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1

Magnetic properties of liquid crystalline iron complexes  

NASA Astrophysics Data System (ADS)

We report on the magnetic properties of liquid crystalline iron complexes with 1,4,7-tris[3,4-bis(decyloxy)-benzyl]-1,4,7-triazacyclononane. Mössbauer spectroscopy in external magnetic fields reveals two different molecular configurations: monomers form magnetic single domain particles while dimers are found to behave diamagnetic.

Luetkens, H.; Klauß, H.-H.; Benda, R.; Walf, G. H.; Litterst, F. J.; Lattermann, G.

1999-09-01

2

Magnetic Properties of Some Binuclear Complexes of Chromium and Iron  

Microsoft Academic Search

WE have been investigating the magnetic properties of a series of polynuclear complexes of the first-row transition elements. Following the procedure of Kambe1 and Abragam2, the general interaction between the two metal ions in a binuclear complex may be formulated as , where J is the exchange interaction, s1 and s2 are the spins of the two metal ions, and

A. Earnshaw; J. Lewis

1958-01-01

3

Magnetic and electronic properties of complex oxide interfaces  

NASA Astrophysics Data System (ADS)

Interfaces between two complex materials based on perovskite oxides can have novel physical properties. We studied the magnetic and electronic properties of La0.67Ca0.33MnO3/YBa2Cu3O7 (LCMO/YBCO) superlattices using first-principles density-functional theory (DFT). The energetics of several types of magnetic (spin) configurations of Mn ions near the LCMO/YBCO interface have been calculated using the DFT approach. Their magnetic and electronic properties have been explored and compared to the properties of bulk materials. These results are compared to recent experimental observation of suppressed magnetization at the LCMO/YBCO interface. We will also discuss the possibility of charge transfer across the interface, as suggested by recent experimental results from local electron energy-loss spectroscopy (EELS). This research was sponsored by the Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, U.S. Department of Energy, under contract DE-AC05-00OR22725 with Oak Ridge National Laboratory, managed and operated by UT-Battelle, LLC, and by the McMinn Endowment at Vanderbilt University.

Luo, Weidong; Varela, Maria; Pennycook, Stephen J.; Pantelides, Sokrates T.

2007-03-01

4

Negative g Factors, Berry Phases, and Magnetic Properties of Complexes  

NASA Astrophysics Data System (ADS)

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 magneic field. Ab initio calculations show that gXgYgZ<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 gi, i=X, Y, Z, on each metal site can be extracted from experiment.

Chibotaru, L. F.; Ungur, L.

2012-12-01

5

Magnetic properties and chiral states of a trimetallic uranium complex  

NASA Astrophysics Data System (ADS)

The magnetic properties of the triangular molecular nanomagnet [UO2L]3 (L = 2-(4-tolyl)-1,3-bis(quinolyl)malondiiminate) have been investigated through electron paramagnetic resonance spectroscopy, high-field magnetization and susceptibility measurements. The experimental findings are well reproduced by a microscopic model including exchange interactions and local crystal fields. These results show that [UO2L]3 is characterized by a non-magnetic ground doublet corresponding to two oppositely twisted chiral arrangements of the uranium moments. The non-axial character of single-ion crystal fields leads to quantum tunneling of the noncollinear magnetization in the presence of a magnetic field applied perpendicularly to the triangle plane.

Carretta, S.; Amoretti, G.; Santini, P.; Mougel, V.; Mazzanti, M.; Gambarelli, S.; Colineau, E.; Caciuffo, R.

2013-12-01

6

Spectral and magnetic properties of phenylazo-6-aminouracil complexes  

NASA Astrophysics Data System (ADS)

Complexes of Co II, Ni II and Cu II with substituted phenylazo-6-aminouracils containing (-H, p-OH, p-CH 3, p-OCH 3p-COOH) have been synthesized and characterized by elemental analysis, magnetic measurements and spectral measurements (IR, UV-Vis, ESR). Infrared spectra assigned the fundamental bands of the major groups, O?H, N?H, C?H, C?O, C?N, N?N, C?N and C?O (?, ? and ? modes of vibrations). The absence of ? OH and the appearance of ? C?O in the infrared spectra of the free ligands of 5-( p-tolyl and p-anisylazo)-6-aminouracil, assigned the keto structure, whereas in cases of 5-(phenyl, p-hydroxyphenyl and p-carboxyphenylazo)-6-aminouracil ligands, the data showed strong ? OH and ? C?O bands to assign keto-enol tautomerisms. The modes of interactions between the ligands and the metals were discussed, where oxygen and nitrogen atoms (of amino-amide groups) are involved in chelation. The azo group was not involved in chelation for all the prepared complexes except those of copper complexes derived from 5-(phenyl, p-tolyl, p-hydroxyphenyl and p-carboxyphenylazo)-6-aminouracils. The room temperature effective magnetic moment values, the Nujol mull spectra and ESR proved that all the prepared complexes were of octahedral geometry, except the nickel complex derived from 5-(phenylazo)-6-aminouracil and cobalt complex derived from 5-( p-carboxy-phenylazo)-6-aminouracil were square planar.

Masoud, Mamdouh S.; Abou El-Enein, Saeda A.; Ayad, Mohamed E.; Goher, Ahmed S.

2004-01-01

7

Spectral and magnetic properties of phenylazo-6-aminouracil complexes.  

PubMed

Complexes of Co(II), Ni(II) and Cu(II) with substituted phenylazo-6-aminouracils containing (-H, p-OH, p-CH(3), p-OCH(3) p-COOH) have been synthesized and characterized by elemental analysis, magnetic measurements and spectral measurements (IR, UV-Vis, ESR). Infrared spectra assigned the fundamental bands of the major groups, O-H, N-H, C-H, C=O, C=N, N=N, C-N and C-O (nu, delta and gamma modes of vibrations). The absence of nu(OH) and the appearance of nu(C=O) in the infrared spectra of the free ligands of 5-(p-tolyl and p-anisylazo)-6-aminouracil, assigned the keto structure, whereas in cases of 5-(phenyl, p-hydroxyphenyl and p-carboxyphenylazo)-6-aminouracil ligands, the data showed strong nu(OH) and nu(C=O) bands to assign keto-enol tautomerisms. The modes of interactions between the ligands and the metals were discussed, where oxygen and nitrogen atoms (of amino-amide groups) are involved in chelation. The azo group was not involved in chelation for all the prepared complexes except those of copper complexes derived from 5-(phenyl, p-tolyl, p-hydroxyphenyl and p-carboxyphenylazo)-6-aminouracils. The room temperature effective magnetic moment values, the Nujol mull spectra and ESR proved that all the prepared complexes were of octahedral geometry, except the nickel complex derived from 5-(phenylazo)-6-aminouracil and cobalt complex derived from 5-(p-carboxy-phenylazo)-6-aminouracil were square planar. PMID:14670463

Masoud, Mamdouh S; Abou El-Enein, Saeda A; Ayad, Mohamed E; Goher, Ahmed S

2004-01-01

8

Complex structure of triangular graphene: electronic, magnetic and electromechanical properties.  

PubMed

We have investigated electronic and magnetic properties of graphene nanodisks (nanosize triangular graphene) as well as electromechanical properties of graphene nanojunctions. Nanodisks are nanomagnets made of graphene, which are robust against perturbation such as impurities and lattice defects, where the ferromagnetic order is assured by Lieb's theorem. We can generate a spin current by spin filter, and manipulate it by a spin valve, a spin switch and other spintronic devices made of graphene nanodisks. We have analyzed nanodisk arrays, which have multi-degenerate perfect flat bands and are ferromagnet. By connecting two triangular graphene corners, we propose a nanomechanical switch and rotator, which can detect a tiny angle rotation by measuring currents between the two corners. By making use of the strain induced Peierls transition of zigzag nanoribbons, we also propose a nanomechanical stretch sensor, in which the conductance can be switched off by a nanometer scale stretching. PMID:22523991

Ezawa, Motohiko

2012-01-01

9

Thermodynamic and magnetic properties of the finite spin complexes of the Ising type  

NASA Astrophysics Data System (ADS)

In the frame of the static fluctuation approximation (SFA) the analysis of the thermodynamic and magnetic properties of the finite spin clusters in the 1D Ising model is performed It has been shown that under the influence of the magnetic impurity that forms the fixed value of the magnetization on the ends of spin complex the total magnetic ordering of the whole chain becomes possible. The results obtained in the frame of this model can open a way to understanding of magnetic properties of a wide class of the finite cluster systems.

Khamzin, A. A.; Nigmatullin, R. R.

2014-05-01

10

Complex magnetic ordering as a driving mechanism of multifunctional properties of Heusler alloys from first principles  

NASA Astrophysics Data System (ADS)

First-principles calculations are used to study the structural, electronic and magnetic properties of (Pd, Pt)-Mn-Ni-(Ga, In, Sn, Sb) alloys, which display multifunctional properties like the magnetic shape-memory, magnetocaloric and exchange bias effect. The ab initio calculations give a basic understanding of the underlying physics which is associated with the complex magnetic behavior arising from competing ferro- and antiferromagnetic interactions with increasing number of Mn excess atoms in the unit cell. This information allows to optimize, for example, the magnetocaloric effect by using the strong influence of compositional changes on the magnetic interactions. Thermodynamic properties can be calculated by using the ab initio magnetic exchange parameters in finite-temperature Monte Carlo simulations. We present guidelines of how to improve the functional properties. For Pt-Ni-Mn-Ga alloys, a shape memory effect with 14% strain can be achieved in an external magnetic field.

Entel, Peter; Siewert, Mario; Gruner, Markus E.; Herper, Heike C.; Comtesse, Denis; Arróyave, Raymundo; Singh, Navedeep; Talapatra, Anjana; Sokolovskiy, Vladimir V.; Buchelnikov, Vasiliy D.; Albertini, Franca; Righi, Lara; Chernenko, Volodymyr A.

2013-02-01

11

Influence of water molecule coordination on the magnetic properties of polyamine copper dinitrate complexes  

NASA Astrophysics Data System (ADS)

The magnetic properties of two biogenic polyamine copper complexes were investigated by dc magnetization and electron paramagnetic resonance (EPR) measurements. The variation in temperature of the low field magnetization reveals that the absence or presence of water molecules in the copper coordination sphere results, respectively, in the enhancement or suppression of antiferromagnetic interactions between Cu2+ ions. Analysis of the EPR spectra shows considerable temperature dependence of both the g values and EPR linewidths that persist in the paramagnetic regime for both complexes. Such variation of EPR parameters is attributed to the interplay of demagnetizing field effects, pertinent to the purely paramagnetic compound, and to the presence of short-range magnetic order that applies to the antiferromagnetic polyamine complex.

Guskos, N.; Glenis, S.; Likodimos, V.; Typek, J.; Fuks, H.; Wabia, M.; Szymczak, R.; Lin, C. L.; Perkowska, T. A.

2003-06-01

12

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

13

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

14

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

15

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.

16

Complex magnetic ordering and spin glass behavior as a driving mechanism of multifunctional properties of Heusler alloys from first principles  

NASA Astrophysics Data System (ADS)

First-principles calculations are used to study the structural, electronic and magnetic properties of (Pd, Pt)-Mn-Ni-(Ga, In, Sn, Sb) alloys which display multifunctional properties like the magnetic shape-memory, magnetocaloric and exchange bias effect. The ab initio calculations give a basic understanding of the underlying physics which is associated with the complex magnetic behavior (also spin glass) arising from competing ferro- and antiferromagnetic interactions with increasing number of Mn excess atoms in the unit cell. This information allows to optimize, for example, the magnetocaloric effect by using the strong influence of compositional changes on the magnetic interactions. Thermodynamic properties can be calculated by using the ab initio magnetic exchange parameters in finite-temperature Monte Carlo simulations. We present guidelines of how to improve the functional properties. For Pt-Ni-Mn-Ga alloys, a shape memory effect with 14% strain can be achieved in an external magnetic field.

Gruenebohm, Anna; Entel, Peter; Herper, Heike C.; Gruner, Markus E.; Hucht, Alfred; Comtesse, Denis; Arroyave, Raymundo

2013-03-01

17

A novel 18-metallacrown-6 complex: Synthesis, structural characterization and magnetic properties  

NASA Astrophysics Data System (ADS)

The novel 18-metallacrown-6 complex, with the formula of [Mn 6(C 11H 11N 2O 3) 6(CH 3CH 2OH) 6]·3C 3H 7NO·2CH 3CH 2OH ( 1) (pmshz = N-propanoyl-3-methyl-salicylhydrazide), has been prepared and characterized. The self-assembled, manganese complex assumes a nearly planar cyclic structure with an [Mn-N-N] 6 backbone. Due to the coordination, the ligand enforces the stereochemistry of the Mn 3+ ions as a propeller shape with alternating …????… configurations. The magnetic properties of the metallacrown molecule are characterized by a weak antiferromagnetic exchange interaction between the Mn 3+ ion spins with S = 2 in the cyclic system.

Shu, Tian-Pin; Wen, Jun-Long; Feng, Hai-Mei; Lei, Ke-Wei; Liang, Hong-Ze

2009-11-01

18

New divalent manganese complex with pyridine carboxylate N-oxide ligand: Synthesis, structure and magnetic properties  

NASA Astrophysics Data System (ADS)

Two new manganese complexes, [Mn 3( L1) 4(NO 3) 2] n ( 1, H L1=nicotinate N-oxide acid) and [Mn L2Cl] n ( 2, H L2=isonicotinate N-oxide acid)], have been hydrothermally synthesized and characterized by elemental analysis, IR and single-crystal X-ray diffraction. In 1, the L1 ligands take two different coordinated modes bridging four and three Mn II ions. The nitrate anions take chelating coordination modes, leading one type of the Mn II ions as a 4-connected node. The whole net can be viewed as a 3, 4, 6-connected 4-nodal net with Schläfli notation {4 3}2{4 4; 6 2}4{4 6; 6 6; 8 3}. Complex 2 has a honeycomb layer mixed bridged by chlorine, N-oxide and carboxylate. The adjacent layers are linked by the phenyl ring of L2 ligand, giving a 3D framework with a {3 4; 5 4} {3 2;4;5 6;6 6} 4, 6-connect net. Magnetic studies indicate that 1 is an antiferromagnet with low-dimensional characteristic, in which a - J1J1J2- coupled alternating chain is predigested. Fitting the data of 1 gives the best parameters J1=-2.77, J2=-0.67 cm -1. The magnetic properties of complex 2 represent the character of the 2D honeycomb layer with the J1=-2.05 and J2=0.55 cm -1, which results in a whole antiferromagnetic state.

Liu, Fu-Chen; Xue, Min; Wang, Hai-Chao; Ou-Yang, Jie

2010-09-01

19

"Switching on" the properties of single-molecule magnetism in triangular manganese(III) complexes.  

PubMed

The reaction between oxide-centered, triangular [MnIII3O(O2CR)6(py)3](ClO4) (R = Me (1), Et (2), Ph (3)) compounds and methyl 2-pyridyl ketone oxime (mpkoH) affords a new family of Mn/carboxylato/oximato complexes, [MnIII3O(O2CR)3(mpko)3](ClO4) [R = Me (4), Et (5), and Ph (6)]. As in 1-3, the cations of 4-6 contain an [MnIII3(mu3-O)]7+ triangular core, but with each Mn2 edge now bridged by an eta1:eta1:mu-RCO2- and an eta1:eta1:eta1:mu-mpko- group. The tridentate binding mode of the latter causes a buckling of the formerly planar [MnIII3(mu3-O)]7+ core, resulting in a relative twisting of the three MnIII octahedra and the central O2- ion now lying approximately 0.3 A above the Mn3 plane. This structural distortion leads to ferromagnetic exchange interactions within the molecule and a resulting S = 6 ground state. Fits of dc magnetization data for 4-6 collected in the 1.8-10.0 K and 10-70 kG ranges confirmed S = 6 ground states, and gave the following D and g values: -0.34 cm(-1) and 1.92 for 4, -0.34 cm(-1) and 1.93 for 5, and -0.35 cm(-1) and 1.99 for 6, where D is the axial zero-field splitting (anisotropy) parameter. Complexes 4-6 all exhibit frequency-dependent out-of-phase (chi" M) ac susceptibility signals suggesting them possibly to be single-molecule magnets (SMMs). Relaxation rate vs T data for complex 4 down to 1.8 K obtained from the chi" M vs T studies were supplemented with rate vs T data measured to 0.04 K via magnetization vs time decay studies, and these were used to construct Arrhenius plots from which was obtained the effective barrier to relaxation (Ueff) of 10.9 K. Magnetization vs dc field sweeps on single-crystals of 4.3CH2Cl2 displayed hysteresis loops exhibiting steps due to quantum tunneling of magnetization (QTM). The loops were essentially temperature-independent below approximately 0.3 K, indicating only ground-state QTM between the lowest-lying Ms = +/-6 levels. Complexes 4-6 are thus confirmed as the first triangular SMMs. High-frequency EPR spectra of single crystals of 4.3CH2Cl2 have provided precise spin Hamiltonian parameters, giving D = -0.3 cm(-1), B40 = -3 x 10(-5) cm(-1), and g = 2.00. The spectra also suggest a significant transverse anisotropy of E > or = 0.015 cm(-1). The combined work demonstrates the feasibility that structural distortions of a magnetic core imposed by peripheral ligands can "switch on" the properties of an SMM. PMID:17622145

Stamatatos, Theocharis C; Foguet-Albiol, Dolos; Lee, Sheng-Chiang; Stoumpos, Constantinos C; Raptopoulou, Catherine P; Terzis, Aris; Wernsdorfer, Wolfgang; Hill, Stephen O; Perlepes, Spyros P; Christou, George

2007-08-01

20

Electronic and magnetic properties of bimetallic ytterbocene complexes: the impact of bridging ligand geometry.  

PubMed

Bimetallic ytterbocene complexes with bridging N-heterocylic ligands have been studied extensively in recent years due to their potential applications ranging from molecular wires to single-molecule magnets. Herein, we review our recent results for a series of ytterbocene polypyridyl bimetallic complexes to highlight the versatility and tunability of these systems based on simple changes in bridging ligand geometry. Our work has involved structural, electrochemical, optical, and magnetic measurements with the goal of better understanding the electronic and magnetic communication between the two ytterbium metal centers in this new class of bimetallics. PMID:17924595

Carlson, Christin N; Veauthier, Jacqueline M; John, Kevin D; Morris, David E

2008-01-01

21

Synthesis, structure and magnetic properties of a novel lead(II) complex containing nitronyl nitroxide radicals  

Microsoft Academic Search

The lead(II) complex with nitronyl nitroxide, [Pb(NIT2Py)2(NO3)2] [NIT2Py=2-(2?-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide], has been prepared and characterized by magnetic and single-crystal X-ray diffraction studies. In the complex, the lead(II) ion is coordinated with two bidentate nitronyl nitroxide and two nitrate anions. The lead(II) ion shows seven-coordinate geometry. Magnetic susceptibility data for the title complex has been measured in the range 5–300K. There are antiferromagnetic

Li-Ya Wang; Yu-Fang Wang; Lu-Fang Ma

2007-01-01

22

Magnetic and transport properties of the giant-unit-cell Al 3.26Mg 2 complex metallic alloy  

Microsoft Academic Search

The ?-Al3Mg2 complex metallic alloy comprises about 1168 atoms in the giant-unit cell, making this material excellent candidate to investigate how the exceptional structural complexity and the coexistence of two different length scales – one defined by the unit-cell parameters and the other by the cluster substructure – affect physical properties of a metallic material. We have investigated magnetic, electrical,

J. Dolinšek; T. Apih; P. Jegli?; I. Smiljani?; A. Biluši?; Ž. Bihar; A. Smontara; Z. Jagli?i?; M. Heggen; M. Feuerbacher

2007-01-01

23

Synthesis, Crystal Structure and Magnetic Property of a Complex Containing Silver Ions with Thiazole?substituted Nitronyl Nitroxide Radicals  

Microsoft Academic Search

The synthesis, crystal structure and magnetic properties of a novel diamagnetic metal complex with thiazole?substituted nitronyl nitroxide radicals, [Ag (NIT2?thz)2](NO3) (NIT2?thz=2?(2??thiazole)?4,4,5,5?tetramethylimidazoline?1?oxyl?3?oxide), is reported. The structure of the complex consists of tetracoordinated [Ag (NIT2?thz)2] cations and uncoordinated nitrate anions. The radical behaves as a bidentate chelating ligand through one nitronyl nitroxide oxygen and the thiazole nitrogen. Magnetic susceptibility data showed that

Chen-Xi Zhang; Yuying Zhang

2007-01-01

24

Magnetic properties of La–Co substituted M-type strontium hexaferrites prepared by polymerizable complex method  

Microsoft Academic Search

Magnetic properties of La–Co substituted M-type strontium hexaferrites were studied. The samples were prepared by polymerizable complex method. Crystal structure of samples has been investigated by powder X-ray diffraction (XRD). Single-phase M-type strontium hexaferrites with chemical composition of Sr1.05?xLaxFe12?xCoxO19 (x=0–0.4) were formed by heating at 1173K for 24h in air. Magnetic properties were discussed by measurements of M–H curves with

Takeyuki Kikuchi; Tatsuya Nakamura; Tohru Yamasaki; Makoto Nakanishi; Tatsuo Fujii; Jun Takada; Yasunori Ikeda

2010-01-01

25

Magnetic properties and chiral states of a trimetallic uranium complex.  

PubMed

The magnetic properties of the triangular molecular nanomagnet [UO2L]3 (L = 2-(4-tolyl)-1,3-bis(quinolyl)malondiiminate) have been investigated through electron paramagnetic resonance spectroscopy, high-field magnetization and susceptibility measurements. The experimental findings are well reproduced by a microscopic model including exchange interactions and local crystal fields. These results show that [UO2L]3 is characterized by a non-magnetic ground doublet corresponding to two oppositely twisted chiral arrangements of the uranium moments. The non-axial character of single-ion crystal fields leads to quantum tunneling of the noncollinear magnetization in the presence of a magnetic field applied perpendicularly to the triangle plane. PMID:24169692

Carretta, S; Amoretti, G; Santini, P; Mougel, V; Mazzanti, M; Gambarelli, S; Colineau, E; Caciuffo, R

2013-12-01

26

Magnetic properties of the tetranitrosyl-iron complex Fe2(SC3H5N2)2(NO)4  

NASA Astrophysics Data System (ADS)

The magnetic properties of the binuclear nitrosyl-iron complexes Fe2(SC3H5N2)2(NO)4 are investigated. It is demonstrated that several types of particles, such as dimers with a pair of spins 1/2, dimers with a pair of spins 5/2, and paramagnetic particles with spin 3/2, make a contribution to the magnetic properties of the complexes. A decrease in the temperature below 25 K leads to a change in the shape of the EPR spectra corresponding to these dimers, so that Lorentzian lines (homogeneous broadening) transform into Gaussian lines (inhomogeneous broadening). This is accompanied by a stepwise change in the EPR line width and g factors. The change in the line shape indicates that complexes become asymmetric at low temperatures, possibly, due to the decrease in the spin exchange frequency below the frequency of the microwave field of the spectrometer.

Morgunov, R. B.; Kurganova, E. V.; Aldoshin, S. M.; Sanina, N. A.; Rudneva, T. N.

2007-09-01

27

Preparation and magnetic properties of iron(3+) spin-crossover complexes bearing a thiophene substituent: toward multifunctional metallopolymers.  

PubMed

The synthesis of a new 3-ethynylthienyl-substituted QsalH ligand (QsalH is the short form for N-(8-quinolyl)salicylaldimine) (ThEQsalH 3), and the preparation, electronic, and magnetic properties of three homoleptic and cationic iron(3+) complexes containing this ligand with PF(6)(-) 4, SCN(-) 5, and ClO(4)(-) 6 counteranions are reported. In all three complexes a spin-crossover is observed in the solid state by variable temperature magnetic susceptibility measurements and Mossbauer spectroscopy, indicating that the synthetic modification of the QsalH ligand has not significantly altered the electronics at the metal center. This includes the observation of a very rare S = 5/2 to 3/2 spin-crossover in a non-porphyrin iron(3+) complex 5. The molecular structure and magnetic properties of an unusual iron(2+) complex 7 generated by reduction of complex 6 serendipitously during a recrystallization attempt in aerobic acetone solution is also reported. Complexes 4-6 feature iron(3+) reduction and oxidation of the thiophene ring at potentials of approximately -0.7 and +1.2 V (vs Fc), respectively. PMID:19053331

Djukic, Brandon; Dube, Paul A; Razavi, Fereidoon; Seda, Takele; Jenkins, Hilary A; Britten, James F; Lemaire, Martin T

2009-01-19

28

Magnetic properties of poly(propylene imine)-copper dendromesogenic complexes: An EPR study.  

PubMed

Copper(II) complexes formed by coordination of the Cu(II) ion with liquid-crystalline poly(propylene imine) dendrimer ligand (L) of the first (complex 1) and second (complex 2) generations with various Cu(II) contents (x = Cu/L) have been studied by electron paramagnetic resonance (EPR) spectroscopy. The existence of a redox-active blue complex 1 (x = 1.9) and the copper(II) nitrate electron transfer associated with the valence tautomerism are revealed for the first time in copper-based dendrimers. It has been shown that the electronic structure of the blue complex 1 (x = 1.9) is adequately described as a mixed-valence dimer containing d9- and diamagnetic d10-configurated copper ions, and an antiferromagnetically coupled NO3* radical arising on the nitrate-bridged counter ligand. The activation energy value found for the electron transfer is about 0.35 meV, which indicates a low-energy charge dynamic. The ability of the blue and green complexes 1 (x = 1.9) dissolved in isotropic solvents to orient themselves in the magnetic field was revealed by EPR spectroscopy. The degree of orientation of the molecular z axis (S(z)) of these complexes in the magnetic field differs, depending on the type of copper(II)-complexing site in the dendrimer ligand, and can reach 0.76, which is close to S(z) = 1 (completely aligned system). A combination of magnetic and orientational parameters indicates an NO4 environment of the Cu(II) ion in green complex 1 (x = 1.9), and confirms the chain structure with intermolecular Cu(II)-NO3-Cu(II) bridges between Cu(II) centres in columns. PMID:17089431

Domracheva, Natalia; Mirea, Anisoara; Schwoerer, Markus; Torre-Lorente, Laura; Lattermann, Günter

2006-12-11

29

Magnetic Properties and Electronic Structure of Neptunyl(VI) Complexes: Wavefunctions, Orbitals, and Crystal-Field Models.  

PubMed

The electronic structure and magnetic properties of neptunyl(VI), NpO2 (2+) , and two neptunyl complexes, [NpO2 (NO3 )3 ](-) and [NpO2 Cl4 ](2-) , were studied with a combination of theoretical methods: ab initio relativistic wavefunction methods and density functional theory (DFT), as well as crystal-field (CF) models with parameters extracted from the ab initio calculations. Natural orbitals for electron density and spin magnetization from wavefunctions including spin-orbit coupling were employed to analyze the connection between the electronic structure and magnetic properties, and to link the results from CF models to the ab initio data. Free complex ions and systems embedded in a crystal environment were studied. Of prime interest were the electron paramagnetic resonance g-factors and their relation to the complex geometry, ligand coordination, and nature of the nonbonding 5f orbitals. The g-factors were calculated for the ground and excited states. For [NpO2 Cl4 ](2-) , a strong influence of the environment of the complex on its magnetic behavior was demonstrated. Kohn-Sham DFT with standard functionals can produce reasonable g-factors as long as the calculation converges to a solution resembling the electronic state of interest. However, this is not always straightforward. PMID:24848696

Gendron, Frédéric; Páez-Hernández, Dayán; Notter, François-Paul; Pritchard, Ben; Bolvin, Hélène; Autschbach, Jochen

2014-06-23

30

Synthesis, Crystal Structures and Magnetic Properties of a Cobalt Complex with Nitronyl Nitroxide Radical  

Microsoft Academic Search

A cobalt complex with nitronyl nitroxide, Co(hfac)2(NITPh-p-Br)2 (hfac = hexafluoroacetylacetonate; NITPh-p-Br = 2-(4-bromophenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) was synthesized. The complex has been investigated by X-ray crystal diffraction and magnetic susceptibility measurements. The crystal structure consists of Radical-Co-Radical tri-spin units, in which central Co(II) ion is coordinated by four oxygen atoms from two hfac and two oxygen atoms from the NITPh-p-Br. Furthermore, dimmer structure

Chen-Xi Zhang; Xiang-Yu Zhao; Wen-Min Wang; Yu-Ying Zhang

2012-01-01

31

Synthesis, Crystal Structures, and Magnetic Properties of a Cobalt Complex With Nitronyl Nitroxide Radical  

Microsoft Academic Search

A cobalt complex with nitronyl nitroxide, Co(hfac)2(NITPh-p-Br)2 (hfac = hexafluoroacetylacetonate; NITPh-p-Br = 2-(4?- bromophenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), was synthesized. The complex has been investigated by X-ray crystal diffraction and magnetic susceptibility measurements. The crystal structure consists of Radical-Co-Radical tri-spin units, in which the central Co(II) ion is coordinated by four oxygen atoms from two hfac and two oxygen atoms from the NITPh-p-Br. Furthermore,

Chen-Xi Zhang; Hai-Wen Chen; Wen-Min Wang; Yu-Ying Zhang

2012-01-01

32

Synthesis, Characterization, and Magnetic Properties of Tetracarboxylato?Bridged Binuclear Iron(II) Complexes  

Microsoft Academic Search

Four new binuclear iron(II) complexes with a tetracarboxylato?bridge have been synthesized and characterized, namely [Fe2(PMTA)L4], where L denotes 4,7?diphenyl?1,10?phenanthroline (Ph2?phen); 2,9?dimethyl?1,10?phenanthroline (Me2phen); diaminoethane (en); 1,3?diaminopropane (pn) and PMTA represents the tetraanion of pyromellitic acid. Based on elemental analyses, magnetic moments at room?temperature and molar conductivity measurements, spectroscopic (electronic and IR spectra) studies, it is proposed that these complexes have PMTA?bridged

2004-01-01

33

Structures and magnetic properties of transition metal complexes of 1,3,5-benzenetricarboxylic acid  

Microsoft Academic Search

Treatment of the potassium salt of 1,3,5-benzenetricarboxylic acid with transition metal ions in aqueous solution produced a series of coordination complexes. Reaction of Ni(ClO4)2·6H2O with K3[C6H3(CO2)3] gave complexes 1, Ni3[C6H3(CO2)3]2(H2O)14·4H2O. The compound crystallized as trimers with two terminal Ni(H2O)5 units bridged by two benzenetricarboxylate ligands to a central Ni(H2O)4. Magnetic susceptibility data indicate the presence of either weak antiferromagnetic interactions

Wanru Zhang; Sandra Bruda; Christopher P Landee; Judith L Parent; Mark M Turnbull

2003-01-01

34

Photoinduced single-molecule magnet properties in a four-coordinate iron(II) spin crossover complex.  

PubMed

The four-coordinate Fe(II) complex, PhB(MesIm)3Fe-N?PPh3 (1) has been previously reported to undergo a thermal spin-crossover (SCO) between high-spin (HS, S = 2) and low-spin (LS, S = 0) states. This complex is photoactive below 20 K, undergoing a photoinduced LS to HS spin state change, as determined by optical reflectivity and photomagnetic measurements. With continuous white light irradiation, 1 displays slow relaxation of the magnetization, i.e. single-molecule magnet (SMM) properties, at temperatures below 5 K. This complex provides a structural template for the design of new photoinduced mononuclear SMMs based on the SCO phenomenon. PMID:24313622

Mathonière, Corine; Lin, Hsiu-Jung; Siretanu, Diana; Clérac, Rodolphe; Smith, Jeremy M

2013-12-26

35

Density functional theory study of the magnetic properties of rare earth complexes: the magnetic coupling mechanism in Y III and Gd III complexes with nitronyl nitroxide  

Microsoft Academic Search

The magnetic coupling interactions of the nitronyl nitroxide radicals bound to diamagnetic (YIII) and paramagnetic (GdIII) rare earth ions in two model magnetic systems based on novel rare earth organic radical complexes Ln(hfac)3(NITPhOCH3)2 (Ln = YIII 1, GdIII 2; hafc = hexafluoroacetylacetonate; NITPhOCH3 = 4?-methoxyo-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) have been investigated by density functional theory (DFT).\\u000a The magnetic coupling mechanisms were also explored

Jie Ren; BingWu Wang; ZhiDa Chen

2009-01-01

36

Synthesis and characterization of monomeric Mn (IV) and pseudo-tetrameric Mn (III) complexes: Magnetic properties of Mn (III) complex  

NASA Astrophysics Data System (ADS)

Two novel monomer Mn (IV) [Mn(3,5-ClL1)2]?(CH3OH), (1), [3,5-ClL1H2 = N-(2-hydroxyethyl)-3,5-dichlorosalicylaldimine] (1) and hydrogen-bonded pseudo-tetramer Mn (III) [Mn(5-BrL2)(H2O)2]2?[Mn(5-BrL2)(H2O)]2?2?(ClO4), (2), [5-BrL2H2 = N,N?-bis(5-bromosalicylidenato)-1,2-diamino-2-methylpropane)] (2) Schiff base complexes have been synthesized and their crystal structures have been determined by single crystal X-ray diffraction analysis. A variable temperature magnetic susceptibility measurement study has been performed for complex (2) and the result indicates there is a very weak antiferromagnetic interaction (J = -0.40 ± 0.016 cm-1) between the two manganese (III) centers.

Yahsi, Yasemin; Kara, Hulya

2014-06-01

37

Synthesis and characterization of monomeric Mn (IV) and pseudo-tetrameric Mn (III) complexes: magnetic properties of Mn (III) complex.  

PubMed

Two novel monomer Mn (IV) [Mn(3,5-ClL1)2]?(CH3OH), (1), [3,5-ClL1H2=N-(2-hydroxyethyl)-3,5-dichlorosalicylaldimine] (1) and hydrogen-bonded pseudo-tetramer Mn (III) [Mn(5-BrL2)(H2O)2]2?[Mn(5-BrL2)(H2O)]2?2?(ClO4), (2), [5-BrL2H2=N,N'-bis(5-bromosalicylidenato)-1,2-diamino-2-methylpropane)] (2) Schiff base complexes have been synthesized and their crystal structures have been determined by single crystal X-ray diffraction analysis. A variable temperature magnetic susceptibility measurement study has been performed for complex (2) and the result indicates there is a very weak antiferromagnetic interaction (J=-0.40±0.016cm(-1)) between the two manganese (III) centers. PMID:24632152

Yahsi, Yasemin; Kara, Hulya

2014-06-01

38

Quantitative calculation of magnetic and electric properties in a d2-d3 mixed-valence vanadium dimer complex  

NASA Astrophysics Data System (ADS)

The electronic structure and magnetic properties in the mixed-valence d2-d3 vanadium dimer complex [(PY5Me2)2V2(?-5,6-dmbzim)]4+ under an electric field are investigated by using the density functional theory and the effective Hamiltonian method. With the aim of controlling the localization-delocalization of the excess electron, an electric field is applied in the direction along the two vanadium atoms. The ground state changes with an increase of the electric field from the highest spin S = 5/2 state to the intermediate spin S = 3/2 state, and then it changes to the lowest spin S = 1/2 state. Thus, in this realistic mixed-valence dimer system, the possibility of controlling the spin state by using the electric field is shown. Various magnetic and electric properties of this mixed-valence dimer complex are also calculated using our effective Hamiltonian. The methodology in this paper is quite general and is a useful approach for the calculation of electronic structures in various magnetic complexes.

Suzuki, Hidenori; Satoko, Chikatoshi

2014-01-01

39

Synthesis, magnetic properties, and phosphoesterase activity of dinuclear cobalt(II) complexes.  

PubMed

A series of dinuclear cobalt(II) complexes has been prepared and characterized to generate functional and spectroscopic models for cobalt(II) substituted phosphoesterase enzymes such as the potential bioremediator GpdQ. Reaction of ligands based on 2,2'-(((2-hydroxy-5-methyl-1,3-phenylene)bis(methylene))bis((pyridin-2-ylmethyl)azanediyl)))diethanol (L1) and 2,6-bis(((2-methoxyethyl)(pyridin-2-ylmethyl)amino)methyl)-4-methylphenol (L2) with cobalt(II) salts afforded [Co(2)(CO(2)EtH(2)L1)(CH(3)COO)(2)](PF(6)), [Co(2)(CO(2)EtL2)(CH(3)COO)(2)](PF(6)), [Co(2)(CH(3)L2)(CH(3)COO)(2)](PF(6)), [Co(2)(BrL2)(CH(3)COO)(2)](PF(6)), and [Co(2)(NO(2)L2)(CH(3)COO)(2)](PF(6)). Complexes of the L2 ligands contain a coordinated methyl-ether, whereas the L1 ligand contains a coordinated alcohol. The complexes were characterized using mass spectrometry, microanalysis, X-ray crystallography, UV-vis-NIR diffuse reflectance spectroscopy, IR absorption spectroscopy, solid state magnetic susceptibility measurements, and variable-temperature variable-field magnetic circular dichroism (VTVH MCD) spectroscopy. Susceptibility studies show that [Co(2)(CO(2)EtH(2)L1)(CH(3)COO)(2)](PF(6)), [Co(2)(CO(2)EtL2)(CH(3)COO)(2)](PF(6)), and [Co(2)(CH(3)L2)(CH(3)COO)(2)](PF(6)) are weakly antiferromagnetically coupled, whereas [Co(2)(BrL2)(CH(3)COO)(2)](PF(6)) and [Co(2)(NO(2)L2)(CH(3)COO)(2)](PF(6)) are weakly ferromagnetically coupled. The susceptibility results are confirmed by the VTVH MCD studies. Density functional theory calculations revealed that magnetic exchange coupling occurs mainly through the phenolic oxygen bridge. Implications of geometry and ligand design on the magnetic exchange coupling will be discussed. Functional studies of the complexes with the substrate bis(2,4-dinitrophenyl) phosphate showed them to be active towards hydrolysis of phosphoester substrates. PMID:23374019

Daumann, Lena J; Comba, Peter; Larrabee, James A; Schenk, Gerhard; Stranger, Robert; Cavigliasso, German; Gahan, Lawrence R

2013-02-18

40

Physical properties of magnetic macromolecule-metal and macromolecule-metal oxide nanoparticle complexes  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles are of considerable interest owing to their potential applications in biotechnology and the magnetic recording industry. Iron oxides have received much attention owing to their oxidative stability and biocompatibility; however, other transition metals and their alloys are also under investigation. Cobalt has one of the largest magnetic susceptibilities of these materials, but it readily oxidizes upon exposure to air resulting in antiferromagnetic oxide. Hence, coating cobalt nanoparticles with an oxygen-impermeable sheath would confer numerous benefits. Cobalt nanoparticles were prepared by the thermolysis of dicobalt octacarbonyl in two block copolymer micellar systems, wherein the copolymers were precursors to graphite or silica. Subsequent heat treatment of the samples at 600--700°C was conducted to condense the polymer coating around the cobalt nanoparticles and form oxygen impervious graphite or silica sheaths. Magnetic and structural characterization of these novel materials afforded pertinent information about their physical properties. Magnetic susceptometry indicated that the graphite coated cobalt nanoparticles resisted oxidation far over one year. The silica coated cobalt nanoparticles had high saturated specific magnetic moments, but the coatings were brittle and grinding the particles resulted in oxidation over time. Transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and energy-filtered TEM (EFTEM) were employed to study particle size and structural differences of the cobalt nanoparticles before and after heat treatment. The mean particle size and size distribution increased for the graphite coated cobalt particles, due to particle sintering at 700°C. In the silica coated cobalt nanoparticle system, the mean particle size increased when the sample was heat-treated at 600°C leading to a bimodal distribution. This bimodal distribution was explained by a fraction of the particles sintering, while others remained discrete. When the silica system was heat treated at 700°C, the particle size and size distribution remained similar to those of the pre-heat-treated sample, indicating that no sintering had taken place. The rapid pyrolysis of the polymer at 700°C may serve to lock the cobalt nanoparticles into a silica matrix, thus preventing them from coming into contact with one another and sintering. Several diffraction techniques (selected area electron diffraction (SAD), nano-beam electron diffraction (NBD) and x-ray diffraction (XRD)) were used to probe the crystal structure of graphite and silica coated cobalt nanoparticies, which was determined to be predominantly face-centered cubic. Anisotropic magnetic nanoparticles (nanorods) have an increased magnetophoretic mobility over spherical magnetic nanoparticles with the same equatorial radius. This property makes them attractive candidates for in vivo biological applications. Anisotropic mixed ferrite nanoparticles were coated with a biocompatible hydrophilic block copolymer to render them dispersible in aqueous media. Polymer coated mixed ferrite particles exhibited magnetic properties similar to that of pure magnetite, as the total level of other transition metals in the nanoparticulate system was less than 5%. Electron energy loss spectroscopy (EELS) and (EFTEM) confirmed that the dominant elements in the mixed ferrite nanoparticles were iron and oxygen. Furthermore, HRTEM, SAD and XRD analyses indicated that the crystal structure for the mixed ferrite nanoparticles was inverse spinel. X-ray diffraction peaks at low angles for the coated mixed ferrite rods corresponded to poly(ethylene oxide) peaks, suggesting that the block copolymer employed as a dispersant was associated with the particles.

Zalich, Michael Andrew

41

Synthesis and magnetic properties of nickel(II) complexes with the nitronyl nitroxides  

Microsoft Academic Search

Four novel complexes of nickel(II), Ni(tfac)2(NITPa)2 (1), Ni(tfac)2(NITPhNO2)2 (2), Ni(pfpr)2(NITPa)2 (3) and Ni(pfpr)2(NITPhNO2)2 (4), [tfac=trifluoro- acetato, NITPa=2-(3,4-methylenedioxyphenyl)-4,4,5, 5-tetramethylimidazoline-1-oxy-3-oxid, NITPhNO2= 2-(3-nitrophenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxid, pfpr=pentafluoropropionato], have been prepared and characterized by elemental analysis, i.r., and electronic spectra, and molar conductances. The temperature dependence of the magnetic susceptibility for complexes (1) and (3) was measured (4–300K). The observed data were successfully simulated giving the exchange

Lei Zhang; Su-Qi Li; Xiang-Jun Meng; Dai-Zheng Liao; Zong-Hui Jiang; Gen-Lin Wang; Pan-Wen Shen; Qi-Hua Zhao

1999-01-01

42

Dinuclear Mn(II,II) complexes: magnetic properties and microwave assisted oxidation of alcohols.  

PubMed

A series of six new mixed-ligand dinuclear Mn(II,II) complexes of three different hydrazone Schiff bases (H3L(1), H3L(2) and H3L(3)), derived from condensation of the aromatic acid hydrazides benzohydrazide, 2-aminobenzohydrazide or 2-hydroxybenzohydrazide, with 2,3-dihydroxy benzaldehyde, respectively, is reported. Reactions of Mn(NO3)2·4H2O with the H3L(1-3) compounds, in the presence of pyridine (1?:?1?:?1 mole ratio), in methanol at room temperature, yield [Mn(H2L(1))(py)(H2O)]2(NO3)2·2H2O (1·2H2O), [Mn(H2L(2))(py)(CH3OH)]2(NO3)2·4H2O (2·4H2O) and [Mn(H2L(3))(py)(H2O)]2(NO3)2 (3) respectively, whereas the use of excess pyridine yields complexes with two axially coordinated pyridine molecules at each Mn(II) centre, viz. [Mn(H2L(1))(py)2]2(NO3)2·H2O (4·H2O), [Mn(H2L(2))(py)2]2(NO3)2·2H2O (5·2H2O) and [Mn(H2L(3))(py)2]2(NO3)2·2CH3OH (6·2CH3OH), respectively. In all the complexes, the (H2L(1-3))(-) ligand coordinates in the keto form. Complexes 1·2H2O, 2·4H2O, 4·H2O, 5·2H2O and 6·2CH3OH are characterized by single crystal X-ray diffraction analysis. The complexes 1, 2 and 6, having different coordination environments, have been selected for variable temperature magnetic susceptibility measurements to examine the nature of magnetic interaction between magnetically coupled Mn(II) centres and also for exploration of the catalytic activity towards microwave assisted oxidation of alcohols. A yield of 81% (acetophenone) is obtained using a maximum of 0.4% molar ratio of catalyst relative to the substrate in the presence of TEMPO and in aqueous basic solution, under mild conditions. PMID:24452284

Sutradhar, Manas; Martins, Luísa M D R S; Guedes da Silva, M Fátima C; Alegria, Elisabete C B A; Liu, Cai-Ming; Pombeiro, Armando J L

2014-03-14

43

Complex-temperature properties of the two-dimensional Ising model for nonzero magnetic field  

NASA Astrophysics Data System (ADS)

We study the complex-temperature phase diagram of the square-lattice Ising model for nonzero external magnetic field H, i.e., for 0<=?<=?, where ?=e-2?H. We also carry out a similar analysis for -?<=?<=0. The results for the interval -1<=?<=1 provide a way of continuously connecting the two known exact solutions of this model, viz., at ?=1 (Onsager, Yang) and ?=-1 (Lee and Yang). Our methods include numerical calculations of complex-temperature zeros of the partition function and an analysis of low-temperature series expansions. For real nonzero H, the inner branch of a limaçon bounding the FM phase breaks and forms two complex-conjugate arcs. We study the singularities and associated exponents of thermodynamic functions at the endpoints of these arcs. For ?<0, there are two line segments of singularities on the negative and positive u axis, and we carry out a similar study of the behavior at the inner endpoints of these arcs, which constitute the nearest singularities to the origin in this case. Finally, we also determine the exact complex-temperature phase diagrams at ?=-1 on the honeycomb and triangular lattices and discuss the relation between these and the corresponding zero-field phase diagrams.

Matveev, Victor; Shrock, Robert

1996-01-01

44

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

45

Characterizing the Effect of Temperature and Magnetic Field Strengths on the Complex Shear Modulus Properties of Magnetorheological (mr) Fluids  

NASA Astrophysics Data System (ADS)

When a magnetic field is applied across MR fluids, a yield stress is developed, and their rheological properties can then be categorized into two distinct regimes; pre-yield and post-yield. This paper concerns the viscoelastic behaviour of MR fluids in the pre-yield region. Oscillatory tests were carried out to determine the complex shear modulus properties of MR fluids between the temperature range of -20°C and +50°C. The test results show that the storage modulus and loss modulus increased in value as the excitation frequency was increased from 5Hz to 50Hz. The complex modulus was also found to be influenced by changes in temperature; the higher the temperature, the lower the complex modulus. This is consistent with the behaviour of viscoelastic polymers. The sets of temperature-dependent and frequency-dependent data were subsequently condensed using the method of reduced variables into master curves of complex modulus which effectively extended the frequency coverage of the data at the reference temperature.

Chooi, W. W.; Oyadiji, S. O.

46

Preparation and magnetic properties of metal-complexes from N-t-butyl-N-oxidanyl-2-amino-(nitronyl nitroxide).  

