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1

Salen-based [Zn2Ln3] complexes with fluorescence and single-molecule-magnet properties.  

PubMed

A family of four isostructural complexes with a V-shaped pentanuclear [Zn(2)Ln(3)] core of general formula [Zn(2)Ln(3)(m-salen)(3)(N(3))(5)(OH)(2)] [Ln(III) = Tb(III) (1), Eu(III) (2), Ho(III) (3), Dy(III) (4); m-salen = N,N'-ethylenebis(3-methoxysalicylideneamine)] were isolated and structurally characterized. The fluorescence and magnetic measurements of the four compounds were investigated. Complex 1 exhibits strong fluorescence properties, while single-molecule-magnet behavior is seen in complex 4. PMID:19678667

Burrow, Carolyn E; Burchell, Tara J; Lin, Po-Heng; Habib, Fatemah; Wernsdorfer, Wolfgang; Clérac, Rodolphe; Murugesu, Muralee

2009-09-01

2

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

3

Syntheses, crystal structures, magnetic and luminescence properties of five novel lanthanide complexes of nitronyl nitroxide radical  

SciTech Connect

Five novel Ln(III) complexes based on a new nitronyl nitroxide radical have been synthesized, characterized structurally and magnetically: [Ln(hfac){sub 3}(NITPh-3-Br-4-OMe){sub 2}] (Ln(III)=Eu(1), Gd(2), Tb(3), Dy(4), Ho(5); hfac=hexafluoroacetylacetonate; and NITPh-3-Br-4-OMe=2-3?-Br-4?-methoxyphenyl-4,4,5,5 -tetramethylimidazoline-1-oxyl-3-oxide). The single-crystal structures analyses show that these complexes have similar mononuclear tri-spin structures, in which central Ln(III) ions are all eight coordinated by three hfac molecules and two NITPh-3-Br-4-OMe radicals. The variable-temperature magnetic susceptibility studies reveal the antiferromagnetic interactions between the paramagnetic ions (Ln(III) and radicals) in complexes 1, 2, 3 and 5 and ferromagnetic interaction in complex 4. The luminescence characterizations of complexes Eu(1), Tb(3) and Dy(4) are also studied in this paper. - Graphical abstract: Using a novel halogen phenyl-substituted nitronyl-nitroxide radical, we obtained and characterized five isostructural lanthanide mononuclear tri-spin compounds. - Highlights: • A new halogen phenyl-substituted nitronyl-nitroxide radical was designed. • Five new Ln(III) radical complexes have been synthesized and characterized. • The reasonable evaluation the magnetic interactions between Ln(III) ions and radical is meaningful. • These complexes show good luminescent properties.

Wang, Ya-Li; Gao, Yuan-Yuan [Department of Chemistry and Key Laboratory of Advanced Energy Materials Chemistry (MOE) and TKL of Metal and Molecule Based Material Chemistry, Nankai University, Tianjin 300071 (China); Ma, Yue, E-mail: maynk@nankai.edu.cn [Department of Chemistry and Key Laboratory of Advanced Energy Materials Chemistry (MOE) and TKL of Metal and Molecule Based Material Chemistry, Nankai University, Tianjin 300071 (China); Wang, Qing-Lun; Li, Li-Cun [Department of Chemistry and Key Laboratory of Advanced Energy Materials Chemistry (MOE) and TKL of Metal and Molecule Based Material Chemistry, Nankai University, Tianjin 300071 (China); Liao, Dai-Zheng [Department of Chemistry and Key Laboratory of Advanced Energy Materials Chemistry (MOE) and TKL of Metal and Molecule Based Material Chemistry, Nankai University, Tianjin 300071 (China); State Key Laboratory of Physical Chemistry of Solid Surface, Xiamen University, Xiamen 361005 (China)

2013-06-15

4

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

PubMed

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

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

2014-06-01

5

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.

Roberta Schneck

2011-10-13

6

New tris-3,4-HOPO lanthanide complexes as potential imaging probes: complex stability and magnetic properties.  

PubMed

There is a growing interest in the development of new medical diagnostic tools with higher sensibility and less damage for the patient body, namely on imaging reporters for the management of diseases and optimization of treatment strategies. This article examines the properties of a new class of lanthanide complexes with a tripodal tris-3-hydroxy-4-pyridinone (tris-3,4-HOPO) ligand - NTP(PrHP)(3). Among the studies herein performed, major relevance is given to the thermodynamic stability of the complexes with a series of Ln(3+) ions (Ln = La, Pr, Gd, Er, Lu) and to the magnetic relaxation properties of the Gd(3+) complex. This hexadentate ligand enables the formation of (1 : 1) Ln(3+) complexes with high thermodynamic stability following the usual trend, while the Gd-chelates show improved relaxivity (higher hydration number), as compared with the commercially available Gd-based contrast agents (CAs); transmetallation of the Gd(3+)-L complex with Zn(2+) proved to be thermodynamically and kinetically disfavored. Therefore, NTP(PrHP)(3) emerges as part of a recently proposed new generation of CAs with prospective imaging sensibility gains. PMID:23296398

Mendonça, Ana C; Martins, André F; Melchior, Andrea; Marques, Sérgio M; Chaves, Sílvia; Villette, Sandrine; Petoud, Stéphane; Zanonato, Pier Luigi; Tolazzi, Marilena; Bonnet, Célia S; Tóth, Éva; Di Bernardo, Plinio; Geraldes, Carlos F G C; Santos, M Amélia

2013-05-01

7

Electrical, magnetic, and thermal properties of the ?-FeZn10 complex intermetallic phase  

NASA Astrophysics Data System (ADS)

We report the electrical, magnetic, and thermal properties of the ?-FeZn10 phase in the zinc-rich domain of the Fe-Zn system. The ?-FeZn10 phase possesses high structural complexity typical of complex metallic alloys: a giant unit cell comprising 556 atoms, polyhedral atomic order with icosahedrally coordinated environments, fractionally occupied lattice sites, and statistically disordered atomic clusters that introduce intrinsic disorder into the structure. Structural disorder results in suppression of the electrical and heat transport phenomena, making ?-FeZn10 a poor electrical and thermal conductor. Structural complexity results in a complex electronic structure that is reflected in the opposite signs of the thermoelectric power and the Hall coefficient. The ?-FeZn10 phase is paramagnetic down to the lowest investigated temperature of 2 K with a significant interspin coupling of antiferromagnetic type. Specific heat indicates the formation of short-range-ordered spin clusters at low temperatures, very likely a precursor of a phase transition to a collective magnetic state that would take place below 2 K. The magnetoresistance of ?-FeZn10 is sizeable, amounting to 1.5% at 2 K in a 9-T field. The electrical resistivity exhibits a maximum at about 220 K, and its temperature dependence could be explained by the theory of slow charge carriers, applicable to metallic systems with weak dispersion of the electronic bands, where the electron motion changes from ballistic to diffusive upon heating.

Jazbec, S.; Koželj, P.; Vrtnik, S.; Jagli?i?, Z.; Pop?evi?, P.; Ivkov, J.; Stani?, D.; Smontara, A.; Feuerbacher, M.; Dolinšek, J.

2012-08-01

8

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.

9

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

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

10

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

11

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

12

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

PubMed

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

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

2013-11-21

13

Magnetic Properties of the Pd and Pt Group Transition Metal Complexes  

Microsoft Academic Search

The magnetic susceptibilities and the g-values of the Pd and Pt group transition metal complexes are calculated by means of the intermediate coupling scheme. Crystalline field with cubic symmetry is assumed to be strong, so that the effect of dgamma orbitals is neglected. The effect of Coulomb repulsion is considered to be comparable with that of the spin-orbit interaction. The

Hiroshi Kamimura; Shoichiro Koide; Hisao Sekiyama; Satoru Sugano

1960-01-01

14

Complex phase, microstructure and magnetic properties of Z-type hexaferrite sintered at low-temperature  

Microsoft Academic Search

In this paper, the effects of different additives, calcining temperatures and mixing process on Z-phase transformation mechanism during sintering, microstructure and magnetic properties were investigated. The Z-type hexaferrite, Ba3Co0.8Zn1.2Fe24O41 ((Co0.4Zn0.6)2Z), was prepared by solid-state reaction method.

L. Jia; H. Zhang; Y. Liu; Z. Zhong

2006-01-01

15

Solvent dependent reactivities of di-, tetra- and hexanuclear manganese complexes: syntheses, structures and magnetic properties.  

PubMed

An unusual solvent effect on the synthesis of five manganese complexes [Mn2(L1)2(Py)4](), [Mn2(L1)2(DMSO)4](), [Mn4(L2)4(OH)4](), [Mn4(L3)2(DMSO)7(H2O)](), and [Mn6O2(L4)4(OAc)2(OMe)2(DMSO)4]·MeOH] (), (H3L1 = 5-(2-oxyphenyl)-pyrazole-3-carboxylic acid; H2L2 = 5-(2-oxyphenyl)-pyrazole-3-carboxylic acid amide; H4L3 = di-[5-(2-oxyphenyl)-pyrazole]-3-hydroxamic ether; and H2L4 = 5-(2-oxyphenyl)-pyrazole-3-carboxylic acid methyl ester) has been reported. Five complexes have been characterized by X-ray single crystal diffraction, IR, element analysis, thermogravimetric analysis and UV-vis spectra. The analysis reveals that complexes and are isostructural with a bimetallic six-membered ring and L1 from the decomposition of the original H4ppha (H4ppha = 5-(2-hydroxyphenyl)-pyrazole-3-hydroxamic acid) ligand. Complexes and are two tetranuclear clusters, and possesses an aza12-metallacrown-4 core with L2 from the amide functionalization of the decomposition L1; while represents a novel linear [Mn4N8O2] core with L3 from the condensation of L1 and H4ppha. Complex is the first Mn6 cluster linked by two stacked, off-set 8-azametallacrown-3 subunits with [M-N-N-M-N-N-M-O] connectivity, and L4 derived from the esterification of L1. The magnetic behaviour of complexes show the dominant antiferromagnetic interactions between metal centers, whereas complex further reveals the coexistence of antiferromagnetic and ferromagnetic interactions, and slow magnetic relaxation at T < 6 K with S = 4 ground state, as well as field induced magnetization saturation. PMID:25758136

Yang, Hua; Cao, Fan; Li, Dacheng; Zeng, Suyuan; Song, You; Dou, Jianmin

2015-03-24

16

Synthesis, structure and magnetic properties of four unexpected di- and tetranuclear Robson-type macrocyclic complexes  

NASA Astrophysics Data System (ADS)

Four symmetrical macrocyclic complexes, [Ni2L1(C6H4NO2)] (H2O)4 (1), [Cu4L1N3(ClO4)2(H2O)2]·[Cu2L1(ClO4)2(H2O)2 ]N3 (2), [Zn4L2 (H2O)2]·(ClO4)4 (3) and [Zn2L2(N3)2]CH3CN (4) (where H2L1 and H2L2 are the [2 + 2] condensation products of 2,6-diformyl-4-flurophenol with 1,3-diaminopropane and 1,4-diaminobutane, respectively), have been synthesized and characterized. The variable-temperature magnetisms of complexes 1 and 2 show that there are antiferromagnetic couplings between the two metal centers in both complexes, and the strongly electron-withdrawing fluorine groups in H2L weaken the antiferromagnetic exchange.

Cheng, Q. R.; Zhou, H.; Pan, Z. Q.; Liao, G. Y.; Xu, Z. G.

2014-09-01

17

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

NASA Astrophysics Data System (ADS)

Influence of chemical substitution in the Fe 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.

Suzuki, Atsushi; Iguchi, Motoi; Oku, Takeo; Fujiwara, Motoyasu

2010-04-01

18

Syntheses, structures, and magnetic properties of three Fe(II) complexes with reduced radical ligands  

Microsoft Academic Search

Three new Fe(II) complexes [Fe(HIM2py)2(SCN)2] (1), [Fe(HIM2py)2(H2O)2](ClO4)2·2H2O (2), and [Fe(HIM2py)2(4,4-bipy)](ClO4)2·3CH3CH2OH (3) (4,4-bipy=4,4?-bipyridine, HIM2py=1-hydroxyl-2(2?-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole) have been synthesized and characterized structurally as well as magnetically. The X-ray analysis reveals that HIM2py ligands are coordinated to the metal ions as an unusual six-membered didentate chelate with the ?2N(py), O(HIM) mode. Fe(II) ions in complex 3 are bridged by 4,4-bipy, leading to a 1D

Xiao-Ling Wang; Pei-Pei Yang; Zong-Wei Li; Li-Cun Li; Dai-Zheng Liao

2009-01-01

19

Synthesis, structures, and magnetic properties of tetranuclear CuII-LnIII complexes.  

PubMed

The copper(II)-gadolinium(III) and copper(II)-terbium(III) complexes studied in this report derive from disymmetric trianionic ligands abbreviated H3Li (i = 4-6). These ligands are obtained through reaction of different aldehydes with "half-units" having an amide function, the latter resulting from the monocondensation of different diamines with phenyl 2-hydroxy-3-methoxybenzoate. Upon deprotonation, the Li ligands (i = 4-10) possess an inner N2O2 coordination site with one amido, one imine, and two phenoxo functions, an outer O2O2 or O2O coordination site, and an amido oxygen atom positioned out of these two sites. The trianionic character of such ligands yields original anionic complexes in the presence of copper(II) or nickel(II) ions, with a 1/1 L/M stoichiometry. The crystal and molecular structures of four complexes, two 3d (1, 5) and two 3d-4f (12, 13) complexes, have been determined. Complex 1 crystallizes in the monoclinic space group C2/c: a = 27.528(2) A, b = 7.0944(7) A, c = 22.914(2) A, beta = 92.130(6) degrees , V = 4471.9(7) A(3), Z = 8 for C(21.5)H(27)CuKN(2)O(6.5). Complex 5 crystallizes in the monoclinic space group P2(1)/n (No. 14): a = 11.0760(9) A, b = 21.454(2) A, c = 15.336(1) A, beta = 101.474(1) degrees , V = 3571.5(5) A(3), Z = 4. Complex 12 crystallizes in the triclinic space group P (No. 2): a = 8.682(2) A, b = 11.848(2) A, c = 11.928(2) A, alpha = 81.77(3) degrees , beta = 89.17(3) degrees , gamma = 85.49(3) degrees , V = 1210.6(4) A(3), Z = 2 for C20H22CuN5O11Tb. Complex 13 belongs to the monoclinic space group C2/c: a = 25.475(5)A, b = 12.934(3)A, c = 15.023(3) A, beta = 91.06(3) degrees , V = 4949.02A3, Z = 8 for C21H25CuN4O12Tb. The structural determinations confirm that the dinuclear entities involved in 12 and 13 are disposed in a head-to-tail arrangement to give tetranuclear complexes in which the copper and lanthanide ions are positioned at the vertexes of a rectangle. In the [Cu-Gd]2 species, there are two different ferromagnetic Cu-Gd interactions. The stronger one is supported by the double phenoxo bridge (CuO2Gd) while the weaker one corresponds to the single amido bridge (Cu-N-C-O-Gd). Replacement of gadolinium ions with anisotropic terbium ions yields tetranuclear entities showing slow relaxation of magnetization and magnetization hysteresis. Detailed relaxation and hysteresis loop studies establish single-molecule magnet (SMM) behavior which is influenced by weak intermolecular interactions. PMID:16499353

Costes, Jean-Pierre; Auchel, Magali; Dahan, Françoise; Peyrou, Viviane; Shova, Sergiu; Wernsdorfer, Wolfgang

2006-03-01

20

Versatile lanthanide-azide complexes with azide/carboxylate/hydroxy mixed bridged chain exhibiting magnetic and luminescent properties  

SciTech Connect

Two new lanthanide-azide complexes, [Ln{sub 2}(N{sub 3})(isonic){sub 2}(OH){sub 3}(Hisonic)(H{sub 2}O)]{sub n} (Ln=Yb for 1 and Tb for 2, isonic=isonicotinate), were obtained in hydrothermal condition. X-ray diffraction analysis indicated the two complexes are isomorphic chain structure in which the Ln{sup III} ions are mixed bridged by the azide anions, hydroxyl anions and carboxylate groups of the isonicotinate ligands. Further studies indicated weak antiferromagnetic interactions between the Ln{sup III} ions in 1 and 2, and complex 2 exhibit green sensitized Luminescent character of Tb{sup III} ion. - Graphical abstract: Two new 1D lanthanide-azide complexes, [Ln{sub 2}(N{sub 3})(isonic){sub 2}(OH){sub 3}(Hisonic)(H{sub 2}O)]{sub n} (Ln=Yb{sup III} for 1 and Tb{sup III} for 2, isonic=isonicotinate), were synthesized by hydrothermal reaction and exhibit interesting magnetism and fluorescence properties. Highlights: Black-Right-Pointing-Pointer The research provided a new method for synthesizing lanthanide-azide complexes. Black-Right-Pointing-Pointer The complexes have an interesting azide/hydroxyl/carboxylate mixed bridged1D chain structure. Black-Right-Pointing-Pointer The antiferromagnetic coupling between the complexes and 2 displays green luminescence.

Wang Haichao; Xue Min; Guo Qian [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Zhao Jiongpeng, E-mail: horryzhao@yahoo.com [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Liu Fuchen, E-mail: fuchenliutj@yahoo.com [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Lanzhou Petrochemical College of Vocational Technology 730060 (China); Ribas, Joan [Inorganica Universitat de Barcelona, Diagonal, 6487, 08028-Barcelona (Spain)

2012-03-15

21

Study of the luminescent and magnetic properties of a series of heterodinuclear [Zn(II)Ln(III)] complexes.  

PubMed

Herein, we report the synthesis, structural investigation, and magnetic and photophysical properties of a series of 13 [Zn(II)Ln(III)] heterodinuclear complexes, which have been obtained employing a Schiff-base compartmental ligand derived from o-vanillin [H(2)valpn = 1,3-propanediylbis(2-iminomethylene-6-methoxy-phenol)]. The complexes have been synthesized starting from the [Zn(valpn)(H(2)O)] mononuclear compound and the corresponding lanthanide nitrates. The crystallographic investigation indicated two structural types: the first one, [Zn(H(2)O)(valpn)Ln(III)(O(2)NO)(3)], contains 10-coordinated Ln(III) ions, while in the second one, [Zn(ONO(2))(valpn)Ln(III)(H(2)O)(O(2)NO)(2)]·2H(2)O, the rare earth ions are nine-coordinated. The Zn(II) ions always display a square-pyramidal geometry. The first structural type encompasses the larger Ln ions (4f(0)-4f(9)), while the second is found for the smaller ions (4f(8)-4f(11)). The dysprosium derivative crystallizes in both forms. Luminescence studies for the heterodinuclear compounds containing Nd(III), Sm(III), Tb(III), Dy(III), and Yb(III) revealed that the [Zn(valpn)(H(2)O)] moiety acts as an antenna. The magnetic properties for the paramagnetic [Zn(II)Ln(III)] complexes have been investigated. PMID:21634383

Pasatoiu, Traian D; Tiseanu, Carmen; Madalan, Augustin M; Jurca, Bogdan; Duhayon, Carine; Sutter, Jean Pascal; Andruh, Marius

2011-07-01

22

Targeted crystal growth of rare Earth intermetallics with synergistic magnetic and electrical properties: structural complexity to simplicity.  

PubMed

The single-crystal growth of extended solids is an active area of solid-state chemistry driven by the discovery of new physical phenomena. Although many solid-state compounds have been discovered over the last several decades, single-crystal growth of these materials in particular enables the determination of physical properties with respect to crystallographic orientation and the determination of properties without possible secondary inclusions. The synthesis and discovery of new classes of materials is necessary to drive the science forward, in particular materials properties such as superconductivity, magnetism, thermoelectrics, and magnetocalorics. Our research is focused on structural characterization and determination of physical properties of intermetallics, culminating in an understanding of the structure-property relationships of single-crystalline phases. We have prepared and studied compounds with layered motifs, three-dimensional magnetic compounds exhibiting anisotropic magnetic and transport behavior, and complex crystal structures leading to intrinsically low lattice thermal conductivity. In this Account, we present the structural characteristics and properties that are important for understanding the magnetic properties of rare earth transition metal intermetallics grown with group 13 and 14 metals. We present phases adopting the HoCoGa5 structure type and the homologous series. We also discuss the insertion of transition metals into the cuboctahedra of the AuCu3 structure type, leading to the synthetic strategy of selecting binaries to relate to ternary intermetallics adopting the Y4PdGa12 structure type. We provide examples of compounds adopting the ThMn12, NaZn13, SmZn11, CeCr2Al20, Ho6Mo4Al43, CeRu2Al10, and CeRu4Al16-x structure types grown with main-group-rich self-flux methods. We also discuss the phase stability of three related crystal structures containing atoms in similar chemical environments: ThMn12, CaCr2Al10, and YbFe2Al10. In addition to dimensionality and chemical environment, complexity is also important in materials design. From relatively common and well-studied intermetallic structure types, we present our motivation to work with complex stannides adopting the Dy117Co57Sn112 structure type for thermoelectric applications and describe a strategy for the design of new magnetic intermetallics with low lattice thermal conductivity. Our quest to grow single crystals of rare-earth-rich complex stannides possessing low lattice thermal conductivity led us to discover the new structure type Ln30Ru4+xSn31-y (Ln = Gd, Dy), thus allowing the correlation of primitive volumes with lattice thermal conductivities. We highlight the observation that Ln30Ru4+xSn31-y gives rise to highly anisotropic magnetic and transport behavior, which is unexpected, illustrating the need to measure properties on single crystals. PMID:25730512

Schmitt, Devin C; Drake, Brenton L; McCandless, Gregory T; Chan, Julia Y

2015-03-17

23

On-off optical switching of the magnetic and structural properties in a spin-crossover complex  

NASA Astrophysics Data System (ADS)

A photoexcitation is one of the promising external fields to control the material phases. Here, the authors have demonstrated that the magnetic and structural properties of a spin-crossover complex, Fe(phen)2(NCS)2 (phen=1,10-phenanthroline), can be reversibly switched by the on-off action of the continuous photoexcitation at the same temperature. The structural data suggest that the density of the high-spin Fe2+ in the photoinduced phase is about 0.88. Suppressed atomic vibrations of the photoinduced phase exclude the conventional heating effect as the origin for the observed optical switching.

Kato, K.; Takata, M.; Moritomo, Y.; Nakamoto, A.; Kojima, N.

2007-05-01

24

Heteronuclear complexes of macrocyclic oxamide with co-ligands: syntheses, crystal structures, and magnetic properties.  

PubMed

Four heteronuclear complexes Mn(CuL)2(SCN)2 (1), {[Mn(CuL)2(mu-dca)2].2H2O}n (2), Zn(CuL)2(SCN)2 (3), and [Fe(CuL)(N3)2]2 (4) incorporating macrocyclic oxamide ligands have been synthesized and structurally characterized. L is the dianion of diethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo[1,4,8,11]-tetraazacyclotetradecine-13,18-dicarboxylate, and dca is the dicyanamide. The structure of 1 or 3 consists of oxamido-bridged trinuclear [MIICuII2] molecules (for 1, M is the manganese(II) ion, and for 3, M is the zinc(II) ion). Both of them consist of 1D supramolecuar chains via pi-pi interactions. The structure of 2 also has the oxamido-bridged trinuclear [MnIICuII2] structure units and consists of 2D layers formed by the linkage of copper(II) and manganese(II) atoms via the oxamido and mu1, 5-dca bridges. Complex 4 consists of oxamido-bridged tetranuclear [FeII2CuII2] molecules and arranges in 1D chains. Different co-ligands may result in different structures in this macrocyclic oxamide system. The variable-temperature magnetic susceptibility measurements (2-300 K) of 1 and 2 both show the pronounced antiferromagnetic interactions between the copper(II) and manganese(II) ions. PMID:17243761

Zhu, Li-Na; Xu, Na; Zhang, Wei; Liao, Dai-Zheng; Yoshimura, Kazuyoshi; Mibu, Ko; Jiang, Zong-Hui; Yan, Shi-Ping; Cheng, Peng

2007-02-19

25

Structural and magnetic properties of In1-xMnxSb: Effect of Mn complexes and MnSb nanoprecipitates  

NASA Astrophysics Data System (ADS)

Structural and magnetic properties of the group III-V diluted magnetic semiconductor In1-xMnxSb with x = 0.005-0.06, including the nuclear magnetic resonance (NMR) investigations, are reported. Polycrystalline In1-xMnxSb samples were prepared by direct alloying of indium antimonide, manganese and antimony, followed by a fast cooling of the melt with a rate of 10-12 K/s. According to the X-ray diffraction data, part of Mn is substituted for In, forming the In1-xMnxSb matrix. Atomic force microscopy and scanning tunneling microscopy investigations provide evidence for the presence of microcrystalline MnSb inclusions (precipitates), having a size of ˜100-600 nm, and the fine structure of nanosize grains with a Gaussian distribution around the diameter of ˜24 nm. According to the NMR spectra, the majority of Mn enters the MnSb inclusions. In addition to the single Mn ions, which contribute to the magnetization M (T) only in the low-temperature limit of T < 10-20 K, and MnSb nanoprecipitates responsible for the ferromagnetic (FM) properties of In1-xMnxSb, a superparamagnetic (SP) contribution of atomic-size magnetic Mn complexes (presumably dimers) has been established. The fraction of the MnSb phase, ? ˜ 1-4%, as well as the concentration, nsp ˜ (0.8-3.2) × 1019 cm-3, and the magnetic moment of the Mn dimers, ? ˜ 8-9 ?B, are determined. The solubility limit of Mn in the InSb matrix, NSL ˜ 1020 cm-3, is estimated. Hysteresis in low (H < 500 Oe) magnetic fields and saturation of the magnetization in high (H > 20 kOe) magnetic fields are observed, indicating a presence of the SP and FM contributions to the dependence of M (H) up to T ˜ 500 K. The hysteresis is characterized by the coercivity field, Hc, decreasing between ˜100 and 75 Oe when T is increased from 5 to 510 K. The values of Hc are in reasonable agreement with the effect of the largest MnSb inclusions. The maximum of M (T), measured in the zero-field-cooled and the field-cooled conditions in a weak field of 500 Oe, is observed at T ˜ 510 K and is attributable to the Hopkinson effect.

Kochura, A. V.; Aronzon, B. A.; Lisunov, K. G.; Lashkul, A. V.; Sidorenko, A. A.; De Renzi, R.; Marenkin, S. F.; Alam, M.; Kuzmenko, A. P.; Lähderanta, E.

2013-02-01

26

Crystal Structures and Magnetic Properties of CuX(2)(pdmp)(2) Complexes (X = Br, Cl).  

PubMed

We report the synthesis and the structural and magnetic characterization of two new compounds: dibromobis(pdmp)copper(II), CuBr(2)C(22)H(24)N(4) (1), and dichlorobis(pdmp)copper(II), CuCl(2)C(22)H(24)N(4) (2), where pdmp = 1-phenyl-3,5-dimethylpyrazole. The structures were refined by full-matrix least-squares techniques to R1 = 0.0620 and 0.0777, respectively. Compound 1 belongs to the space group P2(1)/n with a = 8.165(5) Å, b = 10.432(3) Å, c = 13.385(4) Å, beta = 100.12(4) degrees, and Z = 2. Compound 2 belongs to the space group P2(1)/c with a = 8.379(2) Å, b = 22.630(2) Å, c = 12.256(2) Å, beta = 98.43(3) degrees, and Z = 4. It has the same molecular formula as a compound reported previously but a different crystal structure. Detailed single-crystal EPR measurements were performed for single-crystal samples of 1 and 2 at 9 and 35 GHz and at room temperature. The positions and line widths of the EPR lines were measured as a function of the magnetic field orientation in three orthogonal planes. The data were used to study the electronic properties of the copper ions and to evaluate the exchange interactions between them. Our results are discussed in terms of the electronic pathways for superexchange between copper ions, which are provided by the stacking of pyrazole and phenyl rings of neighboring molecules and by hydrogen-halogen bonds. PMID:11671151

Costa-Filho, Antonio J.; Munte, Claudia E.; Barberato, Claudio; Castellano, Eduardo E.; Mattioli, M. P. D.; Calvo, Rafael; Nascimento, Otaciro R.

1999-10-01

27

Formation, Structure and Magnetic Properties of Polymer Matrix Nanocomposites Processed by Thermal Decomposition of the Fe(III)Co(II) Acrylate Complex  

Microsoft Academic Search

Structure and magnetic properties of polymer matrix nanocomposites, processed by pyrolysis of the Fe(III)Co(II) acrylate complex, were investigated. It was shown that thermal transformation of the complex studied consisted of three macrostages: dehydration, solid state polymerisation and decarboxylation of a metallopolymer form. The main products of the decomposition were nanoparticles stabilised by polymeric matrix. The crystalline phases, which were found

M. ?awecka; M. Kopcewicz; A. ?lawska-Waniewska; M. Leonowicz; J. Kozubowski; G. I. Dzhardimalieva; A. S. Rozenberg; A. D. Pomogailo

2003-01-01

28

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

Microsoft Academic Search

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

Michael Andrew Zalich

2005-01-01

29

Dinuclear palladium complexes with two ligand-centered radicals and a single bridging ligand: subtle tuning of magnetic properties.  

PubMed

The facile and tunable preparation of unique dinuclear [(L(?) )Pd?X?Pd(L(?) )] complexes (X=Cl or N3 ), bearing a ligand radical on each Pd, is disclosed, as well as their magnetochemistry in solution and solid state is reported. Chloride abstraction from [PdCl(NNO(ISQ) )] (NNO(ISQ) =iminosemiquinonato) with TlPF6 results in an unusual monochlorido-bridged dinuclear open-shell diradical species, [{Pd(NNO(ISQ) )}2 (?-Cl)](+) , with an unusually small Pd-Cl-Pd angle (ca.?93°, determined by X-ray). This suggests an intramolecular d(8) -d(8) interaction, which is supported by DFT calculations. SQUID measurements indicate moderate antiferromagnetic spin exchange between the two ligand radicals and an overall singlet ground state in the solid state. VT EPR spectroscopy shows a transient signal corresponding to a triplet state between 20 and 60?K. Complex 2 reacts with PPh3 to generate [Pd(NNO(ISQ) )(PPh3 )](+) and one equivalent of [PdCl(NNO(ISQ) )]. Reacting an 1:1 mixture of [PdCl(NNO(ISQ) )] and [Pd(N3 )(NNO(I) (SQ) )] furnishes the 1,1-azido-bridged dinuclear diradical [{Pd(NNO(ISQ) )}2 (?(1) -N;?-N3 ](+) , with a Pd-N-Pd angle close to 127° (X-ray). Magnetic and EPR measurements indicate two independent S=1/2 spin carriers and no magnetic interaction in the solid state. The two diradical species both show no spin exchange in solution, likely because of unhindered rotation around the Pd?X?Pd core. This work demonstrates that a single bridging atom can induce subtle and tunable changes in structural and magnetic properties of novel dinuclear Pd complexes featuring two ligand-based radicals. PMID:25735905

Broere, Daniël L J; Demeshko, Serhiy; de Bruin, Bas; Pidko, Evgeny A; Reek, Joost N H; Siegler, Maxime A; Lutz, Martin; van der Vlugt, Jarl Ivar

2015-04-01

30

Odd-numbered Fe(III) complexes: synthesis, molecular structure, reactivity, and magnetic properties.  

PubMed

Three isostructural disklike heptanuclear FeIII compounds of the general formula [FeIII7(mu3-O)3(L)3(mu-O2CCMe3)6(eta1-O2CCMe3)3(H2O)3], where L represents a di- or triethanolamine moiety, display a three-blade propeller topology, with the central Fe atom representing the axle or axis of the propeller. This motif corresponds to the theoretical model of a frustrated Heisenberg star, which is one of the very few solvable models in the area of frustrated quantum-spin systems and can, furthermore, be converted to an octanuclear cage for the case where L is triethanolamine to give [FeIII8(mu4O)3(mu4-tea)(teaH)3(O2CCMe3)6(N3)3].1/2MeCN.1/2H2O or [FeIII8(mu4O)3(mu4-tea)(teaH)3(O2CCMe3)6(SCN)3].2MeCN when treated with excess NaN3 or NH4SCN, respectively. The core structure is formally derived from that of the heptanuclear compounds by the replacement of the three aqua ligands by an {Fe(tea)} moiety, so that the 3-fold axis of the propeller is now defined by two central FeIII atoms. Magnetic studies on two of the heptanulcear compounds established unequivocally S = 5/2 spin ground state for these complexes, consistent with overall antiferromagnetic interactions between the constituent FeIII ions. PMID:17257017

Ako, Ayuk M; Waldmann, Oliver; Mereacre, Valeriu; Klöwer, Frederik; Hewitt, Ian J; Anson, Christopher E; Güdel, Hans U; Powell, Annie K

2007-02-01

31

Rhenium(IV)-copper(II) heterobimetallic complexes with a bridge malonato ligand. Synthesis, crystal structure, and magnetic properties.  

PubMed

The Re(IV) complex [ReCl4(mal)]2-, in the form of two slightly different salts, (AsPh4)1.5(HNEt3)0.5[ReCl4(mal)] (1a) and (AsPh4)(HNEt3)[ReCl4(mal)] (1b), and the Re(IV)-Cu(II) bimetallic complexes [ReCl4(mu-mal)Cu(phen)2].CH3CN (2), [ReCl4(mu-mal)Cu(bpy)2] (3), and [ReCl4(mu-mal)Cu(terpy)] (4) (mal=malonate dianion, AsPh4=tetraphenylarsonium cation, HNEt3=triethylammonium cation, phen=1,10-phenanthroline, bpy=2,2'-bipyridine and terpy=2,2':6',2' '-terpyridine) have been synthesized and the structures of 1a, 1b, 2, and 3 determined by single-crystal X-ray diffraction. The structures of 1a and 1b are made up of discrete [ReCl4(mal)]2- anions and AsPh4+ and HNEt3+ cations, held together by electrostatic forces and hydrogen bonds. The Re(IV) atom is surrounded by four chloride anions and a bidentate malonate group, in a distorted octahedral environment. The structure of 2 consist of neutral dinuclear units [ReCl4(mu-mal)Cu(phen)2], with the metal ions united through a bridge carboxilato. The environment of Re(IV) is nearly identical to that in the mononuclear complex, and Cu(II) is five coordinate, being surrounded by four nitrogen atoms of two bidentate phen ligands and one oxygen atom of the malonato ligand. In 3, there are also dinuclear units, [ReCl4(mu-mal)Cu(bpy)2], but the Cu(II) ions complete a distorted octahedral coordination by binding with the free malonato oxygen atom of a neighbor unit, resulting in an infinite chain. The magnetic properties of 1-4 were also investigated in the temperature range 2.0-300 K. The magnetic behavior of 1a and 1b is as expected for a Re(IV) complex with a large value of the zero-field splitting (2D ca. 110 cm(-1)). For the bimetallic complexes, the magnetic coupling between Re(IV) and Cu(II) is antiferromagnetic in 2 (J=-0.39 cm(-1)), ferromagnetic in 4 (J=+1.51 cm(-1)), and nearly negligible in 3 (J=-0.09 cm(-1)). PMID:15554648

Cuevas, Alicia; Chiozzone, Raúl; Kremer, Carlos; Suescun, Leopoldo; Mombrú, Alvaro; Armentano, Donatella; De Munno, Giovanni; Lloret, Francesc; Cano, Juan; Faus, Juan

2004-11-29

32

Effects of f-f Interactions on the Single-Molecule Magnet Properties of Terbium(III)-Phthalocyaninato Quintuple-Decker Complexes.  

PubMed

Single-molecule magnet (SMM) properties of terbium(III)-phthalocyaninato quintuple-decker complex TbCdCdTb were studied and were compared with those of other multiple-decker complexes (triple-decker: TbTb, quadruple-decker: TbCdTb) to elucidate the relationship between magnetic dipole interactions and SMM properties. From X-ray crystallography performed with synchrotron radiation, the Tb(III)-Tb(III) distance in TbCdCdTb was determined to be 9.883 Å. From alternating current magnetic studies on TbCdCdTb, the activation energy for spin reversal (?) increased with an increase in the direct current magnetic field (Hdc). This behavior is similar to that of TbCdTb, although the increase in ? for TbCdTb is smaller. On the other hand, for TbTb, which has shortest Tb(III)-Tb(III) distance, ? did not depend on Hdc, indicating that there is a correlation between SMM properties and the strength of the Tb(III)-Tb(III) interactions. By comparing the Zeeman diagrams for multiple-decker complexes, we found that the Tb(III)-Tb(III) interactions affected the magnetic field regions where quantum tunnelling of the magnetization was active. The results obtained from Zeeman diagrams are consistent with the results obtained from the magnetic studies. PMID:25799034

Horii, Yoji; Katoh, Keiichi; Yasuda, Nobuhiro; Breedlove, Brian K; Yamashita, Masahiro

2015-04-01

33

Magnetic properties of cerium monopnictides  

NASA Astrophysics Data System (ADS)

The unusual magnetic properties of Ce-monopnictides are reviewed. CeAs was found to order with a triple- k type I structure. In CeBi, a very anisotropic magnetic excitation spectrum was observed, indicating a strong planar coupling. The unique magnetic properties of CeSb are strongly perturbed by an applied pressure or by the substitution of Ce by La or Y, or Sb by Te, As, Bi proving that they depend drastically on the concentration of p-holes in the valence band. In CeSb, the substitution of Sb by Te yields quite complex phenomena.

Rossat-Mignod, J.; Burlet, P.; Quezel, S.; Effantin, J. M.; Delacôte, D.; Bartholin, H.; Vogt, O.; Ravot, D.

1983-02-01

34

Structural diversity of five new bitriazole-based complexes: luminescence, sorption, and magnetic properties.  

PubMed

Employing an uninvestigated eight N-donor bitriazole ligand, 5'-(pyrazin-2-yl)-2H,4'H-3,3'-bi(1,2,4-triazole) (H2pzbtz), five complexes, {[Zn2(pzbtz)(SO4)(H2O)2]·2H2O}n (), {[Cd(pzbtz)]·3H2O}n (), [Zn3(Hpzbtz)2(SO4)2(H2O)6] (), [Co(Hpzbtz)2(H2O)2] () and {[Co2(pzbtz)2(H2O)2]·4H2O}n (), have been solvothermally synthesised by altering the reaction solvents and temperatures. Complex shows a three-dimensional (3D) framework with a very rare (3,5)-connected fsc-3,5-Cmce-2 topology. Complex exhibits a (4,4)-connected 3D pts framework with 1D channels. Complexes and are discrete trinuclear and mononuclear molecules, respectively. Complex presents a chiral 3D framework based on a novel trinuclear Co3(tr)4 cluster and features an unusual six-connected lcy topology. In the five complexes, H2pzbtz show a very variety of geometrical configurations and coordination modes. Due to the planarity of H2pzbtz, complexes display strong photoluminescence; in particular, features highly selective luminescent sensing for the Cu(2+) ion and nitrobenzene molecule. In addition, shows highly selective adsorption for CO2 over CH4, and exhibits antiferromagnetic exchange interactions among the Co(2+) ions. PMID:25410384

Du, Li-Yun; Wang, Hui; Liu, Ge; Xie, Dong; Guo, Fu-Sheng; Hou, Lei; Wang, Yao-Yu

2015-01-21

35

Thiazolidine4-carboxylic acid and 2-aminothiazoleethanoic acid as ligands. The synthesis, magnetic, e.p.r. and spectral properties of copper(II) complexes  

Microsoft Academic Search

Two complexes formed from CuII acetate and thiazolidine-4-carboxylic acid (4-TCA) and 2-amino-4-thiazoleethanoic acid (ATAA) have been prepared and characterized by magnetic and spectroscopic techniques. The influence of the nature of ligands and solvents upon CuII e.p.r. properties was investigated for these compounds, Spin-Hamiltonian parameters from these data enabled suggestions concerning the structure of these complexes and the binding ability of

Krystyna Gie?zak-Ko?win; Walter Wojciechowski

1996-01-01

36

Structure, photochemistry and magnetic properties of tetrahydrogenated Schiff base chromium(III) complexes.  

