and spin-lattice relaxation times as a function of hydration level are reported. Formation of tightly and loosely bound water fractions at rehydration process is discussed.

Nizio?, J.; Hara?czyk, H.; Kobierski, J.; Hebda, E.; Pielichowski, J.; Ostachowicz, B.

2013-10-01

310

Superconducting Magnetic Properties and Granularity in Single and Polycrystalline  

NASA Astrophysics Data System (ADS)

In this work the magnetic shielding properties of both polycrystalline sintered and powdered YBa _2Cu_3O_{7-delta} and DyBa_2Cu_3O_{7-delta } as well as single crystalline YBa _2Cu_3O_{7-delta} are investigated as a function of applied magnetic field and temperature. The tools used are ac susceptibility and flux penetration measurements and also dc magnetization measurements. Both single-and polycrystalline specimens behave like granular materials. This is shown by measuring the magnetization and full penetration fields as a function of specimen size. At low temperatures (4.2K) full coupling of the single crystal is observed, but at 77K in high magnetic fields (4T) it seems to be completely granular. J _{c} as a function of field shows an unusual minimum at low fields, followed by a maximum at intermediate fields and finally decreasing again as a field H_{irr} < H_{c2 } is approached. H_{c2 } was determined using the reversible part of the magnetization trace. Together with H_ {c1} (which was also measured for both principal orientations) a set of superconducting parameters for YBa_2Cu_3O_{7-delta } was derived.

Daeumling, Manfred Franz

311

A Study of the Magnetic and Thermal Properties of Ln  

SciTech Connect

Crystal structures, and magnetic, electric, and thermal properties of fluorite related compounds Ln{sub 3}RuO{sub 7} (Ln=Sm, Eu) have been investigated. For Eu{sub 3}RuO{sub 7}, a magnetic transition due to Ru{sup 5+} ions is found at T{sub N}=22.5 K on the susceptibility-temperature curve. Specific heat measurements also exhibit a {lambda}-type anomaly at the same temperature. The Moessbauer spectrum measured at 10 K shows broadening of the line corresponding to magnetic splitting. For Sm{sub 3}RuO{sub 7}, two magnetic anomalies have been observed at 10.5 and 22.5 K from its magnetic susceptibility measurements. Below 22.5 K Ru{sup 5+} ions are antiferromagnetically coupled, and when the temperature is decreased through 10.5 K the ordering of Sm{sup 3+} ions occurs rapidly. Specific heat measurements show first-order transition peaks at T=280 and 190 K for Eu{sub 3}RuO{sub 7} and Sm{sub 3}RuO{sub 7}, respectively. T he results of magnetic susceptibility and electric resistivity measurements indicate that these transitions are structural phase transitions.

Harada, Daijitsu; Hinatsu, Yukio

2001-05-01

312

A reentrant phenomenon in magnetic and dielectric properties of Dy2BaNiO5 and an intriguing influence of external magnetic field.  

PubMed

We report that the spin-chain compound Dy2BaNiO5, recently proven by us to exhibit magnetoelectric coupling below its Néel temperature (TN) of 58 K, exhibits strong frequency-dependent behavior in ac magnetic susceptibility and complex dielectric properties at low temperatures (<10?K), mimicking the 'reentrant' multiglass phenomenon. Such a behavior is not known among undoped compounds. A new finding in the field of multiferroics is that the characteristic magnetic feature at low temperatures moves towards higher temperatures in the presence of a magnetic field (H), whereas the corresponding dielectric feature shifts towards lower temperatures with H, unlike the situation near TN. This observation indicates that the alignment of spins by external magnetic fields tends to inhibit glassy-like slow electric-dipole dynamics, at least in this system, possibly arising from peculiarities in the magnetic structure. PMID:24722401

Basu, Tathamay; Paulose, P L; Iyer, K K; Singh, K; Mohapatra, N; Chowki, S; Gonde, B; Sampathkumaran, E V

2014-04-30

313

Density Functional Theory Calculations on Magnetic Properties of Actinide Compounds  

SciTech Connect

We have performed a detailed analysis of the magnetic (collinear and non-collinear) order and the atomic and electron structures of UO2, PuO2 and UN on the basis of density functional theory with the Hubbard electron correlation correction (DFT + U). We have shown that the 3-k magnetic structure of UO2 is the lowest in energy for the Hubbard parameter value of U = 4.6 eV (and J = 0.5 eV) consistent with experiments when Dudarev’s formalism is used. In contrast to UO2, UN and PuO2 show no trend for a distortion towards rhombohedral structure and, thus, no complex 3-k magnetic structure is to be anticipated in these materials.

Gryaznov, D.; Heifets, Eugene; Sedmidubsky, David

2010-08-16

314

Influence of magnetic electrodes thicknesses on the transport properties of magnetic tunnel junctions with perpendicular anisotropy  

NASA Astrophysics Data System (ADS)

The influence of the bottom and top magnetic electrodes thicknesses on both perpendicular anisotropy and transport properties is studied in (Co/Pt)/Ta/CoFeB/MgO/FeCoB/Ta magnetic tunnel junctions. By carefully investigating the relative magnetic moment of the two electrodes as a function of their thicknesses, we identify and quantify the presence of magnetically dead layers, likely localized at the interfaces with Ta, that is, 0.33 nm for the bottom electrode and 0.60 nm for the top one. Critical thicknesses (spin-reorientation transitions) are determined as 1.60 and 1.65 nm for bottom and top electrodes, respectively. The tunnel magnetoresistance ratio reaches its maximum value, as soon as both effective (corrected from dead layer) electrode thicknesses exceed 0.6 nm.

Cuchet, Léa; Rodmacq, Bernard; Auffret, Stéphane; Sousa, Ricardo C.; Dieny, Bernard

2014-08-01

315

Journal of Magnetism and Magnetic Materials 267 (2003) 347356 Magnetic and structural properties and crystallization behavior  

E-print Network

-consistent magnetization analysis is presented which for the first time in FINEMET materials correlates a macroscopic rights reserved. Keywords: Macroscopic and atomistic magnetization analysis; Chemical partitioning model address: Department of Socio-Environmental Energy Science, Graduate School of Energy Science, Kyoto

McHenry, Michael E.

316

Electronic structures and magnetic properties of iron nitrides  

NASA Astrophysics Data System (ADS)

To investigate the effect of nitrogen atoms on the magnetic properties of iron atoms, band calculations were carried out for Fe 4N and Fe 16N 2 by the Linearized Muffin Tin Orbitals (LMTO) method within the framework of the Local-Spin-Density (LSD) approximation. It was found that the magnetic moments of iron atoms near to nitrogen atoms decrease on the 3c sites of Fe 4N and on the 4e sites of Fe 16N 2, while the iron atoms far from nitrogen atoms have giant magnetic moments on the 1a sites of Fe 4N and on the 4d sites of Fe 16N 2.

Ishida, S.; Kitawatase, K.

1992-02-01

317

Transport and magnetic properties of BaVSe3  

NASA Astrophysics Data System (ADS)

We report a comprehensive study of transport, magnetotransport, and magnetic properties of single crystals of BaVSe3 . The paramagnetic metal-ferromagnetic metal transition at 43 K was followed as a function of pressure by measuring the electrical resistivity and the thermoelectric power. The exponent of the low-temperature power-law dependence of the resistivity increases with pressure. The effective magnetic moment obtained from magnetic susceptibility in the paramagnetic regime is ?eff=1.40?B . The study was completed by band-structure calculations based on density-functional theory both at ambient and high pressures. Transport coefficients of BaVSe3 resemble the high-pressure phase of BaVS3 , which suggest that the replacement of sulfur with selenium can be viewed as chemical pressure.

Akrap, Ana; Stevanovi?, Vladan; Herak, Mirta; Miljak, Marko; Bariši?, Neven; Berger, Helmuth; Forró, László

2008-12-01

318

Magnetic properties of X-ray bright points. [in sun  

NASA Technical Reports Server (NTRS)

Using high-resolution Kitt Peak National Observatory magnetograms and sequences of simultaneous S-054 soft X-ray solar images, the properties of X-ray bright points (XBP) and ephemeral active regions (ER) are compared. All XBP appear on the magnetograms as bipolar features, except for very recently emerged or old and decayed XBP. The separation of the magnetic bipoles is found to increase with the age of the XBP, with an average emergence growth rate of 2.2 plus or minus 0.4 km per sec. The total magnetic flux in a typical XBP living about 8 hr is found to be about two times ten to the nineteenth power Mx. A proportionality is found between XBP lifetime and total magnetic flux, equivalent to about ten to the twentieth power Mx per day of lifetime.

Golub, L.; Krieger, A. S.; Harvey, J. W.; Vaiana, G. S.

1977-01-01

319

Enhancement of the magnetic properties of Al/La multiferroic  

NASA Astrophysics Data System (ADS)

Nanosized multiferroic La1-xAlxFeO3 (0.00?x?0.20) samples were successfully synthesized by the citrate technique without subsequent heat treatment. All the prepared samples revealed single phase orthorhombic structure of space group Pbnm. XRD data revealed that the lattice parameters (a) decrease with increasing Al content. The magnetic susceptibility (?M) was enhanced significantly from 0.36 to 0.68 emu/g mole from LaFeO3 to La0.8Al0.2FeO3 respectively. The values of magnetization (M) and effective magnetic moment (?eff) were found to increase with increasing Al content. The enhancement of the physical and structural properties of the investigated multiferroic is possibly due to the changes in the lattice parameters, tolerance factor as well as crystallite size caused by aluminum substitution.

Ahmed, M. A.; Okasha, N.; Hussein, B.

2012-08-01

320

Magnetic property of the precursor of polyacenic semiconductive material  

NASA Astrophysics Data System (ADS)

In association with the studies of recent organic ``ferromagnets,'' measurements of magnetic properties including the magnetization, the magnetic susceptibility, and the electron spin resonance of the precursor of the polyacenic semiconductive material prepared from pyrolytic treatment of phenol-formaldehyde resin at a low temperature (220°C) have been carried out. The overall results have suggested that, in the skeleton of this precursor, there are structurally some parts containing the parallel-spin alignments with the averaged spin multiplicity S of unity or even higher in addition to a small amount of general isolated spins with S=1/2. Triphenylmethyl radicals possibly appearing in the skeleton have been deduced to be responsible for the origin of such peculiar spin alignments.

Kobashi, Masahiro; Sanekata, Hideki; Tanaka, Kazuyoshi; Yamabe, Tokio; Yamauchi, Jun; Yata, Shizukuni

1991-07-01

321

UNIVERSITY of CALIFORNIA EFFECT OF BISMUTH DOPING ON THE MAGNETIC PROPERTIES  

E-print Network

UNIVERSITY of CALIFORNIA SANTA CRUZ EFFECT OF BISMUTH DOPING ON THE MAGNETIC PROPERTIES OF RARE of Bismuth Doping on the Magnetic Properties of Rare-Earth Orthoferrites by Kelsey A. Collier The purpose of this experiment was to investigate the magnetic properties of bismuth-doped rare-earth orthoferrites, prompted

Belanger, David P.

322

Magnetic and elastic properties of CoFe2O4- polydimethylsiloxane magnetically oriented elastomer nanocomposites  

NASA Astrophysics Data System (ADS)

Magnetic elastic structured composites were prepared by using CoFe2O4 ferromagnetic and superparamagnetic nanoparticles as fillers in polydimethylsiloxane (PDMS) matrixes, which were cured in the presence of a uniform magnetic field. Cobalt-iron oxide nanoparticles of three different average sizes (between 2 and 12 nm) were synthesized and characterized. The smallest nanoparticles presented superparamagnetic behavior, with a blocking temperature of approximately 75 K, while larger particles are already blocked at room temperature. Macroscopically structured-anisotropic PDMS-CoFe2O4 composites were obtained when curing the dispersion of the nanoparticles in the presence of a uniform magnetic field (0.3 T). The formation of the particle's chains (needles) orientated in the direction of the magnetic field was observed only when loading with the larger magnetically blocked nanoparticles. The SEM images show that the needles are formed by groups of nanoparticles which retain their original average size. The Young's moduli of the structured composites are four times larger when measured along the oriented needles than in the perpendicular direction. Magnetization (VSM) and ferromagnetic resonance curves of the structured composites were determined as a function of the relative orientation between the needles and the probe field. The remanence magnetization was 30% higher when measured parallel to the needles, while the coercive field remains isotropic. These observations are discussed in terms of the individual nanoparticle's properties and its aggregation in the composites.

Soledad Antonel, P.; Jorge, Guillermo; Perez, Oscar E.; Butera, Alejandro; Gabriela Leyva, A.; Martín Negri, R.