PubMed

Metal complexation reactions of N-t-butyl-N-oxidanyl-2-amino(nitronyl nitroxide) diradical (1) with M(hfac)2 (M: Mn or Cu) were investigated. These reactions were found to be very sensitive to the type of metal ion employed. Complex [Mn(hfac)2·1], consisting of Mn(hfac)2 and diradical 1, was readily prepared by mixing the components. However, the reaction of Cu(hfac)2 with 1 or N-t-butyl-N-oxidanyl-2-amino(iminonitroxide) diradical (2) involved the reduction of the diradical to the N-t-butyl-N-oxidanide-2-amino(iminonitroxide) radical anion (3) and finally produced the polymer-chain complex [Cu2(hfac)2·32·Cu(hfac)2]n. The structures of these complexes were elucidated by X-ray analysis, and their magnetic properties were investigated in detail. The temperature dependence of ?pT (?p: magnetic susceptibility) for [Mn(hfac)2·1] exhibited a strong antiferromagnetic interaction (H = -2JS1·S2, J/kB = -217 K) between the Mn(II) spin (S = 5/2) and the diradical 1 spin (S = 1). However, the ?pT-T plots for [Cu2(hfac)2·32·Cu(hfac)2]n indicated the presence of several magnetic interactions: a large ferromagnetic interaction (J/kB = 510 K) between iminonitroxide 3 and the imino-coordinating Cu(II) atom, a moderately large ferromagnetic interaction (J/kB = 58 K) between the iminonitroxide and (iminonitroxide oxygen)-coordinating Cu(hfac)2, and a weak antiferromagnetic interaction (J/kB = -1.4 K) between the two Cu(hfac)-3 moieties within a Cu2O2 square. PMID:24364815

Furui, Takanori; Suzuki, Shuichi; Kozaki, Masatoshi; Shiomi, Daisuke; Sato, Kazunobu; Takui, Takeji; Okada, Keiji; Tretyakov, Evgeny V; Tolstikov, Svyatoslav E; Romanenko, Galina V; Ovcharenko, Victor I

2014-01-21

47

Synthesis, crystal structure and magnetic properties of a novel complex containing a diamagnetic metal ion and thiazole-substituted nitronyl nitroxide radicals  

Microsoft Academic Search

The synthesis, crystal structure and magnetic properties of a novel diamagnetic metal complex containing thiazole-substituted nitronyl nitroxide radicals, [HgCl2(NIT2-thz)2] (NIT2-thz?= 2-(2?-thiazole)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), is reported. The mercury(II) ion has distorted tetrahedral coordination involving two chloride atoms and two thiazole nitrogen atoms. Magnetic susceptibility data show that there are intramolecular antiferromagnetic interactions between the radicals in the complex.

Li-Ya Wang; Chen-Xi Zhang; Dai-Zheng Liao; Zong-Hui Jiang; Shi-Ping Yan

2005-01-01

48

Cationic assembly of metal complex aggregates: structural diversity, solution stability, and magnetic properties.  

PubMed

The tetradentate imino-carboxylate ligand [L](2)(-) chelates the equatorial sites of Ni(II) to give the complex [Ni(L)(MeOH)(2)] in which a Ni(II) center is bound in an octahedral coordination environment with MeOH ligands occupying the axial sites. Lanthanide (Ln) and Group II metal ions (M) template the aggregation of six [Ni(L)] fragments into the octahedral cage aggregates (M[Ni(L)](6))(x)(+) (1: M = Sr(II); x = 2,2: M = Ba(II); x = 2, 3: M = La(III); x = 3, 4: M = Ce(III); x = 3, 5: M = Pr(III); x = 3, and 6: M = Nd(III); x = 3). In the presence of Group I cations, however, aggregates composed of the alkali metal-oxide cations template various cage compounds. Thus, Na(+) forms the trigonal bipyramidal [Na(5)O](3+) core within a tricapped trigonal prismatic [Ni(L)](9) aggregate to give ((Na(5)O) subset [Ni(L)](9)(MeOH)(3))(BF(4))(2).OH.CH(3)OH, 7. Li(+) and Na(+) together form a mixed Li(+)/Na(+) core comprising distorted trigonal bipyramidal [Na(3)Li(2)O](3+) within an approximately anti-square prismatic [Ni(L)](8) cage in ((Na(3)Li(2)O) subset [Ni(L)](8)(CH(3)OH)(1.3)(BF(4))(0.7))(BF(4))(2.3).(CH(3)OH)(2.75).(C(4)H(10)O)(0.5), 8, while in the presence of Li(+), a tetrahedral [Li(4)O](2+) core within a hexanuclear open cage [Ni(L)](6) in ((Li(4)O) subset [Ni(L)](6)(CH(3)OH)(3))2ClO(4).1.85CH(3)OH, 9, is produced. In the presence of H(2)O, the Cs(+) cation induces the aggregation of the [Ni(L)(H(2)O)(2)] monomer to give the cluster Cs(2)[Ni(L)(H(2)O)(2)](6).2I.4CH(3)OH.5.25H(2)O, 10. Analysis by electronic spectroscopy and mass spectrometry indicates that in solution the trend in stability follows the order 1-6 > 7 > 8 approximately 9. Magnetic susceptibility data indicate that there is net antiferromagnetic exchange between magnetic centers within the cages. PMID:12889978

Lin, Xiang; Doble, Dan M J; Blake, Alexander J; Harrison, Andrew; Wilson, Claire; Schröder, Martin

2003-08-01

49

Influence of structural factors on the magnetic properties of the binuclear copper complexes with salicylaldehyde hydrazone and bis(hydrazone)-2,6-diformylphenol: Quantum-chemical calculations  

Microsoft Academic Search

The structures and magnetic properties of the binuclear copper complexes of salicylaldehyde mono- and bis(hydrazone) derivatives\\u000a were studied by the quantum-chemical density functional theory (B3LYP\\/6-311++g(d,p)) using the broken-symmetry technique. The change in the degree of deprotonation of the ligands was found to exert an insignificant\\u000a effect on the magnetic properties, whereas the coordination of solvent molecules substantially weakened the antiferromagnetic

A. G. Starikov; V. A. Kogan; V. V. Lukov; V. I. Minkin; R. M. Minyaev

2009-01-01

50

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

51

Synthesis, structure, magnetic properties and DFT calculations of two hydroxo-bridged complexes based on Mn(III)(Schiff-Bases).  

PubMed

Two hydroxo-bridged complexes, {[Mn(III)(3-CH(3)O)salen](2)[Cr(III)(salen)(OH)(2)]}ClO(4)·6H(2)O (1) and {[Mn(III)(5-CH(3))salen](2)(OH)}ClO(4)·3H(2)O (2) [salen = N,N'-ethylenebis(salicylideneiminato) dianion], have been synthesized by the hydrolysis of the corresponding Mn(III)(Schiff-Bases) derivatives and [Cr(salen)(H(2)O)(2)]Cl precursors. X-Ray structure characterization reveals the discrete linear arched trinuclear structure of 1 and the 1D chain arrangement of 2. Magnetic experimental data and density functional theory (DFT) calculations both indicate the dominant antiferromagnetic interaction mediated by the hydroxo-bridges in both 1 and 2. Frequency-dependent AC susceptibilities reveal slow relaxation of 1 in low temperature. It is worth noting that the structure and magnetic properties of 1 is comparable to a reported cyano-bridged SMM, K[(5-Brsalen)(2)(H(2)O)(2)Mn(2)Cr(CN)(6)]·2H(2)O. PMID:21541410

Zhou, Hong-Bo; Wang, Hui-Sheng; Chen, Ying; Xu, Yong-Lu; Song, Xiao-Jiao; Song, You; Zhang, Yi-Quan; You, Xiao-Zeng

2011-06-14

52

Magnetic properties of the Old Crow tephra: Identification of a complex iron titanium oxide mineralogy  

Microsoft Academic Search

The mineralogy and grain-size distribution of the Fe-Ti oxide population of the Old Crow tephra bed, outcropping at the Halfway House loess deposit in central Alaska, are characterized through multiple low- and high-temperature magnetization experiments. The characterization is facilitated by heavy liquid separation of the bulk sample into a low-density ( 0.8 and may play an equally important role as

Subir K. Banerjee; Mike J. Jackson

2004-01-01

53

Magnetic properties of the Old Crow tephra: Identification of a complex iron titanium oxide mineralogy  

Microsoft Academic Search

The mineralogy and grain-size distribution of the Fe-Ti oxide population of the Old Crow tephra bed, outcropping at the Halfway House loess deposit in central Alaska, are characterized through multiple low- and high-temperature magnetization experiments. The characterization is facilitated by heavy liquid separation of the bulk sample into a low-density (<2850 kg\\/m3, LD) and high-density (>=2850 kg\\/m3, HD) fraction. Three

Subir K. Banerjee; Mike J. Jackson

2004-01-01

54

Synthesis, crystal structures and magnetic properties of transition metal dicyanamide complexes coordinated with pyridyl nitronyl nitroxides  

Microsoft Academic Search

Two novel complexes Ni(NITpPy)2[N(CN)2]2 ? 2H2O (I) and Zn(NITpPy)2[N(CN)2]2 ? 2H2O (II) (NITpPy = 2-(p-pyridyl)-4,4,5,5- tetramethylimidazoline-1-oxyl-3-oxide) were synthesized and characterized by infrared spectra, elemental\\u000a analyses, and UV-Vis techniques. The crystal structures of both complexes have been determined by X-ray diffraction analysis.\\u000a Both complexes are of centrosymmetric distorted octahedral co-ordination geometry in which metal ions are bound to two dicyanamide\\u000a anions,

Q. H. Zhao; D. Y. Tang; L. Du; R. B. Fang

2007-01-01

55

Syntheses, crystal structures, magnetic properties of two lanthanide-nitronyl nitroxide complexes (Ln III = Gd ?, Pr ?)  

Microsoft Academic Search

Two complexes based on rare-earth-radical of formula {Ln(hfac)3[NITPh(OCH3)3]2} (Ln=Gd (1), Pr(2)); hfac=hexafluoroacetylacetonate; NITPh(OCH3)3=2-(3?,4?,5?-trimethoxyphenyl)-4,4,5,5-tetramethylimidazoline -1-oxyl-3-oxide) have been synthesized and characterized by single-crystal X-ray diffraction. The single-crystal structures show that two complexes have similar structures, in which the metal ions are eight-coordinated in slightly distorted dodecahedron geometry. Two oxygen atoms of the N–O group from nitronyl nitroxide radicals and six oxygen atoms

Chen-Xi Zhang; Na-Na Sun; Xiang-Yu Zhao; Yu-Ying Zhang; Yan-Ling Guo

2011-01-01

56

Structures and Magnetic Properties of Dinuclear Oxovanadium(IV) Complexes with Tris(µ-diphenylphosphinato)-bridges  

Microsoft Academic Search

Novel dinuclear oxovanadium(IV) complexes with tris(µ-phosphinato)-bridges, [(VO) 2 (dpp) 3 (bpy) 2 ]NO 3 ·2H 2 O ( 1 ), [(VO) 2 (dpp) 3 (phen) 2 ]NO 3 ·H 2 O ( 2 ) and [(VO) 2 (bmp) 3 (bpy) 2 ]NO 3 ·H 2 O ( 3 ) (Hdpp=diphenylphosphinic acid, Hbmp=bis(4-methoxyphenyl)phosphinic acid, bpy=2,2'-bipyridine, phen=1,10-phenanthroline), have been prepared and structurally

Seiichi Kawasaki; Masayuki Koikawa; Tadashi Tokii

2002-01-01

57

Crystal Structures and Magnetic Properties of Hydrogen-Bonded Nitronyl Nitroxide Radicals and Their Metal Complexes  

Microsoft Academic Search

Nitronyl nitroxide derivatives showing hydrogen-bonded structures in the solid state have been prepared and characterized. In the complex of p -hydroxyphenyl nitronyl nitroxide with 1,2-Bis(diphenylphosphinoyl)ethane ( 1 ), water molecules are bridging the two organic components, forming a hetero-chain structure. 3,5-Dimethyl-4-hydroxyphenyl nitronyl nitroxide ( 2 ) and pyridone-substituted nitronyl nitroxide ( 3 ) were also prepared and shown to have

Mikio Ueda; Tomoyuki Mochida; Sachie Furukawa; Hideaki Suzuki; Hirosi Moriyama; Hatsumi Mori

2003-01-01

58

Unprecedented nitronyl nitroxide bridged 3d-4f complexes: structure and magnetic properties.  

PubMed

Two novel 2p-3d-4f compounds, {Ln(hfac)3[Cu(hfac)2]3(NITPhPyrim)2} [Ln = Gd (1), Dy (2)], have been obtained by reacting phenyl pyrimidyl nitronyl nitroxide with Cu(hfac)2 and Ln(hfac)3. These two compounds are the first examples of two-dimensional 3d-4f complexes bridged by nitronyl nitroxide radicals. Overall ferromagnetic behaviors were observed in both compounds. PMID:24151811

Zhu, Mei; Li, Yun-Gai; Ma, Yue; Li, Li-Cun; Liao, Dai-Zheng

2013-11-01

59

Synthesis and Magnetic Properties of Copper(II) Complexes Derived from Dihydrazones  

Microsoft Academic Search

A series of new acyldihydrazones, H2L, obtained by condensation of ethylpyruvate with oxalic, malonic, succinic, glutaric and adipic dihydrazides, undergoes quantitative hydrolysis of the ?C(O)OC2H5 group via reactions with copper(II) acetate in alcoholic medium. Dicopper(II) complexes of the general formula [Cu2(L?) · H2O] · xH2O have been isolated, where L? refers to the quadruply deprotonated pyruvic acid dihydrazone ligand and n refers to the

Nahed M. H. Salem

2005-01-01

60

Isolation, structure, and magnetic properties of a novel mononuclear rhodium(II) complex  

SciTech Connect

Our current research interests is the coordination chemistry of solvated polynuclear metal cations, especially the recently reported rhodium(II,II) complex, (Rh{sub 2}(CH{sub 3}CH){sub 4})(F{sub 4}){sub 4}. In order to circumvent the problems associated with preparing and handling aqua species, we have developed a convenient synthesis for the CH{sub 3}CN derivative of RH{sub 2} (vide supra), a compound that allows easy access to other monomeric and polynuclear compounds of Rh(II). We now also report the synthesis of a pseudo-octahedral rhodium(II) monomer stabilized only by two bulky phosphine ligands.

Dunbar, K.R.; Haefner, S.C.; Pence, L.E. (Michigan State Univ., East Lansing (USA))

1989-07-05

61

A one-dimensional azido-bridged manganese(III) complex with bidentate Schiff base: Crystal structure and magnetic properties  

SciTech Connect

The synthesis, structural characterization, and magnetic behavior of a novel one-dimensional azido-bridged manganese(III) complex of formula [Mn(L){sub 2}N{sub 3}] (1) is reported, where HL is the bidentate Schiff base obtained from the condensation of salicylaldehyde with 4-methoxy aniline. Complex 1 crystallizes in the monoclinic system, space group P2{sub 1}/n, with a=11.743(4) A, b=24.986(9) A, c=13.081(5) A, {beta}=95.387(7){sup o} and Z=2. The complex is of one-dimensional chain structure with single end-to-end azido bridges and the manganese(III) ion has an elongated octahedral geometry. Magnetic studies show that the weak antiferromagnetic interaction is mediated by the single end-to-end azido bridge with the exchange parameter J=-5.84 cm{sup -1}. - Graphical abstract: A novel azido-bridged manganese(III) complex with bidentate Schiff base ligands has been prepared and characterized structurally and magnetically. The complex is of one-dimensional chain structure with single end-to-end azido bridges in axial positions. Two bidentate Schiff base ligands coordinate in the equatorial mode. The magnetic measurements show that the complex exhibits weak antiferromagnetic interaction.

Li Wei; Li Zongwei [Department of Chemistry, Nankai University, 94 Weijing Road, Tianjin 300071 (China); Li Licun [Department of Chemistry, Nankai University, 94 Weijing Road, Tianjin 300071 (China); State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002 (China)], E-mail: llicun@nankai.edu.cn; Liao Daizheng; Jiang Zonghui [Department of Chemistry, Nankai University, 94 Weijing Road, Tianjin 300071 (China)

2007-10-15

62

Electron microscopy of iron oxides and implications for the origin of magnetizations and rock magnetic properties of Banded Series rocks of the Stillwater Complex, Montana  

Microsoft Academic Search

The origins of multiple magnetizations of the Archean Stillwater Complex have been investigated through scanning electron microscopy and seamting transmission electron microscopy observations of mineralogieal relations, using representative samples from nine sites in mafic Banded series rocks. On the basis of directional grouping and demagnetization behavior, three magnetizations (here labeled A, B, and C) have been recognized. The natural reinanent

Weixin Xu; John W. Geissman; Rob Van der Voo; Donald R. Peacor

1997-01-01

63

Synthesis, structure and magnetic property of a dihydroxo-bridged dichromium(III) complex with N-(2-pyridylmethyl)iminodiacetate  

Microsoft Academic Search

A dihydroxo-bridged dichromium(III) complex, [Cr2(?-OH)2(pmida)2]·4H2O (pmida=N-(2-pyridylmethyl)iminodiacetate), has been prepared and characterized structurally and magnetically. The complex consists of a three-dimensional network in which [Cr2(?-OH)2(pmida)2] units are alternatively linked by hexacyclic hydrogen-bonded rings adopting the chair conformation. The magnetic susceptibility measured over the range 3–300K shows there is the antiferromagnetic interaction between the two chromium(III) ions. Based on the Hamiltonian written

Li-Zhi Zhang; Yu-Hu Wang; Wen Gu; Xin Liu; Dai-Zheng Liao

2006-01-01

64

Enantiopure tetranuclear iron(III) complexes using chiral reduced Schiff base ligands: synthesis, structure, spectroscopy, magnetic properties, and DFT studies.  

PubMed

Four new tetranuclear iron(III) complexes of formula [{Fe(L)(2)}(3)Fe], 1-4, have been prepared by reacting [Fe(ClO(4))(3)].6H(2)O with H(2)L in methanol. Here, L(2-) is the deprotonated form of N-(2-hyrdoxybenzyl)-l-valinol (H(2)L(1)), N-(2-hyrdoxybenzyl)-l-leucinol (H(2)L(2)), N-(5-chloro-2-hyrdoxybenzyl)-l-leucinol (H(2)L(3)), and N-(2-hyrdoxybenzyl)-l-phenylalaninol (H(2)L(4)). The complexes are prepared in an enantiomeric pure form. The complexes have been characterized with the help of IR, UV-vis, circular dichroism (CD), (1)H, and elemental analyses. The complex [{Fe(L(2))(2)}(3)Fe].CH(3)OH.2H(2)O, 2.CH(3)OH.2H(2)O, crystallizes in enantiomeric pure form containing a propeller-like Fe(4)O(6) core. (1)H and CD spectral studies of the four species are consistent with the structural similarities of the complexes in solution. Variable-temperature magnetic susceptibility of one case shows an intramolecular antiferromagnetic coupling between the Fe(III) ions. Magnetic measurements are in accord with the S = 5 ground state and suggest single molecular magnet behavior. The magnetic exchange coupling constant between the iron centers within the molecule is interpreted using broken-symmetry density functional theory calculation. PMID:19466801

Singh, Reena; Banerjee, Atanu; Colacio, Enrique; Rajak, Kajal Krishna

2009-06-01

65

Novel tetranuclear Ni(II) Schiff base complex containing Ni4O4 cubane core: Synthesis, X-ray structure, spectra and magnetic properties.  

PubMed

Novel tetranuclear nickel(II) Schiff base complex having symmetric Ni4O4 cubane-core, [Ni4O2(OAc)2(L)2] (1) has been synthesized. Single crystal of the complex exhibits four nickel atoms in the alternate corner of the cubane and other four sites are occupied by phenolate-O and ?3-O(2-). Variable temperature magnetic moment data suggests the Ni centres are weakly antiferromagnetically coupled with J1=-4.82cm(-1) and J2=-4.83cm(-1). The electronic spectra, emission properties and life time measurement of ligand, HL and complex 1 have been studied. PMID:24996213

Jana, Mahendra Sekhar; Priego, José L; Jiménez-Aparicio, Reyes; Mondal, Tapan Kumar

2014-12-10

66

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

67

Syntheses, crystal structures and magnetic properties of a new thienyl-substituted nitronyl nitroxide and its copper(II) complex  

Microsoft Academic Search

A new building block for molecule-based magnetic materials???thiophene-substituted nitronyl nitroxide, NIT2-thp, [1, NIT2-thp?=?4,4,5,5-tetramethyl-2-(thiophenal-2-yl)imidazoline-1-oxyl-3-oxide] and its copper(II) complex [Cu(hfac)2]3(NIT2-thp)2 (2) (hfac?=?hexafluoroacetylacetonate) have been synthesized and characterized structurally and magnetically. For 1, dimers were formed and arranged through intermolecular interactions, the shortest contact between nitroxide groups is 4.115?Å among adjacent dimers. In 2 two types of copper interaction with 1 give three

Kai Jiang; Xiaoqiang Wang; Liya Wang; Baoli Zhao

2008-01-01

68

Synthesis, crystal structure and magnetic properties of nickel(II) and cobalt(III) complexes of a pentadentate Schiff base  

NASA Astrophysics Data System (ADS)

Two new Schiff base complexes, [Ni2(HL)2(?1,3-N3)]ClO4·H2O (1) and [Co(L)(N3)] (2) where L = 2,2'-{(methylimino)bis[propane-3,1-diylnitrilomethylylidene]}diphenolate ion, have been synthesized by the reaction of equimolar amounts of nickel(II) or cobalt(II) perchlorate with the pentadentate Schiff base ligand (H2L) in presence of azide ion. The complexes have been characterized by microanalytical, spectroscopic, single crystal X-ray diffraction and other physicochemical studies. Structural studies reveal that 1 is an end-to-end azido-bridged binuclear complex in which each nickel(II) adopts irregular octahedral geometry. In contrast, 2 is a mononuclear octahedral cobalt(III) complex containing the azide ion in one of its apical positions. Low temperature magnetic measurements on 1 indicate noticeable intradimer ferromagnetic interactions.

Layek, Manas; Ghosh, Mahendra; Sain, Saugata; Fleck, Michel; Muthiah, Packianathan Thomas; Jenniefer, Samson Jegan; Ribas, Joan; Bandyopadhyay, Debasis

2013-03-01

69

Magnetic properties of the Fe{sup II} spin crossover complex in emulsion polymerization of trifluoroethylmethacrylate using poly(vinyl alcohol)  

SciTech Connect

Influence of chemical substitution in the Fe{sup II} spin crossover complex on magnetic properties in emulsion polymerization of trifluoroethylmethacrylate using poly(vinyl alcohol) as a protective colloid was investigated near its high spin/low spin (HS/LS) phase transition. The obvious bi-stability of the HS/LS phase transition was considered by the identification of multiple spin states between the quintet (S=2) states to single state (S=0) across the excited triplet state (S=1). Magnetic parameters of gradual shifts of anisotropy g-tensor supported by the molecular distortion of the spin crossover complex would arise from a Jahn-Teller effect regarding ligand field theory on the basis of a B3LYP density functional theory using electron spin resonance (ESR) spectrum and X-ray powder diffraction. - Graphical abstract: AFM surface image of the emulsion particles with the spin crossover complex.

Suzuki, Atsushi, E-mail: suzuki@mat.usp.ac.j [Department of Materials Science, The University of Shiga Prefecture, 2500 Hassaka, Hikone 522-8533 (Japan); Iguchi, Motoi; Oku, Takeo [Department of Materials Science, The University of Shiga Prefecture, 2500 Hassaka, Hikone 522-8533 (Japan); Fujiwara, Motoyasu [Institute for Molecular Science, Okazaki 444-8585 (Japan)

2010-04-15

70

Synthesis, structures, magnetic and optical properties of two lanthanide [Ln=Sm(III), Dy(III)] complexes with chelating nitronyl nitroxide radicals  

Microsoft Academic Search

The synthesis, structures, magnetic and optical properties of two lanthanide complexes with chelating nitronyl nitronide radicals of formula [Ln(III)(NIT2Py)2(NO3)3·xH2O] (Ln=Sm(III) 1, x=0, Dy(III) 2, x=0.25) (NIT2Py=2-(2?-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) are reported. The lanthanide ion of each complex is 10-coordinated with three bidentate nitrate anions and two radicals (NIT2Py). The radical behaves as a bidentate chelating ligand through one nitroxide oxygen atom and one

Dong-jiao Li; Shu-ping Wang; Dai-Zheng Liao; Zong-Hui Jiang; Shi-Ping Yan

2004-01-01

71

Two new end-to-end single dicyanamide bridged Cu(II) complexes with Schiff base ligands: Structural, electrochemical and magnetic properties  

Microsoft Academic Search

The synthesis, crystal structures and magnetic properties of two different copper(II) complexes of formula [Cu(L1)(dca)]n·nClO4 (1) and [Cu(L2)]2(dca)(ClO4) (2) [L1=N,N-dimethylethylene-N?-(pyridine-2-carbaldiiminato), HL2=N,N-dimethylethylene-N?-salicylaldiiminato, dca=dicyanamide anion] are described. Spectroscopic and electrochemical properties have also been discussed. A one-dimensional chain structure with single, symmetrical, ?1,5-dca bridges is found in compound 1. The copper atom in 1 has a square pyramidal geometry. A tridentate Schiff

Ruma Karmakar; Chirantan Roy Choudhury; David L. Hughes; Glenn P. A. Yap; M. Salah El Fallah; Cédric Desplanches; Jean-Pascal Sutter; Samiran Mitra

2006-01-01

72

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

73

Single-molecule magnets: preparation and properties of low symmetry [Mn4O3(O2CPh-R)4(dbm)3] complexes with S = 9/2.  

PubMed

The preparation and properties of [Mn(4)O(3)(O(2)CPh-R)(4)(dbm)(3)] (R = H, p-Me, p-OMe, and o-Cl; dbm(-) is the anion of dibenzoylmethane) single-molecule magnets (SMMs) with virtual C(S) symmetry are reported. They were prepared by controlled potential electrolysis in 26-80% yields. The structures comprise a distorted-cubane core of virtual C(S) symmetry, in contrast to the other, more common complexes of this type with virtual C(3)(V) symmetry. Solid-state magnetic susceptibility data establish the complexes have S = 9/2 ground-state spins, and ac susceptibility studies indicate they are single-molecule magnets (SMMs). Magnetization vs dc field sweeps below 1.00 K reveal hysteresis loops confirming a SMM, with a very large step at zero applied field diagnostic of fast quantum tunneling of magnetization (QTM) through the anisotropy barrier. The fast QTM rate suggested a significant rhombic ZFS parameter E, as expected from the low (virtual C(S)) symmetry. This was confirmed by high-frequency electron paramagnetic resonance spectroscopy on polycrystalline and single-crystal studies. The results confirm the importance of symmetry on the QTM rates. PMID:15453784

Aliaga-Alcalde, Núria; Edwards, Rachel S; Hill, Stephen O; Wernsdorfer, Wolfgang; Folting, Kirsten; Christou, George

2004-10-01

74

Oxamido-bridged heterobinuclear copper(II)–nickel(II) complex and homotrinuclear nickel(II) complex with 2D supramolecular structure: synthesis, crystal structure, magnetic and spectroscopic properties  

Microsoft Academic Search

The oxamido-bridged heterobinuclear copper(II)–nickel(II) complex, [Cu(oxbe)Ni(phen)2]ClO4·3H2O (1) and homotrinuclear nickel(II) complex {[Ni(oxbe)]2Ni(H2O)2}·2.5DMF (2) have been synthesized and characterized by means of elemental analysis, IR, EPR, and electronic spectra and magnetic susceptibility, where H3oxbe is dissymmetrical ligand N-benzoato-N?-(2-aminoethyl)oxamido, phen=1,10-phenanthroline, DMF=dimethylformamide. Complex 1 has an extended oxamido-bridged structure consisting of planar copper(II) and octahedral nickel(II) ions. The ?M and ?eff versus T

Ruo-Jie Tao; Shuang-Quan Zang; Yan-Xiang Cheng; Qing-Lun Wang; Ning-Hai Hu; Jing-Yang Niu; Dai-Zheng Liao

2003-01-01

75

Oxo-bridged dinuclear chromium(III) complexes: correlation between the optical and magnetic properties and the basicity of the oxo bridge.  

PubMed

The synthesis and X-ray structure of a new member of the series of oxo-bridged, dinuclear chromium(III) complexes, the methyl isocyanide complex [(CH3NC)5CrOCr(CNCH3)5](PF6)4·2CH3CN, is reported. This constitutes only the third oxo-bridged, dinuclear chromium(III) complex with a homoleptic auxillay ligand sphere. Experimentally, the system shows unshifted narrow nuclear magnetic resonance (NMR) spectra that are consistent with calculations using broken symmetry density functional theory (DFT), which suggests it to be the strongest coupled, dinuclear chromium(III) complex known. Furthermore, we report the crystal structure and computed magnetic properties for [(bpy)2(SCN)CrOCr(NCS)(bpy)2](ClO4)2·2H2O (bpy = 2,2'-bipyridine), which differs from other reported oxo-bridged species by featuring a bent CrOCr(4+) core. We also interpret the spectacular 10-orders-of-magnitude variation in acid dissociation constant of the bridging hydroxo ligand in mono hydroxo-bridged dinuclear chromium(III) complexes, in terms of a valence bond model parametrized by metal-to-metal charge transfer (MMCT) and ligand-to-metal charge transfer (LMCT) energies. PMID:24597528

Morsing, Thorbjørn J; Bendix, Jesper; Weihe, Høgni; Døssing, Anders

2014-03-17

76

Magnetic properties of two 2D complexes based on 1D chain containing [Fe(bpy)(CN)4]- unit.  

PubMed

Two heterobimetallic 2-dimensional layer complexes, {[Fe(bpy)(CN)(4)](2)M(4,4'-bipyridine)}·4H(2)O [bpy = 2,2'-bipyridine, M = Mn (1), Cu (2)] have been prepared by diffusion and their structures determined by single crystal X-ray diffraction. 1 and 2 are isomorphous, made of neutral bimetallic [Fe(bpy)(CN)(4)](2)M(4,4'-bipyridine)] layers and uncoordinated water molecules located between the layers. Interestingly, complex 2 shows the compression of the Jahn-Teller distortion around the copper(II) ion. Magnetic investigation shows antiferromagnetic coupling between the manganese(II) and iron(III) ions mediated by bridging CN(-) in 1, while ferromagnetic coupling between the copper(II) and iron(III) ions is seen in 2. Both complexes 1 and 2 reveal a metamagnetic-like behaviour with different critical fields (H(c), at 1.8 K): 2.0 kOe (1) and 3.2 kOe (2). The weak interchain antiferromagnetic interaction can be illustrated by the spin-polarization mechanism. PMID:23131869

Song, Xiao-Jiao; Muddassir, Mohd; Chen, Ying; Wang, Hui-Sheng; Song, You; You, Xiao-Zeng

2013-01-28

77

Proton NMR spectroscopy and magnetic properties of a solution-stable dicopper(II) complex bearing a single mu-hydroxo bridge.  

PubMed

The reaction of copper(II) perchlorate with the macrocyclic ligand [22]py4pz in the presence of base leads to formation of a dinuclear complex [Cu(2)([22]py4pz)(mu-OH)](ClO(4))(3)xH(2)O, in which two copper ions are bridged by a single mu-hydroxo bridge. Each copper ion is further surrounded by four nitrogen atoms of the ligand. The mu-hydroxo bridge mediates a strong antiferromagnetic coupling (2J = -691(35) cm(-1)) between the metal centers, leading to relatively sharp and well-resolved resonances in the (1)H NMR spectrum of the complex in solution. We herein report the crystal structure, the magnetic properties, and the full assignment of the hyperfine-shifted resonances in the NMR spectrum of the complex, as well as the determination of the exchange coupling constant in solution through temperature-dependent NMR studies. PMID:15934768

Koval, Iryna A; van der Schilden, Karlijn; Schuitema, Anna Maria; Gamez, Patrick; Belle, Catherine; Pierre, Jean-Louis; Lüken, Matthias; Krebs, Bernt; Roubeau, Olivier; Reedijk, Jan

2005-06-13

78

Magnetic and optical properties of Cu(II)-bis(oxamato) complexes: combined quantum chemical density functional theory and vibrational spectroscopy studies.  

PubMed

Vibrational spectroscopies are shown to be highly sensitive to the structural modifications of paramagnetic mono- and trinuclear Cu(II)-bis(oxamato) complexes. The vibrational bands are assigned using density functional theory (DFT) calculations. Moreover, Raman spectroscopy investigations for different temperatures of thin films show that the onset of superexchange interactions at low temperatures does not involve a modification of the structural parameters. The influence of packing effects, however, on the magnetic properties is significant, as demonstrated by means of DFT using the broken symmetry approach. PMID:18410161

Bräuer, Björn; Weigend, Florian; Totti, Federico; Zahn, Dietrich R T; Rüffer, Tobias; Salvan, Georgeta

2008-05-01

79

Magnetic properties of a new N-TEMPO-tert-butyl substituted salicylaldimines and their biradical palladium(II) complexes  

NASA Astrophysics Data System (ADS)

A new TEMPO bearing tert-butylated salicylaldimines 1 and 2, as well as early reported 3, and their bis(N-TEMPO-tert-butylated salicylaldiminato)palladium(II) biradical complexes 4-6 have been synthesized and characterized by elemental analyses, IR, UV/vis, ESR and an SQUID magnetometer. The solid state g-factors (2.0116-2.0168) for 4-6 suggest the existence of the significant metal-orbital contribution to the SOMO of nitroxyl radicals. The ?mT vs. T plots for 1 and 2 indicate that the ?mT decreases as T is lowered from 300 to 20 K, suggesting the existence of weak antiferromagnetic interactions in these radicals. Variable-temperature dependence (10-300 K) magnetic susceptibility data for biradical complexes 4-6 revealed the existence of ferromagnetic and antiferromagnetic behavior around at 10-220 K range for 4. The 1/?m data for 1-6 follow the Curie-Weiss law with negative ? throughout the above temperature range.

Kasumov, Veli T.; Yerli, Yusuf; Topkaya, Ramazan

2013-01-01

80

Solution NMR characterization of magnetic/electronic properties of azide and cyanide-inhibited substrate complexes of human heme oxygenase: implications for steric ligand tilt.  

PubMed

Solution 2D (1)H NMR was carried out on the azide-ligated substrate complex of human heme oxygenase, hHO, to provide information on the active site molecular structure, chromophore electronic/magnetic properties, and the distal H-bond network linked to the exogenous ligand by catalytically relevant oriented water molecules. While 2D NMR exhibited very similar patterns of two-dimensional nuclear Overhauser spectroscopy cross peaks of residues with substrate and among residues as the previously characterized cyanide complex, significant, broadly distributed chemical shift differences were observed for both labile and non-labile protons. The anisotropy and orientation of the paramagnetic susceptibility tensor, ?, were determined for both the azide and cyanide complexes. The most significant difference observed is the tilt of the major magnetic axes from the heme normal, which is only half as large for the azide than cyanide ligand, with each ligand tilted toward the catalytically cleaved ?-meso position. The difference in chemical shifts is quantitatively correlated with differences in dipolar shifts in the respective complexes for all but the distal helix. The necessity of considering dipolar shifts, and hence determination of the orientation/anisotropy of ?, in comparing chemical shifts involving paramagnetic complexes, is emphasized. The analysis shows that the H-bond network cannot detect significant differences in H-bond acceptor properties of cyanide versus azide ligands. Lastly, significant retardation of distal helix labile proton exchange upon replacing cyanide with azide indicates that the dynamic stability of the distal helix is increased upon decreasing the steric interaction of the ligand with the distal helix. PMID:23391487

Peng, Dungeng; Ogura, Hiroshi; Ma, Li-Hua; Evans, John P; de Montellano, Paul R Ortiz; La Mar, Gerd N

2013-04-01

81

Closely-related Zn(II)2Ln(III)2 complexes (Ln(III) = Gd, Yb) with either magnetic refrigerant or luminescent single-molecule magnet properties.  

PubMed

The reaction of the compartmental ligand N,N',N?-trimethyl-N,N?-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H2L) with Zn(NO3)2·6H2O and subsequently with Ln(NO3)3·5H2O (Ln(III) = Gd and Yb) and triethylamine in MeOH using a 1:1:1:1 molar ratio leads to the formation of the tetranuclear complexes {(?3-CO3)2[Zn(?-L)Gd(NO3)]2}·4CH3OH (1) and{(?3-CO3)2[Zn(?-L)Yb(H2O)]2}(NO3)2·4CH3OH (2). When the reaction was performed in the absence of triethylamine, the dinuclear compound [Zn(?-L)(?-NO3)Yb(NO3)2] (3) is obtained. The structures of 1 and 2 consist of two diphenoxo-bridged Zn(II)-Ln(III) units connected by two carbonate bridging ligands. Within the dinuclear units, Zn(II) and Ln(III) ions occupy the N3O2 inner and the O4 outer sites of the compartmental ligand, respectively. The remaining positions on the Ln(III) ions are occupied by oxygen atoms belonging to the carbonate bridging groups, by a bidentate nitrate ion in 1, and by a coordinated water molecule in 2, leading to rather asymmetric GdO9 and trigonal dodecahedron YbO8 coordination spheres, respectively. Complex 3 is made of acetate-diphenoxo triply bridged Zn(II)Yb(III) dinuclear units, where the Yb(III) exhibits a YbO9 coordination environment. Variable-temperature magnetization measurements and heat capacity data demonstrate that 1 has a significant magneto-caloric effect, with a maximum value of -?Sm = 18.5 J kg(-1) K(-1) at T = 1.9 K and B = 7 T. Complexes 2 and 3 show slow relaxation of the magnetization and single-molecule magnet (SMM) behavior under an applied direct-current field of 1000 Oe. The fit of the high-temperature data to the Arrhenius equation affords an effective energy barrier for the reversal of the magnetization of 19.4(7) K with ?o = 3.1 × 10(-6) s and 27.0(9) K with ?o = 8.8 × 10(-7) s for 2 and 3, respectively. However, the fit of the full range of temperature data indicates that the relaxation process could take place through a Raman-like process rather than through an activated Orbach process. The chromophoric L(2-) ligand is able to act as an "antenna" group, sensitizing the near-infrared (NIR) Yb(III)-based luminescence in complexes 2 and 3 through an intramolecular energy transfer to the excited states of the accepting Yb(III) ion. These complexes show several bands in the 945-1050 nm region, corresponding to (2)F5/2?(2)F7/2 transitions arising from the ligand field splitting of both multiplets. The observed luminescence lifetimes ?obs are 0.515 and 10 ?s for 2 and 3, respectively. The shorter lifetime for 2 is due to the presence of one coordinated water molecule on the Yb(III) center (and to a lesser extent noncoordinated water molecules), facilitating vibrational quenching via O-H oscillators. Therefore, complexes 2 and 3, combining field-induced SMM behavior and NIR luminescence, can be considered to be dual magneto-luminescent materials. PMID:24593019

Ruiz, José; Lorusso, Giulia; Evangelisti, Marco; Brechin, Euan K; Pope, Simon J A; Colacio, Enrique

2014-04-01

82

Synthesis, structures, and magnetic properties of a series of cyano-bridged Fe-Mn bimetallic complexes.  

PubMed

The preparation and crystal structures of five cyano-bridged Fe-Mn complexes, [(bipy)2Fe(II)(CN)2Mn(II)(bipy)2]2(ClO4)4 (1), [(bipy)2Fe(II)(CN)2Mn(II)(DMF)3(H2O)]2(ClO4)4 (2), {[(Tp)Fe(III)(CN)3]2Mn(II)(DMF)2(H2O)}2 (3), {[(Tp)Fe(III)(CN)3]2Mn(II)(DMF)2}n (4), and Na2[Mn(II)Fe(II)(CN)6] (5) (bipy = 2,2'-bipyridine, Tp = tris(pyrazolyl)hydroborate), are reported here. Compounds 1-4 contain the basic Fe2(CN)4Mn2 square building units, of which 1-3 show the motif of discrete molecular squares of Fe2(CN)4Mn2 and 4 possesses a 1D double-zigzag chain-like structure, while compound 5 is a 3D cubic framework analogous to that of Prussian blue. Compounds 1 and 2 show weak ferromagnetic interactions between two Mn(II) ions through the bent -NC-Fe(II)-CN- bridges. Compound 3 shows weak antiferromagnetic coupling between the Fe(III) and Mn(II) ions, while compound 4 displays a metamagnetic-like behavior with TN = 5.2 K and Hc = 10.5 kOe. Compound 5 exhibits a ferromagnetic ordering with Tc= 3.5 K, coercive field, Hc, = 330 G, and a remnant magnetization of 503 cm3 Oe mol(-1). PMID:16780323

Jiang, Long; Feng, Xiao-Long; Lu, Tong-Bu; Gao, Song

2006-06-26

83

Three tetranuclear copper(II) cluster-based complexes constructed from 4-amino-1,2,4-triazole and different aromatic carboxylates: Assembly, structures, electrochemical and magnetic properties  

SciTech Connect

Three new tetranuclear copper(II) cluster-based complexes constructed from 4-amino-1,2,4-triazole (atrz) and three types of aromatic carboxylates, [Cu{sub 4}({mu}{sub 3}-OH){sub 2}(atrz){sub 2}(DNBA){sub 6}] (1), [Cu{sub 4}({mu}{sub 3}-OH){sub 2}(atrz){sub 2}(1,3-BDC){sub 3}]{center_dot}2H{sub 2}O (2) and [Cu{sub 4}({mu}{sub 3}-OH){sub 2}(atrz){sub 2}(SIP){sub 2}]{center_dot}4H{sub 2}O (3) (HDNBA=3,5-dinitrobenzoic acid, 1,3-H{sub 2}BDC=1,3-benzenedicarboxylic acid and NaH{sub 2}SIP=sodium 5-sulfoisophthalate), have been hydrothermally synthesized and structurally characterized. Complex 1 displays a single-molecular Cu{sup II}{sub 4} cluster structure, which is further connected by the intermolecular hydrogen-bonding interactions to form a 2D supramolecular layer. In 2, there also exist tetranuclear Cu{sup II}{sub 4} clusters, which are linked by the 1,3-BDC anions to give a 3D NaCl-type framework. In 3, the Cu{sup II}{sub 4} clusters are connected by the carboxyl and sulfo groups of SIP anions to generate 3D (4,8)-connected framework with a (4{sup 10}{center_dot}6{sup 14}{center_dot}8{sup 4})(4{sup 5}{center_dot}6){sub 2} topology. The atrz ligand conduces to the construction of tetranuclear copper(II) clusters and the carboxylates with different non-carboxyl substituent show important effects on the final structures of the title complexes. The electrochemical and magnetic properties of 1-3 have been investigated. - Graphical abstract: Three tetranuclear copper(II) cluster-based complexes based on different carboxylates have been synthesized under hydrothermal conditions. The carboxylate anions play a key role in the formation of three different structures. Highlights: Black-Right-Pointing-Pointer Three new tetranuclear copper(II) cluster-based complexes have been obtained. Black-Right-Pointing-Pointer The atrz conduces to the construction of tetranuclear copper(II) clusters. Black-Right-Pointing-Pointer Carboxylates show important effect on the structures of title complexes. Black-Right-Pointing-Pointer Magnetic properties and electrochemical behaviors have been reported.

Wang, Xiu-Li, E-mail: wangxiuli@bhu.edu.cn [Department of Chemistry, Bohai University, Liaoning Province Silicon Materials Engineering Technology Research Centre, Jinzhou 121000 (China)] [Department of Chemistry, Bohai University, Liaoning Province Silicon Materials Engineering Technology Research Centre, Jinzhou 121000 (China); Zhao, Wei; Zhang, Ju-Wen; Lu, Qi-Lin [Department of Chemistry, Bohai University, Liaoning Province Silicon Materials Engineering Technology Research Centre, Jinzhou 121000 (China)] [Department of Chemistry, Bohai University, Liaoning Province Silicon Materials Engineering Technology Research Centre, Jinzhou 121000 (China)

2013-02-15

84

Structure and magnetic properties of a copper(II) complex with the schiff base derived from 2,2,6,6-tetramethyl-4-aminopiperidine-1-iminoxyl  

Microsoft Academic Search

The crystal structure of a copper(II) complex with a Schiff base containing iminoxyI radicals has been determined. Measurements of magnetic susceptibility in the 1.3-300~ range have shown that the magnetic system of the complex consists of triads of interacting spins. The ESR spectra of single crystals of the complex measured at 1.3-300~ have led to a conclusion about interaction between

L. O. Atovmyan; N. I. Golovina; G. A. Klitskaya; A. A. Medzhidov; A. V. Zvarykina; V. B. Stryukov; D. N. Fedutin

1975-01-01

85

Structural, electronic and magnetic properties of Mo (4d)-based complex perovskites Ba2MMoO6 (M=Cr and Fe)  

NASA Astrophysics Data System (ADS)

We report a study of crystallographic parameters of the Mo-based complex perovskites Ba2MMoO6 (M=Cr and Fe) obtained from analysis of X-ray diffraction (XRD) data and the electronic and magnetic properties prediction using the magnetic measurements and the full-potential linearized muffin–tin orbitals within the plane-wave approximation (LMTO–PLW). The Ba2MMoO6 materials were prepared by the solid state reaction method. XRD analysis reveals that Ba2MMoO6 crystalline in a cubic structure (space group Fm-3m) with lattice parameters (a=8.013 Å) for M=Cr and (a=8.061 Å) for M=Fe. XRD results present a matching of 98% with the theoretical results. The densities of states were calculated using the local spin density approximation (LSDA) and LSDA+U methods. LDOS results show a half-metallic-ferrimagnetic ground state for Ba2MMoO6, which is in majority due to the 4d-t2g and 3d-t2g characters. The structural, electronic and magnetic calculation results are in excellent agreement with the experimental and previous theoretical results.

Musa Saad H.-E., M.; El-Hagary, M.

2014-06-01

86

Complex magnetic properties of the rare-earth copper oxides, R2CuO4, observed via measurements of the dc and ac magnetization, EPR, microwave magnetoabsorption, and specific heat  

NASA Astrophysics Data System (ADS)

We report the results of an extensive investigation of the magnetic properties of a large series of undoped R2CuO4 single crystals with R==Pr, Nd, Sm, Eu, and Gd (which are the host compounds for the newly discovered series of electron cuprate superconductors) and mixture versions of the form A2-xBxCuO4, with A==Pr, Nd, Sm, Eu, or Gd, and B==Gd, Tb, or Dy. We have measured dc and ac magnetization, microwave magnetoabsorption, EPR, and specific heat. These measurements reveal two characteristic transition temperatures associated with a novel complex magnetic behavior, including weak ferromagnetism, two sharp peaks in the low-field dc magnetization, an unusual anisotropy in the EPR resonance field for R=Gd, and two additional anisotropic microwave absorption modes. The higher characteristic transition temeperature at ~270 K is associated with antiferromagnetic ordering of the Cu moments which are strongly coupled within the CuO2 layers. The lower, at <=20 K, cannot be attributed to antiferromagnetic ordering of the R moments and is tentatively attributed to a spontaneous canted spin reorientation. An understanding of this magnetic behavior is important in order to ascertain its relationship to possible mechanisms of high-temperature superconductivity.

Oseroff, S. B.; Rao, D.; Wright, F.; Vier, D. C.; Schultz, S.; Thompson, J. D.; Fisk, Z.; Cheong, S.-W.; Hundley, M. F.; Tovar, M.

1990-02-01

87

Three tetranuclear copper(II) cluster-based complexes constructed from 4-amino-1,2,4-triazole and different aromatic carboxylates: Assembly, structures, electrochemical and magnetic properties  

NASA Astrophysics Data System (ADS)

Three new tetranuclear copper(II) cluster-based complexes constructed from 4-amino-1,2,4-triazole (atrz) and three types of aromatic carboxylates, [Cu4(?3-OH)2(atrz)2(DNBA)6] (1), [Cu4(?3-OH)2(atrz)2(1,3-BDC)3]·2H2O (2) and [Cu4(?3-OH)2(atrz)2(SIP)2]·4H2O (3) (HDNBA=3,5-dinitrobenzoic acid, 1,3-H2BDC=1,3-benzenedicarboxylic acid and NaH2SIP=sodium 5-sulfoisophthalate), have been hydrothermally synthesized and structurally characterized. Complex 1 displays a single-molecular CuII4 cluster structure, which is further connected by the intermolecular hydrogen-bonding interactions to form a 2D supramolecular layer. In 2, there also exist tetranuclear CuII4 clusters, which are linked by the 1,3-BDC anions to give a 3D NaCl-type framework. In 3, the CuII4 clusters are connected by the carboxyl and sulfo groups of SIP anions to generate 3D (4,8)-connected framework with a (410·614·84)(45·6)2 topology. The atrz ligand conduces to the construction of tetranuclear copper(II) clusters and the carboxylates with different non-carboxyl substituent show important effects on the final structures of the title complexes. The electrochemical and magnetic properties of 1-3 have been investigated.