PubMed

Four mononuclear chromium(III) complexes [Cr(L(1))(en)]Br0.3Cl0.7 (1), [Cr(L(1))(pr)]Cl (2), [Cr(L(2))(en)]ClO4 (3), [Cr(L(2))(pr)]Cl (4) along with one dinuclear ?-methoxo [Cr(?-OMe)(L1)]2 (5) were synthesized (en=1,2-ethanediamine, pr=1,3-diaminopropane H2L(1)=Tetrahydrosalen=H2[H4]salen=N,N'-bis(2-hydroxybenzyl)-1,2-ethanediamine, H2L(2)=Tetrahydrosalpr=H2[H4]salpr=N,N'-bis(2-hydroxybenzyl)-1,3-diaminopropane). The competitive reactions in the presence of EDTA were carried out and the first-order rate constants k(1)=(5.2±0.2)×10(-3) h(-1)complex 5 exhibits a strong antiferromagnetic coupling with the J=-10.8 cm(-1). PMID:25637815

Liu, Bin; Chai, Jie; Feng, SiSi; Yang, BinSheng

2015-04-01

37

Magnetic Properties of Nanostructures  

NASA Astrophysics Data System (ADS)

The recent development of the superlattice nanowire pattern transfer (SNAP) technique has enabled the fabrication of complex molecular-electronic circuits at unprecedented densities. In this project, we explore the possibility of extending this technique to generate comparably dense arrays of nanoscale giant magnetoresistive (GMR) and tunneling magnetoresistive (TMR) devices. My primary contribution to this project has focused on using a vibrating sample magnetometer (VSM), as well as a superconducting interference device (SQUID) magnetometer to monitor the magnetic properties of the devices as they are processed from thin 2D films into nanostructure arrays. This investigation allows us to investigate both fundamental and technological aspects of the nanopatterning process. For example, the effects of changing surface to volume ratios on the ferromagnetic exchange interaction and the role of various patterning techniques in determining surface chemistry and oxidation of the final nanostructures, respectively. Additionally I have worked on simulations of the materials using NIST's OOMF program, allowing me to compare actual results with theoretical expectations. I am also designing a magneto-optical Kerr effect (MOKE) detector, which will allow faster approximations of magnetic behavior.

Ciraldo, John

2007-10-01

38

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

39

Uranyl and uranyl-3d block cation complexes with 1,3-adamantanedicarboxylate: crystal structures, luminescence, and magnetic properties.  

PubMed

The reaction of 1,3-adamantanedicarboxylic acid (LH2) with uranyl nitrate under solvo-hydrothermal conditions, either alone or in the presence of additional metal cations (Co(2+), Ni(2+), or Cu(2+)) gives a series of nine complexes displaying a wide range of architectures. While [UO2(L)(H2O)]·1.25CH3CN (1) and [UO2(L)(DMF)] (2) are one-dimensional (1D) species analogous to that previously known, [H2NMe2]2[(UO2)2(L)3]·1.5H2O (3), which includes dimethylammonium counterions generated in situ, is a three-dimensional (3D) framework, and [UO2(L)(NMP)] (4) (NMP = N-methyl-2-pyrrolidone) is a braid-shaped 1D polymer. When 3d block metal ions are present and bound to 2,2'-bipyridine (bipy) coligands, their role is reduced to that of decorating species attached to uranyl-containing 1D polymers, as in [UO2M(L)2(bipy)2]·0.5H2O with M = Co (5) or Ni (6), and [(UO2)2Cu2(L)3(NO3)2(bipy)2]·0.5H2O (9), or of counterions, as in [Ni(bipy)3][(UO2)4(O)2(L)3]·3H2O (7), in which a two-dimensional (2D) assembly is built from tetranuclear uranyl-containing building units. In contrast, the heterometallic 3D framework [UO2Cu(L)2] (8) can be isolated in the absence of bipy. The emission spectra measured in the solid state display the usual uranyl vibronic fine structure, with various degrees of resolution and quenching, except for that of complex 7, which shows emission from the nickel(II) centers. The magnetic properties of complexes 5, 6, 8, and 9 were investigated, showing, in particular, the presence of zero-field splitting effects in 6 and weak antiferromagnetic interactions in 9. PMID:25710676

Thuéry, Pierre; Rivière, Eric; Harrowfield, Jack

2015-03-16

40

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

PubMed

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

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

2014-09-01

41

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

42

Magnetic property, DFT calculation, and biological activity of bis[(?(2)-chloro)chloro(1,10-phenanthroline)copper(II)] complex.  

PubMed

The dinuclear complex bis[(?(2)-chloro)chloro(1,10-phenanthroline)copper(II)] (1) was synthesized, and characterized by X-ray, FTIR and thermal analysis. The fitting of magnetic susceptibility and magnetization curve of (1) indicates the occurrence of weak antiferromagnetic exchange interaction between copper(II) ions. The electronic structure has been also determined by density functional theory (DFT) method. Complex (1) displayed potent anticancer activity against B16 (Melanoma), MDA-MB-32 (Breast Adenocarcinoma), A549 (Lung Adenocarcinoma), HT-29 (Colon Adenocarcinoma) and SF (Astrocytoma) cell lines with an average IC50 value of 0.726?g/ml compared to 4.88?g/ml for cisplatin. Complex (1) has a better therapeutic index and toxicological profile than cisplatin, and has demonstrated a potential chemotherapeutic property. PMID:25753321

Mroueh, Mohammad; Daher, Costantine; Hariri, Essa; Demirdjian, Sally; Isber, Samih; Choi, Eun Sang; Mirtamizdoust, Babak; Hammud, Hassan H

2015-04-25

43

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

44

Molecular architectures for trimetallic d/f/d complexes: structural and magnetic properties of a LnNi2 core.  

PubMed

A series of cationic, trimetallic d/f/d complexes have been prepared which use a multidentate, macrocyclic amine phenol ligand to coordinate divalent first row d-block transition metal ions (TM) and lanthanides (Ln) ions in close proximity, desirable for magnetic studies. Isolable complexes of the d/f/d cluster compounds with the formula [Ln(TM)2(bcn)2]ClO4.nH2O, where H3bcn is tris-N, N', N''-(2-hydroxybenzyl)-1,4,7-triazacyclononane, TM = Zn(II) and Ni(II) and Ln = La(III), Nd(III), Gd(III), Dy(III), and Yb(III), were synthesized by a one-pot sequential reaction of stoichiometric amounts of H 3bcn with the TM(II) and Ln(III) metal ions. The spontaneously formed cationic complexes were characterized by a variety of analytical techniques including IR, NMR, +ESI-MS, and EA. The [TM(Hbcn)].nH2O and [TM3(bcn)2].nH2O complexes were also synthesized to probe the building blocks of the d/f/d coaggregated species. The solid-state X-ray crystal structures of [GdNi2(bcn)2(CH3CN)2]ClO4.CH3CN and [GdZn2(bcn)2(CH3CN)2]ClO4.CH3CN were determined to be nearly identical with each TM(II) encapsulated in an octahedral geometry by the N3O3 binding pocket of the bcn (3-) ligand. The eight coordinate Gd(III) was bicapped by two [TM(bcn)](-) moieties and coordinated by two solvent molecules. Because of the isostructurality of the [LnZn2(bcn)2]ClO4.nH2O and [LnNi2(bcn)2]ClO4.nH2O complexes, an empirical approach using the LnZn2 magnetic data was utilized to remove first-order anisotropic contributions from the LnNi2 species. Ferromagnetic spin interactions were determined for the [LnNi2(bcn)2]ClO4.nH2O complexes, where Ln = Gd(III), Dy(III), and Yb(III), while an antiferromagnetic exchange was observed for Ln = Nd(III). PMID:18318481

Barta, Cheri A; Bayly, Simon R; Read, Paul W; Patrick, Brian O; Thompson, Robert C; Orvig, Chris

2008-04-01

45

Dinuclear (Fe(II), Gd(III)) complexes deriving from hexadentate Schiff bases: synthesis, structure, and Mössbauer and magnetic properties.  

PubMed

The dinuclear (Fe(II), Gd(III)) complexes studied in this report derive from hexadentate Schiff base ligands abbreviated H(2)L(i)() (i = 1, 2, 3). H(2)L(1) = N,N'-bis(3-methoxysalicylidene)-1,3-diamino-2,2'-dimethyl-propane, H(2)L(2) = N,N'-bis(3-methoxysalicylidene)-1,2-diamino-2-methylpropane, and H(2)L(3) = N,N'-bis(3-methoxysalicylidene)-1,2-diaminoethane. The crystal and molecular structures of three complexes have been determined at 160 K. Depending on the solvent used in the preparation, L(1)Fe(CH(3)OH)Gd(NO(3))(3)(CH(3)OH)(2), 1, or L(1)Fe((CH(3))(2)CO)Gd(NO(3))(3), 1', is obtained from H(2)L(1). A similar complex, L(2)Fe((CH(3))(2)CO)Gd(NO(3))(3), 2, is obtained from H(2)L(2). Complex 1 crystallizes in the orthorhombic space group Pca2(1) (No. 29): a = 22.141(3) A, b = 9.4159(16) A, c = 15.2075(17) A, V = 3170.4(7) A(3), Z = 4. Complexes 1' and 2 crystallize in the monoclinic space group P2(1)/c (No. 14): 1', a = 9.6264(17) A, b = 19.662(3) A, c = 16.039(3) A, beta = 95.15(2) degrees, V = 3023.6(9) A(3), Z = 4; 2, a = 9.7821(13) A, b = 18.7725(17) A, c = 16.100(2) A, beta = 96.497(16) degrees, V = 2937.5(6) A(3), Z = 4. Complexes 1, 1', and 2 possess an Fe(O(phenoxo))(2-)Gd core. The mononuclear L(3)Fe complex could be prepared from H(2)L(3) but not the related dinuclear (Fe, Gd) species. Mössbauer spectroscopy evidences that the iron center is in the +2 oxidation state for the six complexes. The experimental magnetic susceptibility and magnetization data of complexes 1, 1', and 2 indicate the occurrence of weak Fe(II)-Gd(III) ferromagnetic interactions. Single ion zero-field splitting of the iron(II) 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 (1, J = 0.50 cm(-1), D = 2.06 cm(-1); 1', J = 0.41 cm(-1), D = 3.22 cm(-1); 2, J = 0.08 cm(-1), D = 4.43 cm(-1)). PMID:12033896

Costes, Jean-Pierre; Clemente-Juan, Juan Modesto; Dahan, Françoise; Dumestre, Frédéric; Tuchagues, Jean-Pierre

2002-06-01

46

Stereochemistry for engineering spin crossover: structures and magnetic properties of a homochiral vs. racemic [Fe(N3O2)(CN)2] complex.  

PubMed

The Schiff-base condensation of the R,R-(+)-diamine () with 2,6-diacetyl pyridine in the presence of Fe(II) affords the macrocyclic complex [Fe(dpN3O2)(CN)2] () (dp = diphenyl) with ligand centred chirality comprising of a 1?:?1 mixture of LS 6- and HS 7-coordinate Fe(II) centres. Variable temperature magnetic susceptibility and Mössbauer studies reveal that () undergoes an incomplete thermal SCO transition with a T1/2 = 250 K as well as a LIESST effect. In contrast its racemic counterpart () comprises of mostly LS Fe(II) and exhibits no LIESST properties. PMID:25789944

Wang, Qiang; Venneri, Shari; Zarrabi, Niloofar; Wang, Hongfeng; Desplanches, Cédric; Létard, Jean-François; Seda, Takele; Pilkington, Melanie

2015-04-01

47

Magnetic, electrical, thermal transport, and thermoelectric properties of the ?' and ? complex metallic alloy phases in the Al-Pd-Mn system  

NASA Astrophysics Data System (ADS)

The Al-Pd-Mn system of intermetallics contains complex metallic alloy (CMA) phases, whose crystal structures are based on giant unit cells comprising up to more than a thousand atoms per cell. We performed investigation of the magnetic, electrical, and thermal transport and thermoelectric properties of the ?' phase and the related ? phase on single-crystalline samples grown by the Bridgman technique. The samples are diamagnets with a tiny paramagnetic Curie-like magnetization and an estimated fraction of magnetic Mn atoms about 100 ppm. The electrical resistivity between 300 and 4 K exhibits a temperature variation of less than 2%. The origin of this temperature-compensated resistivity is analyzed in terms of the spectral conductivity model. The thermal conductivity of the samples is small and can be described by the sum of the electronic and lattice contributions, which are of comparable size at room temperature. The lattice contribution can be reproduced by the sum of the Debye term (long-wavelength phonons) and the term due to hopping of localized vibrations. The thermoelectric power is small and negative, compatible with a low concentration of electrons as the majority charge carriers. The studied physical properties of the giant-unit-cell CMA phases in the Al-Pd-Mn system are in many respects intermediate between those of metals or simple intermetallics and quasicrystals, suggesting that both the polytetrahedral local atomic order and the large-scale periodicity influence the physical properties of the material.

Dolinšek, J.; Jegli?, P.; McGuiness, P. J.; Jagli?i?, Z.; Biluši?, A.; Bihar, Ž.; Smontara, A.; Landauro, C. V.; Feuerbacher, M.; Grushko, B.; Urban, K.

2005-08-01

48

Dinuclear copper(II) complexes hold by crab-shaped pincer ligands: Syntheses, structures, luminescent and magnetic properties  

NASA Astrophysics Data System (ADS)

Two Cu(II) complexes with N,N?-(2-hydroxy-5-R-1,3-xylylene)bis(N-(carboxymethyl)glycine (R-H5XTA, R = Cl and Br) ligands have been synthesized and their crystal structures have been analyzed by X-ray diffraction methods. The ligands provide a convenient dinucleating feature with the phenolate oxygen providing the bridging function. The complexes consist of dinuclear copper units, hexahydrate copper ion and solvent water molecules. Thereinto, dimer copper ions show two different geometries as Cu1 distorted octahedron and Cu2 square-based pyramid respectively, which has been confirmed by the solid-state electronic absorption spectrum. The thermal decomposition process consists of the loss of corresponding water molecules below 473 K and follow-up decomposition of the main structures. Under the excitation of 360 nm light, luminescence of ligands is quenched by the coordinated Cu(II) ions and heavy Br atom, respectively. Magnetic study shows that coupling of dinuclear copper ions displays ferromagnetic behavior with the J = +9.03 cm-1.

Feng, Sisi; Ma, Ling; Feng, Guoqin; Jiao, Yuan; Zhu, Miaoli

2014-02-01

49

Magnetic Properties in Nondestructive Testing  

E-print Network

that the magnetic properties of steels de- pend on their composition and heat treatment. Mechanically harder steels. ­ 55 ­ #12;Chapter 4 Magnetic Properties in NDT 4.1.2 Alternative terminology The magnetic induction B to as the coercive field, and BR and MR as the re- manent induction and remanent magnetisation respectively

Cambridge, University of

50

Magnetic Properties of Antiferromagnetic Iron Oxyhydroxides  

NASA Astrophysics Data System (ADS)

Weakly magnetic iron oxyhydroxides such as ferrihydrite, lepidocrocite or goethite are commonly found in diverse geological and environmental setting, including ground waters and streams, sediments, soils, or acid mine drainage. These minerals take part in multiple biological and abiological processes, and can evolve to more magnetic phases such as hematite, maghemite, or magnetite. Therefore, they represent key minerals with regard to paleoclimate, paleoenvironmental, and paleomagnetic studies. At this meeting, we will present low temperature magnetic properties acquired on fully characterized synthetic samples. The complex nature of the magnetism of these minerals is revealed by comparing magnetic data with other types of characterizations such as high-resolution transmission electron microscopy or synchrotron X-ray magnetic circular dichroism (XMCD), or by studying the early-stages of solid-state alteration (under oxidizing or reducing atmosphere). In particular, we will present recent results about the presence of ferri-magnetic nano-clusters in lepidocrocite, and about uncompensated magnetic moments in goethite nanoparticles.

Guyodo, Y. J.; Till, J. L.; Lagroix, F.; Bonville, P.; Penn, R. L.; Sainctavit, P.; Carvallo, C.; ona-Nguema, G.; Morin, G.

2013-12-01

51

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

52

Probing the structural, bonding, and magnetic properties of cobalt coordination complexes: co-benzene, co-pyridine, and co-pyrimidine.  

PubMed

Neutral and anionic Co1,2(benzene)1,2, Co1,2(pyridine)1,2, and Co1,2(pyrimidine)1,2 complexes have been investigated within the framework of an all-electron gradient-corrected density functional theory. The ground-state structures for each size clusters were identified based on the geometry optimization. Meanwhile, their electron affinities and vertical detachment energies were predicted and compared with the experimental values. By analyzing the pattern of highest occupied molecular orbitals (HOMOs), we found that the bond formation of these Co-organic complexes mainly arises from the 3d/4s electrons of the cobalt atoms and the ?-cloud of the organic molecules. More importantly, we presented an approach to map and analyze the Co-organic interactions from another perspective. The scatter plots of the reduced density gradient (RDG) versus ? allow us to identify the different types of interactions, and the maps of the gradient isosurfaces show a rich visualization of chemical bond and steric effects. Their magnetic properties were studied by determining the spin magnetic moments and visualizing the spin density distributions. Finally, the natural population analysis (NPA) charge was calculated to achieve a deep insight into the distribution of electron density and the reliable charge-transfer information. PMID:24219660

Shao, Peng; Kuang, Xiao-Yu; Ding, Li-Ping

2013-12-01

53

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

54

Magnetic properties of polycrystalline diamonds  

Microsoft Academic Search

The remanent magnetism and bulk magnetic properties of polycrystalline diamonds have been investigated. The diamonds are of two distinct types, those occurring together with gem-grade diamonds in kimberlite pipes in S Africa, and carbonados, found in placer deposits notably in Brazil and the Central African Republic. Both types generally possess measurable remanent magnetization, the former stronger than the latter, and

D. W. Collinson

1998-01-01

55

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

E-print Network

Structurally Diverse Copper(II) Complexes of Polyaza Ligands Containing 1,2,3-Triazoles: Site, Florida 32306-4390, United States *S Supporting Information ABSTRACT: Copper(II) acetate mediated coupling, was observed in the copper(II) complexes of L1 -L6 . The preference of copper(II) to two common bidentate 1

Weston, Ken

56

Face-sharing heterotrinuclear M(II)-Ln(III)-M(II) (M = Mn, Fe, Co, Zn; Ln = La, Gd, Tb, Dy) complexes: synthesis, structures, and magnetic properties.  

PubMed

Trinuclear linear 3d-4f-3d complexes (3d = Mn(II), Fe(II), Co(II), Zn(II) and 4f = La(III), Gd(III), Tb(III), Dy(III)) were prepared by using a tripodal nonadentate Schiff base ligand, N,N',N''-tris(2-hydroxy-3-methoxybenzilidene)-2-(aminomethyl)-2-methyl-1,3-propanediamine. The structural determinations showed that in these complexes two distorted trigonal prismatic transition metal complexes of identical chirality are assembled through 4f cations. The Mn and Fe entities crystallize in the chiral space group P2(1)2(1)2(1) as pure enantiomers; the cobalt complexes exhibit a less straightforward behavior. All Mn, Fe, and Co complexes experience M(II)-Ln(III) ferromagnetic interactions. The Mn-Gd interaction is weak (0.08 cm(-1)) in comparison to the Fe-Gd (0.69 cm(-1)) and Co-Gd (0.52 cm(-1)) ones while the single ion zero field splitting (ZFS) term D is larger for the Fe complexes (5.7 cm(-1)) than for the cobalt ones. The cobalt complexes behave as single-molecules magnets (SMMs) with large magnetization hysteresis loops, as a consequence of the particularly slow magnetic relaxation characterizing these trinuclear molecules. Such large hysteresis loops, which are observed for the first time in Co-Ln complexes, confirm that quantum tunnelling of the magnetization does not operate in the Co-Gd-Co complex. PMID:20446714

Yamaguchi, Tomoka; Costes, Jean-Pierre; Kishima, Yukana; Kojima, Masaaki; Sunatsuki, Yukinari; Bréfuel, Nicolas; Tuchagues, Jean-Pierre; Vendier, Laure; Wernsdorfer, Wolfgang

2010-10-18

57

First-principle predictions of magnetic properties for a complex and strongly related to quasicrystalline phase: ?-Al 4Mn  

NASA Astrophysics Data System (ADS)

First-principle spin-polarized electronic structure calculations have been performed in the structure of ?-Al 4Mn, a crystalline phase of 568 atoms per cell, considered to be closely related to the icosahedral quasicrystalline i-AlMn. It is found that the ferromagnetic state in this structure is more stable than corresponding paramagnetic one, being only about 156 meV/cell lower in energy. The average magnetic moment is predicted of 0.432 ? B per Mn atom and we show that its formation is governed by a local Stoner criterion. A creation of Hume-Rothery pseudogap nearby the Fermi level due to strong Al-sp-Mn-d hybridization in crystalline intermetallic compound is the origin of partially suppressed magnetic moment on all inequivalent Mn sites.

Nguyen-Manh, D.; Trambly de Laissardière, G.

2003-06-01

58

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

Microsoft Academic Search

Magnetism has interested physicists for decades, but magnetism through molecules is quite recent. One of the active areas of molecular magnetism is the design of new materials with unusual, but predictable magnetic properties. We show how simple orbital considerations permit the description of unpaired electrons in molecular complexes, allow us to foresee their interactions through molecular bridges, and to obtain

Wanru Zhang

1995-01-01

59

Magnetic properties of layered antiferromagnets  

NASA Astrophysics Data System (ADS)

Magnetic properties of layered antiferromagnets have been studied using correlated effective field (CEF) theory developed by M. E. Lines. This theory goes beyond mean-field theory and correctly reproduces the experimental results. The theory is used here to interpret the magnetic order parameter and the susceptibilities of the FePS3 compound, which is a layered antiferromagnet with a marked Ising anisotropy.

Chatterjee, Ibha

1995-02-01

60

Superconductivity and Magnetism: Materials Properties  

E-print Network

.g. within high-Tc superconductivity, magnetic superconductors, MgB2, CMR materials, nanomagnetism and spin#12;#12;Superconductivity and Magnetism: Materials Properties and Developments #12;Copyright 2003 Risø National Laboratory Roskilde, Denmark ISBN 87-550-3244-3 ISSN 0907-0079 #12;Superconductivity

61

Magnetic Properties of Diabase Dikes  

Microsoft Academic Search

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

D. W. Strangway

1961-01-01

62

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

63

A One-dimensional Nickel(III) Chain Complex Showing Ferromagnetic Ordering: Crystal Structure and Magnetic Property  

E-print Network

A One-dimensional Nickel(III) Chain Complex Showing Ferromagnetic Ordering: Crystal Structure-membered nickel- containing rings are slightly puckered, as have been found with other [M(mnt)2]nÃ? structures.10 The nearest S... S, S... Ni and Ni... Ni distances are of 3.73, 3.63 and 3.96 A within the [Ni(mnt)2]Ã? anion

Gao, Song

64

Tuning the Magnetic Properties of Nanoparticles  

PubMed Central

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

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

2013-01-01

65

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

66

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

67

Emergent properties of magnetic materials  

NASA Astrophysics Data System (ADS)

In Tolstoy's War and Peace, history is presented as a tapestry spun from the daily interactions of large numbers of individuals. Even if one understands individuals, it is very difficult to predict history. Similarly, the interactions of large numbers of electrons give rise to properties that one would not initially guess from their microscopic interactions. During the course of my dissertation, I have explored emergent phenomena in a number of contexts. In ZnCr2O4, geometric frustration gives rise to a plethora of equivalent ground states. From these, a lower dimensional set of collinear spins on hexagons are selected to form the building blocks of the lattice. In MgTi2O4, quantum spins dimerize and form a unique chiral ordering pattern on the spinel lattice. Descending into two dimensions, differences in size and charge give rise to an ordering between triangular layers of magnetic and nonmagnetic ions. This triangular lattice allows for the possibility of observing the RVB spin liquid state, or perhaps a valence bond crystal and initial measurements are promising. Also, on the spinel lattice, ionic ordering gives rise to one dimensional chains with their own interesting physics. Finally, in the SrCoxTi1-x O3, system we find that upon reduction, tiny clusters of Co metal precipitate out and chemical inhomogeneity on the microscale may determine much of the physics. This has relevance to a number of recent claims of room temperature ferromagnism in dilute magnetic systems. In all of these systems, complex behavior emerges from well understood microscopic behavior. For me, this is the fascination of strongly correlated electronic systems.

Ratcliff, William Davis, II

68

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

69

Tetraanionic biphenyl lanthanide complexes as single-molecule magnets.  

PubMed

Inverse sandwich biphenyl complexes [(NN(TBS))Ln]2(?-biphenyl)[K(solvent)]2 [NN(TBS) = 1,1'-fc(NSi(t)BuMe2)2; Ln = Gd, Dy, Er; solvent = Et2O, toluene; 18-crown-6], containing a quadruply reduced biphenyl ligand, were synthesized and their magnetic properties measured. One of the dysprosium biphenyl complexes was found to exhibit antiferromagnetic coupling and single-molecule-magnet behavior with Ueff of 34 K under zero applied field. The solvent coordinated to potassium affected drastically the nature of the magnetic interaction, with the other dysprosium complex showing ferromagnetic coupling. Ab initio calculations were performed to understand the nature of magnetic coupling between the two lanthanide ions bridged by the anionic arene ligand and the origin of single-molecule-magnet behavior. PMID:25695369

Huang, Wenliang; Le Roy, Jennifer J; Khan, Saeed I; Ungur, Liviu; Murugesu, Muralee; Diaconescu, Paula L

2015-03-01

70

Two binuclear cyanide-bridged Cr(III)-Mn(III) complexes based-on [Cr(2,2'-bipy)(CN)4]- building block: synthesis, crystal structures and magnetic properties.  

PubMed

Tetracyanide building block [Cr(2,2'-bipy)(CN)4]- and two bicompartimental Schiff-base based manganese(III) compounds have been employed to assemble cyanide-bridged heterometallic complexes, resulting in two cyanide-bridged CrIII-MnIII complexes: [Mn(L1)(H2O)][Cr(2,2'-bipy)(CN)4]·CH3OH·2.5H2O (1) and [Mn(L2)(H2O)][Cr(2,2'-bipy)(CN)4]·CH3OH·3H2O (2) (L1 = N,N'-(1,3-propylene)-bis(3-methoxysalicylideneiminate), L2 = N,N'-ethylene-bis(3-ethoxysalicylideneiminate)). Single X-ray diffraction analysis shows their similar cyanide-bridged binuclear structures, in which the cyanide precursor acting as monodentate ligand connects the manganese(III) ion. The binuclear complexes are self-complementary through coordinated aqua ligand and the free O4 compartment from the neighboring complex, giving H-bond linking dimer structure. Investigation over magnetic properties reveals the antiferromagnetic magnetic coupling between the cyanide-bridged Cr(III) and Mn(III) ions. A best-fit to the magnetic susceptibilities of these two complexes leads to the magnetic coupling constants J = -5.95 cm-1, j = -0.61 cm-1 (1) and J = -4.15 cm-1, j = -0.57 cm-1 (2), respectively. PMID:25830979

Zhanga, Daopeng; Kong, Lingqian; Zhang, Hongyan

2015-01-01

71

Synthesis, structures, and magnetic properties of face-sharing heterodinuclear Ni(II)-Ln(III) (Ln = Eu, Gd, Tb, Dy) complexes.  

PubMed

Heterodinuclear [(Ni (II)L)Ln (III)(hfac) 2(EtOH)] (H 3L = 1,1,1-tris[(salicylideneamino)methyl]ethane; Ln = Eu, Gd, Tb, and Dy; hfac = hexafluoroacetylacetonate) complexes ( 1.Ln) were prepared by treating [Ni(H 1.5L)]Cl 0.5 ( 1) with [Ln(hfac) 3(H 2O) 2] and triethylamine in ethanol (1:1:1). All 1.Ln complexes ( 1.Eu, 1.Gd, 1.Tb, and 1.Dy) crystallized in the triclinic space group P1 (No. 2) with Z = 2 with very similar structures. Each complex is a face-sharing dinuclear molecule. The Ni (II) ion is coordinated by the L (3-) ligand in a N 3O 3 coordination sphere, and the three phenolate oxygen atoms coordinate to an Ln (III) ion as bridging atoms. The Ln (III) ion is eight-coordinate, with four oxygen atoms of two hfac (-)'s, three phenolate oxygen atoms of L (3-), and one ethanol oxygen atom coordinated. Temperature-dependent magnetic susceptibility and field-dependent magnetization measurements showed a ferromagnetic interaction between Ni (II) and Gd (III) in 1.Gd. The Ni (II)-Ln (III) magnetic interactions in 1.Eu, 1.Tb, and 1.Dy were evaluated by comparing their magnetic susceptibilities with those of the isostructural Zn (II)-Ln (III) complexes, [(ZnL)Ln(hfac) 2(EtOH)] ( 2.Ln) containing a diamagnetic Zn (II) ion. A ferromagnetic interaction was indicated in 1.Tb and 1.Dy, while the interaction between Ni (II) and Eu (III) was negligible in 1.Eu. The magnetic behaviors of 1.Dy and 2.Dy were analyzed theoretically to give insight into the sublevel structures of the Dy (III) ion and its coupling with Ni (II). Frequency dependence in the ac susceptibility signals was observed in 1.Dy. PMID:18512903

Yamaguchi, Tomoka; Sunatsuki, Yukinari; Ishida, Hiroyuki; Kojima, Masaaki; Akashi, Haruo; Re, Nazzareno; Matsumoto, Naohide; Pochaba, Andrzej; Mrozi?ski, Jerzy

2008-07-01

72

Complex structures adapted to magnetic flows  

E-print Network

Let $M$ be a compact real-analytic manifold, equipped with a real-analytic Riemannian metric $g,$ and let $\\beta$ be a closed real-analytic 2-form on $M$, interpreted as a magnetic field. Consider the Hamiltonian flow on $T^*M$ that describes a charged particle moving in the magnetic field $\\beta$. Following an idea of T. Thiemann, we construct a complex structure on a tube inside $T^*M$ by pushing forward the vertical polarization by the Hamiltonian flow "evaluated at time $i$." This complex structure fits together with $\\omega-\\pi^*\\beta$ to give a Kaehler structure on a tube inside $T^*M$. We describe this magnetic complex structure in terms of its $(1,0)$-tangent bundle, at the level of holomorphic functions, and via a construction using the embeddings of Whitney-Bruhat and Grauert, which is a magnetic analogue to the analytic continuation of the geometric exponential map. We describe an antiholomorphic intertwiner between this complex structure and the complex structure induced by $-\\beta$, and we give two formulas for local Kaehler potentials, which depend on a local choice of vector potential 1-form for $\\beta$. When $\\beta=0$, our magnetic complex structure is the adapted complex structure of Lempert-Sz\\H{o}ke and Guillemin-Stenzel. We compute the magnetic complex structure explicitly for constant magnetic fields on $\\mathbb{R}^{2}$ and $S^{2}.$ In the $\\mathbb{R}^{2}$ case, the magnetic adapted complex structure for a constant magnetic field is related to work of Kr\\"otz-Thangavelu-Xu on heat kernel analysis on the Heisenberg group.

Brian C. Hall; William D. Kirwin

2012-01-10

73

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

PubMed

We establish the coordination potential of the Schiff base ligand (2-methoxy-6-[(E)-2'-hydroxymethyl-phenyliminomethyl]-phenolate (H2L)) via the isolation of various M(II)-Ln(III) complexes (where M(II) = Ni or Zn and Ln(III) = La or Pr or Gd). Single crystals of these five complexes were isolated and their solid state structures were determined by single crystal X-ray diffraction. Structural determination revealed molecular formulae of [NiGd(HL)2(NO3)3] (1), [NiPr(HL)2(NO3)3] (2) and [Ni2La(HL)4(NO3)](NO3)2 (3), [Zn2Gd(HL)4(NO3)](NO3)2 (4), and [Zn2Pr(HL)4(NO3)](NO3)2 (5). Complexes and were found to be neutral heterometallic dinuclear compounds, whereas 3-5 were found to be linear heterometallic trinuclear cationic complexes. Direct current (dc) magnetic susceptibility and magnetization measurements conclusively revealed that complexes 1 and 4 possess a spin ground state of S = 9/2 and 7/2 respectively. Empirically calculated ??MT derived from the variable temperature susceptibility data for all complexes undoubtedly indicates that the Ni(II) ion is coupled ferromagnetically with the Gd(III) ion, and antiferromagnetically with the Pr(III) ion in 1 and 2 respectively. The extent of the exchange interaction for was estimated by fitting the magnetic susceptibility data using the parameters (g = 2.028, S = 9/2, J = 1.31 cm(-1) and zJ = +0.007), supporting the phenomenon observed in an empirical approach. Similarly using a HDVV Hamiltonian, the magnetic data of 3 and 4 were fitted, yielding parameters g = 2.177, D = 3.133 cm(-1), J = -0.978 cm(-1), (for 3) and g = 1.985, D = 0.508 cm(-1) (for 4). The maximum change in magnetic entropy (-?Sm) estimated from the isothermal magnetization data for was found to be 5.7 J kg(-1) K(-1) (?B = 7 Tesla) at 7.0 K, which is larger than the -?Sm value extracted from 4 of 3.5 J kg(-1) K(-1) (?B = 7 Tesla) at 15.8 K, revealing the importance of the exchange interaction in increasing the overall ground state of a molecule for better MCE efficiency. PMID:25330279

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

2014-12-14

74

Ground State Electronic and Magnetic Properties of a ?3-Oxo Bridged Trinuclear Cu(II) Complex: Correlation to the Native Intermediate of the Multicopper Oxidases  

PubMed Central

The ground state electronic and magnetic properties of one of the possible structures of the trinuclear CuII site in the native intermediate (NI) of the multicopper oxidases, the ?3-oxo bridged structure, are evaluated using the C3-symmetric Cu3II complex, ?3O. ?3O is unique in that no ligand, other than the oxo, contributes to the exchange coupling. However, ?3O has a ferromagnetic ground state, inconsistent with that of NI. Therefore, two perturbations have been considered: protonation of the ?3-oxo ligand and relaxation of the ?3-oxo ligand into the Cu3 plane. Notably, when the oxo-ligand is sufficiently close to the Cu3 plane (< 0.3 Å), the ground state of ?3O becomes antiferromagnetic and can be correlated to that of NI. In addition, the ferromagnetic 4A ground state of ?3O is found from variable-temperature EPR to undergo a zero-field splitting (ZFS) of 2D = -5.0 cm-1, which derives from the second-order anisotropic exchange. This allows evaluation of the ?-to-? excited state exchange pathways and provides experimental evidence that the orbitally-degenerate 2E ground state of the antiferromagnetic ?3O would also undergo a ZFS by the first-order antisymmetric exchange that has the same physical origin as the anisotropic exchange. The important contribution of the ?3-oxo bridge to the ground-to-ground and ground-to-excited state superexchange pathways that are responsible for the isotropic, antisymmetric and anisotropic exchange are discussed. PMID:16241158

Yoon, Jungjoo; Solomon, Edward I.

2008-01-01

75

Structure of the oxygen-evolving complex of photosystem II: information on the S(2) state through quantum chemical calculation of its magnetic properties.  

PubMed

Twelve structural models for the S(2) state of the oxygen-evolving complex (OEC) of photosystem II are evaluated in terms of their magnetic properties. The set includes ten models based on the 'fused twist' core topology derived by polarized EXAFS spectra and two related models proposed in recent mechanistic investigations. Optimized geometries and spin population analyses suggest that Mn(iii), which is most often identified with the manganese ion at site D, is always associated with a penta-coordinate environment, unless a chloride is directly ligated to the metal. Exchange coupling constants were determined by broken-symmetry density functional theory calculations and the complete spectrum of magnetic sublevels was obtained by direct diagonalization of the Heisenberg Hamiltonian. Seven models display a doublet ground state and are considered spectroscopic models for the ground state corresponding to the multiline signal (MLS) of the S(2) state of the OEC, whereas the remaining five models display a sextet ground state and could be related to the g = 4.1 signal of the S(2) state. It is found that the sign of the exchange coupling constant between the Mn centres at positions A and B of the cluster is directly related to the ground state multiplicity, implying that interconversion between the doublet and sextet can be induced by only small structural perturbations. The recently proposed quantum chemical method for the calculation of (55)Mn hyperfine coupling constants is subsequently applied to the S(2) MLS state models and the quantities that enter into the individual steps of the procedure (site-spin expectation values, intrinsic site isotropic hyperfine parameters and projected (55)Mn isotropic hyperfine constants) are analyzed and discussed in detail with respect to the structural and electronic features of each model. The current approach performs promisingly. It reacts sensitively to structural distortions and hence may be able to distinguish between different structural proposals. Thus it emerges as a useful contributor to the ongoing efforts that aim at establishing correlations between the body of spectroscopic data available for the various S(i) states of the OEC and their actual geometric features. PMID:19639153

Pantazis, Dimitrios A; Orio, Maylis; Petrenko, Taras; Zein, Samir; Lubitz, Wolfgang; Messinger, Johannes; Neese, Frank

2009-08-21

76

MAGNETIC AND FLOW PROPERTIES OF HIGH MAGNETIZATION NANOFLUIDS  

Microsoft Academic Search

The paper reviews recent experimental results con- cerning a wide variety of magnetic nanofluids with high saturation magnetization. Magnetic, rheological and magneto-rheological properties are presented and discussed, especially related to nanostructural proc- esses and colloidal stability in applied magnetic field. Ms (A\\/m) saturation magnetization H (A\\/m) intensity of applied magnetic field ?i (-) initial susceptivity (nm) mean magnetic diameter

Ladislau VÉKÁS; Daniela SUSAN-RESIGA; Floriana D. STOIAN; Doina BICA

77

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

78

Magnetism of the oceanic crust: Evidence from ophiolite complexes  

SciTech Connect

The magnetic properties of six ophiolite complexes from around the world, ranging in age from Jurassic to Miocene, are presented. An emphasis is placed in our study on the petrologic and isotopic data from these ophiolite complexes in order to determine first whether the rock samples presently available represent the pristine ocean crust or whether they have been altered subaerially since their formation. Five of the ophiolites are found to be acceptable, and the conclusion is overwhelmingly in favor of a marine magnetic source layer that includes not only the pillow lavas but also the underlying dikes and gabbro. At the moment, however, our observations do not suggest that the magnetic contributions of the basaltic dikes should be overlooked in favor of gabbro. A second important conclusion is that nearly pure magnetite could indeed be a magnetic carrier which contributes to marine magnetic anomanies. It only awaits discovery by deeper ocean crustal penetration by future Deep Sea Drilling Project legs.

Banerjee, S.K.

1980-07-10

79

Rheological properties of magnetic suspensions.  

PubMed

We present results of a theoretical study of the magnetorheological viscosity ? of a suspension versus the applied magnetic field H and shear rate [Formula: see text]. It is supposed that the macroscopic rheological effects are provided by linear chain-like aggregates. Unlike in traditional models, the natural statistical distribution of the chains over the number of particles in them is taken into account. The results obtained explain important features of the rheological ? versus [Formula: see text] law, which has been detected in experiments but qualitatively contradicts known theories of rheological properties of magnetic suspensions. PMID:21694267

Zubarev, A; Iskakova, L

2008-05-21

80

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

81

Trigonal-bipyramidal metal cyanide complexes: a versatile platform for the systematic assessment of the magnetic properties of Prussian blue materials.  

PubMed

Pentanuclear cyanide-bridged clusters of the general formula {[M(tmphen)(2)](3)[M'(CN)(6)](2)} (tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline) have been under investigation in our laboratories for a number of years. These related molecules are conveniently prepared by a building block approach that involves the reaction of mononuclear {M(tmphen)(2)X(2)}(0/2+) species (M = Cr, Mn, Fe, Co, Ni, Zn; X = anion, solvent) with [M'(CN)(6)](3-) anions (M' = Cr, Mn, Fe, Co, Os). The resulting trigonal-bipyramidal (TBP) clusters, consisting of M and M' centers in the equatorial and axial positions, respectively, exhibit diverse properties including those that had previously been observed only for Prussian blue extended phases; these properties include single-molecule magnetism, spin crossover, charge-transfer-induced spin transitions, cyanide linkage isomerism, and magnetic coupling through diamagnetic metal ions. Given that a series of clusters with identical axial cyanometallate units can be prepared, we have been able to establish trends in magnetic coupling for families of clusters with different equatorial metal ions. The crystal packing of the clusters, which involves supramolecular pi-stacking interactions, reveals the origin of the observed differences in the coordination environments and, in several cases, the physical properties of the metal ions in the equatorial sites. Recent work has focused on the use of these molecules as building blocks for magnetic chains and the incorporation of highly anisotropic 5d metal ions such as Os(III) into the TBP core. Such comprehensive studies of small clusters are valuable for understanding and modeling the magnetic behavior of more complicated cyanide materials. PMID:19361244

Funck, Kristen E; Hilfiger, Matthew G; Berlinguette, Curtis P; Shatruk, Michael; Wernsdorfer, Wolfgang; Dunbar, Kim R

2009-04-20

82

Effects of calcination temperature and solution pH value on the structural and magnetic properties of Ba 2Co 2Fe 12O 22 ferrite via EDTA-complexing process  

Microsoft Academic Search

Y-type hexagonal Ba2Co2Fe12O22 was prepared via a simple EDTA-complexing process using corresponding metal nitrates as raw materials and ethylene diamine tetraacetic acid (EDTA) as complexing agent. The decomposition process of the precursor, formation process of Ba2Co2Fe12O22, structure, morphology and magnetic properties of the particles were investigated by thermogravimetric analysis and differential thermal analysis (TGA–DTA), Fourier transform infrared spectroscopy (FT-IR), X-ray

Chunxiang Zhang; Jianshe Shi; Xujie Yang; Lulu De; Xin Wang

2010-01-01

83

Copper(II) cyanido-bridged bimetallic nitroprusside-based complexes: Syntheses, X-ray structures, magnetic properties, {sup 57}Fe Moessbauer spectroscopy and thermal studies  

SciTech Connect

Three heterobimetallic cyanido-bridged copper(II) nitroprusside-based complexes of the compositions [Cu(tet)Fe(CN){sub 5}NO].H{sub 2}O (1), where tet=N,N'-bis(3-aminopropyl)ethylenediamine, [Cu(hto)Fe(CN){sub 5}NO].2H{sub 2}O (2), where hto=1,3,6,9,11,14-hexaazatricyclo[12.2.1.1{sup 6,9}]octadecane and [Cu(nme){sub 2}Fe(CN){sub 5}NO].H{sub 2}O (3), where nme=N-methylethylenediamine, were synthesized and characterized by elemental analyses, {sup 57}Fe Moessbauer and FTIR spectroscopies, thermal analysis, magnetic measurements and single-crystal X-ray analysis. The products of thermal degradation processes of 2 and 3 were studied by XRD, {sup 57}Fe Moessbauer spectroscopy, SEM and EDS, and they were identified as mixtures of CuFe{sub 2}O{sub 4} and CuO. - Three heterobimetallic cyano-bridged copper(II) nitroprusside-based complexes of the general compositions of [Cu(L)Fe(CN){sub 5}NO].xH{sub 2}O, where L=N,N'-bis(3-aminopropyl)ethylenediamine (complex 1), 1,3,6,9,11,14-hexaazatricyclo[12.2.1.1{sup 6,9}]-octadecane (complex 2) and N-methylethylenediamine (complex 3), were synthesized, and fully structurally and magnetically characterized. SEM, EDS, XRD and {sup 57}Fe Moessbauer experiments were used for characterization of thermal decomposition products of complexes 2 and 3.