2011-08-01

323

Magnetic Properties of Avanhandava H4 Meteorite Chondrules  

NASA Astrophysics Data System (ADS)

The magnetic properties of twenty individual chondrules from Avanhandava chondritic (H4) meteorite fall were studied. Magnetic hysteresis measurements and isothermal remanent magnetization (IRM) acquisition experiments reveal two populations of chondrules with different magnetic properties within the meteorite. The first group shows magnetically hard behavior with coercivities (Hc) ranging between 20 and 60 mT and IRM acquisition curves displaying two distinct coercivity components. The low coercivity component is acquired at fields < 250 mT, while the high coercivity component is acquired mostly between 400 and 1200 mT. This high coercivity component is also apparent in first order reversal curve (FORC) diagrams. The median destructive field (MDF) for samples' saturation isothermal remanent magnetization (SIRM) was ˜ 160 mT. The second group shows magnetically soft behavior, with Hc values below 5 mT and IRM acquisition curves showing only a single low coercivity component acquired at fields < 250 mT. Additionally, there are no high coercivity components observed in the FORC diagrams of these chondrules, and MDFs are generally lower than those of the first group. The natural remanent magnetization (NRM) of the chondrules is weak (˜ 10-2 - 10-1 mAm2/kg). Surprisingly, there is no correlation between the stability of the NRM and the presence of the high coercivity component. The NRM directions of individual chondrules define a random distribution. Alternating field demagnetization reveals one or two stable components. Some chondrules display erratic variations in intensity during demagnetization, which can be caused by the presence of multi-domain grains. While the low coercivity component is likely related to the presence of multi-domain kamacite, the mineralogy of the high coercivity fraction is uncertain. Experiments are underway to identify the magnetic carriers of the two coercivity fractions. This information will be essential for isolating the NRM component held by the high coercivity carriers, which may be related to processes such as original chondrule formation, subsequent coalescence into a parent meteorite body, and/or shock events.

Kohout, T.; Pesonen, L.; Feinberg, J.

2009-05-01

324

Fermi surface, magnetic, and superconducting properties in actinide compounds  

NASA Astrophysics Data System (ADS)

The de Haas-van Alphen effect, which is a powerful method to explore Fermi surface properties, has been observed in cerium, uranium, and nowadays even in neptunium and plutonium compounds. Here, we present the results of several studies concerning the Fermi surface properties of the heavy fermion superconductors UPt3 and NpPd5Al2, and of the ferromagnetic pressure-induced superconductor UGe2, together with those of some related compounds for which fascinating anisotropic superconductivity, magnetism, and heavy fermion behavior has been observed. xml:lang="fr"

?nuki, Yoshichika; Settai, Rikio; Haga, Yoshinori; Machida, Yo; Izawa, Koichi; Honda, Fuminori; Aoki, Dai

2014-08-01

325

Nonlinear optical properties of the magnetized QED Vacuum  

Microsoft Academic Search

New processes associated with the nonlinear optical properties of the\\u000aelectromagnetic vacuum, as predicted by quantum electrodynamics are described.\\u000aWe consider the presence of a static and a rotating magnetic field. The cases\\u000aof harmonic generation and two different types of sideband cascades are\\u000aconsidered. First order and second order effects with respect to the external\\u000amagnetic field are discussed

J. T. Mendonca

2007-01-01

326

Magnetic and transport properties of magnetite thin films  

Microsoft Academic Search

Magnetite (Fe3O4) films were prepared by DC reactive magnetron sputtering at various oxygen partial pressures with the ratio ? of oxygen to argon changing from 0.50:50 to 0.70:50 at room temperature, and then the Fe3O4 films were annealed at 480°C for 80min. The properties of the films were studied by X-ray diffraction, scanning electron microscopy, magnetic hysteresis loops, magnetoresistance (MR),

Guomin Zhang; Chongfei Fan; Liqing Pan; Fengping Wang; Ping Wu; Hong Qiu; Yousong Gu; Yue Zhang

2005-01-01

327

Photometric properties of magnetic elements: resolved and unresolved features  

E-print Network

We investigate, by numerical simulations, the photometric signature of magnetic flux tubes in the solar photosphere. We show that the observed contrast profiles are determined not only by the physical properties of the tube and its surroundings, but also by the peculiarities of the observations, including the line/continuum formation height and the spatial and spectral resolution. The aim is to understand these contributions well enough so that multi-wavelength observations can begin to disentangle them.

Serena Criscuoli

2007-12-19

328

Electric and Magnetic Properties of Co-filled Carbon Nanotube  

NASA Astrophysics Data System (ADS)

We investigate the electric and magnetic properties of a (3,3) single-walled carbon nanotube filled with a linear Co nanowire. We carry out first-principle calculations based on the spin-polarized density functional theory, and find that in the stable structure, it shows half metallic ferromagnetic behavior, i.e., the majority-spin electrons show metallic behavior while the minority-spin electrons have a semiconducting bandgap.

Rahman, Md. Mahmudur; Kisaku, Masanori; Kishi, Tomoya; Roman, Tanglaw Abat; Diño, Wilson Agerico; Nakanishi, Hiroshi; Kasai, Hideaki

2005-02-01

329

Magnetic properties of multi-walled carbon nanotubes encapsulated  

Microsoft Academic Search

The experimental apparatus by self-designed was used, Fe\\/Co particles encapsulated in multi-walled carbon nanotubes (MWCNTs) were prepared by the method of anodic arc discharging plasma. The products were characterized by transmission election microscopy, Raman spectroscopy and X-ray diffractometry. The magnetic properties of the products were characterized with vibration sample magnetometer. The TEM results show that MWCNTs have little impurity and

LI Wei-xue

330

Dielectric, ferroelectric, magnetic, and magnetoelectric properties of multiferroic laminated composites  

Microsoft Academic Search

Multiferroic laminated composites consisting of lead-zirconate titanate (PZT)\\/polyvinylidene-fluoride (PVDF) particulate composite layers and Tb-Dy-Fe alloy (Terfenol-D)\\/PVDF particulate composite layers, prepared by a simple hot-molding technique, were reported. In the laminated composites, the polymer PVDF is inert and used just as a binder. The measured dielectric, ferroelectric, magnetic, and magnetoelectric properties demonstrate strong dependence on volume fraction f of the PVDF

N. Cai; J. Zhai; C.-W. Nan; Y. Lin; Z. Shi

2003-01-01

331

Magnetic properties of the ferrimagnetic glass-ceramics for hyperthermia  

NASA Astrophysics Data System (ADS)

Magnetic materials play a key-role in magnetic induction hyperthermia for the treatment of cancer. In this paper, we analyse the magnetic properties of ferrimagnetic glass-ceramics with the composition in the system SiO 2-Na 2O-CaO-P 2O 5-FeO-Fe 2O 3, as a function of the melting temperature. These materials were obtained by melting of commercial reagents in the temperature range of 1400-1550 °C. Room-temperature magnetic measurements were performed by means of a vibrating sample magnetometer at room temperature. The power loss was determined from calorimetric measurements, using a magnetic induction furnace. The highest power loss (61 W/g) has been obtained for samples melted at 1500 °C. The heat generation of the ferrimagnetic glass-ceramics prepared by two different synthesis methods (traditional melting and coprecipitation-derived) will be compared. These materials are expected to be useful in the localised treatment of cancer.

Bretcanu, O.; Verné, E.; Cöisson, M.; Tiberto, P.; Allia, P.

2006-10-01

332

Cryogenic properties of dispersion strengthened copper for high magnetic fields  

NASA Astrophysics Data System (ADS)

Cold deformed copper matrix composite conductors, developed for use in the 100 tesla multi-shot pulsed magnet at the National High Magnetic Field Laboratory (NHMFL), have been characterized. The conductors are alumina strengthened copper which is fabricated by cold drawing that introduces high dislocation densities and high internal stresses. Both alumina particles and high density of dislocations provide us with high tensile strength and fatigue endurance. The conductors also have high electrical conductivities because alumina has limited solubility in Cu and dislocations have little scattering effect on conduction electrons. Such a combination of high strength and high conductivity makes it an excellent candidate over other resistive magnet materials. Thus, characterization is carried out by tensile testing and fully reversible fatigue testing. In tensile tests, the material exceeds the design criteria parameters. In the fatigue tests, both the load and displacement were measured and used to control the amplitude of the tests to simulate the various loading conditions in the pulsed magnet which is operated at 77 K in a non-destructive mode. In order to properly simulate the pulsed magnet operation, strain-controlled tests were more suitable than load controlled tests. For the dispersion strengthened coppers, the strengthening mechanism of the aluminum oxide provided better tensile and fatigue properties over convention copper.

Toplosky, V. J.; Han, K.; Walsh, R. P.; Swenson, C. A.

2014-01-01

333

Magnetic properties in an ash flow tuff with continuous grain size variation: a natural reference for magnetic particle granulometry  

USGS Publications Warehouse

The Tiva Canyon Tuff contains dispersed nanoscale Fe-Ti-oxide grains with a narrow magnetic grain size distribution, making it an ideal material in which to identify and study grain-size-sensitive magnetic behavior in rocks. A detailed magnetic characterization was performed on samples from the basal 5 m of the tuff. The magnetic materials in this basal section consist primarily of (low-impurity) magnetite in the form of elongated submicron grains exsolved from volcanic glass. Magnetic properties studied include bulk magnetic susceptibility, frequency-dependent and temperature-dependent magnetic susceptibility, anhysteretic remanence acquisition, and hysteresis properties. The combined data constitute a distinct magnetic signature at each stratigraphic level in the section corresponding to different grain size distributions. The inferred magnetic domain state changes progressively upward from superparamagnetic grains near the base to particles with pseudo-single-domain or metastable single-domain characteristics near the top of the sampled section. Direct observations of magnetic grain size confirm that distinct transitions in room temperature magnetic susceptibility and remanence probably denote the limits of stable single-domain behavior in the section. These results provide a unique example of grain-size-dependent magnetic properties in noninteracting particle assemblages over three decades of grain size, including close approximations of ideal Stoner-Wohlfarth assemblages, and may be considered a useful reference for future rock magnetic studies involving grain-size-sensitive properties.

Till, J.L.; Jackson, M.J.; Rosenbaum, J.G.; Solheid, P.

2011-01-01

334

Observation of metal ion dependent packing structures and magnetic behaviors of metal-bis-1, 2-dithiolene complexes.  

PubMed

The crystal structures and magnetic properties were investigated experimentally and theoretically for two S = ½ spin chain complexes, which consist of [M(mnt)(2)](-) (M = Pt for 1 or Pd for 2) with 1-(4'-bromo-2'-flurobenzyl)-4-aminopyridinium (1-BrFBz-4-NH(2)Py(+)). The 1-BrFBz-4-NH(2)Py(+) cations exhibit different molecular conformations and arrangements in 1 and 2; the [M(mnt)(2)](-) anions form regular stacks in 1, whereas they form irregular stacks in 2. In addition, the intermolecular interactions between the [M(mnt)(2)](-) anions and cations are also different from each other in the crystals of 1 and 2. Complex 1 shows the magnetic characteristics of a low-dimensional antiferromagnetic coupling spin system with a spin-Peierls-type transition around 7 K, and complex 2 exhibits diamagnetism over the temperature range of 5-300 K. Theoretical analyses, based on the calculations for the charge density distributions of [Pt(mnt)(2)](-) and [Pd(mnt)(2)](-) anions and the magnetic exchange constants within the anion spin chains, addressed the diverse molecular alignments in the crystals of 1 and 2 and distinct magnetic behaviors between 1 and 2. PMID:22237662

Pei, Wen-Bo; Wu, Jian-Sheng; Ren, Xiao-Ming; Tian, Zheng-Fang; Xie, Jingli

2012-03-01

335

Magnetic properties of geometrically frustrated SrGd2O4  

NASA Astrophysics Data System (ADS)

A study of the magnetic properties of the frustrated rare-earth oxide SrGd2O4 has been completed using bulk property measurements of magnetization, susceptibility, and specific heat on single-crystal samples. Two zero-field phase transitions have been identified at 2.73 and 0.48 K. For the field H, applied along the a and b axes, a single boundary is identified that delineates the transition from a low-field, low-temperature magnetically ordered regime to a high-field, high-temperature paramagnetic phase. Several field-induced transitions, however, have been observed with H ?c. The measurements have been used to map out the magnetic phase diagram of SrGd2O4, suggesting that it is a complex system with several competing magnetic interactions. The low-temperature magnetic behavior of SrGd2O4 is very different compared to the other SrL2O4 (L = Lanthanide) compounds studied so far, even though all of the SrL2O4 compounds are isostructural, with the magnetic ions forming a low-dimensional lattice of zigzag chains that run along the c axis. The differences are likely to be due to the fact that in the ground state Gd3+ has zero orbital angular momentum and therefore the spin-orbit interactions, which are crucial for other SrL2O4 compounds, can largely be neglected. Instead, given the relatively short Gd3+-Gd3+ distances in SrGd2O4, dipolar interactions must be taken into account for this antiferromagnet alongside the Heisenberg exchange terms.

Young, O.; Balakrishnan, G.; Lees, M. R.; Petrenko, O. A.

2014-09-01

336

Magnetic blocking in extended metal atom chains: a pentachromium(ii) complex behaving as a single-molecule magnet.  