Wang, Xiu-Li; Zhao, Wei; Zhang, Ju-Wen; Lu, Qi-Lin

2013-02-01

88

Tridecanuclear [Mn(III)5Ln(III)8] complexes derived from N-(t)butyl-diethanolamine: synthesis, structures, and magnetic properties.  

PubMed

The synthesis, structures and magnetic properties of a family of heterometallic [Mn(III)(5)Ln(III)(8)(mu(3)-OH)(12)(L(2))(4)(piv)(12)(NO(3))(4)(OAc)(4)](-) (Ln = Pr, 2; Nd, 3; Sm, 4; Gd, 5; Tb, 6) aggregates are reported. The complexes were obtained from the direct reaction of N-(t)butyldiethanolamine (H(2)L(2)) with Mn(OAc)(2) x 4 H(2)O and Ln(NO(3))(3) x 6 H(2)O in the presence of pivalic acid (pivH) in MeCN under ambient conditions. Compounds 2-6 are isomorphous and crystallize in the monoclinic space group P2(1)/n with four molecules in the unit cell. The complexes have a centrosymmetric tridecanuclear anionic core consisting of two distorted inner heterometallic [Mn(III)Ln(III)(3)(mu(3)-OH)(4)](8+) cubane subunits sharing a common Mn vertex flanked by four edge-sharing heterometallic [Mn(III)Ln(III)(2)(mu(3)-OH)(4)](5+) defect cubane units. Complexes 2-6 are the first high-nuclearity 3d-4f aggregates reported to date using (t)Bu-deaH(2) as ligand. These compounds show no evidence of slow relaxation behavior above 1.8 K, which appears to be the consequence of the very weak or non-existent magnetic interactions between the Mn(III) and Ln(III) ions resulting from the particular angles at the bridging oxygens. PMID:19530694

Ako, Ayuk M; Mereacre, Valeriu; Clérac, Rodolphe; Hewitt, Ian J; Lan, Yanhua; Buth, Gernot; Anson, Christopher E; Powell, Annie K

2009-07-20

89

Synthesis, structural characterization, and magnetic properties of a copper-gadolinium complex derived from a hydroxybenzohydrazide ligand.  

PubMed

The reaction of hydroxybenzohydrazide with o-vanillin yields 2-hydroxy-N'-[(2-hydroxy-3-methoxyphenyl)methylidene]benzohydrazide (LH3), a ligand that is able to give mononuclear and tetranuclear copper complexes but also to associate copper and gadolinium ions in a Cu2-Gd2 heterotetranuclear complex. This synthesis is successful if the Gd ions, which are acidic in protic solvents, are introduced in a basic methanol solution of the mononuclear copper complex. In the absence of piperidine, the addition of Gd ions to a methanol solution of the mononuclear copper complex only yields a tetranuclear cubane-type copper complex. This work reports on the first structural characterization of a copper-gadolinium complex involving a benzohydrazide ligand. The resulting complex consists of two Cu-Gd pairs linked by a dihydroxo Gd-Gd bridge, in which the Cu and Gd ions are bridged by a nonsymmetric phenoxo-hydroxo bridge. The magnetostructural correlation between the ferromagnetic coupling constant and the hinge angle observed in symmetrical double-phenoxo Cu-Gd bridges remains valid for dissymmetric Cu-Gd bridges and confirms the preponderance of the structural factor over the nature of the bridge. This tetranuclear complex corresponds to two S = 4 units linked through a dihydroxo bridge introducing a weak antiferromagnetic Gd-Gd interaction and impeding the existence of a S = 8 ground state. PMID:24499105

Costes, Jean-Pierre; Duhayon, Carine; Vendier, Laure

2014-02-17

90

Synthesis, crystal structures and magnetic properties of transition metal–azide complexes coordinated with pyridyl nitronyl nitroxides  

Microsoft Academic Search

Two novel complexes Co(N3)2(PNN)4 (I) and Mn(N3)2(PNN)2(CH3OH)(C2H5OH) (II) (PNN=2-(p-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3–oxide) were synthesized and characterized by infrared spectra, elemental analyses and UV–Vis techniques. The crystal structures of both complexes have been determined by X-ray diffraction analysis. Complex I is a neutral five-spin system and adopts a centrosymmetric tetragonally compressed octahedral coordination geometry in which Co(II) ion is coordinated to four radicals through

Lei Zhang; Li-Cun Li; Dai-Zheng Liao; Zong-Hui Jiang; Shi-Ping Yan; Pan-Wen Shen

2001-01-01

91

Magnetic properties of iron nanoparticle  

SciTech Connect

Magnetic properties of Fe nanoparticles with different sizes synthesized by a physical deposition technique have been investigated experimentally. We have used a high pressure sputtering technique to deposit iron nanoparticles on a silicon substrate. The nanoparticles are then analyzed using atomic force microscopy (AFM), transmission electron microscopy (TEM), and superconducting quantum interference device techniques. TEM and AFM data show that the particle size could be tuned by adjusting the deposition conditions. The magnetic properties have been investigated from temperature dependent magnetization M(T) and field dependent magnetization M(H) measurements. The results show that two phases including both ferromagnetic and superparamagnetic particles are present in our system. From these data we extracted the superparamagnetic critical size to be 9 nm for our samples. Ferromagnetic particles are single magnetic domain particles and the magnetic properties can be explained by the Stoner and Wohlfarth model. For the superparamagnetic phase, the effective anisotropy constant, K{sub eff}, decreases as the particle size increases.

Carvell, J.; Ayieta, E.; Gavrin, A.; Cheng, Ruihua [Department of Physics, Indiana University Purdue University Indianapolis, 402 N Blackford Street Indianapolis, Indiana 46202 (United States); Shah, V. R.; Sokol, P. [Department of Physics, Indiana University, 727 E. Third Street Bloomington, Indiana 47405 (United States)

2010-05-15

92

Mononuclear and binuclear iron(III) complexes incorporating N 4O 3 coordinating heptadentate ligand: Synthesis, structure and magnetic properties  

Microsoft Academic Search

The N4O3 coordinating heptadentate ligand afforded the mononuclear [FeIII(HL)][BPh4] (1) and binuclear [Fe2IIIL(OAc)2][BPh4] (2) complexes. In complex 1, the ligand binds in a trianionic N2O3 fashion whereas in the case of 2 the ligand binds in the trianionic N4O3 form in which the iron ions are held together by ?-phenoxo and bis ?-acetato bridges. In 1, the Fe(III) center has

Reena Singh; Coen de Graaf; Enrique Colacio; Kajal Krishna Rajak

2008-01-01

93

Mono-, di- and trinuclear 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz)-containing copper(II) complexes: syntheses, crystal structures and magnetic properties.  

PubMed

Three new copper(ii) complexes of formula [Cu(tppz)(NCO)(2)].0.4H(2)O (1), [Cu(2)(tppz)Br(4)](2) and [Cu(3)(tppz)(C(5)O(5))(3)(H(2)O)(3)].7H(2)O (3)[tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine; C(5)O(5)(2-) = croconate, dianion of 4,5-dihydroxycyclopent-4-ene-1,2,3-trione] have been synthesised and structurally characterized by X-ray diffraction methods. The structure of complex is made up of neutral [Cu(tppz)(NCO)(2)] mononuclear units and uncoordinated water molecules. The mononuclear units are grouped by pairs to give a rather short copper-copper distance of 3.9244(4) angstroms. The structure of complex 1 consists of neutral tppz-bridged [Cu(2)(tppz)Br(4)] dinuclear units, the copper-copper separation across tppz being 6.6198(1) angstroms. The dinuclear units are further connected through weak, double out-of-plane Cu-Br...Cu bridges [Br(1)...Cu(1a) 4.0028(17) angstroms] creating tetranuclear entities, the copper-copper separation through this interaction being 4.3299(21) angstroms. The structure of complex 3 is built of neutral [Cu(3)(tppz)(C(5)O(5))(3)(H(2)O)(3)] trinuclear units and uncoordinated water molecules. Tppz and one of the croconate groups act as bridging ligands, the former exhibiting the bis-terdentate coordination mode and the latter adopting an unusual asymmetrical bis-bidentate bridging mode through three adjacent oxygen atoms. The other two croconate groups exhibit the bidentate coordination mode. The intramolecular copper-copper separations are 6.5417(9)(across tppz) and 4.3234(9) angstroms (through bis-bidentate croconato). The magnetic properties of 2 and 3 have been investigated in the temperature range 1.9-300 K. The magnetic behaviour of complex 2 is that of an antiferromagnetically coupled copper(II) dimer (J = -40.9 cm(-1), the Hamiltonian being H = -JS(A).S(B)). In the case of compound , the chi(M) T vs. T plot is typical of an overall antiferromagnetic coupling with a low-lying spin doublet being fully populated at T < 10 K. The values of the intramolecular antiferromagnetic interactions in 3 are -19.9 (across tppz) and -32.9 cm(-1)(through bridging croconato). Density functional type calculations were performed on model dinuclear fragments of 3 in order to analyze the efficiency of the exchange pathways involved and also to substantiate the coupling parameters. PMID:15558125

Carranza, José; Sletten, Jorunn; Brennan, Conor; Lloret, Francesc; Cano, Joan; Julve, Miguel

2004-12-01

94

Chain-like and dinuclear coordination polymers in lanthanide (Nd, Eu) oxochloride complexes with 2,2':6',2''-terpyridine: synthesis, XRD structure and magnetic properties.  

PubMed

The solvothermal reactions (at 180 °C for 48 h) of a mixture of lanthanide chlorides (Nd, Eu) with the tridendate heterocyclic nitrogen ligand, 2,2':6',2''-terpyridine (terpy), in ethanol medium give rise to the formation of crystalline mixed chloro-hydroxo-aquo complex Ln(2)Cl(5)(OH)(H(2)O)(terpy). Its crystal structure consists of the connection of eight- and nine-fold coordinated lanthanide centers linked to each other via ?(2,3)-chloro and ?(3)-hydroxo species to form a tetranuclear unit, which are then further connected through chloro edges to generate infinite ribbons. Only one lanthanide cation in every two is chelated by terpy. Similar molar composition of the starting reactants led to the crystallization at room temperature of a second type of complex LnCl(3)(H(2)O)(terpy) (Ln = Nd, Eu). It is built up from the molecular assembly of dinuclear species containing two eight-fold coordinated lanthanide centers chelated by terpy and linked through a ?(2)-Cl edge. Luminescence spectra have been collected for the europium-based compound and indicates a strong red signal with the expected bands from the F-D transitions. The magnetic properties of the four compounds were investigated. Their behaviors correspond to that of the rare-earth ions present in the structure. The magnetic susceptibility of the neodymium-based compounds agrees with that of the Nd(III) ion with an (4)I(9/2) ground state split by crystal field. Concerning the Eu(III) derivatives, the term (7)F is split by spin-orbit coupling, the first excited states being thermally populated. Accordingly, the thermal dependence of the magnetic susceptibility was nicely reproduced by using appropriate analytical relations. The refined values of the spin-orbit coupling are consistent with the energies of the electronic levels deduced from the photoluminescence spectra. Unexpectedly, the magnetic susceptibility exhibits a hysteretic behavior in the range 45-75 K. PMID:21818485

Lhoste, Jérôme; Pérez-Campos, Ana; Henry, Natacha; Loiseau, Thierry; Rabu, Pierre; Abraham, Francis

2011-09-28

95

Synthesis, structure, and single-molecule magnetic properties of rare-earth sandwich complexes with mixed phthalocyanine and Schiff base ligands.  

PubMed

Double- and quadruple-decker complexes of rare-earth metals with mixed phthalocyanine and Schiff base ligands have been synthesized and structurally and magnetically characterized. These complexes (see picture: Dy?pink, Ca?green, N?blue, C?black) extend the scope of sandwich-type tetrapyrrole-based rare-earth molecular materials. PMID:23281042

Wang, Hailong; Cao, Wei; Liu, Tao; Duan, Chunying; Jiang, Jianzhuang

2013-02-11

96

An antiferromagnetically coupled hexanuclear copper(II) Schiff base complex containing phenoxo and dicyanamido bridges: Structural aspects and magnetic properties  

Microsoft Academic Search

A novel hexanuclear complex [{(CuL)2Cu}2(?-dca)2](ClO4)2·2L?(1) (where H2L=(OH)C6H4C(CH3)N(CH2)3NC(CH3)C6H4(OH) or N,N?-bis(2-hydroxyacetophenone) propylenediimine and dca=N(CN)2? and L?=2-hydroxyacetophenone) has been synthesized and characterized by elemental analysis, UV–Vis, FT-IR spectroscopic and electrochemical methods. Single crystal X-ray structural characterization reveals a centrosymmetric nature of the complex unit, where the metal centers adopt distorted square-planar and distorted octahedral geometries. Structural analysis also reveals ?2-phenoxo bridges between terminal

Pritha Talukder; Shyamapada Shit; Ashok Sasmal; Stuart R. Batten; Boujemaa Moubaraki; Keith S. Murray; Samiran Mitra

2011-01-01

97

Novel heterometallic metal-azido complex synthesized by "one-step" reaction: synthetic strategy and magnetic properties  

NASA Astrophysics Data System (ADS)

A novel heterometallic complex, [Ni2Mn(N3)2(nic)4·(H2O)2]n (1) (nic=nicotinate), was obtained by assembling MnCl2·4H2O, Ni(NO3)2·6H2O, NaN3 and nicotinic acid with a "one step" synthetic strategy—hydrothermal reaction. The 3D structure of the complex can be described as end-on (EO) azido and syn,syn carboxylates mixed bridged by alternate Ni-Mn-Ni trimers linked by the nicotinate. Dominant ferromagnetic interactions were observed between the NiII and MnII ions in the trimer.

Jiao, Yong-Kun; Li, Xiu-Ping; Zhao, Cui; Wang, Hai-Chao; Xue, Min; Zhao, Jiong-Peng; Liu, Fu-Chen

2013-06-01

98

Complex magnetic reversal modes in low-symmetry nanoparticles  

NASA Astrophysics Data System (ADS)

A detailed numerical analysis of the magnetization reversal processes in T-shaped nanoparticles has been carried out. Attention has been focused on the influence of the symmetry of the particle on the formation, propagation, and interaction of internal magnetic structures such as domain walls, vortices, and antivortices. Results show that the lower the degree of symmetry of the particle, the more complex the reversal process is. Thus, symmetry represents an additional ingredient to control the magnetic properties of ferromagnetic nanoparticles.

Escobar, R. A.; Vargas, N. M.; Castillo-Sepúlveda, S.; Allende, S.; Altbir, D.; d'Albuquerque e Castro, J.

2014-03-01

99

Synthesis, crystal structure and magnetic properties of a nickel(II) complex with pyridine-substituted nitronyl nitroxide radicals  

Microsoft Academic Search

The complex [Ni(NIT2Py)(PDA)(H2O)]·(MeOH)(H2O) [NIT2Py = 2-(2'-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; PDA = 2,6-pyridine dicarboxylic acid] has been prepared and structurally characterized. The NiII ion is in a distorted octahedral environment: one nitrogen atom and one oxygen atom from the NIT2Py, one nitrogen atom from the PDA and one oxygen atom from the H2O in the basal plane; two oxygen atoms from the PDA in

Chen-Xi Zhang; Dai-Zheng Liao; Zong-Hui Jiang; Shi-Ping Yan; Bin Zhao

2003-01-01

100

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.

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

2013-01-01

101

Three Novel Rare-earth Complexes with Nitronyl Nitroxide Radical [RE(hfac) 3 (NITPhOCH 3 ) 2 ] [RE = Gd III , Y III and Er III ]: Syntheses, Crystal Structures and Magnetic Properties  

Microsoft Academic Search

Three novel isomorphous complexes of formula [RE(hfac)3(NITPhOCH3)2], where RE = GdIII, YIII and ErIII; hfac = hexafluoroacetylacetonate; NITPhOCH3 = 4?-methoxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, were synthesized, structurally and magnetically characterized.\\u000a The crystal structure consists of isolated molecules where the nitronyl nitroxide radicals act as monodentate ligands towards\\u000a RE(III) through the oxygen atom of the N–O group. The magnetic properties of the complexes were studied

Qi-Hua Zhao; Yong-Ping Ma; Lin Du; Rui-Bin Fang

2006-01-01

102

Synthesis, crystal structure and magnetic properties of a novel complex Ni(NIT2-thz) 3(ClO 4) 2  

Microsoft Academic Search

A novel Ni(II)-nitronyl nitroxide-substituted thiazole complex, Ni(NIT2-thz)3(ClO4)2 (NIT2-thz=2-(2?-thiazole)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) was synthesized and characterized structurally and magnetically. It crystallizes in the monoclinic space group P21c. The metal coordination sphere is fully occupied by three chelating nitroxide ligands, showing a distorted octahedral geometry. The complex molecules were connected as 1-D chain structure by the intermolecular interaction. Magnetic studies show that antiferromagnetic couplings occurred

Li-Ya Wang; Lu-Fang Ma; Zong-Hui Jiang; Dai-Zheng Liao; Shi-Ping Yan

2005-01-01

103

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

104

Magnetic properties of magnetic nanowire arrays  

Microsoft Academic Search

The arrays of NiFe and CoNiFe nanowires were grown in anodic alumina (alumite) and track etched polycarbonate (PCTE) membranes with various pore sizes by pulsed electrodeposition. Magnetic properties of the array were studied as functions of wire material, length, and diameter as well as field orientation. In PCTE membranes, as high as 0.92 of remanent squareness (S) was obtained for

G. C. Han; B. Y. Zong; Y. H. Wu

2002-01-01

105

3D vector magnetic properties of soft magnetic composite material  

Microsoft Academic Search

Even under one-dimensional (1D) alternating or 2D rotating magnetic excitation, a magnetic material shows 3D magnetic property due to the rotation of magnetic domains. Only when the 3D properties are properly considered the understanding and modelling of the magnetisation process can be complete. This paper summarises our work about the investigation on the magnetic properties of soft magnetic composite (SMC)

Y. G. Guo; J. G. Zhu; Z. W. Lin; J. J. Zhong

2006-01-01

106

Scaling Properties of Magnetic Reconnection  

NASA Astrophysics Data System (ADS)

Magnetic reconnection is a universal process in space plasmas which often dominates the magnetic topology of the system and the flow patterns within and around it This process is operative in systems with vastly different spatial scales such as the Sun planetary magnetospheres and at comets In addition magnetic reconnection operates on plasma scales ranging from those associated with kinetic electrons and ions to fluid and macro-scales A true knowledge of the magnetic reconnection process requires the understanding of the minimum spatial scales at which it can be operative and how its properties scale with the system size Without such an understanding it is not possible to apply our knowledge of reconnection to systems with various sizes and properties In this talk we examine the scaling properties of reconnection using results of global hybrid simulations kinetic ions fluid electrons of solar wind interaction with magnetic dipoles of various strength Focus is on dayside reconnection during purely southward interplanetary magnetic field direction The parameter Dp defined as the standoff distance of the nose magnetopause normalized to solar wind ion skin depth is used to characterize the nature of the resulting magnetosphere as a function of dipole strength It is found that magnetic reconnection generation of reconnection electric field and the associated plasma jetting first occur at small values of Dp sim 2 before a terrestrial like magnetosphere is formed Further evolution of this process is observed with increasing values of

Omidi, N.; Blanco-Cano, X.; Russell, C. T.

107

Systematic studies of the structures and magnetic properties for a family of cubane complexes with the formula: [M2Ln2] (Ln = Dy, Gd; M = Ni, Zn) and [Ni2Y2].  

PubMed

Studies of magnetic properties of a family of tetranuclear M(II)(2)Ln(III)(2) (M = Ni, Zn; Ln = Dy, Gd and Y) complexes with hmp (anion of 2-hydroxymethylpyridine) and benzoate as ligands are reported. In these complexes, metal ions (M or Ln) occupy the four alternative corners of a distorted cubane with oxygen atoms from alkoxyl groups on the others. Complexes 1, 2 and 3 crystallized in P2(1)/c and complexes 4 and 5 in C2/c space groups. Although in different space groups, complexes 1-5 have very similar structures which permit the magnetic interactions to be systematically compared with respect to metal ion pairs. In complex 3 (Ni(2)Y(2)), clear ferromagnetic coupling between Ni(II) ions can be seen, with: g = 2.16, S = 2, D = -0.95 cm(-1), J = +3.77 cm(-1) (or g = 2.20, S = 2, D = +1.51 cm(-1)). In complex 5 (Zn(2)Gd(2)), a very weak antiferromagnetic coupling between the Gd(III) ions was observed: g = 2.08, J = -0.05 cm(-1). Based on these data, we concluded that the decrease in ?(M)T-T upon cooling for complex 2 (Zn(2)Dy(2)) might be partly due to antiferromagnetic coupling between Dy(III) ions. The data from complex 4 (Ni(2)Gd(2)) were analyzed based on the preceding results and gave moderate ferromagnetic coupling between Ni(II) and Gd(III) with J = 0.26 cm(-1). A detailed study of magnetic properties of complex 1 (Ni(2)Dy(2)) was not possible, because of its strong orbital contributions from Dy(III) ions. In addition, frequency-dependent out-of-phase signals were clearly observed for both complexes 1 and 2 which can be attributed to magnetoanisotropy contributions from Dy(III) ions. PMID:23334432

Yu, Wan-Rong; Lee, Gene-Hsian; Yang, En-Che

2013-03-21

108

3D vector magnetic properties of soft magnetic composite material  

NASA Astrophysics Data System (ADS)

Even under one-dimensional (1D) alternating or 2D rotating magnetic excitation, a magnetic material shows 3D magnetic property due to the rotation of magnetic domains. Only when the 3D properties are properly considered the understanding and modelling of the magnetisation process can be complete. This paper summarises our work about the investigation on the magnetic properties of soft magnetic composite (SMC) material under 3D vector magnetisations by using a 3D magnetic property tester. The core loss models under 3D flux density vectors are analysed and applied to predict the core losses of a permanent magnet claw pole/transverse flux motor with SMC core.

Guo, Y. G.; Zhu, J. G.; Lin, Z. W.; Zhong, J. J.

2006-07-01

109

Formation of octapod MnO nanoparticles with enhanced magnetic properties through kinetically-controlled thermal decomposition of polynuclear manganese complexes.  

PubMed

Polynuclear manganese complexes are used as precursors for the synthesis of manganese oxide nanoparticles (MnO NPs). Altering the thermal decomposition conditions can shift the nanoparticle product from spherical, thermodynamically-driven NPs to unusual, kinetically-controlled octapod structures. The resulting increased surface area profoundly alters the NP's surface-dependent magnetism and may have applications in nanomedicine. PMID:24220037

Douglas, Fraser J; MacLaren, Donald A; Tuna, Floriana; Holmes, William M; Berry, Catherine C; Murrie, Mark

2014-01-01

110

Synthesis, structure, electronic and magnetic properties of two new complexes obtained by coordination of Co(II) and Mn(II) phenyltrifluoroacetylacetonate with a nitronyl nitroxide radical  

Microsoft Academic Search

Two new magnetic compounds were obtained by using ?-diketonate 1,3-butanedione, 4,4,4-trifluoro-1-phenyl (Phtfac) as ligand. The complexes with formula [M(Phtfac)2(NITpPy)2 [M=Co(II) 1, Mn(II) 2; NITpPy=4-pyridyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] were characterized structurally and magnetically. Both structures consist of [M(II)(Phtfac)2(NITpPy)2] units, where the metal ion is in an octahedral environment bound to two NITpPy through the nitrogen atom of the pyridine ring. Compound 1 is the

Denise A. Souza; Antonio S. Florencio; José Walkimar de M. Carneiro; Stéphane S. Soriano; Carlos B. Pinheiro; Miguel A. Novak; Maria G. F. Vaz

2008-01-01

111

Synthesis, magnetic, thermal and structural properties of Co(II), Ni(II) and Cu(II) complexes containing isophthalato ligands  

NASA Astrophysics Data System (ADS)

A series of novel ternary Co(II), Ni(II) and Cu(II) complexes containing 2,2'-dipyridylamine (dipya), 2,2'-bipyridine (bipy), and 1,10-phenanthroline (phen), as aromatic diamine ligands, and dianion of isophthalic acid (ipht) have been prepared by ligand exchange reactions from diluted H 2O/EtOH solutions. The complexes were characterized by elemental analysis, IR spectroscopy, magnetic susceptibility measurements and TG and DSC analysis. Three complexes, Cu(dipya)(ipht)·H 2O ( 1), Co(dipya)(ipht)·2H 2O ( 2) and Cu(ipht)(phen)·2H 2O ( 5) are polymeric with bis-monodentate ipht, while the other two complexes M(bipy)(ipht)·4H 2O, M dbnd Co(II) ( 3) and Ni(II) ( 4), contain ipht as a counter ion. All Co(II) and Ni(II) complexes are (pseudo)octahedral, while Cu(II) complexes have square-pyramidal or distorted octahedral geometry. The variable temperature magnetic susceptibility measurements showed very weak antiferromagnetic behaviour for all complexes. Dehydration processes, decomposition mechanisms and thermal stability of 1- 5 are assumed. One complex from the above series, [Ni(bipy)(H 2O) 4](ipht) ( 4), and one additional complex, [Co(bipy)(ipht)] n ( 6), are obtained as single-crystals and their structures are determined from X-ray diffraction data. In both structures M(II) centers are in deformed octahedral environment and they are linked by hemi-ipht ligands ( 4) and two different bridging ipht ligands ( 6). Three-dimensional networks in 4 and 6 are governed by strong noncovalent interactions. The cations and ipht anions in 4 are connected by hydrogen bonds building double layers parallel to ab-plane that are further packed by ?- ? interactions. In 6 double chains extending along b-axis are strengthened by interchain ?- ? interactions constructing a three-dimensional framework.

Rogan, Jelena; Poleti, Dejan; Karanovi?, Ljiljana; Jagli?i?, Zvonko

2011-01-01

112

The role of charge degrees of freedom in Mott insulators: coupling of dielectric and magnetic properties in Cr-trimer complexes.  

NASA Astrophysics Data System (ADS)

Materials that are insulating owing to strong electron correlations are pervasive in condensed matter physics-the parent phase of high-Tc cuprates, colossal magnetoresistive manganites and quantum magnets. All are characterized by a large onsite coulomb repulsion relative to the dominant electron hopping. As such, at half-band filling the charge is localized. The properties of these materials are therefore commonly described solely in terms of their spin degrees of freedom, with little attention given to any further role of the charge. Certain classes of Mott insulator are predicted to break this paradigm, providing a direct correlation between the magnetic spin texture and the dielectric properties of a material. We observe such a correlation in Cr- trimer systems, which combined with recent theoretical developments, indicates a purely electronic mechanism for multiferroic behavior. Magnetic field strengths of the order of the exchange interaction strongly perturb the spin texture, which is evident as steps and plateau in the magnetization. The corresponding shifts in dielectric properties reveal the role of the charge degrees of freedom. Electron Spin Resonance (ESR) results and the prospect of novel dipole-active ESR giving rise to the possibility of negative refractive indices will also be discussed.

McDonald, Ross; Ayala Valenzuela, Oscar; Jaime, Marcelo; Mydosh, John

2009-03-01

113

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

114

SIMPRE: a software package to calculate crystal field parameters, energy levels, and magnetic properties on mononuclear lanthanoid complexes based on charge distributions.  

PubMed

This work presents a fortran77 code based on an effective electrostatic model of point charges around a rare earth ion. The program calculates the full set of crystal field parameters, energy levels spectrum, and wave functions, as well as the magnetic properties such as the magnetization, the temperature dependence of the magnetic susceptibility, and the Schottky contribution to the specific heat. It is designed for real systems that need not bear ideal symmetry and it is able to determine the easy axis of magnetization. Its systematic application to different coordination environments allows magneto-structural studies. The package has already been successfully applied to several mononuclear systems with single-molecule magnetic behavior. The determination of effective point charge parameters in these studies facilitates its application to new systems. In this article, we illustrate its usage with two example studies: (a) an ideal cubic structure coordinating a lanthanoid ion and (b) a system with slow relaxation of the magnetization, LiHo(x)Y((1-x))F(4). PMID:24000391

Baldoví, José J; Cardona-Serra, Salvador; Clemente-Juan, Juan M; Coronado, Eugenio; Gaita-Ariño, Alejandro; Palii, Andrew

2013-08-15

115

Formation of octapod MnO nanoparticles with enhanced magnetic properties through kinetically-controlled thermal decomposition of polynuclear manganese complexes  

NASA Astrophysics Data System (ADS)

Polynuclear manganese complexes are used as precursors for the synthesis of manganese oxide nanoparticles (MnO NPs). Altering the thermal decomposition conditions can shift the nanoparticle product from spherical, thermodynamically-driven NPs to unusual, kinetically-controlled octapod structures. The resulting increased surface area profoundly alters the NP's surface-dependent magnetism and may have applications in nanomedicine.Polynuclear manganese complexes are used as precursors for the synthesis of manganese oxide nanoparticles (MnO NPs). Altering the thermal decomposition conditions can shift the nanoparticle product from spherical, thermodynamically-driven NPs to unusual, kinetically-controlled octapod structures. The resulting increased surface area profoundly alters the NP's surface-dependent magnetism and may have applications in nanomedicine. Electronic supplementary information (ESI) available: Experimental details, TGA, TEM and diffraction data. See DOI: 10.1039/c3nr04832b

Douglas, Fraser J.; MacLaren, Donald A.; Tuna, Floriana; Holmes, William M.; Berry, Catherine C.; Murrie, Mark

2013-12-01

116

A three-spin complex [Ni(salox) 2(IM4Py) 2] containing salicylaldoxime and nitronyl nitroxide: Structure and magnetic properties  

Microsoft Academic Search

A transition metal-radical heterospin complex [Ni(salox)2(IM4Py)2] (1) (salox=salicylaldoxime, IM4Py=2-(4?-pyridinyl)-4,4,5,5-tetramethylimidazoline-l-oxyl) (1) has been synthesized based on the substitution reaction of Ni(salox)2(py)2 and IM4Py. Compound 1 exhibits a chain structure created by the intermolecular hydrogen bonds. Magnetic measurements show intermolecular antiferromagnetic interactions in 1.

Yue Ma; Wei Zhang; Yan Ou-Yang; Kazuyoshi Yoshimura; Dai-Zheng Liao; Zong-Hui Jiang; Shi-Ping Yan

2007-01-01

117

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

118

Magnetic properties of Acidithiobacillus ferrooxidans.  

PubMed

Understanding the magnetic properties of magnetotactic bacteria (MTBs) is of great interest in fields of life sciences, geosciences, biomineralization, biomagnetism, and planetary sciences. Acidithiobacillus ferrooxidans (At. ferrooxidans), obtaining energy through the oxidation of ferrous iron and various reduced inorganic sulfur compounds, can synthesize intracellular magnetite magnetosomes. However, the magnetic properties of such microorganism remain unknown. Here we used transmission electronmicroscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) assay, vibrating sample magnetometer (VSM), magneto-thermogravimetric analysis (MTGA), and low temperature magnetometry to comprehensively investigate the magnetic characteristics of At. ferrooxidans. Results revealed that each cell contained only 1 to 3 magnetite magnetosomes, which were arranged irregularly. The magnetosomes were generally in a stable single-domain (SD) state, but superparamagnetic (SP) magnetite particles were also found. The calcined bacteria exhibited a ferromagnetic behavior with a Curie Temperature of 454 °C and a coercivity of 16.36 mT. Additionally, the low delta ratio (?FC/?ZFC=1.27) indicated that there were no intact magnetosome chains in At. ferrooxidans. Our results provided the new insights on the biomineralization of bacterial magnetosomes and magnetic properties of At. ferrooxidans. PMID:23910310

Yan, Lei; Zhang, Shuang; Chen, Peng; Wang, Weidong; Wang, Yanjie; Li, Hongyu

2013-10-01

119

The role of charge degrees of freedom in Mott insulators: coupling of dielectric and magnetic properties in Cr-trimer complexes  

Microsoft Academic Search

Materials that are insulating owing to strong electron correlations are pervasive in condensed matter physics-the parent phase of high-Tc cuprates, colossal magnetoresistive manganites and quantum magnets. All are characterized by a large onsite coulomb repulsion relative to the dominant electron hopping. As such, at half-band filling the charge is localized. The properties of these materials are therefore commonly described solely

Ross McDonald; Oscar Ayala Valenzuela; Marcelo Jaime; John Mydosh

2009-01-01

120

Synthesis, spectroscopy, thermal analysis, magnetic properties and biological activity studies of Cu(II) and Co(II) complexes with Schiff base dye ligands.  

PubMed

Three azo group-containing Schiff base ligands, namely 1-{3-[(3-hydroxypropylimino) methyl]-4-hydroxyphenylazo}-4-nitrobenzene (2a), 1-{3-[(3-hydroxypropylimino) methyl]-4-hydroxyphenylazo}-2-chloro-4-nitrobenzene (2b) and 1-{3-[(3-hydroxypropylimino) methyl]-4-hydroxyphenylazo}-4-chloro-3-nitrobenzene (2c) were prepared. The ligands were characterized by elemental analysis, FTIR spectroscopy, UV-Vis spectroscopy, ¹³C- and ¹H-NMR spectroscopy and thermogravimetric analysis. Next the corresponding copper(II) and cobalt(II) metal complexes were synthesized and characterized by the physicochemical and spectroscopic methods of elemental analysis, FTIR spectroscopy, UV-Vis spectroscopy, magnetic moment measurements, and thermogravimetric analysis (TGA) and (DSC). The room temperature effective magnetic moments of complexes are 1.45, 1.56, 1.62, 2.16, 2.26 and 2.80 B.M. for complexes 3a, 3b, 3c, 4a 4b, and 4c, respectively, indicating that the complexes are paramagnetic with considerable electronic communication between the two metal centers. PMID:22643354

Ahmadi, Raziyeh Arab; Amani, Saeid

2012-01-01

121

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

122

Magnetic and Microstructure Properties of Iron - Rare - Earth - Boron Magnets  

Microsoft Academic Search

The new generation of cobalt free Fe-Nd-B permanent magnets have excellent hard magnetic properties which are attributed to a tetragonal Fe(,14)Nd(,2)B phase that has a high anisotropy and a high magnetic moment. The purpose of this work has been to study the magnetic and microstructure properties of the iron-rare-earth-boron based systems. The magnets were mostly made from heat-treated melt-spun samples.

Yi Fei Tao

1986-01-01

123

Some Structural Properties of Solar Magnetic Fields  

NASA Astrophysics Data System (ADS)

We discuss some results of the study of spatial characteristics of solar magnetic fields. The analysis is based on the magnetic field data obtained with a new spectromagnetograph installed on the IZMIRAN Tower Telescope (Fe I 6302.5 Å) (Kozhevatov et al., 2002), the data of the MSFC solar vector magnetograph (Fe I 5250.2 Å) and the data of longitudinal magnetic 96 m daily maps of SOHO/MDI magnetograph (Ni I 6768 Å) downloaded through Internet. Our study was directed in some different ways: the fractal properties of sunspots; fractal properties of space distribution of the magnetic fields along great distances comparable with the size of active regions or active complexes; fractal properties of active and quiet regions as global entities. To do it we used some different methods, particularly, the well known method using the relation between the area and the perimeter of magnetic field lines (see (Feder, 1988; Meunier, 1999; Nesme-Ribes at al., 1996; Balke et al., 1993)) and technique developed by Higuchi (1988), who applied it to the investigation of long time series. Note also that magnetic structure in terms of the fractal models was developed earlier in (Zelenyi & Milovanov, 1991; Milovanov & Zelenyi, 1993; Mogilevskii, 1994; Mogilevskii, 2001; Abramenko et al., 2002; Abramenko, 2005; Salakhudinova & Golovko, 2005). The main results are: 1. Fractal analysis of sunspot magnetic field indicated the existence of three families of self-similar contour lines roughly belonging to the umbra, penumbra and the ambient photosphere correspondingly. The greatest fractal dimension corresponds to the regions of weakest fields (ambient photosphere), the least one corresponds to the intermediate region (penumbra). 2. More detailed analysis shows that the fractal coefficient has a maximum (about 1.50) near the umbra--penumbra interface. 3. The global fractal numbers of space distribution of magnetic field on solar surface is closely connected with the mean absolute values of the longitudinal magnetic field for this surface. The fractal numbers diminish with the rising of mean magnetic field (from values about 2.0 for the relatively quiet region to 1- 1.2 for very active regions). 4. The dependences of fractal numbers of the space distribution of longitudinal and transversal fields versus mean longitudinal field are similar by their character but the fractal values for transversal field are higher than the corresponding factor values for longitudinal field by factor about 1.5. This means that the distribution of transversal field along the space is more chaotic than the distribution of longitudinal field.

Ioshpa, B.; Mogilevskii, E.; Obridko, V.

2007-05-01

124

Peculiarities of crystal structures and magnetic properties of Cu(II) and Ni(II) mixed-ligand complexes on the 1,3-dithiole-2-thione-4,5-dithiolate basis  

NASA Astrophysics Data System (ADS)

Mixed-ligand Cu(II) and Ni(II) complexes, [Cu(dmit)(bpy)]2 (I), [Ni(dmit)(phen)2] (II) and [Ni(dmit)(phen)2]·CH2Cl2 (III) (dmit=1.3-dithiole-2-thione-4.5-dithiolate, phen=1.10-phenantroline, bpy=2.2?-bipyridine) have been prepared by ligand exchange between phen or bpy and (Bu4N)2[M(dmit)2] (M=Ni, Cu) and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray analysis and by investigation of magnetic and resonance properties. In complex I, the monomeric units form dimers in a head-to-tail arrangement by weak coordination bonds between copper and dithiolate sulfur atoms and ?-? interactions between dmit and bpy from neighboring monomers. Dimers in I are further extended into chains by weak Cu-S(thione) contacts. In crystal packing of complex II and III, there exists a weak ?-? interaction between two parallel phen molecules of the adjacent complexes. As a consequence, the magnetic and resonance characteristics of copper complex may be described in approximation of exchange-coupled pairs of Cu2+ ions with ion spin S=1/2. The nickel complexes are described by isotropic exchange model for single-site spin S=1.

Starodub, V. A.; Vitushkina, S. V.; Kamenskyi, D.; Anders, A. G.; Cheranovskii, V. O.; Schmidt, H.; Steinborn, D.; Poto??ák, I.; Kaj?aková, M.; Radváková, A.; Feher, A.

2012-02-01

125

Sandwich complex-containing macromolecules: property tunability through versatile synthesis.  

PubMed

Sandwich complexes feature unique properties as the physical and electronic properties of a hydrocarbon ligand or its derivative are integrated into the physical, electronic, magnetic, and optical properties of a metal. Incorporation of these complexes into macromolecules results in intriguing physical, electrical, and optical properties that were hitherto unknown in organic-based macromolecules. These properties are tunable through well-designed synthetic strategies. This review surveys many of the synthetic approaches that have resulted in tuning the properties of sandwich complex-containing macromolecules. While the past two decades have seen an ever-growing number of research publications in this field, gaps remain to be filled. Thus, we expect this review to stimulate research interest towards bridging these gaps, which include the insolubility of some of these macromolecules as well as expanding the scope of the sandwich complexes. PMID:24474608

Abd-El-Aziz, Alaa S; Agatemor, Christian; Etkin, Nola

2014-03-01

126

Syntheses, structures and magnetic properties of Co(II) complexes based on H 4BTEC and 2-( n-pyridyl)benzimidazole ( n = 2, 3, and 4)  

NASA Astrophysics Data System (ADS)

The hydrothermal reactions of cobalt(II) salts with 1,2,4,5-benzenetetracarboxylic acid (H 4BTEC) and 2-( n-pyridyl)benzimidazole ( n = 2, 3, 4) led to the formation of three new coordination complexes, Namely, [Co(BTEC) 0.5(2-PyBIm) · H 2O] · H 2O ( 1), [Co(BTEC) 0.5(3-PyBIm) · H 2O] ( 2), [Co(H 2BTEC)(4-PyBIm) 2] · H 2O ( 3) were studied. The H 4BTEC ligands adopt different coordination modes according to the orientation of the pyridyl-sustituted benzimidazole. In complex 1, the BTEC 4- acts as four-dentate bridging ligand with all carboxylate groups adopt unidentate coordination fashion, leading a two-dimensional coordination network. While in 2, two of the four carboxylate groups adopt chelating bi-dentate coordination mode, and the others demonstrate uni-dentate coordination fashion; leading a one-dimensional chain with the nearest Co ⋯ Co separation being 5.057 Å. In 3, the adjacent carboxylate groups chelate the cobalt(II) atom in the uni-dentate coordination fashion, leading a one-dimensional undulating chain. Finally, all the complexes are extended into three-dimensional framework via hydrogen-bonding as well as ?-? interactions. The thermal stabilities and temperature-dependent magnetic susceptibilities for the three complexes were also studied.

Xia, Chang-Kun; Lu, Can-Zhong; Yuan, Da-Qiang; Zhang, Quan-Zheng; Wu, Xiao-Yuan; Zhang, Jian-Jun; Wu, Ding-Ming

2007-04-01

127

Synthesis, structures and magnetic properties of a family of nitrate-bridged octanuclear [Na2Ln6] (Ln = Dy, Tb, Gd, Sm) complexes.  

PubMed

A new family of octanuclear lanthanide compounds [Na2Ln6L8(C6H4NH2COO)2(C2H5OH)2(H2O)4(NO3)]·NO3·C2H5OH·nH2O [H2L = 2-{[(2-hydroxy-3-methoxyphenyl)methylidene]amino}benzoic acid; Ln = Dy (1) (n = 15); Tb (2), Gd (3) (n = 14); Sm (4) (n = 16)] have been prepared under hydrothermal conditions. The X-ray crystal structure analysis reveals that complexes 1-4 are isomorphous. The core of the structure is a [4 + 2] combination of an Ln4 cubane and an Ln2 unit. The two units are bridged by a nitrate ion, which is located in the center of the cluster and displays an unusual ?8-?(2):?(2):?(4) tridentate bridging mode. The magnetic studies for complex 1 show that the [Na2Dy6] unit exhibits slow magnetic relaxation behavior. PMID:23715465

She, Shixiong; Chen, Yanmei; Zaworotko, Michael J; Liu, Wei; Cao, Yanyuan; Wu, Jian; Li, Yahong

2013-08-01

128

Relationship between solare flare productivity and photospheric magnetic field properties  

Microsoft Academic Search

From a large number of magnetograms we compute several physical measures including the maximum horizontal gradient the length of neutral line etc These measures are used to describe photospheric magnetic field properties such as nonpotentiality and complexity which is believed to be closely related with flare production Our statistical results suggest that solar flare productivity increases with nonpotentiality and complexity

Y. M. Cui; H. N. Wang

2006-01-01

129

Magnetic properties of nanoscale conductors  

NASA Astrophysics Data System (ADS)

This doctoral dissertation examines some magnetic properties of nanoscale conductors. It comprises two classes of problems, namely, the response of closed nanoscopic systems to an external magnetic field, and the magnetization dependent transport of nanomagnets. In the first class of closed nanoscopic structures like quantum dots or metal grains, the system has discrete energy levels which can be modeled by Random Matrix Theory. The addition of a magnetic field is analyzed using a crossover random matrix model. In Chapter 2, we show that in the crossover there exist correlations between elements of the same eigenvector and between different eigenvectors. We show that these correlations between different eigenvectors lead to enhanced fluctuations of the electron-electron interaction matrix elements which are absent in the pure ensembles. In Chapter 3, we generalize these results to analyze the magnetic field response of energy levels in ultrasmall metal grains. We present a theory of mesoscopic fluctuations of g tensors and avoided crossing energies in a, small metal grain that contains both orbital and spin contributions to the g tensor. In the second class of problems we study two effects in small ferromagnets where the charge transport is coupled to the magnetization. In Chapter 4, we show that a sufficiently large unpolarized current can cause a spin-wave instability in a nanomagnet with asymmetric contacts. The dynamics beyond the instability is calculated analytically in the perturbative regime of small spinwave amplitudes, and numerically for larger currents. In Chapter 5, we study "anisotropic magnetoresistance fluctuations" which is the ferromagnetic analog of the well-known Universal Conductance; Fluctuations in metals. The conductance of a ferromagnetic particle depends on the relative orientation of the magnetization with respect to the direction of current flow. This phenomenon is known as "anisotropic magnetoresistance" and has no counterpart in normal-metal conductors. We show that quantum interference leads to an additional, random yet (statistically) universal dependence of the conductance of a ferromagnet on the magnetization direction. The mechanism for these anisotropic magnetoresistance fluctuations is the interplay of spin-orbit scattering, random impurity scattering, and the ferromagnet's exchange field.

Adam, Shaffique

130

Dinuclear and 1D iron(III) Schiff base complexes bridged by 4-salicylideneamino-1,2,4-triazolate: X-ray structures and magnetic properties.  

PubMed

Four new iron(III) complexes were obtained by the reaction of 4-salicylideneamino-1,2,4-triazole (Hsaltrz) and selected dinuclear ?-oxo-bridged iron(III) Schiff base complexes [{FeL(4)}(2)(?-O)], where L(4) represents a terminal tetradentate dianionic Schiff-base ligand. X-ray structural analysis revealed a novel bridging mode of ?N,?O of the saltrz ligand to form dinuclear complexes [{Fe(salen)(?-saltrz)}(2)]·CH(3)OH (1) (H(2)salen = N,N'-ethylenebis(salicylimine)) and [{Fe(salpn)(?-saltrz)}(2)] (2) (H(2)salpn = N,N'-1,2-propylenbis(salicylimine)), whereas one-dimensional (1D) zig-zag chains were formed in the case of [{Fe(salch)(?-saltrz)}·0.5CH(3)OH](n) (3) (H(2)salch = N,N'-cyclohexanebis(salicylimine)) and [Fe(salophen)(?-saltrz)](n) (4) (H(2)salophen = N,N'-o-phenylenebis(salicylimine)). It was also shown that the rigidity of the terminal ligand L(4) can be considered as the key factor for the molecular dimensionality of the products. The thorough magnetic analysis based on SQUID experiments, including the isotropic exchange and the zero-field splitting of both temperature and field dependent data, was performed for dimeric (1 and 2) and also for polymeric compounds (3 and 4) and revealed weak antiferromagnetic exchange mediated by the saltrz anions with much larger D-parameter (|D|?|J|). PMID:21968851

Herchel, Radovan; Pavelek, Lubomír; Trávní?ek, Zden?k

2011-11-28

131

Interface magnetism in complex oxide heterostructures  

Microsoft Academic Search

Magnetic oxides are an important class of materials from the perspectives of fundamental physics and technological applications. Advances in growth of high quality thin films and epitaxial oxide heterostructures over the years, have led to the realization of ideal condensed matter systems in which the complex and rich physics associated with cooperative phenomena can be explored. Examples of coupled phenomena

Hariharan Srikanth

2008-01-01

132

S-shaped decanuclear heterometallic [Ni8Ln2] complexes [Ln(iii) = Gd, Tb, Dy and Ho]: theoretical modeling of the magnetic properties of the gadolinium analogue.  