Travnicek, Zdenek, E-mail: zdenek.travnicek@upol.c [Department of Inorganic Chemistry, Faculty of Science, Palacky University, Tr. 17. listopadu 12, CZ-771 46 Olomouc (Czech Republic); Herchel, Radovan; Mikulik, Jiri [Department of Inorganic Chemistry, Faculty of Science, Palacky University, Tr. 17. listopadu 12, CZ-771 46 Olomouc (Czech Republic); Zboril, Radek [Department of Physical Chemistry, Faculty of Science, Palacky University, Tr. 17. listopadu 12, CZ-771 46 Olomouc (Czech Republic)

2010-05-15

84

Two types of nitrito support for ?4-oxido-bridged [Cu4] complexes: synthesis, crystal structures, magnetic properties and DFT analysis.  

PubMed

Novel nitrito supported and ?4-oxido bridged Cu(II) aggregates have been found in two tetranuclear complexes, [Cu4(?4-O)L2(?1,3-ONO)4] () and [Cu4(?4-O)L2(?1,3-OAc)2(?1,2-NO2)2] (), of the chiral Schiff base HL (HL = 4-methyl-2,6-bis-(1-phenyl-ethylimino)-methylphenol). The structures contain either in situ generated or externally added peripheral ?-nitrito groups, in ?(2)O/O and ?(2)N/O bridging modes. Four NO2(-) bridges in and two AcO(-) co-ligands along with two NO2(-) bridges in are essential for the stabilization of these tetranuclear aggregates. The complexes have been characterized by X-ray crystal structure determination, spectroscopic and magnetic measurements, and density functional theory (DFT) analysis. They are formed from the assembly of two [Cu2L](3+) fragments around a water-derived oxido ligand under the control of nitrite or mixed nitrite/acetate bridges. Variable temperature magnetic susceptibility measurements reveal strong intramolecular antiferromagnetic exchange interactions within the tetranuclear clusters to yield ST = 0 ground state. The capacity of the two different nitrite bridging modes to mediate magnetic coupling has been examined through measurements and numerical fitting procedures, and rationalized by means of DFT calculations. PMID:25729876

Pait, Moumita; Shatruk, Michael; Lengyel, Jeff; Gómez-Coca, Silvia; Bauzá, Antonio; Frontera, Antonio; Bertolasi, Valerio; Ray, Debashis

2015-03-17

85

Terbium(III) and yttrium(III) complexes with pyridine-substituted nitronyl nitroxide radical and different ?-diketonate ligands. Crystal structures and magnetic and luminescence properties.  

PubMed

A terbium(III) complex of nitronyl nitroxide free radical 2-(2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro1H-imidazolyl-1-oxy-3-oxide (NIT2Py), [Tb(acac)3NIT2Py]·0.5H2O (3) (acac = acetylacetonate), was synthesized for comparison with the previously reported [Tb(hfac)3NIT2Py]·0.5C7H16 (1) (hfac = hexafluoroacetylacetonate), together with their yttrium analogues [Y(hfac)3NIT2Py]·0.5C7H16 (2) and [Y(acac)3NIT2Py]·0.5H2O (4). The crystal structures show that in all complexes the nitronyl nitroxide radical acts as a chelating ligand. Magnetic studies show that 3 like 1 exhibits slow relaxation of magnetization at low temperature, suggesting single-molecule magnet behavior. The luminescence spectra show resolved vibronic structure with the main interval decreasing from 1600 cm(-1) to 1400 cm(-1) between 80 and 300 K. This effect is analyzed quantitatively using experimental Raman frequencies. PMID:25148132

Lannes, Anthony; Intissar, Mourad; Suffren, Yan; Reber, Christian; Luneau, Dominique

2014-09-15

86

Synthesis and magnetic properties of copper(II)-lanthanide(III) heterobinuclear complexes with N,N?-bis[3-(dimethylamino)propyl]oxamido as ligand  

NASA Astrophysics Data System (ADS)

Nine new ?-oxamido-bridged copper(II)-lanthanide(III) heterobinuclear complexes, described by the overall formula Cu(dmoxpn)Ln(NO 2phen) 2(NO 3) 3 (Ln=La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er), where dmoxpn denotes N,N'-bis[3-(dimethylamino)propyl]oxamido dianions and NO 2phen represents 5-nitro-1,10-phenanthroline, have been synthesized and characterized by the elemental analyses, molar conductivity measurements and spectroscopic (IR, UV, ESR) studies. The complex Cu(dmoxpn)Gd(NO 2phen) 2(NO 3) 3 was further characterized by variable-temperature magnetic susceptibility (4.2˜300 K) measurements and the magnetic data have also been used to deduce the indicated heterobinuclear structure. The results derived from least-squares fit of the experimental data have confirmed that the adjacent copper(II) and gadolinium(III) ions through the oxamido-bridge in the complex are ferromagnetically coupled with the exchange integral J=+7.8 cm. A plausible mechanism for the ferromagnetic coupling between gadolinium(III) and copper(II) is discussed.

Li, Yan-Tuan; Wu, Qiang-Ming; Yan, Cui-Wei; Zhu, Chun-Yuan

2004-12-01

87

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

88

Solvatomorphs of dimeric transition metal complexes based on the V 4O 12 cyclic anion as building block: Crystalline packing and magnetic properties  

Microsoft Academic Search

Dinuclear [{M(phen)2}2V4O12]·C6H12O·H2O (M=CoII1, MnII2, NiII3 and CuII4) and [{Cu(phen)2}2V4O12]·3.5H2O 5 has been prepared by biphasic and hydrothermal syntheses, respectively. All five structures exhibit the {V4O12}4? cluster in a chair-like configuration, covalently bonded to two [M(phen)2]2+ fragments, producing a super-exchange magnetic phenomenon. The magnetic study of complexes 1–5 shows that they are very weak antiferromagnetically coupled systems, with J values of

V. Paredes-García; S. Gaune; M. Saldías; M. T. Garland; R. Baggio; A. Vega; M. Salah El Fallah; A. Escuer; E. Le Fur; D. Venegas-Yazigi; E. Spodine

2008-01-01

89

Methanolysis and phenolysis routes to Fe6, Fe8, and Fe1) complexes and their magnetic properties: a new type of Fe8 ferric wheel.  

PubMed

Alcoholysis of preformed tetranuclear and hexanuclear iron(III) clusters has been employed for the synthesis of four higher-nuclearity clusters. Treatment of [Fe(4)O(2)(O(2)CMe)(7)(bpy)(2)](ClO(4)) with phenol affords the hexanuclear cluster [Fe(6)O(3)(O(2)CMe)(9)(OPh)(2)(bpy)(2)](ClO(4)) (1). Reaction of [Fe(6)O(2)(OH)(2)(O(2)CR)(10)(hep)(2)] (R = Bu(t) or Ph) with PhOH affords the new "ferric wheel" complexes [Fe(8)(OH)(4)(OPh)(8)(O(2)CR)(12)] [R = Bu(t) (2) or Ph (3)]. Complexes 2 and 3 exhibit the same structure, which is an unprecedented type for Fe(III). In contrast, treatment of [Fe(6)O(2)(OH)(2)(O(2)CBu(t))(10)(hep)(2)] with MeOH leads to the formation of [Fe(10)(OMe)(20)(O(2)CBu(t))(10)] (4), which exhibits the more common type of ferric wheel seen in analogous complexes with other carboxylate groups. Solid-state variable-temperature magnetic susceptibility measurements indicate spin-singlet ground states for complexes 2 and 4. The recently developed semiempirical method ZILSH was used to estimate the pairwise exchange parameters (J(AB)) and the average spin couplings S(A)[empty set].S(B)[empty set] between the Fe(III) centers, providing a clear depiction of the overall magnetic behavior of the molecules. All exchange interactions between adjacent Fe(III) atoms are antiferromagnetic. PMID:14632497

Cañada-Vilalta, Cristina; O'Brien, Ted A; Pink, Maren; Davidson, Ernest R; Christou, George

2003-12-01

90

Magnetic structure and magnetic properties of TbMg  

Microsoft Academic Search

The magnetic properties of the CsCl-type compound TbMg have been studied by means of neutron diffraction and magnetization measurements. At 4.2 K the magnetic structure consists of a magnetic unit cell, which is twice as long in one of the cube directions as the crystallographic cell (a, a, 2a). The magnetic structure entails an antiferromagnetic component perpendicular to the propagation

W. Schäfer; G. Will; K. H. J. Buschow

1977-01-01

91

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

92

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

93

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

94

Electron density measurements in magnetized complex plasmas  

Microsoft Academic Search

This contribution introduces a new experiment for the investigation of magnetized complex plasmas. Its basic features are discussed and first experiments on free-falling dust particles are presented. By means of Langmuir probes and the resonance cone technique, the influence of dust particles on the free electron density is studied. With both methods, significant electron density reductions are observed.

Thomas Trottenberg; Björn Brede; Dietmar Block; Alexander Piel

2004-01-01

95

Magnetic properties of diluted magnetic semiconductors  

NASA Astrophysics Data System (ADS)

A review will be given of the magnetic characteristics of diluted magnetic semiconductors and the relation with the driving exchange mechanisms. II-VI as well as IV-VI compounds will be considered. The relevance of the long-range interaction and the role of the carrier concentration will be emphasized.

de Jonge, W. J. M.; Swagten, H. J. M.

1991-11-01

96

The structure and magnetic properties of amorphous magnetic thin films  

NASA Astrophysics Data System (ADS)

A review of the structural and magnetic properties of amorphous ferromagnetic and ferrimagnetic thin films is presented. An attempt is made to report structural information on atomic and microstructural scales, and to stress its relevance to the magnetic properties of these materials. The more obvious microstructural features of deposited films are not present in the other important type of amorphous magnetic material prepared by rapid quenching from the melt, and present opportunities for differences in structure dependent magnetic properties. In the main, three classes of amorphous magnetic films are considered. Ferromagnetic transition metal (TM) films which are metastable only at temperatures well below room temperature are discussed. Their importance lies in the fact that they clearly represent the most fundamental amorphous phase. Ferromagnetic transition metal-metalloid (TM-Me) alloys have potential applications as magnetically soft materials. These alloys are, perhaps, the most studied amorphous magnetic materials both in deposited thin film and rapidly quenched ribbon forms. Finally, amorphous rare earth-transition metal (RE-TM) films are reviewed. They exhibit a wide variety of magnetic properties encompassing both extremely low and very high coercivities and also perpendicular magnetic anisotropy. The possible application of these materials in various types of device has encouraged much detailed research into their magnetic properties. This has highlighted the importance of preparation conditions and microstructure in defining their properties.

Grundy, P. J.

1980-07-01

97

Synthesis, structures and magnetic properties of polynuclear mixed-valence Mn(II)Mn(III) complexes containing 3-(2-phenol)-5-(pyridin-2-yl)-1,2,4-triazole ligand.  

PubMed

This paper reports the synthesis, crystal structures, and magnetic properties of a series of mixed-valence polynuclear manganese complexes bridged by a dianionic 1,2,4-triazole-based ligand L(2-) (H(2)L = 3-(2-phenol)-5-(pyridin-2-yl)-1,2,4-triazole). Complexes 1 to 3 show a similar binuclear structure, with the central core of [Mn(II)Mn(III)(L)(2)] and some other small molecules also coordinated to the two Mn centers. The two [Mn(II)Mn(III)(L)(2)] subunits can be further connected by different dicarboxylic acids to construct non-charged tetranuclear complexes 4 to 7. In these complexes, each deprotonated dianionic ligand L(2-) acts as a mu(2)-bridged ligand to coordinate two Mn centers via the 1,2,4-triazole ring. Bond valence sum (BVS) calculations and Mn surrounding bond lengths indicate that the Mn center coordinated to the pyridine N atoms in the +2 oxidation state, while another Mn center coordinated to the phenolic O atoms is in the +3 oxidation state. The Mn(III) centre shows Jahn-Teller elongation along one of the axes. Magnetic studies show the presence of ferromagnetic Mn(III)-Mn(II) coupling in the binuclear (1-3) and tetranuclear (4-7) complexes with the magnetic coupling constant (J) ranging from 0.58 to 1.17 cm(-1), based on the Hamiltonian H = -2JS(1) x S(2) (S(1) = 5/2 and S(2) = 2). In all cases both z'J' (intermolecular interactions) and D parameter (Zero Field Splitting of the Mn (III) ion) has been introduced to improve the corresponding fit. The relationship of the coupling interaction between the Mn(II)/Mn(III) and their electronic structures is discussed. PMID:20023874

Liu, Hui; Tian, Jinlei; Kou, Yingying; Zhang, Jingyan; Feng, Li; Li, Dongdong; Gu, Wen; Liu, Xin; Liao, Daizheng; Cheng, Peng; Ribas, Joan; Yan, Shiping

2009-12-21

98

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

99

Mono- and Dinuclear Iron Complexes of Bis(1-methylimidazol-2-yl)ketone (bik): Structure, Magnetic Properties and Catalytic Oxidation Studies  

PubMed Central

The newly synthesized dinuclear complex [FeIII2(?-OH)2(bik)4](NO3)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 FeIII2(?-OH)2 complexes. The bridging hydroxide groups of 1 are strongly hydrogen bonded to a nitrate anion. The 57Fe isomer shift (? = 0.45 mm s?1) and quadrupole splitting (?EQ = 0.26 mm s?1) obtained from Mössbauer 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 = JS1·S2) 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 [FeII(bik)3]2+ species. Variable temperature magnetic susceptibility measurements of [FeII(bik)3](OTf)2 (2) revealed spin crossover behavior. Thermal hysteresis was observed with 2, due to a loss of co-crystallized solvent molecules, as monitored by thermogravimetric analysis. The hysteresis disappears once the solvent is fully depleted by thermal cycling. [FeII(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 O2, 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.

2011-01-01

100

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.

Nancy Thill

101

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

102

Diluted magnetic semiconductors: Novel properties in high magnetic fields  

NASA Astrophysics Data System (ADS)

Diluted magnetic semiconductors, II-VI and IV-VI compounds in which the cation is partially replaced by a magnetic ion such as Mn or a rare earth, combine interesting semiconducting and magnetic properties. At zero applied field, the materials behave like normal semiconductors or semimetals with energy gaps that can be varied with the composition of the magnetic ion. In the presence of an applied field, however, novel properties are observed. These include large field-induced splittings of energy levels, leading to strong Faraday rotations and the possibility of energy-gap tuning by magnetic field, field and temperature-dependent g-factors, large negative magnetoresistance followed at higher fields by a slowly varying positive magnetoresistance, and large paramagnetism with coupling of the magnetic ions by superexchange. Not only can these properties be observed in bulk crystal, but also they suggest promising physics and applications in artificially structured materials.

Anderson, J. R.

1990-06-01

103

Properties of tea-polyphenol-complexed bromelain  

Microsoft Academic Search

Tea polyphenols extracted from Chinese green tea were used to complex and separate bromelain from pineapple juice. The antioxidant activity of tea polyphenols and their effects on the properties of bromelain were studied. The thermal stability of bromelain was enhanced after complexing with tea polyphenols. By complexing, the activity half-life of bromelain at 60°C was lengthened from 60 to 105

H. H Liang; H. H Huang; K. C Kwok

1999-01-01

104

Effective magnetization of the dust particles in a complex plasma  

NASA Astrophysics Data System (ADS)

The large mass and size of the dust particles in a complex plasma has several advantages, including low characteristic frequencies on the order of a few Hz and the ability to record their motion with video cameras. However, these properties pose major difficulties for achieving strong magnetization. While the light electrons and ions can be magnetized by (superconducting) magnets, magnetizing the heavy dust component is extremely challenging. Instead of further increasing the magnetic field strengths or decreasing the particle size, we use the analogy between the Lorentz force and the Coriolis force experienced by particles in a rotating reference frame to create ``effective magnetic fields'' which is a well-established technique in the field of trapped quantum gases [1]. To induce rotation in a complex plasma, we take advantage of the neutral drag force, which allows to transmit the motion of a rotating neutral gas to the dust particles [2]. The equations of motion in the rotating frame agree with those in a stationary gas except for the additional centrifugal and Coriolis forces [3]. Due to the slow rotation frequencies (˜ Hz) and contrary to the situation in a strong magnetic field, only the properties of the heavy dust particles are notably affected. Experiments with a rotating electrode realize the desired velocity profile for the neutral gas and allow us to verify the efficiency of the concept [3].[4pt] This work was performed in collaboration with J. Carstensen, M. Bonitz, H. L"owen, F. Greiner, and A. Piel.[4pt] [1] A. L. Fetter, Rev. Mod. Phys. 81, 647 (2009)[0pt] [2] J. Carstensen, F. Greiner, L.-J. Hou, H. Maurer, and A. Piel, Phys. Plasmas 16, 013702 (2009)[0pt] [3] H. K"ahlert, J. Carstensen, M. Bonitz, H. L"owen, F. Greiner, and A. Piel, submitted for publication, arXiv:1206.5073

Kählert, Hanno

2012-10-01

105

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

106

[Preliminary pharmacological study on a "magnetic" drug complex].  

PubMed

Standard therapy requires high amounts of drugs, with subsequent risks of harmful effects on normal tissues. A treatment method that possible can avoid these risks is based on magnetic carriers (the method is designated also as magnetic carrier technique). The method consists in the selective attachment on a micro particle (permanent or reversible bonds), with strong magnetic moment, of an entity with no intrinsic magnetic properties (cells, microorganisms, antibody, antigens or chemicals), followed by external magnetic field targeting of the complexes ("active targeting"). The aims of this study were (1) to evaluate the acute toxicity of two original ferro-fluid (ammonium oleate and sodium oleate-based ferro-fluid) and (2) to assess the diclofenac (non-steroidal antiinflammatory drug, NSAIDS)--sodium oleate-based ferro-fluid efficiency in an acute inflammation model. We founded ammonium oleate-based ferro-fluid to have a strong dose-dependent toxicity, possible trough in vivo ammonium ions release; sodium oleate based-ferro-fluid seems to have a less toxicity. Diclofenac, diclofenac-ferro-fluid complex and ferro-fluid alone, each blocks the 6 hours inflammatory peak and the first two block also the 72 hours inflammatory peak. We conclude that the diclofenac-ferro-fluid complex is probably concentrated in the area of external magnetic field application, leading to a stronger effect of the antiinflammatory drug. Taking in consider our results we cannot exclude a possible summation of the individual effects of diclofenac, ferro-fluid, and external magnetic field on the inflammatory phenomenon. PMID:16607818

Brede?ean, O; C?m?ru?, Stef?nica; Ciochin?, A D; C?m?ru?, Maria; Iacob, G

2005-01-01

107

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

John Eichinger

2009-05-15

108

Improving magnetic properties of ultrasmall magnetic nanoparticles by biocompatible coatings  

NASA Astrophysics Data System (ADS)

This paper deals with the effect of a biocompatible surface coating layer on the magnetic properties of ultrasmall iron oxide nanoparticles. Particles were synthesized by laser pyrolysis and fully oxidized to maghemite by acid treatment. The surface of the magnetic nanoparticles was systematically coated with either phosphonate (phosphonoacetic acid or pamidronic acid) or carboxylate-based (carboxymethyl dextran) molecules and the binding to the nanoparticle surface was analyzed. Magnetic properties at low temperature show a decrease in coercivity and an increase in magnetization after the coating process. Hysteresis loop displacement after field cooling is significantly reduced by the coating, in particular, for particles coated with pamidronic acid, which show a 10% reduction of the displacement of the loop. We conclude that the chemical coordination of carboxylates and phosphonates reduces the surface disorder and enhances the magnetic properties of ultrasmall maghemite nanoparticles.

Costo, R.; Morales, M. P.; Veintemillas-Verdaguer, S.

2015-02-01

109

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

SciTech Connect

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

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

2013-08-15

110

Complex magnetically insulated transmission line oscillator  

SciTech Connect

A magnetically insulated transmission line oscillator (MILO) is a crossed-field device designed specifically to generate microwave power at the gigawatt level, which is a major hotspot in the field of high-power microwaves (HPM) research at present. It is one of the major thrust for MILO development to improve the power conversion efficiency. In order to improve the power conversion efficiency of MILO, a complex MILO is presented and investigated theoretically and numerically, which comprises the MILO-1 and MILO-2. The MILO-2 is used as the load of the MILO-1. The theoretical analyses show that the maximum power conversion efficiency of the complex MILO has an increase of about 50% over the conventional load-limited MILO. The complex MILO is optimized with KARAT code (V. P. Tarakanov, Berkeley Research Associates, Inc., 1992), and the simulation results agree with the theoretical results.

Fan Yuwei; Zhong Huihuang; Shu Ting; Li Zhiqiang [College of Optoelectric Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

2008-08-15

111

Transition metal complexes and radical anion salts of 1,10-phenanthroline derivatives annulated with a 1,2,5-tiadiazole and 1,2,5-tiadiazole 1,1-dioxide moiety: multidimensional crystal structures and various magnetic properties.  

PubMed

Advances in the molecular variety and the elucidation of the physical properties of 1,10-phenanthroline annulated with 1,2,5-thiadiazole and 1,2,5-thiadiazole 1,1-dioxide moieties have been achieved, and are described herein. A 1,2,5-thiadiazole compound, [1,2,5]thiadiazolo[3,4-f][1,10]phenanthroline (tdap), was used as a ligand to create multidimensional network structures based on S•••S and S•••N intermolecular interactions. A 1,2,5-thiadiazole 1,1-dioxide compound, [1,2,5] thiadiazolo[3,4-f][1,10]phenanthroline, 1,1-dioxide (tdapO2), was designed to create a stable radical anion, as well as good network structures. Single crystal X-ray structure analyses revealed that transition metal complexes of tdap, and radical anion salts of tdapO2 formed multidimensional network structures, as expected. Two kinds of tdap iron complexes, namely [Fe(tdap)2(NCS)2] and [Fe(tdap)2(NCS)2]•MeCN exhibited spin crossover transitions, and their transition temperatures showed a difference of 150 K, despite their similar molecular structures. Magnetic measurements for the tdapO2 radical anion salts revealed that the magnetic coupling constants between neighboring radical species vary from strongly antiferromagnetic (J=-320 K) to ferromagnetic (J=24 K), reflecting the differences in their ? overlap motifs. PMID:24402196

Shuku, Yoshiaki; Awaga, Kunio

2014-01-01

112

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

113

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

114

Electrical properties of chain microstructure magnetic emulsions in magnetic field  

E-print Network

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

Arthur Zakinyan; Yuri Dikansky; Marita Bedzhanyan

2014-02-05

115

Magnetic properties of anisotropic Sr-La-system ferrite magnets  

SciTech Connect

This paper presents an experiment carried out to investigate the effect of La{sub 2}O{sub 3} addition to the magnetic and physical properties of strontium ferrite magnets. It was found that the La{sub 2}O{sub 3} addition to SrO {center dot} 6Fe{sub 2}O{sub 3} (stoichiometric composition) was very useful in stabilizing the magnetoplumbite structure and that these Sr-La-system ferrites had excellent properties as a permanenent magnet. Compositions were chosen according to the formula ((SrO){sub 1/n+1}(Fe{sub 2}O{sub 3}){sub n/n+1}){sub 100{minus}x}(La{sub 2}O{sub 3}){sub x}, where n was varied between 5.0 and 6.5, and x between 0 and 5.0. The optimum conditions for making magnets and some properties of typical specimens are discussed.

Yamamoto, H.; Nagakura, M. (School of Science and Technology, Meiji Univ., 1-1-1 Higashi-mita, Tama-ku, Kawasaki 214 (JP)); Terada, H. (College of Engineering, Chubu Univ., 1200 Matsumoto-cho, Kasugai 487 (JP))

1990-05-01

116

Tetranuclear hetero-metal [Co(II)2Ln(III)2] (Ln = Gd, Tb, Dy, Ho, La) complexes involving carboxylato bridges in a rare ?4-?(2):?(2) mode: synthesis, crystal structures, and magnetic properties.  

PubMed

A new family of 3d-4f heterometal 2 × 2 complexes [Co(II)2(L)2(PhCOO)2Ln(III)2(hfac)4] (1-5) (Ln = Gd (compound 1), Tb (compound 2), Dy (compound 3), Ho (compound 4), and La (compound 5)) have been synthesized in moderate yields (48-63%) following a single-pot protocol using stoichiometric amounts (1:1 mol ratio) of [Co(II)(H2L)(PhCOO)2] (H2L = N,N'-dimethyl-N,N'-bis(2-hydroxy-3,5-dimethylbenzyl)ethylenediamine) as a metalloligand and [Ln(III)(hfac)3(H2O)2] (Hhfac = hexafluoroacetylacetone) as a lanthanide precursor compound. Also reported with this series is the Zn-Dy analog [Zn(II)2(L)2(PhCOO)2Dy(III)2(hfac)4] 6 to help us in understanding the magnetic properties of these compounds. The compounds 1-6 are isostructural. Both hexafluoroacetylacetonate and benzoate play crucial roles in these structures as coligands in generating a tetranuclear core of high thermodynamic stability through a self-assembly process. The metal centers are arranged alternately at the four corners of this rhombic core, and the carboxylato oxygen atoms of each benzoate moiety bind all of the four metal centers of this core in a rare ?4-?(2):?(2) bridging mode as confirmed by X-ray crystallography. The magnetic susceptibility and magnetization data confirm a paramagnetic behavior, and no remnant magnetization exists in any of these compounds at vanishing magnetic field. The metal centers are coupled in an antiferromagnetic manner in these compounds. The [Co(II)2Dy(III)2] compound exhibits a slow magnetic relaxation below 6 K, as proven by the AC susceptibility measurements; the activation energy reads U/kB = 8.8 K (?0 = 2.0 × 10(-7) s) at BDC = 0, and U/kB = 7.8 K (?0 = 3.9 × 10(-7) s) at BDC = 0.1 T. The [Zn(II)2Dy(III)2] compound also behaves as a single-molecule magnet with U/kB = 47.9 K and ?0 = 2.75 × 10(-7) s. PMID:24437653

Abtab, Sk Md Towsif; Majee, Mithun Chandra; Maity, Manoranjan; Titiš, Ján; Bo?a, Roman; Chaudhury, Muktimoy

2014-02-01

117

Magnetic Nanotubes: Synthesis, Properties, and Applications  

Microsoft Academic Search

This article presents a comprehensive review of recent progress of research dedicated to magnetic nanotubes (MNTs). The review mainly covers the recent achievements in the syntheses, properties, and applications of MNTs. After introducing the significance of MNTs and the magnetic characteristics of elements in the periodic table, the article starts with a brief overview of the existing fabrication pathways for

Yixing Ye; Baoyou Geng

2012-01-01

118

Selected Magnetic Properties of the Atomic Nuclei  

Microsoft Academic Search

Three different but closely related aspects of the magnetic properties of the atomic nuclei: (a) the quenching and fragmentation of transitions to stretched states, (b) the scissor mode magnetic dipole excitation and higher multipole excitations, and (c) the double beta decay matrix element, are studied in the context of the nuclear structure calculations. A rotational model is devised for both

Huan Liu

1987-01-01

119

Magnetic properties of polymer bonded nanocrystalline powder  

Microsoft Academic Search

Purpose: The aim of this paper was to develop a dielectromagnetic based on nanocrystalline Fe73.5Cu1Nb3Si13.5B9 powder bonded with organo-silicon polymer and to investigate the powder particle size and content of polymer response of the magnetic properties. Design\\/methodology\\/approach: The dynamic magnetic properties at the frequency range from 50 Hz up to 100 kHz of nanocrystalline iron based powder cores were measured

P. Gramatyka; R. Nowosielski; P. Sakiewicz

120

Static magnetic properties of Maghemite nanoparticles  

NASA Astrophysics Data System (ADS)

We report the static magnetic properties of Maghemite (?-Fe2O3) nanoparticles with an average crystallite size of 14 ± 1.8 nm synthesized via a co-precipitation method. The zero-field-cooled (ZFC) and the field-cooled (FC) magnetization measurements were performed using a physical properties measurements system (PPMS) at temperatures from 5 K to 300 K. The ZFC/FC measurements showed a typical superparamagnetic behavior with a narrow size distribution.

Zulfiqar; Rahman, Muneeb Ur; Usman, M.; Hasanain, Syed Khurshid; Zia-ur-Rahman; Ullah, Amir; Kim, Ill Won

2014-12-01

121

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

122

Versatility in the binding of 2-pyrazinecarboxylate with iron : Synthesis, structure and magnetic properties of iron(II) and iron(III) complexes  

Microsoft Academic Search

The synthesis and characterization of two new iron(II) complexes, [Fe(pca)(2)(py)(2)]center dot py (1) and {[Fe(pca)(2)(H2O))] center dot H2O}(n) (2) and one new iron(m) complex, Na-2{[Fe(pca)(3))](2)O}center dot 2H(2)O center dot 2CH(3)CN (3) (pca(-) stands for 2-pyrazinecarboxylate), are reported. Complex 1 is obtained from the reaction of iron powder with 2-pyrazinecarboxylic acid. The reaction of Fe(ClO4)(3)center dot 10H(2)O with Hpca in the

Stefania Tanase; Patricia Marqués Gallego; Elisabeth Bouwman; Gary J. Long; Leila Rebbouh; Fernande Grandjean; René de Gelder; Ilpo Mutikainen; Urho Turpeinen; Jan Reedijk

2006-01-01

123

Complex of heavy magnetic ions and luminescent silicon nanoparticles  

NASA Astrophysics Data System (ADS)

We study the optical properties of luminescent silicon nanoparticles in the presence of magnetic ions of iron or erbium under wet conditions and electric biasing. Upon the introduction of the ions under zero biasing, the brightness is enhanced with some spectral change. Under biasing including breakdown field conditions, the enhancement remains stable and is maintained after recovery of the particles into nanosolid films using electric spray. The ion-nanoparticle interaction is analyzed using first principle atomistic calculations employing unrestricted Hartree-Fock density functional theory. The calculations yield configurations, which show strong binding and stability. The complexes promise diverse applications in magnetic/optical imaging, spatially programmable deposition, spin-based memories and transistors, infrared communications, filtration, as well as interplanetary and interstellar observation and modeling.

Hoang, T.; Stupca, M.; Mantey, K.; Maximenko, Y.; Elhalawany, N.; Carr, C.; Yu, H.; Nayfeh, M. H.; Morgan, H.

2013-10-01

124

Self-assembly of cuII and niII [2 x 2] grid complexes and a binuclear CuII complex with a new semiflexible substituted pyrazine ligand: multiple anion encapsulation and magnetic properties.  

PubMed

With the new substituted pyrazine ligand pyrazine-2,3-dicarboxylic acid bis[(pyridin-2-ylmethyl)amide], H(2)L, a binuclear complex [Cu(2)(LH)(Cl(3))(H(2)O)].H(2)O (1) and two [2 x 2]G grid complexes, [[Cu(4)(LH)(4)](ClO(4))(4)].5CH(3)OH.4H(2)O (2) and [[Ni(4)(LH)(4)]Cl(4)].5CH(3)CN.13H(2)O (3), have been synthesized and characterized spectroscopically and crystallographically. The ligand H(2)L crystallized in the triclinic space group P1, with a = 4.9882(7) A, b = 12.079(2) A, c = 14.454(2) A, alpha = 107.08(2) degrees, beta = 98.61(2) degrees, gamma = 97.54(2) degrees, V = 808.8(2) A(3), Z = 2, R1 = 0.0747, and R(w) = 0.1829 for 1319 observed reflections [I > 2 sigma(I)]. The molecule is L-shaped with a strong intramolecular bifurcated hydrogen bond in half of the molecule. In the crystal the molecules are linked by an intermolecular hydrogen bond to form a 1D polymer. The binuclear complex [Cu(2)(LH)(Cl(3))(H(2)O)].H(2)O (1) crystallized in the monoclinic space group P2(1)/a, with a = 8.6859(7) A, b = 28.060(2) A, c = 9.5334(9) A, beta = 107.89(1) degrees, V = 2211.2(3) A(3), Z = 4, R1 = 0.039, and R(w) = 0.097 for 1408 observed reflections [I > 2 sigma(I)]. There are two independent copper atoms both having square pyramidal geometry. Both coordinate to a pyrazine, a pyridine, and an amide N atom. Two chlorines complete the coordination sphere of one of the copper atoms, while one chlorine atom and a water molecule complete the coordination sphere of the other. The copper(II) [2 x 2] grid complex [[Cu(4)(LH)(4)](ClO(4))(4)].5CH(3)OH.4H(2)O (2) crystallized in the triclinic space group P1, with a = 17.1515(14) A, b = 17.7507(13) A, c = 19.3333(15) A, alpha = 67.34(1) degrees, beta = 69.79(1) degrees, gamma = 71.50(1) degrees, V = 4980.3(7) A(3), Z = 2, R1 = 0.083, and R(w) = 0.207 for 5532 observed reflections [I > 2 sigma(I)]. The four Cu(II) atoms are octahedrally coordinated by two pyrazine, two pyridine, and two amide N atoms and occupy the corners of a [2 x 2] grid with edge lengths, Cu...Cu, varying from 7.01 to 7.39 A. The nickel(II) [2 x 2] grid complex [[Ni(4)(LH)(4)]Cl(4)].5CH(3)CN.13H(2)O (3) crystallized in the monoclinic space group C2/c, with a = 16.3388(10) A, b = 29.754(2) A, c = 20.857(1) A, beta = 101.845(1) degrees, V = 9923.6(12) A(3), Z = 4, R1 = 0.050, and wR2 = 0.101 for 3391 observed reflections [I > 2 sigma(I)]. Here the complex possesses C(2) symmetry and again each metal atom is octahedrally coordinated to two pyrazine, two pyridine, and two amide N atoms. They occupy the corners of a [2 x 2] grid with an average edge length, Ni.Ni, of 6.97 A. Of the four anions (ClO(4)(-)'s in 2 and Cl(-)'s in 3) required to equilibrate the charges in the grid complexes, two are encapsulated, one above and one below the plane of the four metal atoms. The remaining two anions are located between the "wings" of the ligands. Magnetic susceptibility measurements indicate that the binuclear complex 1 is antiferromagnetic, with a J value of -15.07 cm(-1). This is larger than the J values found for the Cu(II) (2) and Ni(II) (3) grid complexes, which were -5.87 and -2.64 cm(-1), respectively. DFT calculations have been carried out to explain the difference in the J values found for complexes 1 and 2. PMID:14753824

Cati, Dilovan S; Ribas, Joan; Ribas-Ariño, Jordi; Stoeckli-Evans, Helen

2004-02-01

125

Magnetic properties of metallic ferromagnetic nanoparticle composites  

NASA Astrophysics Data System (ADS)

Magnetic properties of nanoparticle composites, consisting of aligned ferromagnetic nanoparticles embedded in a nonmagnetic matrix, have been determined using a model based on phenomenological approaches. Input materials parameters for this model include the saturation magnetization (Ms), the crystal anisotropy field (Hk), a damping parameter (?) that describes the magnetic losses in the particles, and the conductivity (?) of the particles; all particles are assumed to have identical properties. Control of the physical characteristics of the composite system—such as the particle size, shape, volume fraction, and orientation—is necessary in order to achieve optimal magnetic properties (e.g., the magnetic permeability) at GHz frequencies. The degree to which the physical attributes need to be controlled has been determined by analysis of the ferromagnetic resonance (FMR) and eddy current losses at varying particle volume fractions. Composites with approximately spherical particles with radii smaller than 100 nm (for the materials parameters chosen here), packed to achieve a thin film geometry (with the easy magnetization axes of all particles aligned parallel to each other and to the surface of the thin film) are expected to have low eddy current losses, and optimal magnetic permeability and FMR behavior.

Ramprasad, R.; Zurcher, P.; Petras, M.; Miller, M.; Renaud, P.

2004-07-01

126

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

127

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

128

MICRODYNAMICS OF MAGNETIC PARTICLES DISPERSED IN COMPLEX MEDIA  

E-print Network

of a magnetic field is the basic phenomenon which underlies all the physics of magnetorheological (MR) fluids in the rheological properties of a magnetorheological (MR) suspension upon application of a magnetic field [1

Paris-Sud XI, Université de

129

Magnetic Properties of Hydroxy Ni-Mica Intercalation  

NASA Astrophysics Data System (ADS)

The magnetic properties of hydroxy Ni-mica intercalation complexes in which Ni forms two-dimensional lattices between mica layers have been investigated. The concentration of Ni was varied up to 21 wt%. The magnetic moment per Ni was evaluated from the Curie constants to be between 2 and 3 ?B (dependent on the Ni content). Paramagnetic Curie temperatures obtained by the temperature dependence of the initial susceptibility are about 7-13 K for all the samples, while an apparent ferromagnetism is defined only for a sample with 2.6 wt% Ni by Arrott plots. These magnetic properties were explained by the formation of a Ni triad in a two-dimensional lattice because of the chemical stability of [Ni3(OH)5H2O]+ as an intercalant, and by a coaguration of triads with increasing Ni content.

Takahashi, Minoru; Sato, Minoru; Ishio, Shunji; Ohtsuka, Kunio; Suda, Mitsuru; Ono, Mikiya

1986-09-01

130

Magnetic properties within sunspot clusters  

NASA Astrophysics Data System (ADS)

By studying coronal limb synoptic maps we found that the long-lived large scale coronal streamers are sustained by spatially related non-contemporaneous sunspots The individual sunspot group normally has life time of one solar rotation But different groups of sunspots emerge from the same location on the sun give rise to the streamers which can last as long as 10 solar rotations This finding accounts for earlier studies on active longitudes sunspot nests or active zones The implication of these studies is that there exists a subsurface source of activity which lasts sometimes for years Continuous line-of-sight magnetograms are obtained by MDI SOHO since 1996 These data provide opportunities to study magnetic structures of sunspots as function of time We will present 5 sunspot clusters selected by coronal streamers over years 1996 to 2002 Each sunspot group within the 5 clusters are studied with structural parameters including distances between virtual positive and negative polarities areas magnetic flux magnetic tilt angles using MDI data These parameters have been studied recently with different types of sunspots

Li, J.

131

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

E-print Network

) Succinic acid (0.118 g, 1 mmol) was dissolved in a solution of NaOH (0.008 g, 2 mmol) in H2O (4 m(II) complexes bridged by succinate q Siau Gek Ang a,*, Bai Wang Sun a , Song Gao b a Department of Chemistry State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry, Peking

Gao, Song

132

Stability Properties of Magnetic Tower Jets  

E-print Network

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

Masanori Nakamura; Hui Li; Shengtai Li

2006-08-31

133

Metal ion complexes of. cap alpha. -amido acids. 2. Structure and magnetic properties of iron(II) hippurate, a linear-chain insulator  

Microsoft Academic Search

Iron(II) hippurate, Fe(hipp)â(HâO)â 2HâO, has been prepared and characterized. Single-crystal x-ray diffraction revealed the compound to be essentially isostructural with the previously reported cobalt(II) and nickel(II) hippurates, crystallizing as a linear chain with canted metal octahedra bridged by the oxygen atom of a water molecule. The space group is C2\\/c with four formula weights per unit cell. The structural properties

Maurice M. Morelock; Mary L. Good; Louis M. Trefonas; Richard. Majeste; David G. Karraker

1982-01-01

134

Exchange coupling across the cyanide bridge: structural and DFT interpretation of the magnetic properties of a binuclear chromium(III) complex.  