PubMed

Compound [Cr5(tpda)4Cl2] (H2tpda = N(2),N(6)-di(pyridin-2-yl)pyridine-2,6-diamine), an Extended Metal Atom Chain complex featuring two quadruply-bonded {Cr2} units, exhibits field-induced slow relaxation of its magnetization arising from the terminal chromium(ii) ion and provides the first example of a chromium(ii)-based Single-Molecule Magnet. PMID:25336023

Cornia, A; Rigamonti, L; Boccedi, S; Clérac, R; Rouzières, M; Sorace, L

2014-11-01

337

Influence of soft magnetic underlayers on the magnetic properties of Co90Fe10 films  

NASA Astrophysics Data System (ADS)

The structure and magnetic properties of thin Co90Fe10 films have been studied to determine how different soft magnetic underlayers (Fe81B13.5Si3.5C2 (Metglas) and Ni81Fe19) influence these properties with the aim to achieve soft fcc Co90Fe10 films with large magnetostriction constants. The thickness of the Co90Fe10 films was 25 nm with the thickness of the magnetic underlayer ranging from 15 nm to 35 nm. The effect of applying a magnetic field during the growth of both layers was also investigated. From X-ray diffraction, it was found that the Co90Fe10 films grown on NiFe had lower in-plane stresses compared to those grown on silicon and Metglas. While the coercive fields of all the Co90Fe10 films were smaller than the monolith Co90Fe10 film, the magnetostriction constants were strongly dependent on the underlayer they were grown on. Thus it is possible to tune the magnetostriction constant of the Co90Fe10 film to be positive or negative by selecting the correct soft magnetic underlayer.

Caruana Finkel, A.; Reeves-McLaren, N.; Morley, N. A.

2014-05-01

338

Metal nanoparticle fluids with magnetically induced electrical switching properties  

NASA Astrophysics Data System (ADS)

We report the successful preparation of solvent-free metal nanoparticle (NP) fluids with multiple-functionalities, such as rheological properties, magnetism, ionic conductivity, and electrical properties, allowing for facile synthesis and mass production. The gold nanoparticles (AuNPs) used in this study were synthesized using tetraoctylammonium bromide (TOABr) in toluene and then directly phase-transferred to solvent-free low-molecular-weight (Mw) imidazolium-type ionic liquid media containing thiol groups (i.e., IL-SH). Magnetic metal fluids (i.e., MIL-SH-AuNPs) were prepared by the addition of FeCl3 powder to metal fluids (i.e., IL-SH-AuNPs). These fluids showed relatively high ionic and electrical conductivities compared with those of conventional metal NP fluids based on organic ILs with high Mw. Furthermore, it was demonstrated that these fluids could be used as electric switches operated using an external magnetic field in organic media.We report the successful preparation of solvent-free metal nanoparticle (NP) fluids with multiple-functionalities, such as rheological properties, magnetism, ionic conductivity, and electrical properties, allowing for facile synthesis and mass production. The gold nanoparticles (AuNPs) used in this study were synthesized using tetraoctylammonium bromide (TOABr) in toluene and then directly phase-transferred to solvent-free low-molecular-weight (Mw) imidazolium-type ionic liquid media containing thiol groups (i.e., IL-SH). Magnetic metal fluids (i.e., MIL-SH-AuNPs) were prepared by the addition of FeCl3 powder to metal fluids (i.e., IL-SH-AuNPs). These fluids showed relatively high ionic and electrical conductivities compared with those of conventional metal NP fluids based on organic ILs with high Mw. Furthermore, it was demonstrated that these fluids could be used as electric switches operated using an external magnetic field in organic media. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00653k

Kim, Younghoon; Cho, Jinhan

2013-05-01

339

Formal verification of complex properties on PLC programs  

E-print Network

Formal verification has become a recommended practice in the safety-critical application areas. However, due to the complexity of practical control and safety systems, the state space explosion often prevents the use of formal analysis. In this paper we extend our former verification methodology with effective property preserving reduction techniques. For this purpose we developed general rule-based reductions and a customized version of the Cone of Influence (COI) reduction. Using these methods, the verification of complex requirements formalised with temporal logics (e.g. CTL, LTL) can be orders of magnitude faster. We use the NuSMV model checker on a real-life PLC program from CERN to demonstrate the performance of our reduction techniques.

Darvas, D; Voros, A; Bartha, T; Blanco Vinuela, E; Gonzalez Suarez, V M

2014-01-01

340

Magnetic susceptibility and magnetization properties of asymmetric nuclear matter under a strong magnetic field  

E-print Network

We study the effect of a strong magnetic field on the proton and neutron spin polarization and magnetic susceptibility of asymmetric nuclear matter within a relativistic mean-field approach. It is shown that magnetic fields $B \\sim 10^{16} - 10^{17}$ G have already noticeable effects on the range of densities of interest for the study of the crust of a neutron star. Although the proton susceptibility is larger for weaker fields, the neutron susceptibility becomes of the same order or even larger for small proton fractions and subsaturation densities for $B > 10^{16}$ G. We expect that neutron superfluidity in the crust will be affected by the presence of magnetic fields.

Rabhi, A; Providência, C; Vidaña, I

2014-01-01

341

Magnetic susceptibility and magnetization properties of asymmetric nuclear matter under a strong magnetic field  

E-print Network

We study the effect of a strong magnetic field on the proton and neutron spin polarization and magnetic susceptibility of asymmetric nuclear matter within a relativistic mean-field approach. It is shown that magnetic fields $B \\sim 10^{16} - 10^{17}$ G have already noticeable effects on the range of densities of interest for the study of the crust of a neutron star. Although the proton susceptibility is larger for weaker fields, the neutron susceptibility becomes of the same order or even larger for small proton fractions and subsaturation densities for $B > 10^{16}$ G. We expect that neutron superfluidity in the crust will be affected by the presence of magnetic fields.

A. Rabhi; M. A. Pérez-García; C. Providência; I. Vidaña

2014-10-10

342

Direct observation of dynamics of single spinning dust grains in weakly magnetized complex plasma  

SciTech Connect

The rotational dynamics of single dust grains in a weak magnetic field is investigated on a kinetic level. Experiments reveal spin-up of spherical dust grains and alignment of their magnetic moments parallel to the magnetic induction vector. The angular velocity of spinning prolate grains varies as magnetic induction increases to 250 G. Spinning dust grains are found to flip over only when the magnetic field magnitude is changing. The results demonstrate that dusty plasma has paramagnetic properties. Qualitative interpretations are proposed to explain newly discovered phenomena.

Dzlieva, E. S.; Karasev, V. Yu., E-mail: plasmadust@yandex.ru [St. Petersburg State University, Institute of Physics (Russian Federation); Petrov, O. F. [Russian Academy of Sciences, Institute for High Energy Densities, Joint Institute for High Temperatures (Russian Federation)

2012-01-15

343

Physics of complex transverse susceptibility of magnetic particulate systems Dorin Cimpoesu*  

E-print Network

Physics of complex transverse susceptibility of magnetic particulate systems Dorin Cimpoesu distributions in particulate magnetic media. So far, only thermal fluctuations and rate-dependent damped Pareti and Turilli9 experimentally verified the theory of Aharoni et al.8 which predicted that the plot

Spinu, Leonard

344

Limits on the complexity of empirical models of magnetic storm phenomena  

Microsoft Academic Search

We explore the statistical limits on the complexity of data-derived models of magnetic storm phenomena, including magnetic indices, plasmapause evolution, and outer radiation belt dynamics. Specifically, we estimate the limits on the number of free parameters justifiable by application of Occam's razor, or the rule of parsimony. These limits arise from the strong intercorrelation of geomagnetic phenomena, which decimates the

T. P. O'Brien

2006-01-01

345

Mixed (phthalocyaninato)(Schiff-base) di-dysprosium sandwich complexes. Effect of magnetic coupling on the SMM behavior.  

PubMed

Reaction between Schiff-base ligand and half-sandwich complex M(Pc)(acac) led to the isolation of new sandwich-type mixed (phthalocyaninato)(Schiff-base) di-lanthanide compounds M2(Pc)2(L)H2O (M = Dy, Gd) (1, 2) [H2Pc = metal free phthalocyanine, Hacac = acetylacetone, H2L = N,N'-bis(3-methyloxysalicylidene)benzene-1,2-diamine] with the triple-decker molecular structure clearly revealed by single crystal X-ray diffraction analysis. For the comparative studies, sandwich triple-decker analogues with pure Schiff-base ligand M2(L)3H2O (M = Dy, Gd) (3, 4) were also prepared. Dynamic magnetic measurement result reveals the single-molecule magnet (SMM) nature of the di-dysprosium derivative 1, while the static magnetic investigation over both pure and the diamagnetic diluted samples of this compound discloses the interionic ferromagnetic coupling between the two dysprosium ions, which in turn effectively suppresses the QTM and enhances the energy barrier of this SMM. Nevertheless, comparative studies over the static magnetic properties of the di-dysprosium triple-decker complexes 1 and 3 indicate the stronger magnetic coupling between the two lanthanide ions in mixed (phthalocyaninato)(Schiff-base) species than in the pure Schiff-base triple-decker analogue, suggesting the special coordination sphere around the dysprosium ions in the former compound over the latter one on the more intense inter-ionic ferromagnetic coupling. As a very small step towards understanding the structure-property relationship, the present result will be surely helpful for the design and synthesis of the multinuclear lanthanide-based SMMs with good properties. PMID:24005576

Wang, Hailong; Liu, Chenxi; Liu, Tao; Zeng, Suyuan; Cao, Wei; Ma, Qi; Duan, Chunying; Dou, Jianmin; Jiang, Jianzhuang

2013-11-21

346

Magnetic and electronic properties of NpCo2: Evidence for long-range magnetic order  

NASA Astrophysics Data System (ADS)

The magnetic and electronic properties of the cubic Laves phase intermetallic compound NpCo2 have been investigated by magnetization, specific heat, and electrical resistivity measurements. Magnetization data confirm previous results, i.e., an antiferromagneticlike order at 12.5 K and a metamagnetic transition at Bm ˜ 4.3 T at 3 K with a saturation moment of ˜0.6 ?B. Although extensive neutron diffraction studies failed to establish the nature of the antiferromagnetic order, its occurrence is confirmed by specific heat measurements that also highlight the presence of magnetic fluctuations suppressed by the application of an external field larger than Bm. The observed high value of the electronic specific heat, ?0 ˜ 330 mJ/mol K2 as T ? 0, and the minute magnetic entropy, <0.1Rln2, classify NpCo2 as an itinerant, moderately-heavy-fermion antiferromagnet. The electrical resistivity data agree with the presence of an antiferromagnetic order below Bm and suggest a non-Fermi liquid behavior at low temperature. The electronic structure of NpCo2 was examined theoretically and compared to experimental data. Local spin density approximation (LSDA) calculations show that this material is close to a magnetic instability and that ferromagnetic alignment of the Np moments is the most stable. LSDA+U calculations in the fully localized limit with U = 0 give reasonable agreement with the experimental Np moment value and their orbital and spin contributions.

Sanchez, J. P.; Griveau, J.-C.; Javorsky, P.; Colineau, E.; Eloirdi, R.; Boulet, P.; Rebizant, J.; Wastin, F.; Shick, A. B.; Caciuffo, R.

2013-04-01

347

Ln[DO3A-N-?-(pyrenebutanamido)propionate] complexes: optimized relaxivity and NIR optical properties.  

PubMed

We have proposed recently that the DO3A-N-?-(amino)propionate chelator and its amide conjugates are leads to targeted, high relaxivity, safe contrast agents for magnetic resonance imaging. In this work we illustrate further the expeditious nature and robustness of the synthetic methodologies developed by preparing the DO3A-N-(?-pyrenebutanamido)propionate chelator. Its Gd(3+) chelate retains the optimized water exchange, high stability and inertness of the parent complex. The pyrene moiety imparts concentration-dependent self-assembly properties and aggregation-sensitive fluorescence emission to the Gd(3+) complex. The Gd(3+) complex displays pyrene-centred fluorescence whilst the Yb(3+) and Nd(3+) complexes exhibit sensitized lanthanide-centred near-infrared luminescence. The aggregated form of the complex displays high relaxivity (32 mM(-1) s(-1), 20 MHz, 25 °C) thanks to simultaneous optimization of the rotational correlation time and of the water exchange rate. The relaxivity is however still limited by chelate flexibility. This report demonstrates that the DO3A-N-(?-amino)propionate chelator is a valuable platform for constructing high relaxivity CA using simple design principles and robust chemistries accessible to most chemistry labs. PMID:24343660

Ferreira, M F; Pereira, G; Martins, A F; Martins, C I O; Prata, M I M; Petoud, S; Toth, E; Ferreira, P M T; Martins, J A; Geraldes, C F G C

2014-02-28

348

Synthesis, X-ray crystal structures, thermal and electrochemical properties of thiosemicarbazidatodioxouranium(VI) complexes.  

PubMed

The stable uranyl complexes, [UO(2)(L)C(9)H(19)OH], were obtained from 3,5-dichlorosalicyl-(L(I)) and salicyl-aldehyde-S-propyl-thiosemicarbazones (L(II)) with substituted-salicylaldehyde in nonyl alcohol. The structures of the complexes have been characterized by elemental analysis, IR, (1)H NMR, conductivity, magnetic moment measurements, cyclic voltammetry, thermal gravimetric analysis and single crystal X-ray diffraction technique. The U(VI) centre is seven-coordinated in a distorted pentagonal bipyramidal geometry. The relative orientations of the nonyl alcohol and S-propyl group in the title complexes are completely different due to different crystal packing. Electrochemical behaviors of the thiosemicarbazone ligands and the uranyl complexes were studied using cyclic voltammetry and square wave voltammetry. Redox processes of the compounds are significantly influenced by the central metal ions and the nature of substituents on the thiosemicarbazones, which are important factors in controlling the redox properties. In situ spectroelectrochemical studies were employed to determine the colors and spectra of electro-generated species of the complexes. PMID:20922238

Sahin, Musa; Koca, At?f; Ozdemir, Nam?k; Dinçer, Muharrem; Büyükgüngör, Orhan; Bal-Demirci, Tülay; Ulküseven, Bahri

2010-11-14

349

Towards polymetallic lanthanide complexes as dual contrast agents for magnetic resonance and optical imaging.  