PubMed

The reaction of 8-quinolinol-2-carboaldoxime (LH2) with Ni(II) and Ln(III) salts afforded the heterometallic decanuclear compounds [Ni8Dy2(?3-OH)2(L)8(LH)2(H2O)6](ClO4)2·16H2O (1), [Ni8Gd2(?3-OH)2(L)8(LH)2(H2O)4(MeOH)2](NO3)2·12H2O (2), [Ni8Ho2(?3-OH)2(L)8(LH)2(H2O)4(MeOH)2](ClO4)2·2MeOH·12H2O (3) and [Ni8Tb2 (?3-OH)2(L)8(LH)2(MeOH)4(OMe)2]·2CH2Cl2·8H2O (4). While compounds 1-3 are dicationic, compound 4 is neutral. These compounds possess an S-shaped architecture and comprise a long chain of metal ions bound to each other. In all the complexes, the eight Ni(II) and two Ln(III) ions of the multimetallic ensemble are hold together by two ?3-OH, eight dianionic (L(2-)) and two monoanionic oxime ligands (LH(-)) whereas compound 4 has two ?3-OH, eight dianionic (L(2-)), two monoanionic oxime ligands (LH(-)) and two terminal methoxy (MeO(-)) ligands. The central portion of the S-shaped molecular wire is made up of an octanuclear Ni(II) ensemble which has at its two ends the Ln(III) caps. Magnetic studies on 1-4 reveal that the magnetic interactions between neighboring metal ions are negligible at room temperature. On the other hand, at lower temperatures in all the compounds anti-ferromagnetic interactions seem to be dominated. Analysis of the magnetic data for the Gd(III) derivative indicates Ni(II)-Ni(II) anti-ferromagnetic interactions and Gd(III)-Ni(II) ferromagnetic interactions at low temperatures. A theoretical density functional study on the magnetic behavior of the Gd(III) derivative suggests that while the weak ferromagnetic interaction between Gd(III) and Ni(II) is in line with the expectation of the magnetic interactions between orthogonal d and f orbitals, antiferromagnetic Ni(II)-Ni(II) interactions are related to the wide Ni-O-Ni angles (?102°) and quasi-planar conformation of the Ni2O2 core. PMID:24876072

Hossain, Sakiat; Das, Sourav; Chakraborty, Amit; Lloret, Francesc; Cano, Joan; Pardo, Emilio; Chandrasekhar, Vadapalli

2014-07-14

133

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

134

Syntheses, crystal structures, and magnetic properties of four new cyano-bridged bimetallic complexes based on the mer-[Fe(III)(qcq)(CN)3]- building block.  

PubMed

Four new cyano-bridged bimetallic complexes, [{Mn(III)(salen)}2{Fe(III)(qcq)(CN)3}2]n·3nCH3CN·nH2O (1) [salen = N,N'-ethylenebis(salicylideneiminato) dianion; qcq(-) = 8-(2-quinoline-2-carboxamido)quinoline anion], [{Mn(III)(salpn)}2{Fe(III)(qcq)(CN)3}2]n·4nH2O (2) [salpn = N,N'-1,2-propylenebis(salicylideneiminato)dianion], [{Mn(II)(bipy)(CH3OH)}{Fe(III)(qcq)(CN)3}2]2·2H2O·2CH3OH (3) (bipy = 2,2'-bipyridine), and [{Mn(II)(phen)2}{Fe(III)(qcq)(CN)3}2]·CH3CN·2H2O (4) (phen = 1,10-phenanthroline) have been synthesized and characterized both structurally and magnetically. The structures of 1 and 2 are both unique 1-D linear branch chains with additional structural units of {Mn(III)(salen/salpn)}{Fe(III)(qcq)(CN)3} dangling on the sides. In contrast, 3 and 4 are cyano-bridged bimetallic hexanuclear and trinuclear clusters, respectively. The intermolecular short contacts such as ?-? interactions and hydrogen bonds extend 1-4 into high dimensional supermolecular networks. Magnetic investigation reveals the dominant intramolecular antiferromagnetic interactions in 1, 3, and 4, while ferromagnetic and antiferromagnetic interactions coexist in 2. Alternating current measurement at low temperature indicates the existence of slow magnetic relaxation in 1 and 2, which should be due to the single ion anisotropy of Mn(III). PMID:24350592

Shen, Xiaoping; Zhou, Hongbo; Yan, Jiahao; Li, Yanfeng; Zhou, Hu

2014-01-01

135

Synthesis, structures, and magnetic properties of novel mononuclear, tetranuclear, and 1D chain Mn(III) complexes involving three related asymmetrical trianionic ligands.  

PubMed

The manganese(III) complexes studied in this report derive from asymmetrical trianionic ligands abbreviated H(3)L(i) (i = 4-6). These ligands are obtained through reaction of salicylaldehyde with "half-units", the latter resulting from monocondensation of different diamines with phenylsalicylate,. Upon deprotonation, L(i) (i = 4-6) possess an inner N(2)O(2) coordination site with one amido, one imine, and two phenoxo functions, and an outer amido oxygen donor. The trianionic character of such ligands yields original neutral complexes with the L/Mn stoichiometry. The crystal and molecular structures of three complexes have been determined at 190 K (1) or 180 K (2 and 3). Complex 1 crystallizes in the triclinic space group P (No. 2): a = 7.8582(14) A, b = 10.9225(16) A, c = 12.4882(18) A, alpha = 67.231(14) degrees, beta = 72.134(14) degrees, gamma = 82.589(13) degrees, V = 940.6(3) A(3), Z = 2. Complex 2 crystallizes in the orthorhombic space group Pbcn (Nuomicron. 60): a = 23.8283(15) A, b = 11.1605(7) A, c = 26.152(2) A, V = 6954.8(8) A(3), Z = 8, while complex 3 crystallizes in the monoclinic space group P2(1)/c (No. 14) with a = 11.7443(14) A, b = 7.5996(10) A, c = 18.029(2) A, beta = 100.604(10) degrees, V = 1581.6(3) A(3), Z = 4. Owing to hydrogen bonds and pi-pi stackings, the mononuclear neutral molecules of 1 are arranged in a 2D network while complexes 2 and 3 are tetranuclear and polymeric (1D chain) species, respectively, owing to the bridging ability of the oxygen atom of the amido function. The experimental magnetic susceptibilities of complexes 2 and 3 indicate the occurrence of similarly weak Mn(III)-Mn(III) antiferromagnetic interactions (J = -1.1 cm(-1)). Single ion zero-field splitting of manganese(III) must be taken into account for satisfactorily fitting the data by exact calculation of the energy levels associated to the spin Hamiltonian through diagonalization of the full matrix for axial symmetry in 2 (J = - 1.1 cm(-1), D(1) = 2.2 cm(-1), D(2) = -2.8 cm(-1)), D(1) and D(2) being associated to the six- and five-coordinate Mn ions, respectively. A weaker antiferromagnetic interaction (J = - 0.2 cm(-1)) operates through pi-pi stacking in complex 1. Complex 3 is a weak ferromagnet (ordering temperature approximately 7 K) as a result of the spin canting originating from the crystal packing. PMID:15074994

Costes, Jean-Pierre; Dahan, Françoise; Donnadieu, Bruno; Rodriguez Douton, Maria-Jesus; Fernandez Garcia, Maria-Isabel; Bousseksou, Azzedine; Tuchagues, Jean-Pierre

2004-04-19

136

Magnetic Properties of Disordered Fe3Al  

NASA Astrophysics Data System (ADS)

The magnetic properties of Fe3Al powders prepared by filing the ingot in both as-filed and annealed form are studied. Results of Mössbauer, X-ray diffraction and DC magnetization studies show that the magnetic properties are modified due to formation of non-magnetic Fe3AlC0.5 phase due to C intercalated on filing. The hyperfine fields obtained are explained in terms of nearest and next nearest neighbor configurations of 57Fe.

Nehra, J.; Kabra, K.; Jani, S.; Ranjith, P. M.; Lakshmi, N.; Venugopalan, K.

2011-07-01

137

Interface magnetism in complex oxide heterostructures  

NASA Astrophysics Data System (ADS)

Magnetic oxides are an important class of materials from the perspectives of fundamental physics and technological applications. Advances in growth of high quality thin films and epitaxial oxide heterostructures over the years, have led to the realization of ideal condensed matter systems in which the complex and rich physics associated with cooperative phenomena can be explored. Examples of coupled phenomena in heterostructures include exchange bias effects, magnetoelectric coupling and interplay between magnetism and superconductivity. In this talk, I will focus on three classes of oxide heterostructures --PLD-grown M-type barium hexaferrite(BaM)/barium strontium titanate(BST), CVD-grown CrO2/Cr2O3 bilayers and high-pressure sputtered LCMO/YBCO films. The common theme is the magnetic coupling across the interfaces. I will demonstrate that dynamic susceptibility and kinetic inductance experiments using a sensitive tunnel-diode oscillator (TDO) are effective probes of such coupled effects. In the case of CrO2/Cr2O3 and LCMO/YBCO, the interface coupling results in anomalous anisotropy, exchange bias in the former and complex interaction between the LCMO magnetism and YBCO vortex lattice in the latter. In BaM/BST heterostructures, I will discuss how interfacial coupling influences the microwave response that is both electrically and magnetically tunable.

Srikanth, Hariharan

2008-03-01

138

Synthesis, structures and magnetic properties of nickel(II), manganic(II) and zinc(II) complexes containing pyridyl-substituted nitronyl nitroxide and tris(2-benzimidazolymethyl)amine  

Microsoft Academic Search

Three new magnetic compounds were synthesized by using 2-(2?-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (NIT2Py) and tris(2-benzimidazolymethyl)amine (NTB) as ligands. The structures and magnetic properties of the complexes with formula [Ni(NIT2Py)(NTB)](ClO4)2(CH3OH) 1, [Mn(NIT2Py)(NTB)](ClO4)22 and {[Zn(NIT2Py)2(CH3OH)2](ClO4)2}{[Zn(NTB)(H2O)](ClO4)2} 3 were characterized. Compounds 1 and 2 both have [M(NIT2Py)(NTB)] structural units, where the metal ion is in an octahedral environment bound to one NIT2Py through one pyridyl nitrogen atom

Chen-Xi Zhang; Yu-Ying Zhang; Hai-Li Zhang; Yan Zhao; Ya-Qiu Sun

2009-01-01

139

Cu-Pd-Cu and Cu-Pt-Cu linear frameworks: synthesis, magnetic properties, and theoretical analysis of two mixed-metal complexes of dipyridylamide (dpa), isostructural, and isoelectronic with [Cu3(dpa)4Cl2]+.  

PubMed

The synthesis and crystal structure of two heteronuclear compounds stabilized by four dipyridylamide (dpa) ligands is reported. Cu2Pd(dpa)4Cl2 (1) and Cu2Pt(dpa)4Cl2 (2) exhibit an approximate D4 symmetry and a linear metal framework. They are structurally similar to the homotrinuclear complexes M3(dpa)4L2 already characterized with various transition metals (M=Cr, Co, Ni, Cu, Rh, Ru). With 26 metal valence electrons, they are also isoelectronic to the oxidized form of the tricopper complex [Cu3(dpa)4Cl2]+ (3), previously characterized and investigated by Berry et al.10 The magnetic properties and the EPR spectra of 1 and 2 are reported. The results for 1 are interpreted in terms of a weak antiferromagnetic interaction (2J=-7.45 cm(-1) within the framework of the Heisenberg Hamiltonian H=-2JAB ?A?B) between the Cu(II) magnetic centers. For 2, the antiferromagnetic interaction sharply decreases to <1 cm(-1). These properties are at variance with those of (3), for which a relatively strong antiferromagnetic interaction (2J=-34 cm(-1)) had been reported. DFT/UB3LYP calculations reproduce the decrease of the magnetic interaction from 3 to 1 and assign it to the role of the nonmagnetic metal in the transference of the superexchange coupling. However, the vanishing of the magnetic interaction in 2 could not be reproduced at this level of theory and is tentatively assigned to spin-orbit coupling. PMID:17929801

Liu, Isiah Po-Chun; Lee, Gene-Hsiang; Peng, Shie-Ming; Bénard, Marc; Rohmer, Marie-Madeleine

2007-11-12

140

Thermoelectric Properties of Complex Zintl Phases  

NASA Astrophysics Data System (ADS)

Complex Zintl phases make ideal thermoelectric materials because they can exhibit the necessary ``electron-crystal, phonon-glass'' properties required for high thermoelectric efficiency. Complex crystal structures can lead to high thermoelectric figure of merit (zT) by having extraordinarily low lattice thermal conductivity. A recent example is the discovery that Yb14MnSb11, a complex Zintl compound, has twice the zT as the SiGe based material currently in use at NASA. The high temperature (300K - 1300K) electronic properties of Yb14MnSb11 can be understood using models for heavily doped semiconductors. The free hole concentration, confirmed by Hall effect measurements, is set by the electron counting rules of Zintl and the valence of the transition metal (Mn^+2). Substitution of nonmagnetic Zn^+2 for the magnetic Mn^+2 reduces the spin-disorder scattering and leads to increased zT (10%). The reduction of spin-disorder scattering is consistent with the picture of Yb14MnSb11 as an underscreened Kondo lattice as derived from low temperature measurements. The hole concentration can be reduced by the substitution of Al^+3 for Mn^+2, which leads to an increase in the Seebeck coefficient and electrical resistivity consistent with models for degenerate semiconductors. This leads to further improvements (about 25%) in zT and a reduction in the temperature where the zT peaks. The peak in zT is due to the onset of minority carrier conduction and can be correlated with reduction in Seebeck coefficient, increase in electrical conductivity and increase in thermal conductivity due to bipolar thermal conduction.

Snyder, G. Jeffrey

2008-03-01

141

Syntheses, structures, and magnetic properties of unusual nonlinear polynuclear copper(II) complexes containing derivatives of 1,2,4-triazole and pivalate ligands.  

PubMed

Novel polynuclear Cu(II) complexes containing derivatives of 1,2,4-trizaole and pivalate ligands, [Cu(3)(mu(3)-OH)(mu-adetrz)(2)(piv)(5)(H(2)O)].6.5H(2)O (1) (adetrz = 4-amino-3,5-diethyl-1,2,4-triazole, piv = pivalate), [Cu(4)(mu(3)-OH)(2)(mu-atrz)(2)(mu-piv)(4)(piv)(2)].2MeOH.H(2)O (2) (atrz = 4-amino-1,2,4-triazole), [Cu(4)(mu(3)-OH)(2)(mu-tbtrz)(2)(mu-piv)(2)(piv)(4)].4H(2)O (3) (tbtrz = 4-tert-butyl-1,2,4-trizaole), and [Cu(4)(mu(3)-O)(2)(mu-admtrz)(4)(admtrz)(2)(mu-piv)(2)(piv)(2)].2[Cu(2)(mu-H(2)O)(mu-admtrz)(piv)(4)].13H(2)O [4 = 4a.2(4b).13H(2)O; admtrz = 4-amino-3,5-dimethyl-1,2,4-triazole], have been prepared and structurally characterized. 1 is an asymmetrical triangular complex containing a [Cu(3)(mu(3)-OH)] core with two Cu---Cu edges spanned by bridging adetrz ligands. 2, 3, and 4a are novel tetranuclear compounds containing a [Cu(4)(mu(3)-O)(2)] or [Cu(4)(mu(3)-OH)(2)] core with Cu---Cu edges spanned by bridging 1,2,4-triazole or pivalate ligands. 4b is a dinuclear compound with one admtrz and one water bridge, and it is the first dinuclear Cu(II) triazole complex with one bridging water molecule. 1 is one of few reported triangular Cu(II) complexes with derivatives of 1,2,4-triazole, while 2, 3, and 4a are the first group of the nonlinear tetranuclear Cu(II) compounds with derivatives of 1,2,4-triazole. Variable-temperature magnetic susceptibility studies on the powder samples of 1-3 reveal the overall antiferromagnetic coupling between Cu(II) ions with J values of -55.6 to -12.8 cm(-1) (1), -216.4 to 0 cm(-1) (2), and -259.8 to 4.8 cm(-1) (3). PMID:16241151

Zhou, Jian-Hao; Cheng, Ru-Mei; Song, You; Li, Yi-Zhi; Yu, Zhi; Chen, Xue-Tai; Xue, Zi-Ling; You, Xiao-Zeng

2005-10-31

142

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

143

Magnetic Properties of the Foum-Zguid Dyke (south Morocco)  

NASA Astrophysics Data System (ADS)

This work focuses on the study of magma flow and propagation, using rock magnetic methods on a group of cross sections of the Foum-Zguid Jurassic dyke in Southern Morocco. Thermomagnetic analysis show that Ti-poor titanomagnetite is the main magnetic carrier and petrographic analysis shows that the main Ti phase (ilmenite) can be either as exsolution within magnetite (core of the dyke) or as isolated grains (dyke rim). Bulk magnetic properties display distinct behavior according to distance to the dyke rim; grain size of the main magnetic carrier decreases towards the core of the dyke, while the natural remanent magnetization and the bulk magnetic susceptibility increase. Only the magnetic susceptibility ellipsoid close to the dyke rim corresponds to that usually found in thin dykes, with the magnetic foliation parallel to dyke borders. Maximum principal axis is in most cases either parallel or perpendicular to the intersection between the planes of magnetic foliation and dyke wall. Moreover, when this axis is perpendicular to the intersection it is associated with a more oblate magnetic susceptibility ellipsoid shape, indicating the presence of complex magnetic fabrics. Magnetic properties show that flow structures related with dyke propagation are only preserved close to the fast cooled dyke rims.

Silva, P. M.; Miranda, J. M.; Marques, F. O.; Henry, B.; Mateus, A.; Lourenco, N.

2003-12-01

144

Mono- and dinuclear iron complexes of bis(1-methylimidazol-2-yl)ketone (bik): structure, magnetic properties, and catalytic oxidation studies.  

PubMed

The newly synthesized dinuclear complex [Fe(III)(2)(?-OH)(2)(bik)(4)](NO(3))(4) (1) (bik, bis(1-methylimidazol-2-yl)ketone) shows rather short Fe···Fe (3.0723(6) Å) and Fe-O distances (1.941(2)/1.949(2) Å) compared to other unsupported Fe(III)(2)(?-OH)(2) complexes. The bridging hydroxide groups of 1 are strongly hydrogen-bonded to a nitrate anion. The (57)Fe isomer shift (? = 0.45 mm s(-1)) and quadrupole splitting (?E(Q) = 0.26 mm s(-1)) obtained from Mo?ssbauer spectroscopy are consistent with the presence of two identical high-spin iron(III) sites. Variable-temperature magnetic susceptibility studies revealed antiferromagnetic exchange (J = 35.9 cm(-1) and H = JS(1)·S(2)) of the metal ions. The optimized DFT geometry of the cation of 1 in the gas phase agrees well with the crystal structure, but both the Fe···Fe and Fe-OH distances are overestimated (3.281 and 2.034 Å, respectively). The agreement in these parameters improves dramatically (3.074 and 1.966 Å) when the hydrogen-bonded nitrate groups are included, reducing the value calculated for J by 35%. Spontaneous reduction of 1 was observed in methanol, yielding a blue [Fe(II)(bik)(3)](2+) species. Variable-temperature magnetic susceptibility measurements of [Fe(II)(bik)(3)](OTf)(2) (2) revealed spin-crossover behavior. Thermal hysteresis was observed with 2, due to a loss of cocrystallized solvent molecules, as monitored by thermogravimetric analysis. The hysteresis disappears once the solvent is fully depleted by thermal cycling. [Fe(II)(bik)(3)](OTf)(2) (2) catalyzes the oxidation of alkanes with t-BuOOH. High selectivity for tertiary C-H bond oxidation was observed with adamantane (3°/2° value of 29.6); low alcohol/ketone ratios in cyclohexane and ethylbenzene oxidation, a strong dependence of total turnover number on the presence of O(2), and a low retention of configuration in cis-1,2-dimethylcyclohexane oxidation were observed. Stereoselective oxidation of olefins with dihydrogen peroxide yielding epoxides was observed under both limiting oxidant and substrate conditions. PMID:21902227

Bruijnincx, Pieter C A; Buurmans, Inge L C; Huang, Yuxing; Juhász, Gergely; Viciano-Chumillas, Marta; Quesada, Manuel; Reedijk, Jan; Lutz, Martin; Spek, Anthony L; Münck, Eckard; Bominaar, Emile L; Klein Gebbink, Robertus J M

2011-10-01

145

Magnetic properties of Fe-based soft magnetic nanocrystalline alloys  

NASA Astrophysics Data System (ADS)

In this work the magnetic properties of FeCuSiBCuNb soft magnetic nanocrystalline alloys are reviewed. The characteristic magnetic transition associated with the magnetic decoupling of the ferromagnetic grains around the Curie point of the residual amorphous phase is studied through ac inductive techniques (temperature dependence of the magnetic permeability and coercive field). In particular, the study is focused on a Fe 68.5Mn 5Si 13.5B 9Cu 1Nb 3 melt-spun ribbon, where the inclusion of Mn introduces distinctive features in the crystallization and magnetization process of the sample. The main magnetic characteristics of these nanocrystalline systems (i.e. field dependence of the magnetic permeability and nonlinear terms) are analyzed taking into account the particular magnetization process of the exchange coupled ferromagnetic grains around the Curie point of the residual amorphous phase.

Gómez-Polo, C.

146

Rock magnetic properties of uncultured magnetotactic bacteria  

Microsoft Academic Search

Understanding the magnetic properties of magnetite crystals (Fe3O4) produced by magnetotactic bacteria (MTBs) is of fundamental interest in fields of geosciences, biomineralization, fine particle magnetism, and planetary sciences. The database of bulk magnetic measurements on MTBs is, however, still too sparse to allow for generalizations due to difficulties in obtaining bacteria cells in sufficient quantities from natural environments, and the

Yongxin Pan; Nikolai Petersen; Michael Winklhofer; Alfonso F. Davila; Qingsong Liu; Thomas Frederichs; Marianne Hanzlik; Rixiang Zhu

2005-01-01

147

Discovering the "Hidden" Properties of Magnets  

NSDL National Science Digital Library

Students will become familiar with the properties of magnets. They will design a data collection sheet to show where magnets are hidden in a closed box with their explanation of their findings. They will also design a game or activity using magnets and present their activity to the class.

Thill, Nancy

148

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

149

Vector Magnetic Property Measurement in Magnetic Steel Sheets under High Magnetic Flux Density Conditions  

NASA Astrophysics Data System (ADS)

In order to develop higher torque, lower weight and smaller sized magnetic actuators for driving electrical vehicles and robot arms, designing under high magnetic field and high exciting voltage is most effective. It is therefore very important to understand vector magnetic properties in electrical steel sheets under high magnetic flux density conditions. The vector magnetic properties mean the relationship between the magnetic flux density vector and the magnetic field strength vector and it is very difficult to measure the each component under high magnetic flux density conditions because of the magnetic saturation and the magnetic anisotropy. In this paper, accurate measurement techniques of the vector magnetic properties over 1.5T and measured vector magnetic properties are reported and discussed.

Maeda, Yoshitaka; Todaka, Takashi; Enokizono, Masato

150

Emergence of atypical magnetic and electronic properties in graphitic nanowiggles  

NASA Astrophysics Data System (ADS)

Graphitic nanowiggles (GNWs) are periodic repetitions of non-aligned finite-sized graphitic nanoribbon domains seamlessly stitched together without structural defects. These complex nanostructures have been recently fabricated using the self-assembly and subsequent fusion of small aromatic compound (Nature 466, 470 (2010)). The structures are predicted to possess unusual properties, such as tunable bandgaps and versatile magnetic behaviors (Phys. Rev. Lett. 107, 135501 (2011)). First-principles theory was used to highlight the microscopic origin of the emerging electronic and magnetic properties of the main subclasses of GNWs, thereby establishing a road-map for guiding the design and synthesis of specific GNWs with targeted nanoelectronic, optoelectronic, and spintronic properties. We will show the unusual versatility of GNWs' magnetic properties, we will highlight the variation of electronic properties with the details of the structures and how these structures can be used to transport electrons.

Meunier, Vincent; Costa-Girao, Eduardo; Liang, Liangbo; Cruz-Silva, Eduardo; Gomes Souza Filho, Antonio

2012-02-01

151

Design of magnetic coordination complexes for quantum computing.  

PubMed

A very exciting prospect in coordination chemistry is to manipulate spins within magnetic complexes for the realization of quantum logic operations. An introduction to the requirements for a paramagnetic molecule to act as a 2-qubit quantum gate is provided in this tutorial review. We propose synthetic methods aimed at accessing such type of functional molecules, based on ligand design and inorganic synthesis. Two strategies are presented: (i) the first consists in targeting molecules containing a pair of well-defined and weakly coupled paramagnetic metal aggregates, each acting as a carrier of one potential qubit, (ii) the second is the design of dinuclear complexes of anisotropic metal ions, exhibiting dissimilar environments and feeble magnetic coupling. The first systems obtained from this synthetic program are presented here and their properties are discussed. PMID:21818467

Aromí, Guillem; Aguilà, David; Gamez, Patrick; Luis, Fernando; Roubeau, Olivier

2012-01-21

152

Magnetic and Microstructure Properties of Iron - Rare - Earth - Boron Magnets.  

NASA Astrophysics Data System (ADS)

The new generation of cobalt free Fe-Nd-B permanent magnets have excellent hard magnetic properties which are attributed to a tetragonal Fe(,14)Nd(,2)B phase that has a high anisotropy and a high magnetic moment. The purpose of this work has been to study the magnetic and microstructure properties of the iron-rare-earth-boron based systems. The magnets were mostly made from heat-treated melt-spun samples. The addition of Co and Tb (Dy) in the Fe-Nd-B compounds enhances the relatively low Curie temperature and the coercivity, respectively. These outstanding hard magnetic properties find wide applications in industry. Partial substitution of Boron by other metalloids (Si, C, P) leads to a substantial decrease in properties of hard magnetic materials and to a substantial decrease in Curie temperature. The spin reorientation temperature in Fe-Nd-B alloys has been found to drop drastically with partial substitution of Fe by Ni, Mn and B by C, Si. The origin of high coercivity has been examined by correlating the hard magnetic properties with the microstructure. The high coercivities can be explained by domain wall pinning at grain boundaries.

Tao, Yi Fei

153

Hexa- and heptacoordinated manganese(II) dicyanamide complexes containing a tetradentate N-donor Schiff base: Syntheses, composition tailored architectures and magnetic properties  

NASA Astrophysics Data System (ADS)

Two 1D coordination polymers [Mn(L)(?1,5-dca)(MeOH)]n(ClO4)n (1) and [Mn(L)(?1,5-dca)]n(PF6)n (2) and a dinuclear compound [Mn2(L)2(?1,5-dca)2(dca)2]?H2O (3) [L = N,N'-(bis-(pyridin-2-yl)benzylidene)-ethane-1,2-diamine; dca = dicyanamide] have been isolated using one-pot synthesis of the building components in appropriate molar ratios and characterized. X-ray structural studies reveal that 1 forms a zigzag 1D chain through single Mn-(NCNCN)-Mn units in which each heptacoordinated manganese(II) center adopts a distorted pentagonal bipyramidal geometry with an MnN6O chromophore occupied with four N atoms of L, two nitrile N atoms of monobridged ?1,5-dca and one O atom of MeOH. In 2, each hexacoordinated metal(II) center has a distorted octahedral coordination environment with an MnN6 chromophore bound by four N atoms of L and two nitrile N atoms of two different single bridged ?1,5-dca units; the latter connects other neighboring metal centers in a non-ending fashion affording a linear 1D chain. Complex 3 is dinuclear where two [Mn(L)]2+ units are connected by double ?1,5-dca bridges with a distorted pentagonal bipyramidal environment. Variable-temperature magnetic susceptibility measurements of 1-3 show weak antiferromagnetic interactions among the metal centers through ?1,5-dca bridges.

Bhar, Kishalay; Sutradhar, Dipu; Choubey, Somnath; Ghosh, Rajarshi; Lin, Chia-Her; Ribas, Joan; Ghosh, Barindra Kumar

2013-11-01

154

Investigating the Properties of Magnets  

NSDL National Science Digital Library

In this activity, younger students encounter, discuss, and apply the basic characteristics of magnets and magnetism as they explore and elaborate on their experiences. Student groups implement some of the terminology and concepts appropriate to the study

Eichinger, John

2009-05-15

155

Magnetism in Complex Oxide Heterostructures Determined with Neutron Scattering  

NASA Astrophysics Data System (ADS)

With the creation of high quality superlattices consisting of complex oxide materials novel materials exhibiting a wide range of interesting phenomena are emerging. Due to the diverse physical properties of complex oxides, (e.g., ferromagnetism, antiferromagnetism, superconductivity), some of which can be varied by doping, the versatility in their applications is large. The physical properties in these new materials, often is tied to the behavior at the interfaces between the different components of the superlattice, and therefore requires detailed knowledge of the relationship between the chemical and electronic composition. Polarized neutron reflectometry (PNR) provides access to the depth-dependent magnitude and orientation of the magnetization and can therefore link the magnetic to the electronic and chemical properties, especially close to these interfaces. Several examples of our work will be presented, including that on La0.7Ca0.3MnO3/ YBa2Cu3O7-?/ La0.7Ca0.3MnO3 trilayers which exhibit the inverse superconducting spin switch behavior, and where suppression of the magnetization close to the interface, as well as a varying anisotropy axis have been determined [1]. Another example is work on digitally layered analogs of La1-xSrxMnO3, where PNR reveals an asymmetric distribution of the magnetization across the two components (antiferromagnetic) LaMnO3and SrMnO3, which has been linked to structural properties at the interfaces [2]. [4pt] [1] V. Peña, Z. Sefrioui, D. Arias, C. Leon, J. Santamaria, J. L. Martinez, S. G. E. te Velthuis, A. Hoffmann, Phys. Rev. Lett. 94 (2005) 057002. [0pt] [2] S. J. May, A. B. Shah, S. G. E. te Velthuis, M. R. Fitzsimmons, J. M. Zuo, X. Zhai, J. N. Eckstein, S. D. Bader, and A. Bhattacharya, Phys. Rev. B 77 (2008) 174409.

Te Velthuis, Suzanne G. E.

2009-03-01

156

Improved measurement of magnetic properties with 3D magnetic fluxes  

NASA Astrophysics Data System (ADS)

This paper, as a pioneering work, presents measurement techniques to characterize soft magnetic materials in three-dimensional (3D) space. A novel 3D magnetic property tester using cubic sample has been constructed and calibrated. Some phenomena and problems of measurement caused by the imperfect winding and misalignment of coils are analyzed. The correction methods are proposed and employed. The new soft magnetic composite SOMALOY™ 500 is investigated.

Zhong, J. J.; Zhu, J. G.; Lin, Z. W.; Guo, Y. G.; Sievert, J. D.

2005-04-01

157

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

158

Magnetic field properties of SSC model dipole magnets  

SciTech Connect

SSC 1.5m model dipole magnets were built and tested at Fermilab. Magnetic field properties were studied in term of transfer function variation and multipole components. The results were satisfactory. Observation of periodicity of remanent field along the axis is also reported.

Wake, M.; Bossert, R.; Carson, J.; Delchamps, S.; Jaffery, T.S.; Kinney, W.; Koska, W.; Lamm, M.J.; Strait, J. (Fermi National Accelerator Lab., Batavia, IL (United States)); Butteris, J.; Sims, R.; Winters, M. (Superconducting Super Collider Lab., Dallas, TX (United States))

1992-09-01

159

The magnetic properties of seamless steel pipe  

NASA Astrophysics Data System (ADS)

The magnetic and metallurgical properties of seamless pipe steel have been investigated as a function of position around the pipe circumference. No changes in magnetic properties were found to be associated with the four cycle spiral variations in pipe wall thickness introduced during forging. A weaker single cycle thickness variation was accompanied by a change both in magnetic properties and pearlite fraction. The coercive field predicted from an empirical relationship between grain size and ferrite and pearlite fractions was found to be in excellent agreement with that measured experimentally.

Willcock, S. N. M.; Tanner, B. K.; Mundell, P. A.

1987-03-01

160

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

161

Structure, magnetic behavior, and anisotropy of homoleptic trinuclear lanthanoid 8-quinolinolate complexes.  

PubMed

Three complexes of the form [Ln(III)3(OQ)9] (Ln = Gd, Tb, Dy; OQ = 8-quinolinolate) have been synthesized and their magnetic properties studied. The trinuclear complexes adopt V-shaped geometries with three bridging 8-quinolinolate oxygen atoms between the central and peripheral eight-coordinate metal atoms. The magnetic properties of these three complexes differ greatly. Variable-temperature direct-current (dc) magnetic susceptibility measurements reveal that the gadolinium and terbium complexes display weak antiferromagnetic nearest-neighbor magnetic exchange interactions. This was quantified in the isotropic gadolinium case with an exchangecoupling parameter of J = -0.068(2) cm(-1). The dysprosium compound displays weak ferromagnetic exchange. Variable-frequency and -temperature alternating-current magnetic susceptibility measurements on the anisotropic cases reveal that the dysprosium complex displays single-molecule-magnet behavior, in zero dc field, with two distinct relaxation modes of differing time scales within the same molecule. Analysis of the data revealed anisotropy barriers of Ueff = 92 and 48 K for the two processes. The terbium complex, on the other hand, displays no such behavior in zero dc field, but upon application of a static dc field, slow magnetic relaxation can be observed. Ab initio and electrostatic calculations were used in an attempt to explain the origin of the experimentally observed slow relaxation of the magnetization for the dysprosium complex. PMID:24520896

Chilton, Nicholas F; Deacon, Glen B; Gazukin, Olga; Junk, Peter C; Kersting, Berthold; Langley, Stuart K; Moubaraki, Boujemaa; Murray, Keith S; Schleife, Frederik; Shome, Mahasish; Turner, David R; Walker, Julia A

2014-03-01

162

Synthesis, Characterization, and Study of Magnetic Properties of Layered Materials  

NASA Astrophysics Data System (ADS)

Synthesis and characterization of layered materials in different systems were studied. The complexation of montmorillonite with iron polycations and its expansion with organic molecules mixed with iron (III) present magnetic properties of a dilute system. The magnetic properties due to structural changes as a result of the heating of the complexes at various temperatures and for varying time intervals were investigated. Another magnetic dilute system was studied in the compounds rm K_ {0.14}NiO_{2-delta} and rm Na_{0.12}K_ {0.087}NiO_{2-delta} that were obtained by the electrolysis of molten KOH or NaOH in which nickel nitrate was dissolved. Finally a study of new layered compounds related to the Ruddlesden -Popper (R-P) phases, which play an important role in superconductivity, was carried out.

Govea, Laura Violeta

1995-01-01

163

High temperature magnetic properties of oxide superconductors  

NASA Astrophysics Data System (ADS)

The magnetic properties of MBa 2Cu 3O 7-x with M = Y and La have been investigated above room temperature up to 1700 K. A pronounced difference in the high temperature magnetic susceptibility behavior between these compounds and samples containing Eu and Gd is reported. Initial results on the in situ magnetic susceptibility variation during the preparation process of YBa 2Cu 3O 7-x are presented.

Jenny, H.; Leemann, G.; Walz, B.; Gu¨ntherodt, H.-J.

1988-06-01

164

Oxide magnetic semiconductors: Materials, properties, and devices  

NASA Astrophysics Data System (ADS)

We give a brief introduction to the oxide (ZnO, TiO2, In2O3, SnO2, etc.)-based magnetic semiconductors from fundamental material aspects through fascinating magnetic, transport, and optical properties, particularly at room temperature, to promising device applications. The origin of the observed ferromagnetism is also discussed, with a special focus on first-principles investigations of the exchange interactions between transition metal dopants in oxide-based magnetic semiconductors.

Tian, Yu-Feng; Hu, Shu-Jun; Yan, Shi-Shen; Mei, Liang-Mo

2013-08-01

165

Magnetic Properties of Polymers Containing Ferrocene.  

National Technical Information Service (NTIS)

Ferrocene was copolymerized with alpha-bromo-naphthalene and with n-dichlorobenzene, and the electron paramagnetic resonance and magnetic properties of the resulting substances were examined. Possible resons for the observed ferromagnetism are discussed.

P. M. Belash Y. M. Paushkin

1966-01-01

166

Structure and magnetic properties of ? compounds  

NASA Astrophysics Data System (ADS)

In the present work, the influence of substitution of V for Mn on the structure and magnetic properties of 0953-8984/10/1/019/img13 compounds has been investigated. The lattice constants, the Curie and spin-reorientation temperatures, the anisotropy field and the saturation magnetization have been determined as a function of the V content.

Hu, Jifan; Yang, Fuming; Mei, Liangmo; Li, Hua; Wang, Jianli; Luan, Kaizheng; Tang, Ning; Zhou, Kaiwen; Wang, Yingang; de Boer, F. R.

1998-01-01

167

Synthesis and Properties of Magnetic Fine Particles  

Microsoft Academic Search

Magnetic fine particles with a variety of compositions and sizes have been prepared by aerosol and coprecipitation technique. Their magnetic properties are shown to be either similar to or quite different from those of their bulk counterparts. Iron oxide, barium iron oxide and neodynium iron based fine particles have been synthesized by an aerosol technique which produced particles with average

Zhongxun Tang

1991-01-01

168

Thermal and magnetic properties of neutron stars  

SciTech Connect

The interaction of the magnetic field with the heat flux in neutron stars is investigated. It is proposed that the magnetic field develops as a result of thermal processes in the liquid and solid phases of neutron star envelopes. Necessary conditions for the growth to occur are derived and it is shown that surface fields comparable to those observed would result. The magnetization of neutron stars in binary systems (which have magnetic properties differing substantially from those of isolated pulsars) can be explained by thermal processes associated with accretion flows. In order to study magnetic effects on neutron star cooling a number of subsidiary issues are considered. The thermal structure of unmagnetized neutron star envelopes is examined using approximate analytical models. From the results it is possible to justify a number of simplifying assumptions and extend them to the magnetized case. The effect of the field on the magnetic properties of the electron gas in neutron star crusts is considered. It is shown that the gas is unstable to the formation of domains of alternating magnetization. The influence of the field on the electron transport properties of neutron star envelopes is examined in detail. Accurate expressions are derived for all components of the relevant transport tensors, taking into account quantum mechanical and relativistic effects. Finally, these results are used to study the thermal structure of magnetized neutron star envelopes.

Hernquist, L.E.

1985-01-01

169

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

170

Magnetic properties of Np 2T 3X 4 compounds  

NASA Astrophysics Data System (ADS)

The magnetic and electronic properties of Np 2T 3X 4 compounds, as inferred from 237Np Mössbauer spectroscopy, magnetization and resistivity measurements, are reported. Np 2Mo 3Si 4 orders at TN?47 K into an AF phase and becomes ferrimagnetic at T''?38 K, Np 2Tc 3Si 4 and Np 2Tc 3Ge 4 order antiferromagnetically, respectively, at TN?19 K and TN?15 K. All compounds exhibit complex Mössbauer spectra which were reproduced assuming the occurrence of three distinct Np 3+ sites with different magnetic moments and moreover an extra, zero-moment Np 3+ site is always associated with the AF-phases. The variation of the magnetic properties along the series may be explained by Np-transition metal hybridization and Kondo effect.

Colineau, E.; Wastin, F.; Rebizant, J.; Boulet, P.

2001-05-01

171

Pentachloro(pyrazine)rhenate(IV) complex as precursor of heterobimetallic pyrazine-containing Re(IV)2M(II) (M = Ni, Cu) species: synthesis, crystal structures and magnetic properties.  

PubMed

Three novel Re(IV) mononuclear complexes of formulae NBu4[ReC15(pyz)] (1), NH2Me2[ReCl5(pyz)] (2) and NH4[ReCl5(pyz)].0.75H2O (3), (pyz being pyrazine; NBu4+ = tetra-n-butylammonium cation, NH2Me2+ = dimethylammonium cation and NH4+ = ammonium cation), were synthesized by ligand substitution reaction from [ReCl6]2- anion and pyrazine in N,N-dimethylformamide (DMF). In addition, two new heterobimetallic compounds, the salt namely [ReCl5(pyz)]2[Ni(cyclam)](4) (cyclam = 1,4,8,11-tetraazacyclotetradecane) and the heterotrinuclear [{ReCl5(mu-pyz)}2Cu(DMF)4] (5) complex, were prepared by using as precursor 1 and 3, respectively. Compounds 1-5 were characterized by single-crystal X-ray diffraction. 1-3 are made up of discrete [ReCl5(pyz)]- anions and NBu4 (1), NH2Me2+ (2) and NH4+ (3) cations. [ReCl5(pyz)]- unit interacts toward Ni(II) (4) and Cu(II) (5) metal ions through different modes. In 4 two [ReCl5(pyz)]- anions weakly interact with a [Ni(cyclam)]2+ cation through chloro atoms, while compound 5 is a heterotrinuclear pyrazine-bridged Re(IV)2Cu(II) complex made up of [ReCl5(pyz)]- anions and [Cu(DMF)4]2+ cations. The magnetic properties of 1-5 were investigated in the temperature range 1.9-300 K. The magnetic behaviour of 1 is that of a magnetically diluted Re(IV) complex with a large value of zero-field splitting of the ground state (/2D/ is ca. 18.8(1) cm(-1)), whereas those of 2 and 3 are typical of antiferromagnetically coupled systems exhibiting susceptibility maxima at 10 (2) and 12 K (3). Compound 4 shows antiferromagnetic interactions between Re(IV) metal ions, Ni(II) being diamagnetic (because of its square-planar geometry), while 5 exhibits a ferromagnetic coupling between Re(IV) and Cu(II) metal ions across the pyrazine bridges with a J(ReCu), value of +11.8(1) cm(-1). PMID:19024357

Martínez-Lillo, José; Armentano, Donatella; Marino, Nadia; Arizaga, Livia; Chiozzone, Raúl; González, Ricardo; Kremer, Carlos; Cano, Joan; Faus, Juan

2008-09-14

172

Fast magnetic relaxation in an octahedral dysprosium tetramethyl-aluminate complex.  

PubMed

Ab initio calculations on the octahedral dysprosium aluminate complex [Dy(AlMe4)3] (1) predict weak SMM properties. Dynamic magnetic susceptibility measurements on 1 confirm the theoretical predictions, revealing fast relaxation of the magnetization via quantum tunnelling. PMID:24121786

König, Sonja N; Chilton, Nicholas F; Maichle-Mössmer, Cäcilia; Pineda, Eufemio Moreno; Pugh, Thomas; Anwander, Reiner; Layfield, Richard A

2014-02-28

173

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

174

High-pressure synthesis, structural and complex magnetic properties of the ordered double perovskite Pb2NiReO6.  

PubMed

The ordered double perovskite Pb2NiReO6 has been prepared at 6 GPa and temperatures ranging from 1273 to 1373 K. Its crystal structure determined by X-ray powder diffraction and selected area electron diffraction shows monoclinic symmetry with centrosymmetric space group I2/m (a = 5.6021(1) Å, b = 5.6235(1) Å, c = 7.9286(1) Å and ? = 90.284°(1)). High angle annular dark field microscopy studies reveal the existence of compositional microdomains. The compound displays a re-entrant spin-glass transition from a ferrimagnetic ordering below T(N) ~ 37 K between the Re(+5) and Ni(+3) (high spin configuration) magnetic sublattices to a spin-glass configuration. Magnetic field dependent magnetization measurements revealed wasp-waisted hysteresis loops at 5 K. These shaped features originate from the antiferromagnetic/ferromagnetic (AFM/FM) competing interactions. PMID:24169530

Stoyanova-Lyubenova, Teodora; Dos santos-García, Antonio J; Urones-Garrote, Esteban; Torralvo, María José; Alario-Franco, Miguel Á

2014-01-21

175

Synthesis, crystal structures, and magnetic properties of a new family of heterometallic cyanide-bridged Fe(III)2M(II)2 (M=Mn, Ni, and Co) square complexes.  

PubMed

New heterobimetallic tetranuclear complexes of formula [Fe(III){B(pz)(4)}(CN)(2)(?-CN)Mn(II)(bpy)(2)](2)(ClO(4))(2)·CH(3)CN (1), [Fe(III){HB(pz)(3)}(CN)(2)(?-CN)Ni(II)(dmphen)(2)](2)(ClO(4))(2)·2CH(3)OH (2a), [Fe(III){B(pz)(4)}(CN)(2)(?-CN)Ni(II)(dmphen)(2)](2)(ClO(4))(2)·2CH(3)OH (2b), [Fe(III){HB(pz)(3)}(CN)(2)(?-CN)Co(II)(dmphen)(2)](2)(ClO(4))(2)·2CH(3)OH (3a), and [Fe(III){B(pz)(4)}(CN)(2)(?-CN)Co(II)(dmphen)(2)](2)(ClO(4))(2)·2CH(3)OH (3b), [HB(pz)(3)(-) = hydrotris(1-pyrazolyl)borate, B(Pz)(4)(-) = tetrakis(1-pyrazolyl)borate, dmphen = 2,9-dimethyl-1,10-phenanthroline, bpy = 2,2'-bipyridine] have been synthesized and structurally and magnetically characterized. Complexes 1-3b have been prepared by following a rational route based on the self-assembly of the tricyanometalate precursor fac-[Fe(III)(L)(CN)(3)](-) (L = tridentate anionic ligand) and cationic preformed complexes [M(II)(L')(2)(H(2)O)(2)](2+) (L' = bidentate ?-diimine type ligand), this last species having four blocked coordination sites and two labile ones located in cis positions. The structures of 1-3b consist of cationic tetranuclear Fe(III)(2)M(II)(2) square complexes [M = Mn (1), Ni (2a and 2b), Co (3a and 3b)] where corners are defined by the metal ions and the edges by the Fe-CN-M units. The charge is balanced by free perchlorate anions. The [Fe(L)(CN)(3)](-) complex in 1-3b acts as a ligand through two cyanide groups toward two divalent metal complexes. The magnetic properties of 1-3b have been investigated in the temperature range 2-300 K. A moderately strong antiferromagnetic interaction between the low-spin Fe(III) (S = 1/2) and high-spin Mn(II) (S = 5/2) ions has been found for 1 leading to an S = 4 ground state (J(1) = -6.2 and J(2) = -2.7 cm(-1)), whereas a moderately strong ferromagnetic interaction between the low-spin Fe(III) (S = 1/2) and high-spin Ni(II) (S = 1) and Co(II) (S = 3/2) ions has been found for complexes 2a-3b with S = 3 (2a and 2b) and S = 4 (3a and 3b) ground spin states [J(1) = +21.4 cm(-1) and J(2) = +19.4 cm(-1) (2a); J(1) = +17.0 cm(-1) and J(2) = +12.5 cm(-1) (2b); J(1) = +5.4 cm(-1) and J(2) = +11.1 cm(-1) (3a); J(1) = +8.1 cm(-1) and J(2) = +11.0 cm(-1) (3b)] [the exchange Hamiltonian being of the type H? = -J(S?(i)·S?(j))]. Density functional theory (DFT) calculations have been used to substantiate the nature and magnitude of the exchange magnetic coupling observed in 1-3b and also to analyze the dependence of the exchange magnetic coupling on the structural parameters of the Fe-C-N-M skeleton. PMID:21630643

Pardo, Emilio; Verdaguer, Michel; Herson, Patrick; Rousselière, Helene; Cano, Joan; Julve, Miguel; Lloret, Francesc; Lescouëzec, Rodrigue

2011-07-01

176

Microwave complex conductivity of the YBCO thin films as a function of static external magnetic field  

NASA Astrophysics Data System (ADS)

A sapphire rod resonator operating at microwave frequencies was used to determine the electric properties of 600 nm thick YBCO films in the superconducting state. The rigorous electromagnetic modelling was applied to transform the measured Q-factor and the resonant frequency to the complex conductivity of high accuracy, which was previously shown to describe the intrinsic properties of superconductor thin films in more precise manner than the complex impedance. Static external magnetic field induces typical transition to normal state due to introduction of magnetic vortices into the sample. Observed magnetic hysteresis has the origin in the strong temperature dependent pinning. Additional energy absorption at about 1.5 T was observed.