PubMed

The reaction of [Cr(CN)6]3- with a mixture of trans-[Cr(cyclam)(OH)2]Cl, [Cr(cyclam)(OH)Cl]Cl and [Cr(cyclam)Cl2]Cl affords the cyanide bridged dimer, trans-[HO-Cr(cyclam)-NC-Cr(CN)5]-. The tetraphenylphosphonium salt of the anion crystallizes in space group P2(1)/n and shows a bent arrangement of the Cr1-CN-Cr2 unit with the Cr1-CN bond angle at 166.9 degrees and CN-Cr2 at 160.32 degrees . The Cr2-O bond, trans to the hexacyanide fragment, is very short at 1.902 A. Two dimers are held together by two hydrogen bonds connecting the Cr2-OH group of each dimer with one of the NH groups of the cyclam ligand of an adjacent molecule, leading to an almost linear configuration. These dimers of dimers get packed parallel to each other, generating layers separated by the tetraphenylphosphonium cations. Four of the cyanide groups of the anion are engaged in H-bonds with the four water molecules present in the structure or with a NH group of the macrocycle of an adjacent molecule. From magnetic susceptibility measurements, the dimer was found to exhibit antiferromagnetic interaction between the Cr(III) centers with J=-16 cm(-1)(H=-2JS(A)S(B)). Structural and magnetic parameters have been calculated by density functional theoretical methods at the B3LYP level. The exchange coupling constant, J, calculated for the dimer at the X-ray geometry is -23.2 cm(-1) which is in excellent agreement with the experimental value. PMID:16462955

Alborés, Pablo; Slep, Leonardo D; Weyhermüller, Thomas; Rentschler, Eva; Baraldo, Luis M

2006-02-21

135

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

136

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. PMID:24910569

2014-01-01

137

Formation of coordination polymers or discrete adducts via reactions of gadolinium(III)-copper(II) 15-metallacrown-5 complexes with polycarboxylates: synthesis, structures and magnetic properties.  

PubMed

Reactions of the copper(II)-gadolinium(III) 15-metallacrown-5 complex [GdCu5(Glyha)5(NO3)2(H2O)6](NO3) (Glyha(2-) = dianion of glycinehydroxamic acid) with different di/tricarboxylates (1,3-phthalate, 1,4-phthalate, biphenyl-4,4'-dicarboxylate, citrate) resulted in formation of different types of products: {[(GdCu5(Glyha)5(H2O)2)(GdCu5(Glyha)5(H2O)3)(1,3-bdc)3]·16H2O}n (1), {[(GdCu5(Glyha)5(H2O)3)2(1,4-bdc)2](1,4-bdc)·8H2O}n (2), {[(GdCu5(Glyha)5(H2O)4)2(1,4-bdc)3]·8H2O}n (3), [GdCu5(Glyha)5(Citr)(H2O)4]·7H2O (4), {[GdCu5(Glyha)5(H2O)5](?2-CO3)[Cu(Fgg)]}·7H2O (5) and [Cu(Gly)2(H2O)]n (6) (where bdc(2-) is the corresponding phthalate (benzenedicarboxylate), Citr(3-) is citrate, Fgg(3-) is the trianion of [(N-formylaminoacetyl)amino]acetic acid and Gly(-) is glycinate). Complexes 1-5 contain the [GdCu5(Glyha)5](3+) cation. Complexes 2 and 3 possess the same composition but differ by the mode of p-phthalate coordination to the [GdCu5(Glyha)5](3+) unit. In compounds 1-3, metallacrown cations are linked by the corresponding phthalates in 1D, 1D and 2D polymers, respectively, whereas 4 and 5 are discrete molecules. Compound 5 is the product of a multistep reaction, which finally involves atmospheric CO2 capture. Hydrolysis of hydroxamate in this reaction is confirmed by isolation of a mononuclear copper glycine complex 6. The ?MT vs T data for 1 were fitted using a model based on the Hamiltonian ? (GdCu5) = -2J1(S1 × SGd + S2 × SGd + S3 × SGd + S4 × SGd + S5 × SGd) - 2J2(S1 × S2 + S2 × S3 + S3 × S4 + S4 × S1 + S5 × S1. The best fit corresponded to J1 = +0.60(2) cm(-1), J2 = -61.0(5) cm(-1) and zJ' = -0.035(4) cm(-1). Complex 1 is the first example of a 15-metallacrown-5 system, for which numerical values of exchange parameters have been reported. The isotherm for methanol absorption by compound 1 at 293 K was typical for microporous sorbents, whereas ethanol sorption was negligibly small. PMID:24422476

Pavlishchuk, Anna V; Kolotilov, Sergey V; Zeller, Matthias; Thompson, Laurence K; Addison, Anthony W

2014-02-01

138

Magnetic properties and energy-mapping analysis.  

PubMed

The magnetic energy levels of a given magnetic solid are closely packed in energy because the interactions between magnetic ions are weak. Thus, in describing its magnetic properties, one needs to generate its magnetic energy spectrum by employing an appropriate spin Hamiltonian. In this review article we discuss how to determine and specify a necessary spin Hamiltonian in terms of first principles electronic structure calculations on the basis of energy-mapping analysis and briefly survey important concepts and phenomena that one encounters in reading the current literature on magnetic solids. Our discussion is given on a qualitative level from the perspective of magnetic energy levels and electronic structures. The spin Hamiltonian appropriate for a magnetic system should be based on its spin lattice, i.e., the repeat pattern of its strong magnetic bonds (strong spin exchange paths), which requires one to evaluate its Heisenberg spin exchanges on the basis of energy-mapping analysis. Other weaker energy terms such as Dzyaloshinskii-Moriya (DM) spin exchange and magnetocrystalline anisotropy energies, which a spin Hamiltonian must include in certain cases, can also be evaluated by performing energy-mapping analysis. We show that the spin orientation of a transition-metal magnetic ion can be easily explained by considering its split d-block levels as unperturbed states with the spin-orbit coupling (SOC) as perturbation, that the DM exchange between adjacent spin sites can become comparable in strength to the Heisenberg spin exchange when the two spin sites are not chemically equivalent, and that the DM interaction between rare-earth and transition-metal cations is governed largely by the magnetic orbitals of the rare-earth cation. PMID:23128376

Xiang, Hongjun; Lee, Changhoon; Koo, Hyun-Joo; Gong, Xingao; Whangbo, Myung-Hwan

2013-01-28

139

Refocusing properties of periodic magnetic fields  

NASA Technical Reports Server (NTRS)

The use of depressed collectors for the efficient collection of spent beams from linear-beam microwave tubes depends on a refocusing procedure in which the space charge forces and transverse velocity components are reduced. The refocusing properties are evaluated of permanent magnet configurations whose axial fields are approximated by constant plateaus or linearly varying fields. The results provide design criteria and show that the refocusing properties can be determined from the plateau fields alone.

Stankiewicz, N.

1976-01-01

140

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

141

Maria Goeppert-Mayer Award Talk: Novel Magnetism and Transport in Complex Oxide Thin Films, Multilayers and Nanostructures  

Microsoft Academic Search

In epitaxial complex oxide systems, epitaxial strain, cation substitution and nanofabrication are just some ways in which their magnetic, electronic and optical properties may be tuned. In addition, their surfaces and interfaces provide a rich playground for the exploration of novel magnetic properties not found in the bulk constituents and the development of functional interfaces to be incorporated into technological

Yuri Suzuki

2005-01-01

142

Magnetic core shell nanostructures with plasmonic properties  

NASA Astrophysics Data System (ADS)

The gold nanoparticle coated cobalt-silica core-shell nanospheres have been synthesized via a multi-step, solution based chemical approach. While the plasmonic characteristics of gold nanoparticles (AuNPs) are retained in core shell configuration, the magnetic properties of core shell system change significantly after AuNP coating. It is found that the coercivity of magnetic core-shell significantly reduces after AuNP coating and system could not attain magnetic saturation at 300 K (even at large field of 5 T). At low temperature (10 K), AuNP coated cobalt-silica coreshell nanospheres exhibit reduced magnetization (Ms=4.3 emu/g) compared to bare cobalt-silica core-shell system (Ms=6 emu/g).

Tyagi, Himanshu; Aslam, M.

2013-02-01

143

Magnetic Properties of Ubiquitous yet Underrated Antiferromagnetic Nanoparticles  

NASA Astrophysics Data System (ADS)

Ferrihydrite, lepidocrocite and goethite are antiferromagnetic, weakly "ferromagnetic" iron oxyhydroxides that are commonly found in diverse environments, including ground waters and streams, sediments, soils, or acid mine drainage. One of them, ferrihydrite, constitutes the mineral core of ferritin, a vital iron storage protein. Iron oxyhydroxides take part in multiple biological and abiological processes, and can evolve, under changing environmental or geological conditions, to more magnetic phases such as hematite, maghemite, or magnetite. Therefore, they represent key minerals with regard to paleoclimate, paleoenvironmental, and paleomagnetic studies. We will present low temperature magnetic properties acquired on fully characterized synthetic iron oxyhydroxides. The complex nature of the magnetism of these minerals is revealed by comparing magnetic data with other types of characterizations such as high-resolution transmission electron microscopy or synchrotron X-ray magnetic circular dichroism (XMCD), or when the early-stages of solid-state alteration (under oxidizing or reducing atmosphere) are studied. In particular, we will present resent results about the structure of 6-line ferrihydrite, about the possible presence of ferri-magnetic nano-clusters in lepidocrocite, and about uncompensated magnetic moments in goethite nanoparticles.

Guyodo, Y. J.; Till, J. L.; Lagroix, F.; Bonville, P.; Penn, R.; Sainctavit, P.; Ona-Nguema, G.; Morin, G.

2013-05-01

144

Rock-magnetic Records of Arctic Lake Sediments Reveal Complex Links Between Lakes and Environmental Change  

NASA Astrophysics Data System (ADS)

As part of a multi-parameter study of subarctic watersheds we analyzed the rock-magnetic properties of six lake sediment cores from northern Manitoba, Canada. These cores are all located within 75 km of Nejanilini Lake (59.7°N, -97.8°W) and straddle the present northern tree line. The studied sediment cores are between 2 and 3.5 m in length and they record environmental changes over the past 7500 - 8000 years. To characterize the magnetic properties of the cores we measured magnetic susceptibility (?), anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM) for all samples, and magnetic coercivity distributions for a selected subset of samples. Basal layers are characterized by strongly magnetic, coarse grained sediments whose magnetic properties are dominated by the surrounding till and outwash. More recent organic rich sediments are weakly magnetized and characterized by varying abundances of magnetotactic bacteria, which supply an abundance of small single-domain particles. In some sites, changes in magnetic parameters correlate to variations in non-magnetic parameters, such as macroscopic charcoal concentrations, pollen percentages or geochemical parameters (biSi, C:N ratios, pollen, bulk grain-size, Fe:Ti ratios). However, the observed changes are site-dependent underscoring the complex nature of lacustrine sedimentary records.

Geiss, C. E.; Camill, P.; Umbanhowar, C. E.; Edlund, M.

2011-12-01

145

Magnetic properties of heterotrophic bacteria (abstract)  

NASA Astrophysics Data System (ADS)

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

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

1994-05-01

146

Magnetic property variations in nickel caused by non-magnetic inclusions  

Microsoft Academic Search

A study of the effect of non-magnetic particles on the magnetic properties of nickel is reported. The presence of inclusions is known to affect the structure sensitive magnetic properties of materials. In this work, two kinds of inclusions, namely, alumina particles and voids were studied and their effects on the magnetic properties were investigated. Powder metallurgy techniques were used to

A. Ramesh; M. R. Govindaraju; D. C. Jiles; S. B. Biner

1996-01-01

147

Magnetic properties of pelagic marine carbonates  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

148

Two new tetranuclear complexes of the macrocyclic oxamide [MCu 3 ] (M = Cd, Mn, macrocyclic oxamide = 1,4,8,11-tetraazacyclotradecanne-2,3-dione): syntheses, spectra and magnetic properties  

Microsoft Academic Search

Two new tetranuclear complexes of macrocyclic oxamide [Cd(CuL)3](NO3)2·2.5H2O 1, [Mn(CuL)3(OH)2](ClO4)2·Mn(H2O)6·4.5H2O 2 (L = 1,4,8,11-tatraazacyclotradecanne-2,3-dione) have been synthesized, structurally characterized and preliminary investigated\\u000a by magnetic studies. The structures of the title complexes consist of a tetranuclear units MCu3 (M = Cd, Mn), the packing diagram shows two-dimensional and three-dimensional system through intermolecular weak interactions.\\u000a The temperature-dependent magnetic susceptibilities of complex 2 were analyzed by an

Yan Ouyang; Wei Zhang; Yue Ma; Na Xu; Dai-Zheng Liao; Kazuyoshi Yoshimura; Shi-Ping Yan

2007-01-01

149

Tuning electronic and magnetic properties of silicene with magnetic superhalogens.  

PubMed

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

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

2014-11-14

150

Magnetic Properties and Magnetization Dynamics in Amorphous Ferromagnetic Microwires  

NASA Astrophysics Data System (ADS)

The dynamics of the domain walls during magnetization reversal processes in amorphous ferromagnetic microwires is studied. The studies have been based in measurements made in bmagnetic bistable Fe77.5Si7.5B15 microwires . In bistable microwires the magnetization reversal process generally happens through the propagation of a single domain wall along the axial direction, i.e., a large Barkhausen jump. This reversal process is initiated at the wire ends, where a complex domain structure, characterized by the presence of closure domains, is found. Samples with diameters between 20 and 40 ?m, and lengths between 7 and 12 centimeters have been studied. The dynamics has been investigated through the analysis of the signal induced in search coils by the domain walls movement. The influence of externally applied magnetic fields in the dynamics of domain wall propagation has been investigated. Through these studies it was possible to distinguish the different magnetization processes taking place at the extremities and the central part of the microwires.

Sinnecker, João Paulo; Novak, Rafael

2006-03-01

151

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

152

Magnetic fabrics of the Morcles Nappe complex  

Microsoft Academic Search

Anisotropy of magnetic susceptibility (AMS) measured with high fields, at ambient and low temperatures (77 K), has been used to separate ferromagnetic (sensu lato), paramagnetic and diamagnetic sub-fabrics for deformed limestones located in a nappe structure from southwest Switzerland. The magnetic fabrics are dominantly controlled by paramagnetic and diamagnetic minerals, and ferromagnetic minerals contribute significantly only at two of the eight

Bjarne S. G. Almqvist; Ann M. Hirt; Volkmar Schmidt; Dorothee Dietrich

2009-01-01

153

Complexity and Diffusion of Magnetic Flux Surfaces in Anisotropic Turbulence  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

154

Switching nuclearity and Co(II) content through stoichiometry adjustment: {Co(II)6Co(III)3} and {Co(II)Co4(III)} mixed valent complexes and a study of their magnetic properties.  

PubMed

We are reporting two new mixed valent Co(ii)/Co(iii) polynuclear complexes, {Co(II)6Co(III)3} and {Co(II)Co(III)4}, bearing different amount of Co(ii) ions in their cores, through the employment of the multidentate triethanolamine (teaH3) ligand in different stoichiometric ratios. We present a complete picture of the magnetic behaviour of both complexes through a combined usage of the susceptibility, magnetization and X-band EPR data as well as broken-symmetry DFT calculations. Compound shows an atypical spin-only behaviour, probably due to the presence of four and five coordinated Co(ii) sites as well as highly distorted six coordinated Co(ii) ions, promoting a high degree of orbital contribution quenching. Through the usage of a simplified exchange coupling scheme and relying on DFT based magneto-structural correlation we have been able to explain the observed diamagnetic ground state. Concerning compound , DC magnetic data supported by X-band EPR measurements suggest the existence of anisotropy with a zero-field splitting parameter D, at least in the range of 2-10 cm(-1). In agreement with this description, a slow relaxation of magnetization is observed after applying a small external magnetic field, under AC measurements. Field and temperature dependence of the characteristic relaxation time establishes a thermal barrier for magnetization reversal of about 25 cm(-1), which is in good agreement with the energy splitting of the |±1/2? and |±3/2? doublets established from static magnetic measurements. PMID:25537966

Funes, Alejandro V; Carrella, Luca; Sorace, Lorenzo; Rentschler, Eva; Alborés, Pablo

2015-02-01

155

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

156

Magnetic and Electronic Properties of Rare-Earth - Metallic Glasses.  

NASA Astrophysics Data System (ADS)

Results of magnetic measurements are presented on the new metallic glass systems (R(,80)G(,20))(,100-x)Fe(,x) and (R(,80)Ga(,20))(,90)B(,10), where R is a rare-earth (i.e., La, Pr, Nd, Sm, Gd, Tb and Er) and G is Ga or Au for 0 (LESSTHEQ) x (LESSTHEQ) 30. High-field magnetization (to 80 kOe) and A.C. and D.C. susceptibility measurements were made from 1.4 K to 300 K. High-field magnetization data are analyzed by an Arrott plot technique and some Gd-based glasses show results consistent with the presence of the recently predicted infinite susceptibility phase of Aharony and Pytte. The magnetic hardness properties of most of these glasses (not containing S-state ions) are discussed in terms of the 'microdomain' model of Callen et al. In many glasses the magnetization reversal seems consistent with a coherent rotation mechanism as is suggested from the thermal variation of the coercivity. The glasses (R(,80)Ga(,20))(,70)Fe(,30) where R is Er and Tb are more complex and show behavior consistent with the presence of domain walls. Magnetic saturation was not obtained (at 80 kOe) on any glass containing an anisotropic rare -earth while glasses based on S-state rare-earths were fairly easily saturated. Giant intrinsic magnetic hardness is observed in the glasses (R(,80)G(,20))(,100-x)Fe(,x) where R is Nd or Pr and G is Ga or Au for 15 (LESSTHEQ) x (LESSTHEQ) 30. An unusual thermal variation of the coercive field is observed showing peaks at intermediate temperatures ((DBLTURN) 90 K). A phase separation into different amorphous stoichiometries is shown to exist by Fe('57) Mossbauer effect and other measurements. These results are consistent with a recent theory by Paul predicting that magnetic hardness can result from the presence of site-to-site variations in magnetic properties. Electrical resistivity measurements were made on the above glasses as well as the series (Pr(,80)Ga(,20))(,80)T(,20), where T = Cr, Mn, Co, Ni, Cu and Ga. These show negative temperature coefficients of resistivity at higher temperatures in most cases as well as structure in the resistivity below magnetic ordering temperatures. These results are shown to be consistent with some recent theories (for instance the extended Ziman theory) predicting negative slopes of the resistivity as well as to some theories predicting a magnetic contribution to the resistivity from coherent exchange scattering.

Cornelison, Steven G.

1982-03-01

157

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

158

The complex initial reluctivity, permeability and susceptibility spectra of magnetic materials  

NASA Astrophysics Data System (ADS)

The HF complex permeability spectrum of a magnetic material is deduced from the measured impedance spectrum, which is then normalized to a series permeability spectrum. However, this series permeability spectrum has previously been shown to correspond to a parallel magnetic circuit, which is not appropriate. Some of the implications of this truth are examined. This electric/magnetic duality has frustrated efforts to interpret the shape of the complex magnetic permeability spectra of materials, and has hindered the application of impedance spectroscopy to magnetic materials. In the presence of magnetic loss, the relationship between the relative magnetic permeability and the magnetic susceptibility is called into question. The use of reluctivity spectra for expressing magnetic material properties is advocated. The relative loss factor, tan?m/?i is shown to be an approximation for the imaginary part of the reluctivity. A single relaxation model for the initial reluctivity spectra of magnetic materials is presented, and its principles are applied to measurements of a high permeability ferrite. The results are presented as contour plots of the spectra as a function of temperature.

Hamilton, N. C.

2015-03-01

159

Magnetic properties of the High Himalayan leucogranites: Structural implications  

NASA Astrophysics Data System (ADS)

The magnetic properties of the High Himalayan leucogranites have been investigated on 527 specimens in three plutons, Everest-Makalu (6 sites) and Manaslu (40 sites) in Nepal, and Gangotri (43 sites) in India. Susceptibility varies between 2 and 100 x 10(exp -6) SI, with an anisotropy ratio up to 1.16. High field and low-temperature magnetic measurements together with comparisons with weight percent iron demonstrate that anisotropy of magnetic susceptibility is carried by paramagnetic biotite and tourmaline. The latter produces an inverse fabric, i.e. with the minimum axis parallel to mineral lineation. The magnetic fabric demonstrates complex patterns of stretching lineations during magmatic emplacement, and its usefulness in semi-quantitatively estimating petrofabric intensity is demonstrated for the biotite-bearing facies. Natural remanent magnetization was measurable at only two sites in Everest-Makalu, where there are well-defined reverse directions carries by titanomagnetite and pyrrhotite. Comparison of these preliminary results with predicted directions for stable India suggests northward tilting of about 10 deg and a small clockwise rotation of this massif.

Rochette, Pierre; Scaillet, Bruno; Guillot, Stephane; Le Fort, Patrick; Pecher, Arnaud

1994-09-01

160

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

161

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

162

Magnetic properties of Kurokami pumices from Mt. Sakurajima, Japan  

E-print Network

Magnetic properties of Kurokami pumices from Mt. Sakurajima, Japan Yongjae Yu aY *, David J. Dunlop-Ti titanomagnetite are carriers of natural remanent magnetization (NRM) in Kurokami andesitic pumices of Mt reserved. Keywords: chromite; titanomagnetite; pumice; Sakura-jima; magnetic properties 1. Introduction

Dunlop, David J.

163

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

164

Oriented inclusions of magnetite in clinopyroxene: Source of stable remanent magnetization in gabbros of the Messum Complex, Namibia  

Microsoft Academic Search

Crystallographically oriented and highly elongate magnetite inclusions in clinopyroxene are the dominant source of highly stable remanent magnetization in gabbros of the Early Cretaceous Messum Complex, Namibia. Rock magnetic properties determined for individual pyroxene crystals indicate a high proportion of single-domain magnetite, consistent with the observed sizes and shape anisotropy of the magnetite inclusions. As in previous studies of similar

Paul R. Renne; Gary R. Scott; Jonathan M. G. Glen; Joshua M. Feinberg

2002-01-01

165

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

166

Magnetic fabrics of the Morcles Nappe complex  

NASA Astrophysics Data System (ADS)

Anisotropy of magnetic susceptibility (AMS) measured with high fields, at ambient and low temperatures (77 K), has been used to separate ferromagnetic ( sensu lato), paramagnetic and diamagnetic sub-fabrics for deformed limestones located in a nappe structure from southwest Switzerland. The magnetic fabrics are dominantly controlled by paramagnetic and diamagnetic minerals, and ferromagnetic minerals contribute significantly only at two of the eight study locations. Separation of the magnetic sub-fabrics is possible in the root zone and overturned limb of the Morcles Nappe, which contains a high ratio of diamagnetic matrix calcite to paramagnetic secondary phases. Each of the sub-fabrics displays a relationship with structural cleavage and the crystallographic preferred orientation (CPO) of calcite in the root zone and overturned limb. The maximum axis of the paramagnetic AMS ellipsoid ( kmax) lies close to the pole to cleavage, with the intermediate ( kint) and minimum ( kmin) axes near the cleavage plane. Conversely, the diamagnetic kmin lies close to the pole to cleavage with kmax and kint axes near the cleavage plane. Slight offsets in the poles to cleavage and in the principal AMS directions are observed. They are interpreted to be the consequence of a second phase deformation event, affecting only the CPO but not the macroscopic structural elements. The diamagnetic sub-fabric reflects the CPO of calcite, produced through recrystallization during nappe deformation. Iron-rich calcite appears to control the paramagnetic sub-fabric. Susceptibility ellipsoids approach oblate shapes for the diamagnetic sub-fabric, with the most extreme shapes reaching susceptibility differences (? k = kmax - kmin) close to that of single crystal calcite, whereas the paramagnetic sub-fabric is represented mainly by prolate shape ellipsoids. The low-field AMS ellipsoids show mixed oblate and prolate shapes, without consistency within or between sites. It is evident that, when the magnetic sub-fabrics of the root zone and overturned limb are separated, their individual shapes and distribution of principal directions mirror the developed CPO.

Almqvist, Bjarne S. G.; Hirt, Ann M.; Schmidt, Volkmar; Dietrich, Dorothee

2009-03-01

167

The symmetry properties of planetary magnetic fields  

SciTech Connect

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 contributoins are considered. The magnetic fields are analyzed by decomposing them into those parts which have simple symmetry properties with respect to the rotation axis and the equatorial plane. 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, by now rather well known, 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. The implications of these results for dynamo models are discussed. With a vgiew to Cowling's theorem the symmetry of the fields is investigated with respect to not only the rotation axis but also to other axes intersecting the plaentary center. Surprisingly, the high degree of asymmetry of the Uranian field that is observed with respect to the rotation axis reduces considerably to being compare to that for Earth or Jupiter when the appropriate axis is employed.

Raedler, K.H. (Zentral Inst. fuer Astrophysik, Potsdam-Babelsberg (East Germany)); Ness, N.F. (Univ. of Delaware, Newark (United States))

1990-03-01

168

Magnetic Properties of Radiation Damage in Pu and Pu Alloys  

SciTech Connect

Among the many exceptional properties of Pu is its apparent lack of either local moments or cooperative magnetism. Lashley et al., have recently noted that little experimental evidence for the existence of local moments or collective magnetism has been found in over 50 years. Nevertheless the search for local moments in Pu and Pu-alloys continues, why? Plutonium's physical properties: resistance, magnetic susceptibility, and heat capacity, all support a system with an enhanced electron density of states. Pu sits on the edge of both magnetism and superconductivity and possesses one of the highest elemental Pauli susceptibilities, consistent with a highly correlated electron system. The low-density {delta}-Pu has eluded full first principles description and is both a challenge and an area of active investigation for theorists. The complex changes associated with the transition between the light and heavy actinides happen within the phase diagram of Pu, thus making Pu an intriguing and challenging solid-state system for continuing experimental and theoretical investigation. Recently, Griveau et al., observed the variations in the resistance and superconducting properties of Am metal as a function of pressure to 27GPa and T>0.4K. They postulate that the interesting features in the superconducting critical temperature, T{sub c}, vs. pressure, indicate a Mott-like, f-electron localization-delocalization transition as pressure drives Am towards a Pu and then a U-like structure. Hence, we posit that it would be reasonable to expect that dilating the Pu lattice will bring one to a similar transition. Experimental evidence supporting this point of view is given here.

McCall, S; Fluss, M J; Chung, B; Chapline, G; McElfresh, M; Jackson, D; Baclet, N; Jolly, L; Dormeval, M

2005-03-31

169

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

170

Complex magnetic fields breathe life into fluids.  

PubMed

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

Solis, Kyle J; Martin, James E

2014-12-01

171

Magnetic properties of nanosized diluted magnetic semiconductors with band splitting  

Microsoft Academic Search

A continual model of nonuniform magnetism in thin films and wires made of a diluted magnetic semiconductor is considered with regard to the finite spin polarization and band splitting of carriers responsible for the indirect Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between magnetic impurities. Spatial distributions (across the film thickness or along the wire radius) of magnetization and the concentrations of carriers with

E. Z. Meilikhov; R. M. Farzetdinova

2009-01-01

172

Effects of pressure on the sturctural and magnetic properties on Sm based permanent magnets  

NASA Astrophysics Data System (ADS)

The magnetic properties of the rare earth-transition metal permanent magnets are sensitive to interatomic spacing and can be tuned by adjusting these parameters. We report the effects of high pressure on the crystal structure and magnetic properties of Sm2Co17 and Sm2Fe17 measured in diamond anvil cells.

McCall, Scott; Butch, Nicholas; Jeffries, Jason; Huang, Patrick

2013-03-01

173

Annealing effects on magnetic properties of silicone-coated iron-based soft magnetic composites  

E-print Network

Annealing effects on magnetic properties of silicone-coated iron-based soft magnetic composites desired properties in specific applications [1­4]. Insulated iron powder offers several advantages over Permeability a b s t r a c t This paper focuses on novel iron-based soft magnetic composites synthesis

Volinsky, Alex A.

174

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

175

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

176

Quantitative estimates of magnetic field reconnection properties from electric and magnetic field measurements  

E-print Network

Quantitative estimates of magnetic field reconnection properties from electric and magnetic field there are positive electric field components tangential to the magnetopause and a magnetic field component normal to it. Because these three components are the smallest of the six electric and magnetic fields

California at Berkeley, University of

177

Magnetic and screening properties of amorphous ferromagnetic ribbons  

NASA Astrophysics Data System (ADS)

We have studied the magnetic and screening properties of cylindrical shields made of amorphous ferromagnetic ribbons. It is established that the relative magnetic permeability of this material can exceed 106. The action of an alternating decaying magnetic field (demagnetization) converts amorphous ferromagnetic ribbons into the state of anhysteretic magnetization, which is characterized by extremely high (above 2 × 107) values of the relative magnetic permeability in magnetic fields at a level of 10 nT. The results of measurements were used to estimate the coefficient of attenuation of the Earth's magnetic field inside cylindrical shields with open ends, depending on the diameter and the number of layers of an amorphous ferromagnetic ribbon.

Gudoshnikov, S. A.; Grebenshchikov, Yu. B.; Volkov, V. T.; Prokhorova, Yu. V.

2014-10-01

178

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

179

Effect of doping SiO2 on high-frequency magnetic properties for W-type barium ferrite  

Microsoft Academic Search

The microstructure, static and dynamic magnetic and dielectric properties of BaCo1.3Zn0.7Fe16O27 doped with small amounts of SiO2 have been investigated. The results show that the crystal structure and static magnetic properties have no obvious changes as SiO2 varies from 0 to 1 wt %. However, the complex permittivity and complex permeability could be significantly modified by SiO2 doping. Due to

Yuping Wu; Z. W. Li; Linfeng Chen; S. J. Wang; C. K. Ong

2004-01-01

180

Synthesis of the first heterometalic star-shaped oxido-bridged MnCu3 complex and its conversion into trinuclear species modulated by pseudohalides (N3(-), NCS- and NCO-): structural analyses and magnetic properties.  

PubMed

A tetra-nuclear, star-shaped hetero-metallic copper(II)-manganese(II) complex, [{CuL(H(2)O)}(2)(CuL)Mn](ClO(4))(2) (1) has been synthesized by reacting the "complex as ligand" [CuL] with Mn(ClO(4))(2) where H(2)L is the tetradentate di-Schiff base derived from 1,3-propanediamine and 2-hydroxyacetophenone. Upon treatment with the polyatomic anions azide, cyanate, or thiocyanate in methanol medium, complex 1 transforms into the corresponding trinuclear species [(CuL)(2)Mn(N(3))(2)] (2), [(CuL)(2)Mn(NCO)(2)] (3) and [(CuL)(2)Mn(NCS)(2)] (4). All four complexes have been structurally and magnetically characterized. In complex 1 the central Mn(II) ion is encapsulated by three terminal [CuL] units through the formation of double phenoxido bridges between Mn(II) and each Cu(II). In complexes 2-4 one of the CuL units is replaced by a couple of terminal azide, N-bonded cyanate or N-bonded thiocyanate ions respectively and the central Mn(II) ion is connected to two terminal Cu(II) ions through a double asymmetric phenoxido bridge. Variable temperature magnetic susceptibility measurements show the presence of moderate ferrimagnetic exchange interactions in all the cases mediated through the double phenoxido bridges with J values (H = -JS(i)S(i + 1)) of -41.2, -39.8 and -12.6 cm(-1) (or -40.5 and -12.7 cm(-1) if we use a model with two different exchange coupling constants) for the tetranuclear MnCu(3) cluster in compound 1 and -20.0, -17.3 and -32.5 cm(-1) for the symmetric trinuclear MnCu(2) compounds 2-4. These ferrimagnetic interactions lead to spin ground states of 1 (5/2 - 3*1/2) for compound 1 and 3/2 (5/2 - 2*1/2) for compounds 2-4. PMID:22042489

Biswas, Saptarshi; Naiya, Subrata; Gómez-García, Carlos J; Ghosh, Ashutosh

2012-01-14

181

Synthesis, structure, and magnetic properties of a [Mn22] wheel-like single-molecule magnet.  

PubMed

The synthesis and magnetic properties of the compound [Mn(22)O(6)(OMe)(14)(O(2)CMe)(16)(tmp)(8)(HIm)(2)] 1 are reported. Complex 1 was prepared by treatment of [Mn(3)O(MeCO(2))(6)(HIm)(3)](MeCO(2)) (HIm = imidazole) with 1,1,1-tris(hydroxymethyl)propane (H(3)tmp) in MeOH. Complex 1.2MeOH crystallizes in the orthorhombic space group Pbca. The molecule consists of a metallic core of 2 Mn(IV), 18 Mn(III), and 2 Mn(II) ions linked by a combination of 6 micro(3)-bridging O(2)(-) ions, 14 micro(3)- and micro(2)-bridging MeO(-) ions, 16 micro-MeCO(2)(-) ligands, and 8 tmp(3)(-) ligands, which use their alkoxide arms to bridge in a variety of ways. The metal-oxygen core is best described as a wheel made from [Mn(3)O(4)] partial cubes and [Mn(3)O] triangles. Variable-temperature direct current (dc) magnetic susceptibility data were collected for complex 1 in the 1.8-300 K temperature range in a 1 T applied field. The chi(M)T value steadily decreases from 56 cm(3) K mol(-)(1) at 300 K to 48.3 cm(3) K mol(-)(1) at 30 K and then increases slightly to reach a maximum value of 48.6 cm(3) K mol(-)(1) at 15 K before dropping rapidly to 40.3 cm(3) K mol(-)(1) at 5 K. The ground-state spin of complex 1 was established by magnetization measurements in the 0.1-2.0 T and 1.80-4.00 K ranges. Fitting of the data by a matrix-diagonalization method to a model that assumes only the ground state is populated and incorporating only axial zero-field splitting (DS(z)()(2)), gave a best fit of S = 10, g = 1.96 and D = -0.10 cm(-)(1). The ac magnetization measurements performed on complex 1 in the 1.8-8 K range in a 3.5 G ac field oscillating at 50-1000 Hz showed frequency-dependent ac susceptibility signals below 3 K. Single-crystal hysteresis loop and relaxation measurements indicate loops whose coercivities are strongly temperature and time dependent, increasing with decreasing temperature and increasing field sweep rate, as expected for the superparamagnetic-like behavior of a single-molecule magnet, with a blocking temperature (T(B)) of approximately 1.3 K. PMID:15236531

Murugesu, Muralee; Raftery, James; Wernsdorfer, Wolfgang; Christou, George; Brechin, Euan K

2004-07-12

182

Magnetic blocking in a linear iron(I) complex  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

183

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

184

Magnetic memory in an isotopically enriched and magnetically isolated mononuclear dysprosium complex.  

PubMed

The influence of nuclear spin on the magnetic hysteresis of a single-molecule is evidenced. Isotopically enriched Dy(III) complexes are synthesized and an isotopic dependence of their magnetic relaxation is observed. This approach is coupled with tuning of the molecular environment through dilution in an amorphous or an isomorphous diamagnetic matrix. The combination of these approaches leads to a dramatic enhancement of the magnetic memory of the molecule. This general recipe can be efficient for rational optimization of single-molecule magnets (SMMs), and provides an important step for their integration into molecule-based devices. PMID:25486900

Pointillart, Fabrice; Bernot, Kevin; Golhen, Stéphane; Le Guennic, Boris; Guizouarn, Thierry; Ouahab, Lahcène; Cador, Olivier

2015-01-26

185

Symmetry properties of magnetic photonic crystals with simple cubic lattice  

Microsoft Academic Search

We discuss in this paper some general properties of magnetic photonic crystals with simple cubic lattice. Using the theory of magnetic groups, we consider the problem of changing symmetry of photonic crystal with simple cubic lattice by a dc magnetic field and qualitative characteristics of their eigenwaves. The analysis is fulfilled using symmetry arguments alone.

Victor Dmitriev

2006-01-01

186

Modeling the properties of ferrogels in uniform magnetic fields  

Microsoft Academic Search

The properties of ferrogels in homogeneous magnetic fields are studied using a simple microscopic model and Monte Carlo simulations. The main phenomena of interest concern the anisotropy and enhancement of the elastic moduli that result from applying uniform magnetic fields before and after the magnetic grains are locked in to the polymer-gel matrix by cross-linking reactions. The positional organization of

Dean S. Wood; Philip J. Camp

2011-01-01

187

Magnetic and structural properties of isolated and assembled clusters  

Microsoft Academic Search

Within the last years, a fundamental understanding of nanoscaled materials has become a tremendous challenge for any technical applications. For magnetic nanoparticles, the research is stimulated by the effort to overcome the superparamagnetic limit in magnetic storage devices. The physical properties of small particles and clusters in the gas phase, which are considered as possible building blocks for magnetic storage

J. Bansmann; S. H. Baker; C. Binns; J. A. Blackman; J.-P. Bucher; J. Dorantes-Dávila; V. Dupuis; L. Favre; D. Kechrakos; A. Kleibert; K.-H. Meiwes-Broer; G. M. Pastor; A. Perez; O. Toulemonde; K. N. Trohidou; J. Tuaillon; Y. Xie

2005-01-01

188

Magnetic properties of nanosized diluted magnetic semiconductors with band splitting  

Microsoft Academic Search

A continual model of nonuniform magnetism in thin films and wires made of a diluted magnetic semiconductor is considered with\\u000a regard to the finite spin polarization and band splitting of carriers responsible for the indirect Ruderman-Kittel-Kasuya-Yosida\\u000a (RKKY) interaction between magnetic impurities. Spatial distributions (across the film thickness or along the wire radius)\\u000a of magnetization and the concentrations of carriers with

E. Z. Me?likhov; R. M. Farzetdinova

2009-01-01

189

Magnetic properties of stainless steels at room and cryogenic temperatures  

Microsoft Academic Search

The magnetic properties of ten types of ferritic and martensitic stainless steels have been measured at room temperature and at 77K. The steel samples studied were in the annealed state as received from the manufacturer. Our room temperature measurements indicate significantly harder magnetic properties than those quoted in the ASM International Handbook, which studied fully annealed stainless steel samples. Despite

Paul Oxley; Jennifer Goodell; Robert Molt

2009-01-01

190

Mimicking the magnetic properties of rare earth elements using superatoms.  

PubMed

Rare earth elements (REs) consist of a very important group in the periodic table that is vital to many modern technologies. The mining process, however, is extremely damaging to the environment, making them low yield and very expensive. Therefore, mimicking the properties of REs in a superatom framework is especially valuable but at the same time, technically challenging and requiring advanced concepts about manipulating properties of atom/molecular complexes. Herein, by using photoelectron imaging spectroscopy, we provide original idea and direct experimental evidence that chosen boron-doped clusters could mimic the magnetic characteristics of REs. Specifically, the neutral LaB and NdB clusters are found to have similar unpaired electrons and magnetic moments as their isovalent REs (namely Nd and Eu, respectively), opening up the great possibility in accomplishing rare earth mimicry. Extension of the superatom concept into the rare earth group not only further shows the power and advance of this concept but also, will stimulate more efforts to explore new superatomic clusters to mimic the chemistry of these heavy atoms, which will be of great importance in designing novel building blocks in the application of cluster-assembled nanomaterials. Additionally, based on these experimental findings, a novel "magic boron" counting rule is proposed to estimate the numbers of unpaired electrons in diatomic LnB clusters. PMID:25848014

Cheng, Shi-Bo; Berkdemir, Cuneyt; Castleman, A W

2015-04-21

191

Magnetization patterns in ferromagnetic nanoelements as functions of complex variable.  

PubMed

The assumption of a certain hierarchy of soft ferromagnet energy terms, realized in small enough flat nanoelements, allows us to obtain explicit expressions for their magnetization distributions. By minimizing the energy terms sequentially, from the most to the least important, magnetization distributions are expressed as solutions of the Riemann-Hilbert boundary value problem for a function of complex variable. A number of free parameters, corresponding to positions of vortices and antivortices, still remain in the expression. Thus, the presented approach is a factory of realistic Ritz functions for analytical (or numerical) micromagnetic calculations. Examples are given for multivortex magnetization distributions in a circular cylinder, and for two-dimensional domain walls in thin magnetic strips. PMID:20867543

Metlov, Konstantin L

2010-09-01

192

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

193

A new Cu–cysteamine complex: structure and optical properties  

SciTech Connect

Here we report the structure and optical properties of a new Cu–cysteamine complex (Cu–Cy) with a formula of Cu3Cl(SR)2 (R ¼ CH2CH2NH2). This Cu–Cy has a different structure from a previous Cu–Cy complex, in which both thio and amine groups from cysteamine bond with copper ions. Single-crystal X-ray diffraction and solid-state nuclear magnetic resonance results show that the oxidation state of copper in Cu3Cl(SR)2 is +1 rather than +2. Further, Cu3Cl(SR)2 has been observed to show intense photoluminescence and X-ray excited luminescence. More interesting is that Cu3Cl(SR)2 particles can produce singlet oxygen under irradiation by light or X-ray. This indicates that Cu3Cl(SR)2 is a new photosensitizer that can be used for deep cancer treatment as X-ray can penetrate soft tissues. All these findings mean that Cu3Cl(SR)2 is a new material with potential applications for lighting, radiation detection and cancer treatment.