PubMed

Magnetic resonance imaging (MRI) is a popular imaging technique in medical diagnostics. With the development of contrast agents, interest in its applications has grown tremendously. Significant effort has been made in order to identify the most important parameters that enhance the relaxation efficiency of MRI probes. Taking into account the requirements for an optimal magnetic performance, different contrast agents have been synthesized and studied. Moreover, novel bimodal probes have been developed in order to exploit the high sensitivity and resolution of optical microscopy with the ability of MRI to image opaque samples. Employing this strategy enables the simultaneous visualization of the same biological structures at different resolutions and depths. Throughout this review, different approaches used to improve relaxivity, especially by increasing the molecular volume and hence the rotational tumbling time of the agent, are highlighted. Several ways to obtain bimodal contrast agents are discussed in detail. Finally, lanthanide complexes incorporating an aromatic unit permitting efficient sensitization of lanthanide luminescence in combination with the relaxometric properties of gadolinium analogues are listed. PMID:25211043

Debroye, Elke; Parac-Vogt, Tatjana N

2014-12-01

350

Magnetic exchange in binuclear copper(II) complexes with dissimilar bridging atoms  

NASA Astrophysics Data System (ADS)

Several copper(II) complexes have been prepared that use binucleating ligands to yield a coordinatively unsaturated product complex. These complexes will accept an exogenous ligand that binds to a bridging position. We have prepared two families of complexes from 5- or 7-coordinate binucleating ligands that exhibit similar magnetic effects as the exogenous bridging ligands are changed. Complexes of the 7-coordinate binucleating ligand are also especially useful as models of the active site of some binuclear copper proteins (e.g. hemocyanin). We report on our results covering a large series of complexes with exogenous bridging ligands B = Cl -, Br -, OH -, CH 3CO -2, 1,1-N -3, 1,3-N -3, ClO -4, etc. The magnetic exchange interaction for these complexes has not yet been observed to be ferromagnetic, but the magnitude of antiferromagnetic interactions range from Curie-Weiss paramagnetism (B = CH 3COO -) to diamagnetism (B = 1,3-N -3).

O'Connor, Charles J.; Sorrell, Thomas N.; Kahn, Olivier

1986-02-01

351

DFT Description of the Electronic Structure and Spectromagnetic Properties of Strongly Correlated Electronic Systems: Ni, CuI and Zn o-Dioxolene Complexes  

Microsoft Academic Search

The spectroscopic and magnetic properties of dioxolene complexes of zinc, copper and nickel were studied by DFT calculations on model complexes of formulas[(NH)M(SQ)] (M=Zn, Ni; SQ=semiquinonato) and[(NH)Cu (SQ)]+. Standard approaches such as time-dependent DFT (TDDFT), the Slater transition state (STS), and broken symmetry (BS) were found to be unable to completely account for the physical properties of the systems, and

Alessandro Bencini; Chiara Carbonera; Federico Totti

2004-01-01

352

Two-dimensional magnetic property measurement for magneto-rheological elastomer  

NASA Astrophysics Data System (ADS)

Magneto-rheological elastomer (MRE) is a new kind of smart material. Its rheological properties can be altered and controlled in a real time manner when it is applied an external magnetic field. For calculating magnetic properties of MRE material, usually Maxwell-Garnet equation is used to acquire an approximately effective permeability. This equation treats the magnetic property of particles as linear. However, when the applied magnetic field is alternating or rotating, the nonlinearity of magnetic property and magnetic hysteresis cannot be neglected. Hence, the measurement and modelling of the magnetic properties under alternating and rotating magnetic fields are essential to explore new applications of the material. This paper presents the investigation on the magnetic hysteresis properties of MRE material under one-dimensional (1-D) alternating and two-dimensional (2-D) rotating magnetic field excitations. A kind of MRE material, consisting of 70% carbonyl iron particles, 10% silicone oil, and 20% silicone rubber, was used to investigate the magnetic properties. The diameter of carbonyl iron particles is 3-5 ?m. The measurement results, such as the relations between magnetic field intensity (H) and magnetic flux density (B) under different magnetic field excitations on the MRE sample, have been obtained and analyzed. These data would be useful for design and analysis of MRE smart structures like MR dampers.

Zeng, Jianbin; Guo, Youguang; Li, Yancheng; Zhu, Jianguo; Li, Jianchun

2013-05-01

353

Analysis of the Magnetic Field Influence on the Rheological Properties of Healthy Persons Blood  

PubMed Central

The influence of magnetic field on whole blood rheological properties remains a weakly known phenomenon. An in vitro analysis of the magnetic field influence on the rheological properties of healthy persons blood is presented in this work. The study was performed on blood samples taken from 25 healthy nonsmoking persons and included comparative analysis of the results of both the standard rotary method (flow curve measurement) and the oscillatory method known also as the mechanical dynamic analysis, performed before and after exposition of blood samples to magnetic field. The principle of the oscillatory technique lies in determining the amplitude and phase of the oscillations of the studied sample subjected to action of a harmonic force of controlled amplitude and frequency. The flow curve measurement involved determining the shear rate dependence of blood viscosity. The viscoelastic properties of the blood samples were analyzed in terms of complex blood viscosity. All the measurements have been performed by means of the Contraves LS40 rheometer. The data obtained from the flow curve measurements complemented by hematocrit and plasma viscosity measurements have been analyzed using the rheological model of Quemada. No significant changes of the studied rheological parameters have been found. PMID:24078918

Nawrocka-Bogusz, Honorata

2013-01-01

354

Magnetic and magnetocaloric properties of bulk dysprosium chromite  

SciTech Connect

In this work, a polycrystalline bulk DyCrO{sub 3} sample was prepared by a solution route and the structural and magnetic properties were investigated. The phase purity and ionic valence state of the DyCrO{sub 3} sample were determined by x-ray diffraction/Raman spectroscopy and x-ray photoelectron spectroscopy, respectively. The AC and DC magnetization measurements revealed the onset of antiferromagnetic order at 146 K with an effective moment of 8.88 ?{sub B}. Isothermal magnetization measurements of this material are presented for the first time, showing a peak in the coercive field at 80 K that is explained by the competition between the paramagnetic Dy{sup 3+} and Cr{sup 3+} sublattices. DyCrO{sub 3} was found to display a large magnetocaloric effect (8.4 J/kg K) and relative cooling power (217 J/kg) at 4 T applied field, which renders DyCrO{sub 3} useful for magnetic refrigeration between 5 K and 30 K.

McDannald, A. [Material Science and Engineering, University of Connecticut, Storrs, Connecticut 06269 (United States) [Material Science and Engineering, University of Connecticut, Storrs, Connecticut 06269 (United States); Institute of Material Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Kuna, L. [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States)] [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States); Jain, M. [Institute of Material Science, University of Connecticut, Storrs, Connecticut 06269 (United States) [Institute of Material Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States)

2013-09-21

355

Nano-structured magnetic metamaterial with enhanced nonlinear properties  

PubMed Central

Nano-structuring can significantly modify the properties of materials. We demonstrate that size-dependent modification of the spin-wave spectra in magnetic nano-particles can affect not only linear, but also nonlinear magnetic response. The discretization of the spectrum removes the frequency degeneracy between the main excitation mode of a nano-particle and the higher spin-wave modes, having the lowest magnetic damping, and reduces the strength of multi-magnon relaxation processes. This reduction of magnon-magnon relaxation for the main excitation mode leads to a dramatic increase of its lifetime and amplitude, resulting in the intensification of all the nonlinear processes involving this mode. We demonstrate this experimentally on a two-dimensional array of permalloy nano-dots for the example of parametric generation of a sub-harmonic of an external microwave signal. The characteristic lifetime of this sub-harmonic is increased by two orders of magnitude compared to the case of a continuous magnetic film, where magnon-magnon relaxation limits the lifetime. PMID:22745899

Kobljanskyj, Yuri; Melkov, Gennady; Guslienko, Konstantin; Novosad, Valentyn; Bader, Samuel D.; Kostylev, Michael; Slavin, Andrei

2012-01-01

356

Magnetic properties of graphite irradiated with MeV ions  

SciTech Connect

We have studied the change in the magnetic properties produced on highly oriented pyrolytic graphite samples by irradiation of H, C, and N ions in the mega-electron-volt energy range. The use of specially made sample holders for the magnetic measurements provided high reproducibility allowing us to obtain directly the irradiation effects without any corrections or subtractions. Our results show that three magnetic phenomena are triggered by the defects produced by the irradiation, namely, Curie-type paramagnetism, ferromagnetism and an anomalous paramagnetic state that appears as precursor of the magnetic ordered state. Using SRIM simulations to estimate the amount of vacancies produced by the irradiation, the Curie-type paramagnetic response indicates an effective Bohr magneton number per nominally produced vacancy p=0.27+-0.02mu{sub B}. Direct measurements of the surface sample temperature during irradiation and the decrease in the (as-received) paramagnetic as well as ferromagnetic contributions after irradiation indicate that self-heating is one of the causes for small yield of ferromagnetism. Taking into account the hydrogen distribution in the virgin samples, the obtained results indicate that the induced ferromagnetism appears when the average vacancy distance is {approx}2 nm in the near surface region.

Ramos, M. A.; Munoz-Martin, A.; Climent-Font, A. [CMAM and Instituto de Ciencia de Materiales 'Nicolas Cabrera', Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Barzola-Quiquia, J.; Esquinazi, P. [Division of Superconductivity and Magnetism, Institut fuer Experimentelle Physik II, Universitaet Leipzig, Linnestrasse 5, D-04103 Leipzig (Germany); Garcia-Hernandez, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain)

2010-06-01

357

Role of magnetic anisotropy on the magnetic properties of Ni nanoclusters embedded in a ZnO matrix  

NASA Astrophysics Data System (ADS)

We have investigated the magnetic properties of Ni nanoaggregates produced by ion implantation in ZnO single crystals. Several deviations from classical models usually adopted to describe the magnetic properties of nanoparticle systems were found. The strain between host and Ni nanoaggregates induces a magnetic anisotropy with a preferred direction. We show that these anisotropy effects can be misinterpreted as a ferromagnetic or antiferromagnetic coupling among the nanoaggregates similar to that of an oriented, interacting nanocrystal ensemble.

Nunes, W. C.; Borges, R. P.; Cruz, M. M.; da Silva, R. C.; Wahl, U.; Cuchillo, A.; Vargas, P.; Magen, C.; Godinho, M.

2014-07-01

358

Properties of magnetic field fluctuations in boundary regions of the Earth's magnetosphere  

NASA Astrophysics Data System (ADS)

Statistical properties of magnetic field fluctuations in boundary regions of the Earth’s magnetosphere at different timescales were considered. Data with high resolution (22,5 Hz) obtained by Cluster mission from 2004 to 2010 were used. As a characteristic of the fluctuations on various time scales, changes in the shape and parameters of the probability density function and wave analysis were studied. In order for investigations of features of the probability density functions of magnetic field fluctuations we analyzed the statistical properties of the absolute value of magnetic field variations in the different regions of near earth space. Amplitude of fluctuations in the magnetosheath just after crossing bow shock exceeds in a few time amplitude of fluctuations for non-perturbed solar wind or the foreshock. The analysis of the height of maximum of the probability density functions and of the kurtosis values have shown the presence of different asymptotic modes which are characterized by different power laws. The use of the technique of probability density function for magnetic fluctuations has shown that at high frequencies the structure of turbulence differs from that in the low-frequency region. The critical scale corresponds to the scales of the Larmor radius of ions. The research of the statistical properties of boundary layers allows to determine the role of turbulent processes in the interaction of plasma flows with the magnetic obstacles, whether these are fields of planets, stars, or laboratory traps, and to reveal the actual mechanisms of the energy transformation in collisionless plasma. The work is done in the frame of complex program of NAS of Ukraine on space researches for 2012-1016, within the framework of the educational program No.2201250 “Education, Training of students, PhD students, scientific and pedagogical staff abroad” launched by the Ministry of Education and Science of Ukraine and under a partial support of the grant No. F 53.2/039.