Krupka, J.; Judek, J.; Jastrzebski, C.; Ciuk, T.; Wosik, J.; Zdrojek, M.

2014-03-01

177

Magnetic Properties of Iron Clusters  

Microsoft Academic Search

In this dissertation we present results of experiments designed to map out the magnetic behavior of free iron clusters. We report a decrease in the magnetic moment from a high of 3.06mu_{B} \\/atom for 70 atom clusters down to the bulk value of 2.2mu_{B} for clusters of 700 or more atoms. The clusters are superparamagnetic for vibrational temperatures above 248K.

Joseph Girard Louderback IV

1995-01-01

178

Structural and viscous properties of bidispersed magnetic colloids  

NASA Astrophysics Data System (ADS)

We demonstrate here certain structural properties and flow behavior of bidispersed magnetic colloids. Under the application of magnetic field it is observed that the magnetic nanoparticles are filled inside the structural microcavities formed due to the association of large magnetic particles, and some of the magnetic nanoparticles are attached at the end of the chains formed by the large particles. These structural properties are useful for the demonstrations of the assembly of complex structures with unique optical properties and are of fundamental importance in improving our understanding of self-assembly processes and stability of bidispersed MR fluids. The magnetic field dependent flow behavior is also quite different from the monodispersed magnetic colloid. It is also observed that at particular concentration of large particles the change in field induced viscosity is maximum than the other concentrations due to peculiar structure formation between the two sized particles and their energy minimization. The flow behavior can be useful for the study of micro and nanofluidic devices.

Virpura, Hiral; Parmar, Mayur; Dave, Vishaka; Patel, Rajesh

2014-04-01

179

The magnetic detection of material properties  

SciTech Connect

This paper reports that because of the nature of ferromagnetism, the magnetic properties of a material can provide useful information about other material properties. For example, magnetic-hysteresis parameters and Barkhausen-effect measurements are affected by the microstructure of materials and by applied or residual stresses. Considerable work has shown that magnetic hysteresis and the Barkhausen effect can be used to investigate the condition of materials or components by nondestructive means. Such investigations can be carried out fairly easily under laboratory conditions; adapting the methods to in-service components is more problematic.

Devine, M.K. (Ames Lab., IA (United States))

1992-10-01

180

Magnetic properties of nanosize iron clusters  

SciTech Connect

Isolated, monodisperse {alpha}-Fe clusters between 1.4 and 15 nm in diameter were prepared inside inverse micelles using an oil-continuous, nonaqueous system. The magnetic properties of these clusters were studied in a SQUID magnetometer as a function of cluster size, temperature and applied magnetic field. The blocking temperature, coercive field and remanent moment of 12.5 nm Fe clusters in inverse micelles are significantly lower than those reported for clusters of similar {alpha}-Fe core size but with a surface oxide. The novel synthesis technique may yield metallic clusters with essentially intrinsic magnetic properties.

Venturini, E.L.; Wilcoxon, J.P.; Newcomer, P.P.

1993-12-31

181

Topological properties and dynamics of magnetic skyrmions.  

PubMed

Magnetic skyrmions are particle-like nanometre-sized spin textures of topological origin found in several magnetic materials, and are characterized by a long lifetime. Skyrmions have been observed both by means of neutron scattering in momentum space and microscopy techniques in real space, and their properties include novel Hall effects, current-driven motion with ultralow current density and multiferroic behaviour. These properties can be understood from a unified viewpoint, namely the emergent electromagnetism associated with the non-coplanar spin structure of skyrmions. From this description, potential applications of skyrmions as information carriers in magnetic information storage and processing devices are envisaged. PMID:24302027

Nagaosa, Naoto; Tokura, Yoshinori

2013-12-01

182

Magnetic properties of porous iron compacts  

SciTech Connect

Magnetic hysteresis measurements, magnetoacoustic emission, and the Barkhausen effect have been used to investigate the magnetic properties of six porous iron compacts with porosities in the range of 0.3-6.2% and pore sizes in the range 1.6-13.2 ..mu.. m. Coercivity and maximum permeability varied with pore size, showing respectively a maximum and a minimum for pore areas in the range 50-100 (..mu.. m)/sup 2/, corresponding to pore diameters 8-11 ..mu.. m. Significant correlations were found between several of the magnetic parameters including a fundamental relationship between coercivity, initial permeability, and maximum differential permeability. There were also indicates of a correlation between magnetic properties and the initial molding pressure, although these were not conclusive. However, none of the magnetic properties was found to vary in a progressive manner with percentage porosity, although it is conceivable that if all other variables, such as pore size and grain size, remained constant, that changes in magnetic properties with porosity could be detected from magnetic measurements.

Jiles, D.C.; Owen, C.V.; Spitzig, W.A.

1987-09-01

183

Variability of magnetic soil properties in Hawaii  

NASA Astrophysics Data System (ADS)

Magnetic soils can seriously hamper the performance of electromagnetic sensors for the detection of buried land mines and unexploded ordnance (UXO). Soils formed on basaltic substrates commonly have large concentrations of ferrimagnetic iron oxide minerals, which are the main cause of soil magnetic behavior. Previous work has shown that viscous remanent magnetism (VRM) in particular, which is caused by the presence of ferrimagnetic minerals of different sizes and shapes, poses a large problem for electromagnetic surveys. The causes of the variability in magnetic soil properties in general and VRM in particular are not well understood. In this paper we present the results of laboratory studies of soil magnetic properties on three Hawaiian Islands: O"ahu, Kaho"olawe, and Hawaii. The data show a strong negative correlation between mean annual precipitation and induced magnetization, and a positive correlation between mean annual precipitation and the frequency dependent magnetic behavior. Soil erosion, which reduces the thickness of the soil cover, also influences the magnetic properties.

van Dam, Remke L.; Harrison, J. Bruce J.; Hendrickx, Jan M. H.; Borchers, Brian; North, Ryan E.; Simms, Janet E.; Jasper, Chris; Smith, Christopher W.; Li, Yaoguo

2005-06-01

184

Magneto--optical properties of complex oxides  

NASA Astrophysics Data System (ADS)

We investigated the magneto-optical properties of ?-Fe2O3, frustrated system Ni3V2O8, and rare earth indium oxides like DyInO3 in order to understand the interplay between charge and magnetism. We discovered that hematite appears more red in applied magnetic field than in zero field conditions, an effect that is amplified by the presence of the spin flop transition. Furthermore, magnetic field aligns the spins into fully polarized state and induces optical band gap change in Ni3V2O8. As a consequence, Ni3V2O8 appears more green in 35 T. f electron excitations in DyInO3 changes dramatically in applied magnetic field because of enormous spin-orbit coupling effect in the rare earth elements. These findings advance our understanding of spin-charge coupling and motivate spectroscopic work on other functional materials under extreme conditions.

Chen, Peng; Holinsworth, Brian; O'Neal, Kenneth; Brinzari, Tanea; Musfeldt, Janice; Lee, Nara; Xuan, Luo; Cheong, Sang; Rogado, Nyrissa; Cava, Robert; Wang, Yaqi; Lorenz, Bernd; McGill, Steve

2013-03-01

185

Magnetic properties and spin dynamics in magnetic molecule {Mn3}  

NASA Astrophysics Data System (ADS)

We report dc magnetization and nuclear magnetic resonance (NMR) measurements in a trinuclear manganese compound, {Mn3}, with formula [Mn3O(O2CCH3)6(C5H5N)3].C5H5N. The magnetic properties are characterized by two antiferromagnetic (AF) coupling constants, J=-7.9 K and J'=-27.6 K. 1H NMR linewidth strongly depends on both the magnetic field and temperature, and is quantitatively explained by the dipolar interaction between proton nuclei and Mn ion spins. The strong enhancement of T1-1 at low temperatures is ascribed to the slowing down of magnetic fluctuations resulting from building up of AF correlations. From the T dependence of T1-1 at low T, we obtained the gap ?NMR=19 K, in qualitative agreement with the gap ??12 K obtained from susceptibility ?.

Suh, B. J.; Procissi, D.; Jung, J. K.; Bud'Ko, S.; Jeon, W. S.; Kim, Y. J.; Jung, D.-Y.

2003-05-01

186

Experimental study of magnetic slurries regarding magnetic properties  

SciTech Connect

The aim of this study was to assess the basic magnetic properties of a mixture composed of a commercial lubricant and soft magnetic iron particles, where the particle content is significantly higher than in conventional magnetic fluids, due to the fact that the particles verge on the sedimentation level. This so called magnetic slurry can, then, be regarded as a highly ductile magnetic conducting material for tentative use in magnetic circuit that can change shape under operation. The high particle content results in high saturation field densities that extend the application field towards electric power engineering. This paper, therefore, focuses on properties like relative permeability losses, the Q-factor and the efficiency for the power frequencies 50 and 400 Hz. It shows that the relative permeabilities are low (below 10). The values of the efficiency and the Q-factor decrease considerably above 0.5 T. That limits the application of the studied slurry in electric power engineering. In such applications, the powder properties must be improved.

Engdahl, G. [ABB Corporate Research, Vaesteraas (Sweden)] [ABB Corporate Research, Vaesteraas (Sweden); Lerebourg, B. [Ecole Nationale Superieure d`Hydraulique et de Mecanique de Grenoble, St. Martin d`Heres (France)] [Ecole Nationale Superieure d`Hydraulique et de Mecanique de Grenoble, St. Martin d`Heres (France)

1996-09-01

187

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

188

Synthesis and magnetic properties of new nickel(II)-copper(II)-nickel(II) trinuclear complexes with irregular spin-state structure  

Microsoft Academic Search

Four novel heterotrinuclear complexes were prepared, namely {[Ni(L)2]2[Cu(pba)]}(ClO4)2, where pba = pro-pylene-1,3-bis(oxamato) and L = 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO2-phen), 2,2'-bipyridyl (bpy), 4,4'-dimethyl-2,2'-bipyridyl (Me2bpy). Based on i.r., elemental analyses, conductivity measurements and electronic spectra oxamato-bridged structures are proposed for these complexes, consisting of two nickel(II) ions, each in a distorted octahedral environment, and a copper(II) ion in a square planar environment,

Ming-Ming Miao; Dai-Zheng Liao; Zong-Hui Jiang; Geng-Lin Wang

1994-01-01

189

Ferromagnetic exchange coupling in a new bis(?-chloro)-bridged copper(II) Schiff base complex: Synthesis, structure, magnetic properties and catalytic oxidation of cycloalkanes  

Microsoft Academic Search

A new (?-chloro)-bridged complex [Cu(HL)Cl]2·H2O (1) with the Schiff base ligand H2L, [2-((E)-(2-hydroxyethylimino)methyl)-4-bromophenol], has been synthesized and characterized by elemental analysis, IR, UV–Vis and EPR spectroscopic studies. X-ray diffraction studies show that 1 is a binuclear CuII complex with a pair of chlorine atoms bridging the copper atoms in a central Cu2Cl2 core. Each copper atom in 1 adopts a

Santarupa Thakurta; Partha Roy; Georgina Rosair; Carlos J. Gómez-García; Eugenio Garribba; Samiran Mitra

2009-01-01

190

Synthesis, structural characterization and magnetic properties of new tripeptide Schiff base heterotrinuclear Cu(II)–M(II)–Cu(II) (M=Ni and Mn) complexes  

Microsoft Academic Search

Two novel heterotrinuclear Cu(II)-M(II)-Cu(II) (M=Ni and Mn) complexes, [Ni(H2O)4(CuL)2]·7H2O (1), [Mn(H2O)4(CuL)2]·8H2O (2), have been obtained by the self-assembly of the mononuclear tripeptide Schiff base complexes [CuL]? with bivalent metal ion M2+, where H3L=N-salicylideneglycylglycylglycine. Single crystal X-ray diffraction experiments indicate that the structures both 1 and 2, are made up of centrosymmetric trinuclear units with the M atom lying on an

Wen-Long Liu; Yang Zou; Chun-Lin Ni; Yi-Zhi Li; Qing-Jin Meng

2005-01-01

191

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

192

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

193

Heterobinuclear copper(II)–nickel(II) complexes of macrocyclic oxamide with diamines and tetraazacyclam as blocking ligands: synthesis, crystal structure and magnetic properties  

Microsoft Academic Search

Three novel oxamido-bridged heterobinuclear copper(II)–nickel(II) complexes derived from macrocylic oxamido compound with diamines and tetraazacyclam as blocking ligands were synthesized and characterized by IR, ESR and electronic spectra. Their formula is [Cu(L)Ni(en)2](ClO4)2·0.5C2H5OH·H2O (1), [Cu(L)Ni(tmd)2](ClO4)2·4H2O (2) and [Cu(L)Ni(rac-cth)](ClO4)2·CH3OH (3), where L=1,4,8,11-tetraazacyclotradecanne-2,3-dione, en=1,2-diaminoethande, tmd=1,3-diaminopropane and rac-cth is rac-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane. The crystal structures of the three complexes have been determined. The structures consist of

Jin-Kui Tang; Shu Feng Si; En-Qing Gao; Dai-Zheng Liao; Zong-Hui Jiang; Shi-Ping Yan

2002-01-01

194

Synthesis, structures and magnetic properties of copper (II) and cobalt (II) complexes containing pyridyl-substituted nitronyl nitroxide and 3,5-dinitrobenzoate  

Microsoft Academic Search

Four new metal-radical complexes - [Cu(NIT3Py)2(DTB)2] 1, [Co(NIT3Py)2(DTB)2(CH3OH)2] 2, [Cu(NIT4Py)2(DTB)2(H2O)2] 3, [Co(NIT4Py)2(DTB)2(H2O)2] 4, (NIT3Py=2-(3?-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide], NIT4Py=2-(4?-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide], DTB=3,5-dinitrobenzoic anion) have been synthesized by using transition metal ions, nitronyl nitroxide radicals as spin carriers, and incorporating 3,5-dinitrobenzoic acid (DTB) as a coligand.The structures of 1–4 were determined by X-ray single-crystal analyses. Complex 1 has a square planar geometry, where the Cu(II) ion is

Chen-Xi Zhang; Yu-Ying Zhang; Ya-Qiu Sun

2010-01-01

195

Synthesis, crystal structure and magnetic properties of quasi-linear tetranuclear copper(II) Schiff base complexes formed by covalent linkage of asymmetrically dibridged dicopper(II) units  

Microsoft Academic Search

Alkoxo-phenoxo bridged tetranuclear copper(II) complexes [Cu4L2(O2CC6H4-p-OH)2] (1) and [Cu4L2(O2CC6H4-o-OH)2] (2) containing pentadentate Schiff base ligand N,N?-(2-hydroxypropane-1,3-diyl)bis(salicylaldimine) (H3L) are prepared and structurally characterized. Crystal structures of the complexes show the covalent linkage between two {Cu2L(O2CR)}(R = C6H4-p-OH, C6H4-o-OH) units through the phenoxo atoms of the Schiff base ligand showing axial\\/equatorial bonding modes. The Cu(1)–O(2)–Cu(2) alkoxo bridge angle is 131° in 1

Arindam Mukherjee; Manas K. Saha; Indranil Rudra; Suryanarayanasastry Ramasesha; Munirathinam Nethaji; Akhil R. Chakravarty

2004-01-01

196

Facile synthesis of Cu(II) complexes of monocondensed N,N,N donor Schiff base ligands: Crystal structure, spectroscopic and magnetic properties  

Microsoft Academic Search

Four new copper(II) complexes, [(CuL1N3)2](ClO4)2 (1), [(CuL2N3)2](ClO4)2 (2), [CuL3(N3)(ClO4)]n (3) and [CuL4(?-1,1-N3)(?-1,3-N3)(ClO4)]n (4) where L1=N1-pyridin-2-yl-methylene-propane-1,3-diamine, L2=N1-(1-pyridin-2-yl-ethylidene)propane-1,3-diamine, L3=N1-(1-pyridin-2-yl-ethylidene)ethane-1,2-diamine and L4=N1-(1-pyridin-2-yl-ethylidene)propane-1,2-diamine are four tridentate N,N,N donor Schiff base ligands, have been derived and structurally characterized by X-ray crystallography. Compounds 1 and 2 consist of double basal–apical end-on (EO) azide bridged dinuclear CuII complexes with square-pyramidal geometry. In complex 3 the square planar

Shouvik Chattopadhyay; Mau Sinha Ray; Michael G. B. Drew; Albert Figuerola; Carmen Diaz; Ashutosh Ghosh

2006-01-01

197

Luminescence and magnetic properties of mixed-ligand europium trifluoroacetates  

NASA Astrophysics Data System (ADS)

The luminescence and magnetic properties of mixed-ligand europium trifluoroacetates with nitrogen- and phosphorus-containing neutral ligands [Eu(TFA)3 · 3H2O]2 and Eu(TFA)3 · 2D · nH2O were studied (here TFA is the trifluoroacetic acid anion, and D is Phen (1,10-phenanthroline), n = 1; DMF (dimethylformamide), n = 1; or TPPO (triphenylphosphine oxide), n = 3). The molar magnetic susceptibility increased in the series of complex compounds Eu(TFA)3 · 2Phen · H2O < [Eu(TFA)3 · 3H2O]2 < Eu(TFA)3 · 2DMF · H2O < Eu(TFA)3 · 2TPPO · 3H2O. Correlations were found between the luminescent and magnetic characteristics of the complex compounds.

Kalinovskaya, I. V.; Tkachenko, I. A.; Mirochnik, A. G.; Karasev, V. E.; Kavun, V. Ya.

2010-08-01

198

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

199

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

PubMed Central

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.

2014-01-01

200

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

201

Synthesis, structure and magnetic properties of the pentanuclear complex [Fe 2 (CN) 12 Ni 3 (L) 6 ]·27H 2 O, where L is nitronyl nitroxide  

Microsoft Academic Search

We succeeded in synthesizing a new high-spin complex [Fe2(CN)12Ni3(L)6]·27H2O, where L is stable nitroxide 2-(imidazol-4-yl)-4,4,5,5-tetramethyl-2-imidazoline-3-oxide-1-oxyl. According to X-ray diffraction\\u000a data, the metal core of the pentanuclear [Fe2(CN)12Ni3(L)6] molecule is a trigonal bipyramid with Fe atoms occupying the axial positions and linked via CN bridges to {NiL2} fragments laying in the equatorial plane. A peculiarity of this coordination compound is a

H. Higashikawa; K. Inoue; K. Yu. Maryunina; G. V. Romanenko; A. S. Bogomyakov; O. V. Kuznetsova; E. Yu. Fursova; V. I. Ovcharenko

2009-01-01

202

Two novel oxamido-bridge dinuclear copper(II) complexes containing four spin carriers involving the nitroxide radical ligand: synthesis, crystal structure and magnetic properties  

Microsoft Academic Search

The combined use of nitroxide free radicals as terminal ligands and precursor [Cu2(oxpn)]2+ anions has led to the preparation of two novel oxamido-bridged dinuclear copper(II) complexes containing nitronyl nitroxide Cu2(oxpn)(NIToBA)2(1) or imino nitroxide [Cu2(oxpn)(IMpPy)2](ClO4)2 · 2H2O (2). X-ray crystallography shows that both (1) and (2) have like as coordination modes where the oxamido group as a trans-form bridged ligand, combine

Qi-Hua Zhao; Xiao-Feng Wang; Rui-Bin Fang

2005-01-01

203

Synthesis, crystal structures and magnetic properties of new oxalato- and phenolato-bridged binuclear copper(II) complexes with Schiff-base ligands  

Microsoft Academic Search

Two binuclear complexes of copper(II), [(Hfsaaep)Cu(?-C2O4)Cu(Hfsaaep)] (1) and [Cu2(Hfsadmpn)2(H2O)2](ClO4)2 (2), have been synthesized by using Schiff-base ligands derived from 3-formyl-salicylic acid: 3-[N-2-(pyridylethyl)formimidoyl]salicylic acid (H2fsaaep) and 3-N-[N?,N?-dimethylaminopropyl)formimidoyl]salicylic acid (H2fsadmpn). The crystal structures of compounds 1 and 2 have been solved. That of compound 1 consists of neutral binuclear entities with copper atoms bridged by one oxalato group, which connect axial–equatorial positions

Floriana Tuna; Gabriel Ionut Pascu; Jean-Pascal Sutter; Marius Andruh; Stéphane Golhen; Joseph Guillevic; Hans Pritzkow

2003-01-01

204

Three-dimensional magnetic properties of soft magnetic composite materials  

NASA Astrophysics Data System (ADS)

A three-dimensional (3-D) magnetic property measurement system, which can control the three components of the magnetic flux density B vector and measure the magnetic field strength H vector in a cubic sample of soft magnetic material, has been developed and calibrated. This paper studies the relationship between the B and H loci in 3-D space, and the power losses features of a soft magnetic composite when the B loci are controlled to be circles with increasing magnitudes and ellipses evolving from a straight line to circle in three orthogonal planes. It is found that the B and H loci lie in the same magnetization plane, but the H loci and power losses strongly depend on the orientation, position, and process of magnetization. On the other hand, the H vector evolves into a unique locus, and the power loss approaches a unique value, respectively, when the B vector evolves into the round locus with the same magnitude from either a series of circles or ellipses.

Lin, Z. W.; Zhu, J. G.

2007-05-01

205

Correlation Between Solar Flare Productivity and Photospheric Magnetic Field Properties  

Microsoft Academic Search

From a large number of SOHO\\/MDI longitudinal magnetograms, three physical measures including the maximum horizontal gradient,\\u000a the length of the neutral line, and the number of singular points are computed. These measures are used to describe photospheric\\u000a magnetic field properties including nonpotentiality and complexity, which is believed to be closely related to solar flares.\\u000a Our statistical results demonstrate that solar

Yanmei Cui; Rong Li; Liyun Zhang; Yulin He; Huaning Wang

2006-01-01

206

A series of trinuclear sandwich-like cyanide-bridged iron(III)-manganese(II) complexes: synthesis, crystal structures, and magnetic properties  

Microsoft Academic Search

Four pyridinecarboxamide iron dicyanide building blocks and one Mn(III) compound have been employed to assemble cyanide-bridged\\u000a heterometallic complexes, resulting in a series of trinuclear cyanide-bridged FeIII–MnII complexes: {[Mn(DMF)2 (MeOH)2][Fe(bpb)(CN)2]2}·2DMF (1), {[Mn(MeOH)4][Fe(bpmb)(CN)2]2}·2MeOH·2H2O (2), {[Mn(MeOH)4][Fe(bpdmb)(CN)2]2}·2MeOH·2H2O (3) and {[Mn(MeOH)4][Fe(bpClb)(CN)2]2}·4MeOH (4) (bpb2? = 1,2-bis(pyridine-2-carboxamido)benzenate, bpmb2? = 1,2-bis(pyridine-2-carboxamido)-4-methyl-benzenate, bpdmb2? = 1,2-bis(pyridine-2-carboxamido)-4,5-dimethyl-benzenate, bpClb2? = 1,2-bis(pyridine-2-carboxamido)-4-chloro-benzenate). Single-crystal X-ray diffraction analysis shows their similar sandwich-like\\u000a structures, in which the two cyanide-containing building blocks act as monodentate

Daopeng Zhang; Lifang Zhang; Xia Chen; Zhonghai Ni

2011-01-01

207

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

208

Progress in magnetic couple system of nitroxidemetal complexes  

Microsoft Academic Search

Metal-radical method is an effective approach to synthesizing magnetic molecular materials. With the development in decades,\\u000a the study of nitroxide-metal complexes has made great progress in model, theoretical treatment and design of molecules. Several\\u000a mechanisms of the metal-radical magnetic coupling are discussed. Molecular magnetic project of nitroxide-metal mmplutes has\\u000a made fruitful achievements, but crystal magnetic project is difficult to be

Baiwang Sun; Daizheng Liao; Zonghui Jiang; Genglin Wang

1998-01-01

209

Measurement of dielectric and magnetic properties of soil  

SciTech Connect

The possibility of subsurface imaging using SAR technology has generated a considerable amount of interest in recent years. One requirement for the successful development of a subsurface imagin system is an understanding of how the soil affects the signal. In response to a need for an electromagnetic characterization of the soil properties, the Radar/Antenna department has developed a measurement system which determines the soils complex electric permittivity and magnetic permeability at UHF frequencies. The one way loss in dB is also calculated using the measured values. There are many reports of measurements of the electric properties of soil in the literature. However, most of these are primarily concerned with measuring only a real dielectric constant. Because some soils have ferromagnetic constituents it is desirable to measure both the electric and magnetic properties of the soil.

Patitz, W.E.; Brock, B.C.; Powell, E.G.

1995-11-01

210

Fundamental Magnetic Properties from Pure Synthetic Greigite  

NASA Astrophysics Data System (ADS)

Greigite (Fe3S4), an authigenic mineral that forms in sulfate-reducing environments, has been widely identified in marine and lake sediments. It is often the main magnetic carrier in some settings, and can therefore be significant in paleomagnetic and environmental magnetic studies. However, unlike its iron oxide counterpart, magnetite (Fe3O4), the fundamental magnetic characteristics of greigite are still poorly understood, which is partially due to the metastability of greigite and the difficulty in obtaining high quality greigite samples. We have successfully synthesized pure greigite samples with good crystallinity using a new hydrothermal method. Our detailed low- and high-temperature magnetic measurements document the previously poorly known magnetic properties of greigite, including the first accurate measurement of its saturation magnetization. We have for the first time unambiguously determined the magnetic structure of greigite by combined neutron powder diffraction and neutron polarization analysis. Low temperature (LT) neutron diffraction spectra reveal the temperature dependence of sublattice magnetizations. The pure synthetic greigite samples are large enough to show pseudo-single-domain (PSD) and multi-domain (MD) behavior. LT cycling (LTC) of saturation isothermal remanent magnetization (SIRM) measurements indicate a continuous demagnetization of remanence during cooling. Preservation of the main features of first-order reversal curve distributions at LT, coupled with LT SIRM warming curves, rule out the presence of substantial superparamagnetic behavior in the studied samples. No LT magnetic transition has been detected; however, a local coercivity minimum is observed at around 130 K. These fundamental studies provide new constraints on the magnetic behaviour of greigite.

Chang, L.; Roberts, A. P.; Muxworthy, A. R.; Tang, Y.; Chen, Q.; Rainford, B. D.

2007-12-01

211

Thermophysical and Magnetic Properties of Carbon Beads Containing Cobalt Nanocrystallites  

NASA Astrophysics Data System (ADS)

Magnetic Co-beads were fabricated in the course of a three-step procedure comprising preparation of a metal-acrylamide complex, followed by frontal polymerization and finally pyrolysis of the polymer. The composites obtained were composed of cobalt nanocrystallites stabilized in a carbon matrix built of disordered graphite. The crystallite size, material morphology, fraction of the magnetic component, and thus the magnetic properties can be tailored by a proper choice of the processing variables. The samples were subjected to an alternating magnetic field of different strengths ( H = 0 to 5 kA · m-1) at a frequency of f = 500 kHz. From the calorimetric measurements, we concluded that the relaxation processes dominate in the heat generation mechanism for the beads pyrolyzed at 773 K. For the beads pyrolyzed at 1073 K, significant values of magnetic properties, such as the coercive force and remanence give substantial contribution to the energy losses for hysteresis. The specific absorption coefficient ( SAR) related to the cobalt mass unit for the 1073 K pyrolyzed beads {({SAR} = 1340 W \\cdot g^{-1 }_cobalt)} is in very good conformity with the results obtained by other authors. The effective density power loss, caused by eddy currents, can be neglected for heating processes applied in magnetic hyperthermia. The Co-beads can potentially be applied for hyperthermia treatment.

Izydorzak, M.; Skumiel, A.; Leonowicz, M.; Kaczmarek-Klinowska, M.; Pomogailo, A. D.; Dzhardimalieva, G. I.

2012-04-01

212

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

213

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

214

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

215

Magnetic Properties of Three Impact Structures in Canada  

NASA Astrophysics Data System (ADS)

Magnetic anomaly lows associated with the West Hawk Lake (Manitoba), Deep Bay (Saskatchewan) and Clearwater Lakes (Quebec) impact structures, are variable in lateral extent and intensity, a characteristic shared with most impact structures [1]. Drill core from the centres of these structures provides a unique opportunity to ground truth the causes of the reduction in magnetic field intensity in impact structures. Magnetic susceptibility and remanent magnetization levels have been found to be well below regional levels in melt rocks, impact breccias, fractured/shocked basement rocks in the central uplifts, and post-impact sediments. Deep Bay, formed in Pre-Cambrian paragneisses, is a complex crater with a submerged central uplift. It has been extensively infilled with non-magnetic black shales of Cretaceous age [2]. An airborne magnetic low of about 100 nT is associated with the Deep Bay structure. Below the shales and along the rim of the structure are highly brecciated country rocks with variable amounts of very fine rock flour. Susceptibility and remanent magnetization are both weak due to extensive alteration in the brecciated rocks. Alteration of the brecciated rocks, and the effect of several hundred meters of non-magnetic sedimentary infill, both contribute to the magnetic low. West Hawk Lake, a simple crater, was excavated in metavolcanic and metasedimentary rocks of the Superior Province [3], and has a ground magnetic low of about 250 nT. As with Deep Bay, West Hawk Lake has been infilled with dominantly non-magnetic sediments. Brecciation and alteration are extensive, with breccia derived from greenschist-facies meta-andesite displaying slightly higher susceptibilities and remanent magnetizations than breccia derived from the more felsic metasediments. Brecciation has effectively randomized magnetization vectors, and subsequent alteration resulted in the destruction of magnetic phases. These two factors contribute to the magnetic low over this structure. The Clearwater Lakes impact structures are two complex craters formed in Archean retrograde granulite facies rocks [4]. Clearwater West, at 36 km diameter, has an annular ring of islands and a shallowly submerged central uplift. Clearwater East, at 26 km diameter, has a more deeply submerged central uplift. The structures are characterised by highly oxidized melt rock and melt- breccia lenses exposed at the surface. Shocked crystalline basement rocks and minor amounts of breccia and melt rock occur in the central uplifts [5]. Despite relatively little alteration at depth, these rocks exhibit both susceptibilities and remanent magnetizations well below the regionally high values. The Clearwater rocks also contain a thermoremanent reversed magnetization, acquired at the time of impact, and characteristic of the Permo-Carboniferous Reversed Polarity Superchron. The magnetization is carried by titanomagnetite in Clearwater West, and both magnetite and pyrrhotite in Clearwater East. This reversed magnetization contributes to the magnetic low, but cannot account for all of it. The intense airborne magnetic low (> 500 nT) requires a significant contribution from the shocked basement at depth, produced by either alteration of magnetic phases along fractures, or reduction in magnetic properties by lower shock levels away from the point of impact [6]. References: [1] Pilkington M. and Grieve R. A. F. (1992) Rev. Geophys., 30, 161-181. [2] Innes M. J. S. et al. (1964) Publ. Dom. Obs. Ottawa, 31, 19-52. [3] Halliday I. and Griffin A. A. (1967) J. Roy. Astron. Soc. Can., 61, 1-8. [4] Simonds C. H. et al. (1978) LPS IX, 2633-2658. [5] Hische R. (1994) Unpublished Ph.D. thesis, Munster. [6] Pohl J. (1994) 3rd Intl. Wkshp., ESF Network Impact Cratering and Evol. of Planet Earth, Shockwave Behavior in Nature and Expt., Progr. Abstr., 51.

Scott, R. G.; Pilkington, M.; Tanczyk, E. I.; Grieve, R. A. F.

1995-09-01

216

Syntheses, crystal structures, and magnetic properties of two cyclic dimer M 2L 2 complexes constructed from a new nitronyl nitroxide ligand and M(hfac) 2 (M = Cu 2+, Mn 2+)  

Microsoft Academic Search

Two new binuclear radical complexes derived from a new long nitronyl nitroxide ligand, 2-[4-(5-pyrimidyl)phenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (4-NITPhPyrim), and M(hfac)2 (M2+=Cu2+, Mn2+; hfac?=hexafluoroacetylacetonato), [Cu(hfac)2(4-NITPhPyrim)]2·4H2O (1) and [Mn(hfac)2(4-NITPhPyrim)]2·4H2O (2), were synthesized as well as characterized structurally and magnetically. X-ray analysis indicates that 1 and 2 are rectangle-like centrosymmetric dimer M2L2 complexes. Magnetic measurements indicate that there are two types of magnetic exchanges in 1:

Jian-Ying Zhang; Cai-Ming Liu; De-Qing Zhang; Song Gao; Dao-Ben Zhu

2007-01-01

217

Magnetic and electronic properties of ?-graphyne nanoribbons.  

PubMed

Based on the first-principles calculations, we investigate the magnetic and electronic properties of ?-graphyne nanoribbons (NRs). We show that all the armchair ?-graphyne NRs are nonmagnetic semiconductors with band gaps as a function of ribbon widths. The zigzag ?-graphyne NRs are found to have magnetic semiconducting ground state with ferromagnetic ordering at each edge and opposite spin orientation between the two edges. Under the application of transverse electric field, we further predict the existence of half-metallicity in the zigzag NRs which strongly depends on the width of the ribbon. PMID:22755594

Yue, Qu; Chang, Shengli; Kang, Jun; Tan, Jichun; Qin, Shiqiao; Li, Jingbo

2012-06-28

218

Magnetoelectric Properties of Magnetic Tunneling Junctions  

NASA Astrophysics Data System (ADS)

Magnetic tunneling junctions(MTJ's) consisting of two ferromagnetic layers separated by a thin insulating barrier show large tunnel magnetoresistive effects when the magnetizations of the ferromagnetic layers change their relative orientation from parallel to antiparallel in an applied field. Tunnel magneto resistance (TMR) is defined as the relative difference in tunnel resistance between parallel and antiparallel oriented magnetizations of electrodes. The larger this TMR effect, the more sensitive the MTJ will be as magnetic read out device. This result has attracted considerable attention due to its potential applicability in digital storage industry and as magnetic field sensors. In this study we present our experimental evidence of magnetoelectric properties of MTJ's. Co(30nm)/Al2O3(1.5nm)/NiFe(30nm) tunnel junctions were fabricated on a Si wafer using DC plasma sputtering deposition with shadow mask technique. We used the RF plasma in-situ oxidation method to oxidize the thin Al layer. We measured the magnetoresistance(MR) ratio of these junctions at room temperature by applying magnetic field in plane and perpendicular to the direction of current. We could obtain MR values of 8% at room temperature and the resistances of these junctions were found to be 500O to 50 KO range. To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.NWS07.C1.2

Chava, Shilpa; Dhakal, Avishesh; Jiang Yeh, Wei

2007-05-01

219

Magnetic resonance relaxation properties of superparamagnetic particles.  

PubMed

Nanometric crystals of maghemite are known to exhibit superparamagnetism. Because of the significance of their magnetic moment, maghemite nanoparticles are exceptional contrast agents and are used for magnetic resonance imaging (of the liver, spleen, lymph nodes), for magnetic resonance angiography and for molecular and cellular imaging. The relaxivity of these agents depends on their size, saturation magnetization and magnetic field and also on their degree of clustering. There are different types of maghemite particles whose relaxation characteristics are suited to a specific MRI application. The relaxation induced by maghemite particles is caused by the diffusion of water protons in the inhomogeneous field surrounding the particles. This is well described by a theoretical model that takes magnetite crystal anisotropy and Néel relaxation into account. Another type of superparamagnetic compound is ferritin, the iron-storing protein: it contains a superparamagnetic ferrihydrite core. Even if the resulting magnetic moment of ferritin is far smaller than for magnetite nanoparticles, its massive presence in different organs darkens T(2)-weighted MR images, allowing the noninvasive estimation of iron content, thanks to MRI. The relaxation induced by ferritin in aqueous solutions has been demonstrated to be caused by the exchange of protons between bulk water protons and the surface of the ferrihydrite crystal. However, in vivo, the relaxation properties of ferritin are still unexplained, probably because of protein clustering. PMID:20049798

Gossuin, Yves; Gillis, Pierre; Hocq, Aline; Vuong, Quoc L; Roch, Alain

2009-01-01

220

Relationships Between Magnetic Properties and Weathering Indices of Basaltic Rocks  

NASA Astrophysics Data System (ADS)

Performance of geophysical sensors is often hampered by soils and regolith with significant levels of magnetic susceptibility and viscosity, primarily dependent on the amount and form of ferrimagnetic iron oxide minerals present. In order to develop predictive models for the occurrence of such conditions, it is crucial to understand how the magnetic signal evolves during weathering from fresh rock to soil material. Rock weathering leads to destruction of primary minerals, formation of secondary minerals, and concomitant changes in magnetic properties and major-, minor-, and trace-element geochemistry. Previous work has examined relationships between magnetic properties (e.g., magnetic susceptibility) and single-element proxies for overall sample weathering state. In this contribution we study the relationships between bulk geochemical and magnetic characteristics of weathered basaltic rock, and regolith and soils with basaltic parent material. Four samples collected from a corestone formed by spheroidal weathering on the Kohala Peninsula on the Big Island of Hawaii represent the earliest stages of weathering; a series of samples from regolith to the B-horizon for a soil on Kaho'olawe Island represent later weathering stages. Our analysis includes X-Ray Fluorescence Spectroscopy of whole-sample geochemistry and magnetic measurements for a range of temperatures and frequencies. The extent of chemical weathering is assessed by use of a number of common (but Fe-free) major-element weathering indices. Progressive spheroidal weathering involves centripetal migration of a weathering front from joints and fractures into the interior of the joint blocks. As the weathering front passes through a volume of material, fresh or slightly weathered rock is transformed to a primary-mineral-depleted, clay-rich shell. The exfoliated shells farthest from the corestone were the first weathered; shells successively closer to the corestone were more recently transformed. In the Kohala corestone-shell complex, some chemical-weathering indices vary monotonically with total Fe (as Fe2O3), whereas other chemical-weathering indices vary monotonically with magnetic susceptibility. Thus, some Fe-free major-element chemical-weathering indices seem to scale more systematically with soil magnetic properties than others. For more strongly weathered soils from Kaho'olawe, there is a weak relationship between magnetic properties and total Fe. We hope that through the use of Fe-free major-element weathering indices an improved relationship can be developed. Such an improved correlation would benefit phenomenological understanding of geophysical sensor performance in areas with basaltic substrate.

van Dam, R. L.; Velbel, M. A.

2009-05-01

221

Focused-ion-beam induced interfacial intermixing of magnetic bilayers for nanoscale control of magnetic properties.  

PubMed

Modification of the magnetic properties in a thin-film ferromagnetic/non-magnetic bilayer system by low-dose focused ion-beam (FIB) induced intermixing is demonstrated. The highly localized capability of FIB may be used to locally control magnetic behaviour at the nanoscale. The magnetic, electronic and structural properties of NiFe/Au bilayers were investigated as a function of the interfacial structure that was actively modified using focused Ga(+) ion irradiation. Experimental work used MOKE, SQUID, XMCD as well as magnetoresistance measurements to determine the magnetic behavior and grazing incidence x-ray reflectivity to elucidate the interfacial structure. Interfacial intermixing, induced by low-dose irradiation, is shown to lead to complex changes in the magnetic behavior that are associated with monotonic structural evolution of the interface. This behavior may be explained by changes in the local atomic environment within the interface region resulting in a combination of processes including the loss of moment on Ni and Fe, an induced moment on Au and modifications to the spin-orbit coupling between Au and NiFe. PMID:24833038

Burn, D M; Hase, T P A; Atkinson, D

2014-06-11

222

Focused-ion-beam induced interfacial intermixing of magnetic bilayers for nanoscale control of magnetic properties  

NASA Astrophysics Data System (ADS)

Modification of the magnetic properties in a thin-film ferromagnetic/non-magnetic bilayer system by low-dose focused ion-beam (FIB) induced intermixing is demonstrated. The highly localized capability of FIB may be used to locally control magnetic behaviour at the nanoscale. The magnetic, electronic and structural properties of NiFe/Au bilayers were investigated as a function of the interfacial structure that was actively modified using focused Ga+ ion irradiation. Experimental work used MOKE, SQUID, XMCD as well as magnetoresistance measurements to determine the magnetic behavior and grazing incidence x-ray reflectivity to elucidate the interfacial structure. Interfacial intermixing, induced by low-dose irradiation, is shown to lead to complex changes in the magnetic behavior that are associated with monotonic structural evolution of the interface. This behavior may be explained by changes in the local atomic environment within the interface region resulting in a combination of processes including the loss of moment on Ni and Fe, an induced moment on Au and modifications to the spin-orbit coupling between Au and NiFe.

Burn, D. M.; Hase, T. P. A.; Atkinson, D.

2014-06-01

223

Slow magnetic relaxation in tris(diphosphanylamido) and tetra(phosphanoamido) dysprosium complexes.  

PubMed

Two homoleptic phosphanylamido dysprosium complexes [Li(THF)4][(Ph2PNPh)4Dy] and [Dy{N(PPh2)2}3] have been synthesized. Both have a highly symmetric arrangement of the ligand which is only slightly broken in the solid state by steric and packing effects as a result of the weak coordination of phosphorus atoms to the metal centre. Magnetic properties of these two compounds are similar with both showing slow magnetic relaxation. PMID:23828221

Völcker, Franziska; Lan, Yanhua; Powell, Annie K; Roesky, Peter W

2013-08-28

224

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

225

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

226

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

227

Magnetic properties of artificially synthesized ferritins  

NASA Astrophysics Data System (ADS)

Human ferritin homopolymers with H or L subunits (rHF and rLF) were genetically engineered in E coli. Apoferritins were then reconstituted with 2000 Fe atoms. A big difference was observed in the rates of iron uptake, whereas the mean core size was similar in rHF and rLF. Magnetization of the recombinant human ferritins were measured as functions of temperature and field. The blocking temperature TB(H) at low fields is considerably higher in rLF than in rHF. From the fit of M(H) data to a modified Langevin function: M(H)=M0L(?pH/kBT)+?aH, the effective magnetic moment ?p is found to be much larger in rLF than in rHF. Experimental data demonstrate that the magnetic properties, in particular, the uncompensated spins of ferritin core are related to the biomineralization process in ferritins.

Kim, B. J.; Lee, H. I.; Cho, S.-B.; Yoon, S.; Suh, B. J.; Jang, Z. H.; St. Pierre, T. G.; Kim, S.-W.; Kim, K.-S.

2005-05-01

228

Physical Properties of Complex C Halo Clouds  

NASA Astrophysics Data System (ADS)

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-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 101.1-104.8 M sun, sizes of 101.2-102.6 pc, and have a median volume density and pressure of 0.065 cm-3 and (P/k) = 580 K cm-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 × 10-4 cm-3, which given a constant distance of 10 kpc is at a z-height of ~3 kpc. Using the same argument for the Stream results in a median halo density of 8.4 × 10-5 (60 kpc/d) cm-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.; Putman, M. E.; Heitsch, F.; Stanimirovi?, S.; Peek, J. E. G.; Clark, S. E.

2011-02-01

229

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

230

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

231

Molecular Magnets Based on Homometallic Hexanuclear Lanthanide(III) Complexes.  

PubMed

The reaction of lanthanide(III) chloride salts (Gd(III), Dy(III), Tb(III), and Ho(III)) with the hetero donor chelating ligand N'-(2-hydroxy-3-methoxybenzylidene)-6-(hydroxymethyl)picolinohydrazide (LH3) in the presence of triethylamine afforded the hexanuclear Ln(III) complexes [{Ln6(L)2(LH)2}(?3-OH)4][MeOH]p[H2O]q[Cl]4·xH2O·yCH3OH (1, Ln = Gd(III), p = 4, q = 4, x = 8, y = 2; 2, Ln = Dy(III), p = 2, q = 6, x = 8, y = 4; 3, Ln = Tb(III), p = 2, q = 6, x = 10, y = 4; 4, Ln = Ho(III), p = 2, q = 6, x = 10, y = 2). X-ray diffraction studies revealed that these compounds possess a hexanuclear [Ln6(OH)4](14+) core consisting of four fused [Ln3(OH)](8+) subunits. Both static (dc) and dynamic (ac) magnetic properties of 1-4 have been studied. Single-molecule magnetic behavior has been observed in compound 2 with an effective energy barrier and relaxation time pre-exponential parameters of ?/kB = 46.2 K and ?0 = 2.85 × 10(-7) s, respectively. PMID:24766539

Das, Sourav; Hossain, Sakiat; Dey, Atanu; Biswas, Sourav; Sutter, Jean-Pascal; Chandrasekhar, Vadapalli

2014-05-19

232

Magnetic Compton scattering: A reliable probe to investigate magnetic properties  

NASA Astrophysics Data System (ADS)

Magnetic Compton scattering (MCS) is an ideal technique for the study of magnetic properties of ferro/ferrimagnetic materials because this method reveals the spin-polarized electron momentum density and yields the absolute and site dependent spin moments. The quantity measured in the MCS, so called magnetic Compton profile, is defined as the difference in the one-dimensional projection of the spin-polarized electron momentum density for majority and minority spin bands. In MCS, the Doppler broadening of the scattered radiation provides information on the correlation between the spin moment and the spin-polarized electron states of the valence electrons. It can also distinguish the spin polarization of itinerant electrons, because their momentum is narrow around the center of the profile. In this paper, temperature and field dependent spin momentum densities in Zn doped Ni ferrite namely, Ni1-xZnxFe2O4(x = 0.0,0.1,0.2), hole doped manganites like La0.7Ca0.3Mn1-xAlxO3(x = 0,0.02and0.06) and half Heusler alloys Cu1-xNixMnSb(x = 0.17,0.22) are reviewed. The decomposition of profiles in terms of site specific magnetic moments and their role in the formation of total spin moment is also discussed.

Ahuja, B. L.

2013-02-01

233

Magnetic Polymer Nanocomposites with Tunable Microwave Properties  

Microsoft Academic Search

Due to the multifunctionality, polymer nanocomposites (PNCs) have potential applications for electromagnetic interference shielding, tunable electromagnetic devices and flexible electronics. We report on synthesis, magnetic and RF characterization of polymer films loaded with varying concentrations of Fe3O4 and CoFe2O4 nanoparticles. The nanoparticles (5 ± 1 nm) were synthesized by chemical co-precipitation. Structural properties were characterized by XRD and TEM. Nanoparticles

K. Stojak; S. Pal; H. Srikanth; S. Skidmore; C. Morales; J. Dewdney; J. Wang; T. Weller

2010-01-01

234

Magnetic properties of arrays of electrodeposited nanowires  

Microsoft Academic Search

The fabrication and magnetic properties of arrays of short nanowires are reviewed. The arrays consist of electrodeposited ferromagnetic cylinders with aspect ratios of up to 3 and diameters of 57–180nm. Their hysteresis loops are characterized and their remanent states are related to the predictions of a three-dimensional micromagnetic model, which shows a transition from a single-domain ‘flower’ state to a

C. A. Ross; M. Hwang; M. Shima; Henry I. Smith; M. Farhoud; T. A Savas; W. Schwarzacher; J. Parrochon; W. Escoffier; H. Neal Bertram; F. B Humphrey; M. Redjdal

2002-01-01

235

Magnetic Properties of Photospheric Regions with Very Low Magnetic Flux  

NASA Astrophysics Data System (ADS)

The magnetic properties of the quiet Sun are investigated using a novel inversion code, FATIMA, based on the Principal Component Analysis of the observed Stokes profiles. The stability and relatively low noise sensitivity of this inversion procedure allows for the systematic inversion of large data sets with a very weak polarization signal. Its application to quiet-Sun observations of network and internetwork regions reveals that a significant fraction of the quiet-Sun contains kilogauss fields (usually with very small filling factors) and confirms that the pixels with weak polarization account for most of the magnetic flux. Mixed polarities in the resolution element are also found to occur more likely as the polarization weakens.

Socas-Navarro, H.; Sánchez Almeida, J.