Ma, Lun; Chen, Wei; Schatte, Gabriele; Wang, Wei; Joly, Alan G.; Huang, Yining; Sammynaiken, Ramaswami; Hossu, Marius

2014-06-07

194

Magnetic wire-based sensors for the micro-rheology of complex fluids  

E-print Network

We propose a simple micro-rheology technique to evaluate the viscoelastic properties of complex fluids. The method is based on the use of magnetic wires of a few microns in length submitted to a rotational magnetic field. In this work, the method is implemented on a surfactant wormlike micellar solution that behaves as an ideal Maxwell fluid. With increasing frequency, the wires undergo a transition between a steady and a hindered rotation regime. The study shows that the average rotational velocity and the amplitudes of the oscillations obey scaling laws with well-defined exponents. From a comparison between model predictions and experiments, the rheological parameters of the fluid are determined.

L. Chevry; N. K. Sampathkumar; A. Cebers; J. -F. Berret

2013-11-23

195

Magnetic and magnetothermal properties, and the magnetic phase diagram of single-crystal holmium along the easy magnetization direction  

NASA Astrophysics Data System (ADS)

The magnetic and magnetothermal properties of holmium single crystal have been investigated from 4.2 to 300 K in magnetic fields up to 100 kOe using magnetization and heat capacity data measured along the easy magnetization direction, which is the crystallographic b-axis, i.e. [1 1 \\bar{2} 0] direction. The magnetic phase diagram of Ho has been refined by examining data measured using a high purity single crystal.

Zverev, V. I.; Tishin, A. M.; Min, Zou; Mudryk, Ya; Gschneidner, K. A., Jr.; Pecharsky, V. K.

2015-04-01

196

Magnetic and magnetothermal properties, and the magnetic phase diagram of single-crystal holmium along the easy magnetization direction.  

PubMed

The magnetic and magnetothermal properties of holmium single crystal have been investigated from 4.2 to 300 K in magnetic fields up to 100 kOe using magnetization and heat capacity data measured along the easy magnetization direction, which is the crystallographic b-axis, i.e. [Formula: see text] direction. The magnetic phase diagram of Ho has been refined by examining data measured using a high purity single crystal. PMID:25786610

Zverev, V I; Tishin, A M; Min, Zou; Mudryk, Ya; Jr, K A Gschneidner; Pecharsky, V K

2015-04-15

197

Structural and Magnetic Properties of Co-Mn-Sb Thin films  

SciTech Connect

Thin Co-Mn-Sb films of different compositions were investigated and utilized as electrodes in alumina based magnetic tunnel junctions with CoFe counterelectrode. The preparation conditions were optimized with respect to magnetic and structural properties. The Co-Mn-Sb/Al-O interface was analyzed by x-ray absorption spectroscopy and magnetic circular dichroism with particular focus on the element-specific magnetic moments. Co-Mn-Sb crystallizes in different complex cubic structures depending on its composition. The magnetic moments of Co and Mn are ferromagnetically coupled in all cases. A tunnel magnetoresistance ratio of up to 24% at 13 K was found and indicates that Co-Mn-Sb is not a ferromagnetic half-metal. These results are compared to recent works on the structure and predictions of the electronic properties.

Meinert, M.; Schmalhorst, J.-M.; Ebke, D.; Liu, N. N.; Thomas, A.; Reiss, G.; Kanak, J.; Stobiecki, T.; Arenholz, E.

2009-12-17

198

Magnetic Properties of Anorthosites: Possible Source Rocks for Planetary Magnetic Anomalies  

NASA Astrophysics Data System (ADS)

Anorthosites, rocks composed of 90% plagioclase feldspar, are not uncommon on Earth, predominant on the Moon, and suspected units on both Mars and Mercury. Due to the minor amount of oxide minerals in most anorthosites, they have long been considered weakly-magnetic. We studied four related but distinct anorthosite units (Egersund-Ogna, Haland-Helleren, Ana-Sira and Garsaknatt) in the Rogaland Igneous Complex in Southern Norway, emplaced into Sveconorwegian basement around 930 Ma. Aeromagnetic maps of the region show moderate positive to large negative anomalies associated with the anorthosites. Measurements on 43 sites (279 samples) of susceptibility, natural remanent magnetization (NRM) and hysteresis properties provide a startling picture of the magnetic behavior of these rocks. Mean NRM values on each anorthosite range from a low of 0.6 A/m on the Egersund-Ogna body to 5.9 A/m on the Haland-Helleren, placing these rocks in similar NRM range to young basalts. Susceptibility varies widely from body to body, with a low of 4.88 x 10-4 SI on the Egersund-Ogna to 2.40 x 10-2 SI on the Haland-Helleren. All units have average Koenigsberger Ratio (Q) values greater than 1, ranging from 8 for the Garsaknatt to 61 for the Egersund-Ogna. With the exception of a few samples in the Garsaknatt, mean destructive fields for alternating field demagnetization for all bodies are greater than 40 mT. Most samples show considerable intensity remaining after thermal demagnetization to 560C and appreciable amounts above 580C. Hysteresis properties from the anorthosites show a wide range of Mr/Ms and Hcr/Hc values. Optical investigation of polished sections reveals the presence hemo-ilmenite in Ana Sira, Egersund-Ogna and Haland-Helleren anorthosites. Minor amounts of magnetite are restricted to the Garsaknatt and parts of the Haland-Helleren anorthosites. Although these four anorthosites have a wide range of magnetic properties, they all have appreciable remanent magnetization and all are capable of producing moderate to strong remanent-dominated anomalies. Because anorthosites are common on the Moon and suggested to exist on other planets, these rocks should be considered as possible sources for planetary paleomagnetism and/or magnetic anomalies.

Brown, L. L.; McEnroe, S. A.

2006-12-01

199

2.20 Properties of Rocks and Minerals -Magnetic Properties of Rocks and Minerals  

E-print Network

2.20 Properties of Rocks and Minerals - Magnetic Properties of Rocks and Minerals R. J. Harrison, R 621 622 623 623 579 #12;580 Magnetic Properties of Rocks and Minerals 2.20.5.3 2.20.5.4 2, and are present in all types of rocks, sediments, and soils. These minerals retain a memory of the geomagnetic

Dunin-Borkowski, Rafal E.

200

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

PubMed Central

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

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

2014-01-01

201

High-resolution nuclear magnetic resonance in paramagnetic complexes  

NASA Astrophysics Data System (ADS)

The features of the phenomenon of nuclear magnetic resonance in paramagnetic systems are considered. Specific character of detection of high-resoluton NMR spectra modified by hyperfine coupling is analyzed. Examples of the use of specific features of nuclear magnetic resonance in paramagnetic complexes in studies of the structure and dynamics of multielectron systems are given. The need for further experimental investigations of the nature of paramagnetic shifts (especially, contact ones) of NMR signals not only of 1H and 13C, but also of other nuclei is emphasized.

Voronov, Vladimir K.; Ushakov, Igor A.

2010-12-01

202

Magnetic properties of cobalt nitride thin films  

Microsoft Academic Search

Cobalt nitride (CoNx) thin films with a large perpendicular magnetic anisotropy are synthesized by reactive sputtering. The perpendicular magnetic anisotropy is induced by substrate heating during deposition, annealing after deposition, or ion bombardment during deposition.

Morito Matsuoka; Ken'ichi Ono; Takashi Inukai

1986-01-01

203

Spectacular Magneto-Related Properties of Complex Oxides  

Microsoft Academic Search

\\u000a Perovskite manganites display unusual correlations between magnetic, electronic, and structural properties that are caused\\u000a by strong electron-electron and electron-phonon interactions. In this paper we discuss spectacular magneto-related structural,\\u000a resistive, and thermo-caloric properties originating from magnetic, orbital, and charge ordering. Detailed neutron diffraction,\\u000a striction, and magnetic measurements demonstrate a wealth of novel behavior observed for these compounds: the structural transformation\\u000a induced

B. Dabrowski; S. Kolesnik; O. Chmaissem; Z. Bukowski; J. Mais; C. W. Kimball; A. Szewczyk; A. Wisniewski; L. Gladczuk; K. Piotrowski; R. Kartaszynski; M. Gutowska; H. Szymczak; J. D. Jorgensen

204

Low-dimensional compounds containing cyano groups. XIV. Crystal structure, spectroscopic, thermal and magnetic properties of [CuL {sub 2}][Pt(China){sub 4}] complexes (L=ethylenediamine or N,N-dimethylethylenediamine)  

SciTech Connect

Violet crystals of [Cu(en){sub 2}][Pt(China){sub 4}] and blue crystals of [Cu(dmen){sub 2}][Pt(China){sub 4}] were crystallized from the water-methanol solution containing CuCl{sub 2}.2H{sub 2}O, ethylenediamine (en) or N,N-dimethylethylenediamine (dmen) and K{sub 2}[Pt(China){sub 4}].3H{sub 2}O. Both compounds were characterized using elemental analysis, infrared and UV-VIS spectroscopy, magnetic measurements, specific heat measurements and thermal analysis. X-ray structure analysis revealed chain-like structure in both compounds. The covalent chains are built of Cu(II) ions linked by [Pt(China){sub 4}]{sup 2-} anions in the [111] and [101] direction, respectively. The Cu(II) atoms are hexacoordinated by four nitrogen atoms in the equatorial plane from two molecules of bidentate ligands L with average Cu-N distance of 2.022(2) and 2.049(4) A, respectively. Axial positions are occupied by two nitrogen atoms from bridging [Pt(China){sub 4}]{sup 2-} anions at longer Cu-N distance of 2.537(2) and 2.600(5) A, respectively. Both materials are characterized by the presence of weak antiferromagnetic exchange coupling. Despite the one-dimensional (1D) character of the structure, the analysis of magnetic properties and specific heat at very low temperatures shows that [Cu(en){sub 2}][Pt(China){sub 4}] behaves as two-dimensional (2D) spatially anisotropic square lattice Heisenberg magnet, while more pronounced influence of interlayer coupling is observed in [Cu(dmen){sub 2}][Pt(China){sub 4}]. - Graphical abstract: Chain-like structure in [Cu(en){sub 2}][Pt(China){sub 4}] (R=H) and [Cu(dmen){sub 2}][Pt(China){sub 4}] (R=CH{sub 3}) compounds.

Potocnak, Ivan [Department of Inorganic Chemistry, Institute of Chemistry, P.J. Safarik University, Moyzesova 11, SK-04154 Kosice (Slovakia)]. E-mail: ivan.potocnak@upjs.sk; Vavra, Martin [Department of Inorganic Chemistry, Institute of Chemistry, P.J. Safarik University, Moyzesova 11, SK-04154 Kosice (Slovakia); Cizmar, Erik [Centre of Low Temperature Physics of the Faculty of Science of P.J. Safarik University and IEP SAS, Park Angelinum 9, SK-04154 Kosice (Slovakia); Tibenska, Katarina [Centre of Low Temperature Physics of the Faculty of Science of P.J. Safarik University and IEP SAS, Park Angelinum 9, SK-04154 Kosice (Slovakia); Orendacova, Alzbeta [Centre of Low Temperature Physics of the Faculty of Science of P.J. Safarik University and IEP SAS, Park Angelinum 9, SK-04154 Kosice (Slovakia); Steinborn, Dirk [Institute of Inorganic Chemistry, Martin-Luther-University, Halle-Wittenberg, Kurt-Mothes-Street 2, D-06120 Halle (Germany); Wagner, Christoph [Institute of Inorganic Chemistry, Martin-Luther-University, Halle-Wittenberg, Kurt-Mothes-Street 2, D-06120 Halle (Germany); Dusek, Michal [Institute of Physics, Na Slovance 2, CZ-182 21 Praha 8 (Czech Republic); Fejfarova, Karla [Institute of Physics, Na Slovance 2, CZ-182 21 Praha 8 (Czech Republic); Schmidt, Harry [Institute of Inorganic Chemistry, Martin-Luther-University, Halle-Wittenberg, Kurt-Mothes-Street 2, D-06120 Halle (Germany); Muller, Thomas [Institute of Inorganic Chemistry, Martin-Luther-University, Halle-Wittenberg, Kurt-Mothes-Street 2, D-06120 Halle (Germany); Orendac, Martin [Centre of Low Temperature Physics of the Faculty of Science of P.J. Safarik University and IEP SAS, Park Angelinum 9, SK-04154 Kosice (Slovakia); Feher, Alexander [Centre of Low Temperature Physics of the Faculty of Science of P.J. Safarik University and IEP SAS, Park Angelinum 9, SK-04154 Kosice (Slovakia)

2006-07-15

205

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

206

Magnetic properties of the Bay of Islands ophiolite suite and implications for the magnetization of oceanic crust  

USGS Publications Warehouse

Rock magnetic properties, opaque mineralogy, and degree of metamorphism were determined for 101 unoriented samples from the North Arm and Blow-Me-Down massifs of the Bay of Islands ophiolite complex, Newfoundland. The weathered and metamorphosed extrusive basalt samples have a weak, secondary magnetization arising from oxidation and exsolution of ilmenite of unknown origin. The initial magnetization of the underlying sheeted dike complex appears to have been destroyed by hydrothermal alteration soon after formation. The magnetic intensity of the gabbroic samples increases as the degree of alteration increases, with the highly altered upper metagabbros having an average intensity of 3×10?3 emu/c3. Because magnetization of the metagabbro samples is related to nonpervasive, variable alteration, these crustal units are unlikely to make a significant contribution to lineated magnetic anomalies. A compilation of our results and other studies suggests a model in which oceanic crust magnetization results from an upper extrusive basalt source layer, roughly 600 m thick, with no contribution from a deeper source layer recognizable from these Bay of Islands data.

Swift, B. Ann; Johnson, H. Paul

1984-01-01

207

Magnetic properties of RbBp.2Ttg  

NASA Astrophysics Data System (ADS)

The crystal structure of RbBp.2Ttg (Bp = biphenyl and Ttg = Tetraglyme = CH3O(CH2CH2O)4CH3) shows the presence of layers of paramagnetic biphenyl anions separated by layers of alkali-glyme complexes. This structure suggests two-dimensional magnetic behaviour. The magnetic properties of these crystals were studied with E.P.R. in the temperature range from 300 to 1·2K. Above 25K the anisotropy in the linewidth of the exchange-narrowed E.P.R. line and the deviations from the lorentzian lineshape demonstrate the importance of spin diffusion. Both results are in agreement with theoretical predictions made for pseudo 2-d magnetic systems. In the magnetic layer two biphenyl anions are lying closely together while all the others are further apart. This is reflected in the susceptibility which may be described by the singlet-triplet model with J = -13K. Upon cooling no E.P.R. signals of isolated triplets are observed. Instead, at 1·2 K a well resolved spectrum arises, which could be ascribed to isolated biphenyl anions in the doublet state. The spectra can be simulated perfectly. From the simulations we could conclude that the biphenyl anions are oriented according to the crystal structure. The concentration of the anions is about 1 per cent. An explanation of their occurrence is given. At high microwave powers a double quantum transition was observed in the temperature range from 3 to 7 K. This has been attributed to a transition from the |-1> to the |+1> state of the triplet manifold. It gains a high probability at orientations where the dipolar interaction is zero ('magic angle').

Gribnau, M. C. M.; Pikkemaat, J. A.; de Boer, E.

208

Magnetic properties of intermediate-mass stars  

E-print Network

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

G. A. Wade

2006-01-30

209

Magnetic and Superconducting Properties of Vanadium Nanoconstrictions  

NASA Astrophysics Data System (ADS)

We study the magnetic and superconducting properties in a paramagnetic vanadium (V) nanoconstriction with changing its size using a mechanically controllable break junction technique. In the normal state the magnetoresistance effect is observed below the diameter d ~ 8 nm. Moreover, a Fano resonance appears around zero-bias voltage in the differential conductance for the atomic-size contacts and changes shape as the size of the constriction changes. On the other hand, below the superconducting critical temperature the superconducting gap features in V contacts are largely different from those in Pb contacts which exhibit typical features expected in superconducting point contacts. Only a single Andreev anomaly at 2?, where ? is the superconducting energy gap, is observed in the spectra of the V contacts, while two anomalies at ? and 2? appear in the case of the Pb contacts. In the tunnel conductance regime, the structure of the superconducting quasiparticle tunneling density of states is not seen in the V spectra in contrast to the Pb spectra. The origin of these features is discussed.

Takata, Hiroki; Inagaki, Yuji; Kawae, Tatsuya; Ienaga, Koichiro; Tsujii, Hiroyuki

2015-03-01

210

Binuclear nickel complexes with an edge sharing bis(square-pyramidal) N3Ni(?-S2)NiN3 core: synthesis, characterization, crystal structure and magnetic properties.  

PubMed

The synthesis of the novel macrocyclic octadentate amino-thiophenolate ligand H(2)L2 (3,7,11,19,23,27-hexaaza-33,34-dithiol-15,31-di(tert-butyl)-tricyclo[27,3,1(13.17)]-tetratriaconta-1(32),13,15,17(34),29,30-hexane) and its ability to support binuclear nickel(II) complexes with dithiolato-bridged square-pyramidal Ni(II) ions are reported. H(2)L2 is obtained as the hexahydrobromide salt from a Schiff-base condensation reaction between 1,2-bis(4-tert-butyl-2,6-diformylphenylthio)ethane and bis(3-aminopropyl)amine followed by two successive reductions with NaBH(4) and Na/NH(3). The ligand forms a green, paramagnetic, binuclear nickel(II) complex dication [Ni(II)(2)L2](2+), which can be isolated as a ClO(4)(-) (4) or BPh(4)(-) salt (5). The binuclear nickel(II) complex contains a central N(3)Ni(?-S)(2)NiN(3) core with two square-pyramidal coordinated Ni(II) ions. The [Ni(2)L2](2+) dication does not bind further coligands, in striking contrast to the behaviour of the parent [Ni(2)L1](2+) dication supported by the smaller (L1)(2-) macrocycle (containing diethylenetriamine in place of the dipropylenetriamine units) which readily binds a variety of other coligands (L') to form bisoctahedral [Ni(2)L1(L')](+) structures. The unusual behaviour of 4 relates to two different N configurations which leads to a steric shielding of the third bridging position by the CH(2)-groups of the dipropylenetriamine chains. An analysis of the temperature-dependent magnetic susceptibility data of 5 reveals the presence of a weak antiferromagnetic exchange interaction between the spins of the nickel(II) ions with a value for the magnetic exchange coupling constant J of -23.5 cm(-1) (H = -2JS(1)S(2)). These results are further substantiated by DFT calculations. PMID:23108013

Lehmann, Ulrike; Lach, Jochen; Loose, Claudia; Hahn, Torsten; Kersting, Berthold; Kortus, Jens

2013-01-28

211

Magnetic properties of stainless steels at room and cryogenic temperatures  

NASA Astrophysics Data System (ADS)

The magnetic properties of ten types of ferritic and martensitic stainless steels have been measured at room temperature and at 77 K. The steel samples studied were in the annealed state as received from the manufacturer. Our room temperature measurements indicate significantly harder magnetic properties than those quoted in the ASM International Handbook, which studied fully annealed stainless steel samples. Despite having harder magnetic properties than fully annealed steels some of the as-received steels still display soft magnetic properties adequate for magnetic applications. The carbon content of the steels was found to affect the permeability and coercive force, with lower-carbon steels displaying significantly higher permeability and lower coercive force. The decrease in coercive force with reduced carbon content is attributed to fewer carbide inclusions which inhibit domain wall motion. Cooling to 77 K resulted in harder magnetic properties. Averaged over the ten steels tested the maximum permeability decreased by 8%, the coercive force increased by 14%, and the residual and saturation flux densities increased by 4% and 3%, respectively. The change in coercive force when cooled is comparable to the theoretical prediction for iron, based on a model of domain wall motion inhibited by inclusions. The modest changes of the magnetic properties indicate that the stainless steels can still be used in magnetic applications at very low temperatures.

Oxley, Paul; Goodell, Jennifer; Molt, Robert

2009-07-01

212

Deep structure of the Mount Amram igneous complex, interpretation of magnetic and gravity data  

NASA Astrophysics Data System (ADS)

The Mt Amram igneous complex (AIC) represents northern tip of the Neoproterozoic Arabian Nubian Shield (ANS). For the first time the AIC deep structure was studied using the gravity, aero and ground magnetic, magnetic susceptibility and density measurements and geological data. Analysing all available data at the Amram area we concluded what only monzonite body can be reason for gravity high and coinciding reduced to pole (RTP) maximum. Geological knowledge allowed suggesting its intrusive character and compact body form. Cluster of inverse solutions (Werner deconvolution) localized this body as initial model for forward modelling. Further iterations (23/4-D forward modelling) clarified the monzonite geometry and properties; the modelling allowed also to investigate the non-uniqueness and estimate also the confident intervals for final solution. The research consists three interconnected stages. At the detailed scale, ground magnetic data suggested three magmatic blocks of few hundred meters shifted dextral about 100 m along the Zefunut fault. Estimated accuracy for geometry of the magnetic bodies is a few tens metres. At the middle scale, quantitative gravity and magnetic interpretations provide model of the monzonite body, which is an order of magnitude more than the volume of the felsic rhyolites and granite rocks. Boundary of the whole monzonite body was estimated with accuracy as a hundred meters. As a result we suggest that the parent magma for the AIC is the monzonite, similar to the model suggested for the Timna Igneous Complex 12 km north of the AIC. The model developed can be applied to evaluate the subsurface volumes of the mafic magmatic rocks in adjacent locations. At the regional scale for exposed the Sinai and Arab Saudi Precambrian crystalline shield our approach allows to understand the apparent contradiction between geological predominantly granite composition (low magnetic rocks) and magnetic data. The aeromagnetic data show number strong magnetic anomalies suggesting the presence large volume of high magnetic (mainly basic) rocks at the depth. This problem is proposed for future research.

Shirman, Boris; Rybakov, Michael; Beyth, Michael; Mushkin, Amit; Ginat, Hanan

2015-03-01

213

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

214

Studies of zinc phthalocyanine/magnetic fluid complex as a bifunctional agent for cancer treatment  

NASA Astrophysics Data System (ADS)

The present study introduces a new class of material that allows the combined action of photodynamic therapy (PDT) and hyperthermia (HPT) therapies, designed to work in a synergetic way when used in vivo, with an expected enhancement in tumor damaging after minimum drug doses and based on heat dissipation and/or light photosensitization. With this purpose, we have investigated the spectroscopic and photophysical properties of the complex zinc phthalocyanine/magnetic fluid (ZnPC/MF) in homogeneous medium (ethanol). Our findings clearly indicate that the spectroscopic properties of ZnPC as a photosensitizer associated or not with MF present similar behavior working efficiently as a PDT drug.

Oliveira, D. M.; Macaroff, P. P.; Ribeiro, K. F.; Lacava, Z. G. M.; Azevedo, R. B.; Lima, E. C. D.; Morais, P. C.; Tedesco, A. C.

2005-03-01

215

Dissociation of ligand-receptor complexes using magnetic tweezers.  

PubMed

We present a new tool for measuring ligand-receptor complex bonds at the single-molecule level using magnetic tweezers. Our apparatus allows massively parallel (100-1000) measurements on many single complexes perturbed by constant forces. Compared to other single-molecule techniques, our method is simple, inexpensive, robust, and widely compatible with other techniques. We immobilized specific receptor molecules on the surface of superparamagnetic beads and corresponding ligand molecules on a fixed surface. The beads were allowed to contact the surface so that ligand-receptor binding occurred. A permanent magnet then generated a constant force that pulled the receptors away from the ligands. The rates at which bound species separated at various forces allowed us to characterize the potential energy landscape of the bond and extrapolate bulk solution kinetic rates and transition-state distances. These values agreed with those obtained using bulk and single-molecule methods. PMID:15889889

Danilowicz, Claudia; Greenfield, Derek; Prentiss, Mara

2005-05-15

216

Magnetic Properties of Co doped ZnS Diluted Magnetic Semiconductor  

NASA Astrophysics Data System (ADS)

The magnetic properties of Zn0.9Co0.1S nanoparticles synthesized by solid state reaction method are presented. The nanoparticles are crystallized with zinc-blende structure. The variation of magnetic properties stems from the changes of the local structure around Co ions and the distribution of Co ions, given by X-ray absorption fine structures.

Hou, Qingteng; Chen, Kai; Zhang, Hongguang; Li, Yongtao; Liu, Hao; Dong, Xueguang; Huang, Yongchao; Li, Qi

2013-04-01

217

Magnetic Structure and Magnetic Properties of CaMn2Sb2  

Microsoft Academic Search

The AM2X2 ternary intermetallic (A = rare or alkaline earth, M = transition metal) compounds have revealed interesting magnetic properties due to the interplay between their magnetic sublattices. Pursuing the idea that the coupling between Mn-Mn ions can significantly affect electric transport properties, we investigated (Ca,Sr)Mn2Sb2 intermetallic compounds which presents two secondary magnetic transitions at 82K and 250K. Field dependent

A. L. Lima Sharma; A. M. S. Gomes; J. L. Gonzales; W. Ratcliff II

2008-01-01

218

Magnetic Properties of Chemical Vapour Deposited Cobalt Doped Gamma Iron Oxide Thin Films  

Microsoft Academic Search

Magnetic properties of chemical vapour deposited (CVD) Fe3O4 and gamma-Fe2O3 obtained by co-pyrolysis of ferric and cobaltus acetyl acetonate complexes are described. Saturation magnetization, remanent magnetization and coercivity value of 3.7 kG, 2.2 kG and 820 Oe respectively have been obtained for Co-gamma Fe2O3 films. Chemically vapour deposited Co-Fe3O4 films are laterally inhomogeneous with only a fraction of Co2+ ions

Sandip Dhara; Ravinder Kumar Kotnala; Alok Chandra Rastogi; Bijoy Kishore Das

1992-01-01

219

Hard magnetic properties of melt-spun Mn-Al-C alloys , F. Mazaleyrat1  

E-print Network

technological properties (mechanical strength, machinability, corrosion resistance) and low cost (no rare earth for permanent magnet applications due to good magnetic properties (superior to conventional ferrites), high

Paris-Sud XI, Université de

220

Magnetic structure and magnetic properties of Nd1?xNaxMnO3 compounds  

Microsoft Academic Search

The crystal structure, magnetic structure, and magnetic properties of Nd1-xNaxMnO3 (x = 0, 0.15, and 0.20) compounds were studied using magnetization and neutron powder diffraction techniques. The magnetic ordering is found to undergo a transition from A-type antiferromagnetic (AFM) structure for x = 0 to pseudo charge-exchange (CE)-type AFM phase for x = 0.20 through the spin canted ferromagnetic (FM)

B. Samantaray; S. Ravi; A. Das; S. K. Srivastava

2011-01-01

221

Magnetic properties and magnetoresistance of Bi and Fe substituted manganites  

NASA Astrophysics Data System (ADS)

In this work structure, magnetic and transport properties of La 0.7- x Bi xCa 0.3MnO 3 (0.05? x?0.7), La 0.7Pb 0.3Mn 1- xFe xO 3 and La 0.7Sr 0.3Mn 1 -xFe xO 3 (0? x?0.3) manganites have been studied. Competition between ferromagnetic and antiferromagnetic interactions has been observed giving rise to complex magnetic behaviour, including metamagnetism and spin glass features. Such features are interpreted as arising from the weakening of the double exchange mechanism, of ferromagnetic character, as a consequence of the substitutions. In the case of Bi substituted compounds the covalent character of Bi strongly localizes the hopping electron, while the Fe substitution destroys the double exchange mechanism by the change in energy levels of the Fe 4+ ions with respect to the Mn 4+ ones.

Barandiaran, J. M.; Gutiérrez, J.; Righi, L.; Amboage, M.; Peña, A.; Hernández, T.; Insausti, M.; Rojo, T.

2001-06-01

222

Microwave properties of composites with glass coated amorphous magnetic microwires  

NASA Astrophysics Data System (ADS)

The complex permittivity and permeability of composites filled with Fe-based microwires are measured in a coaxial line at frequencies from 0.01 to 10 GHz.The samples under study consist of closely packed wire sections with various orientations relative to wave vector. The composites, where the wires are collinear to the coaxial axis, are found to be low permeable. Their permittivity has frequency dispersion governed by the length of the wire and its linear impedance. The middle section of the wire has higher impedance than that of the end sections where the regular domain structure is distorted. Magnetic bias parallel to the wire axis affects the linear impedance and parameters of dielectric absorption of a composite, the effect is proportional to bias strength. The samples of a coil-type structure, where the wires are wound around the coaxial axis, display the intensive magnetic absorption attributed to the domain wall motion. The absorption takes place in the megahertz band, at microwaves the permeability is close to unity. The microwave properties of diluted composites filled with randomly oriented permeable wires are discussed.

Starostenko, S. N.; Rozanov, K. N.; Osipov, A. V.

2006-03-01

223

Metastable epitaxial magnets: A study of growth and magnetic properties  

Microsoft Academic Search

Recent advancement in the information storage industry is demanding more fundamental understanding of magnetic systems, especially the magnetic thin films, surfaces, and interfaces. In this work, we were focusing on ultrathin ferromagnetic thin films of Ni on Cu(100), Cu(110) and Cu(111) single crystal substrates, and FeNi and CoNi binary alloy films on Cu(100) with varying atomic concentration. The growth of

Stella Zhong Wu

1997-01-01

224

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

225

Correlation Between Domain Behavior and Magnetic Properties of Materials  

SciTech Connect

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

Jeffrey Scott Leib

2003-05-31

226

EM Properties of Magnetic Minerals at RADAR Frequencies  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

227

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

228

Structural, spectroscopic and magnetic properties of M[R2P(E)NP(E)R'2]2 complexes, M = Co, Mn, E = S, Se and R, R' = Ph or iPr. Covalency of M-S bonds from experimental data and theoretical calculations.  

PubMed

The S/Se-containing bidentate ligands LH of the type R2P(E)NHP(E)R'2, E = S, Se and R, R' = Ph or iPr have been employed to synthesize ML2 (M = Mn, Co) complexes which contain the biologically important MS4 core. Theoretical calculations on the LH and L- forms of the ligands probe the geometric and electronic changes induced by the deprotonation of the LH form, which are correlated with structural data from X-ray crystallography. These results reflect the flexibility of the ligands, which enables them to be rather versatile with respect to the formation of ML2 complexes with varied geometries and MEPNPE metallacycle conformations. A series of old and new ML2 complexes have been synthesized and their structural, spectroscopic and magnetic properties characterized in detail. The nephelauxetic ratio beta of the CoL2 complexes provides evidence of covalent interactions, whereas the EPR properties of the MnL2 complexes are interpreted on the basis of predominant ionic interactions, between the metal center and the ligands, respectively. Additional evidence for the existence of covalent interactions in the CoL2 complexes (R = Ph, iPr, or mixed Ph/iPr), is offered by comparisons between their 31P NMR. The aforementioned notations are supported by extensive theoretical calculations on the ML2 (E = S, R = Me) modelled structures, which probe the covalent and ionic character of the M-S bonds when M = Co or Mn. Wider implications of the findings of the present study on the M-S covalency and its importance in the active sites of various metalloenzymes are also discussed. PMID:16688318

Maganas, Dimitrios; Staniland, Sarah S; Grigoropoulos, Alexios; White, Fraser; Parsons, Simon; Robertson, Neil; Kyritsis, Panayotis; Pneumatikakis, Georgios

2006-05-21

229

Magnetic and magnetothermal properties and the magnetic phase diagram of high purity single crystalline terbium along the easy magnetization direction  

SciTech Connect

The magnetic and magnetothermal properties of a high purity terbium single crystal have been re-investigated from 1.5 to 350 K in magnetic fields ranging from 0 to 75 kOe using magnetization, ac magnetic susceptibility and heat capacity measurements. The magnetic phase diagram has been refined by establishing a region of the fan-like phase broader than reported in the past, by locating a tricritical point at 226 K, and by a more accurate definition of the critical fields and temperatures associated with the magnetic phases observed in Tb.

Zverev, V. I. [M V Lomonosov Moscow State University; Tishin, A. M. [M V Lomonosov Moscow State University; Chernyshov, A. S. [Advanced Media Development; Mudryk, Ya [Ames Laboratory; Gschneidner Jr., Karl A. [Ames Laboratory; Pecharsky, Vitalij K. [Ames Laboratory

2014-01-21

230

Tuning the photophysical properties of amidophosphine complexes of copper  

E-print Network

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

Mickenberg, Seth F. (Seth Fox)

2009-01-01

231

Investigation of the magnetic properties and magnetic structure parameters of nanocrystalline Fe 79 Zr 10 N 11 films  

Microsoft Academic Search

The magnetic properties (magnetization curve, ferromagnetic resonance spectrum) of nanocrystalline Fe79Zr10N11 films obtained by RF magnetron sputtering with subsequent annealing were studied experimentally, along with the fundamental\\u000a magnetic constants of these films (saturation magnetization M\\u000a S, local magnetic anisotropy energy K, and the exchange coupling constant A). The magnetic properties are discussed within the random magnetic model, which determines the

E. N. Sheftel’; S. V. Komogortsev; R. S. Iskhakov; P. K. Sidorenko; L. A. Chekanova; N. S. Perov; A. N. Ivanov

2010-01-01

232

Magnetic Properties and Structure of Oxyhemoglobin  

Microsoft Academic Search

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

Linus Pauling

1977-01-01

233

Magnetic properties of Ni substituted Y-type barium ferrite  

NASA Astrophysics Data System (ADS)

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

Won, Mi Hee; Kim, Chul Sung

2014-05-01

234

Magnetic properties of Ni substituted Y-type barium ferrite  

SciTech Connect

Y-type barium hexaferrite is attractive material for various applications, such as high frequency antennas and RF devices, because of its interesting magnetic properties. Especially, Ni substituted Y- type hexaferrites have higher magnetic ordering temperature than other Y-type. We have investigated macroscopic and microscopic properties of Y-type barium hexaferrite. Ba{sub 2}Co{sub 2?x}Ni{sub x}Fe{sub 12}O{sub 22} (x?=?0, 0.5, 1.0, 1.5, and 2.0) samples are prepared by solid-state reaction method and studied by X-ray diffraction (XRD), vibrating sample magnetometer, and Mössbauer spectroscopy, as well as a network analyzer for high frequency characteristics. The XRD pattern is analyzed by Rietveld refinement method and confirms the hexagonal structure with R-3m. The hysteresis curve shows ferrimagnetic behavior. Saturation magnetization (M{sub s}) decreases with Ni contents. Ni{sup 2+}, which preferentially occupies the octahedral site with up-spin sub-lattice, has smaller spin value S of 1 than Co{sup 2+} having S?=?3/2. The zero-field-cooled (ZFC) measurement of Ba{sub 2}Co{sub 1.5}Ni{sub 0.5}Fe{sub 12}O{sub 22} shows that Curie and spin transition temperatures are found to be 718?K and 209?K, respectively. The Curie temperature T{sub C} is increased with Ni contents, while T{sub S} is decreased with Ni. The Mössbauer spectra were measured at various temperatures and fitted by using a least-squares method with six sextet of six Lorentzian lines for Fe sites, corresponding to the 3b{sub VI}, 6c{sub IV}*, 6c{sub VI}, 18h{sub VI}, 6c{sub IV}, and 3a{sub IV} sites at below T{sub C}. From Mössbauer measurements, we confirmed the spin state of Fe ion to be Fe{sup 3+} and obtained the isomer shift (?), magnetic hyperfine field (H{sub hf}), and the occupancy ratio of Fe ions at six sub-lattices. The complex permeability and permittivity are measured between 100?MHz and 4?GHz, suggesting that Y-type barium hexaferrite is promising for antenna applications in UHF band.

Won, Mi Hee; Kim, Chul Sung, E-mail: cskim@kookmin.ac.kr [Department of Physics, Kookmin University, Seoul 136-702 (Korea, Republic of)

2014-05-07

235

Studies on magneto-transport properties of dilute magnetic semiconductors  

Microsoft Academic Search

Diluted magnetic semiconductors (DMS) are rare group of promising semiconductors in which a fraction of the constituent ions is replaced by magnetic ions. This study is aimed to understand the magneto-transport properties of magnetic ion doped In2O3 thin films. The films were grown under different temperature and partial oxygen pressures by pulsed laser deposition. The films were characterized using various

R. Gupta; A. Ghosh; Y. Kolekar; K. Ghosh; P. Kahol

2011-01-01

236

Magnetization reversal behavior in complex shaped Co nanowires: A nanomagnet morphology optimization  

NASA Astrophysics Data System (ADS)

A systematic micromagnetic study of the morphological characteristic effects over the magnetic static properties of Co-based complex shaped nanowires is presented. The relevance of each characteristic size (i.e., length L, diameter d, and size of the nanowires head T) and their critical values are discussed in the coercive field optimization goal. Our results strongly confirms that once the aspect ratio ( L/d ) of the nanowire is bigger than around 10, the length is no more the pertinent parameter and instead the internal diameter and the shape of the nanowires play a key role. We attribute this behavior to the non uniform distribution of the demagnetizing field which is localized in the nanowires head and acts as a nucleation point for the incoherent magnetization reversal. Finally, angular dependence of the magnetization is simulated and compared to the case of a prolate spheroid for all considered morphologies.

Zighem, Fatih; Mercone, Silvana

2014-11-01

237

Magnetic properties of dense holographic QCD  

E-print Network

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

Oren Bergman; Gilad Lifschytz; Matthew Lippert

2009-04-30

238

Magnetic properties of some iron powders and ore concentrates  

Microsoft Academic Search

In the manufacture of separators for the enrichment of the iron powders and ore concentrates being produced at the Novotul'sk Iron and Steel Plant, it is necessary to know the magnetic properties of these materials, since the principal factor distinguishing the process of propagation of electromagnetic waves in a ferromagnetic material is inconstancy of magnetic permeability. The latter grows in

G. D. Degtyareva; V. L. Shvartsman

1974-01-01

239

Electronic and magnetic properties of ultrathin rhodium nanowires  

Microsoft Academic Search

The structures of ultrathin rhodium nanowires are studied using empirical molecular dynamics simulations with a genetic algorithm. Helical multishell cylindrical and pentagonal packing structures are found. The electronic and magnetic properties of the rhodium nanowires are calculated using an spd tight-binding Hamiltonian in the unrestricted Hartree-Fock approximation. The average magnetic moment and electronic density of states are obtained. Our results

Baolin Wang; Guanghou Wang; Yun Ren; Houqian Sun; Xiaoshuang Chen; Jijun Zhao

2003-01-01

240

Improving the magnetic properties of hydrothermally synthesized barium ferrite  

Microsoft Academic Search

The formation of fine barium ferrite (BaFe12O19) powders under hydrothermal conditions at [OH?]\\/[NO3?] ratio of 2 has been examined by employing barium nitrate and ferric nitrate as the starting materials. The effects of Ba\\/Fe ratio, reaction temperature and time on the formation, particle size, and magnetic properties of barium ferrite were studied. To further enhance the magnetic properties of hydrothermally

Xiangyuan Liu; John Wang; Leong-Ming Gan; Ser-Choon Ng

1999-01-01

241

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

242

Colossal anisotropy of the magnetic properties of doped lithium nitrodometalates  

NASA Astrophysics Data System (ADS)

We present a first-principles investigation of the electronic structure and physical properties of doped lithium nitridometalates Li2(Li1-xMx)N (LiMN) with M = Cr, Mn, Fe, Co, and Ni. The diverse properties include the equilibrium magnetic moments, magneto-crystalline anisotropy, magneto-optical Kerr spectra, and x-ray magnetic circular dichroism. We explain the colossal magnetic anisotropy in LiFeN by its unique electronic structure which ultimately leads to a series of unusual physical properties. The most unique property is a complete suppression of relativistic effects and freezing of orbital moments for in-plane orientation of the magnetization. This leads to the colossal spatial anisotropy of many magnetic properties including energy, Kerr, and dichroism effects. LiFeN is identified as an ultimate single-ion anisotropy system where a nearly insulating state can be produced by a spin orbital coupling alone. A very nontrivial strongly fluctuating and sign changing character of the magnetic anisotropy with electronic 3d-atomic doping is predicted theoretically. A large and highly anisotropic Kerr effect due to the interband transitions between atomic-like Fe 3d bands is found for LiFeN. A giant anisotropy of the x-ray magnetic circular dichroism for the Fe K spectrum and a very weak one for the Fe L2,3 spectra in LiFeN are also predicted.

Antropov, V. P.; Antonov, V. N.