Kozak, Liudmyla; Savin, Sergey; Lui, Anthony Tat Yin; Igor, Gala

359

Electronic and magnetic properties of Co-doped ZnO diluted magnetic semiconductor  

Microsoft Academic Search

The effect of low level Co doping (5%) on polycrystalline ZnO samples has been investigated to correlate the observed changes in their magnetic state vis à vis changes in their electronic properties. Rietveld refinement of the XRD patterns confirms single phase crystallization of the samples in the wurtzite type lattice, with no evidence of any secondary phases. The as-synthesized Co-doped

R. K. Singhal; Arvind Samariya; Y. T. Xing; Sudhish Kumar; S. N. Dolia; U. P. Deshpande; T. Shripathi; Elisa B. Saitovitch

2010-01-01

360

A nanoporous molecular magnet with reversible solvent-induced mechanical and magnetic properties  

Microsoft Academic Search

Interest in metal-organic open-framework structures has increased enormously in the past few years because of the potential benefits of using crystal engineering techniques to yield nanoporous materials with predictable structures and interesting properties. Here we report a new efficient methodology for the preparation of metal-organic open-framework magnetic structures based on the use of a persistent organic free radical (PTMTC), functionalized

Daniel Maspoch; Daniel Ruiz-Molina; Klaus Wurst; Neus Domingo; Massimilliano Cavallini; Fabio Biscarini; Javier Tejada; Concepció Rovira; Jaume Veciana

2003-01-01

361

Transport in complex magnetic geometries: 3D modelling of ergodic edge plasmas in fusion experiments  

Microsoft Academic Search

Both stellarators and tokamaks can have quite complex magnetic topologies in the plasma edge. Special complexity is introduced by ergodic effects producing stochastic domains. Conventional numerical methods from fluid dynamics are not applicable in this case. In the present paper, we discuss two alternative possibilities. Our multiple coordinate system approach (MCSA) [Phys. Plasmas 8 (2001) 916] originally developed for the

A. Runov; S. Kasilov; D. Reiter; N. McTaggart; X. Bonnin; R. Schneider

2003-01-01

362

INDEPENDENT COMPONENT ANALYSIS OF COMPLEX-VALUED FUNCTIONAL MAGNETIC RESONANCE IMAGING DATA  

E-print Network

information has a straightforward physiologic interpretation [2]. When performing an analysis of fMRI dataINDEPENDENT COMPONENT ANALYSIS OF COMPLEX-VALUED FUNCTIONAL MAGNETIC RESONANCE IMAGING DATA analysis (ICA) for separating complex- valued sources is needed for convolutive source

Adali, Tulay

363

Complex Inductance, Excess Noise, and Surface Magnetism in dc SQUIDs S. Sendelbach,1  

E-print Network

Complex Inductance, Excess Noise, and Surface Magnetism in dc SQUIDs S. Sendelbach,1 D. Hover,1 M (Received 12 May 2009; published 9 September 2009) We have characterized the complex inductance of dc SQUIDs cooled to millikelvin temperatures. The SQUID inductance displays a rich, history-dependent structure

Saffman, Mark

364

Complex magnetic interactions and charge transfer effects in highly ordered NixFe1-x nano-wires  

NASA Astrophysics Data System (ADS)

This work investigates the subtle magnetic interactions within the NixFe1-x (x=0.3, 0.5, and 1.0) nano-wires by probing spin-dependent behaviors of the two constituted elements. The wires were fabricated by electro-deposition and an anode aluminum oxide template to produce free-standing nature, and the Ni-Fe interactions were probed by x-ray magnetic spectroscopy across a BCC?FCC structural transition. The wires' magneto-structural properties were predominated by Ni, as reflected by a decrease but an increase in total magnetization and FCC x-ray intensity with increasing x, even if the Fe moment increased simultaneously. Upon annealing, a prominent charge transfer, together with the changes of spin-dependent states, took place in the Ni and Fe 3d orbitals, and a structural disordering was also obtained, for the wires at x=0.3. The charge transfer led to a local magnetic-compensation for the two elements, explaining the minor change in total magnetization for x=0.3 probed by a vibrational sample magnetometer. When x was increased to 0.5, however, the charge transfer became inactive due to persistent structural stability supported by Ni, albeit resulting in nearly invariant magnetization similar to that of x=0.3. The complexity of the Ni-Fe interactions varied with the composition and involved the modifications of the coupled magnetic, electronic and structural degrees of freedom. The study identifies the roles of Ni and Fe as unequally-influential in NixFe1-x, which provides opportunities to re-investigate the compound's properties concerning its technological applications.

Chang, Shu-Jui; Yang, Chao-Yao; Ma, Hao-Chung; Tseng, Yuan-Chieh

2013-04-01

365

Electronic structure of GdN: magnetic and structural properties  

NASA Astrophysics Data System (ADS)

The class of REN (RE=rare earth) materials has been of considerable theoretical and experimental interest due to their magnetic properties. Controversy still exists in GdN as to whether these materials are semiconducting or metallic and the nature of the magnetic ground state. We have studied GdN using LMTO-ASA, FP-LMTO, and LAPW calculations within LDA-DFT. A more proper treatment of the Gd 4f orbitals within LDA+U moves the Gd 4f away from the Fermi energy but cannot resolve whether the system is semiconducting or weakly semimetallic. However, a series of supercell calculations shows that the ground state configuration is ferromagnetic unlike most REN compounds, such as ErN, which are known to be antiferromagnetic.

Larson, P.; Lambrecht, W. R. L.

2004-03-01

366

Electrical and magnetic properties of ion-exchangeable layered ruthenates  

SciTech Connect

An ion-exchangeable ruthenate with a layered structure, K{sub 0.2}RuO{sub 2.1}, was prepared by solid-state reactions. The interlayer cation was exchanged with H{sup +}, C{sub 2}H{sub 5}NH{sub 3}{sup +}, and ((C{sub 4}H{sub 9}){sub 4}N{sup +}) through proton-exchange, ion-exchange, and guest-exchange reactions. The electrical and magnetic properties of the products were characterized by DC resistivity and susceptibility measurements. Layered K{sub 0.2}RuO{sub 2.1} exhibited metallic conduction between 300 and 13K. The products exhibited similar magnetic behavior despite the differences in the type of interlayer cation, suggesting that the ruthenate sheet in the protonated form and the intercalation compounds possesses metallic nature.

Sugimoto, Wataru [Faculty of Textile Science and Technology, Department of Fine Materials Engineering, Shinshu University, 3-15-1 Tokida, Ueda 386-8567 (Japan)]. E-mail: wsugi@shinshu-u.ac.jp; Omoto, Masashi [Faculty of Textile Science and Technology, Department of Fine Materials Engineering, Shinshu University, 3-15-1 Tokida, Ueda 386-8567 (Japan); Yokoshima, Katsunori [Faculty of Textile Science and Technology, Department of Fine Materials Engineering, Shinshu University, 3-15-1 Tokida, Ueda 386-8567 (Japan); Murakami, Yasushi [Faculty of Textile Science and Technology, Department of Fine Materials Engineering, Shinshu University, 3-15-1 Tokida, Ueda 386-8567 (Japan); Takasu, Yoshio [Faculty of Textile Science and Technology, Department of Fine Materials Engineering, Shinshu University, 3-15-1 Tokida, Ueda 386-8567 (Japan)

2004-12-01

367

Magnetic properties of sputtered Permalloy/molybdenum multilayers  

SciTech Connect

In this work, we report the magnetic properties of sputtered Permalloy (Py: Ni{sub 80}Fe{sub 20})/molybdenum (Mo) multilayer thin films. We show that it is possible to maintain a low coercivity and a high permeability in thick sputtered Py films when reducing the out-of-plane component of the anisotropy by inserting thin film spacers of a non-magnetic material like Mo. For these kind of multilayers, we have found coercivities which are close to those for single layer films with no out-of-plane anisotropy. The coercivity is also dependent on the number of layers exhibiting a minimum value when each single Py layer has a thickness close to the transition thickness between Neel and Bloch domain walls.

Romera, M.; Ciudad, D.; Maicas, M.; Aroca, C. [ISOM and Dpto. Fisica Aplicada, E.T.S.I. Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, Madrid 28040 (Spain); Ranchal, R. [Dpto. Fisica de Materiales, Facultad CC. Fisicas, Universidad Complutense de Madrid, Ciudad Universitaria s/n, Madrid 28040 (Spain)

2011-10-15

368

Electronic, magnetic and spectroscopic properties of manganese nanostructures  

NASA Astrophysics Data System (ADS)

This paper presents a review of the electronic, magnetic and spectroscopic properties of manganese (Mn)-based nanostructures. In the last few years a variety of techniques have been used to prepare mesoscopic transition-metal islands and novel effects associated with the electronic structure in nanoscale systems have been reported. Mn in the atomic configuration possesses a moment as high as 5?B so it should be very interesting to dope semiconductors with Mn for spin injection or to use Mn itself for permanent magnets. In this paper the introduction (section 1) focuses mainly on metallic Mn nanostructures which are the core of this review. Nevertheless we try to present a general overview of various kinds of Mn structures as well as several theoretical methods with their own limitations to handle the corresponding problems. More precisely, section 2 outlines a variety of bulk, surface, interface and cluster structures with their resulting magnetism as far as Mn is concerned. Actually, in these past two decades, considerable interest has been devoted to Mn nanostructures deposited on various metallic substrates (section 3). Because of its exotic structural and magnetic properties, Mn is indeed an interesting candidate for ultra-thin film growth as it is expected to accept different local configurations. Experimentally, one may attempt to stabilize normally high-temperature phases of Mn by epitaxial growth on a suitable substrate. Specifically, we shall point out the frequently occurring, important situation of magnetically stabilized surface alloys. Next (section 4) we first focus on spectroscopic properties of Mn compounds as well as Mn adsorbates upon graphite and other substrates both experimentally and theoretically. Moreover, we recall a few remarks about Mn impurities with respect to the Kondo problem and also with respect to semiconductors and spintronics. In the latter field, practical applications actually require room-temperature Mn ferromagnetism which is not that easy to obtain. Finally, in section 5, we point out that a given Mn nanostructure generally exhibits a non-collinear (NCL) structure which is often the most stable one among all the collinear and NCL ones. This fact explains why constrained collinear calculations have often disagreed with the corresponding experimental data. Section 6 is devoted to a short discussion where we recall a few important points that have been developed in this paper.

Demangeat, C.; Parlebas, J. C.

2002-11-01

369

The hard-magnetic properties of rare earth-transition metal alloys  

Microsoft Academic Search

The intermetallic phases formed between the rare earth metals (R) and the elements of the 3-d transition series are a large group of new substances with interesting magnetic properties. They have been studied intensely in the last decade. Their properties are reviewed with a view toward their usefulness for permanent magnets. Some aspects of the recently developed magnets based on

KARL J. STRNAT

1972-01-01

370

Biomonitoring of traffic air pollution in Rome using magnetic properties of tree leaves  

Microsoft Academic Search

We report a biomonitoring study of air pollution in Rome based on the magnetic properties of tree leaves.In a first step, magnetic properties of leaves from different tree species from the same location were compared. It was observed that leaves of evergreen species, like Quercus ilex, present much higher magnetic intensities than those of deciduous species, like Platanus sp., suggesting

Eva Moreno; Leonardo Sagnotti; Jaume Dinarès-Turell; Aldo Winkler; Antonio Cascella

2003-01-01

371

Magnetic field properties in a birdcage coil P. Boissoles and G. Caloz  

E-print Network

Magnetic field properties in a birdcage coil P. Boissoles and G. Caloz March 15, 2006 Abstract Radiofrequency magnetic fields used in MRI experiments have to sat- isfy specific properties. First, they need they generate an adequate homogeneous radiofrequency magnetic field. Since then several studies have used

Boyer, Edmond

372

Average properties of the magnetic reconnection ion diffusion region in the Earth's magnetotail: The 20012005 Cluster  

E-print Network

Average properties of the magnetic reconnection ion diffusion region in the Earth's magnetotail (2010), Average properties of the magnetic reconnection ion diffusion region in the Earth's magnetotail; published 14 August 2010. [1] Magnetic reconnection plays a key role in the circulation of plasma through

California at Berkeley, University of

373

Highly stable FeCo/carbon composites: Magnetic properties and microwave response  

NASA Astrophysics Data System (ADS)

Highly steady composites of FeCo alloy and carbon nanotubes have been synthesized by in situ catalytic decomposition of benzene over FeCo alloy nanoparticles generated through procedures of sol-gel fabrication and hydrogen reduction. Magnetic measurement indicates that the coercivity (HC) increases with the rise of Co concentration and the saturation magnetization (MS) rises in the order of FeCo13@Ccomplex permittivity and permeability of the composites indicates that the maximum reflection loss (RL) is -6.7 dB at 11.1 GHz at thickness of 1.5 mm for FeCo13@C, and as well as the electromagnetic wave absorption properties can be tuned by adjusting the composition of FeCo alloy and the absorption layer thickness.

Xu, M. H.; Zhong, W.; Wang, Z. H.; Au, Chaktong; Du, Y. W.

2013-08-01

374

Electrical and magnetic properties of thin films containing metal clusters  

NASA Astrophysics Data System (ADS)

A large variety of granular polymer thin films can be synthetized in a capacitively coupled coplanar diode radiofrequency (r.f.) discharge system in which an argon-monomer mixture is injected at low pressure (20 mTorr). This approach offers several advantages over the other techniques, e.g. easy control of the metal content in the film from a few % up to 100%. The d.c. electrical properties of gold containing plasma polymerized tetrafluoroethylene (PPTFE) and the magnetic behavior of cobalt containing plasma polymerized propane (PPP) are reported in this paper.

Laurent, C.; Kay, E.

1989-03-01

375

Polarizability and magnetoplasmonic properties of magnetic general nanoellipsoids.  