2002-02-01

236

Monte Carlo study of nanowire magnetic properties  

NASA Astrophysics Data System (ADS)

In this work, we use Monte Carlo simulations to study the magnetic properties of a nanowire system based on a honeycomb lattice, in the absence as well as in the presence of both an external magnetic field and crystal field. The system is formed with NL layers having spins that can take the values ? = ±1/2 and S = ±1,0. The blocking temperature is deduced, for each spin configuration, depending on the crystal field ?. The effect of the exchange interaction coupling Jp between the spin configurations ? and S is studied for different values of temperature at fixed crystal field. The established ground-state phase diagram, in the plane (Jp, ?), shows that the only stable configurations are: (1/2, 0), (1/2, +1), and (1/2, -1). The thermal magnetization and susceptibility are investigated for the two spin configurations, in the absence as well as in the presence of a crystal field. Finally, we establish the hysteresis cycle for different temperature values, showing that there is almost no remaining magnetization in the absence of the external magnetic field, and that the studied system exhibits a super-paramagnetic behavior.

Masrour, R.; Bahmad, L.; Benyoussef, A.

2013-05-01

237

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

238

Cyclic metal–radical complexes based on 2-[4-(1-imidazole)phenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide: Syntheses, crystal structures and magnetic properties  

Microsoft Academic Search

Using new nitronyl nitroxide radical ligand 2-[4-(1-imidazole)phenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (NITPhIm), three new complexes [M(hfac)2(NITPhIm)]2 (M=Cu(II) 1, Mn(II) 2, Co(II) 3; hfac=hexafluoroacetylacetonate) have been prepared. Three complexes possess cyclic dimer structure in which each NITPhIm radical links two different metal ions through the oxygen of nitroxide group and the nitrogen of imidazole. The magnetic studies show the copper(II) ion interacts ferromagnetically with the

Rui-Na Liu; Li-Cun Li; Xiao-Yan Xing; Dai-Zheng Liao

2009-01-01

239

One trinuclear copper(II) complex derived from a new Schiff base ligand based on the dianion of 4-chloro-6-(hydroxymethyl)-2-((3-aminopropylimino)methyl)-phenol: Synthesis, structure, spectroscopic and magnetic properties  

Microsoft Academic Search

A linear trinuclear copper(II) complex (1), prepared from a new Schiff base ligand, namely the dianion of 4-chloro-6-(hydroxymethyl)-2-((3-aminopropylimino)methyl)-phenol, was synthesized and characterized in this paper. The X-ray structural study reveals that the geometry of the central Cu2 ion is elongated octahedral and that of the two side Cu(II) ions is distorted square pyramidal. The magnetic susceptibility measurements from 2 to

Juechao Jiang; Zhaolian Chu; Wei Huang

2009-01-01

240

Interaction of Phase Transformation and Magnetic Properties of Heusler Alloys: A Density Functional Theory Study  

NASA Astrophysics Data System (ADS)

The structural, electronic, and magnetic properties of functional Ni-Mn- Z ( Z = Ga, In, Sn, and Sb) Heusler alloys are studied by first-principles and Monte Carlo tools. The ab initio calculations give a basic understanding of the underlying physics that are associated with the complex magnetic behavior arising from the competition of ferromagnetic and antiferromagnetic interactions with increasing chemical disorder in the super cell. This complex magnetic ordering is the driving mechanism of structural transformations. It also essentially determines the multifunctional properties of the Heusler alloys such as magnetic shape-memory and magnetocaloric effects. The thermodynamic properties can be calculated by using the ab initio magnetic exchange parameters in finite-temperature Monte Carlo simulations. The experimental entropy and specific heat changes across the magnetostructural transition are accurately reproduced by the Monte Carlo simulations. The predictive power of the first-principles calculations allows one to optimize the functional features by choosing optimal compositions.

Entel, Peter; Gruner, Markus E.; Comtesse, Denis; Wuttig, Manfred

2013-11-01

241

Non-destructive evaluation of mechanical properties of magnetic materials  

SciTech Connect

A magnetic-based non-destructive evaluation (NDE) method, which employs Barkhausen effect and measurement of the hysteresis loops, is used to correlate the magnetic and mechanical properties of ultra low carbon (ULC) steel. In particular, the NDE method was used to detect small deviations from linearity that occur in the stress-strain curve well below the 0.2% offset strain, and which generally defines the yield point in materials. Results show that three parameters: jumpsum and jumpsum rate (derived from the Barkhausen spectrum), and the relative permeability (derived from the B-H loops) varies sensitively with small permanent strains, and can be related to the plastic deformation in ULC steels. Investigation of micromagnetic structure revealed that plastic deformation leaves a residual stress state in the samples; the associated magneto-elastic energy makes the favorable easy axis of magnetization in a given grain to be the one that lies closest to the tensile axis. The consequence of this realignment of domains is that wall motion becomes intergranular in nature (as opposed to intragranular in unstrained samples). As a result, the more complex grain boundaries instead of dislocations, become the dominant pinning sites for domain walls. These observations provide a microscopic interpretation of the observed changes in the measured magnetic properties.

Kankolenski, K.P.; Hua, S.Z.; Yang, D.X.; Hicho, G.E.; Swartzendruber, L.J.; Zang, Z.; Chopra, H.D.

2000-07-01

242

Novel copper(II) homobinuclear macrocyclic complexes: Cyclic voltammetry, biological properties and spectral studies  

NASA Astrophysics Data System (ADS)

A series of five new copper(II) macrocyclic complexes have been synthesized by template condensation. The bonding and stereochemistry of the complexes have been characterized by elemental analysis, molar conductance, magnetic susceptibility, IR, UV-visible, EPR spectral studies and electrochemical properties. g-Values are calculated for all of the complexes in polycrystalline form as well as in DMSO solution. The magnetic and spectral data indicate square planar geometry for all the complexes. Cyclic voltammograms for all the complexes are similar and involve two quasi-reversible redox processes. Cu IICu II ? Cu IICu I ? Cu ICu I. Their biological properties have also been studied. The macrocyclic complexes show more anti-bacterial than controlled one. The anti-bacterial activities of the compounds were tested against Streptococcus fecalis and Escherichia coli with different concentrations.

Chandra, Sulekh; Gupta, Nidhi; Gupta, Rachna

2006-03-01

243

FLARES AND THEIR UNDERLYING MAGNETIC COMPLEXITY  

SciTech Connect

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 x 10{sup 33} T{sup 1.9{+-}0.1}.

Engell, Alexander J.; Golub, Leon; Korreck, Kelly [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138 (United States); Siarkowski, Marek; Gryciuk, Magda; Sylwester, Janusz; Sylwester, Barbara [Space Research Center, Polish Academy of Sciences, Kopernika 11, 51-622 Wroclaw (Poland); Cirtain, Jonathan, E-mail: aengell@cfa.harvard.edu [Marshall Space Flight Center NASA, Mail Code: VP62, Marshall Space Flight Center, AL 35812 (United States)

2011-01-01

244

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

245

Magnetized dusty plasmas: the next frontier for complex plasma research  

NASA Astrophysics Data System (ADS)

This paper discusses the role of magnetic fields in dusty (complex) plasma experiments. It first provides a description of the conditions necessary for a dusty plasma to become fully magnetized. The paper then briefly reviews a series of experimental studies that illustrate how magnetic fields are applied to dusty plasmas—from experiments that use magnetic fields to control the background plasma to those that have strong enough magnetic fields to directly modify the confinement and dynamics of the charged microparticles. The paper will then discuss the newest experiment that is currently under development at Auburn University, the magnetized dusty plasma experiment device. The paper concludes with a discussion of important outstanding physics and technical issues that will define the next generation of experiments.

Thomas, E., Jr.; Merlino, R. L.; Rosenberg, M.

2012-12-01

246

3-D vector magnetic properties of SMC Material for advanced field analysis of SMC machine  

Microsoft Academic Search

In a rotating electrical machine or the T-joints of a multiphase transformer, the magnetic flux is basically three-dimensional (3-D) and rotational. This paper presents the 3-D vector magnetic properties of soft magnetic composite (SMC) materials for advanced field analysis of electromagnetic devices with SMC core, which is particularly developed for application of electrical machines with complex structure and 3-D flux.

Youguang Guo; Jianguo Zhu; Haiyan Lu; Zhiwei Lin; Shuhong Wang; Jianxun Jin

2008-01-01

247

Magnetic properties of substituted barium ferrite powders  

SciTech Connect

Hexagonal barium ferrites were prepared using the citrate method. Cobalt and titanium were added in the amounts x from 0.2 to 1.1 ion/f.u. related to the formula BaCo{sub x}Ti{sub x}Fe{sub 12{minus}2x}O{sub 19}. The heat treatment has been applied in three steps of 550 C/5 hrs, 850 C/2 hrs and 1,100 C/2 hrs. The following magnetic properties have been achieved: H{sub c} {approximately} 80 kA/m, J{sub s} {approximately} 120 {times} 10{sup {minus}6} Tkg{sup {minus}1} m{sup 3}, and J{sub r} {approximately} 60 {times} 10{sup {minus}6} Tkg{sup {minus}1} m{sup 3} in the composition for which x is equal to 0.5 ion/f.u. The magnetic parameters have been measured by the vibration magnetometer.

Gruskova, A. [Slovak Univ. of Technology, Bratislava (Slovakia). Dept. of Electrotechnology] [Slovak Univ. of Technology, Bratislava (Slovakia). Dept. of Electrotechnology

1994-03-01

248

Synthesis and magnetic properties of nanostructured maghemite  

SciTech Connect

Nanocrystalline maghemite, {gamma}{endash}Fe{sub 2}O{sub 3}, can be synthesized in a microwave plasma using FeCl{sub 3} or Fe{sub 3}(CO){sub 12} as the precursor. Electron microscopy revealed particle sizes in the range of 5 to 10 nm. In general, this material is superparamagnetic. The magnetic properties are strongly dependent on the precursor. In both cases the production process leads to a highly disordered material with the consequence of a low magnetization. The assumption of a disordered structured is also supported by electron energy loss (EEL) and Moessbauer spectroscopy. The structure of this material shows a nearly identical number of cations on tetrahedral and octahedral lattice sites. {copyright} {ital 1997 Materials Research Society.}

Vollath, D.; Szabo, D.V. [Institut fuer Materialforschung III, Forschungszentrum Karlsruhe, P.O. Box 3640, D-76021 Karlsruhe (Germany); Taylor, R.D.; Willis, J.O. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

1997-08-01

249

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

250

Magnetic properties of nanoparticles of cenospheres from energetic ashes  

NASA Astrophysics Data System (ADS)

The application of magnetic cenospheres including ferrospinel nanoparticles as a “transport container” in medicine and biology is quite attractive. Their nanoscale size, high porosity, and well pronounced magnetic properties provide good consumer choice. In this contribution, we report on the magnetic properties of microspheres from energetic ashes of Ekibastuz coals.

Balaev, A. D.; Rabchevskii, E. V.; Anshits, A. G.; Petrov, M. I.

2006-12-01

251

Magnetic and related properties of silicates and phosphates  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume I5? `Phyllosilicates' of Volume 27 `Magnetic properties of non-metallic inorganic compounds based on transition elements' of Landolt-Börnstein - Group III `Condensed Matter'. It presents silicates belonging to the gillespite group with regard to their crystal structures, lattice parameters, magnetic properties, nuclear gamma resonance (NGR) data and optical properties.

Burzo, E.

252

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

SciTech Connect

The Nd-Fe-B bulk magnets with a slab shape of 0.9 x 4 x 15 mm{sup 3} 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 Nd{sub 9.5}Fe{sub 71.5}Ti{sub 2.5}Zr{sub 0.5}Cr{sub 1}B{sub 14.5}C{sub 0.5} alloy have been studied. The results show that the sample cast with magnetic field has a stronger (00L) texture of Nd{sub 2}Fe{sub 14}B 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 B{sub r} = 5.8 kG, {sub i}H{sub c} = 6.5 kOe, and (BH){sub max} = 5.9 MGOe for thesample cast without magnetic field to B{sub r} = 6.1 kG, {sub i}H{sub c} = 10.3 kOe, and (BH){sub max} = 7.3 MGOe for the sample cast with a 3.7 kOe magnetic field.

Wang, C. [Department of Physics, National Chung Cheng University, Chia-Yi 621, Taiwan (China); College of Materials Science and Engineering, Fuzhou University, Fuzhou 350108 (China); Lai, Y. S.; Hsieh, C. C.; Chang, W. C. [Department of Physics, National Chung Cheng University, Chia-Yi 621, Taiwan (China); Chang, H. W. [Department of Physics, Tunghai University, Taichung 407, Taiwan (China); Sun, A. C. [Department of Chemical Engineering and Materials Science, Yuan Ze University, Chung-Li 32003, Taiwan (China)

2011-04-01

253

Syntheses, crystal structures, and magnetic properties of two cyclic dimer M 2 L 2 complexes constructed from a new nitronyl nitroxide ligand and M(hfac) 2 (M = Cu 2+ ,M n 2+ )  

Microsoft Academic Search

Two new binuclear radical complexes derived from a new long nitronyl nitroxide ligand, 2-(4-(5-pyrimidyl)phenyl)-4,4,5,5-tetramethyl- imidazoline-1-oxyl-3-oxide (4-NITPhPyrim), and M(hfac)2 (M 2+ =C u 2+ ,M n 2+ ; hfac ? = hexafluoroacetylacetonato), (Cu(hfac)2- (4-NITPhPyrim))2 Æ 4H2 O( 1) and (Mn(hfac)2(4-NITPhPyrim))2 Æ 4H2 O( 2), were synthesized as well as characterized structurally and magnetically. X-ray analysis indicates that 1 and 2 are

Jian-Ying Zhang; Cai-Ming Liu; De-Qing Zhang; Song Gao; Dao-Ben Zhu

2007-01-01

254

Electric and magnetic functionality in complex oxides  

NASA Astrophysics Data System (ADS)

In recent years, there has been considerable progress in the field of perovskite related oxide films. The availability of single crystal films has allowed an improved understanding of their physical properties as well as the use of their functionality in novel applications. Since the pioneering work of McKee et al., PRL 81, 3014 (1998) -- who demonstrated the epitaxial integration of these oxides with Si -- one can now envision to couple the functionality of these materials with that of standard semiconductors. For three specific examples, we will illustrate how the specific material property of the oxide appears and can be tuned by various parameters such as thickness, strain, and interface control. The examples are the strained superconducting La_1.9Sr_0.1CuO4 compound (J.-P. Locquet et al., Nature, 394), 453 (1998), the uniaxial ferroelectric LaTiO_3.5 compound (J. W. Seo et al., PRB 63), 205401, 2001 and the antiferromagnet LaFeO3 (A. Scholl e t al., Science, 287), 1014 (2000).

Locquet, Jean-Pierre

2002-03-01

255

Synthesis, structure, and magnetic properties of tetranuclear cubane-like and chain-like iron(II) complexes based on the N(4)O pentadentate dinucleating ligand 1,5-bis[(2-pyridylmethyl)amino]pentan-3-ol.  

PubMed

The tetranuclear complexes [Fe(4)(pypentO)(pym)(3)(Oac)(NCS)(3)] x 1.5EtOH (1), [Fe(4)(pypentO)(pym)(Oac)(2)(NCS)(2)(MeO)(2)(H(2)O)] x H(2)O (2), [Fe(2)(pypentO)(NCO)(3)](2) (3), and [Fe(2)(pypentO)(N(3))(3)](2) (4) have been prepared, and their structure and magnetic properties have been studied (pypentOH = 1,5-bis[(2-pyridylmethyl)amino]pentan-3-ol, pymH = 2-pyridylmethanol). The X-ray diffraction analysis of 1 (C(43)H(53)N(10)O(7.5)S(3)Fe(4), monoclinic, P2(1)/n, a = 11.6153(17) A, b = 34.391(17) A, c = 14.2150(18) A, beta = 110.88(5) degrees, V = 5305(3) A(3), Z = 4) and 2 (C(31)H(45)N(7)O(10)S(2)Fe(4), monoclinic, C2/c, a = 19.9165(17) A, b = 21.1001(12) A, c = 21.2617(19) A, beta = 104.441(10) degrees, V = 8652.7(12) A(3), Z = 8) showed a Fe(4)O(4) cubane-like arrangement of four iron(II) atoms, four mu(3)-O bridging ligands, one (1) or two (2) syn-syn bridging acetates. The X-ray diffraction analysis of 3 (C(40)H(46)N(14)O(8)Fe(4), monoclinic, P2(1)/c, a = 11.7633(18) A, b = 18.234(3) A, c = 10.4792(16) A, beta = 99.359(18) degrees, V = 2217.7(6) A(3), Z = 2) and 4 (C(34)H(46)N(26)O(2)Fe(4), monoclinic, P2(1)/c, V = 4412.4(10) A(3), a = 23.534(3) A, b = 18.046(2) A, c = 10.4865(16) A, beta = 97.80(2) degrees, Z = 4) showed a zigzag bis-dinuclear arrangement of four iron(II) cations, two mu(2)-O bridging pypentO ligands, four mu(2)-N-cyanato bridging ligands (3) or four end-on azido bridging ligands (4): they are the first examples of cyanato and azido bridged discrete polynuclear ferrous compounds, respectively. The Mössbauer spectra of 1 are consistent with four different high-spin iron(II) sites in the Fe(4)O(4) cubane-type structure. The Mössbauer spectra of 3 are consistent with two high-spin iron(II) sites (N(5)O and N(4)O). Below 190 K, the Mössbauer spectra of 4 are consistent with one N(5)O and two N(4)O high-spin iron(II) sites. The temperature dependence of the magnetic susceptibility was fitted with J(1) approximately 0 cm(-1), J(2) = -1.3 cm(-1), J(3) = 4.6 cm(-1), D = 6.4 cm(-1), and g = 2.21 for 1; J(1) = 2.6 cm(-1), J(2) = 2.5 cm(-1), J(3) = - 5.6 cm(-1), D = 4.5 cm(-1), and g = 2.09 for 2; J(1) = 1.5 cm(-1), J(2) = 0.2 cm(-1), D = - 5.6 cm(-1), D' = 4.5 cm(-1), and g = 2.14 for 3; and J(1) = - 2.6 cm(-1), J(2) = 0.8 cm(-1), D= 6.3 cm(-1), D' = 1.6 cm(-1), and g = 2.18 for 4. The differences in sign among the J(1), J(2), and J(3) super-exchange interactions indicate that the faces including only mu(3)-OR bridges exhibit ferromagnetic interactions. The nature of the ground state in 1-3 is confirmed by simulation of the magnetization curves at 2 and 5 K. In the bis-dinuclear iron(II) compounds 3 and 4, the J(2) interaction resulting from the bridging of two Fe(2)(pypentO)X(3) units through two pseudo-halide anions is ferromagnetic in 3 (X = mu(2)-N-cyanato) and may be either ferro- or antiferromagnetic in 4 (X = end-on azido). The J(1) interaction through the central O(alkoxo) and pseudo-halide bridges inside the dinuclear units is ferromagnetic in 3 (X = mu(2)-N-cyanato) and antiferromagnetic in 4 (X = end-on azido). In agreement with the symmetry of the two Fe(II) sites in complexes 3 and 4, D (pentacoordinated sites) is larger than D' (octahedral sites). PMID:11896717

Clemente-Juan, Juan M; Mackiewicz, Christine; Verelst, Marc; Dahan, Françoise; Bousseksou, Azzedine; Sanakis, Yiannis; Tuchagues, Jean-Pierre

2002-03-25

256

Magnetic properties measurement of soft magnetic composite materials over wide range of excitation frequency  

Microsoft Academic Search

Accurate measurements of magnetic properties of soft magnetic composite (SMC) material are performed on an improved 3D tester by means of novel precision B-H sensing coils attached to the surface of the specimen. By controlling the adjustable excitation topologies, magnetic properties over wide excitation frequency range from 2 Hz to 1000 Hz are acquired and analyzed. In this paper, the

Yongjian Li; Jianguo Zhu; Qingxin Yang; Zhi Wei Lin; Yi Wang; Wei Xu

2010-01-01

257

Review of the low-temperature magnetic properties of magnetite from a rock magnetic perspective  

Microsoft Academic Search

The low-temperature magnetic properties of magnetite are reviewed, and implications for rock magnetism considered. The behaviour of fundamental properties of magnetite at low temperatures near the Verwey transition (Tv) are documented, and attention is given to various Verwey transition theories. The low-temperature behaviour of the magnetic energies that control domain structure is reviewed in detail. For the first time in

A. R. Muxworthy; E. McClelland

2000-01-01

258

Magnetic blocking in a linear iron(I) complex.  

PubMed

Single-molecule magnets that contain one spin centre may represent the smallest possible unit for spin-based computational devices. Such applications, however, require the realization of molecules with a substantial energy barrier for spin inversion, achieved through a large axial magnetic anisotropy. Recently, significant progress has been made in this regard by using lanthanide centres such as terbium(III) and dysprosium(III), whose anisotropy can lead to extremely high relaxation barriers. We contend that similar effects should be achievable with transition metals by maintaining a low coordination number to restrict the magnitude of the d-orbital ligand-field splitting energy (which tends to hinder the development of large anisotropies). Herein we report the first two-coordinate complex of iron(I), [Fe(C(SiMe3)3)2](-), for which alternating current magnetic susceptibility measurements reveal slow magnetic relaxation below 29 K in a zero applied direct-current field. This S =  complex exhibits an effective spin-reversal barrier of Ueff = 226(4) cm(-1), the largest yet observed for a single-molecule magnet based on a transition metal, and displays magnetic blocking below 4.5 K. PMID:23787747

Zadrozny, Joseph M; Xiao, Dianne J; Atanasov, Mihail; Long, Gary J; Grandjean, Fernande; Neese, Frank; Long, Jeffrey R

2013-07-01

259

Study with magnetic property measurement of soft magnetic composite material and its application in electrical machines  

Microsoft Academic Search

This paper reports our study with the magnetic property measurements of soft magnetic composite (SMC) materials under both alternating and rotational magnetic excitations, and development of different electrical machines with SMC cores and three-dimensional magnetic field, such as claw pole and transverse flux motors. Three-dimensional finite element electromagnetic field analysis is conducted for determining some important parameters and optimizing the

Jian Guo Zhu; YouGuang Guo

2004-01-01

260

Effects Of Hydrothermal Alteration On Magnetic Properties And Magnetic Signatures - Implications For Predictive Magnetic Exploration Models  

NASA Astrophysics Data System (ADS)

Magnetics is the most widely used geophysical method in hard rock exploration and magnetic surveys are an integral part of exploration programs for many types of mineral deposit, including porphyry Cu, intrusive-related gold, volcanic-hosted epithermal Au, IOCG, VMS, and Ni sulfide deposits. However, the magnetic signatures of ore deposits and their associated mineralized systems are extremely variable and exploration that is based simply on searching for signatures that resemble those of known deposits and systems is rarely successful. Predictive magnetic exploration models are based upon well-established geological models, combined with magnetic property measurements and geological information from well-studied deposits, and guided by magnetic petrological understanding of the processes that create, destroy and modify magnetic minerals in rocks. These models are designed to guide exploration by predicting magnetic signatures that are appropriate to specific geological settings, taking into account factors such as tectonic province; protolith composition; post-formation tilting/faulting/ burial/ exhumation and partial erosion; and metamorphism. Patterns of zoned hydrothermal alteration are important indicators of potentially mineralized systems and, if properly interpreted, can provided vectors to ore. Magnetic signatures associated with these patterns at a range of scales can provide valuable information on prospectivity and can guide drilling, provided they are correctly interpreted in geological terms. This presentation reviews effects of the important types of hydrothermal alteration on magnetic properties within mineralized systems, with particular reference to porphyry copper and IOCG deposits. For example, an unmodified gold-rich porphyry copper system, emplaced into mafic-intermediate volcanic host rocks (such as Bajo de la Alumbrera, Argentina) exhibits an inner potassic zone that is strongly mineralized and magnetite-rich, which is surrounded by an outer potassic zone that contains less abundant, but still significant, magnetite. The inner potassic zone represents relatively intense development of qtz-mt-Kfsp veins, whereas the outer potassic zone corresponds to bio-Kfsp-qtz-mt alteration. A shell of magnetite-destructive phyllic alteration with very low susceptibility envelops the potassic zones. The phyllic zone is surrounded by a zone of intense propylitic alteration, which is partially magnetite-destructive, which passes out into weak propylitic alteration and then into unaltered, moderately magnetic volcanics. For such a system, emplaced into magnetic intermediate-mafic igneous host rocks and exposed after removal by erosion of ~ 1 km of overburden, a strong central RTP high is surrounded by a relatively weak annular low over the phyllic zone, gradually returning to background levels over the propylitic zone (an "archery target" signature). For a completely buried system, however, the signature is basically an alteration low due to the large volume of magnetite-destructive alteration surrounding the deeply buried magnetic core.

Clark, D.

2012-12-01

261

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

262

Topological properties of refinery system: A complex network approach  

Microsoft Academic Search

Recent development in complex network theory has boosted the exploration of topological properties of various natural and man-made complex systems. Refinery system is a typical complex system in process industry. However, only plant at equipment level has been studied by the complex network theory. This article treats the whole refinery system at plant level as a network. Study illustrates that

Suyu Liu; Zuwei Liao; Yiping Feng; Gang Rong

2010-01-01

263

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

264

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

265

Structural tailoring effects on the magnetic behavior of symmetric and asymmetric cubane-type Ni complexes.  

PubMed

Using two kinds of carboxylate ligands with small but significant differences in steric size, symmetric and asymmetric Fe(II) and Ni(II) cubanes have been synthesized in a controlled fashion. Fast sweeping pulsed field measurements showed magnetization hysteresis loops for two cubane-type molecular complexes, [Ni4(?-OMe)4(O2CAr(4F-Ph))4(HOMe)8] and [Ni4(?-OMe)4(O2CAr(Tol))4(HOMe)6], thus suggesting single-molecule magnet behavior. To differentiate the magnetic properties between the symmetric and asymmetric cubanes, detailed electron paramagnetic resonance (EPR) measurements were performed. From the EPR data, taken at various frequencies and temperatures, zero-field splitting parameters D, E, and other higher-order parameters for both cubane samples were extracted. Compared to the symmetric Ni-cubane, the asymmetric one shows an increase in the D and E values by about 20%, thereby suggesting structural engineering effects on the magnetic properties. By using the magnetic parameters determined by EPR, a static magnetization curve at 2?K and a temperature dependence of the magnetic susceptibility were simulated. A good agreement between theoretical and experimental data confirms the validity of the values obtained from EPR measurements. PMID:23509044

Ponomaryov, Alexey N; Kim, Namseok; Hwang, Jaewon; Nojiri, Hiroyuki; van Tol, Johan; Ozarowski, Andrew; Park, Jena; Jang, Zeehoon; Suh, Byoungjin; Yoon, Sungho; Choi, Kwang-Yong

2013-06-01

266

Optical and magnetic properties of boron fullerenes.  

PubMed

We report linear response properties of the recently proposed boron fullerenes [N. Gonzalez Szwacki et al., Phys. Rev. Lett., 2007, 98, 166804]: magnetic susceptibilities, static dipole polarizabilities and dynamical polarizabilities (i.e. optical and near ultraviolet absorption spectra), calculated from first principles within the (time-dependent) density-functional theory framework. We find that all clusters except B80 are diamagnetic. The strong cancellation between diamagnetic and paramagnetic currents in B80 leads to a very small value for its susceptibility that turns out to be slightly paramagnetic. Static polarizabilities increase linearly with the number of B atoms. Furthermore, the absorption spectrum of B80 is very different from the one of its carbon counterpart C60, exhibiting a low absorption threshold of about 1.5 eV and many peaks in the visible and near ultraviolet. This can be understood by the analysis of the wavefunctions involved in the low energy transitions. PMID:19475170

Botti, Silvana; Castro, Alberto; Lathiotakis, Nektarios N; Andrade, Xavier; Marques, Miguel A L

2009-06-14

267

Magnetic properties of Fe-based alloys  

NASA Astrophysics Data System (ADS)

The magnetic properties of fcc FexNi1-x and FexCo1-x alloys grown on Cu(100) were investigated in an element-specific fashion. The technique employed was linear dichroism in photoemission, which by varying the chirality can also determine the magnetization axis. We observed a different behavior for the two alloys at Fe concentrations above 60%. At this concentration the FexNi1-x alloy shows a strong reduction of the Fe dichroism associated with the invar instability. This is in contrast to the FexCo1-x alloy, where the Fe dichroism stays essentially constant across the concentration. Despite these differences both systems show a change of the easy axis at roughly the same electron count. For small Fe concentrations the easy axis is in-plane along the [011] direction. This changes into the [001] direction at Fe63Ni37, which is at 0.7 excess electrons per atom when compared with Fe. This is different to the bulk, where a change occurs at Fe25Ni75. We find the easy axis change for FexCo1-x to occur at 49% Fe. This would be equivalent to 0.5 excess electrons when compared with Fe.

Schumann, F. O.; Tobin, J. G.

2000-05-01

268

Preliminary results of a study of magnetic properties in the Foum-Zguid dyke (Morocco)  

NASA Astrophysics Data System (ADS)

This work focuses on the study of flow and propagation of magma using rock magnetic analyses along sections across the thick Jurassic dyke of Foum-Zguid (Southern Morocco). Thermomagnetic data show that Ti-poor titanomagnetite is the main magnetic carrier. Petrographic analysis shows that the main Ti phase (ilmenite) occurs either as lamellae within spinel (center of the dyke) or as isolated grains (dyke margin). Bulk magnetic properties display distinct behavior according to the distance to the dyke margin; grain size of the main magnetic carrier decreases towards the center of the dyke, while the natural remanent magnetization and the bulk magnetic susceptibility increase. Only the magnetic susceptibility ellipsoid close to the dyke margin corresponds to that usually found in thin dykes, with the magnetic foliation sub parallel to dyke margins. Maximum principal axis is in most cases either parallel or perpendicular to the intersection between the planes of magnetic foliation and dyke wall. Moreover, when this axis is perpendicular to the intersection it is associated with a more oblate magnetic susceptibility ellipsoid shape, indicating the presence of complex magnetic fabrics. The studied magnetic properties show that, in this 100 m wide thick dyke, flow structures related with dyke propagation are only preserved close to the quickly cooled dyke margins.

Silva, P. F.; Marques, F. O.; Henry, B.; Mateus, A.; Lourenço, N.; Miranda, J. M.

269

High temperature 2:17 magnets: relationship of magnetic properties to microstructure and processing  

Microsoft Academic Search

A comprehensive and systematic study on Sm(CobalFevCuyZrx)z magnets is made to completely understand the effects of composition and processing on their magnetic properties. These studies include the compositions required for the formation of cellular\\/lamellar microstructure, the effects of compositions (x, y, v, z) and processing (aging temperature and time) on microstructure and magnetic properties, the evolution of microstructure and magnetic

G. C. Hadjipanayis; Wei Tang; Y. Zhang; S. T. Chui; J. F. Liu; C. Chen; H. Kronmuller

2000-01-01

270

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

271

Synthesis and Properties of Magnetic Fine Particles  

NASA Astrophysics Data System (ADS)

Magnetic fine particles with a variety of compositions and sizes have been prepared by aerosol and coprecipitation technique. Their magnetic properties are shown to be either similar to or quite different from those of their bulk counterparts. Iron oxide, barium iron oxide and neodynium iron based fine particles have been synthesized by an aerosol technique which produced particles with average size of about 100 nm. It was found that the as-received samples were usually in thermally unstable states because of their short residence time (seconds) at the high temperature when they were created. Heat treatment turned these as -received particles into more stable phases. The final product depended on temperature, environment and composition of the initial solution. Cation and anion effects and solvent effects on the formation and morphology of the final particle have been also observed. Manganese ferrite fine particles have been made by hydroxide induced coprecipitation of mixed iron and manganese salt solutions. The particle size appeared to be an unique function of the ratio of the metallic ion concentration to the hydroxide ion concentration when the digestion conditions were fixed. The system which used ferric salt created small MnFe_2 O_4 particles with size controllable between 5 and 25 nm. The digestion process could be described by an Ostwald ripening in which OH^- acts as a catalyst. Variation of cations showed that their oxidation states had a strong influence on the particle size. The system which used ferrous salt, however, produced larger ferrite particles (above 50 nm) with single ferrite phase (Mn_ xFe_{3-x}O_4 with x <= 0.7). Dissolution and renucleation/growth occurred during digestion. For larger particles, the magnetizations were the same as for the bulk of the phases present, while the coercivities were more system dependent. We have found that nanoscale particles, on the other hand, showed profound size effects. The saturation magnetization of ultrafine MnFe_2 O_4 particles was substantially lower than that of the bulk and decreased with declining particle size due to a surface effect which came from a 7 A thick nonmagnetic surface layer. Careful characterization showed that the particle size was the only independent variable. The Curie temperature in MnFe _2 O_4 was seen to increase with decreasing particle size. The behavior was in good agreement with finite-size scaling. This size dependent Curie temperature caused difficulty in determining critical exponents due to size distribution of fine particle systems. This was the first time that studies of critical phenomena in fine particles have been even attempted.

Tang, Zhongxun

272

Magnetic properties of polymer nanocomposites containing iron oxide nanoparticles  

Microsoft Academic Search

The magnetic behavior of polymer nanocomposites containing nanoparticles (?10nm) of oxidized magnetite in a polyvinyl alcohol matrix were investigated by means of Mossbauer transmission and conversion electron spectroscopy and magnetic measurements. The obtained results show that the base concentration of iron oxide nanoparticles within the polymer matrix volume greatly influences the magnetic properties of nanocomposites. The estimated lamellar distribution of

A. A. Novakova; V. Yu. Lanchinskaya; A. V. Volkov; T. S. Gendler; T. Yu. Kiseleva; M. A. Moskvina; S. B. Zezin

2003-01-01

273

Electrical and Magnetic Properties of Metal Filled Composites  

Microsoft Academic Search

The development of the electric and magnetic properties of metal-filled polymeric composites was investigated. The effects of the particle size and distribution, particle concentration, particle aspect ratio and distribution and the orientation functions of high aspect ratio particles on the volume and surface resistivity, dielectric constant, magnetic permeability and electric and magnetic loss factors were characterized. Percolation limits were established

Thomas Joseph Fiske

1996-01-01

274

Magnetic properties of thin films of soft superconductors  

Microsoft Academic Search

The torque method of measuring the magnetic properties of thin superconducting layers is discussed, and some results reported for experiments in which magnetic fields are applied parallel and perpendicular to the plane of evaporated films of tin, indium and indium-tin alloy. For the parallel case critical fields and supercooling fields can be measured. For the perpendicular case magnetization curves can

G. Robinson

1966-01-01

275

Magnetism in complex oxides probed by transverse susceptibility and magnetocaloric effect  

NASA Astrophysics Data System (ADS)

Magnetic oxides exhibit rich complexity in their fundamental physical properties determined by the intricate interplay between structural, electronic and magnetic degrees of freedom. The common theme that is often present in many systems is the strong magnetostructural coupling and possible spin frustration induced by lattice geometry. In this talk, we will demonstrate the relatively unconventional experimental methods of RF transverse susceptibility (TS) and magnetocaloric effect (MCE) as being powerful probes of multiple magnetic transitions, glassy phenomena and ground state magnetic properties in three classes of oxides including Pr0.5Sr0.5CoO3, LuFe2O4 and mixed phase manganite (La,Pr,Ca)MnO3. The TS experiments reveal a coupled structural/magnetocrystalline anisotropy transition in Pr0.5Sr0.5CoO3 driven by Pr-O hybridization and the nature of this transition is also clarified in MCE experiments. These results point to the existence of an entirely new class of phenomena in the cobaltites due to the unique interplay between structure and magnetic anisotropy. In LuFe2O4, our experiments show the emergence of a complex phase diagram with ferrimagnetic clusters undergoing two glass transitions followed by kinetic arrest at low temperature. Finally, in LPCMO, we will discuss the subtle balance between coexistence of ferromagnetic metal (FMM), charge-ordered insulator (COI) and paramagnetic insulator (PMI) phases that are highly sensitive to strain and dimensionality.

Srikanth, Hariharan

2010-03-01

276

Magnetic properties of Dashing Rocks loess at Timaru, South Island, New Zealand  

NASA Astrophysics Data System (ADS)

The relationships between magnetic susceptibility and pedogenic development are different in various regions of the world. For example, loess magnetic susceptibility shows a positive correlation with pedogenic development in Chinese Loess Plateau (CLP), while it displays a negative correlation with pedogenesis in Alaska and Siberia. To better understand the relationship between magnetic properties and pedogenic development, detailed sampling of Dashing Rocks loess section at Timaru, South Island, New Zealand, was carried out. Multiproxy magnetic parameters such as magnetic susceptibility, anhysteretic remanent magnetization, magnetic hysteresis loops, Ms-T curves and ?-T curves were measured. The results show that the types of magnetic minerals are similar to CLP: magnetite, maghemite, goethite and hematite. However, great differences are found in their concentration: most minerals in the Dashing Rocks section are hard magnetic, such as goethite, the content of paramagnetic minerals is rather high, while the soft-magnetic mineral content is very low. Hard-magnetic and paramagnetic minerals increase with depth, but soft-magnetic minerals decrease with depth, and are absent in the lower part of the profile. Gammate soil structures and Fe/Mn nodules (or pans) are commonly observed in the section, indicating that high susceptibility magnetite and maghemite have been converted to goethite and migrated downward to enrich certain horizons during chemical weathering. This process leads to lower magnetic susceptibility values, possibly related to the source and the transformation of soft-magnetic minerals in a high soil moisture environment. The relationship between magnetic susceptibility and pedogenic development in Dashing Rocks loess section is therefore different from the simple positive and negative relationships in CLP and Siberia, respectively. The more complex relationships between magnetic properties and pedogenic development in New Zealand loess may be related to differing degrees of magnetic mineral transformation at different depths and at different times.

Ma, Mingming; Liu, Xiuming; Pillans, Brad J.; Hu, Shouyun; Lü, Bin; Liu, Huifeng

2013-10-01

277

Magnetic properties of ?-Fe 2O 3 nanowires  

NASA Astrophysics Data System (ADS)

Some basic magnetic properties of ?-Fe 2O 3 nanowires synthesized by oxygenating pure iron are reported. The blocking temperature of the nanowires is 120 K, where the field-cooled and zero-field-cooled magnetization curves diverge, and the hysteresis loops vary notably with temperature. No evidence for Morin transition is found in the temperature range 4-300 K. In addition, the magnetic behavior below 50 K shows a further freezing of magnetic moments. Compared with nanoparticles, the nanowires show some significant differences in magnetic properties.

Xu, Y. Y.; Rui, X. F.; Fu, Y. Y.; Zhang, H.

2005-07-01

278

Effect of process on the magnetic and mechanical properties of Nd–Fe–B bonded magnets  

Microsoft Academic Search

Bonded Nd–Fe–B magnets were prepared through the compression molding method. The effects of preparation technology on their magnetic and mechanical properties were studied through the analysis of Br, Hcj, and (BH)max, and through an analysis of their flexural and compressive strengths. The results demonstrated that the mechanical properties increased, while the magnetic properties decreased along with the increase of binder

X. H. Zhang; W. H. Xiong; Y. F. Li; N. Song

2009-01-01

279

Understanding and controlling complex states arising from magnetic frustration  

SciTech Connect

Much of our national security relies on capabilities made possible by magnetism, in particular the ability to compute and store huge bodies of information as well as to move things and sense the world. Most of these technologies exploit ferromagnetism, i.e. the global parallel alignment of magnetic spins as seen in a bar magnet. Recent advances in computing technologies, such as spintronics and MRAM, take advantage of antiferromagnetism where the magnetic spins alternate from one to the next. In certain crystal structures, however, the spins take on even more complex arrangements. These are often created by frustration, where the interactions between spins cannot be satisfied locally or globally within the material resulting in complex and often non-coplanar spin textures. Frustration also leads to the close proximity of many different magnetic states, which can be selected by small perturbations in parameters like magnetic fields, temperature and pressure. It is this tunability that makes frustrated systems fundamentally interesting and highly desirable for applications. We move beyond frustration in insulators to itinerant systems where the interaction between mobile electrons and the non-coplanar magnetic states lead to quantum magneto-electric amplification. Here a small external field is amplified by many orders of magnitude by non-coplanar frustrated states. This greatly enhances their sensitivity and opens broader fields for applications. Our objective is to pioneer a new direction for condensed matter science at the Laboratory as well as for international community by discovering, understanding and controlling states that emerge from the coupling of itinerant charges to frustrated spin textures.

Zapf, Vivien [Los Alamos National Laboratory

2012-06-01

280

Complex forming properties of natural organic acids. Pt. 2. Complexes with iron and calcium.  

National Technical Information Service (NTIS)

An ultrafiltration technique combined with ion-selective-electrode and atomic absorption methods have been employed to obtain information on the complex forming properties of fulvic acid with iron and calcium. A model for interpreting complexation of meta...

J. H. Ephraim A. S. Mathuthu J. A. Marinsky

1990-01-01

281

Magnetic properties of biomineral particles produced by bacteria Klebsiella oxytoca  

NASA Astrophysics Data System (ADS)

Ferrihydrite nanoparticles (2-5 nm in size) produced by bacteria Klebsiella oxytoca in the course of biomineralization of iron salt solutions from a natural medium exhibit unique magnetic properties: they are characterized by both the antiferromagnetic order inherent in a bulk ferrihydrite and the spontaneous magnetic moment due to the decompensation of spins in sublattices of a nanoparticle. The magnetic susceptibility enhanced by the superantiferromagnetism effect and the magnetic moment independent of the magnetic field provide the possibility of magnetically controlling these natural objects. This has opened up the possibilities for their use in nanomedicine and bioengineering. The results obtained from measurements of the magnetic properties of the ferrihydrite produced by Klebsiella oxytoca in its two main crystalline modifications are reported, and the data obtained are analyzed theoretically. This has made it possible to determine numerical values of the magnetic parameters of real biomineral nanoparticles.

Ra?kher, Yu. L.; Stepanov, V. I.; Stolyar, S. V.; Ladygina, V. P.; Balaev, D. A.; Ishchenko, L. A.; Balasoiu, M.

2010-02-01

282

Investigation of electrical and magnetic properties of triangular antiferromagnets  

Microsoft Academic Search

We have synthesized magnetic Fe-doped NiGa2S4 and investigated its electrical and magnetic properties with a superconducting quantum-interference device magnetometer, Mössbauer spectroscopy, and a physical property measurement system. X-ray diffraction analysis at room temperature shows that the prepared samples are single phase with trigonal structure (P-3m1). From zero-field-cooled (ZFC) and field-cooled magnetization curves under 100 Oe between 4.2 and 200 K,

Bo Ra Myoung; Chin Mo Kim; Sam Jin Kim; Taejoon Kouh; Yasushi Hirose; Tetsuya Hasegawa; Chul Sung Kim

2011-01-01

283

Magnetic and Electrical Properties of U-Ge Intermetallic Compounds  

Microsoft Academic Search

We have clarified the magnetic and electrical properties of U7Ge, U5Ge3, U3Ge4 and UGe2, measuring the electrical resistivity, thermoelectric power, Hall coefficient, magnetic susceptibility, magnetization and specific heat. U7Ge and U5Ge3, which are Pauli paramagnetic compounds, become superconductive below 1.40 K and 0.99 K, respectively. The latter compounds U3Ge4 and UGe2 indicate ferromagnetism. Anisotropic properties of UGe2 are well reflected

Yoshichika Onuki; Isamu Ukon; Sung Won Yun; Izuru Umehara; Kazuhiko Satoh; Tadashi Fukuhara; Hideyuki Sato; Shigeru Takayanagi; Mikio Shikama; Akira Ochiai

1992-01-01

284

Magnetic Properties of the Wenchuan Earthquake Slip Zone  

NASA Astrophysics Data System (ADS)

Motivated by an interest in investigating large earthquake mechanisms, the Wenchuan earthquake Fault Scientific Drilling project (WFSD) has been launched on November 4, 2008, only 178 days after the Wenchuan earthquake struck. Large earthquakes have a signi?cant influence on the rock magnetic records in fault slip zones. The first borehole (WFSD-1) was drilled through 1201.15 m including Pengguan complex rocks of about 800 Ma and alternating sandstones and siltstones of Triassic age at the southern segment of the Yingxiu-Beichuan fault (N31° 8'59.36", E103° 41'28.71"). WFSD-1 shed light to the existence of at least 12 fault zones. The Principal Slip Zone (PSZ) of the Wenchuan earthquake has been identified at a depth of 589.17 m to 589.28 m (FZ590). To understand the high magnetic susceptibility in FZ590, we sampled 6 specimens every 10 cm down from 589.05 m-depth to 589.55 m-depth. The amount of sample is typically about 3-5 g of powder due to the limited and valuable material available. A series of rock magnetic investigations were made, such as mass magnetic susceptibility, high-temperature magnetic susceptibility, magnetic hysteresis loops. The mass and ferromagnetic materials magnetic susceptibility from the 589.25 m-depth sample shows a higher peak than from other samples, while the paramagnetic materials magnetic susceptibility shows a decrease from 589.05 to 589.55 m-depth. The k-T curves of the selected samples all display a rapid slope increase after 380°and a marked peak occurs at about 510°in the heating curves. The magnetic susceptibility reaches zero at about 585°. Every cooling curve shows a clear hump between 580° and 380°, which is clearly higher than the heating curves. The hysteresis loops show the character of closed at about 0.3 T and the low-coercivity phases. The hysteresis parameters are plotted in a Mr/Ms versus Hcr/Hc diagram, except the 589. 55 m-depth sample, which could not be determined due to a very weak expression. All the samples display typical Pseudo-Single Domain (PSD) field. Rock magnetic data from a small amount of samples provide valuable information on the core PSZ. The primary ferromagnetic minerals in this segment are magnetite with the PSD grain size, which suggests that the grain size cannot be the main reason for the high magnetic susceptibility at the PSZ. The dominant mechanism responsible for the 589.25 m-depth high magnetic susceptibility might be the production of new magnetite from iron-containing silicates or clays (e.g. chlorite) caused by frictional heating during earthquakes. Keywords Wenchuan Earthquake, Yingxiu-Beichuan Fault, Slip Zone, Magnetic Properties

pei, junling; li, haibing; sun, zhiming; si, jialiang; wang, huan

2013-04-01

285

Influence of complexing agent on the electrodeposited Co Pt W magnetic thin films  

NASA Astrophysics Data System (ADS)

Complexing agents are often used to improve the quality of electrodeposited alloys. Influence of different complexing agents with hydroxycarboxylic acid group on the electrodeposited Co-Pt-W thin films has been investigated. Cathodic polarization curves show that the polarization behaviors of electroplating bath with different complexing agents are very different. Surface morphology, phase composition and magnetic properties are observed by means of FESEM, XRD and vibrating sample magnetometer (VSM), respectively. It has been found out that, if citrate was used as complexing agent, the Co-Pt-W thin films were homogeneous and the granular crystals with the average grain size of 2 ?m have been observed. Co-Pt-W thin films exhibited hexagonal close packed (hcp) lattice and strong perpendicular anisotropic magnetic behavior ( Hc? = 215.5 kA/m; Hc? = 55.4 kA/m). In the presence of gluconate, needle-like deposits were obtained and a strong face centered cubic (fcc(1 1 1)) texture was measured. The Co-Pt-W thin films showed isotropic magnetic behavior. In the case of tartate and malate, the coexistence of needle-like deposits and cellular deposits appeared. The XRD patterns showed that the mixed fcc and hcp phase formed. Perpendicular anisotropic magnetic behaviors of thin films, from malate or tartate baths, were not obvious.