2014-09-01

243

Complex Fuzzy Set-Valued Complex Fuzzy Measures and Their Properties  

PubMed Central

Let F*(K) be the set of all fuzzy complex numbers. In this paper some classical and measure-theoretical notions are extended to the case of complex fuzzy sets. They are fuzzy complex number-valued distance on F*(K), fuzzy complex number-valued measure on F*(K), and some related notions, such as null-additivity, pseudo-null-additivity, null-subtraction, pseudo-null-subtraction, autocontionuous from above, autocontionuous from below, and autocontinuity of the defined fuzzy complex number-valued measures. Properties of fuzzy complex number-valued measures are studied in detail. PMID:25093202

Ma, Shengquan; Li, Shenggang

2014-01-01

244

Orbital-dependent magnetic properties of molecular cluster containing high-spin Co(II) ions  

NASA Astrophysics Data System (ADS)

To shed light on magnetic properties of the magnetic exchange molecular cluster containing the constituent metal ion with unquenched orbital angular momentum, as representative examples two octahedrally coordinated high-spin Co(II)-cluster complexes were synthesized and characterized: complex (1) [Co3(Hbzp)6][ClO4]2· 2CH3OH·H2O (bzp = 2-benzoylpyridine) with a linear core Co(III)-Co(II)-Co(III) and complex (2) [Co4L(N3)4(CH3CN)4](ClO4)4·2H2O (L = Macrocyclic schiff base of tetra-2,6-pyridinedicarboxaldehyde-tetra-ethane-1,2-diamine) comprised by two nearly independent Co(II)-dimers. Following Lines' isotropic exchange approximation the magnetic interaction effective Hamiltonian was introduced, which includes the exchange interactions, the spin-orbit coupling, the low-symmetry crystal field, and the intercluster exchange interaction. On the basis of the irreducible tensor operator approach to solve Hamiltonian we have coded the software, BJMAG package, and performed the best-fit procedure for experimentally temperature variable magnetic susceptibilities for the complexes (1) and (2). The best-fit parameters were obtained as follows: ? = -126 cm-1, ? = 432 cm-1, ? = 0.96, mJ? = 2.7 cm-1 for the complex (1) and ? = -165 cm-1, ? = 960 cm-1, ? = 0.95, J? = 9 cm-1, mJ? = -0.1 cm-1 for the complex (2). To further elucidate the individual role of each interaction in the employed model, the effects of the key factors governing the magnetic properties on temperature variable magnetic susceptibilities were examined in detail. The significance of the intercluster exchange interactions at low temperatures was briefly discussed and a self-consistent molecular field to calculate the thermally average spin of the nearest neighbor in the intercluster interaction was proposed.

Wang, Fan; Zhao, Fei; Wang, Bing-Wu; Wang, Ming-Wei; Zhang, Yuan-Zhu; Wang, Wei; Gao, Song; Chen, Zhi-Da

245

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

246

Structural, dielectric and magnetic properties of Nd-doped Co 2Z-type hexaferrites  

Microsoft Academic Search

Z-type hexaferrites doped with Nd3+, Ba3?xNdxCo2Fe24O41 (x=0, 0.05, 0.10, 0.15, and 0.25), were prepared by solid-state reaction. The effect of the Nd3+ ions substitution for Ba2+ ions on the microstructure and electromagnetic properties of the samples was investigated. The results reveal that an important modification of microstructure, complex permeability, complex permittivity, and static magnetic properties can be obtained by introducing

Jijing Xu; Guijuan Ji; Haifeng Zou; Yuan Zhou; Shucai Gan

2011-01-01

247

Low-Temperature Magnetic Properties of Environmentally Relevant Iron Oxyhydroxides and Their Alteration Products  

NASA Astrophysics Data System (ADS)

Iron oxyhydroxides such as ferrihydrite or lepidocrocite are weakly magnetic mineral that are thought to be, in some environments, precursors of more magnetic phases such as magnetite or maghemite. Deciphering the alteration pathways of these minerals, and others, should allow quantified interpretations of sediment magnetic properties in terms of climate and environmental change in various natural settings. At this meeting, we will present recent low temperature magnetic properties acquired on synthetic iron oxyhydroxides. Comparison of these low-temperature data with other characterizations (e.g., HR-TEM, Mossbauer, XMCD) point to the complex nature of the magnetism of these minerals, which can no longer be considered as simple antiferromagnets. Results from alteration experiments using these minerals as starting material will also be presented. Several experimental approaches have been used for these alterations, including bio-reduction using Shewanella putrefaciens and solid-state reduction (or oxidation) by slow heating in CO/CO2 (or in air). The low-temperature magnetic properties of the resulting materials actually help in building conceptual structural/compositional models explaining the unusual low-temperature magnetic behavior of the initial iron oxyhydroxides.

Guyodo, Y. J.; Lagroix, F.; Ona-Nguema, G.; Bonville, P.

2011-12-01

248

Magnetic properties of disordered Ni3C  

NASA Astrophysics Data System (ADS)

The metastable Ni3C phase has been produced by mechanically alloying Ni and C. Ni3C particles of diameter 10 nm are produced after 90 h of mechanical alloying with no evidence of crystalline Ni in x ray or electron diffraction. Linear muffin-tin orbital band-structure calculations show that Ni3C is not expected to be ferromagnetic due to strong Ni-C hybridization in the ordered alloy; however, the introduction of even small amounts of disorder produces locally Ni-rich regions that can sustain magnetism. Mechanically alloyed Ni3C is ferromagnetic, with a room-temperature coercivity of 70 Oe and a magnetization of 0.8 emu/g at 5.5 T, although the hysteresis loop is not saturated. The theoretical prediction that interacting locally nickel-rich regions may be responsible for ferromagnetic behavior is supported by the observation of magnetically glassy behavior at low magnetic fields.

Yue, Lanping; Sabiryanov, R.; Kirkpatrick, E. M.; Leslie-Pelecky, Diandra L.

2000-10-01

249

Complex studies of properties of nanostructured silicon  

NASA Astrophysics Data System (ADS)

Nanocrystalline silicon layers ( 3â€``35nm ) have been formed upon single-crystal silicon substrates of very large area (100 cm2), multicrystalline silicon substrates and metallurgical silicon substrates by stain etching. We studied optical and structural properties of nanocrystalline silicon by photoluminescence, reflection, scanning tunnel microscopy, scanning electron microscopy, Auger electronic spectroscopy and SIMS methods. Researches of properties of nc-Si, received by a method of chemical processing, have confirmed an opportunity of creation of this multifunctional material with stable characteristics. The authors have observed the sensors systems with use of nanocrystalline silicon as a sensitive layer, which properties depend on thickness of a received layer and are controlled by parameters of technological process. On an example of the photoluminescent sensor with nc-Si layer it is shown, that such sensor can be successfully used for definition of small concentrations of toxins (pesticides phosalone 10 -8-10 -9 mol/l ), and also for specific biological pollutant, such as protein components, polysaccharides, cells used during biotechnological synthesis.

Luchenko, A. I.; Melnichenko, M. M.; Svezhentsova, K. V.; Shmyryeva, O. M.

2006-08-01

250

Electronic and magnetic properties of ultrathin rhodium nanowires  

NASA Astrophysics Data System (ADS)

The structures of ultrathin rhodium nanowires are studied using empirical molecular dynamics simulations with a genetic algorithm. Helical multishell cylindrical and pentagonal packing structures are found. The electronic and magnetic properties of the rhodium nanowires are calculated using an spd tight-binding Hamiltonian in the unrestricted Hartree-Fock approximation. The average magnetic moment and electronic density of states are obtained. Our results indicate that the electronic and magnetic properties of the rhodium nanowires depend not only on the size of the wire but also on the atomic structure. In particular, centred pentagonal and hexagonal structures can be unusually ferromagnetic.

Wang, Baolin; Wang, Guanghou; Ren, Yun; Sun, Houqian; Chen, Xiaoshuang; Zhao, Jijun

2003-04-01

251

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

252

Magnetic properties of alluvial soils polluted with heavy metals  

NASA Astrophysics Data System (ADS)

Magnetic properties of soils, reflecting mineralogy, concentration and grain-size distribution of Fe-oxides, proved to be useful tool in assessing the soil properties in terms of various environmental conditions. Measurement of soil magnetic properties presents a convenient method to investigate the natural environmental changes in soils as well as the anthropogenic pollution of soils with several risk elements. The effect of fluvial pollution with Cd, Cu, Pb and Zn on magnetic soil properties was studied on highly contaminated alluvial soils from the mining/smelting district (P?íbram; CZ) using a combination of magnetic and geochemical methods. The basic soil characteristics, the content of heavy metals, oxalate, and dithionite extractable iron were determined in selected soil samples. Soil profiles were sampled using HUMAX soil corer and the magnetic susceptibility was measured in situ, further detailed magnetic analyses of selected distinct layers were carried out. Two types of variations of magnetic properties in soil profiles were observed corresponding to indentified soil types (Fluvisols, and Gleyic Fluvisols). Significantly higher values of topsoil magnetic susceptibility compared to underlying soil are accompanied with high concentration of heavy metals. Sequential extraction analysis proved the binding of Pb, Zn and Cd in Fe and Mn oxides. Concentration and size-dependent parameters (anhysteretic and isothermal magnetization) were measured on bulk samples in terms of assessing the origin of magnetic components. The results enabled to distinguish clearly topsoil layers enhanced with heavy metals from subsoil samples. The dominance of particles with pseudo-single domain behavior in topsoil and paramagnetic/antiferromagnetic contribution in subsoil were observed. These measurements were verified with room temperature hysteresis measurement carried out on bulk samples and magnetic extracts. Thermomagnetic analysis of magnetic susceptibility measured on magnetic extracts indicated the presence of magnetite/maghemite in the uppermost layers, and strong mineralogical transformation of iron oxyhydroxides during heating. Magnetic techniques give valuable information about the soil Fe oxides, which are useful for investigation of the environmental effects in soil. Key words: magnetic methods, Fe oxides, pollution, alluvial soils.

Dlouha, S.; Petrovsky, E.; Boruvka, L.; Kapicka, A.; Grison, H.

2012-04-01

253

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

254

Angular dependence of dynamic magnetic properties and magnetization orientation distribution of thin films  

SciTech Connect

The angular dependence of dynamic magnetic properties of FeTaN thin films fabricated by rf sputtering deposition technique onto various substrates was investigated in conjunction with static magnetic characteristics. Thin films grown onto rigid and thick substrates show a well-defined uniaxial anisotropy and strongly distinct permeability spectra measured at various orientations while those samples grown onto flexible and thin substrates exhibit a less well-defined uniaxial anisotropy and much less different permeability spectra. The resultant variation of the magnetization orientation distributions obtained by retrieving the magnetization values from the permeability curves for different substrates can be interpreted in terms of the magnetic anisotropy dispersion due to stress.

Hung, Le Thanh; Ong, C. K. [Department of Physics, Center for Superconducting and Magnetic Materials, National University of Singapore, 2 Science Drive3, Singapore 117542 (Singapore); Phuoc, Nguyen N. [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 2, Singapore 117411 (Singapore)

2009-09-15

255

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

256

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

257

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

258

Trajectories of Unsaturated Magnetic Properties on Day Plots  

NASA Astrophysics Data System (ADS)

The Day plot was initially developed to delineate the domain states of magnetite grains based on saturated magnetic properties and has since become a standard method in rock magnetic studies. Because most natural magnetic systems are "dirty", meaning they may contain a combination of non-stoiciometric magnetite, partially oxidized magnetite, other magnetic minerals, and/or complicated grain-size distributions, Day plots can be difficult to interpret and may not even be applicable to these systems. Furthermore there is a tendency for many natural systems to have similar magnetic parameters, and thus fall in the same field of a Day plot, even though they have distinctly different magnetic compositions and grain sizes. We aim to overcome some of these limitations by using the trajectories of unsaturated magnetic properties in a Day plot. Below saturation, rock magnetic parameters are highly variable with respect to the maximum applied field, Bmax, though surprisingly little work has been done to utilize this variability as a rock magnetic tool. The magnetic moment, the magnetic remanance, the coercivity, and the coercvity of remanance were measured as a function of Bmax, from 10 mT (unsaturated) to 1400 mT (saturated for magnetite). These four parameters were then plotted on a Day plot, which gave a trajectory of points as a function of Bmax, instead of a single point. These trajectories are useful for discriminating grain-size distributions and compositions as illustrated for several pure and mixed synthetic samples of magnetite and hematite, all diluted in vacuum grease to minimize interactions. The technique was also applied to NIST standards 1633 (Fly Ash), 1649 (Urban Dust), and 1650 (Diesel PM) and revealed that all three samples contained at least two magnetic components, each of which has different coercivities and grain-size distributions. This information would not have been discernable with most conventional magnetic measurements.

Roth, A. L.; Acton, G.; Kenneth, V. L.

2004-12-01

259

Magnetic and Transport Properties of Mn-ion implanted Si  

NASA Astrophysics Data System (ADS)

We investigate the magnetic and transport properties of Mn-ion implanted Si. Both temperature dependent and field dependent measurements of the samples using a SQUID magnometer reveal ferromagnetic properties at room temperature. Magnetotransport measurements show a large positive magnetoresistance up to 4.5 T with no signs of saturation.

Preisler, V.; Ogawa, M.; Han, X.; Wang, K. L.

2010-01-01

260

MAGNETIC PROPERTIES OF AN ANTIFERROMAGNETIC TWO-SINGLET SYSTEM.  

E-print Network

27 MAGNETIC PROPERTIES OF AN ANTIFERROMAGNETIC TWO-SINGLET SYSTEM. II. RESULTS ON TERBIUM ALUMINUM. 2014 Les propriétés métamagnétiques du grenat de terbium et d'aluminium (TbAlG), qui est un. Abstract. 2014 The metamagnetic properties of terbium aluminum garnet, which is a six

Paris-Sud XI, Université de

261

Complex inductance, excess noise, and surface magnetism in dc SQUIDs.  

PubMed

We have characterized the complex inductance of dc SQUIDs cooled to millikelvin temperatures. The SQUID inductance displays a rich, history-dependent structure as a function of temperature, with fluctuations of order 1 fH. At a fixed temperature, the SQUID inductance fluctuates with a 1/f power spectrum; the inductance noise is highly correlated with the conventional 1/f flux noise. The data are interpreted in terms of the reconfiguration of clusters of surface spins, with correlated fluctuations of effective magnetic moments and relaxation times. PMID:19792393

Sendelbach, S; Hover, D; Mück, M; McDermott, R

2009-09-11

262

Magnetic Properties of Prussian Blue Analog Films  

NASA Astrophysics Data System (ADS)

The study of magnetization in thin film geometries of Prussian blue analogs, RbjM^'k [M(CN)6]l.nH2O, has shown emergent phenomena compared to bulk-like precursors. One example is the photoinduced decrease in magnetization for M^'=Co, M=Fe materials when the plane of the films is perpendicular to the applied magnetic field, as opposed to the usual increase in magnetization observed in the powder material [1,2]. By studying additional compounds without the photoinduced bistability, such as the M^'=Ni(S=1), M=Cr(S=3/2) ferromagnet with a TC ˜ 75 K and the M^'=Cu(S=1/2), M=Fe(S=1/2) ferromagnet with a TC ˜ 20 K, we have gained insight into the magnetic anisotropy present in the general class of Prussian blue analog thin films. Samples have been characterized by SQUID magnetometry, ESR, AFM, SEM, EDS and FT-IR. [4pt] [1] J.-H. Park, et al., Appl. Phys. Lett. 85, 3797 (2004). [2] F. A. Frye et al., Chem. Mater. 20, 5706 (2008).

Pajerowski, D. M.; Meisel, M. W.; Knowles, E. S.; Andrus, M. J.; Gardner, J. E.; Talham, D. R.; Datta, S.; Ozarowski, A.; Hill, S.

2010-03-01

263

Magnetic properties and microstructure of Nd-Fe-B sintered magnets with DyHx addition  

NASA Astrophysics Data System (ADS)

The effects of DyHx addition on magnetic properties and microstructure of Nd-Fe-B sintered magnets were investigated. In order to obtain the best magnetic properties, the effects of sintering temperature and annealing time on magnetic properties were also investigated. The results shown that the addition of DyHx can affect the microstructure, increase the intrinsic coercivity (Hcj), and improve the thermal stability of sintered Nd-Fe-B magnets. The remanence (Br) and Hcj showed different variation trends as sintering temperature changes. Within a reasonable range, sintering at higher temperature can get higher Br but lower Hcj. The Hcj was further increased by heat treatment and annealing time was extended.

Liu, Y. H.; Guo, S.; Liu, X. M.; Lee, D.; Yan, A. R.

2012-04-01

264

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

265

Magnetic properties of rare-earth metallofullerenes  

SciTech Connect

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

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

1995-02-16

266

Magnetic properties of Ni/Tb multilayers  

NASA Astrophysics Data System (ADS)

Thin multilayer films of alternating ultrathin Ni and Tb layers ( tNi=5…80 Å, tTb=30 Å) were sputter-deposited at room temperature and magnetically characterised by temperature-dependent SQUID measurements and torque measurements at T=300 K. Despite of the multilayer structure of all samples and a transition of the microstructure of the Ni layers the measured spontaneous magnetic moment of all samples is explained by a band filling model in analogy to amorphous and crystalline NiRE alloys. The magnetic Ni moment is quenched by a successive filling of its 3d minority band by the 5d, 6 s conduction electrons of Tb. As long as the Ni moment is not zero an antiferromagnetic Ni-Tb coupling and a perpendicular anisotropy component appears. The corresponding results of structural investigations are given elsewhere J. Magn. Magn. Mater. 248 (2002) 181.

Schmidt, Thomas; Hoffmann, Horst

2003-02-01

267

Polymer nanocomposites exhibiting magnetically tunable microwave properties  

NASA Astrophysics Data System (ADS)

Polymer nanocomposites (PNCs) have been synthesized using Rogers polymer and CoFe2O4 nanoparticles (CFO NPs). X-ray diffraction (XRD) confirms the inverse spinel crystal structure of CFO NPs and transmission electron microscopy (TEM) images show the uniform dispersion of nanoparticles (10 nm ± 1) into the polymer matrix. Magnetic measurements indicate superparamagnetic response near room temperature for all PNCs. A blocking temperature TB ~ 298 K was observed and does not vary for different loading fractions of CFO NPs for the PNCs. The saturation magnetization (Ms) was found to be 11 emu g - 1 for 30 wt% CFO, increasing to 32 emu g - 1 for the 80 wt% CFO loaded PNC. A large value of coercivity (Hc = 19 kOe) is also observed at 10 K and is not affected by varying CFO loading. Microwave measurements show significant absorption in the 80 wt% CFO loading PNC and the quality factor shows a strong enhancement with applied magnetic field.

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

2011-04-01

268

Magnetic properties of Nd-Fe-B\\/alpha-Fe multi-layered thick film magnets  

Microsoft Academic Search

Nd-Fe-B\\/alpha-Fe multi-layered nanocomposite film-magnets were prepared from a rotating Nd2.6Fe14B\\/alpha-Fe composite target by the pulse laser deposition method with a Nd-YAG laser (lambda=355 nm). The prepared film-magnets were composed of approximately 800 layers with the thickness of about several tens nanometre, and exhibited hard magnetic properties after annealing. The laser power for the ablation of the target was varied between

H. Fukunaga; H. Nakayama; T. Kamikawatoko; T. Yanai; M. Nakano; F. Yamashita; S. Ohta; M. Itakura; M. Nishida

2011-01-01

269

High temperature structural and magnetic properties of cobalt nanorods  

SciTech Connect

We present in this paper the structural and magnetic properties of high aspect ratio Co nanoparticles ({approx}10) at high temperatures (up to 623 K) using in-situ X ray diffraction (XRD) and SQUID characterizations. We show that the anisotropic shapes, the structural and texture properties are preserved up to 500 K. The coercivity can be modelled by {mu}{sub 0}H{sub C}=2(K{sub MC}+K{sub shape})/M{sub S} with K{sub MC} the magnetocrystalline anisotropy constant, K{sub shape} the shape anisotropy constant and M{sub S} the saturation magnetization. H{sub C} decreases linearly when the temperature is increased due to the loss of the Co magnetocrystalline anisotropy contribution. At 500 K, 50% of the room temperature coercivity is preserved corresponding to the shape anisotropy contribution only. We show that the coercivity drop is reversible in the range 300-500 K in good agreement with the absence of particle alteration. Above 525 K, the magnetic properties are irreversibly altered either by sintering or by oxidation. - Graphical abstract: We present in this paper the structural and magnetic properties of high aspect ratio Co nanorods ({approx}10) at high temperatures (up to 623 K) using in-situ X-ray diffraction and SQUID characterizations. We show that the anisotropic shapes, the structural and texture properties are preserved up to 500 K. Above 525 K, the magnetic properties are irreversibly altered either by sintering or by oxidation. Highlights: Black-Right-Pointing-Pointer Ferromagnetic Co nanorods are prepared using the polyol process. Black-Right-Pointing-Pointer The structural and texture properties of the Co nanorods are preserved up to 500 K. Black-Right-Pointing-Pointer The magnetic properties of the Co nanorods are irreversibly altered above 525 K.

Ait Atmane, Kahina [Univ. Paris Diderot, Sorbonne Paris Cite, ITODYS, UMR CNRS 7086, 15 rue J.-A. de Baief, 75205 Paris Cedex 13 (France); Zighem, Fatih [Laboratoire Leon Brillouin, CEA CNRS UMR 12, IRAMIS, CEA-Saclay, 91191 Gif sur Yvette (France); Soumare, Yaghoub [Univ. Paris Diderot, Sorbonne Paris Cite, ITODYS, UMR CNRS 7086, 15 rue J.-A. de Baief, 75205 Paris Cedex 13 (France); Ibrahim, Mona; Boubekri, Rym [Universite de Toulouse, LPCNO, INSA CNRS UMR 5215, 135 av. de Rangueil, 31077 Toulouse Cedex 4 (France); Maurer, Thomas [Laboratoire Leon Brillouin, CEA CNRS UMR 12, IRAMIS, CEA-Saclay, 91191 Gif sur Yvette (France); Margueritat, Jeremie [Univ. Paris Diderot, Sorbonne Paris Cite, ITODYS, UMR CNRS 7086, 15 rue J.-A. de Baief, 75205 Paris Cedex 13 (France); Piquemal, Jean-Yves, E-mail: jean-yves.piquemal@univ-paris-diderot.fr [Univ. Paris Diderot, Sorbonne Paris Cite, ITODYS, UMR CNRS 7086, 15 rue J.-A. de Baief, 75205 Paris Cedex 13 (France); Ott, Frederic; Chaboussant, Gregory [Laboratoire Leon Brillouin, CEA CNRS UMR 12, IRAMIS, CEA-Saclay, 91191 Gif sur Yvette (France); Schoenstein, Frederic; Jouini, Noureddine [LSPM, CNRS UPR 9001, Universite Paris XIII, Institut Galilee, 99 av. J.-B. Clement, 93430 Villetaneuse (France); Viau, Guillaume, E-mail: gviau@insa-toulouse.fr [Universite de Toulouse, LPCNO, INSA CNRS UMR 5215, 135 av. de Rangueil, 31077 Toulouse Cedex 4 (France)

2013-01-15

270

A high-temperature molecular ferroelectric Zn/Dy complex exhibiting single-ion-magnet behavior and lanthanide luminescence.  

PubMed

Multifunctional molecular ferroelectrics are exciting materials synthesized using molecular chemistry concepts, which may combine a spontaneous electrical polarization, switched upon applying an electric field, with another physical property. A high-temperature ferroelectric material is presented that is based on a chiral Zn(2+) /Dy(3+) complex exhibiting Dy(3+) luminescence, optical activity, and magnetism. We investigate the correlations between the electric polarization and the crystal structure as well as between the low-temperature magnetic slow relaxation and the optical properties. PMID:25556721

Long, Jérôme; Rouquette, Jérôme; Thibaud, Jean-Marc; Ferreira, Rute A S; Carlos, Luís D; Donnadieu, Bruno; Vieru, Veaceslav; Chibotaru, Liviu F; Konczewicz, Leszek; Haines, Julien; Guari, Yannick; Larionova, Joulia

2015-02-01

271

Magnetic Properties of Radiation Damage in Pu  

SciTech Connect

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

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

2004-10-27

272

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

273

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

PubMed Central

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

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

2013-01-01

274

Maria Goeppert-Mayer Award Talk: Novel Magnetism and Transport in Complex Oxide Thin Films, Multilayers and Nanostructures  

NASA Astrophysics Data System (ADS)

In epitaxial complex oxide systems, epitaxial strain, cation substitution and nanofabrication are just some ways in which their magnetic, electronic and optical properties may be tuned. In addition, their surfaces and interfaces provide a rich playground for the exploration of novel magnetic properties not found in the bulk constituents and the development of functional interfaces to be incorporated into technological applications. We have probed magnetism in complex oxide materials through studies of epitaxial oxide thin films, nanostructures and junction devices. With our ability to control oxide film growth as well as our expertise in nanofabrication, we have been able to study the effects of surfaces and interfaces on magnetism in ultra-thin magnetic oxide films and magnetic oxide nanostructures. For example, we have found that the nature of local magnetic structure in submicron islands of colossal magnetoresistance (CMR) material reveals the importance of shape anisotropy as well as magnetostriction in determining the micromagnetics in such small CMR structures. We have also studied epitaxial oxide trilayer junctions composed of magnetite (Fe3O4) and doped manganite (La0.7Sr0.3MnO3) in which we have confirmed the theoretically predicted negative spin polarization of Fe3O4. Transport through the barrier can be understood in terms of hopping transport through localized states that preserves electron spin information.

Suzuki, Yuri

2005-03-01

275

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

276

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

277

Adsorption-induced magnetic properties and metallic behavior of graphene  

SciTech Connect

Magnetic properties and electronic structures of graphene with Cl, S, and P adsorption have been investigated using ab initio calculations. The adsorption of Cl leads to Fermi level shifting to valence band, which results in metallic graphene. A band gap of 0.6 eV emerges in a S-absorbed graphene, leading to the semiconducting graphene. The unpaired electrons in the absorbed P atom is polarized and thus, exhibits a magnetic moment of 0.86 ?B, while no magnetic moment has been observed after Cl and S adsorption. This demonstrates that the magnetic properties and conductive behavior of graphene can be modified via atom adsorption. Specially, P-absorbed graphene may be useful for spintronic applications, such as tunneling magnetoresistance.

Zhou, Yungang; Zu, Xiaotao T.; Gao, Fei; Lv, H. F.; Xiao, Haiyan J.

2009-09-21

278

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

279

Magnetic and Transport Properties of Lanthanum Based CMR Systems  

NASA Astrophysics Data System (ADS)

The magnetic and transport properties of bulk polycrystalline samples of Ca doped manganite perovskites have been studied. The material properties were characterized using SEM, EDX and XRD. Magnetization measurements were performed using a SQUID magnetometer in order to determine Curie temperature and moment per Mn ion. The temperature and field (H) dependence of the electrical resistance, R(T,H) and Hall effect were measured by standard ac four and six probe techniques in magnetic fields up to 17 T*. Typical zero field I-M transition peaks near 275 K in R(T) and negative dR/dH at high fields were observed. However, for H < 0.2 T, positive MR is seen. The results of these measurements, including low field positive magnetoresistance, will be reported. *Performed at the National High Magnetic Field Lab (NHMFL) FSU, Tallahassee, FL

Estrada, Javier; Bleiweiss, Michael; Saygi, Salih; Datta, Timir; Yin, Ming; Palm, Eric; Brandt, Bruce; Iqbal, Zafar

2001-03-01

280

Novel microwave properties and "memory effect" in magnetic nanowire array  

NASA Astrophysics Data System (ADS)

Ferromagnetic nanowire arrays embedded in insulating matrices have attracted great attention in recent years for their rich physics and potential as sensor and microwave applications. Magnetic nanowires made of 3d transitional metals or their alloys have the advantages of high saturation magnetizations, limited eddy current loss, and guaranteed microwave penetration due to nanometer size. The nanowire arrays can also have high ferromagnetic resonance (FMR) frequencies due to shape anisotropy. In this work, the following new phenomena of magnetic nanowire arrays are demonstrated and explained with a theoretical model. (1) A simple theoretical analysis indicates that high permeability is possible in nanowire arrays with the magnetocrystalline anisotropy comparable to the demagnetization energy and its easy axis perpendicular to the nanowire. With proper conditions, we have fabricated Co nanowire arrays with a crystalline easy axis perpendicular to the nanowire. For Co nanowire arrays with certain geometries, high permeability and low losses have been achieved. (2) Magnetic materials with tunable FMR are highly desirable in microwave devices. We demonstrate that the natural FMR of Ni90Fe10 nanowire array can be tuned continuously from 8.2 to 11.7 GHz by choosing different remanent state. Theoretical model based on dipolar interaction among nanowires has been developed to explain the observed phenomena. A double FMR feature caused by dipolar interaction in magnetic nanowire array was predicted and verified in Co nanowires. (3) A memory effect has also been demonstrated in magnetic nanowire arrays. The magnetic nanowire array has the ability to record the maximum magnetic field that the array has been exposed to after the field has been turned off. The origin of the memory effect is the strong magnetic dipole interaction among the nanowires. Based on the memory effect, a novel and extremely low cost EMP detection scheme is proposed. It has the potential to measure magnetic field pulses as high as a few hundred Oe without breaking down. In the proposed EMP detector, a magnetic field sensor is required to measure the surface field of the magnetic nanowire array. MgO based magnetic tunnel junction (MTJ) is one type of magnetic field sensors. We investigated the evolution of the magnetic transport properties as a function of short annealing time in MgO based MTJ junctions. It is found that the desired sensor behavior appears in samples annealed for 17 minutes. The result can be well fitted by using the superparamagnetism theory, suggesting the formation of superparamagnetic particles in the free layer during the high temperature annealing. The control of MTJ properties with annealing time is desirable in magnetic field sensor productions.

Kou, Xiaoming

2011-12-01

281

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

282

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

283

Luminescent Cyclometalated Platinum and Palladium Complexes with Novel Photophysical Properties  

NASA Astrophysics Data System (ADS)

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

Turner, Eric

284

Polymer nanocomposites exhibiting magnetically tunable microwave properties.  

PubMed

Polymer nanocomposites (PNCs) have been synthesized using Rogers polymer and CoFe?O? nanoparticles (CFO NPs). X-ray diffraction (XRD) confirms the inverse spinel crystal structure of CFO NPs and transmission electron microscopy (TEM) images show the uniform dispersion of nanoparticles (10 nm ± 1) into the polymer matrix. Magnetic measurements indicate superparamagnetic response near room temperature for all PNCs. A blocking temperature T(B)~298 K was observed and does not vary for different loading fractions of CFO NPs for the PNCs. The saturation magnetization (M(s)) was found to be 11 emu g?¹ for 30 wt% CFO, increasing to 32 emu g?¹ for the 80 wt% CFO loaded PNC. A large value of coercivity (H(c) = 19 kOe) is also observed at 10 K and is not affected by varying CFO loading. Microwave measurements show significant absorption in the 80 wt% CFO loading PNC and the quality factor shows a strong enhancement with applied magnetic field. PMID:21343635

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

2011-04-01

285

Preparation and property of polyurethane/nanosilver complex fibers  

NASA Astrophysics Data System (ADS)

Utilizing terminal reactive groups in polyurethane, nanometer silvers were reduced in situ. The formation mechanism of nanosilver in PU was under preliminary discussion. UV-vis spectroscopy and TEM analysis were used to monitor reduction process; and the PU/nanosilver complex fibers were produced by dry spinning, which were characterized by X-ray diffraction, Fourier transform infrared spectra, thermogravimetric analysis, differential scanning calorimetry and so on. The influence of nanosilver on the thermal, mechanical and antimicrobial properties of PU was studied. It is inferred that 0.030% Ag should be a proper concentration for the PU/nanosilver complex fibers with favorable mechanical properties and highly effective antibacterial activities.

Qu, Rongjun; Gao, Jingjing; Tang, Bo; Ma, Qianli; Qu, Baohan; Sun, Changmei

2014-03-01

286

Anisotropic magnetic properties of dysprosium iron garnet (DyIG)  

Microsoft Academic Search

The magnetic properties of dysprosium iron garnet (DyIG) have been studied by performing high resolution powder neutron diffraction experiments and high dc fields magnetizations on single crystals. Among all the reflections (hkl) indexed in the nuclear cubic space group (CSG) Ia bar 3 d with h+k+l=2n and k=[000], the superstructure lines (hkl)* forbidden by the symmetry (222)* and (622)* are

M. Lahoubi; W. Younsi; M.-L. Soltani; B. Ouladdiaf

2010-01-01

287

Glass-ceramic containing lithium ferrite: Magnetic and structural properties  

Microsoft Academic Search

The magnetic and microstructural properties of Fe2O3?Li2O?B2O3 glass strips (with dimensions 50 mm long, 6 mm wide and about 30–100 ?m thick), which were subjected to various heat treatments in order to induce a variable amount of magnetic crystalline phase (LiFe5O8 crystals) within the glassy matrix, were investigated. The irreversible structural changes produced by the heat treatments between 200 and

N. Rezlescu; E. Rezlescu; I. Ciobotaru; M. L. Craus; P. D. Popa

1998-01-01

288

Magnetic and structural properties of YCo5-xCux  

Microsoft Academic Search

The influence of the addition of Cu in the YCo5 matrix, YCo5-xCux with 0⩽x⩽3, on magnetic and structural properties was investigated. With increasing Cu concentration a decreasing saturation magnetization, anisotropy energy and Curie temperature were obtained. Contrary to the results obtained in Sm(Co,Cu) 5 alloys neither an enhancement of the coercive force nor a dH\\/dt dependence of the coercive force

J. C. Tellez-Blanco; R. Grossinger; R. Sato Turtelli; E. Estevez-Rams

2000-01-01

289

Effect of pressure on the magnetic properties of lanthanum manganite  

SciTech Connect

The crystalline structure of pure lanthanum manganite under external hydrostatic pressure has been studied. The behavior of magnetic properties and nuclear magnetic resonance (NMR) spectra under these conditions is theoretically predicted. It is shown that an increase in the Neel temperature with pressure is not only caused by the general contraction of the crystal, but is also related to certain peculiarities in the baric behavior of the orbital structure.

Gonchar', L. E., E-mail: Lyudmila.Gonchar@usu.ru; Leskova, Yu. V.; Nikiforov, A. E. [Ural State University (Russian Federation); Kozlenko, D. P. [Joint Institute for Nuclear Research (Russian Federation)

2010-08-15

290

Geometric properties of the magnetic Laplacian on the Euclidean 4-space  

SciTech Connect

When the four-dimensional Euclidean space is endowed with a covariant derivative that is either self-dual or antiself-dual and of constant curvature, the corresponding magnetic Laplacian is closely related to the sub-Laplacian of the quaternionic Heisenberg group. Some geometric properties of this operator are studied. In particular, it is proved that there exists a canonical orthogonal complex structure which provides a factorization in the sense of Schroedinger.

Kazmierowski, Dominique [Universite Lille I - Sciences et Technologies, 59655 Villeneuve d'Ascq Cedex (France); Zinoun, Azzouz [Laboratoire de Physique des Lasers, Atomes et Molecules, Unite Mixte de Recherche de l'Universite de Lille 1 et du CNRS - UMR 8523, Universite Lille I - Sciences et Technologies, 59655 Villeneuve d'Ascq Cedex (France); Intissar, Ahmed [Departement de Mathematiques, Faculte des Sciences de Rabat, BP 1014 (Morocco)

2010-12-15

291

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

292

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

PubMed Central

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

2013-01-01

293

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

294

Magnetic properties of NdFeB-coated rubberwood composites  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

295

Magnetic properties of a long, thin-walled ferromagnetic nanotube  

NASA Astrophysics Data System (ADS)

We consider magnetic properties of a long, thin-walled ferromagnetic nanotube. We assume that the tube consists of isotropic homogeneous magnet whose spins interact via the exchange energy, the dipole-dipole interaction energy, and also interact with an external field via Zeeman energy. Possible stable states are the parallel state with the magnetization along the axis of the tube, and the vortex state with the magnetization along azimuthal direction. For a given material, which of them has lower energy depends on the value ?=R2d/(L?x2), where R is the radius of the tube, d is its thickness, L is its length and ?x is an intrinsic scale of length characterizing the ratio of exchange and dipolar interaction. At ?<1, the parallel state wins, otherwise the vortex state is stable. A domain wall in the middle of the tube is always energy unfavorable, but it can exist as a metastable structure. Near the ends of a tube magnetized parallel to the axis a half-domain structure transforming gradually the parallel magnetization to a vortex just at the edge of the tube is energy favorable. We also consider the equilibrium magnetization textures in an external magnetic field either parallel or perpendicular to the tube. Finally, magnetic field produced by a nanotube and an array of tubes is analyzed.

Sun, Chen; Pokrovsky, Valery L.

2014-04-01

296

Size-dependent magnetic properties of single-crystalline multiferroic BiFeO3 nanoparticles.  

PubMed

As-prepared, single-crystalline bismuth ferrite nanoparticles show strong size-dependent magnetic properties that correlate with: (a) increased suppression of the known spiral spin structure (period length of approximately 62 nm) with decreasing nanoparticle size and (b) uncompensated spins and strain anisotropies at the surface. Zero-field-cooled and field-cooled magnetization curves exhibit spin-glass freezing behavior due to a complex interplay between finite size effects, interparticle interactions, and a random distribution of anisotropy axes in our nanoparticle assemblies. PMID:17324002

Park, Tae-Jin; Papaefthymiou, Georgia C; Viescas, Arthur J; Moodenbaugh, Arnold R; Wong, Stanislaus S

2007-03-01

297

Magnetic properties of R2Fe3O7 (R=Yb and Lu)  

NASA Astrophysics Data System (ADS)

We have investigated the magnetic properties of R2Fe3O7 (R=Yb and Lu), which belongs to the homologous family of electronic ferroelectric RFe2O4. Magnetization measurements show ferrimagnetic ordering at the Néel temperature (TN) of ~270 K, which is slightly higher than that of RFe2O4 (TN~230-250 K). Observation of spin glass and exchange bias shows a coexistence of ferromagnetic and antiferromagnetic interactions, similarly to RFe2O4. This situation gives rise to a complex magnetic change and a broad peak of magnetic entropy change. Some characteristics, such as refrigeration temperatures higher than in RFe2O4, seem to offer a possibility of this system to applications.

Yoshii, K.; Ikeda, N.; Fukuyama, R.; Nagata, T.; Kambe, T.; Yoneda, Y.; Fukuda, T.; Mori, S.

2013-11-01

298

Magnetic tunnel structures: Transport properties controlled by bias, magnetic field, and microwave and optical radiation  

NASA Astrophysics Data System (ADS)

Different phenomena that give rise to a spin-polarized current in some systems with magnetic tunnel junctions are considered. In a manganite-based magnetic tunnel structure in CIP geometry, the effect of current-channel switching was observed, which causes bias-driven magnetoresistance, rf rectification, and the photoelectric effect. The second system under study, ferromagnetic/insulator/semiconductor, exhibits the features of the transport properties in CIP geometry that are also related to the current-channel switching effect. The described properties can be controlled by a bias, a magnetic field, and optical radiation. At last, the third system under consideration is a cooperative assembly of magnetic tunnel junctions. This system exhibits tunnel magnetoresistance and the magnetic-field-driven microwave detection effect.

Volkov, N. V.; Eremin, E. V.; Tarasov, A. S.; Rautskii, M. V.; Varnakov, S. N.; Ovchinnikov, S. G.; Patrin, G. S.

2012-10-01

299

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

300

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

E-print Network

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

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

2014-09-24

301

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

PubMed

Ferrogels and magnetic elastomers feature mechanical properties that can be reversibly tuned from outside through magnetic fields. Here we concentrate on the question of how their dynamic response can be adjusted. The influence of three factors on the dynamic behavior is demonstrated using appropriate minimal models: first, the orientational memory imprinted into one class of the materials during their synthesis; second, the structural arrangement of the magnetic particles in the materials; and third, the strength of an external magnetic field. To illustrate the latter point, structural data are extracted from a real experimental sample and analyzed. Understanding how internal structural properties and external influences impact the dominant dynamical properties helps to design materials that optimize the requested behavior. PMID:25375498

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

2014-10-01

302

Magnetic properties of Ni-implanted ITO thin films  

NASA Astrophysics Data System (ADS)

The magnetic properties of Ni-implanted ITO thin films have been investigated by ferromagnetic resonance (FMR) technique and vibrating sample magnetometry (VSM) techniques. Commercially available ITO thin films on fused silica substrates have been implanted with different fluences of Ni+ ions with energy of 40 keV and ion current density of 8 ?A/cm2 at room temperature. The samples with three doses of 0.5×1017, 1.0×1017 and 1.5×1017 ions/cm2 have been studied. Room temperature ferromagnetism has been observed in the nickel-implanted ITO samples with fluences of 1.0×1017 and 1.5×1017 ions/cm2. The magnetic properties of the samples have been explained by the formation of Ni-nanoparticles in the implanted surface layer of the ITO films. Although the formation of a diluted magnetic oxide phase cannot be ruled out entirely, the analysis of our FMR and VSM data reveals that the metallic Ni nanoparticles, formed during high-dose implantation process, have major contribution to the magnetic properties of the Ni-implanted ITO thin films. The sizes of the Ni-nanoparticles have been calculated from the blocking temperatures obtained by the VSM measurements. The filling factor of the Ni ferromagnetic phase in the granular magnetic layer has also been estimated by the effective magnetization approach applied to the FMR results.