PubMed

An approach to compute the polarizability tensor of magnetic nanoparticles having general ellipsoidal shape is presented. We find a surprisingly excellent quantitative agreement between calculated and experimental magneto-optical spectra measured in the polar Kerr configuration from nickel nanodisks of large size (exceeding 100 nm) with circular and elliptical shape. In spite of its approximations and simplicity, the formalism presented here captures the essential physics of the interplay between magneto-optical activity and the plasmonic resonance of the individual particle. The results highlight the key role of the dynamic depolarization effects to account for the magneto-optical properties of plasmonic nanostructures. PMID:23609693

Maccaferri, Nicolò; González-Díaz, Juan B; Bonetti, Stefano; Berger, Andreas; Kataja, Mikko; van Dijken, Sebastiaan; Nogués, Josep; Bonanni, Valentina; Pirzadeh, Zhaleh; Dmitriev, Alexandre; Åkerman, Johan; Vavassori, Paolo

2013-04-22

376

Synthesis, assembly and physical properties of magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

Compared with the top-down lithographic techniques, bottom-up chemical synthesis and self-assembly approaches offer much more flexibilities in creating magnetic nanostructures with controlled size, shape, composition and physical properties. This review summarizes some of the latest developments in this field, with emphasis mainly on transition metals, their alloys and metal oxide nanoparticles. The focus is directed towards the conditions of individual particles as well as large assemblies of particles through colloidal chemistry. Furthermore, some of the future directions in nanomagnetism from the perspective of physical chemists is also presented.

Lin, Xiao-Min; Samia, Anna C. S.

2006-10-01

377

A multipole reaction-field model for gauge-origin independent magnetic properties of solvated molecules  

E-print Network

on the mag- netic moments m of the nuclei. The magnetic properties we consider here are the mag- netizability on the external magnetic induction B and the magnetic moments of the nuclei mK through the vector potential A. WeK B mK 0 , 3 where mK is the nuclear magnetic moment of nucleus K. A phenomenological model

Helgaker, Trygve

378

Corrosion product deposits on boiling-water reactor cladding: Experimental and theoretical investigation of magnetic properties  

NASA Astrophysics Data System (ADS)

Recent Eddy current investigations on the cladding of nuclear fuel pins have shown that the apparent oxide layers are falsified due to unexpected magnetic properties of corrosion product deposits. Analyses by Scanning Electron Microscopy (SEM) or Electron Probe Micro Analysis (EPMA) demonstrated that the deposit layer consists of complex 3-d element oxides (Ni, Mn, Fe) along with Zn, since the reactor operates with a Zn addition procedure to reduce buildup of radiation fields on the recirculation system surfaces. The oxides crystallise in ferritic spinel structures. These spinels are well-known for their magnetic behaviour. Since non-magnetic zinc ferrite (ZnFe 2O 4) may become magnetic when doped with even small amounts of Ni and/or Mn, their occurrence in the deposit layer has been analyzed. The magnetic permeability of zinc ferrite, trevorite and jacobsite and their solid solutions are estimated by magnetic moment additivity. From the void history examination, the low elevation sample (810 mm) did not face significant boiling during the irradiation cycles suggesting growth of (Mn0.092+Zn0.752+Fe0.293+)[(Fe1.713+Mn0.032+Ni0.132+)O] crystals with theoretical value of the magnetic permeability for the averaged heterogeneous CRUD layer of 9.5 ± 3. Meanwhile, (Mn0.162+Zn0.552+Fe0.293+)[(Fe1.713+Mn0.042+Ni0.252+)O] crystallizes at the mid elevation (1810 mm) with theoretical magnetic permeability for the CRUD layer of 4.2 ± 1.5 at the investigated azimuthal location. These theoretical data are compared with the magnetic permeability of the corrosion product deposited layers gained from reactor pool side Eddy current (EC) analyses (9.0 ± 1.0 for low and 3.5 ± 1.0 for high elevation). The calculated thicknesses and magnetic permeability values of the deposition layers (estimated by MAGNACROX multifrequency EC method) match together with these estimated using an "ion magnetic moment additivity" model.

Orlov, A.; Degueldre, C.; Wiese, H.; Ledergerber, G.; Valizadeh, S.

2011-09-01

379

Influence of spherical assembly of copper ferrite nanoparticles on magnetic properties: orientation of magnetic easy axis.  

PubMed

The magnetic properties of copper ferrite (CuFe2O4) nanoparticles prepared via sol-gel auto combustion and facile solvothermal method are studied focusing on the effect of nanoparticle arrangement. Randomly oriented CuFe2O4 nanoparticles (NP) are obtained from the sol-gel auto combustion method, while the solvothermal method allows us to prepare iso-oriented uniform spherical ensembles of CuFe2O4 nanoparticles (NS). X-ray diffractometry (XRD), atomic absorption spectroscopy (AAS), infra-red (IR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), (57)Fe Mössbauer spectroscopy and vibrating sample magnetometer (VSM) are used to investigate the composition, microstructure and magnetic properties of as-prepared ferrite nanoparticles. The field-dependent magnetization measurement for the NS sample at low temperature exhibits a step-like rectangular hysteresis loop (M(R)/M(S) ~ 1), suggesting cubic anisotropy in the system, whereas for the NP sample, typical features of uniaxial anisotropy (M(R)/M(S) ~ 0.5) are observed. The coercive field (HC) for the NS sample shows anomalous temperature dependence, which is correlated with the variation of effective anisotropy (K(E)) of the system. A high-temperature enhancement of H(C) and K(E) for the NS sample coincides with a strong spin-orbit coupling in the sample as evidenced by significant modification of Cu/Fe-O bond distances. The spherical arrangement of nanocrystals at mesoscopic scale provokes a high degree of alignment of the magnetic easy axis along the applied field leading to a step-like rectangular hysteresis loop. A detailed study on the temperature dependence of magnetic anisotropy of the system is carried out, emphasizing the influence of the formation of spherical iso-oriented assemblies. PMID:24714977

Chatterjee, Biplab K; Bhattacharjee, Kaustav; Dey, Abhishek; Ghosh, Chandan K; Chattopadhyay, Kalyan K

2014-06-01

380

Unbalanced magnetic field configuration: plasma and film properties  

NASA Astrophysics Data System (ADS)

Coatings of CrN, TiN, ZrN, TaN and NbN were deposited using an unbalanced magnetron sputtering system with two different degrees of unbalancing to investigate the effect of the degree of unbalancing on both plasma characteristics and film properties. The degree of unbalancing was determined by an extensive characterization of the magnetic field fluxes in the X-Z plane perpendicular to the target. Then, the plasma parameters, such as electron temperature, plasma potential, plasma density and ion current density, were obtained for each target and as a function of the unbalance coefficient. The film microstructure, hardness, corrosion and wear resistant were measured to determine the effect of the degree of unbalancing on these properties. The results suggested that the degree of unbalancing, through the variations induced in the ion bombardment and plasma ionization, had a strong influence on the film hardness, microstructure and preferred orientation.

Rodil, S. E.; Olaya, J. J.

2006-08-01

381

Synthesis and properties of polynitrophenyltetrazolatocobalt(III) complexes  

SciTech Connect

The explosive 3,5-dinitrophenyltetrazolato complex (3,5-DNP) tends to propagate in the deflagration mode which suggests its use as a pressure cartridge charge. However, the existence of 3,5-DNP as a hydrate appears to result in variations of thermomechanical properties thus rendering it undesirable for component use. The 2,4-DNP and 2,4,6-TNP analogs were synthesized. These exist in the anhydrous form under normal conditions and underwent DDT in component configuration. This negated their use in pressure cartridge applications. Synthetic procedures have been developed for 5-(2,4-dinitrophenyl)tetrazole and 5-picryltetrazole as well as for the precursor 2,4-dinitro- and 2,4,6-trinitrobenzonitriles. 6 refs.

Fronabarger, J.; Johnson, R.; Fleming, W.

1986-01-01

382

Effect of amorphous powder blend on the magnetic and mechanical properties of die-upset Nd-Fe-B magnets  

NASA Astrophysics Data System (ADS)

The effect of amorphous powder blend on the magnetic and mechanical properties of die-upset Nd-Fe-B magnets has been investigated. The results showed that the intrinsic coercivity and rectangularity of demagnetization curves declined with increasing amorphous powder content. The Vickers hardness of die-upset Nd-Fe-B magnets first declined, and then increased with increasing amorphous powder content. The maximum Vickers hardness and fracture toughness of die-upset Nd-Fe-B magnets were obtained at the amorphous powder content of 10 wt%, but the excessive amorphous powder made the crystallographic alignment and magnetic properties of die-upset Nd-Fe-B magnets decline sharply. The microstructure shows that the addition of amorphous powder can inhibit the grain growth of die-upset Nd-Fe-B magnets.

Hu, Z. H.; Qu, H. J.; Zhao, J. Q.; Luo, C.

2014-05-01

383

Structure, morphology, and magnetic properties of Fe nanoparticles deposited onto single-crystalline surfaces  

PubMed Central

Summary Background: Magnetic nanostructures and nanoparticles often show novel magnetic phenomena not known from the respective bulk materials. In the past, several methods to prepare such structures have been developed – ranging from wet chemistry-based to physical-based methods such as self-organization or cluster growth. The preparation method has a significant influence on the resulting properties of the generated nanostructures. Taking chemical approaches, this influence may arise from the chemical environment, reaction kinetics and the preparation route. Taking physical approaches, the thermodynamics and the kinetics of the growth mode or – when depositing preformed clusters/nanoparticles on a surface – the landing kinetics and subsequent relaxation processes have a strong impact and thus need to be considered when attempting to control magnetic and structural properties of supported clusters or nanoparticles. Results: In this contribution we focus on mass-filtered Fe nanoparticles in a size range from 4 nm to 10 nm that are generated in a cluster source and subsequently deposited onto two single crystalline substrates: fcc Ni(111)/W(110) and bcc W(110). We use a combined approach of X-ray magnetic circular dichroism (XMCD), reflection high energy electron diffraction (RHEED) and scanning tunneling microscopy (STM) to shed light on the complex and size-dependent relation between magnetic properties, crystallographic structure, orientation and morphology. In particular XMCD reveals that Fe particles on Ni(111)/W(110) have a significantly lower (higher) magnetic spin (orbital) moment compared to bulk iron. The reduced spin moments are attributed to the random particle orientation being confirmed by RHEED together with a competition of magnetic exchange energy at the interface and magnetic anisotropy energy in the particles. The RHEED data also show that the Fe particles on W(110) – despite of the large lattice mismatch between iron and tungsten – are not strained. Thus, strain is most likely not the origin of the enhanced orbital moments as supposed before. Moreover, RHEED uncovers the existence of a spontaneous process for epitaxial alignment of particles below a critical size of about 4 nm. STM basically confirms the shape conservation of the larger particles but shows first indications for an unexpected reshaping occurring at the onset of self-alignment. Conclusion: The magnetic and structural properties of nanoparticles are strongly affected by the deposition kinetics even when soft landing conditions are provided. The orientation of the deposited particles and thus their interface with the substrate strongly depend on the particle size with consequences regarding particularly the magnetic behavior. Spontaneous and epitaxial self-alignment can occur below a certain critical size. This may enable the obtainment of samples with controlled, uniform interfaces and crystallographic orientations even in a random deposition process. However, such a reorientation process might be accompanied by a complex reshaping of the particles. PMID:21977415

Kleibert, Armin; Rosellen, Wolfgang; Getzlaff, Mathias

2011-01-01

384

An Investigation of Magnetic, Electronic and Structural Properties of Metallofullerenes  

NASA Astrophysics Data System (ADS)

Gadolinium based endohedral metallofullerenes Gd3N@C80 functionalized with OH radicals have been found to enhance the relaxivity by orders of magnitude over conventional agents and are being sought as new contrast agents in magnetic resonance imaging (MRI). Using state of the art density functional theory (DFT) in the regime of the local density approximation with the on-site Coulomb interaction (LSDA+U), we have carried out theoretical studies to determine the electronic and magnetic properties of gadolinium-based and lutetium-based nitride fullerenes, namely Lu3-xGdxN@C80 (x = 1-2). While Gd3N@C80 has previously shown promising features as a contrast agent, the idea of replacing gadolinium atoms by lutetium has been proposed to result in a mixed-metal species for multi-modal imaging. Our results indicate that Lu2GdN@C80 is the most stable of all possible configurations with a binding energy 16.57 eV, can be considered for use as both an MRI contrast agent, due to gadolinium's high magnetic moment, and as a potential radioactive therapeutic or diagnostic agent, by neutron activation of a lutetium radioisotope. These results along with details of electronic structure will be presented.

Ong, S. Vincent; Qian, Meichun; Khanna, Shiv

2008-03-01

385

Magnetic properties of iron loaded MCM-48 molecular sieves  

NASA Astrophysics Data System (ADS)

Mesoporous molecular sieves of MCM-48 type were loaded with iron by the wet impregnation method, using Fe(III) nitrate or Fe(II) sulfate aqueous solutions as Fe sources, to obtain a magnetic porous composite. The iron loaded materials were characterized by XRD, N 2 adsorption and DRUV-vis and compared with the Si-MCM-48 host. Their magnetic properties were studied by measuring the hysteresis loops up to 1.5 T at different temperatures (5-300 K) and by magnetization vs. temperature curves following the conventional zero field cooling (ZFC) and field cooling (FC) protocols. Materials with high structure regularity and surface area are obtained, which exhibit a mixed paramagnetic and superparamagnetic behavior, arising in isolated iron ions inserted in the host framework, and in small iron oxide clusters or nanoparticles forming inside the pores, respectively. Larger hematite particles (8-13 nm) grown on the external surface provide a quite small ferromagnetic contribution to the hysteresis loop.

Elías, Verónica R.; Oliva, Marcos I.; Vaschetto, Eliana G.; Urreta, Silvia E.; Eimer, Griselda A.; Silvetti, Silvia P.