Wei, Guoying; Ge, Hongliang; Huang, Lihong; Wu, Qiong; Wang, Xinqing; Huang, Liming

2008-03-01

286

Magnetic properties of 1 : 4 complexes of CoCl2 and pyridines carrying carbenes (S(0) = 4/2, 6/2, and 8/2) in diluted frozen solution; influence of carbene multiplicity on heterospin single-molecule magnets.  

PubMed

The microcrystalline sample of a parent complex, [CoCl(2)(py)(4)], showed a single-molecule magnet (SMM) behavior with an effective activation barrier, U(eff)/k(B), of 16 K for reversal of the magnetism in the presence of a dc field of 3 kOe. Pyridine ligands having 2-4 diazo moieties, DYpy; Y = 2, 3l, 3b, and 4, were prepared and confirmed to be quintet, septet, septet, and nonet in the ground state, respectively, after irradiation. The 1 : 4 complexes, CoCl(2)(DYpy)(4); Y = 2, 3l, 3b, and 4 in frozen solutions after irradiation showed the magnetic behaviors of SMMs with total spin multiplicity, S(total) = 17/2, 25/2, 25/2, and 33/2, respectively. Hysteresis loops depending on the temperature were observed and the values of coercive force, H(c), at 1.9 K were 12, 8.4, 11, and 8.1 kOe for CoCl(2)(CYpy)(4); Y = 2, 3l, 3b, and 4, respectively. In dynamic magnetic susceptibility experiments, ac magnetic susceptibility data obeyed the Arrhenius law to give U(eff)/k(B) values of 94, 92, 93, and 87 K for CoCl(2)(CYpy)(4); Y = 2, 3l, 3b, and 4, respectively, while the relaxation times for CoCl(2)(CYpy)(4); Y = 2 and 3l, obtained by dc magnetization decay in the range of 3.5-1.9 K slightly deviated downward from Arrhenius plots on cooling. The dynamic magnetic behaviors for CoCl(2)(CYpy)(4) including [CoCl(2)(py)(4)] and CoCl(2)(C1py)(4) suggested that the generated carbenes interacted with the cobalt ion to increase the relaxation time, ?(q), due to the spin quantum tunneling magnetization, which became larger with increasing S(total) of the complex. PMID:22898723

Karasawa, Satoru; Nakano, Kimihiro; Tanokashira, Jun-ichi; Yamamoto, Noriko; Yoshizaki, Takahito; Koga, Noboru

2012-11-28

287

Magnetic, Electronic, and Structural Properties of Ferric Chloride Intercalated Graphite.  

NASA Astrophysics Data System (ADS)

The magnetic, electronic, and structural properties of intercalated graphite compounds in general, and ferric chloride intercalated graphite compounds in particular, are examined by various experimental and theoretical techniques. Both a microscopic experiment, Mossbauer spectroscopy, and a macroscopic experiment, magnetic susceptibility, indicate that stage 1 and 2 compounds undergo a long-range magnetic phase transition, while evidence is found that stage 4 and 6 compounds do not magnetically order down to 65mK. The magnetic transition temperature dramatically decreases as more diamagnetic graphite planes are added. Therefore, we conclude that the ordering mechanism is influenced by interlayer interactions thus providing direct evidence that magnetic ordering in these compounds is a three-dimensional effect. By using Mossbauer spectroscopy as a characterization tool, we find a sample dependent number of iron vacancies, which dramatically influences the susceptibility curves of the samples. Thus these two experiments also help elucidate the role of iron vacancies in disturbing long-range order thus causing some of the iron spins to acquire spin-glass like characteristics. The electronic properties of these compounds are also examined by Mossbauer spectroscopy. Below 100K donated electrons from the graphite lattice are localized on some ferric chloride sites to change these iron sites from ferric to ferrous sites. The Mossbauer data indicate that at low temperatures the ferric and ferrous sites are not randomly situated, and may form a unique chemical superlattice. The localization process is studied by Mossbauer spectroscopy and two possible explanations of the data are presented. We also examine the role of iron vacancies on the acceptor site. We find that chlorine atoms surrounding iron vacancies, when present in sufficient number, may act as the primary acceptor site for the electrons donated by the graphite to the intercalant. The effects of long-term exposure to air on these compounds is also studied by Mossbauer spectroscopy. A simple model of staging in graphite intercalation compounds is presented which yields only the staged structures which are observed experimentally. We show that for some intercalants, no other structures should be observed while providing physical guidelines for identifying materials in which more complex structures may be realized.

Millman, Steven Edward

288

REVIEW ARTICLE: Property variation with shape in magnetic nanoelements  

NASA Astrophysics Data System (ADS)

Nanometre scale magnetic particles (`nanoelements' or `nanomagnets') form a rich and rapidly growing new area in condensed matter physics, with many potential applications in data storage technology and magnetic field sensing. This paper reviews an extensive study into the influence of shape on the properties of nanomagnets in the size range 35-500 nm. Elliptical, triangular, square, pentagonal and circular geometries have all been considered. It is shown that the size, thickness and geometric shape of nanomagnets all play a vital role in determining the magnetic properties. The shape, size and thickness of a nanomagnet are shown to be linked to its magnetic properties by two distinct phenomena. The first is called configurational anisotropy and describes the role played by small deviations from uniformity in the magnetization field within the nanostructures, which allow unexpected higher-order anisotropy terms to appear. These anisotropies can often dominate the magnetic properties. The second is the competition which exists between exchange energy and magnetostatic energy. This competition determines whether the nanomagnets exhibit single domain or incoherent magnetization and also controls the non-uniformities in magnetization which lead to configurational anisotropy. Understanding the influence of shape opens the way to designing new nanostructured magnetic materials where the magnetic properties can be tailored to a particular application with a very high degree of precision.

Cowburn, R. P.

2000-01-01

289

Surfactant-Assisted Preparation and Magnetic Properties of Iron-Based Nanowires  

NASA Astrophysics Data System (ADS)

Iron carbide Fe7C3 nanoparticles were prepared by decomposing pentacarbonyl complex precursors in a closed autoclave reactor. Spherical nanoparticles were obtained without adding polyethylene (10) octylphenyl ether (OP-10) as a surfactant. The addition of OP-10 induced the one-dimensional crystal growth to form the Fe7C3 nanowires. The iron metal nanowires obtained by reducing the above-mentioned carbide showed anisotropic magnetic properties with a saturated magnetization value of ˜180 emu/g.

Miura, Koji; Itoh, Masahiro; Machida, Ken-ichi

2008-04-01

290

Magnetic properties of polymer nanocomposites containing iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

The magnetic behavior of polymer nanocomposites containing nanoparticles (˜10 nm) of oxidized magnetite in a polyvinyl alcohol matrix were investigated by means of Mossbauer transmission and conversion electron spectroscopy and magnetic measurements. The obtained results show that the base concentration of iron oxide nanoparticles within the polymer matrix volume greatly influences the magnetic properties of nanocomposites. The estimated lamellar distribution of superparamagnetic Fe 3O 4 islands actuates the magnetic anisotropy formation in the investigated films.

Novakova, A. A.; Lanchinskaya, V. Yu.; Volkov, A. V.; Gendler, T. S.; Kiseleva, T. Yu.; Moskvina, M. A.; Zezin, S. B.

2003-03-01

291

The magnetic properties of potassium holmium double tungstate  

NASA Astrophysics Data System (ADS)

The magnetic investigations of potassium holmium double tungstate KHo(WO4)2 have been performed. The results of measurements of magnetic susceptibility and magnetization as a function of temperature (T from 0.3 K up to 100 K) and magnetic field (up to 1.5 T) are presented. A strong anisotropy of magnetic properties was found. The magnetic measurements data were used to calculate the interaction energy. It was shown that the interactions between nearest neighbors Ho3+ ions have antiferromagnetic character.

Borowiec, M. T.; Dyakonov, V. P.; Khatsko, E. N.; Zayarnyuk, T.; Zubov, E. E.; Szewczyk, A.; Gutowska, M. U.; Rykova, A. I.; PieTosa, J.; Majchrowski, A.; Michalski, E.; Hoffmann, J.-U.; Prokes, K.; Wo?niak, K.; Dobrzycki, ?.; Bara?ski, M.; Domukhovski, V.; Shtyrkhunova, V.; ?mija, J.; Szymczak, H.

2011-08-01

292

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

293

Magnetic properties of iron nanoparticles in mesoporous silica matrix  

NASA Astrophysics Data System (ADS)

Anisotropic iron nanoparticles were successfully synthesized within the pores of mesoporous silica matrix by intercalation of hydrophobic iron complex (Fe(CO) 5) into the hydrophobic part of the mesoporous silica-surfactant composite. It was shown that the particles are uniform and well ordered in the matrix and their shape and size are in good agreement with that of the pores. The samples demonstrate spin-glass-like behavior at low temperatures, which transforms to the superparamagnetic one with temperature increases. Nanoscale-related magnetic properties were investigated by polarized SANS. It was shown that hysteretic and the spin-glass-like behavior may be attributed to bunches of the iron nanowires with average radius of 4.7 nm.

Grigorieva, N. A.; Grigoriev, S. V.; Eckerlebe, H.; Eliseev, A. A.; Napolskii, K. S.; Lukashin, A. V.; Tretyakov, Yu. D.

2006-05-01

294

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

295

The Magnetic Properties Experiments on Mars Pathfinder  

Microsoft Academic Search

A remarkable result from the Viking missions was the discovery that the Martian soil is highly magnetic, in the sense that the soil is attracted by permanent magnets. Both the strong and weak magnets on the Viking landers were saturated with dust throughout the mission. Appropriate limits for the spontaneous magnetization sigma_S were advanced: 1 Am(2) (kg soil)(-1) < sigma_S

J. M. Knudsen; H. P. Gunnlaugsson; S. F. Hviid; M. B. Madsen

1996-01-01

296

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

297

Magnetoelectric Properties of Magnetic Tunneling Junctions  

Microsoft Academic Search

Magnetic tunneling junctions(MTJ's) consisting of two ferromagnetic layers separated by a thin insulating barrier show large tunnel magnetoresistive effects when the magnetizations of the ferromagnetic layers change their relative orientation from parallel to antiparallel in an applied field. Tunnel magneto resistance (TMR) is defined as the relative difference in tunnel resistance between parallel and antiparallel oriented magnetizations of electrodes. The

Shilpa Chava; Avishesh Dhakal; Wei Jiang Yeh

2007-01-01

298

Temperature dependence of magnetic properties of heat treated cobalt ferrite  

NASA Astrophysics Data System (ADS)

This study demonstrates the effectiveness of heat treatment in optimizing the magnetic properties of cobalt ferrite, compared to other methods such as cation substitution. It also shows how the magnetic properties of the heat treated cobalt ferrite vary under different temperature conditions. Saturation magnetization increased more due to heat treatment than due to Zn-substitution; a cation substitution that is known to result in high saturation magnetization in ferrites. A remarkable observation is that the increase in the saturation magnetization due to heat treatment was not at the expense of Curie temperature as was often reported for cation substituted materials. The observed variations in the magnetic properties were explained on the basis of cation redistribution arising as a result of the heat treatment.

Nlebedim, I. C.; Melikhov, Y.; Jiles, D. C.

2014-01-01

299

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.

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

2014-01-01

300

Magnetic properties of silica coated spindle-type hematite particles.  

PubMed

Magnetic properties of particles are generally determined from randomly oriented ensembles and the influence of the particle orientation on the magnetic response is neglected. Here, we report on the magnetic characterization of anisotropic spindle-type hematite particles. The easy axis of magnetization is within the basal plane of hematite, which is oriented perpendicular to the spindle axis. Two standard synthesis routes are compared and the effects of silica coating and particle orientation on the magnetic properties are investigated. Depending on the synthesis route we find fundamentally different magnetic behavior compatible with either single domain particles or superparamagnetic sub-units. Furthermore, we show that silica coating reduces the mean blocking temperature to nearly room temperature. The mechanical stress induced by the silica coating appears to reduce the magnetic coupling between the sub-units. PMID:21406920

Reufer, M; Dietsch, H; Gasser, U; Grobety, B; Hirt, A M; Malik, V K; Schurtenberger, P

2011-02-16

301

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

302

Magnetism in nanoparticles: tuning properties with coatings  

NASA Astrophysics Data System (ADS)

This paper reviews the effect of organic and inorganic coatings on magnetic nanoparticles. The ferromagnetic-like behaviour observed in nanoparticles constituted by materials which are non-magnetic in bulk is analysed for two cases: (a) Pd and Pt nanoparticles, formed by substances close to the onset of ferromagnetism, and (b) Au and ZnO nanoparticles, which were found to be surprisingly magnetic at the nanoscale when coated by organic surfactants. An overview of theories accounting for this unexpected magnetism, induced by the nanosize influence, is presented. In addition, the effect of coating magnetic nanoparticles with biocompatible metals, oxides or organic molecules is also reviewed, focusing on their applications.

Crespo, Patricia; de la Presa, Patricia; Marín, Pilar; Multigner, Marta; María Alonso, José; Rivero, Guillermo; Yndurain, Félix; María González-Calbet, José; Hernando, Antonio

2013-12-01

303

Measurement and modelling of magnetic properties of soft magnetic composite material under 2D vector magnetisations  

NASA Astrophysics Data System (ADS)

This paper reports the measurement and modelling of magnetic properties of SOMALOY TM 500, a soft magnetic composite (SMC) material, under different 2D vector magnetisations, such as alternating along one direction, circularly and elliptically rotating in a 2D plane. By using a 2D magnetic property tester, the B- H curves and core losses of the SMC material have been measured with different flux density patterns on a single sheet square sample. The measurements can provide useful information for modelling of the magnetic properties, such as core losses. The core loss models have been successfully applied in the design of rotating electrical machines with SMC core.

Guo, Y. G.; Zhu, J. G.; Zhong, J. J.

2006-07-01

304

Surface controlled magnetic properties of Fe3O4 nanoparticles  

NASA Astrophysics Data System (ADS)

To understand the influence of surface organic-inorganic interactions on the magnetic properties of magnetic nanoparticles, magnetite (Fe3O4) of mean size 4-16 nm (standard deviation ? <= 15 %) are synthesized by three different thermolysis techniques. The surface functionality is controlled through either amine or amine-acid both taking as surfactant for Fe3O4 nanoparticles synthesis. Magnetic investigations revealed that samples prepared using amine as a multifunctional agent (only one surfactant) shows superior magnetic properties than the nanoparticles produced by the approach utilizing oleic acid and oleylamine.

Mohapatra, Jeotikanta; Mitra, Arijit; Bahadur, D.; Aslam, M.

2013-02-01

305

Molecular properties of ciprofloxacin-indion 234 complexes  

Microsoft Academic Search

The purpose of this research was to formulate tasteless complexes of ciprofloxacin with Indion 234 and to evaluate molecular\\u000a properties of drug complexes. The effect of batch and column process, complexation time, temperature, and pH on ciprofloxacin\\u000a loading on Indion 234 is reported. Drug resin complexes (DRC) were characterized by infrared spectroscopy, thermal analysis,\\u000a and x-ray diffraction pattern. Ciprofloxacin release

Sambhaji Pisal; Rana Zainnuddin; Pradeep Nalawade; Kakasaheb Mahadik; Shivajirao Kadam

2004-01-01

306

Modeling of magnetic properties of polymer bonded Nd–Fe–B magnets with surface modifications  

Microsoft Academic Search

The effects of surface modification on the magnetic properties of polymer-bonded Nd–Fe–B magnets have been studied. Two sets of Nd–Fe–B powders, coated and uncoated, were blended and compression molded with polyphenylene sulfide in isotropic form. Their magnetic properties were measured using a Helmholtz coil and a SQUID. The results showed that the effect of the coating significantly improved the irreversible

Jun Xiao; Joshua U Otaigbe; David C Jiles

2000-01-01

307

Magnetic properties and large coercivity of MnxGa nanostructures  

NASA Astrophysics Data System (ADS)

To investigate structure-property correlations, high-coercivity MnxGa nanoparticles were synthesized by the method of sequential deposition of Ga and Mn fluxes using molecular beam epitaxy. Spontaneous nanostructuring was assisted by the use of an Au precursor and thermal annealing, and the growth properties, structure and magnetic properties were characterized. Atomic force microscopy revealed average particle dimensions of 100 nm and X-ray diffraction revealed a dominant tetragonal D022 crystal structure. Magnetic characterization at room temperature identified the presence of two magnetic phases, dominated by a high-coercivity (2.3 T) component in addition to a low-coercivity component.

Jamer, M. E.; Assaf, B. A.; Bennett, S. P.; Lewis, L. H.; Heiman, D.

2014-05-01

308

Properties of Complex Inorganic Solids 2.  

National Technical Information Service (NTIS)

The triennial International Alloy Conferences (IACs) aim at the identification and promotion of the common elements developed in the study, either experimental, phenomenological, or theoretical and computational, of materials properties across materials t...

A. Gonis A. Meike K. Rajan P. E. Turchi

2000-01-01

309

Magnetism in organic ion radical salts and complexes based on nitronyl nitroxide  

Microsoft Academic Search

In order to study effects of magnetic and non-magnetic counter ions on the magnetism in organic radical crystals, alkali metal and transition metal salts of carboxylatofuryl nitronyl nitroxide were synthesized. Guanidinium sulfonatofuryl nitronyl nitroxide complex was also prepared and compared its magnetism with that of the sodium salt. Magnetization measurements reveal that ferromagnetic intermolecular interaction, which is coexistent with antiferromagnetic

T. Sugano; P. Day

1999-01-01

310

Synthesis and complex magnetic susceptibility characterization of magnetic fluids in different liquid carriers  

NASA Astrophysics Data System (ADS)

Kerosene, isopar M, and mineral oil based magnetic fluids were prepared. The magnetite nanoparticles have spherical shapes and a mean diameter of 10.2+/-3.2 nm. The complex magnetic susceptibility ?(?)=?'(?)-i?''(?) of the magnetic fluids was measured using the transmission line technique applying dc magnetic fields over the range 0-1212 Oe over the frequency range 70 MHz-6 GHz, where resonance and relaxation are present. The resonance frequency fres defined as the frequency at which ?'(?) goes from positive to negative values ranges from 2.1 to 5.4 GHz. The maximum frequency fmax defined as the frequency at which maximum absorption occurs in ?''(?) ranges from 1.2 to 4.8 GHz. Anisotropy fields values were also determined.

Ayala Valenzuela, O.; Matutes Aquino, J.; Betancourt Galindo, R.; Rodríguez Fernández, O.; Fannin, P. C.; Giannitsis, A. T.

2005-05-01

311

Structural properties of magnetic Heusler alloys  

Microsoft Academic Search

Magnetically driven actuator materials, such as the ternary and intermetallic Heusler alloys with composition 0953-8984\\/11\\/8\\/014\\/img7, are studied within the density-functional theory (DFT) with the generalized gradient approximation (GGA) for the electronic exchange and correlation. The geometrical and electronic structures for the magnetic 0953-8984\\/11\\/8\\/014\\/img8 structure are calculated. The structures and magnetic moments at equilibrium are in good agreement with the experimental

A. Ayuela; J. Enkovaara; K. Ullakko; R. M. Nieminen

1999-01-01

312

Dynamics of dust-ion acoustic shock waves in a magnetized charge variable superthermal complex plasma  

NASA Astrophysics Data System (ADS)

A theoretical investigation is carried out to study the characteristic properties of dust-ion acoustic (DIA) shock waves in a magnetized, charge varying, complex (dusty) plasma which consists of immobile dust grains, fluid ions and superthermal electrons. The effects of collisions are not included here, but the dissipation leading to the formation of stable shock structures is provided by the dust charge fluctuations. The Korteweg–de Vries–Burgers (KdV–Burgers) equation is derived using the reductive perturbation technique. The combined effects of obliqueness, magnitude of the magnetic field, and electron superthermality on the DIA shock waves are then investigated. It is shown that the effects of obliqueness, electron non-thermality and dust charge fluctuation significantly modify the basic properties of DIA shock waves.

Shahmansouri, Mehran

2014-07-01

313

Dysprosium complexes and their micelles as potential bimodal agents for magnetic resonance and optical imaging.  

PubMed

Six diethylene triamine pentaacetic acid (DTPA) bisamide derivatives functionalized with p-toluidine (DTPA-BTolA), 6-aminocoumarin (DTPA-BCoumA), 1-naphthalene methylamine (DTPA-BNaphA), 4-ethynylaniline (DTPA-BEthA), p-dodecylaniline (DTPA-BC12PheA) and p-tetradecyl-aniline (DTPA-BC14PheA) were coordinated to dysprosium(III) and the magnetic and optical properties of the complexes were examined in detail. The complexes consisting of amphiphilic ligands (DTPA-BC12PheA and DTPA-BC14PheA) were further assembled into mixed micelles. Upon excitation into the ligand levels, the complexes display characteristic Dy(III) emission with quantum yields of 0.3-0.5% despite the presence of one water molecule in the first coordination sphere. A deeper insight into the energy-transfer processes has been obtained by studying the photophysical properties of the corresponding Gd(III) complexes. Since the luminescence quenching effect is decreased by the intervention of non-ionic surfactant, quantum yields up to 1% are obtained for the micelles. The transverse relaxivity r2 per Dy(III) ion at 500 MHz and 310 K reaches a maximum value of 27.4 s(-1) mM(-1) for Dy-DTPA-BEthA and 36.0 s(-1) mM(-1) for the Dy-DTPA-BC12PheA assemblies compared with a value of 0.8 s(-1) mM(-1) for Dy-DTPA. The efficient T2 relaxation, especially at high magnetic field strengths, is sustained by the high magnetic moment of the dysprosium ion, the coordination of water molecules with slow water exchange kinetics and long rotational correlation times. These findings open the way to the further development of bimodal optical and magnetic resonance imaging probes starting from single lanthanide compounds. PMID:24123216

Debroye, Elke; Laurent, Sophie; Vander Elst, Luce; Muller, Robert N; Parac-Vogt, Tatjana N

2013-11-18

314

Novel multifunctional nanocomposites: magnetic mesoporous silica nanospheres covalently bonded with near-infrared luminescent lanthanide complexes.  

PubMed

In this paper, we report the fabrication and characterization of magnetic mesoporous silica nanospheres covalently bonded with near-infrared (NIR) luminescent lanthanide complexes [denoted as Ln(DBM)(3)phen-MMS (Ln = Nd, Yb)]. Ln(DBM)(3)phen-MMS (Ln = Nd, Yb) nanospheres with an average size of 80-130 nm were synthesized via incorporation of the chelate ligand 5-[N,N-bis-3-(triethoxysilyl)propyl]ureyl-1,10-phenanthroline (phen-Si) into the framework of magnetic mesoporous silica (denoted as phen-MMS), followed by introduction of the Ln(DBM)(3)(H(2)O)(2) (Ln = Nd, Yb) complexes into the nanocomposites via a ligand exchange reaction. The morphological, structural, textural, magnetic, and NIR luminescent properties were well-characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), N(2) adsorption-desorption, a superconducting quantum interference device (SQUID), and photoluminescence spectra. These nanocomposites, which possess high surface area, high pore volume, and well-defined pore size, exhibit two-dimensional hexagonal (P6mm) mesostructures. After ligand-mediated excitation, Ln(DBM)(3)phen-MMS (Ln = Nd, Yb) nanocomposites exhibit the characteristic NIR emission of Nd(3+) and Yb(3+), respectively. Magnetic measurements reveal that these mulfunctional nanocomposites possess superparamagnetic properties at 300 K. The high magnetization values make the nanocomposites respond to the external magnetic field quickly. Additionally, the results indicate that Nd(DBM)(3)phen-MMS nanocomposites may have potential applications for laser systems or the optical amplifiers operating at 1.3 microm and Yb(DBM)(3)phen-MMS nanocomposites have several advantages for potential applications in drug delivery or optical imaging. PMID:19886634

Feng, Jing; Song, Shu-Yan; Deng, Rui-Ping; Fan, Wei-Qiang; Zhang, Hong-Jie

2010-03-01

315

Complex windmill transformation producing new purely magnetic fluids  

NASA Astrophysics Data System (ADS)

Minimal complex windmill transformations of G2IB(ii) spacetimes (admitting a two-dimensional Abelian group of motions of the so-called Wainwright B(ii) class) are defined and the compatibility with a purely magnetic Weyl tensor is investigated. It is shown that the transformed spacetimes cannot be perfect fluids or purely magnetic Einstein spaces. We then determine which purely magnetic perfect fluids (PMpfs) can be windmill-transformed into purely magnetic anisotropic fluids (PMafs). Assuming separation of variables, complete integration produces two, algebraically general, G2I-B(ii) PMpfs: a solution with zero 4-acceleration vector and spatial energy-density gradient, previously found by the authors, and a new solution in terms of Kummer's functions, where these vectors are aligned and non-zero. The associated windmill PMafs are rotating but non-expanding. Finally, an attempt to relate the spacetimes to each other by a simple procedure leads to a G2I-B(ii) one-parameter PMaf generalization of the previously found metric.

Lozanovski, C.; Wylleman, L.

2011-04-01

316

Comparison of Microinstability Properties for Stellarator Magnetic Geometries  

SciTech Connect

The microinstability properties of seven distinct magnetic geometries corresponding to different operating and planned stellarators with differing symmetry properties are compared. Specifically, the kinetic stability properties (linear growth rates and real frequencies) of toroidal microinstabilities (driven by ion temperature gradients and trapped-electron dynamics) are compared, as parameters are varied. The familiar ballooning representation is used to enable efficient treatment of the spatial variations along the equilibrium magnetic field lines. These studies provide useful insights for understanding the differences in the relative strengths of the instabilities caused by the differing localizations of good and bad magnetic curvature and of the presence of trapped particles. The associated differences in growth rates due to magnetic geometry are large for small values of the temperature gradient parameter n identical to d ln T/d ln n, whereas for large values of n, the mode is strongly unstable for all of the different magnetic geometries.

G. Rewoldt; L.-P. Ku; W.M. Tang

2005-06-16

317

Magnetic Anomalies and Rock Magnetic Properties Related to Deep Crustal Rocks of the Athabasca Granulite Terrane, Northern Canada  

NASA Astrophysics Data System (ADS)

The Athabasca granulite terrane in northernmost Saskatchewan, Canada is an exceptional exposure of lower crustal rocks having experienced several high temperature events (ca 800C) during a prolonged period of deep-crustal residence (ca 1.0 GPa) followed by uplift and exhumation. With little alteration since 1.8 Ga these rocks allow us to study ancient lower crustal lithologies. Aeromagnetic anomalies over this region are distinct and complex, and along with other geophysical measurements, define the Snowbird Tectonic zone, stretching NE-SW across northwestern Canada, separating the Churchill province into the Hearne (mid-crustal rocks, amphibolite facies) from the Rae (lower crust rocks, granulite facies). Distinct magnetic highs and lows appear to relate roughly to specific rock units, and are cut by mapped shear zones. Over fifty samples from this region, collected from the major rock types, mafic granulites, felsic granulites, granites, and dike swarms, as well as from regions of both high and low magnetic anomalies, are being used to investigate magnetic properties. The intention is to investigate what is magnetic in the lower crust and how it produces the anomalies observed from satellite measurements. The samples studied reveal a wide range of magnetic properties with natural remanent magnetization ranging from an isolated high of 38 A/m to lows of 1 mA/m. Susceptibilities also range over several orders of magnitude, from 1 to 1 x10-4 SI. Magnetite is identified in nearly all samples using both low and high temperature measurements, but concentrations are generally very low. Hysteresis properties on 41 samples reveal nearly equal numbers of samples represented by PSD and MD grains, with a few samples (N=6) plotting in or close to the SD region. Low temperature measurements indicate that most samples contain magnetite, showing a marked Verway transition around 120K. Also identified in nearly half of the samples is pyrrhotite, noted by low temperature transitions at 30-35K. Preliminary results indicate that the same general lithologies can have very different magnetic properties with varying concentrations of magnetic minerals and with widely varying domain sizes and thus magnetic behavior. Additional work is needed to fully understand the magnetic signature causing the aeromagnetic anomalies, but with this information we will be able to better understand the varying rock types, compositions, and exposures in lower crustal rocks, be able to predict anomaly patterns, and eventually better understand the geologic history of this complex area.

Brown, L. L.; Williams, M. L.

2010-12-01

318

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.

Nishida, Keiji; Silver, Pamela A.

2012-01-01

319

Bimetallic anionic formyl complexes: synthesis and properties  

Microsoft Academic Search

Three bimetallic anionic complexes, (2) lithium + dimanganese nonacarbonyl formyl⁻, (3) lithium + rhenium manganese nonacarbonyl formyl⁻, 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

Wilson Tam; Marianne Marsi; J. A. Gladysz

1983-01-01

320

Structural and electronic dependence of the single-molecule-magnet behavior of dysprosium(III) complexes.  

PubMed

We investigate and compare the magnetic properties of two isostructural Dy(III)-containing complexes. The Dy(III) ions are chelated by hexadentate ligands and possess two apical bidendate nitrate anions. In dysprosium(III) N,N'-bis(imine-2-yl)methylene-1,8-diamino-3,6-dioxaoctane (1), the ligand's donor atoms are two alkoxo, two pyridine, and two imine nitrogen atoms. Dysprosium(III) N,N'-bis(amine-2-yl)methylene-1,8-diamino-3,6-dioxaoctane (2) is identical with 1 except for one modification: the two imine groups have been replaced by amine groups. This change has a minute effect on the structure and a larger effect the magnetic behavior. The two complexes possess slow relaxation of the magnetization in the presence of an applied field of 1000 Oe but with a larger barrier for reorientation of the magnetization for 1 (Ueff/kB = 50 K) than for 2 (Ueff/kB = 34 K). First-principles calculations using the spin-orbit complete active-space self-consistent-field method were performed and allowed to fit the experimental magnetization data. The calculations gave the energy spectrum of the 2J + 1 sublevels issued from the J = 15/2 free-ion ground state. The lowest-lying sublevels were found to have a large contribution of MJ = ±15/2 for 1, while for 2, MJ = ±13/2 was dominant. The observed differences were attributed to a synergistic effect between the electron density of the ligand and the small structural changes provoked by a slight alteration of the coordination environment. It was observed that the stronger ligand field (imine) resulted in complex 1 with a larger energy barrier for reorientation of the magnetization than 2. PMID:24533673

Campbell, Victoria E; Bolvin, Hélène; Rivière, Eric; Guillot, Regis; Wernsdorfer, Wolfgang; Mallah, Talal

2014-03-01

321

Fabrication and properties of QMG coil magnets  

Microsoft Academic Search

QMG is a high Jc bulk material, which consists of single crystalline 123 with finely dispersed 211. A QMG coil magnet is proposed as a high field application of oxide bulk high Tc superconductors (HTS). Since the QMG is produced in the form of a single crystal bulk, it has been considered difficult to make a coil shaped magnet by

M. Morita; M. Kumada; A. Sato; H. Teshima; H. Hirano

2007-01-01

322

Magnetic properties and thermal stability of MnBi/NdFeB hybrid bonded magnets  

NASA Astrophysics Data System (ADS)

Magnetic properties and thermal stability were investigated for the MnBi/NdFeB (MnBi = 0, 20, 40, 60, 80, and 100 wt.%) bonded hybrid magnets prepared by spark plasma sintering (SPS) technique. Effect of MnBi content on the magnetic properties of the hybrid magnets was studied. With increasing MnBi content, the coercivity of the MnBi/NdFeB hybrid magnets increases rapidly, while the remanence and maximum energy product drops simultaneously. Thermal stability measurement on MnBi magnet, NdFeB magnet, and the hybrid magnet with 20 wt.% MnBi indicates that both the NdFeB magnet and the MnBi/NdFeB hybrid magnet have a negative temperature coefficient of coercivity, while the MnBi magnet has a positive one. The (BH)max of the MnBi/NdFeB magnet (MnBi = 20 wt.%) is 5.71 MGOe at 423 K, which is much higher than 3.67 MGOe of the NdFeB magnet, indicating a remarkable improvement of thermal stability.

Cao, S.; Yue, M.; Yang, Y. X.; Zhang, D. T.; Liu, W. Q.; Zhang, J. X.; Guo, Z. H.; Li, W.

2011-04-01

323

Magnetic properties and thermal stability of MnBi/NdFeB hybrid bonded magnets  

SciTech Connect

Magnetic properties and thermal stability were investigated for the MnBi/NdFeB (MnBi = 0, 20, 40, 60, 80, and 100 wt.%) bonded hybrid magnets prepared by spark plasma sintering (SPS) technique. Effect of MnBi content on the magnetic properties of the hybrid magnets was studied. With increasing MnBi content, the coercivity of the MnBi/NdFeB hybrid magnets increases rapidly, while the remanence and maximum energy product drops simultaneously. Thermal stability measurement on MnBi magnet, NdFeB magnet, and the hybrid magnet with 20 wt.% MnBi indicates that both the NdFeB magnet and the MnBi/NdFeB hybrid magnet have a negative temperature coefficient of coercivity, while the MnBi magnet has a positive one. The (BH){sub max} of the MnBi/NdFeB magnet (MnBi = 20 wt.%) is 5.71 MGOe at 423 K, which is much higher than 3.67 MGOe of the NdFeB magnet, indicating a remarkable improvement of thermal stability.

Cao, S.; Yue, M.; Yang, Y. X.; Zhang, D. T.; Liu, W. Q.; Zhang, J. X. [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China); Guo, Z. H.; Li, W. [Division of Functional Materials, Central Iron and Steel Research Institute, Beijing, 100081 (China)

2011-04-01

324

Magnetic properties of ?-Fe 2O 3 nanowires  

Microsoft Academic Search

Some basic magnetic properties of ?-Fe2O3 nanowires synthesized by oxygenating pure iron are reported. The blocking temperature of the nanowires is 120K, where the field-cooled and zero-field-cooled magnetization curves diverge, and the hysteresis loops vary notably with temperature. No evidence for Morin transition is found in the temperature range 4–300K. In addition, the magnetic behavior below 50K shows a further

Y. Y. Xu; X. F. Rui; Y. Y. Fu; H. Zhang

2005-01-01

325

Magnetic properties of [alpha]Fe2O3 nanowires  

Microsoft Academic Search

Some basic magnetic properties of [alpha]-Fe2O3 nanowires synthesized by oxygenating pure iron are reported. The blocking temperature of the nanowires is 120 K, where the field-cooled and zero-field-cooled magnetization curves diverge, and the hysteresis loops vary notably with temperature. No evidence for Morin transition is found in the temperature range 4-300 K. In addition, the magnetic behavior below 50 K

Y. Y. Xu; X. F. Rui; Y. Y. Fu; H. Zhang

2005-01-01

326

Enhanced magnetic-field-induced optical properties of nanostructured magnetic fluids by doping nematic liquid crystals  

PubMed Central

Ferronematic materials composed of 4-cyano-4?-pentylbiphenyl nematic liquid crystal and oil-based Fe3O4 magnetic fluid were prepared using ultrasonic agitation. The birefringence (?n) and figure of merit of optical properties (Q?=??n/?, where ? is the extinction coefficient) of pure magnetic fluids and the as-prepared ferronematic materials were examined and compared. The figure of merit of optical properties weighs the birefringence and extinction of the materials and is more appropriate to evaluate their optical properties. Similar magnetic-field- and magnetic-particle-concentration-dependent properties of birefringence and figure of merit of optical properties were obtained for the pure magnetic fluids and the ferronematic materials. For the ferronematic materials, the values of Q increase with the volume fractions of nematic liquid crystal under certain fixed field strength and are larger than those of their corresponding pure magnetic fluids at high field region. In addition, the enhancement of Q value increases monotonously with the magnetic field and becomes remarkable when the applied magnetic field is beyond 50 mT. The maximum relative enhanced value of QR exceeds 6.8% in our experiments. The results of this work may conduce to extend the pragmatic applications of nanostructured magnetic fluids in optical field.

2012-01-01

327

The structural properties of transition metal hydrogen complexes in silicon  

Microsoft Academic Search

A first-principles spin-polarised local density functional cluster method is used to explore the structural and vibrational properties of several substitutional transition-metal impurities complexed with hydrogen.

A. Resende; R. Jones; S. Öberg; P. R. Briddon

1999-01-01

328

Low temperature magnetic properties of a molecular compound (abstract)  

Microsoft Academic Search

In molecular compounds, the magnetic properties depend on the coupling between the magnetic moments of transition metal ions, rare earth ions, and\\/or free radicals. This coupling is often antiferromagnetic, but can give a high spin moment in some particular cases. When organic molecules form crystals, again the coupling between molecules can be antiferromagnetic or ferromagnetic like. In a few cases

J. L. Tholence; M. Novak; D. Luneau; P. Rey; E. Belorisky

1996-01-01

329

Magnetic properties of enstatite chondrites and iron bearing sulfides  

Microsoft Academic Search

A b s t r a c t : Magnetic properties of 15 enstatite chondrites (EH and EL of petro- graphic types 3-6) were investigated in the temperature range 5-300 K. Room temperature hysteresis loops of all 15 meteorites show low coercivities (? 100 mT) indicating a coarse grained MD (Multi Domain) kamacite (?5% Ni) to be a dominant magnetic

T. Kohout; A. Kosterov; J. Haloda; P. Tycova

330

Magnetic properties of the UNS S39205 duplex stainless steel  

Microsoft Academic Search

Duplex stainless steels (DSS) present a fine microstructure of paramagnetic austenite and ferromagnetic ferrite. In this work the microstructures of UNS S39205 (old S31803) duplex stainless steel (DSS) samples were modified by high temperature treatment at 1300°C in vacuum followed by four different cooling rates and thermal aging at 475°C for three different times. Magnetic properties (saturation magnetization, remanence, coercive

S. S. M Tavares; P. D. S Pedrosa; J. R Teodósio; M. R da Silva; J. M Neto; S Pairis

2003-01-01

331

Magnetic properties of tunicate blood cells. II. Ascidia ceratodes  

Microsoft Academic Search

The magnetic properties of intact blood cells of the tunicate Ascidia ceratodes have been measured up to 50 kOe with a SQUID susceptometer. Analysis of total metal contents by plasma emission spectroscopy and V(IV) content by epr indicates that approximately 5% of the accumulated vanadium is +4 vanadyl ion. Measured values of the magnetic moment MP at different values of

Kenneth Kustin; William E. Robinson; Richard B. Frankel; K. Spartalian

1996-01-01

332

Anisotropic magnetic properties of obliquely deposited Ni films  

Microsoft Academic Search

Magnetic properties of evaporated nickel films, deposited onto 75 µm thick 300 H Kapton substrates by evaporation at oblique off-normal angles of incidence, a were investigated by SQUID magnetometry. We found that, in the film plane, the direction of easy magnetization lay perpendicular to the incidence plane for films deposited at a s, the easy axis changed to the direction

T. Otiti

2004-01-01

333

Electrical and Magnetic Properties of D6ac Steel.  

National Technical Information Service (NTIS)

The room temperature electrical and magnetic properties of the high strength steel D6ac are documented in this report. These data were used to support a wider study on the application of magnetic rubber testing (MRT) for the structural integrity managemen...

M. E. Ibrahim S. K. Burke

2007-01-01

334

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

335

Magnetic properties of some rare earth tellurate garnets  

NASA Astrophysics Data System (ADS)

The magnetic properties of the lanthanide tellurate garnets Ln3Te2Li3O12 for Ln=Pr, Nd, Gd Er, and Yb are found to exhibit similarities in many cases to the related aluminum or gallium garnet compounds. Magnetic exchange is also roughly comparable in magnitude, despite the systematic difference in exchange pathways.

Applegate, Ryan P.; Zong, Yuhua; Corruccini, L. R.

2007-09-01

336

Local magnetic properties of a monolayer of Mn12 single molecule magnets.  

PubMed

The magnetic properties of a monolayer of Mn12 single molecule magnets grafted onto a silicon (Si) substrate have been investigated using depth-controlled beta-detected nuclear magnetic resonance. A low-energy beam of spin-polarized radioactive 8Li was used to probe the local static magnetic field distribution near the Mn12 monolayer in the Si substrate. The resonance line width varies strongly as a function of implantation depth as a result of the magnetic dipolar fields generated by the Mn12 electronic magnetic moments. The temperature dependence of the line width indicates that the magnetic properties of the Mn12 moments in this low-dimensional configuration differ from bulk Mn12. PMID:17488049

Salman, Z; Chow, K H; Miller, R I; Morello, A; Parolin, T J; Hossain, M D; Keeler, T A; Levy, C D P; MacFarlane, W A; Morris, G D; Saadaoui, H; Wang, D; Sessoli, R; Condorelli, G G; Kiefl, R F

2007-06-01

337

Structural inhomogeneity and magnetic properties of strontium hexaferrites  

Microsoft Academic Search

of solids and opens new possibilities for controlling their properties. These investigations were made for the purpose of establishment of the relationship between clusterization and magnetic properties of SrO.nFe203, where 5.4< n< 6.2, metal oxide magnetically hard strontium ferrites. The anisotropic strontium ferrites were produced from SrCO 3 and iron oxide produced by Western Siberia Combine using the optimum ceramic

V. P. Pashchenko; Z. A. Samoilenko; V. M. Vintonyak; V. I. Ivanova; E. I. Pushenko; I. F. Klochai; I. F. Gribanov

1995-01-01

338

Lithological discrimination and correlation in oil sands using rock magnetic properties  

SciTech Connect

The Lower Cretaceous McMurray Formation, which contains most of the bitumen reserves of the Athabasca oil sands, comprises uncemented quartz sands with siltstone, shale, and local ironstones. The sequential fluvial, estuarine, and marine depositional environments of the McMurray drainage basin have resulted in the complex juxtaposition of differing lithofacies. Horizontal continuity of lithofacies is limited. Sand body geometries are many and varied. Prediction of sand body geometry has important economic applications; a strong positive correlation exists between sand facies and oil grade. An investigation of the magnetic property variations in specimens from five closely adjacent boreholes within the McMurray Formation has shown that it is possible to: (1) document objective magnetic property parameters to differentiate distinct lithological units; (2) use these same magnetic parameters to establish between borehole lithostratigraphic correlations; and (3) to show that the magnitude of some magnetic parameters bears a direct relationship to the oil content of a lithology.

Morris, W.A. (McMaster Univ., Hamilton, Ontario (Canada))

1991-03-01

339

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

340

Magnetic Properties of 1:2 Mixed Cobalt(II) Salicylaldehyde Schiff-Base Complexes with Pyridine Ligands Carrying High-Spin Carbenes (Scar = 2/2, 4/2, 6/2, and 8/2) in Dilute Frozen Solutions: Role of Organic Spin in Heterospin Single-Molecule Magnets.  

PubMed

The 1:2 mixtures of Co(p-tolsal)2, p-tolsal = N-p-tolylsalicylideniminato, and diazo-pyridine ligands, DXpy; X = 1, 2, 3l, 3b, and 4, in MTHF solutions were irradiated at cryogenic temperature to form the corresponding 1:2 cobalt-carbene complexes Co(p-tolsal)2(CXpy)2, with Stotal = 5/2, 9/2, 13/2, 13/2, and 17/2, respectively. The resulting Co(p-tolsal)2(CXpy)2, X = 1, 2, 3l, 3b, and 4, showed magnetic behaviors characteristic of heterospin single-molecule magnets with effective activation barriers, Ueff/kB, of 40, 65, 73, 72, and 74 K, for reorientation of the magnetic moment and temperature-dependent hysteresis loops with a coercive force, Hc, of ?0, 6.2, 10, 6.5, and 9.0 kOe at 1.9 K, respectively. The relaxation times, ?Q, due to a quantum tunneling of magnetization (QTM) were estimated to be 1.6 s for Co(p-tolsal)2(C1py)2, ?2.0 × 10(3) s for Co(p-tolsal)2(C2py)2, and >10(5) s for Co(p-tolsal)2(CXpy)2; X = 3b, 3l, and 4. In heterospin complexes, organic spins, carbenes interacted with the cobalt ion to suppress the QTM pathway, and the ?Q value increased with increasing the Stotal values. PMID:24816331

Karasawa, Satoru; Nakano, Kimihiro; Yoshihara, Daisuke; Yamamoto, Noriko; Tanokashira, Jun-Ichi; Yoshizaki, Takahito; Inagaki, Yuji; Koga, Noboru

2014-06-01

341

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

342

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

343

Exotic Magnetic Properties in {sup 17}C  

SciTech Connect

Magnetic dipole transitions in {sup 17}C are investigated by shell model calculations. The important role of the tensor interaction for magnetic dipole transitions in this exotic neutron-rich nucleus is pointed out. The recently observed anomalous quenching of the magnetic dipole transition in 1/2{sub 1}{sup +} {yields}3/2{sub g.s.}{sup +} is shown to be well explained by using a modified shell model Hamiltonian that takes full account of the tensor force and monopole corrections in the isospin T=1 channel. The predicted quadrupole moment of {sup 17}C is smaller than the value obtained by conventional shell model Hamiltonians.

Suzuki, Toshio; Otsuka, Takaharu [Department of Physics, College of Humanities and Sciences, Nihon University Sakurajosui 3-25-40, Setagaya-ku, Tokyo 156-8550, Japan and Center for Nuclear Study, University of Tokyo, Hirosawa, Wako-shi, Saitama 351-0198 (Japan); Department of Physics and Center for Nuclear Study, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan and RIKEN, Hirosawa, Wako-shi, Saitama 351-0198 (Japan)

2008-12-15

344

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

345

ERRATUM: Magnetic and caloric properties of magnetic nanoparticles: an equilibrium study  

NASA Astrophysics Data System (ADS)

In the article 'Magnetic and caloric properties of magnetic nanoparticles: an equilibrium study', we discuss thermal equilibrium properties of non-interacting magnetically anisotropic nanoparticles. Some of the results related to ?0, ?2 and caloric properties are discussed earlier by J L García-Palacios in his classic article 'On the statics and dynamics of magneto-anisotropic nanoparticles' [1]. If someone is interested in this topic they should consult the article of J L García-Palacios [1]. References [1] J L García-Palacios 2000 Advances in Chemical Physics vol 112, ed I Priogogine and Stuart A Rice (New York: Wiley) 1

Bandyopadhyay, M.; Bhattacharya, J.

2008-04-01

346

Properties of Magnetized Quark-Hybrid Stars  

Microsoft Academic Search

The structure of a magnetized quark-hybrid stars (QHS) is modeled using a standard relativistic mean-field equation of state (EoS) for the description of hadronic matter. For quark matter we consider a bag model EoS which is modified perturbatively to account for the presence of a uniform magnetic field. The mass-radius (M-R) relationship, gravitational redshift and rotational Kepler periods of such

M. Orsaria; Ignacio F. Ranea-Sandoval; H. Vucetich; F. Weber

2011-01-01

347

Interweaving spins with their environment: novel inorganic nanohybrids with controllable magnetic properties.  

PubMed

We discuss current developments in the synthesis and characterization of magnetic nanohybrids made of molecular magnets and nanostructured materials. We first review several novel approaches that have recently been attempted to combine magnetic coordination complexes with differently-obtained inorganic systems. Special focus is placed on how the altered environment can affect the magnetic properties of single molecules, providing new routes to multifunctional devices based on hybrid magnetic nanosystems. We then show how this approach is opening new outlooks towards the control of nanomagnets using external stimuli (e.g. photons, electrons, etc.) and for the creation of ultra-sensitive devices. Eventually we provide a unified vision of the area, with a personal perspective on the main goals currently at stake and of possible future developments. PMID:24514949

Cervetti, Christian; Heintze, Eric; Bogani, Lapo

2014-03-21

348

Effect of Cadmium Substitution on Structural and Magnetic Properties of Nano Sized Nickel Ferrite  

NASA Astrophysics Data System (ADS)

The structure and crystal phase of the nanocrystalline powders of Ni1-xCdxFe2O4 (0<=x<=0.5) mixed ferrite, synthesized by wet chemical co-precipitation method, were characterized by X-ray diffraction. Results showed that the lattice parameter increased with increasing Cd concentration. Microstructure was studied by scanning electron microscopy. TG/DTA studies were carried out on co-precipitated sulphate complexes. These studies revealed the low ferritization temperature (650 °C) of the ferrite system synthesized by presently adopted route of synthesis and occurrence of simultaneous decomposition and ferritization processes. Further studies by infrared spectroscopy were also conducted. Moreover, magnetic properties of the prepared nanoparticles were studied by magnetization and a.c. susceptibility measurements. The response of prepared Ni1-xCdxFe2O4 mixed ferrites to magnetic field was investigated. Results show that, magnetic susceptibility, Curie temperature, and effective magnetic moment decreased as the Cd content increases.