Ay, F.; Akta?, B.; Khaibullin, R. I.; Nuzhdin, V. I.; Rameev, B. Z.

2015-02-01

303

Single crystal Processing and magnetic properties of gadolinium nickel  

SciTech Connect

GdNi is a rare earth intermetallic material that exhibits very interesting magnetic properties. Spontaneous magnetostriction occurs in GdNi at T{sub C}, on the order of 8000ppm strain along the c-axis and only until very recently the mechanism causing this giant magnetostriction was not understood. In order to learn more about the electronic and magnetic structure of GdNi, single crystals are required for anisotropic magnetic property measurements. Single crystal processing is quite challenging for GdNi though since the rare-earth transition-metal composition yields a very reactive intermetallic compound. Many crystal growth methods are pursued in this study including crucible free methods, precipitation growths, and specially developed Bridgman crucibles. A plasma-sprayed Gd{sub 2}O{sub 3} W-backed Bridgman crucible was found to be the best means of GdNi single crystal processing. With a source of high-quality single crystals, many magnetization measurements were collected to reveal the magnetic structure of GdNi. Heat capacity and the magnetocaloric effect are also measured on a single crystal sample. The result is a thorough report on high quality single crystal processing and the magnetic properties of GdNi.

Shreve, Andrew John [Ames Laboratory

2012-11-02

304

Magnetic Nanoparticles: Surface Effects and Properties Related to Biomedicine Applications  

PubMed Central

Due to finite size effects, such as the high surface-to-volume ratio and different crystal structures, magnetic nanoparticles are found to exhibit interesting and considerably different magnetic properties than those found in their corresponding bulk materials. These nanoparticles can be synthesized in several ways (e.g., chemical and physical) with controllable sizes enabling their comparison to biological organisms from cells (10–100 ?m), viruses, genes, down to proteins (3–50 nm). The optimization of the nanoparticles’ size, size distribution, agglomeration, coating, and shapes along with their unique magnetic properties prompted the application of nanoparticles of this type in diverse fields. Biomedicine is one of these fields where intensive research is currently being conducted. In this review, we will discuss the magnetic properties of nanoparticles which are directly related to their applications in biomedicine. We will focus mainly on surface effects and ferrite nanoparticles, and on one diagnostic application of magnetic nanoparticles as magnetic resonance imaging contrast agents. PMID:24232575

Issa, Bashar; Obaidat, Ihab M.; Albiss, Borhan A.; Haik, Yousef

2013-01-01

305

Dust properties and magnetic field geometry towards LDN 1570  

NASA Astrophysics Data System (ADS)

We have performed both optical linear polarimetric and photometric observations of an isolated dark globule LDN 1570 aim to study the dust polarizing and extinction properties and to map the magnetic field geometry so as to understand not only the importance of magnetic fields in formation and evolution of clouds but also the correlation of the inferred magnetic field structure with the cloud structure and its dynamics. Dust size indicators (R V and ? max ) reveal for the presence of slightly bigger dust grains towards the cloud region. The inferred magnetic field geometry, which closely follows the cloud structure revealed by Herschel images, suggest that the cloud could have been formed due to converging material flows along the magnetic field lines.

Eswaraiah, C.; Maheswar, G.; Pandey, A. K.

2015-03-01

306

Study of magnetic properties of a cryogenic temperature sensor diode  

NASA Astrophysics Data System (ADS)

The magnetic properties of a cryogenic silicon diode temperature sensor (Lake Shore) are studied in the temperature range 5-255 K using a superconducting quantum interference device magnetometer. The M vs H curve at 5 and 250 K showed practically negligible magnetic hysteresis. The magnetization in a field of 100 Oe is found to be temperature independent to within 10% in the temperature range 5-255 K. The observed magnetization comes mainly from the packaging materials which includes ferromagnetic Kovar leads and nickel plating. We suggest a change of the construction materials. Our measurements show that, the existing diodes, if used in close proximity to the sample, in magnetization measurements, can be conveniently used only after background calibration.

Ota, S. B.; Mishra, P. K.; Sahni, V. C.; Singh, M. R.; Bascuñán, Juan

2000-04-01

307

Studies of magnetic properties and HFEPR of octanuclear manganese single-molecule magnets.  

PubMed

A new octanuclear manganese cluster [Mn(8)(Hpmide)(4)O(4)(EtCOO)(6)](ClO(4))(2) (1) is achieved by employing Hpmide as the ligand, and this paper examines the synthesis, X-ray structure, high-field electron paramagnetic resonance (HFEPR), magnetization hysteresis loops and magnetic susceptibilities. Complex 1 was prepared by two different methods, and hence, was crystallized in two space groups: P3(2)21 for 1a and P3(1)21 for 1b. Each molecule possesses four Mn(II) and four Mn(III) ions. The metal-oxo framework of complex 1 consists of three face-sharing cubes with manganese ions on alternate corners. The four Mn(III) cations have their Jahn-Teller elongation axes roughly parallel to the c axis of the crystal lattice. The dc magnetic susceptibility measurements reveal a spin-frustration effect in this compound. The ac magnetic susceptibilities, as well as the magnetization hysteresis measurements, clearly establish that complex 1a is a single-molecule-magnet (SMM) with a kinetic energy barrier (10.4 cm(-1)) for spin reversal. HFEPR further confirms that complex 1a is a new SMM with a magnetoanisotropy and quantized energy levels. However, interpretation of the complete set of measurements in terms of a well defined spin ground state is not possible due to the spin frustration. PMID:20886147

Wu, Che-Chih; Datta, Saiti; Wernsdorfer, Wolfgang; Lee, Gene-Hsian; Hill, Stephen; Yang, En-Che

2010-11-14

308

Magnetic Properties of Cd Substituted Ni-Cu Ferrites  

NASA Astrophysics Data System (ADS)

Cadmium substituted Ni-Cu Ferrites with the general formula Ni0.95-xCdxCu0.05Fe2O4 (x = 0.1, 0.2 and 0.3) were prepared by the standard double sintering ceramic method. The existences of single phase formation with crystalline size of 25-38 nm were confirmed from XRD measurements. The magnetic properties such as saturation magnetization (Ms) and Magnetic moment (?B) were studied by VSM analysis. The existence of multidomain (MD) particles in the samples was revealed from the small values of Mr/Ms.

Belavi, P. B.; Chavan, G. N.; Bammannavar, B. K.; Naik, L. R.; Kotnala, R. K.

2011-07-01

309

Magnetic properties of a single transverse Ising ferrimagnetic nanoparticle  

NASA Astrophysics Data System (ADS)

Using the effective field theory with a probability distribution technique that accounts for the self-spin correlation function, the thermal and the magnetic properties of a single Ising nanoparticle consisting of a ferromagnetic core, a ferromagnetic surface shell and a ferrimagnetic interface coupling are examined. The effect of the transverse field in the surface shell, the exchange interactions between core/shell and in surface shell on the free energy, thermal magnetization, specific heat and susceptibility are studied. A number of interesting phenomena have been found such as the existence of the compensation phenomenon and the magnetization profiles exhibit P-type, N-type and Q-type behaviors.

Bouhou, S.; El Hamri, M.; Essaoudi, I.; Ainane, A.; Ahuja, R.

2015-01-01

310

Magnetic properties of two-phase superconductors  

E-print Network

We have recently proposed a theoretical model for superconductors endowed with two distinct superconducting phases, described by two scalar order parameters which condensate at different critical temperatures. On analyzing the magnetic behavior of such systems, we have found some observable differences with respect to the case of ordinary Ginzburg-Landau superconductors. In particular, at low temperature the London penetration length is strongly reduced and the Ginzburg-Landau parameter k becomes a function of temperature. By contrast, in the temperature region between the two phase transitions k is constant and the system is a type-I or a type-II superconductor depending on the ratio between the critical temperatures.

E. Di Grezia; S. Esposito; G. Salesi

2007-09-17

311

Influence of stress and texture on soft magnetic properties of thin films  

Microsoft Academic Search

This paper presents the relationship among stress, crystallographic texture, and soft magnetic properties of thin films. The magnetic properties considered are those affected by the formation of stripe domains and by the formation of magnetization ripple. In practice, one of these two undesirable domain structures is almost always the impediment to improving the soft magnetic properties. The theoretical analysis accounts

Pei Zou; Winnie Yu; James A. Bain

2002-01-01

312

Author's personal copy Magnetic properties of stainless steels at room and cryogenic temperatures  

E-print Network

: Magnetic measurement Ferromagnetic property Stainless steel Martensitic Ferritic a b s t r a c t The magnetic properties of ten types of ferritic and martensitic stainless steels have been measured at room soft magnetic properties adequate for magnetic applications. The carbon content of the steels was found

Oxley, Paul

313

Encapsulated Fe3O4 /Ag complexed cores in hollow gold nanoshells for enhanced theranostic magnetic resonance imaging and photothermal therapy.  

PubMed

Designed and fabrication of a novel magnetic hollow gold nanoshell complexes that incorporates iron oxide nanoparticles in the hollow interior. The combined effect of the smaller IONPs improved the overall magnetic properties of the design and MRI contrast capability. The overall complex could be synthesized in the range of 60-80 nm in diameter while still having a plasmonic peak in the near infrared region. PMID:24729414

Lin, Adam Y; Young, Joseph K; Nixon, Ariel V; Drezek, Rebekah A

2014-08-27

314

Characterization of Magnetic Viral Complexes for Targeted Delivery in Oncology  

PubMed Central

Oncolytic viruses are promising new agents in cancer therapy. Success of tumor lysis is often hampered by low intra-tumoral titers due to a strong anti-viral host immune response and insufficient tumor targeting. Previous work on the co-assembly of oncolytic virus particles (VPs) with magnetic nanoparticles (MNPs) was shown to provide shielding from inactivating immune response and improve targeting by external field gradients. In addition, MNPs are detected by magnet resonance imaging (MRI) enabling non-invasive therapy monitoring. In this study two selected core-shell type iron oxide MNPs were assembled with adenovirus (Ad) or vesicular stomatitis virus (VSV). The selected MNPs were characterized by high r2 and r2* relaxivities and thus could be quantified non-invasively by 1.5 and 3.0 tesla MRI with a detection limit below 0.001 mM iron in tissue-mimicking phantoms. Assembly and cell internalization of MNP-VP complexes resulted in 81 - 97 % reduction of r2 and 35 - 82 % increase of r2* compared to free MNPs. The relaxivity changes could be attributed to the clusterization of particles and complexes shown by transmission electron microscopy (TEM). In a proof-of-principle study the non-invasive detection of MNP-VPs by MRI was shown in vivo in an orthotopic rat hepatocellular carcinoma model. In conclusion, MNP assembly and compartmentalization have a major impact on relaxivities, therefore calibration measurements are required for the correct quantification in biodistribution studies. Furthermore, our study provides first evidence of the in vivo applicability of selected MNP-VPs in cancer therapy.

Almstätter, Isabella; Mykhaylyk, Olga; Settles, Marcus; Altomonte, Jennifer; Aichler, Michaela; Walch, Axel; Rummeny, Ernst J.; Ebert, Oliver; Plank, Christian; Braren, Rickmer

2015-01-01

315

A study of uranium-based multilayers: II. Magnetic properties  

NASA Astrophysics Data System (ADS)

SQUID magnetometry and polarized neutron reflectivity (PNR) measurements have been employed to characterize the magnetic properties of U/Fe, U/Co and U/Gd multilayers. The field dependence of the magnetization was measured at 10 K in magnetic fields up to 70 kOe. A reduction in the magnetic moment was found for all systems. Magnetic 'dead' layers of ~15 Å were determined for U/Fe and U/Co samples, indicative of chemically diffuse interfaces. For very thick layers, magnetic moments close to the bulk values were expected. For the U/Gd system, a large reduction in the magnetic moment, constant over a wide range of Gd layer thicknesses, was found (~4 µB compared with 7.63 µB for the bulk metal). A possible explanation for this behaviour, consistent with observations of the structure of these multilayers, is that the Gd moments are pinned at the boundaries of column-like crystallites within the Gd layers. A study of the effective anisotropy and of a finite-size scaling behaviour of the U/Gd system is also presented. PNR data were collected in a field of 4.4 kOe for U/Fe and U/Co samples (at room temperature) and for U/Gd samples (at 10 K). Model calculations of the reflectivities used inputs extracted from the structural survey carried out on these systems, combined with data from the bulk magnetization measurements.

Springell, R.; Zochowski, S. W.; Ward, R. C. C.; Wells, M. R.; Brown, S. D.; Bouchenoire, L.; Wilhelm, F.; Langridge, S.; Stirling, W. G.; Lander, G. H.

2008-05-01

316

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

317

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

SciTech Connect

Co{sub x}C magnetic nanoparticles were successfully synthesized via a modified polyol process without using a rare-earth catalyst during the synthesis process. The present results show admixtures of Co{sub 2}C and Co{sub 3}C phases possessing magnetization values exceeding 45?emu/g and coercivity values exceeding 2.3 kOe at room temperature. Moreover, these experiments have illuminated the important role of surfactants, reaction temperature, and reaction duration on the crystallographic structure and magnetic properties of Co{sub x}C, while tetraethylene glycol was employed as a reducing agent. The role of the ratios of Co{sub 2}C and Co{sub 3}C phases in the admixture magnetic properties is discussed. The crystallographic structure and particle size of the Co{sub x}C nanoparticles were characterized by X-ray diffractometry and scanning electron microscopy. Vibrating sample magnetometry was used to determine magnetic properties. Scale-up of synthesis to more than 5 g per batch was demonstrated with no significant degradation of magnetic properties.

Zamanpour, Mehdi, E-mail: zamanpour.m@husky.neu.edu; Bennett, Steven; Taheri, Parisa; Chen, Yajie [Center for Microwave Magnetic Materials and Integrated Circuits, Northeastern University, Boston, Massachusetts 02115 (United States); Harris, Vincent G. [Center for Microwave Magnetic Materials and Integrated Circuits, Northeastern University, Boston, Massachusetts 02115 (United States); Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts 02115 (United States)

2014-05-07

318

Assessment of DNA complexation onto polyelectrolyte-coated magnetic silica nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

319

Magnetic properties of xenoliths from Yakut kimberlite pipes  

NASA Astrophysics Data System (ADS)

Lower continental crust is poorly known due to its limited availability. One source of information about the formation of the lower crust is the study of xenoliths found in kimberlites, mainly peridotites, eclogites and other rocks made by the kimberlite magma to the surface from great depths. Magnetic methods can solve problems related on the one hand, the definition of the phase composition of natural ferrimagnetics responsible for the magnetic properties of rocks, and on the other - with the establishment of the thermodynamic conditions in which they were formed - their genesis. For example, in [1, 2], there were differences in the magnetic properties of kimberlites taken from tubes with different diamond productivity. In this work, studies have been conducted of the magnetic properties and mineralogy of xenoliths from 10 Yakut kimberlit pipes, courtesy of Doctor of Geological and Mineralogical Sciences V. K. Garanin. Found that the natural remanent magnetization (NRM) and magnetic susceptibility (k0) of the investigated samples varies widely: NRM = (0.002-12.59) A/m, k0 = (0.23-59.9)*10-3 SI. Magnetic properties vary by species: average NRM peridotites (0.002-0.32) A/m order of magnitude smaller eclogitic rocks (0.58-12.59) A/m. Thermomagnetic analysis (TMA) of the test samples showed the presence of xenoliths of the ferromagnetic phase with a Curie point close to Tc magnetite. Because of the high correlation between the values of NRM, k0 and ferrimagnetic saturation magnetization (SM) can be inferred that the magnetic properties of the rocks studied at temperatures above ambient is basically determined by the concentration of magnetite in them. Besides magnetite TMA were also identified ferrimagnetic phase with Curie temperatures from -50°C to -125°C. Mineralogical analysis performed on three samples of peridotite tubes Udachnaya, Yubileynaya and Mir and two samples of eclogite tubes Udachnaya and Komsomolskaya, showed that at temperatures below room temperature magnetic properties of peridotites due ferrishpineles with high content of chromium, titanium and aluminum; eclogitic rocks - due hemoilmenites. Among the studied xenoliths, peridotites from the tubes with high diamond productivity (Udachnaya, Mir, Yubileynaya) are characterized by low values of NRM, k0, SM and high paramagnetic contribution. We conclude that the concentration of magnetite in them is very small, and the magnetic properties peridotite above room temperature are determined mainly paramagnetic minerals. This work was supported by RFBR grant No. 11-05-00740. Literature: 1. V.I. Truhin, V.A. Zhilyaeva, N.N. Zinchuk, N.N. Romanov. Kimberlites and traps magnetism. M.MGU. 1989. p. 165 (Russian) 2. V.I. Maksimochkin, V.I. Truhin, Y.A. Minina. Magnetic properties and mineralogy of Botswana kimberlites. Physics of the Earth, 2013, No. 2, p. 143-160 (Russian)

Tselebrovskiy, Alexey; Maksimochkin, Valeriy

2014-05-01

320

Physical properties of elongated magnetic particles: magnetization and friction coefficient anisotropies.  

PubMed

Anisotropy counts: A brief review of the main physical properties of elongated magnetic particles (EMPs) is presented. The most important characteristic of an EMP is the additional contribution of shape anisotropy to the total anisotropy energy of the particle, when compared to spherical magnetic particles. The electron micrograph shows Ni-ferrite microrods fabricated by the authors.We present an overview of the main physical properties of elongated magnetic particles (EMPs), including some of their more relevant properties in suspension. When compared to a spherical magnetic particle, the most important characteristic of an EMP is an additional contribution of shape anisotropy to the total anisotropy energy of the particle. Increasing aspect ratios also lead to an increase in both the critical single-domain size of a magnetic particle and its resistance to thermally activated spontaneous reversal of the magnetization. For single-domain EMPs, magnetization reversal occurs primarily by one of two modes, coherent rotation or curling, the latter being facilitated by larger aspect ratios. When EMPs are used to prepare colloidal suspensions, other physical properties come into play, such as their anisotropic friction coefficient and the consequent enhanced torque they experience in a shear flow, their tendency to align in the direction of an external field, to form less dense sediments and to entangle into more intricate aggregates. From a more practical point of view, EMPs are discussed in connection with two interesting types of magnetic colloids: magnetorheological fluids and suspensions for magnetic hyperthermia. Advances reported in the literature regarding the use of EMPs in these two systems are included. In the final section, we present a summary of the most relevant methods documented in the literature for the fabrication of EMPs, together with a list of the most common ferromagnetic materials that have been synthesized in the form of EMPs. PMID:19434654

Vereda, Fernando; de Vicente, Juan; Hidalgo-Alvarez, Roque

2009-06-01

321

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

NASA Astrophysics Data System (ADS)

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

Mishima, Toshiaki; Owada, Takeshi; Moriyama, Takashi; Ishida, Norihisa; Takahashi, Kosuke; Nagamachi, Shingo; Yoshitake, Yuki; Minamoto, Yasuhiro; Muromatsu, Fujio; Toyodome, Shuichi

2013-04-01

322

Technical properties of iron powder magnets  

Microsoft Academic Search

Coercive force, remanence and maximum energy product of compacts of iron are measured as functions of density of packing (d\\/d0) and X-ray particle size (L). The iron is prepared by hydrogen reduction of ferric oxide and for the grade used optimum technical properties are: Br = 5200 gauss, (B. H)max = 0.82 × 106 gauss: oersted, and BHC = 400

E H Carman

1955-01-01

323

Magnetic properties of indium-substituted orthoferrites  

SciTech Connect

Single crystals of indium-substituted yttrium and dysprosium orthoferrites were obtained by the method of spontaneous crystallization from a solution in a melt. As the indium concentration was increased in the yttrium orthoferrite, the transverse weakly ferromagnetic moment and the anisotropy constant in the ac crystallographic plane were found to increase. A change in the nature of the spin-reorientational transition of the Morin type is observed in the indium-substituted sysprosium orthoferrite, but, in contrast to substitution by gallium, aluminum, and scandium ions, the giant effect of the nonmagnetic impurity on the temperature of the indicated transition does not occur. Based on the results of the magnetic measurements it was concluded that the indium ions in the rare-earth orthoferrites prefer positions occupied by the rare-earth ions.

Ges', A.P.; Derkachenko, V.N.; Fedotova, V.V.; Kadomtseva, A.M.; Lukina, M.M.; Milov, V.N.

1986-03-01

324

Magnetic property enhancement of modified nanocrystalline ZrCo5-based magnets  

NASA Astrophysics Data System (ADS)

The metastable ZrCo5 compound may be a good candidate for the development of rare-earth-free high-performance hard magnetic materials because of its high magnetocrystalline anisotropy field. Melt spinning is a good approach to synthesize metastable phase because of its high quench rate. In this work, the effect of Zr and Fe addition on structure and magnetic properties of melt-spun nanocrystalline Zr1+xCo5(0--0.3) alloys has been investigated. All the samples consist of orthorhombic ZrCo5 hard magnetic and Co/Zr6Co23 soft magnetic phases. Proper Zr addition causes nanostructure refinement and the increase of the hard magnetic phase content, which strengthens intergrain exchange coupling. As a result, coercivity and maximum energy product of ZrCo5-based magnet are significantly enhanced. The best magnetic properties: iHc = 2.8 kOe, (BH)max = 4MGOe, which is the best value among Co-Zr binary alloys, are achieved in Zr1.1Co5. The temperature coefficient of its coercivity between 10 and 380K is -0.05%/K. The saturation magnetization of nanocrystalline Zr1.1Co5 is greatly increased due to 16 at% Fe addition.

Zhang, Wenyong; Li, Xingzhong; Skomski, Ralph; Shield, Jeff; Sellmyer, David J.

2012-02-01

325

Magnetic properties of maraging steels in relation to nickel concentration  

SciTech Connect

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

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

1995-07-01

326

ON THE MAGNETIC PROPERTIES OF OXIDES OF GADOLINIUM  

Microsoft Academic Search

The temperature dependence of the magnetic properties of gadolinium ; ferrites with garnet and perovskite structures and also of gadolinium manganate ; was measured. It is found that at the compensation point and the Curie point ; there is an anomalous growth of the coercive force and a very small paraprocess ; in garnet ferrite. There is also an anomaly

K. P. Belov; M. A. Zaitseva; A. V. Pedko

1959-01-01

327

Anisotropic nanomaterials: Synthesis, optical and magnetic properties, and applications  

Microsoft Academic Search

As nanoscience and nanotechnology mature, anisotropic metal nanostructures are emerging in a variety of contexts as valuable class of nanostructures due to their distinctive attributes. With unique properties ranging from optical to magnetic and beyond, these structures are useful in many new applications. Chapter two discusses the nanodisk code: a linear array of metal disk pairs that serve as surface-enhanced

Matthew John Banholzer

2010-01-01

328

On the Effective Magnetic Properties of Magnetorheological Fluids \\Lambda  

E-print Network

On the Effective Magnetic Properties of Magnetorheological Fluids \\Lambda November 9, 1998 Tammy M. Simon 1 , F. Reitich 2 , M.R. Jolly 3 , K. Ito 1 , H.T. Banks 1 Abstract Magnetorheological (MR) fluids] and Doyle [4]. 1 Introduction Magnetorheological (MR) fluids are suspensions of micron­sized magnetizable

329

Magnetic properties of carbon nanotubes with and without catalyst  

Microsoft Academic Search

In this paper we report on the magnetic properties of single- and multiwalled carbon nanotubes synthesized using different chemical vapour deposition methods and with variety of catalyst materials (ferromagnetic Fe, FeCo and diamagnetic Re). Different methods yield carbon nanotubes with different morphologies and different quantity of residual catalyst material. Catalyst particles are usually encapsulated in the nanotubes and influence the

Kamil Lipert; Manfred Ritschel; Albrecht Leonhardt; Yulia Krupskaya; Bernd Büchner; Rüdiger Klingeler

2010-01-01

330

Four-color theorem linked to crystal's magnetic properties  

E-print Network

Four-color theorem linked to crystal's magnetic properties Domain patterns can be understood in terms of color theorems. (a) Image of the domains in a crystal material and (b) the domains colored in accordance with the four-color theorem. (c) Image of the domains in a second crystal material and (d

Glashausser, Charles

331

Magnetic properties and internal friction of iron carbide powder steels  

Microsoft Academic Search

The effect of the carbon content and the density on the magnetic properties and internal friction of iron carbide baked powder steels is investigated. It is shown that for a separate determination of the carbon content and the density of baked steels one needs to use the coercive force and the velocity of propagation of oscillations or the natural resonance

A. V. Zagainov; E. S. Gorkunov

1995-01-01

332

Hard X-ray properties of magnetic cataclysmic S. Scaringi  

E-print Network

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

Norton, Andrew J.

333

SOME MAGNETIC PROPERTIES OF DILUTE FERROMAGNETIC ALLOYS By W. SUCKSMITH,  

E-print Network

-ferromagnetic element should have a low solubility limit for the ferromagnetic element so that interaction between the ferromagnetic elements does not occur. Thus, a detailed investigation of the variation of the magnetic properties of copper rich copper-iron and copper-cobalt alloys with annealing after quenching was carried out

Boyer, Edmond

334

Spectra and magnetic properties of large spins in external fields  

E-print Network

Spectra and magnetic properties of large spins J (e.g., spins possessed by ions or molecules), placed into a crystal electric field (CEF) of an arbitrary symmetry point group, are shown to change drastically when J changes by 1/2 or 1. At a fixed...

Kalatsky, V. A.; Pokrovsky, Valery L.

1999-01-01

335

Transport properties of graphene under periodic and quasiperiodic magnetic superlattices  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

336

Magnetic properties of NpX 2 intermetallic compounds  

NASA Astrophysics Data System (ADS)

The magnetic and electronic properties of NpX 2 (X = Ga, Si) were studied by Mössbauer and ac-dc magnetization techniques. Both order ferromagnetically below TC = 55(2) and 48(2) K respectively. A comparison of our data with the results for other NpX 2 (X = Al, As, Sb, Te) compounds indicates that NpGa 2 is a highly localized 5f electron system, whereas in NpSi 2 the 5f electrons are partially delocalized. The magnetic properties of NpX 2 compounds can neither be consistently explained within the conventional crystal electric field picture (CEF) nor by taking into account hybridization dressing or local spin density models.

Yaar, I.; Gal, J.; Potzel, W.; Kalvius, G. M.; Will, G.; Schäfer, W.

1992-02-01

337

Magnetic property improvement of niobium doped with rare earth elements  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

338

Magnetic properties of tephras from Lake Van (Eastern Turkey)  

NASA Astrophysics Data System (ADS)

Here we present magnetic properties of tephra layers in the cores taken from Lake Van, Eastern Anatolia, Turkey. Lake Van is the fourth largest terminal Lake in the world by volume (607 km3). It is 460 m deep and has a salinity of 21.4 per mil and a pH of 9.81. It is located on the East Anatolian Plateau with present day water level of 1648 m.a.s.l., and surrounded by large stratovolcanoes Nemrut, Suphan, Tendurek, and Ararat to the west and north. It has accumulated varved-sediments with tephra units, which all provide important paleoenvironmental records. After a seismic survey, four different locations were selected for coring in Lake Van, with water depths varying between 60 m and 90 m. Four cores having between 3 and 4.8 m length were analyzed for for element geochemistry using XRF Core Scanner analysis. The sub-samples were taken into plastic boxes with a volume of 6.4 cm3 for mineral magnetic analysis. The mineral magnetic measurements included magnetic susceptibility (?), anhysteretic remanent magnetisation (ARM), isothermal remanent magnetisation (IRM), hysteresis properties and thermomagnetic analyses. According to the mineral magnetic measurements and geochemical analysis, we identified the five tephra layers (T1-T5). These tephra units were correlated with the previously varve-dated units of Landmann et al. (2011). The varve ages of the tephra layers were used to obtain the age-depth model for the cores. According to the age models the cores extend back to 9500 ka BP (varve years). Down-core profiles of all the magnetic properties are highly correlatable between different cores, suggesting that the magnetic records are of regional character. ARM values are found to be more convenient than ? values for correlating the tephra layers. The hysteresis parameters of samples taken from these layers indicate that they are within Pseudo Single Domain range. IRM curves show that low coersivity magnetic minerals are dominated in all tephra layers. Measurements of the temperature dependence of magnetic susceptibility suggest that the magnetic mineralogy at all tephra layers is dominated by magnetite. All tephra layers have distinct magnetic signature which are characterized by strong ferromagnetic mineral and high Zr and K values, suggesting their alkaline composition. Landmann G, Steinhauser G, Sterba JH, Kempe S, Bichler M., 2011. Geochemical fingerprints by activation analysis of tephra layers in Lake Van sediments, Turkey. Applied Radiation and Isotopes 69, 929-935

Makaroglu, Ozlem; Ca?atay, Nam?k; Pesonen, Lauri J.; Orbay, Naci

2013-04-01

339

Direct production of hard magnetic ribbons with enhanced magnetic properties by controlling cooling rate of melt  

NASA Astrophysics Data System (ADS)

We produced a high-quality hard magnetic Fe81Co2Nb1Nd10B6 alloy by melt spinning without additional treatment. The as-spun ribbons produced at a wheel speed of ˜25 m/s had the best hard magnetic properties: a remanence Br, coercive force Hc, and maximum energy product (BH)max of 0.97 T, 676 kA/m, and 140 kJ/m3, respectively. The Nd2Fe14B/?-Fe nanocomposite phases had grain sizes of ˜10-30 nm. We investigated how the magnetic properties changed with wheel speed, finding that they depended on the as-spun structure and magnetic structure, which changed upon over- and under-quenching from the melt.

Zhou, Weifei; Chang, Chuntao; Inoue, Akihisa; Wang, Xinmin; Li, Fushan; Huo, Juntao

2015-03-01

340

Examining the Magnetic Properties of LaCoO3 Thin Films Using Magnetic Force Microscopy  

NASA Astrophysics Data System (ADS)

In contrast to the non-magnetic ground state of bulk LaCoO3 (LCO) at low temperatures, ferromagnetism has been observed in elastically strained thin film specimens. The origins of ferromagnetism in strained LCO thin films have been obscured by conflicting experimental results. Pulsed laser deposition (PLD) is the current standard of preparation techniques used to grow thin films of LCO, but results from thin film LCO samples prepared by PLD have been questioned on the basis of chemical inhomogeneity and film defects. Using magnetic force microscopy, we investigate the microscale magnetic properties of strained thin films of LCO prepared by molecular beam epitaxy and deposited on lanthanum aluminate and strontium titanate substrates. We observe these properties across a temperature range surrounding the Curie temperature (Tc˜ 80K) and compare our results to global magnetic characteristics of these films as measured by a SQUID magnetometer.

Berg, Morgann; Posadas, Agham; de Lozanne, Alex; Demkov, Alexander

2011-03-01

341

Magnetic properties prediction of NdFeB magnets by using support vector regression  

NASA Astrophysics Data System (ADS)

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

Cheng, Wende

2014-09-01

342

Magnetic properties of pulsed laser deposition-fabricated isotropic Fe-Pt film magnets  

SciTech Connect

A high-speed pulsed laser deposition method with the deposition rate of several tens of microns per 1 h enabled us to obtain isotropic Fe-Pt thick film magnets. Increase in the laser power enabled us to obtain as-deposited films with L1{sub 0} ordered phase due to the heat radiation from a target, which means that a substrate heating system and a post-annealing process are not required to achieve hard magnetic properties in the process. Use of an Fe-rich target enhanced the magnetic properties, and as a result (BH){sub max} value exceeded 100 kJ/m{sup 3} in an isotropic Fe-Pt film fabricated at the power of 3 W, which was comparable to those of isotropic Fe-Pt thick film magnets prepared by a sputtering method.

Nakano, M.; Oniki, W.; Yanai, T.; Fukunaga, H. [Faculty of Engineering, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki, 852-8521 (Japan)

2011-04-01

343

Structure, magnetic and electrical properties of soft magnetic Co-C amorphous thin films  

NASA Astrophysics Data System (ADS)

Amorphous Co xC 1- x thin films, with x in the range of 60-75% in atomic percentage, have been prepared by pulsed filtered vacuum arc deposition. The structures of the films were characterized by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The in-plane magnetic hysteresis loops were measured by a superconducting quantum interference device magnetometer at room temperature. The electrical transport properties were measured by the four-probe technique at various temperatures ranging from 20 to 300 K. The films were found to be magnetically soft with coercivities in the range of 2 to 12 Oe, resistivities in the range of 130 to 300 ? ? cm, and magnetic saturation flux densities in the range of 6 to 13 kG. The films also showed good thermal stability in their structural, electrical and magnetic properties upon annealing up to 200 °C in a vacuum furnace.

Wang, Hao; Chiah, M. F.; Cheung, W. Y.; Wong, S. P.

2003-09-01

344

Magnetism in Complex Oxides Probed by Magnetocaloric Effect and Transverse Susceptibility  

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 themes that are often present in these systems are the phase coexistence, strong magnetostructural coupling, and possible spin frustration induced by lattice geometry. While a complete understanding of the ground state magnetic properties and cooperative phenomena in this class of compounds is key to manipulating their functionality for applications, it remains among the most challenging problems facing condensed-matter physics today. To address these outstanding issues, it is essential to employ experimental methods that allow for detailed investigations of the temperature and magnetic field response of the different phases. In this PhD dissertation, I will demonstrate the relatively unconventional experimental methods of magnetocaloric effect (MCE) and radio-frequency transverse susceptibility (TS) as powerful probes of multiple magnetic transitions, glassy phenomena, and ground state magnetic properties in a large class of complex magnetic oxides, including La0.7Ca0.3- xSrxMnO3 (x = 0, 0.05, 0.1, 0.2 and 0.25), Pr0.5Sr0.5MnO3, Pr1-xSrxCoO 3 (x = 0.3, 0.35, 0.4 and 0.5), La5/8- xPrxCa3/8MnO3 (x = 0.275 and 0.375), and Ca3Co2O 6. First, the influences of strain and grain boundaries, via chemical substitution and reduced dimensionality, were studied via MCE in La0.7Ca 0.3-xSrxMnO 3. Polycrystalline, single crystalline, and thin-film La0.7Ca 0.3-xSrxMnO 3 samples show a paramagnetic to ferromagnetic transition at a wide variety of temperatures as well as an observed change in the fundamental nature of the transition (i.e. first-order magnetic transition to second order magnetic transition) that is dependent on the chemical concentration and dimensionality. Systematic TS and MCE experiments on Pr0.5Sr0.5MnO 3 and Pr0.5Sr0.5CoO3 have uncovered the different nature of low-temperature magnetic phases and demonstrate the importance of coupled structural/magnetocrystalline anisotropy in these half-doped perovskite systems. These findings point to the existence of a distinct class of phenomena in transition-metal oxide materials due to the unique interplay between structure and magnetic anisotropy, and provide evidence for the interplay of spin and orbital order as the origin of intrinsic phase separation in manganites. While Pr0.5Sr0.5MnO3 provides important insights into the influence of first- and second-order transitions on the MCE and refrigerant capacity (RC) in a single material, giving a good guidance on the development of magnetocaloric materials for active magnetic refrigeration, Pr1-xSrxCoO 3 provides an excellent system for determining the structural entropy change and its contribution to the MCE in magnetocaloric materials. We have demonstrated that the structural entropy contributes significantly to the total entropy change and the structurally coupled magnetocrystalline anisotropy plays a crucial role in tailoring the magnetocaloric properties for active magnetic refrigeration technology. In the case of La5/8-xPr xCa3/8MnO3, whose bulk form is comprised of micron-sized regions of ferromagnetic (FM), paramagnetic (PM), and charge-ordered (CO) phases, TS and MCE experiments have evidenced the dominance of low-temperature FM and high-temperature CO phases. The "dynamic" strain liquid state is strongly dependent on magnetic field, while the "frozen" strain-glass state is almost magnetic field independent. The sharp changes in the magnetization, electrical resistivity, and magnetic entropy just below the Curie temperature occur via the growth of FM domains already present in the material, even in zero magnetic field. The subtle balance of coexisting phases and kinetic arrest are also probed by MCE and TS experiments, leading to a new and more comprehensive magnetic phase diagram. A geometrically frustrated spin chain compound Ca3Co 2O6 provides an interesting case study for understanding the cooperative pheno

Bingham, Nicholas S.

345

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

SciTech Connect

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

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

2014-01-01

346

Three-dimensional Magnetostriction and Vector Magnetic Properties under Alternating Magnetic Flux Conditions in Arbitrary Direction  

NASA Astrophysics Data System (ADS)

This paper presents measured magnetostriction of electrical steel sheets under alternating magnetic flux conditions. In the measurements, we used a two-dimensional vector magnetic property measurement system, and a three-axial strain gauge. In order to know magnetostrictions in arbitrary direction, the strain tensor was evaluated. In addition, we try to evaluate the magnetostrictions in thickness direction. In this paper, the three-dimensional magnetostriction in non-oriented and grain-oriented silicon steel sheets are compared.

Wakabayashi, Daisuke; Todaka, Takashi; Enokizono, Masato

347

Magnetic and magnetotransport properties of new III-V diluted magnetic semiconductors: GaMnAs  

Microsoft Academic Search

We have studied magnetic and magnetotransport properties of novel III-V diluted magnetic semiconductors, (Ga1?xMnx)As. The GaMnAs thin films were grown on GaAs(001) substrates by low temperature molecular beam epitaxy. We present magnetoresistance, extraordinary Hall effect, and M–H characteristics of two (Ga1?xMnx)As samples having different Mn content x.

T. Hayashi; M. Tanaka; T. Nishinaga; H. Shimada

1997-01-01

348

Magnetic nanocrystals: Synthesis and properties of diluted magnetic semiconductor quantum dots  

Microsoft Academic Search

The chapters in this thesis describe the investigations into the synthesis and magnetic and electronic properties of diluted magnetic semiconductor quantum dots (DMS-QDs), specifically Co2+ and Mn2+-doped ZnO and Co2+:ZnSe. Homogeneous dopant incorporation and substitutional speciation of Co2+ and Mn2+ in ZnO QDs during solution synthesis at room temperature were confirmed by electronic absorption and electron paramagnetic resonance spectroscopy measurements.

Nicholas S. Norberg

2006-01-01

349

Magnetorheological properties of a magnetic nanofluid with dispersed carbon nanotubes.  

PubMed

We investigate the effect of multiwalled carbon nanotubes (MWCNTs) on the magnetorheological properties of an oil based magnetic nanofluid (ferrofluid). The shear resistant plateau observed in a pure ferrofluid disappears when 0.5 wt% of MWCNT is incorporated. The yield stress values of the composite system are slightly smaller than that of the pure system. This shows that the presence of carbon nanotubes (CNTs) weakens the magnetic field induced microstructure of the ferrofluid due to their interaction that affects the hydrodynamic and magnetic interactions between the dispersed nanoparticles. Interestingly, the Mason number plots for both the pure and composite system show scaling of the viscosity curves onto a single master curve for magnetic fields of 80 mT and above while deviations are observed for lower magnetic fields. The weakening of the ferrofluid microstructure in the presence of CNTs is further evident in the amplitude sweep measurements where the linear viscoelastic region develops only at a higher magnetic field strength compared to lower magnetic fields in pure ferrofluids. These results are useful for tailoring ferrofluids with a faster response for various applications. PMID:25353475

Felicia, Leona J; Philip, John

2014-02-01

350

Magnetic and ferroelectric properties of multiferroic RMn2O5  

NASA Astrophysics Data System (ADS)

The magnetic and ferroelectric properties of multiferroic RMn2O5 (R = Y, Tb, Ho, Er, Tm) are reviewed based on recent neutron diffraction and dielectric measurements. Successive phase transitions of magnetic and dielectric ordering were found to occur simultaneously in this system. The characteristic magnetic ordering of the system exhibits an incommensurate-commensurate phase transition, and again transitions to an incommensurate phase. Special attention is given to the magnetic structure in order to discuss the mechanism for the introduction of ferroelectric polarization. For all the compounds examined, the spin configuration for Mn4+ and Mn3+ ions in the commensurate magnetic phase, where spontaneous electric polarization occurs, was determined to be a transverse spiral spin structure propagating along the c-axis. By contrast, the alignment of the induced 4f moment of R3+ ions showed variation, depending on the character of each of the elements. Corresponding responses to external fields such as a magnetic field, hydrostatic pressure etc at low temperature are strongly dependent on the rare earth element present in the RMn2O5 system. The so-called colossal magnetoelectric effect in this system can be easily interpreted by the phase transition from the magnetic incommensurate and weak ferroelectric phase to the commensurate and ferroelectric phase.

Noda, Y.; Kimura, H.; Fukunaga, M.; Kobayashi, S.; Kagomiya, I.; Kohn, K.