2010-11-01

386

Transport properties of high-temperature air in a magnetic field  

SciTech Connect

Transport properties of equilibrium air plasmas in a magnetic field are calculated with the Chapman-Enskog method. The range considered for the temperature is [50-50 000] K and for the magnetic induction is [0-300] T.

Bruno, D. [Institute of Inorganic Methodologies and Plasmas, CNR, 70126 Bari (Italy); Capitelli, M.; Catalfamo, C. [Department of Chemistry, University of Bari, 70126 Bari (Italy); Giordano, D. [Aerothermodynamics Section, ESA-ESTEC, 2200 AG Noordwijk (Netherlands)

2011-01-15

387

Engineering the magnetic properties of the Mn13 cluster by doping  

E-print Network

With a goal to produce a giant magnetic moment in a Mn13 cluster that will be useful for practical applications, we have considered the structure and magnetic properties of a pure Mn13 cluster and substitutionally doped ...

Datta, Soumendu

388

Engineering the magnetic properties of hybrid organic-ferromagnetic interfaces by molecular chemical functionalization  

E-print Network

We have performed systematic first-principles calculations to tailor the magnetic properties at a hybrid organic-ferromagnetic interface by adsorbing organic molecules containing ?(p[subscript z]) electrons onto a magnetic ...

Lazic, Predrag

389

Investigating the anisotropy of magnetic susceptibility and other rock magnetic properties of the Beaver River Diabase in northeastern Minnesota  

NASA Astrophysics Data System (ADS)

The Beaver River Diabase (BRD) is a series of mafic dikes and sills within the Beaver Bay Complex (BBC) of northern Minnesota, which formed during the development of the ~1.1 Ga Midcontinent Rift (MCR). The BRD is one of the youngest and most extensive intrusive phases of the BBC. The BRD dikes and sills were emplaced into the medial levels of the 6-10 kilometer-thick North Shore Volcanic Group and occur over an arcuate area extending 120 by 20 kilometers. The BRD is composed of fine- to medium-grained ophitic olivine gabbro and does not display obvious foliation or lineation features and rarely displays modal layering. Without obvious magmatic internal structures, it is difficult to determine emplacement properties such as flow direction using standard geologic mapping or petrographic techniques. For this reason, we measured the anisotropy of magnetic susceptibility (AMS), in conjunction with other rock magnetic properties, to better understand the BRD's emplacement and deformation history in the context of the MCR. AMS measures the directional dependence of low-field magnetic susceptibility, and is used to infer a shape-preferred orientation of magnetic minerals within a rock, which can be related to specific emplacement mechanisms (e.g. directional flow or settling). Preliminary analysis of AMS at 20 sites within the southern half of the BRD (with 4-7 samples per site) shows maximum susceptibility values between 4.48 x 10-6 and 2.22 x 10-4 m3/kg (1165 and 65400 ?SI). Most specimens display nearly isotropic AMS ellipsoids (Pj < 1.15) with minor degrees of prolateness and oblateness. However, about 20% of specimens have higher anisotropies (Pj between 1.15 and 1.67) and higher degrees of oblateness and prolateness. Variations in AMS properties may reflect differences in concentration and composition, as well as emplacement mechanisms. Measurements of susceptibility as a function of temperature yield Curie points between 470 and 570 °C, indicating a presence of low-titanium titanomagnetite. Major hysteresis loops and first order reversal curve (FORC) experiments show coercivities between 1 and 125 mT, with a bulk average microcoercivity of 25 mT, consistent with titanomagnetite as the dominant remanence carrier. Further analysis will also investigate the relationship of AMS to rock fabric by measuring mineral crystal preferred orientations using electron backscatter diffraction. These measurements will supplement the AMS data, and provide links to the role of microstructure, texture and mineralogy in AMS.

Hariri, S. H.; Brownlee, S. J.; Feinberg, J. M.; Jackson, M. J.; Miller, J. D.

2013-12-01

390

Magnetic properties and loss separation in iron-silicone-MnZn ferrite soft magnetic composites  

SciTech Connect

This paper investigates the magnetic and structural properties of iron-based soft magnetic composites coated with silicone-MnZn ferrite hybrid. The organic silicone resin was added to improve the flexibility of the insulated iron powder and causes better adhesion between particles to increase the mechanical properties. Scanning electron microscopy and distribution maps show that the iron particle surface is covered with a thin layer of silicone-MnZn ferrite. Silicone-MnZn ferrite coated samples have higher permeability when compared with the non-magnetic silicone resin coated compacts. The real part of permeability increases by 34.18% when compared with the silicone resin coated samples at 20 kHz. In this work, a formula for calculating the total loss component by loss separation method is presented and finally the different parts of total losses are calculated. The results show that the eddy current loss coefficient is close to each other for the silicone-MnZn ferrite, silicone resin and MnZn ferrite coated samples (0.0078

Wu, Shen; Sun, Aizhi; Xu, Wenhuan; Zou, Chao; Yang, Jun; Dong, Juan [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing (China)

2013-12-16

391

Superconducting and magnetic properties of Fe-Se-Te compounds  

NASA Astrophysics Data System (ADS)

The discovery of a new Fe based superconductor ?-FeSex with a Tc of 8 K, hot on the heels of the discovery of superconductivity in LaOFeP/As compounds, has triggered a fresh interest in the study of Fe based superconductors. Se can be replaced with Te in FeSe1-xTex and this results in an increase in Tc from 8 K for x = 0 to 15 K for x = 0.5 while compounds for x > 0.8 are no longer superconducting. We report the synthesis and characterization of the compounds FeSe1-xTex covering the entire solid solution range. The superconducting transition in resistivity measurements does not show any broadening in magnetic fields up to 9 T, but shifts to lower temperatures linearly with a value ˜ -0.22 K/T. This results in extremely high upper critical fields (Hc2) of the order of 70-80 T in these compounds. The superconducting properties are also sensitive to applied pressure and exhibit a positive dTc/dP of around 0.41 K/kbar for the x = 0.5 composition. We observe a jump in specific heat at Tc corresponding to a superconducting gap of 1.8 meV, indicating the bulk nature of superconductivity. Detailed investigations through magnetization, transport and specific heat measurements are presented. A study of the magnetic properties of the non superconducting end compound, FeTe is also presented to gain insight into the onset of superconductivity in the doped systems.

Tomy, C. V.; Balakrishnan, G.; Lees, M. R.

2009-03-01

392

Magnetic and transport properties of diluted granular multilayers  

NASA Astrophysics Data System (ADS)

The magnetic and transport properties of Co80Fe20(t)/Al2O3(4 nm) multilayers with low nominal thicknesses t =0.7 and 0.9 nm of Co80Fe20 granular layers are studied. Magnetic studies find a superparamagnetic state above the blocking temperature Tb (of field-cooled/zero-field-cooled splitting) that grows with t and decreases with H. The low-voltage Ohmic tunnel transport passes to non-Ohmic I ?V3/2 law for applied fields above ˜500 V/cm. At fixed V, the temperature dependence of conductance reveals an anomalous dip around ˜220 K, which can be attributed to the effect of surface contamination by supercooled water. Current-in-plane tunnel magnetoresistance (MR) ratio tends, at lower t, to higher maximum values (˜8% at room temperature) but to lower field sensitivity. This may indicate growing discorrelation effect (e.g., between shrinking areas of correlated moments) in this regime and corroborates the deficit of granule magnetization estimated from the Inoue-Maekawa MR fit, compared to that from direct magnetization measurements. MR displays a mean-field-like critical behavior when t approaches the point of superparamagnetic/superferromagnetic transition (tc˜1.3 nm at room temperature) from below, different from the formerly reported percolationlike behavior at approaching it from above. With growing temperature, MR reveals, beyond the common decrease, an anomalous plateau from Tb˜30-50 K up to some higher value T?˜150-200 K, not seen at higher t.

Silva, H. G.; Gomes, H. L.; Pogorelov, Y. G.; Pereira, L. M. C.; Kakazei, G. N.; Sousa, J. B.; Araújo, J. P.; Mariano, J. F. L.; Cardoso, S.; Freitas, P. P.

2009-12-01

393

Low temperature synthesis of nanocrystalline Dy3+ doped cobalt ferrite: Structural and magnetic properties  

NASA Astrophysics Data System (ADS)

In the present work, the effect of Dy3+ substitution on the structural and magnetic properties of CoFe2-xDyxO4 (x = 0.00 to 0.1 in step of 0.025) system synthesized by solution combustion method were investigated. The thermal decomposition process was investigated by means of differential and thermal gravimetric analysis that showed that the precursor could yield the final product after calcination above 600 °C. The phase purity and crystal lattice symmetry were estimated from X-ray diffraction studies. The microstructural features were observed by scanning electron microscopy that demonstrates the fine clustered particles with an increase of average grain size with Dy3+ content. The existence of constituent's, i.e., Co, Fe, and Dy were authenticated by energy dispersive X-ray analysis. An infrared spectroscopy study shows the presence of two absorption bands in the frequency range around 590 cm-1 (?1) and around 480 cm-1 (?2); which indicate the presence of tetrahedral and octahedral group complexes, respectively, within the spinel lattice. Room temperature magnetization measurements showed that the saturation magnetization and hysteresis losses (coercivity) decreases with Dy3+ addition, which implies that these materials may be applicable for magnetic data storage and recording media.

Kambale, R. C.; Song, K. M.; Koo, Y. S.; Hur, N.

2011-09-01

394

Homometallic and Heterometallic Antiferromagnetic Rings: Magnetic Properties Studied by Nuclear Magnetic Resonance  

SciTech Connect

The aim of the present thesis is to investigate the local magnetic properties of homometallic Cr{sub 8} antiferromagnetic (AFM) ring and the changes occurring by replacing one Cr{sup 3+} ion with diamagnetic Cd{sup 2+} (Cr{sub 7}Cd) and with Ni{sup 2+} (Cr{sub 7}Ni). In the heterometallic ring a redistribution of the local magnetic moment is expected in the low temperature ground state. We have investigated those changes by both {sup 53}Cr-NMR and {sup 19}F-NMR. We have determined the order of magnitude of the transferred hyperfine coupling constant {sup 19}F - M{sup +} where M{sup +} = Cr{sup 3+}, Ni{sup 2+} in the different rings. This latter result gives useful information about the overlapping of the electronic wavefunctions involved in the coordinative bond.

Casadei, Cecilia

2012-05-09

395

Magnetic and Structural Properties of Cosputtered Rare Earth-Iron Permanent-Magnet Films  

NASA Astrophysics Data System (ADS)

The samples for this study are of the form R _2Fe_1_4 B:M (where R = Nd, Pr; M = Ag, Fe, Ta, or Pr). They were prepared in a multiple-gun sputtering system with a temperature-controlled substrate holder capable of reaching 700^circC. The R _2Fe_1_4 B (RFB) was sputtered from a single alloy target. The RFB and M were deposited sequentially, 5 to 5000 A at a time onto Ta or mica substrates. The total film thickness was usually 1 mum. The structures of the films were studied by large-angle and small-angle x-ray diffraction and scanning electron microscopy. Their magnetic properties were studied with a room-temperature vibrating-sample magnetometer (VSM) with a maximum field of 17.1 kOe, and with a cryogenic VSM containing a superconducting solenoid capable of generating 80 kOe. A special heater was developed for the cryogenic VSM, and some of the samples were examined at room temperature in fields up to 80 kOe. It was found that the properties of these films depended strongly upon the material M and the individual layer thicknesses of M and RFB. The magnetization data were compared to coherent rotation, domain wall pinning, and reverse domain nucleation theories of magnetization reversal. The Pr _2Fe_1 _4B:Pr films, for example, have the largest room-temperature coercivities (about 20 kOe), and the magnetization reversal is probably controlled by reverse domain nucleation.

Aylesworth, Kevin Donald

396

Two Body Mesic Exchange Current Contribution to m1 Transitions and Magnetic Moments of Complex Nuclei  

Microsoft Academic Search

In this thesis we study the one pion exchange (OPE) current contribution to nuclear magnetic moments and electro-magnetic transitions (M1). Almost all the previous theoretical and experimental work has been done for nuclei with closed shell (+OR-)1 nucleon. We examine relatively simple complex nuclei i.e., a nucleus with closed shell +2 nucleons (a,b) and a nucleus with closed shell +1

Shaheen Rab

1982-01-01

397

Molecular based magnets comprising vanadium tetracyanoethylene complexes for shielding electromagnetic fields  

DOEpatents

The invention presents a vanadium tetracyanoethylene solvent complex for electromagnetic field shielding, and a method for blocking low frequency and magnetic fields using these vanadium tetracyanoethylene compositions. The compositions of the invention can be produced at ambient temperature and are light weight, low density and flexible. The materials of the present invention are useful as magnetic shields to block low frequency fields and static fields, and for use in cores in transformers and motors. 21 figs.

Epstein, A.J.; Morin, B.G.

1998-10-13

398

Molecular based magnets comprising vanadium tetracyanoethylene complexes for shielding electromagnetic fields  

DOEpatents

The invention presents a vanadium tetracyanoethylene solvent complex for electromagnetic field shielding, and a method for blocking low frequency and magnetic fields using these vanadium tetracyanoethylene compositions. The compositions of the invention can be produced at ambient temperature and are light weight, low density and flexible. The materials of the present invention are useful as magnetic shields to block low frequency fields and static fields, and for use in cores in transformers and motors.