Pralhadrao Jadhav, Sanjay; Ghanshamji Toksha, Bhagwan; Marutirao Jadhav, Kamalakar; Dadarao Shinde, Narayan

2010-08-01

349

In Vivo Display of a Multisubunit Enzyme Complex on Biogenic Magnetic Nanoparticles? †  

PubMed Central

Magnetosomes are unique bacterial organelles comprising membrane-enveloped magnetic crystals produced by magnetotactic bacteria. Because of several desirable chemical and physical properties, magnetosomes would be ideal scaffolds on which to display highly complicated biological complexes artificially. As a model experiment for the functional expression of a multisubunit complex on magnetosomes, we examined the display of a chimeric bacterial RNase P enzyme composed of the protein subunit (C5) of Escherichia coli RNase P and the endogenous RNA subunit by expressing a translational fusion of C5 with MamC, a known magnetosome protein, in the magnetotactic bacterium Magnetospirillum gryphiswaldense. As intended, the purified C5 fusion magnetosomes, but not wild-type magnetosomes, showed apparent RNase P activity and the association of a typical bacterial RNase P RNA. Our results demonstrate for the first time that magnetosomes can be employed as scaffolds for the display of multisubunit complexes.

Ohuchi, Shoji; Schuler, Dirk

2009-01-01

350

In vivo display of a multisubunit enzyme complex on biogenic magnetic nanoparticles.  

PubMed

Magnetosomes are unique bacterial organelles comprising membrane-enveloped magnetic crystals produced by magnetotactic bacteria. Because of several desirable chemical and physical properties, magnetosomes would be ideal scaffolds on which to display highly complicated biological complexes artificially. As a model experiment for the functional expression of a multisubunit complex on magnetosomes, we examined the display of a chimeric bacterial RNase P enzyme composed of the protein subunit (C5) of Escherichia coli RNase P and the endogenous RNA subunit by expressing a translational fusion of C5 with MamC, a known magnetosome protein, in the magnetotactic bacterium Magnetospirillum gryphiswaldense. As intended, the purified C5 fusion magnetosomes, but not wild-type magnetosomes, showed apparent RNase P activity and the association of a typical bacterial RNase P RNA. Our results demonstrate for the first time that magnetosomes can be employed as scaffolds for the display of multisubunit complexes. PMID:19837839

Ohuchi, Shoji; Schüler, Dirk

2009-12-01

351

Structural and Magnetic Properties of Thin Film of Iron Nitride  

NASA Astrophysics Data System (ADS)

The nano-crystalline iron nitride films with a mixture of ?-Fe4N, ?Fe3N and ?Fe2N phases were synthesized on copper substrate by sol-gel technology. The structure, morphology and magnetic properties of the samples were characterized using X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer. The films are ferromagnetic at room temperature. Magnetic properties such as coercive forces and saturation magnetization were found to be 398 Oestered and 32.92 emu/cm3, respectively.

Kayani, Zohra Nazir; Riaz, Saira; Naseem, Shahzad

2014-12-01

352

Spin-glass-like complex susceptibility of frozen magnetic fluids  

NASA Astrophysics Data System (ADS)

The complex magnetic susceptibility ?=?'-i?'' of different kinds of magnetic fluids (MFs) was measured as a function of temperature T from 6 to 300 K in a weak ac field of 1 Oe for frequencies ranging from f=0.1 to 1000 Hz. A prominent peak appears in both ?' and ?'' as a function of T in the frozen state of the MF in which cluster formation of the colloidal particles is difficult, whereas no peak appears in the frozen state of other MFs in which clusters form easily. The peak temperature Tp2 of ?'' depends on f following the Vogel-Fulcher (VF) law, i.e., f=f0exp[-Esg/kB(Tp2-T0)], where f0 and Esg are positive constants and T0 is a function of the particles' volume fraction ?. The VF law only holds for 0.0007<=?<=0.104, where an empirical power law of T0~?0.41 holds. There is another kind of peak in the loss factor tan?=?''/?' as a function of T, which means the existence of a magnetic aftereffect. This peak temperature Tp4 is far less than Tp2 and shown as an Arrhenius-type dependence on f with the exception of a MnZn ferrite particle MF.

Taketomi, Susamu

1998-03-01

353

Thermal to electricity conversion using thermal magnetic properties  

DOEpatents

A system for the generation of Electricity from Thermal Energy using the thermal magnetic properties of a Ferromagnetic, Electrically Conductive Material (FECM) in one or more Magnetic Fields. A FECM is exposed to one or more Magnetic Fields. Thermal Energy is applied to a portion of the FECM heating the FECM above its Curie Point. The FECM, now partially paramagnetic, moves under the force of the one or more Magnetic Fields. The movement of the FECM induces an electrical current through the FECM, generating Electricity.

West, Phillip B [Idaho Falls, ID; Svoboda, John [Idaho Falls, ID

2010-04-27

354

Slow magnetic relaxation in condensed versus dispersed dysprosium(III) mononuclear complexes.  

PubMed

Reaction of the ligands 4,5-bis(propylthio)tetrathiafulvalene-2-(2-pyridyl)benzimidazole (L(1)) and 4,5-bis(propylthio)tetrathiafulvalene-2-(2-pyridyl)-3-(2-pyridinylmethyl)benzimidazole (L(2)) with Dy(hfac)3?2?H2O (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate) gave mononuclear complexes [Dy(hfac)3(L(1))] (1) and [Dy(hfac)3(L(2))] (2). In both compounds the Dy(III) ion is surrounded by six oxygen and two nitrogen atoms. Complex 1 displays single-ion magnet (SIM) behaviour only in solution (?=12(1)?K and ?0 =1.9(4)×10(-6) ?s), while complex 2 is a SIM in both solution (?=15(2)?K and ?0 =1.5(3)×10(-6) ?s) and solid state (?=17(2)?K and ?0 =9.5(2)×10(-6) ?s). The SIM behaviour is obtained if the hydrogen bond is broken by dissolution (1 in solution) or by alkylation (2). Multiple relaxation processes were identified for 2 with two competing processes: a fast one in zero field and a slow one for fields higher than 500?Oe. The two processes coexist for intermediate applied magnetic field. Magnetic-dilution and frozen-solution measurements led to the conclusion that the origin of these multiple relaxation processes is not due to the property of a single molecule. PMID:23589325

Cosquer, Goulven; Pointillart, Fabrice; Golhen, Stéphane; Cador, Olivier; Ouahab, Lahcène

2013-06-10

355

Some Properties of Exponential Time Complexity Classes  

Microsoft Academic Search

The authors separate NE from Px (NP), where x= n0(1)-T. The class EXP-low[1] is introduced and applied in the investigations of stable properties for both EXP and NEXP hard sets. A set A is in EXP-low[1](EXP-low resp.) if EXP A[1]=EXP(EXPA=EXP). The authors separate EXP-low[1] from EXP-low by constructing a set A such that EXP A[1]=EXP and EXPA=EXPEXP

Bin Fu; Hong-zhou Li; Yong Zhong

1992-01-01

356

Imprinting properties of magnetic vortices into superconducting films.  

NASA Astrophysics Data System (ADS)

We investigated experimentally the magnetotransport properties of superconducting Al thin films on top of sub-100 nm Fe nanodot arrays. Samples with arrays of single-domain magnetic dots behave similar to plain Al films. A dramatically different behavior is observed for arrays of dots in the so-called magnetic vortex-state. For these, the details of the magnetic reversal are ``imprinted'' into the superconductor and show up in the magnetotransport properties below the superconducting TC. The resulting hybrid system shows a giant (up to 10^5 %) hysteretic magnetoresistance with different reversible/irreversible regimes related to the array's magnetic state. Such controllable effects originate from the stray fields produced by the magnetic vortex cores in the nanodots, which induce a normal/superconducting transition depending on the distribution of the vortex cores polarities.

Villegas, Javier E.; Li, C.-P.; Schuller, Ivan K.

2007-03-01

357

Electrical and magnetic properties of chitosan-magnetite nanocomposites  

NASA Astrophysics Data System (ADS)

Magnetite powders in nanometer size have been synthesized by the hydrothermal process. Various magnetic films of chitosan and the synthesized magnetite nanopowders containing different concentrations of the latter were prepared by ultrasonication route. The X-ray diffraction (XRD) studies and the transmission electron microscopy (TEM) images showed that the synthesized magnetite particles had 80 nm dimensions. The band gap of the composites was evaluated using the UV-visible Spectroscopy. The influence of magnetite content on the magnetic properties of the composite showed a decrease in the saturation magnetization with the decrease in the magnetic content. The effect of magnetite content on the dielectric properties of the polymer film at different frequencies from 0.01 to 105 Hz was studied using an electrochemical impedance spectroscopy. The possible mechanism for the observed electrical properties of the composite films was discussed.

Bhatt, Aarti S.; Krishna Bhat, D.; Santosh, M. S.

2010-04-01

358

Excellent magnetic properties of fullerene encapsulated ferromagnetic nanoclusters  

NASA Astrophysics Data System (ADS)

Ferromagnetic nanoclusters are very useful for a magnetic recording. However, application of ferromagnetic nanoclusters is limited due to air-oxidation. One way to solve air-oxidation is to encapsulate ferromagnetic nanoclusters with inert materials such as carbon when they are produced. This allows us to keep excellent magnetic properties for a long time. In this work, we report a very simple synthetic method of fullerene (i.e., onions and nanotubes) encapsulated ferromagnetic nickel and cobalt nanoclusters by thermally decomposing metallocene vapors with a resistive heater. Protection from air-oxidation was tested by annealing encapsulated ferromagnetic nanoclusters in air up to ˜180°C for half a day and then, recording XRD patterns. No oxide peaks were observed in the XRD patterns, indicating that oxidation protection via fullerene encapsulation is very good. Magnetic property measurement showed that both fullerene encapsulated nickel and cobalt nanoclusters possessed excellent magnetic properties.

Lee, G. H.; Huh, S. H.; Jeong, J. W.; Ri, H.-C.

2002-05-01

359

On the theory of rheological properties of bimodal magnetic fluids  

NASA Astrophysics Data System (ADS)

This work deals with the theoretical study of rheological properties of a suspension of micron-sized magnetizable particles in a nanodisperse ferrofluid. In recent years, these systems have been synthesized by several teams in order to enhance technological properties of traditional magnetic fluids. We suppose that the micron-sized particles, under the action of an applied magnetic field, form linear chain-like aggregates. Analysis shows that the presence of the ferrofluid can significantly increase the magnetoviscous effect in the suspension of the particles. Unlike the traditional models of magnetorheological suspensions (MRSs) with chains, we have studied the effect of mutual magnetization of particles in chains. Estimates show that this effect significantly increases macroscopical viscous stress in the suspensions and that is why it must be taken into account for theoretical descriptions and interpretation of experiments on the rheological properties of magnetic suspensions.

Chirikov, Dmitry; Iskakova, Larisa; Zubarev, Andrey; Radionov, Alexander

2014-07-01

360

Geometrical and magnetic properties of vanadium clusters supported on graphene  

NASA Astrophysics Data System (ADS)

We report ab-initio calculations of vanadium-cluster V n ( n = 2-5) adsorption on graphene sheets. Geometrical and magnetic properties of various adsorption configurations are studied using first-principles density-functional theory with the generalized gradient approximation. The geometrical and magnetic properties of vanadium clusters are found to be size-dependent, and the supported graphene sheet could influence the formation of the vanadium clusters. Low-dimensional V n cluster configurations could be easily formed when they are absorbed on a graphene sheet, and the combined V n -graphene systems exhibit a nonmagnetic state, which is the most stable magnetic configuration. Our calculations for the geometrical and the magnetic moment properties of V n -graphene systems may be of interest for some nanotechnological applications.

Zou, Yu; Zhan, Chang-Yong; Wu, Jian-Chun; Zhou, Li-Ping; Da, Hai-Xia

2013-07-01

361

Estimation Model for Magnetic Properties of Stamped Electrical Steel Sheet  

NASA Astrophysics Data System (ADS)

Less deterioration in magnetic properties of electrical steel sheets in the process of stamping out iron-core are necessary in order to maintain its performance. First, the influence of plastic strain and stress on magnetic properties was studied by test pieces, in which plastic strain was added uniformly and residual stress was not induced. Because the influence of plastic strain was expressed by equivalent plastic strain, at each equivalent plastic strain state the influence of load stress was investigated. Secondly, elastic limit was determined about 60% of macroscopic yield point (MYP), and it was found to agree with stress limit inducing irreversible deterioration in magnetic properties. Therefore simulation models, where beyond elastic limit plastic deformation begins and magnetic properties are deteriorated steeply, are proposed. Besides considered points in the deformation analysis are strain-rate sensitivity of flow stress, anisotropy under deformation, and influence of stress triaxiality on fracture. Finally, proposed models have been shown to be valid, because magnetic properties of 5mm width rectangular sheets stamped out from non-oriented electrical steel sheet (35A250 JIS grade) can be estimated with good accuracy. It is concluded that the elastic limit must be taken into account in both stamping process simulation and magnetic field calculation.

Kashiwara, Yoshiyuki; Fujimura, Hiroshi; Okamura, Kazuo; Imanishi, Kenji; Yashiki, Hiroyoshi

362

Electric and Magnetic Properties of Transition Metals and Their Compounds.  

National Technical Information Service (NTIS)

Results of studies on the electric and magnetic properties of transition metals and their compounds are presented in sections on rare earth metals, rare earth compounds, and transport properties of IrO sub 2 , RuO sub 2 , and related materials.

1976-01-01

363

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

364

Optimum condition for magnetic properties of two-phase soft magnetic alloys  

NASA Astrophysics Data System (ADS)

It is well-known that the optimum condition to obtain the highest permeability and lowest coercive force for a soft magnetic material is that both K and ?s are very small. In this paper, it is suggested that this optimum condition is sufficient only for the single phase soft magnetic material. For the material containing two phases, in order to obtain the best magnetic properties, a new condition must be added; the difference in the magnitude of the saturation magnetization of the two phases, ?MS, should be very small. Only when the K, ?s, and ?MS are all very small can the best soft magnetic properties be obtained. A model describing the hindrance of the domain well motion by the ?MS effect is suggested. Some examples in the nanocrystalline soft magnetic alloys are used to demonstrate the existence of the ?MS effect.

He, Kai-Yuan

2011-08-01

365

Magnetic properties of Fe 90Zr 7B 3 ribbons studied by FMR and magnetization  

NASA Astrophysics Data System (ADS)

The amorphous alloy Fe 90Zr 7B 3 containing alpha-iron nanocrystallites (known commercially as NANOPERM ®) is produced in ribbons by melt spinning and presents magnetic properties that allow its wide applicability in magnetic shielding, low loss RF transformers, choke coils, magnetic sensors and flux-gate magnetometers. In this work, we present a study of the effect of the annealing process realized at different temperatures on the magnetic properties of this material. Comparisons of experimental results of ferromagnetic resonance (FMR) and magnetization measurements show that the precipitation of alpha-iron phase causes the reduction of the coercive field and the in-plane magnetic anisotropy by about 70% in ribbons annealed for 1 h at temperatures between 250 and 350 °C.

Folly, W. S. D.; Caffarena, V. R.; Sommer, R. L.; Capitaneo, J. L.; Guimarães, A. P.

366

Nuclear magnetic resonance properties of lunar samples.  

NASA Technical Reports Server (NTRS)

Nuclear magnetic resonance spectra of Na-23, Al-27, and P-31 in fines samples 10084,60 and 14163,168 and in crystalline rock samples 12021,55 and 14321,166, have been recorded over a range of frequencies up to 20 MHz. A shift in the field at which maximum absorption occurs for all of the spectra relative to the field at which maximum absorption occurs for terrestrial analogues is attributed to a sample-dependent magnetic field at the Na, Al, and P sites opposing the laboratory field. The magnitude of these fields internal to the samples is sample dependent and varies from 5 to 10 G. These fields do not correlate with the iron content of the samples. However, the presence of single-domain particles of iron distributed throughout the plagioclase fraction that contains the principal fraction of Na and Al is inferred from electron magnetic resonance spectra shapes.

Kline, D.; Weeks, R. A.

1972-01-01

367

Magnetic properties on strained manganite thin film  

NASA Astrophysics Data System (ADS)

Structural and magnetic studies on La2/3Sr1/3MnO3 (LSMO) epitaxial films grown on STO (100) and MgO (100) substrates by Pulsed Laser Deposition are presented. Due to larger interface strain, the grain size of LSMO on MgO is much smaller than that on STO substrate. However, anisotropy energy produced as a result of in plane tensile strain is much larger in case of the films deposited on MgO in such a way that the blocking (irreversibility) temperature and the coercive fields inferred from temperature and magnetic field dependent magnetization measurements are significantly higher. The importance of this result for the memory applications is highlighted.

Prajapat, C. L.; Singh, M. R.; Gupta, S. K.; Bhattacharya, D.; Basu, S.; Ravikumar, G.

2014-04-01

368

Preparation and magnetic properties of bulk nanostructured PrCo5 permanent magnets with strong magnetic anisotropy  

NASA Astrophysics Data System (ADS)

Bulk anisotropic PrCo5 nanostructured magnets were prepared by hot deformation technique. The effects of height reduction on the structure and magnetic properties of the magnets were studied. It is found that the height reduction plays an important role in the formation of c-axis crystal texture of PrCo5 phase during hot deformation process. With the increase of height reduction, the c-axis crystal texture becomes more and more dominant, indicating strong magnetic anisotropy in the magnets. As a result, the saturated magnetization (Ms) of the magnets increases gradually, while the coercivity (Hci) of the magnets drops simultaneously, resulting in the remanence (Mr) of the magnets rising first, peaking at 80% height reduction, then dropping again. Under optimal height reduction of 80%, the PrCo5 magnet bears magnetic properties of Ms of 1.00 T, Mr of 0.86 T, Hci of 488.5 kA/m, and (BH)max of 96.87 kJ/m3.

Liu, W. Q.; Zuo, J. H.; Yue, M.; Lv, W. C.; Zhang, D. T.; Zhang, J. X.

2011-04-01

369

Effect of magnetic field annealing on microstructure and magnetic properties of FePt films  

Microsoft Academic Search

FePt (20nm) films were annealed in a magnetic field (along the normal direction of the films) at a temperature around the Curie temperature of L10 FePt. The influence of magnetic filed annealing on texture and magnetic properties of FePt films were investigated. The results indicate that preferential (001) orientation and perpendicular anisotropy can be obtained in L10 FePt films by

Y. B. Li; Y. F. Lou; L. R. Zhang; B. Ma; J. M. Bai; F. L Wei

2010-01-01

370

Effect of magnetic field annealing on microstructure and magnetic properties of FePt films  

Microsoft Academic Search

FePt (20 nm) films were annealed in a magnetic field (along the normal direction of the films) at a temperature around the Curie temperature of L10 FePt. The influence of magnetic filed annealing on texture and magnetic properties of FePt films were investigated. The results indicate that preferential (0 0 1) orientation and perpendicular anisotropy can be obtained in L10

Y. B. Li; Y. F. Lou; L. R. Zhang; B. Ma; J. M. Bai; F. L. Wei

2010-01-01

371

Investigation of magnetic properties for oblique deposited granular films by magnetic field annealing  

Microsoft Academic Search

A series of (Fe57Co24Ni4Nb2B13)x–(SiO2)1?x nano-granular thin films were fabricated by magnetron sputtering with different oblique incidence angle ? and excellent soft magnetic properties are achieved. Based on the results of magnetic field anneal at different temperature Ta, it is evidenced that orientation of atomic pairs contributes to the annealing treatment, and could manipulate magnetic anisotropy. The damping coefficient ? decreases

Bangmin Zhang; Shihui Ge; Huaping Zuo; Yuhua Xiao; Guowei Wang; Li Zhang

2010-01-01

372

Stress relief and magnetic properties of magnetostrictive Fe 79B 16Si 5 amorphous magnetic ribbons  

Microsoft Academic Search

The in-plane magnetic anisotropy constant and surface magnetization curves have been measured for magnetostrictive Fe79B16Si5 amorphous ribbon in the as-quenched state and after two isothermal annealing treatments. The variation of the residual stress distribution with the thermal treatments has been obtained and related to the changes in the magnetic properties. The results obtained show that the residual stresses are the

M. Tejedor; J. A Garc??a; J. Carrizo; L. Elbaile; J. D Santos

1999-01-01

373

Photoactivation properties of organometallic complexes in solution  

NASA Astrophysics Data System (ADS)

The quantitative photochemistry of (eta5-C5H 5)Fe(CO)2I, [(eta5-C5H5 )Fe(eta6-ipb)]PF6 (ipb = isopropylbenzene) and (eta5-C5H4(CH3))Pt(CH 3)3 in room-temperature solution has been investigated following irradiation at several wavelengths in the 313--683 nm region. In the case of (eta5-C5H5)Fe(CO)2I, the most effective heterolytic cleavage of iodide to form (eta5-C 5H5)Fe(CO)2(eta1-N-pyrrolyl) was found to take place with excitation at long wavelengths (580--647 nm). The absolute photochemical quantum efficiency (?cr) for this photoreaction has been determined to be 0.38 upon photolysis at 647 nm. The photochemical results demonstrate that long-wavelength irradiation provides a valuable way of effecting heterolytic Fe-I dissociation, facilitating a synthetic pathway to azaferrocene. In the [(eta5-C5 H5)Fe(eta6-ipb)]PF6 case, the complex was excited into the lowest-lying singlet ligand field (LF) manifold (355, 458, 488, 514 nm) and directly into the corresponding lowest-lying triplet LF state (633, 683 rim) in nine different solvents. The ?cr results for arene dissociation reaction reveal that the system exhibits a strong wavelength dependence in each investigated solvent and that the reaction is extremely efficient in the UV and visible regions. The wavelength dependence also reveals that the photochemistry does not occur solely from the lowest-lying LF triplet excited state. The solvent dependence shows that there are two different reactive pathways at any excitation wavelength; several factors influence these pathways, including ion-pairing, the nature of the counter-ion and the nucleophilicity of the solvent. New insights in terms of both photophysical and mechanistic aspects of this system are obtained from the quantitative photochemical results. In the case of (eta5-C5H 4(CH3))Pt(CH3)3, highly effective photochemical disappearance of the parent complex was determined in n-pentane (?cr = 0.41) and even higher in the presence of triethylsilane (?cr = 0.79--0.85) following excitation at 313--366 nm respectively. Photohydrosilylation results illustrate that the photopolymerization reaction is also extremely effective.

Jakubek, Vladimir

2000-10-01

374

Microstructure and magnetic properties of inert gas atomized rare earth permanent magnetic materials  

Microsoft Academic Search

Several permanent magnet alloys based on the ternary NdâFeââB (2-14-1) composition have been prepared by inert gas atomization (IGA). The microstructure and magnetic properties of these alloys have been studied as a function of particle size, both before and after heat treatment. Different particle sizes have characteristic properties due to the differences in cooling rate experienced during solidification from the

C. H. Sellers; T. A. Hyde; D. J. Branagan; L. H. Lewis; V. Panchanathan

1997-01-01

375

Microstructure and magnetic properties of inert gas atomized rare earth permanent magnetic materials  

Microsoft Academic Search

Several permanent magnet alloys based on the ternary Nd2Fe14B (2-14-1) composition have been prepared by inert gas atomization (IGA). The microstructure and magnetic properties of these alloys have been studied as a function of particle size, both before and after heat treatment. Different particle sizes have characteristic properties due to the differences in cooling rate experienced during solidification from the

C. H. Sellers; T. A. Hyde; D. J. Branagan; L. H. Lewis; V. Panchanathan

1997-01-01

376

Microwave Properties of Partially Magnetized Ferrites.  

National Technical Information Service (NTIS)

A considerable number of microwave devices now use ferrites in the partially magnetized state. In order to assist the design engineer in predicting the performance of such devices, this report presents data on the microwave permeability of a wide range of...

J. J. Green F. Sandy

1969-01-01

377

Synthesis and magnetic properties of polymer nanocomposites  

Microsoft Academic Search

Magnetic nanoparticles embedded in polymer matrices have excellent potential for electromagnetic device applications like electromagnetic interference (EMI) suppression. Using chemical precipitation methods and Nanogen , a microwave plasma method, we have synthesized various nanoparticles including iron, polystyrene-coated iron, iron oxide (both hematite and magnetite), nickel ferrite, and manganese zinc ferrite. We have synthesized polymer nanocomposites of polymethylmethacrylate (PMMA), polystyrene (PS),

Jessica L Wilson

2004-01-01

378

Magnetic properties of biosynthesized magnetite nanoparticles  

Microsoft Academic Search

Magnetic nanoparticles, which are unique because of both structural and functional elements, have various novel applications. The popularity and practicality of nanoparticle materials create a need for a synthesis method that produces quality particles in sizable quantities. This paper describes such a method, one that uses bacterial synthesis to create nanoparticles of magnetite. The thermophilic bacterial strain Thermoanaerobacter ethanolicus TOR-39

Lucas W. Yeary; Ji-Won Moon; L. J. Love; J. R. Thompson; C. J. Rawn; T. J. Phelps

2005-01-01

379

Microwave Properties of Partially Magnetized Ferrites  

Microsoft Academic Search

With the surge of design activity of ferrite components for phased array RADARs, a knowledge of the microwave characteristics of partially magnetized ferrites is a very useful asset. Phase shifters, circulators, and switches are most economically designed if the biasing field can be kept small. A preferred configuration consists of the microwave ferrite being latched into a major or minor

J. J. Green; F. Sandy; C. E. Patton

1971-01-01

380

The magnetic properties of sigma phase alloys  

Microsoft Academic Search

Measurements of intrinsic magnetization as a function of temperature and composition have been made on a number of first series sigma phase alloys. In conflict with earlier work, ferromagnetism has been observed in only two systems, Fe Cr and Fe V. The results on Fe Cr exhibit many interesting features, and appear to be consistent with a ferrimagnetic model for

D. Read; E. Thomas

1966-01-01

381

Undulator a magnetic properties and spectral performance..  

National Technical Information Service (NTIS)

The Undulator A at the Advanced Photon Source (APS) is a planar permanent magnet hybrid device optimized for generating x-rays from 3 keV to 45 keV by using the first, third, and fifth radiation harmonics. It also produces x-rays above this energy. For hi...

R. J. Dejus I. B. Vasserman S. Sasaki E. R. Moog

2002-01-01

382

Magnetic Fabric, Paleomagnetism and Rock Magnetism of Mafic Intrusive Rocks in the Shimanto Accretionary Complex in Southwest Japan  

NASA Astrophysics Data System (ADS)

The Shimanto Belt in Southwest Japan is unique in that a part of this accretionary complex was characterized by anomalous, post-accretion, near-trench igneous activity associated with regional folding and faulting. Our study focuses on a large intrusive body (c. 14 Ma) and nearby mafic rocks as well as surrounding sedimentary rocks near Cape Muroto of Shikoku Island. We measured remanent magnetizations, anisotropy of magnetic susceptibilities (AMS) and rock magnetic properties in order to clarify how the mafic body was intruded and settled in the present attitude, and to assess the thermal effect of volcanic intrusion on the accretionary prism. The intrusive body was sampled several meters interval from the chilled margin over about 120 m thick in total, and showed stable remanent magnetizations with moderate magnetic coercivity and unblocking temperature spectrum indicating fine-grained magnetite in the groundmass is the major magnetic carrier. The in-situ directions point moderately upward in the northwest quadrant, showing remarkable contrast from the representative direction of contemporaneous rocks in Southwest Japan. There is a systematic variation in inclinations with distance from the margin: the in-situ inclinations of 30-50 degrees near the margin appears to steepen gradually up to 70-80 degrees toward the core of the body. AMS study recognized two zones with relatively well-grouped, minimum susceptibility axes; the one zone, which has the most tightly clustered minimum axes, is located about 20-30 m away from the chilled margin, and the other one is in the central portion of the body with minimum axes much more scattered. The oblate magnetic fabric is consistent with the bedding attitude of the surrounding sedimentary strata, indicating that the body intruded nearly horizontally into the sediment. Magnetizations of the sedimentary rocks nearby show similar directions of reversed polarity as the volcanic intrusion, suggesting the sediments are likely to have been remagnetized on intrusion of the mafic rocks. These AMS and paleomagnetic results suggest that the intrusive body experienced considerable deformation as well as the host accretionary prism.

Kodama, K.

2003-12-01

383

PREDICTION OF THERMODYNAMIC PROPERTIES OF COMPLEX FLUIDS  

SciTech Connect

ABSTRACT The goal of this research has been to generalize Density Functional Theory (DFT) for complex molecules, i.e. molecules whose size, shape, and interaction energies cause them to show significant deviations from mean-field behavior. We considered free energy functionals and minimized them for systems with different geometries and dimensionalities including confined fluids (such as molecular layers on surfaces and molecules in nano-scale pores), systems with directional interactions and order-disorder transitions, amphiphilic dimers, block copolymers, and self-assembled nano-structures. The results of this procedure include equations of equilibrium for these systems and the development of computational tools for predicting phase transitions and self-assembly in complex fluids. DFT was developed for confined fluids. A new phenomenon, surface compression of confined fluids, was predicted theoretically and confirmed by existing experimental data and by simulations. The strong attraction to a surface causes adsorbate molecules to attain much higher densities than that of a normal liquid. Under these conditions, adsorbate molecules are so compressed that they repel each other. This phenomenon is discussed in terms of experimental data, results of Monte Carlo simulations, and theoretical models. Lattice version of DFT was developed for modeling phase transitions in adsorbed phase including wetting, capillary condensation, and ordering. Phase behavior of amphiphilic dimers on surfaces and in solutions was modeled using lattice DFT and Monte Carlo simulations. This study resulted in predictive models for adsorption isotherms and for local density distributions in solutions. We have observed a wide variety of phase behavior for amphiphilic dimers, including formation of lamellae and micelles. Block copolymers were modeled in terms of configurational probabilities and in the approximation of random mixing entropy. Probabilities of different orientations for the segments were considered as order parameters and the free energy was written as a functional of these parameters. Imposing boundary conditions allowed us to apply this approach to confined fluids. Equilibrium self-assembly in fluids was studied in the framework of the lattice density functional theory (DFT). In particular, DFT was used to model the phase behavior of anisotropic monomers. Though anisotropic monomers are a highly idealized model system, the analysis presented here demonstrates a formalism that can be used to describe a wide variety of phase transitions, including processes referred to as self-assembly. In DFT, the free energy is represented as a functional of order parameters. Minimization of this functional allows modeling spontaneous nano-scale phase transitions and self-assembly of supramolecular structures. In particular, this theory predicts micellization, lamellization, fluid – glass phase transitions, crystallization, and more. A classification of phase transitions based on general differences in self-assembled structures is proposed. The roles of dimensionality and intermolecular interactions in different types of phase transitions are analyzed. The concept of “genetic” codes is discussed in terms of structural variety of self-assembled systems.

Marc Donohue

2006-01-05

384

Structure and magnetic properties of nanocrystalline PrCo3  

NASA Astrophysics Data System (ADS)

The structure and magnetic properties of nanocrystalline PrCo3 prepared by high-energy milling technique have been investigated by means of x-ray diffraction using the Rietveld method coupled to Curie temperature and magnetic measurements. The as-milled samples were subsequently annealed in temperature range from 750 to 1050 °C for 30 min to optimize the extrinsic properties. From x-ray studies of magnetic aligned samples, the magnetic anisotropy of this compounds is found uniaxial. The Curie temperature is 349 K and no saturation reached at room temperature for applied field of 90 kOe. The coercive field of 55 kOe and 12 kOe measured at 10 K and 293 K, respectively is obtained after annealing at 750 °C for 30 min suggests that nanocrystalline PrCo3 are interesting candidates in the field of permanent magnets. We have completed this experimental study by simulations in the micromagnetic framework in order to get a qualitative picture of the microstructure effect on the macroscopic magnetization curve. From this simple model calculation, we can suggest that the after annealing the system behaves as magnetically hard crystallites embedded in a weakly magnetized amorphous matrix.

Younsi, K.; Russier, V.; Bessais, L.

2010-04-01

385

Cyanomethylene-bis(phosphonate)-based lanthanide complexes: structural, photophysical, and magnetic investigations.  

PubMed

The syntheses, structural investigations, magnetic and photophysical properties of a series of 10 lanthanide mononuclear complexes, containing the heteroditopic ligand cyanomethylene-bis(5,5-dimethyl-2-oxo-1,3,2?(5)-dioxa-phosphorinane) (L), are described. The crystallographic analyses indicate two structural types: in the first one, [Ln(III)(L)3(H2O)2]·H2O (Ln = La, Pr, Nd), the metal ions are eight-coordinated within a square antiprism geometry, while the second one, [Ln(III)(L)3(H2O)]·8H2O (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er), contains seven-coordinated Ln(III) ions within distorted monocapped trigonal prisms. Intermolecular hydrogen bonding between nitrogen atoms of the cyano groups, crystallization, and coordination water molecules leads to the formation of extended supramolecular networks. Solid-state photophysical investigations demonstrate that Eu(III) and Tb(III) complexes possess intense luminescence with relatively long excited-state lifetimes of 530 and 1370 ?s, respectively, while Pr(III), Dy(III), and Ho(III) complexes have weak intensity luminescence characterized by short lifetimes ranging between a few nanoseconds to microseconds. The magnetic properties for Pr(III), Gd(III), Tb(III), Dy(III), and Ho(III) complexes are in agreement with isolated Ln(III) ions in the solid state, as suggested by the single-crystal X-ray analyses. Alternating current (ac) susceptibility measurements up to 10 kHz reveal that only the Ho(III) complex shows a frequency-dependent ac response, with a relaxation mode clearly observed at 1.85 K around 4500 Hz. PMID:24555824

Maxim, Catalin; Branzea, Diana G; Tiseanu, Carmen; Rouzières, Mathieu; Clérac, Rodolphe; Andruh, Marius; Avarvari, Narcis

2014-03-01

386

Fabrication of a fully magnetic impeller for improvement of the magnetic properties of a pump with a power harvester  

NASA Astrophysics Data System (ADS)

An all-in-one wireless pump with a power generator was developed for use in biomedical applications. The developed pump is driven by an external rotating magnetic field. Thus, the performance of the system is limited by the magnetic properties of the rotor. To improve the magnetic properties of the magnetic all-in-one pump, a fully magnetic impeller was fabricated with magnetic powder (Sm2Fe17N3) because sintered magnetic materials have a lower degree of freedom for shape. The magnetic moment (M) and coercive force (Hc) of the fully magnetic impeller are 0.993 Am2 and 0.82 MA/m, respectively. We analyzed the magnetic properties of the fully magnetic impeller using simulation and experiments. In addition, we investigated the improved performance of the all-in-one pump system using the fully magnetic impeller.

Kim, Sung Hoon; Shin, Jaewon; Hashi, Shuichiro; Ishiyama, Kazushi; Ozaki, Masaru; Matsumura, Syuji

2012-04-01

387

Complex magnetic order in Pr?Pd?Ge?: a single crystal study.  

PubMed

We have investigated the magnetic and electronic transport properties of single crystal Pr(2)Pd(3)Ge(5) grown by the Czochralski method. Complex magnetic behaviour (multiple magnetic transitions) is clearly seen in this compound from the magnetic susceptibility ?(T), isothermal magnetization M(H) and electrical resistivity ?(T) data. For the magnetic field applied along the crystallographic c-axis (H ? [001]) the ?(T) data exhibit two sharp transitions at 6.9 and 6.3 K and a broad hump near 8 K. Four anomalies at 8.0, 7.3, 6.2 and 4.9 K are observed for the magnetic field along both a- and b-directions (H ? [100] and H ? [010]). Further, the ordered state ?(T) presents a large anisotropy with an easy axis along the c-axis. The presence of magnetocrystalline anisotropy is also inferred from the isothermal M(H) data. The M(H) data measured at 1.9 K for H ? [001] exhibit a step-like increase due to field-induced metamagnetic transitions at [Formula: see text] T and [Formula: see text] T. For H ? [100] and H ? [010] sharp step-like field-induced metamagnetic transitions occur at [Formula: see text] T and [Formula: see text] T which are accompanied by a weak S-shaped spin-flop metamagnetic transition at [Formula: see text] T. We have extracted the H-T phase diagram from the M(H) data collected at different temperatures in the magnetically ordered state which shows the existence of three magnetic phases below T(N) for H ? [100] and H ? [010], and two magnetic phases for H ? [001]. A sharp transition due to the onset of long range antiferromagnetic order is also seen in the ?(T) data which also exhibit anisotropic behaviour. The observation of an upturn near T(N) in the ?(T) data suggests the formation of a super-zone gap and hence the existence of incommensurate magnetic structure. Further, in the ordered state, the ?(T) data present a gap in the excitation spectrum of magnons with a characteristic energy gap ? ? 0.23 meV. PMID:23086193

Anand, V K; Thamizhavel, A; Ramakrishnan, S; Hossain, Z

2012-11-14

388

Tailoring the magnetic and pharmacokinetic properties of iron oxide magnetic particle imaging tracers  

PubMed Central

Magnetic particle imaging (MPI) is an attractive new modality for imaging distributions of iron oxide nanoparticle tracers in vivo. With exceptional contrast, high sensitivity, and good spatial resolution, MPI shows promise for clinical imaging in angiography and oncology. Critically, MPI requires high-quality iron oxide nanoparticle tracers with tailored magnetic and surface properties to achieve its full potential. In this review, we discuss optimizing iron oxide nanoparticles’ physical, magnetic, and pharmacokinetic properties for MPI, highlighting results from our recent work in which we demonstrated tailored, biocompatible iron oxide nanoparticle tracers that provided two times better linear spatial resolution and five times better signal-to-noise ratio than Resovist.

Ferguson, Richard Mathew; Khandhar, Amit P; Arami, Hamed; Hua, Loc; Hovorka, Ondrej; Krishnan, Kannan M.

2014-01-01

389

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

390

Magnetic Properties of Dipolar Chains in Ferrofluids  

NASA Astrophysics Data System (ADS)

We have investigated the dipole interaction energies per particle and the local dipole field distributions in a frozen-magnetization model of a ferrofluid chain in a saturating magnetic field. A lognormal distribution of particle diameters was assumed. The interaction energies were calculated for one-dimensional arrays of dipoles with moments parallel to the chain. We have computed the energies by various approximations related to the hard sphere particle diameter distribution. A similar approach was followed for the local field distributions. It was found that the energy per particle and mean local field were largely determined by the mean particle diameter, but the distribution of local fields was sensitive to both the mean diameter and the assumptions about spatial correlations between particles of different size. Detailed results are presented for water-soluble Fe3O4/PAA (polyacrylic acid).

Avgin, I.; Huber, D. L.

2014-05-01

391

Memristive properties of single-molecule magnets  

NASA Astrophysics Data System (ADS)

Single-molecule magnets weakly coupled to two ferromagnetic leads act as memory devices in electronic circuits—their response depends on history, not just on the instantaneous applied voltage. We show that magnetic anisotropy introduces a wide separation of time scales between fast and slow relaxation processes in the system, which leads to a pronounced memory dependence in a wide intermediate time regime. We study the response to a harmonically varying bias voltage from slow to rapid driving within a master-equation approach. The system is not purely memristive but shows a partially capacitive response on short time scales. In the intermediate time regime, the molecular spin can be used as the state variable in a two-terminal molecular memory device.

Timm, Carsten; Di Ventra, Massimiliano

2012-09-01

392

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

393

The symmetry properties of planetary magnetic fields  

NASA Technical Reports Server (NTRS)

This paper provides a comparative study of the geometrical structures of the magnetic fields of earth, Jupiter, Saturn, and Uranus, starting from the traditional multipolar representations of these fields. For earth, Jupiter, and Saturn, the centered dipole, quadrupole, and octupole contributions are included, while at Uranus only the dipole and quadrupole contributions are considered. It is found that there are a number of common features of the magnetic fields of earth and Jupiter. Compared to earth and Jupiter, the Saturnian field exhibits not only a high degree of symmetry about the rotation axis but also a high degree of antisymmetry about the equatorial plane. The Uranian field shows strong deviations from both such symmetries. Nevertheless, there remain features common to all four planets.

Raedler, Karl-Heinz; Ness, Norman F.

1990-01-01

394

Magnetic Properties of Dipolar Chains in Ferrofluids  

NASA Astrophysics Data System (ADS)

We have investigated the dipole interaction energies per particle and the local dipole field distributions in a frozen-magnetization model of a ferrofluid chain in a saturating magnetic field. A lognormal distribution of particle diameters was assumed. The interaction energies were calculated for one-dimensional arrays of dipoles with moments parallel to the chain. We have computed the energies by various approximations related to the hard sphere particle diameter distribution. A similar approach was followed for the local field distributions. It was found that the energy per particle and mean local field were largely determined by the mean particle diameter, but the distribution of local fields was sensitive to both the mean diameter and the assumptions about spatial correlations between particles of different size. Detailed results are presented for water-soluble Fe3O4/PAA (polyacrylic acid).

Avgin, I.; Huber, D. L.

2014-06-01

395

Laser-induced magnetic nanostructures with tunable topological properties.  

PubMed

We report the creation and real-space observation of magnetic structures with well-defined topological properties and a lateral size as low as about 150 nm. They are generated in a thin ferrimagnetic film by ultrashort single optical laser pulses. Thanks to their topological properties, such structures can be classified as Skyrmions of a particular type that does not require an externally applied magnetic field for stabilization. Besides Skyrmions, we are able to generate magnetic features with topological characteristics that can be tuned by changing the laser fluence. The stability of such features is accounted for by an analytical model based on the interplay between the exchange and the magnetic dipole-dipole interactions. PMID:23679767

Finazzi, M; Savoini, M; Khorsand, A R; Tsukamoto, A; Itoh, A; Duò, L; Kirilyuk, A; Rasing, Th; Ezawa, M

2013-04-26

396

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

397

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

398

Electrically conductive polyaniline—A molecular magnet with the possibility of chemically controlling the magnetic properties  

NASA Astrophysics Data System (ADS)

Different forms of an electrically conductive polymer, an organic semiconductor, namely, polyaniline, have been synthesized and characterized. The magnetization curves of the obtained forms have been analyzed. It has been found that, in the oxidized form, the material exhibits a magnetic hysteresis at room temperature. For polyaniline without a special doping with magnetic additives, this result has been obtained for the first time. The possibility of controlling the magnetic properties of the material by means of chemical treatment at the post-polymerization stage has been demonstrated.

Kompan, M. E.; Sapurina, I. Yu.; Babayan, V.; Kazantseva, N. E.

2012-12-01

399

Stress relief and magnetic properties of magnetostrictive Fe 79B 16Si 5 amorphous magnetic ribbons  

NASA Astrophysics Data System (ADS)

The in-plane magnetic anisotropy constant and surface magnetization curves have been measured for magnetostrictive Fe 79B 16Si 5 amorphous ribbon in the as-quenched state and after two isothermal annealing treatments. The variation of the residual stress distribution with the thermal treatments has been obtained and related to the changes in the magnetic properties. The results obtained show that the residual stresses are the main source of the in-plane magnetic anisotropy, they act as pinning centers for the wall displacements, and they are mainly near the surface.

Tejedor, M.; Garc?´a, J. A.; Carrizo, J.; Elbaile, L.; Santos, J. D.

1999-08-01

400

Neutron structure analysis and magnetic properties of ?  

NASA Astrophysics Data System (ADS)

The crystallographic and magnetic structures of 0953-8984/9/41/003/img13 compounds at room temperature were refined by Rietveld analysis of the neutron powder diffraction data. The analysis indicates that 0953-8984/9/41/003/img14 (x = 5,8) compounds have 0953-8984/9/41/003/img15 type structure 0953-8984/9/41/003/img16. For x = 5 Ga atoms partially occupy 18h and 18f sites with the occupancies of 0.40 and 0.43, and for x = 8 they occupy 18h, 18f and 6c sites with the occupancies of 0.20, 0.80 and 1.0 respectively. The magneto-anisotropy changes from easy planar to easy-axial when the Ga content x increases from 5 to 8. The magnetic measurements show that the magnetic ordering temperature 0953-8984/9/41/003/img17 increases abnormally with Ga content x increasing from 6.5 to 8. This paper gives a reasonable explanation for this phenomenon.

Zhang, P. L.; Sun, X. D.; Wang, F. W.; Shen, B. G.; Yan, Q. W.; Ridwan, S.; Mujamilah, H.; Gunawan, M.; Marsongkohadi, P.

1997-10-01

401

Morphology and properties of magnetic fractals  

NASA Astrophysics Data System (ADS)

The inert-gas condensation (IGC) process offers a large variety in the synthesis of nano-particulate metals. In the present work the agglomeration of nickel nanoparticles is studied after evaporation/condensation of ingot material in a laminar Argon gas flow in the pressure range of 50-300 mbar. It is observed that the nickel nanoparticles tend to form large and loosely bound aggregates due to diffusional effects and attractive interparticle forces. A transition from an irregular type to a chain-like morphology is observed, which depends on particle size and can be formally described by a reduction in the fractal dimension. Such necklace-like chains could be deposited in a well-aligned manner in the presence of external magnetic fields. Numerical modeling of magnetically induced aggregation suggests that the interaction energy between the magnetic dipoles leads to chain-formation, if it overcomes the thermal energy of the individ-ual particles. In order to achieve well-defined conditions during extended agglomeration time, buoyancy effects must be suppressed, which usually exist due to strong thermal gradients inside the flow tube chamber. Therefore experiments on parabolic flights were performed to sample agglomerates that were unaffected by convection for up to 10s.

Günther, Bernd

402

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

403

Improvements of magnetic properties of Sr ferrite magnets by substitutions of La and Co  

SciTech Connect

Recently, it is intensively required to improve the magnetic properties of Sr ferrite magnets in order to decrease the weight of motors used in automobiles and to improve the efficiency of motors used in electric appliances such as air conditioners. The effect of the simultaneous partial substitution of Co{sup 2+} for Fe{sup 3+} and of La{sup 3+} for Sr{sup 2+} ion in Sr ferrite on the magnetic properties of anisotropic Sr ferrite magnets was investigated. It was found that the coercive force of Sr ferrite magnets is increased without significant decrease in residual flux density by La-Co substitution. Temperature coefficients of coercive force were found to be also improved by La-Co substitution.

Ogata, Yasunobu; Kubota, Yutaka; Takami, Takashi; Tokunaga, Masaaki; Shinohara, Tadashi

1999-09-01

404

Magnetic properties of ferrite microparticles in borate glasses  

NASA Astrophysics Data System (ADS)

Magneto-optic Faraday effect in potassium-alumina-borate glasses with Fe 2O 3 and CoO additions made during synthesis was studied in dependence on the light wavelength, external magnetic field an temperature. It was shown that unusual magnetic properties of these glasses were due to the formation of ferrimagnetic particles which behaved at definite conditions as an ansamble of noninterecting superparamagnetic particles. Dimensions, structure, composition and blocking temperature of the particles have been determined.

Edelman, I. S.; Zarubina, T. V.; Stepanov, S. A.; Kim, T. A.

1992-04-01

405

Magnetic properties of iron nanoparticles in mesoporous silica  

Microsoft Academic Search

Magnetic properties of nanocomposites based on mesoporous silica SiO2 with embedded iron particles are