Epstein, Arthur J. (Columbus, OH); Morin, Brian G. (Columbus, OH)

1998-01-01

399

Magnetic properties of Ho 2Co 17? x Si x compounds  

Microsoft Academic Search

We have studied the magnetic properties of Ho2Co17?xSix compounds (x?3) by means of magnetic measurements and X-ray diffraction on magnetically aligned powders. The Curie temperature and the spontaneous moment decrease strongly with increasing Si concentration. We have constructed the magnetic phase diagram for the Ho2Co17?xSix system. The easy magnetization direction is parallel to the c-axis in an extended temperature region

S. J. Hu; X. Z. Wei; O. Tegus; D. C. Zeng; E. Brück; J. C. P. Klaasse; F. R. de Boer; K. H. J. Buschow

1999-01-01

400

Controlling Magnetism by Light in Nanoscaled Heterostructures of Cyanometallate Coordination Networks: the role of increased complexity  

NASA Astrophysics Data System (ADS)

Nanometer-sized heterostructures of the Prussian blue analogues AjCok[Fe(CN)6]l.nH2O (Co-Fe PBA, with A = K, Rb) and RbaNib[Cr(CN)6]c.mH2O (Ni-Cr PBA) have been investigated, and new phenomena, not observed for the constituent bulk phases, have been observed.footnotetext D.M. Pajerowski, M.J. Andrus, J.E. Gardner, E.S. Knowles, M.W. Meisel, D.R. Talham, J. Am. Chem. Soc. 132 (2010) 4058.^,footnotetext M.F. Dumont, E.S. Knowles, A. Guiet, D.M. Pajerowski, A. Gomez, S.W. Kycia, M.W. Meisel, D.R. Talham, Inorg. Chem. 50 (2011) 4295.^,footnotetext D.M. Pajerowski, J.E. Gardner, M.J. Andrus, S. Datta, A. Gomez, S.W. Kycia, S. Hill, D.R. Talham, M.W. Meisel, Phys. Rev. B 82 (2010) 214405.^,footnotetext E.S. Knowles, M.F. Dumont, M.K. Peprah, M.W. Meisel, C.H. Li, M.J. Andrus, D.R. Talham, arxiv:1207.2623 (2012). A crucial aspect of the ability to photocontrol the persistent magnetism up to 70 K is the role of the strain coupling present at the interfaces between the nanoscaled regions of the constituents. Increasing the morphological complexity of the samples has the potential to provide materials possessing novel combinations of properties. In parallel, the interplay between long-range magnetic order and structural coherence is an important consideration in our attempts to design new systems. Open, unresolved issues will be discussed, and potential future paths will be sketched.

Meisel, Mark W.

2013-03-01

401

Nickel(II)-Lanthanide(III) Magnetic Exchange Coupling Influencing Single-Molecule Magnetic Features in {Ni2 Ln2 } Complexes.  

PubMed

Four isostructural [Ni2 Ln2 (CH3 CO2 )3 (HL)4 (H2 O)2 ](3+) (Ln(3+) =Dy (1), Tb (2), Ho (3) or Lu (4)) complexes and a dinuclear [NiGd(HL)2 (NO3 )3 ] (5) complex are reported (where HL=2-methoxy-6-[(E)-2'-hydroxymethyl-phenyliminomethyl]-phenolate). For compounds 1-3 and 5, the Ni(2+) ions are ferromagnetically coupled to the respective lanthanide ions. The ferromagnetic coupling in 1 suppresses the quantum tunnelling of magnetisation (QTM), resulting in a rare zero dc field Ni-Dy single-molecule magnet, with an anisotropy barrier Ueff of 19?K. PMID:25214152

Ahmed, Naushad; Das, Chinmoy; Vaidya, Shefali; Langley, Stuart K; Murray, Keith S; Shanmugam, Maheswaran

2014-10-27

402

Complex permittivity, complex permeability and microwave absorption properties of ferrite polymer composites  

NASA Astrophysics Data System (ADS)

The complex permittivity ( ?'- j??), complex permeability (?'- j??) and microwave absorption properties of ferrite-polymer composites prepared with different ferrite ratios of 50%, 60%, 70% and 80% in polyurethane (PU) matrix have been investigated in X-band (8.2-12.4 GHz) frequency range. The M-type hexaferrite composition BaCo +20.9Fe +20.05Si +40.95Fe +310.1O 19 was prepared by solid-state reaction technique, whereas commercial PU was used to prepare the composites. At higher GHz frequencies, ferrite's permeabilities are drastically reduced, however, the forced conversion of Fe +3 to Fe +2 ions that involves electron hopping, could have increased the dielectric losses in the chosen composition. We have measured complex permittivity and permeability using a vector network analyzer (HP/Agilent model PNA E8364B) and software module 85071. All the parameters ?', ??, ?' and ?? are found to increase with increased ferrite contents. Measured values of these parameters were used to determine the reflection loss at various sample thicknesses, based on a model of a single-layered plane wave absorber backed by a perfect conductor. The composite with 80% ferrite content has shown a minimum reflection loss of -24.5 dB (>99% power absorption) at 12 GHz with the -20 dB bandwidth over the extended frequency range of 11-13 GHz for an absorber thickness of 1.6 mm. The prepared composites can fruitfully be utilized for suppression of electromagnetic interference (EMI) and reduction of radar signatures (stealth technology).

Abbas, S. M.; Dixit, A. K.; Chatterjee, R.; Goel, T. C.

2007-02-01

403

Synthesis, structures and properties of a series of manganese coordination complexes constructed from dicarboxylic fluorene derivatives  

SciTech Connect

Assembly reactions of 9,9-diethylfluorene-2,7-dicarboxylic acid (H{sub 2}DFDC) and Mn(CH{sub 3}COO){sub 2}{center_dot}4H{sub 2}O or MnCl{sub 2}{center_dot}4H{sub 2}O by tuning of various secondary ligands such as 2,2 Prime -bipyridine (2,2 Prime -bpy), 4,4 Prime -bipyridine (4,4 Prime -bpy) or 1,3-bis(4-pyridyl)propane) (bpp), gave rise to four complexes {l_brace} [Mn{sub 2}(DFDC){sub 2}(DMF){sub 2}]{center_dot}H{sub 2}O{r_brace} {sub n} (1), [Mn(DFDC)(2,2 Prime -bpy)]{sub n} (2), {l_brace} [Mn{sub 2}(DFDC){sub 2}(4,4 Prime -bpy){sub 2}]{center_dot}2CH{sub 3}OH{r_brace} {sub n} (3), and {l_brace} [Mn{sub 4}(DFDC){sub 4}(bpp){sub 2}(CH{sub 3}OH){sub 3} (H{sub 2}O){sub 3}]{center_dot}3(CH{sub 3}OH){center_dot}3(H{sub 2}O){r_brace} {sub n} (4). Single crystal X-ray diffraction analysis reveal that complex 1 is three dimensional structure with rhombic channels filled by guest water molecules; 2 presents a close-packed structure with high thermal stability; 3 exhibits a three dimensional framework with micro-porous channels filled by guest methanol molecules and 4 is a two-dimensional structure. The photoluminescent properties of 1-4 have been studied, respectively, showing that the Mn(II) ions, accessorial organic ligands or crystal structures exert important influences on the photoluminescence emissions of H{sub 2}DFDC ligands. Thermogravimetric analysis show that the complexes have remarkably high thermal stability. Magnetic susceptibility measurements have been finished and discussed for the complexes. - Graphical abstract: Assembly of 9,9-diethylfluorene-2,7-dicarboxylic acid and Mn(II) salts by tuning of various accessorial ligands resulted in four manganese complexes with different topological frameworks. Highlights: Black-Right-Pointing-Pointer Four manganese complexes based on 9,9-diethylfluorene-2,7-dicarboxylic acid were obtained. Black-Right-Pointing-Pointer The complexes were structurally characterized by single-crystal X-ray diffraction. Black-Right-Pointing-Pointer The complexes 1-4 display different topological structures. Black-Right-Pointing-Pointer Thermogravimetric analysis show the complexes have remarkably high thermal stability.

Li Xing, E-mail: lixing@nbu.edu.cn [State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang, 315211 (China); Zhao Xiuhua; Bing Yue; Zha Meiqin; Xie Hongzhen; Guo Zhiyong [State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang, 315211 (China)

2013-01-15

404

Tailoring of Magnetic Properties of Glass Coated Microwires.  

National Technical Information Service (NTIS)

The magnetic behaviour of the glass-covered metallic microwires with a wide compositional range of composition with soft and bard magnetic character is presented. The effect of conventional furnace and dc current annealing under dc axial magnetic field or...

A. P. Zhukov, J. Gonzalez, J. M. Blanco, V. Zhukova

2001-01-01

405

Phenoxide bridged tetranuclear Co(II), Ni(II), Cu(II) and Zn(II) complexes: Electrochemical, magnetic and antimicrobial studies  

NASA Astrophysics Data System (ADS)

Phenoxide bridged later first row transition metal(II) complexes have been prepared by the interaction of later 3d transition metal(II) chlorides with tetranucleating compartmental Schiff base ligand system derived from 2,6-diformyl-4-methylphenol, p-phenylenediamine and 2-hydrazinobenzothiazole. Ligand and complexes were characterized by analytical, spectral (IR, UV-visible, ESR, FAB-mass and fluorescence), magnetic and thermal studies. All complexes are found to have octahedral geometry. The mutual influence of metal centres in terms of cooperative effect on the electronic, magnetic, electrochemical and structural properties was investigated. The Schiff base and its complexes have been screened for their antibacterial (against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa) and antifungal activities (against Aspergillus niger, and Candida albicans).

Kamath, Anupama; Kulkarni, Naveen V.; Netalkar, Priya P.; Revankar, Vidyanand K.

2011-09-01

406

The structure and magnetic properties of magnetically soft cobalt base nanocrystalline powders and nanocomposites with silicon binding  

Microsoft Academic Search

The paper will present influence of high energy mechanical milling process and isothermal annealing of cobalt base metallic glasses on magnetic properties and their structure. Investigation were carried out on Co68Fe4Mo1Si13.5B13.5 itd. metallic glass tapes milled with different times of milling and different condition of annealing. Based on the results of magnetic properties measurements and particles size distribution nanocomposites samples

L. A. Dobrza?ski; R. Nowosielski; J. Konieczny

2004-01-01

407

Magnetic Properties of Hydrothermalized A-type Red Granites  

NASA Astrophysics Data System (ADS)

Hydrothermalized A-type granites are commonly identified by their pink to red-brick colour attributed to tiny flakes of hematite in the alkali feldspars. These inclusions can be of interest in magnetic studies, but their timing and process of formation are still unclear. Formation of chlorite after biotite is the commonest effect of hydrother- malization and may occur quite early after crystallization due to late-magmatic or externally-derived fluids. The reddish colour appears at a later stage. Five cases of A-type granites were investigated for their magnetic mineralogy and properties. The selected cases range from nearly unmodified granites (Panafrican stratoid granites of Madagascar) to strongly hydrothermalized ones (Meruoca, Brazil; Tana, Corsica); in- termediate cases are : Mount Scott (Oklahoma), Bushveld (granitic core kindly pro- vided by R.G. Cawthorn) and. Hydrothermal alteration is often associated to a de- crease of the magnetic susceptibility magnitude (K) and of the anisotropy degree (P). It also strongly affects the rockt's bulk coercivity parameters, since alteration changes the relative amounts of coarse-grained primary magnetite, fine-grained PSD to SD sec- ondary magnetite, and hematite. Correspondingly, most samples plot away from the magnetite trend in the Dayt's diagram, but the different groups identified after coer- civity parameters do not directly correlate with whole-rock colour. In addition, IRM- acquisition curves and thermal demagnetization of tri-axial IRM show that hematite occurs in almost all analysed samples despite their colour. Various hematite coercivity ranges are also evidenced. In fact, hematite can be formed either in feldspar crys- tals or after magnetite. Tiny hematite within feldspars can appear either by exsolu- tion process or, more likely, by precipitation from a fluid phase. For these reasons, hematite inclusions may carry a remanence acquired shortly after granite crystalliza- tion or, conversely, a recent chemical remanence due to fluid circulation, unrelated to the magmatic history.

Trindade, R. I. F.; Nédélec, A.; Peschler, A.; Archanjo, C. J.; Poitrasson, F.; Bouchez, J. L.

408

Electronic and magnetic properties of the graphene-ferromagnet interface  

NASA Astrophysics Data System (ADS)

This paper presents our work on the investigation of the surface structure and the electronic and magnetic properties of the graphene layer on the lattice-matched surface of a ferromagnetic material, Ni(111). Scanning tunneling microscopy imaging shows that perfectly ordered epitaxial graphene layers can be prepared by elevated temperature decomposition of hydrocarbons, with domains larger than the terraces of the underlying Ni(111). In some exceptional cases, graphene films do not show rotational alignment with the metal surface, leading to moiré structures with small periodicities. We discuss the crystallographic structure of graphene with respect to the Ni(111) surface relying both on experimental results and on recent theoretical studies. X-ray absorption spectroscopy investigations of empty valence-band states demonstrate the existence of interface states, which originate from the strong hybridization between the graphene ? and Ni 3d valence-band states with the partial charge transfer of the spin-polarized electrons to the graphene ?* unoccupied states. The latter leads to the appearance of an induced magnetic moment of carbon atoms in the graphene layer, which is unambiguousl