2008-10-01

351

Crystal growth and magnetic properties of equiatomic CeAl  

NASA Astrophysics Data System (ADS)

Single crystal of CeAl has been grown by flux method using Ce-Al self-flux. Several needle like single crystals were obtained and the length of the needle corresponds to the [001] crystallographic direction. Powder x-ray diffraction revealed that CeAl crystallizes in orthorhombic CrB-type structure with space group Cmcm (no. 63). The magnetic properties have been investigated by means of magnetic susceptibility, isothermal magnetization, electrical transport, and heat capacity measurements. CeAl is found to order antiferromagnetically with a Neel temperature TN = 10 K. The magnetization data below the ordering temperature reveals two metamagentic transitions for fields less than 20 kOe. From the inverse magnetic susceptibility an effective moment of 2.66 ?B/Ce has been estimated, which indicates that Ce is in its trivalent state. Electrical resistivity data clearly shows a sharp drop at 10 K due to the reduction of spin disorder scattering of conduction electrons thus confirming the magnetic ordering. The estimated residual resistivity ratio (RRR) is 33, thus indicating a good quality of the single crystal. The bulk nature of the magnetic ordering is also confirmed by heat capacity data. From the Schottky anomaly of the heat capacity we have estimated the crystal field level splitting energies of the (2J + 1) degenerate ground state as 25 K and 175 K respectively for the fist and second excited states.

Das, Pranab Kumar; Thamizhavel, A.

2015-03-01

352

Magnetic properties of mixed-valence iron phosphate glasses  

NASA Astrophysics Data System (ADS)

Magnetic properties of mixed-valence iron phosphate glasses, where there coexist Fe2+ and Fe3+ ions, have been investigated. The molar fraction of Fe3+ with respect to the total iron ion, [Fe3+]/[Fetotal] , can be controlled by melting the glass at varied temperatures. Experiments of magnetic aging and memory effects as well as dynamic and static scaling analyses of relaxation time and nonlinear magnetic susceptibility have been performed to get insight into the nature of low-temperature magnetic phase of the glass system. The experimental results reveal that the iron phosphate glasses undergo paramagnet-spin-glass transitions at low temperatures. Temperature dependence of magnetic specific heat suggests that as the temperature is lowered, the magnetic moments start to be frozen at a temperature significantly higher than the spin-glass transition temperature accompanied by a deviation in magnetic susceptibility from Curie-Weiss law. The ratio of the absolute value of Weiss temperature to spin-glass transition temperature increases as the ratio [Fe3+]/[Fetotal] becomes larger. This behavior is explainable in terms of the difference in single-ion anisotropy between Fe3+ and Fe2+ ions.

Akamatsu, Hirofumi; Oku, Satoshi; Fujita, Koji; Murai, Shunsuke; Tanaka, Katsuhisa

2009-10-01

353

Structural, magnetic, and transport properties of Permalloy for spintronic experiments  

SciTech Connect

Permalloy (Ni{sub 80}Fe{sub 20}) is broadly used to prepare magnetic nanostructures for high-frequency experiments where the magnetization is either excited by electrical currents or magnetic fields. Detailed knowledge of the material properties is mandatory for thorough understanding its magnetization dynamics. In this work, thin Permalloy films are grown by dc-magnetron sputtering on heated substrates and by thermal evaporation with subsequent annealing. The specific resistance is determined by van der Pauw methods. Point-contact Andreev reflection is employed to determine the spin polarization of the films. The topography is imaged by atomic-force microscopy, and the magnetic microstructure by magnetic-force microscopy. Transmission-electron microscopy and transmission-electron diffraction are performed to determine atomic composition, crystal structure, and morphology. From ferromagnetic resonance absorption spectra the saturation magnetization, the anisotropy, and the Gilbert damping parameter are determined. Coercive fields and anisotropy are measured by magneto-optical Kerr magnetometry. The sum of the findings enables optimization of Permalloy for spintronic experiments.

Nahrwold, Gesche; Scholtyssek, Jan M.; Motl-Ziegler, Sandra; Albrecht, Ole; Merkt, Ulrich; Meier, Guido [Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung, Universitaet Hamburg, Jungiusstrasse 11, 20355 Hamburg (Germany)

2010-07-15

354

The magnetic-nanofluid heat pipe with superior thermal properties through magnetic enhancement.  

PubMed

This study developed a magnetic-nanofluid (MNF) heat pipe (MNFHP) with magnetically enhanced thermal properties. Its main characteristic was additional porous iron nozzle in the evaporator and the condenser to form a unique flowing pattern of MNF slug and vapor, and to magnetically shield the magnet attraction on MNF flowing. The results showed that an optimal thermal conductivity exists in the applied field of 200?Oe. Furthermore, the minor thermal performance of MNF at the condenser limited the thermal conductivity of the entire MNFHP, which was 1.6 times greater than that filled with water for the input power of 60?W. The feasibilities of an MNFHP with the magnetically enhanced heat transfer and the ability of vertical operation were proved for both a promising heat-dissipation device and the energy architecture integrated with an additional energy system. PMID:22716909

Chiang, Yuan-Ching; Chieh, Jen-Jie; Ho, Chia-Che

2012-01-01

355

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

NASA Astrophysics Data System (ADS)

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

Inoue, Hirotaka; Okabe, Seiji

2014-05-01

356

On asymptotic properties of some complex Lorenz-like systems  

E-print Network

The classical Lorenz lowest order system of three nonlinear ordinary differential equations, capable of producing chaotic solutions, has been generalized by various authors in two main directions: (i) for number of equations larger than three (Curry1978) and (ii) for the case of complex variables and parameters. Problems of laser physics and geophysical fluid dynamics (baroclinic instability, geodynamic theory, etc. - see the references) can be related to this second aspect of generalization. In this paper we study the asymptotic properties of some complex Lorenz systems, keeping in the mind the physical basis of the model mathematical equations.

Stoicho Panchev; Nikolay K. vitanov

2005-09-26

357

Tale of a twist: magnetic and optical switching in copper(II) semiquinone complexes.  

PubMed

An intermediate (C) that is observed in both phenol hydroxylation and catechol oxidation with the side-on peroxide species [Cu(2)O(2)(DBED)(2)](2+) (DBED = N(1),N(2)-di-tert-butylethane-1,2-diamine) is identified as a copper(II) semiquinone species ([1](+)) through independent synthesis and characterization. The reaction of the redox-active 3,5-di-tert-butylquinone ligand with [(DBED)Cu(I)(MeCN)](+) yields a copper(II) semiquinone [1](+) complex with a singlet ground state and an intense purple chromophore (?(580) ~ 3500 M(-1) cm(-1)). All other copper(II) semiquinone complexes characterized to date are paramagnetic and weakly colored (?(800) ~ 500 M(-1) cm(-1)). Antiferromagnetic coupling between the Cu(II) center and the semiquinone radical in [1](+) is characterized by paramagnetic (1)H NMR and SQUID magnetometry. Comparative X-ray crystal structures along with density functional theory calculations correlate the geometric structures of copper(II) semiquinone complexes with their magnetic and optical properties. The unique observable properties of [1](+) originate from an increase in the overlap of the Cu 3d and semiquinone ? orbitals resulting from a large rhombic distortion in the structure with a twist of 51°, attributable to the large isotropic demands of the tert-butyl substituents of the DBED ligand. Independent characterization of [1](+) allows the spectroscopic yields of intermediate C to be quantified in this intriguing hydroxylation reaction. PMID:21696132

Verma, Pratik; Weir, John; Mirica, Liviu; Stack, T Daniel P

2011-10-17

358

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

359

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

PubMed

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

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

2014-01-01

360

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

PubMed Central

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

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

2014-01-01

361

Measurement of bidirectional optical properties of complex shading devices  

SciTech Connect

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

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

1995-01-01

362

Magnetic properties of Nickel Nanostructures Grown by Nanosphere Lithography Technique  

NASA Astrophysics Data System (ADS)

The self assembly nanosphere lithography (NSL) is an inexpensive scalable technique for production of Nanstrutures with controlled shape, size. The mono-dispersed 2D colloidal crystals (polystyrene nanoballs of 400nm size) on pre-treated Si (100) substrate is used as mask for creating nanofeatures of Ni. The monodisperse colloidal templates are prepared by drop coating method on hydrophilic Si (100) surfaces. The self assembled polystyrene nanoball templates are characterized by Scanning Electron Microscopy (SEM). Various defect structures, such as line defects, and point defects are observed in colloidal templates, which are inherent to self assembly process. The Ni-nanostructures (nanodots and nanowires) are obtained by growing ultra thin films (120 Å) of Ni onto the colloidal crystal template by vacuum thermal evaporation technique followed by mask removal. The nanostructures are characterized by scanning electron microscopy (SEM) for their structural features and by magnetic force microscopy (MFM) for magnetization properties. Random distribution of nanodot-size (ranging from 250-450 nm) and shapes are observed by scanning electron microscopy. Further we observed formation of nanorods of different dimensions and aligned in the plane of the substrate. Magnetic properties of these nanostructures formation magnetic nanorods are studied by magnetic force microscopy.

Akshay, S.; Kaushik, N. Nitin; Naresh, K.; De, Shounak; Moorthy, V. H. S.

2011-07-01

363

Magnetic properties of nanocrystalline KNbO{sub 3}  

SciTech Connect

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

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

2013-11-07

364

Magnetic properties and microstructure of ultrathin Co /Si(111) films  

NASA Astrophysics Data System (ADS)

The magnetic properties and microstructure of ultrathin Co films grown on a Si(111)-7×7 surface were investigated. The experimental results observed by surface magneto-optic Kerr effect (SMOKE) and scanning tunneling microscopy show that the surface morphological evolution of x ML (monolayer) Co /Si(111) films is strongly related to their magnetic properties. Due to the formation of a CoSi2 layer, no magnetic signal could be detected by SMOKE for x =2.1. Both longitudinal and polar hysteresis loops appear for 4.2-8.5 ML Co /Si(111) films because of their rougher surfaces. When the Co thickness is increased to 11 ML, a magnetic hysteresis loop only occurs in the longitudinal configuration, which can be attributed to the contribution of volume anisotropy. After annealing an 11 ML Co /Si(111) film at 400 and 500K, the surface becomes rougher, inducing magnetic anisotropy on the polar configuration. When the annealing temperature was increased to 600K, however, the Co could react with Si to form a nonmagnetic cobalt silicide compound, and consequently, the hysteresis loops disappeared.

Chang, H. W.; Tsay, J. S.; Hung, Y. C.; Yuan, F. T.; Chan, W. Y.; Su, W. B.; Chang, C. S.; Yao, Y. D.

2007-05-01

365

Axisymmetric Flow Properties for Magnetic Elements of Differing Strength  

NASA Technical Reports Server (NTRS)

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

Rightmire-Upton, Lisa; Hathaway, David H.

2012-01-01

366

Magnetic and magnetodielectric properties of erbium iron garnet ceramic  

NASA Astrophysics Data System (ADS)

An Er3Fe5O12 ceramic has been sintered in oxygen atmosphere at 1400 °C for dielectric measurements. Its structural quality at room temperature has been checked by combining transmission electron microscopy and X-ray diffraction. It crystallizes in the cubic space group Ia3d with a = 12.3488(1). The dielectric permittivity (?') and losses (tan ?) measurements as a function of temperature reveal the existence of two anomalies, a broad one between 110 K and 80 K, attributed to the Er3+ spin reorientation, and a second sharper feature at about 45 K associated to the appearance of irreversibility on the magnetic susceptibility curves. In contrast to the lack of magnetic field impact on ?' for the former anomaly, a complex magnetic field effect has been evidenced below 45 K. The isothermal ?'(H) curves show the existence of positive magnetodielectric effect, reaching a maximum of 0.14% at 3 T and 10 K. Its magnitude decreases as H is further increased. Interestingly, for the lowest H values, a linear regime in the ?'(H) curve is observed. From this experimental study, it is concluded that the ?' anomaly, starting above the compensation temperature Tc (75 K) and driven by the internal magnetic field, is not sensitive to an applied external magnetic field. Thus, below 45 K, it is the magnetic structure which is responsible for the coupling between spin and charge in this iron garnet.

Maignan, A.; Singh, K.; Simon, Ch.; Lebedev, O. I.; Martin, C.; Tan, H.; Verbeeck, J.; Van Tendeloo, G.

2013-01-01

367

Tuning the magnetic ground state of a tetranuclear nickel(II) molecular complex by high magnetic fields  

Microsoft Academic Search

Electron spin resonance and magnetization data in magnetic fields up to 55T of a multicenter paramagnetic molecular complex [L2Ni4(N3)(O2CAda)4](ClO4) are reported. In this compound, four Ni centers each having a spin S=1 are coupled in a single molecule via bridging ligands (including a mu4 -azide) which provide paths for magnetic exchange. Analysis of the frequency and temperature dependence of the

C. Golze; A. Alfonsov; R. Klingeler; B. Büchner; V. Kataev; C. Mennerich; H.-H. Klauss; M. Goiran; J.-M. Broto; H. Rakoto; S. Demeshko; G. Leibeling; F. Meyer

2006-01-01

368

Magnetic and magnetostrictive properties of manganese substituted cobalt ferrite  

Microsoft Academic Search

The magnetic and magnetostrictive properties of polycrystalline\\u000a Co1-xMnxFe2O4 ( 0 = x = 0.4) have been studied. Although the Curie\\u000a temperature decreases continuously with increasing concentration of Mn,\\u000a the magnetization remains high up to x = 0.3 and unexpectedly low\\u000a coercivity is observed for this composition showing an unusual\\u000a magnetostrictive behaviour. This composition shows a relatively larger\\u000a magnetostriction at low

S. D. Bhame; P. A. Joy

2007-01-01

369

Magnetic properties of Fe-R-B powders  

NASA Astrophysics Data System (ADS)

The magnetic properties of Fe77R15B8 powders have been measured as a function of particle size in the temperature range 77-300 K. The coercivity is found to increase first with particle size to a maximum value and then to decrease again. This behavior is explained with the single domain particle theory. The peak values of coercivity obtained in the various alloys are found to scale with the anisotropy field. The temperature coefficients of coercivity are smaller than those observed in sintered magnets.

Gudimetta, K.; Christodoulou, C. N.; Hadjipanayis, G. C.

1986-03-01

370

Effects of coating on magnetic properties in iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

We have studied influence of surface modification on physical properties of iron oxide nanoparticles. We compared samples prepared by thermal decomposition of organic precursor in the presence of oleic acid, and the particles prepared by coprecipitation and partially coated by SiO2 or modified by citric acid and subsequently covered by photoactive TiO2 layer, respectively. Samples were characterised using TEM and XRD, further magnetic studies such as temperature dependence of magnetization and a.c. susceptibility show superparamagnetic behavior for all samples at room temperature. The effects of coating on dipolar inter particle interactions are discussed.

Bittova, B.; Poltierova-Vejpravova, J.; Roca, A. G.; Morales, M. P.; Tyrpekl, V.

2010-01-01

371

Magnetic structure and magnetic properties of Nd1-xNaxMnO3 compounds  

NASA Astrophysics Data System (ADS)

The crystal structure, magnetic structure, and magnetic properties of Nd1-xNaxMnO3 (x = 0, 0.15, and 0.20) compounds were studied using magnetization and neutron powder diffraction techniques. The magnetic ordering is found to undergo a transition from A-type antiferromagnetic (AFM) structure for x = 0 to pseudo charge-exchange (CE)-type AFM phase for x = 0.20 through the spin canted ferromagnetic (FM) phase for x = 0.15. Two magnetic transitions at 75 K and 15 K were observed for x = 0 sample and are ascribed to AFM ordering of Mn ions and ferrimagnetic ordering of Nd ions, respectively. In the case of x = 0.15, a canted FM ordering at around 80 K and a pseudo CE-type AFM magnetic structure at 5 K were observed. The x = 0.20 sample exhibits a charge-ordering transition at 180 K followed by a spin-glass like transition at around 40 K. The magnetic structure of x = 0.20 sample below 125 K is found to be pseudo CE-type AFM structure. The propagation vectors associated with Mn3+ and Mn4+ sublattices are (0 0 1/2) and (1/2 0 1/2), respectively. The maximum refined magnetic moments of Mn3+ and Mn4+ ions in x = 0.20 sample are found to be 3.20 ?B and 3.00 ?B, respectively.

Samantaray, B.; Ravi, S.; Das, A.; Srivastava, S. K.

2011-11-01

372

Properties of a Viroid-replicating Complex Solubilized from Nuclei  

Microsoft Academic Search

SUMMARY An organelle-free fraction with the ability to synthesize citrus exocortis viroid (CEV) RNA was prepared from nuclei-rich samples taken from CEV-infected Gynura aurantiaca D.C. leaf tissue. This extraction was accomplished in the presence of the detergent sarkosyl. Characterization of the viroid synthetic reaction demonstrated that the solubilized complex retained the properties displayed by intact nuclei. These include optima of

R. F. Rivera-Bustamante; J. S. Semancik

1989-01-01

373

Foaming properties of potato proteins recovered by complexation with carboxymethylcellulose  

Microsoft Academic Search

A protein isolate, with a 74.4% (w\\/w) protein content, was recovered from a simulated potato processing plant waste effluent by complexation with carboxymethylcellulose. The protein solubility of the isolate was satisfactory, it decreased in the presence of NaCl, but was not markedly affected by heat treatment. The isolate exhibited remarkable foaming and foam stabilizing properties, compared with lyophilized egg white,

Z Partsia; V Kiosseoglou

2001-01-01

374

Soft magnetic properties of nanocrystalline Fe 100- xSi x (15< x<34) alloys  

NASA Astrophysics Data System (ADS)

Nanocrystalline Fe 100- xSi x (15< x<34) alloys have been prepared by melt spinning with high cooling rate. We have found by X-ray diffraction that the basic cubic symmetry could be extended up to 34 at% Si. Around the composition of Fe 2Si, a single-phase metastable B2 structure was found. If the quenching is not properly conducted, traces of hexagonal Fe 5Si 3 appear, which is detrimental to the soft magnetic properties. Our MS, TC, K, Dsp and ? results complement the existing (up to 25 at%) data and their soft magnetic properties are herein presented for the first time. The frequency dependence of the complex permeability in this high Si content region is comparable with that of NiZn ferrite.

Varga, L. K.; Mazaleyrat, F.; Kovac, J.; Kákay, A.

2000-06-01

375

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

PubMed

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

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

2014-04-30

376

A Study of the Magnetic and Thermal Properties of Ln  

SciTech Connect

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

Harada, Daijitsu; Hinatsu, Yukio

2001-05-01

377

Valley properties of doped graphene in a magnetic field  

NASA Astrophysics Data System (ADS)

The aim of this work is to describe the electronic properties of graphene in a constant magnetic field in the long wavelength approximation with random binary disorder, by solving the Soven equation self-consistently. Density of state contributions for different valleys in each sublattice sites are obtained for different values of magnetic field strength showing remarkable differences between K and K' valleys. A band gap is obtained by an asymmetric on-site impurity concentration and the graphene electrons acquire an anomalous magnetic moment, which is opposite in different valleys, which depend highly in the interplay between the impurity band, the band edges and the broadening of the Landau levels. In turn, magnetization as a function of B for different on-site random impurities is computed showing that by decreasing the on-site impurity energy values, maximum magnetization is shifted towards higher values of B which can be used to create and manipulate polarized valley currents. Finally, conductivity and local vertex function are obtained as a function of energy showing that scattering contributions from A and B sublattices differ significantly. Effective medium local two-irreducible vertex is computed showing that scattering from sublattices A and B do not contribute equally, which can be related to weak anti-localization. From these results, it could be possible to explore how the valley pseudospin can be used to create polarized currents by populating asymmetrically the sublattice sites, where the population can be tuned with the applied magnetic field strength.

Ardenghi, Juan Sebastian; Bechthold, Pablo; Gonzalez, Estela; Jasen, Paula; Juan, Alfredo

2015-02-01

378

Structural and magnetic properties of cobalt doped titanium dioxide  

NASA Astrophysics Data System (ADS)

Semiconductor spintronics is a promising new field of study in the ongoing quest to make electronic devices faster, cheaper, and more efficient. While current spintronics utilize the spin property of electrons to achieve greater functionally, the integration of spintronics into conventional semiconductor electronics will lead to advances optoelectronics, quantum computing, and other emerging fields of technology. This integration relies on effective generation; injection, transport, and detection of spin polarized electron current. To these end, mastering synthesis of room temperature ferromagnetic semiconductors is inevitable. In this work, we study the properties of cobalt-implanted titanium dioxide, a room temperature dilute ferromagnetic semiconductor discovered in 2001. The ferromagnetic interaction mechanism is however controversial. By using metal vapor vacuum arc (MEVVA) ion source, different doses of cobalt ions were implanted into anatase structures of titanium dioxide (TiO2) thin films. The TiO2 films which were sputtered on SiO2 (100nm)/Si (110) substrates and rutile structure of TiO2. The cobalt implanted TiO2 thin films were prepared with different atomic fraction and then thermally treated at different temperature after ion implantation. The structural properties of the anatase titanium dioxide were also studied as a comparison to rutile titanium dioxide. Rutherford backscattering spectrometry (RBS) was performed to determine the composition of cobalt. The crystal structure of the thin films and rutile single crystal was mainly anatase as detected in XRD spectra. X-ray photoelectron spectrometry (XPS) and transmission electron microscopy (TEM) were also used in sample analysis. Vibrating sample magnetometer (VSM) was employed to study the magnetic properties of the cobalt implanted films. Ferromagnetic behaviors of these films were observed at room temperature. Cobalt doped anatase TiO2 films show room temperature ferromagnetism. Doping was provided by implantation using a MEVVA ion source. The enhancement of ferromagnetic properties was obtained by post-implantation annealing. The microstructure, magnetic properties and the dependence on the annealing conditions have being studied using various characterization techniques. Interestingly, the output referring to the saturation magnetization per Co atom with a value as high as 3.16 muB/Co atom, exceeds considerably that of the bulk cobalt which suggests that contribution to the overall magnetic behavior is not only a function of the concentration of inherently magnetic elements, but there must exist also sources of magnetisms. One of these sources are oxygen vacancies as discussed within this work. It is also interesting that instead of the more commonly observed hcp structure, the Co nanoclusters are found in fcc structure probably being stabilized by the TiO2 matrix.

Luk, Wing Yan

379

Analysis of the magnetic properties experiment data on Mars: results from Mars Pathfinder  

Microsoft Academic Search

The paper presents the results of a new analysis of the data from the Magnetic Properties Experiment onboard the Mars Pathfinder Spacecraft. The spectral data from the extended visible region of material adhering to the magnets are presented as well as the time dependence of dust accumulation to the magnets. A new model is developed to estimate the magnetic properties

Haraldur Páll Gunnlaugsson

2000-01-01

380

The magnetic properties of Quaternary aeolian dusts and sediments, and their palaeoclimatic significance  

E-print Network

Review The magnetic properties of Quaternary aeolian dusts and sediments, and their palaeoclimatic/or palae- oclimatic information carried by sediment magnetic properties. The most important minerals, the weakly but very magnetically stable minerals, haematite and goethite, form key magnetic tracers

Maher, Barbara

381

Using Solution Phase Self-Assembly to Control the Properties of Magnetic and Magnetoelectric Nanostructures  

NASA Astrophysics Data System (ADS)

Nanostrutured magnetic materials have gained much recent interest because of their application in various electronic systems. These materials, however, often require complex lithography and epitaxy to control the magnetic properties. In this work, solution-phase self-assembly is used to create magnetic and magnetoelectric materials with a variety of nanoscale structures. By engineering the architecture of the system, control over a range of magnetic properties can be realized. The first part of this work focuses on nano-magnetic materials. Here, the organization of nanoscale magnets into different geometries is controlled, and the properties of the systems are studied. In the first chapter, Ni-Cu nanowire stacks are examined to explore the effect of shape anisotropy on the coupling between different elements. This work provides insight into how to design new elements for spin-torque devices. In the next chapter, directed self-assembly of block copolymers is used to create coupled 1D chains of ferromagnetic and superparamagnetic FePt nanoparticles. These nano-patterned are globally aligned on the wafer length-scale using micron-sized lithographic grooves. This system is ideal for studying dipolar coupling between magnetic nanocrystals. Additionally, the processing methods developed here provide a platform for organizing other types of nanomaterials. The second sections explore magnetoelectric materials. These are materials that combine ferromagnetism and ferroelectricity in a coupled manner. One material that does this intrinsically is bismuth ferrite. The first chapter of this section explores ordered nanoporous bismuth ferrite produced by block copolymer templating. It is shown that the ordered porosity of the system creates a unique strain state in the bismuth ferrite, which in turn produces a large change in magnetization upon application of an electric field. Finally, in the last chapter, a nanostructured composite magnetoelectric system is studied. Here, magnetostrictive Ni nanocrystals are coupled to a single-crystalline piezoelectric substrate. The nanocrystals are superparamagnetic and show no net magnetization. Upon application of an electric field, however, strain induced in the piezoelectric substrate strains the lattice of the nanocrystals, creating a preferred magnetic axis along the high strained direction. This locks the magnetization along the strain axis and switches the nanocrystals from a superparamagnetic to a ferromagnetic state.

Schelhas, Laura Theresa

382

Magnetic resonance imaging of the submandibular-sublingual complex.  

PubMed

The submandibular-sublingual complex (SSC) was studied in vivo by magnetic resonance imaging (MRI) at 4.7 and 7.05 Tesla in rat and mouse. A correlation was found between histology and MRI signal. The mainly mucous sublingual gland emitted a more intense signal than the mainly serous submandibular gland. Ventral to the glands, cutis, subcutaneous adipose tissue and two planes of muscular tissue separated by connective laminae were visible in vivo. Autopsy and histology confirmed the in vivo description provided by MRI. The reactivity of the salivary system after pharmacological stimulation was studied in mice at 7.05 Tesla. Stimulation of salivary secretion by pilocarpine nitrate injected in the subcutaneous space ventrally to the SSC resulted in an augmentation of the salivary liquid visible in the oral cavity by MRI. The diffusion of pilocarpine nitrate in the connective tissue located ventrally the SSC and in the glandular parenchyma was also followed in vivo. These results show that MRI is a potentially useful tool for studying the salivary glands in vivo. PMID:8184660

Sbarbati, A; Baldassarri, A; Leclercq, F; Merigo, F; Antonakis, K; Boicelli, A

1994-01-01

383

Magnetic Separation and Magnetic Properties of Low-Grade Manganese Carbonate Ore  

NASA Astrophysics Data System (ADS)

The relation between the magnetic separation behavior and magnetic properties of a low-grade manganese ore was analyzed before and after treatment by direct reduction with coal. It was found that raw ore with an initial average grade of 10.39% Mn and consisting of diamagnetic and paramagnetic minerals can be concentrated by high-intensity magnetic separation to produce a salable product with a grade of 22.75% Mn and a recovery of 89.88%. In contrast, direct reduction of the ore results in a new Mn-Fe oxide phase formed with a combination of ferromagnetic and paramagnetic properties, thereby increasing the magnetic susceptibilities of the ore by almost two orders of magnitude. The grade of Mn for the roasted ore could only be concentrated to 15.49% with a recovery of 66.67%. Therefore, it is concluded that the low-grade manganese ores with antiferromagnetic and paramagnetic (or diamagnetic, but not strongly ferromagnetic) properties could be efficiently beneficiated via high-intensity magnetic separation.

Wu, Y.; Shi, B.; Ge, W.; Yan, C. J.; Yang, X.

2015-02-01

384

Heat capacity, magnetic and lattice dynamic properties of TbMn1-xFexO3  

NASA Astrophysics Data System (ADS)

The effect of substitution of Fe3+ ions by Mn3+ ions on crystal structure, lattice dynamic, heat capacity and magnetic properties in TbMn1-xFexO3 ceramics has been studied. X-ray powder diffraction and Raman spectroscopy revealed that lattice distortion can be mainly attributed to Jahn-Teller distortion and tilting of octahedrons for samples with x < 0.4; for higher Fe concentration, the distortions are dominated by the octahedra tilting with less contribution of the Jahn-Teller effect. The anomalies in heat capacity of parent compounds (TbMnO3 and TbFeO3), which are associated with magnetic transitions, are smeared out by ion substitution. Magnetization measurements indicate that magnetic ordering persists in whole concentration range. The butterfly-type magnetic hysteresis loops suggest that the magnetic ground state of the whole system is complex and thence interesting for next experimental and theoretical studies.

Mihalik, M., Jr.; Mihalik, M.; Fitta, M.; Vavra, M.; Zentková, M.; Vilarinho, R.; Mota, D. A.; Tavares, P.; Agostinho Moreira, J.; Almeida, A.

2015-03-01

385

The correlations between processing parameters and magnetic properties of an iron–resin soft magnetic composite  

Microsoft Academic Search

In this study, internal microstrain of an iron–resin composite produced by powder metallurgy has been calculated using the Williamson–Hall method. The effects of microstrain evolution during different processing conditions on magnetic properties such as coercive force and hysteresis loss have been investigated. The results show that there are regular and similar changes of coercivity and hysteresis loss. Both of these

I. Hemmati; H. R. Madaah Hosseini; A. Kianvash

2006-01-01

386

Magnetic structure and Magnetic transport Properties of Graphene Nanoribbons With Sawtooth Zigzag Edges  

NASA Astrophysics Data System (ADS)

The magnetic structure and magnetic transport properties of hydrogen-passivated sawtooth zigzag-edge graphene nanoribbons (STGNRs) are investigated theoretically. It is found that all-sized ground-state STGNRs are ferromagnetic and always feature magnetic semiconductor properties, whose spin splitting energy gap Eg changes periodically with the width of STGNRs. More importantly, for the STGNR based device, the dual spin-filtering effect with the perfect (100%) spin polarization and high-performance dual spin diode effect with a rectification ratio about 1010 can be predicted. Particularly, a highly effective spin-valve device is likely to be realized, which displays a giant magnetoresistace (MR) approaching 1010%, which is three orders magnitude higher than the value predicted based on the zigzag graphene nanoribbons and six orders magnitude higher than previously reported experimental values for the MgO tunnel junction. Our findings suggest that STGNRs might hold a significant promise for developing spintronic devices.

Wang, D.; Zhang, Z.; Zhu, Z.; Liang, B.

2014-12-01

387

Magnetic structure and Magnetic transport Properties of Graphene Nanoribbons With Sawtooth Zigzag Edges  

PubMed Central

The magnetic structure and magnetic transport properties of hydrogen-passivated sawtooth zigzag-edge graphene nanoribbons (STGNRs) are investigated theoretically. It is found that all-sized ground-state STGNRs are ferromagnetic and always feature magnetic semiconductor properties, whose spin splitting energy gap Eg changes periodically with the width of STGNRs. More importantly, for the STGNR based device, the dual spin-filtering effect with the perfect (100%) spin polarization and high-performance dual spin diode effect with a rectification ratio about 1010 can be predicted. Particularly, a highly effective spin-valve device is likely to be realized, which displays a giant magnetoresistace (MR) approaching 1010%, which is three orders magnitude higher than the value predicted based on the zigzag graphene nanoribbons and six orders magnitude higher than previously reported experimental values for the MgO tunnel junction. Our findings suggest that STGNRs might hold a significant promise for developing spintronic devices. PMID:25533701

Wang, D.; Zhang, Z.; Zhu, Z.; Liang, B.

2014-01-01

388

UNIVERSITY of CALIFORNIA EFFECT OF BISMUTH DOPING ON THE MAGNETIC PROPERTIES  

E-print Network

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

Belanger, David P.

389

The magnetic and microstructural properties of Co-Cr thin films with perpendicular anisotropy  

Microsoft Academic Search

This paper reports measurements of the magnetic properties of dc sputter deposited Co100-xCrx alloy thin films for 0 <= x <= 30 at %. Properties of interest are those obtained from the in-plane and perpendicular hysteresis loops such as magnetization, saturation fields and coercivities. These properties are correlated with the microstructure, crystal structure and, to some extent, the magnetic domain

P. J. Grundy; Mubarak Ali

1983-01-01

390

Nanostructure and magnetic properties of polycrystalline FePdPtMgO Sangki Jeong,a)  

E-print Network

in the literature. In this article, the structure and magnetic properties of polycrystalline FePdPt films on Mg. Magnetic properties were mea- sured using alternating gradient force magnetometry, in fields up to 13­14 kNanostructure and magnetic properties of polycrystalline FePdPt�MgO thin films Sangki Jeong,a) Anup

Laughlin, David E.

391

Investigation of the Properties of Magnetic Films Deposited on Carbon Nitride  

E-print Network

. Giant Magnetoresistance C. Dependence of Magnetic and Transport Behavior on Structural Properties D C. Vibrating Sample Magnetometry IV. Results A. Roughness of Films B. Magnetic Properties V The purpose of this study is to investigate the magnetic and structural properties of nickel films when

Reilly, Anne

392

Magnetic properties of superparamagnetic nanoparticles loaded into silicon nanotubes  

PubMed Central

In this work, the magnetic properties of silicon nanotubes (SiNTs) filled with Fe3O4 nanoparticles (NPs) are investigated. SiNTs with different wall thicknesses of 10 and 70 nm and an inner diameter of approximately 50 nm are prepared and filled with superparamagnetic iron oxide nanoparticles of 4 and 10 nm in diameter. The infiltration process of the NPs into the tubes and dependence on the wall-thickness is described. Furthermore, data from magnetization measurements of the nanocomposite systems are analyzed in terms of iron oxide nanoparticle size dependence. Such biocompatible nanocomposites have potential merit in the field of magnetically guided drug delivery vehicles. PACS 61.46.Fg; 62.23.Pq; 75.75.-c; 75.20.-g PMID:25170336

2014-01-01

393

Discontinuous properties of current-induced magnetic domain wall depinning  

PubMed Central

The current-induced motion of magnetic domain walls (DWs) confined to nanostructures is of great interest for fundamental studies as well as for technological applications in spintronic devices. Here, we present magnetic images showing the depinning properties of pulse-current-driven domain walls in well-shaped Permalloy nanowires obtained using photoemission electron microscopy combined with x-ray magnetic circular dichroism. In the vicinity of the threshold current density (Jth = 4.2 × 1011?A.m?2) for the DW motion, discontinuous DW depinning and motion have been observed as a sequence of “Barkhausen jumps”. A one-dimensional analytical model with a piecewise parabolic pinning potential has been introduced to reproduce the DW hopping between two nearest neighbour sites, which reveals the dynamical nature of the current-driven DW motion in the depinning regime. PMID:24170087

Hu, X. F.; Wu, J.; Niu, D. X.; Chen, L.; Morton, S. A.; Scholl, A.; Huang, Z. C.; Zhai, Y.; Zhang, W.; Will, I.; Xu, Y. B.; Zhang, R.; van der Laan, G.

2013-01-01

394

Synthesis and properties of magnetic iron oxide/platinum nanocomposites  

NASA Astrophysics Data System (ADS)

Iron oxide/platinum nanocomposites have been synthesized by the extractive-pyrolytic method (EPM) involving gradual decomposition of iron capronate and n-trioctylammonium hexachloroplatinate initially produced by solvent extraction. The content of platinum in the composites was 1.2 wt%, 2.4 wt% and 4.8 wt%. Phase composition, morphology and magnetic properties of the produced materials were investigated. XRD analysis and magnetic measurements show that the magnetic phase (magnetite Fe3O4) dominates in a carrier sample produced by the pyrolysis of iron carboxylate, but hematite ?-Fe2O3 exists there as an admixture. Referring to the TEM results, the produced composites contain ultra-disperse platinum particles on the carrier, and the mean size of these varies from 3 nm to 9 nm.

Serga, V.; Maiorov, M.; Kulikova, L.; Krumina, A.; Karashanova, D.

2015-03-01

395

Magnetic nanoparticles supported ionic liquids improve firefly luciferase properties.  

PubMed

Ionic liquids as neoteric solvents, microwave irradiation, and alternative energy source are becoming as a solvent for many enzymatic reactions. We recently showed that the incubation of firefly luciferase from Photinus pyralis with various ionic liquids increased the activity and stability of luciferase. Magnetic nanoparticles supported ionic liquids have been obtained by covalent bonding of ionic liquids-silane on magnetic silica nanoparticles. In the present study, the effects of [?-Fe2O3@SiO2][BMImCl] and [?-Fe2O3@SiO2][BMImI] were investigated on the structural properties and function of luciferase using circular dichroism, fluorescence spectroscopy, and bioluminescence assay. Enzyme activity and structural stability increased in the presence of magnetic nanoparticles supported ionic liquids. Furthermore, the effect of ingredients which were used was not considerable on K(m) value of luciferase for adenosine-5'-triphosphate and also K(m) value for luciferin. PMID:24492953

Noori, Ali Reza; Hosseinkhani, Saman; Ghiasi, Parisa; Akbari, Jafar; Heydari, Akbar

2014-03-01

396

Insights into the control of magnetic coupling in the Mn4(III) complex: from ferromagnetic to antiferromagnetic.  

PubMed

Magnetic coupling interactions of a Mn(III)(4) system are investigated by calculations based on density functional theory combined with a broken-symmetry approach (DFT-BS). Three different interactions including ferromagnetic and antiferromagnetic coupling are concomitant in this complex. This magnetic phenomenon of the complex is due to the different bridging angles between the Mn(III) centers in the three different models and the orbital complementarity of the ?-pzbg and ?-OCH(3) bridging ligands, which is proven by the analyses of the molecular orbitals. According to the analyses of the magneto-structural correlation, it is revealed that the magnetic coupling interaction switches from ferromagnetic to antiferromagnetic at the point of the bridging angle Mn-(?-OCH(3))-Mn = 99°, which is equal to the value in the origin crystal. Significant correlation between the magnetic properties and the component of the d orbitals in these systems shows that the larger contribution of the d(z(2)) orbital corresponds to the larger ferromagnetic coupling interaction. These results should provide a means to control the magnetic coupling of the polynuclear Mn systems, which is instructive for the design of new molecular magnetic materials. PMID:20922243

Wang, Li-Li; Sun, You-Min; Gao, Jun; Lin, Xian-Jie; Liu, Cheng-Bu

2010-11-14

397

Magnetic properties of mantle xenoliths and implications for long wavelength magnetic anomalies  

NASA Astrophysics Data System (ADS)

Unaltered peridotite xenoliths are broadly representative of the lithospheric mantle in both oceanic and continental domains. These peridotites are mainly lherzolites and harzburgites. Other rock types such as dunites, wehrlites and pyroxenites are generally not volumetrically significant. The respective contributions of rock-forming minerals to induced and remanent magnetization in these rocks are currently poorly constrained. This information can be used to assess the significance of long-wavelength magnetic anomalies. It can also provide insights, as an alternate approach to the spinel-olivine-pyroxene oxybarometer, into several important petrologic parameters of the lithospheric mantle including fO2. Forty-nine representative, uncontaminated and non-serpentinized xenoliths have been magnetically investigated. These specimens display contrasting remanent magnetic properties (NRM, Mr, Ms) depending on their tectonic settings, specifically oceanic hot-spot, continental mantle plume, island arc, and craton. The main paramagnetic silicates (olivine, clinopyroxene, orthopyroxene, etc...) typically account for most of the peridotite magnetic properties. The low-field bulk magnetic susceptibility of pristine, unaltered mantle xenoliths is ? 500 +/- 60 x 10-6 [SI] and displays limited variability. The total contribution of paramagnetic silicates to magnetic susceptibility (Kpara-silicates) can be determined from the high-field slope of a saturated hysteresis experiment. Kpara-silicates can also be calculated by adding the respective contributions of individual silicates based on their modes, chemical composition, and the Bohr magneton numbers of individual cations. Silicates account for between 56 and 97% (average ? 85%) of the magnetic susceptibility depending on rock composition. When present, the contribution of chrome spinel, which is paramagnetic in the absence of late-stage exsolution products, remains around 1%. Plagioclase-, spinel- and garnet-lherzolites share similar low-field magnetic properties. The remaining contribution to magnetic susceptibility arises from variable amounts of primary magnetite (and pyrrhotite to a minor extent). These mineral phases, although present in tens to hundreds of ppm only, contribute significantly to the rock magnetic properties because they have large intrinsic magnetic susceptibilities (? 1 to 4 [SI] for magnetite). Stoichiometric magnetite has been identified as microscopic exsolutions in the lattice of olivine and accounts for 2 to 43% (average ? 8%) of the magnetic susceptibility. Whether these pseudo-single domain magnetite grains are in equilibrium with other rock-forming minerals or not is still being investigated. Pyrrhotite (up to 600 ppm in some rare specimens), although detectable in low-temperature magnetic experiments, does not significantly contribute to magnetic susceptibility. The contribution of ferromagnetic minerals, such as magnetite and pyrrhotite, to remanent magnetization (Mr) is significant and varies greatly (over 250x between specimens) with tectonic setting. The fact that all specimens contain primary magnetite suggests that these assemblages equilibrated at least at or above the wustite-magnetite (WM) oxygen buffer and near the fayalite-magnetite-quartz (FMQ) oxygen buffer. The amount of magnetite present in the mantle peridotite assemblage seems to correlate with tectonic setting and may be linked to fO2 in the mantle. The timing of magnetite exsolution in olivine is still poorly understood and may depend on degree of partial melting, rate of cooling to ambient lithospheric temperature, or mantle metasomatic processes due to introduction of hydrous fluids.

Friedman, Sarah A.

2011-12-01

398

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

399

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

SciTech Connect

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

Cuchet, Léa; Rodmacq, Bernard; Auffret, Stéphane; Sousa, Ricardo C.; Dieny, Bernard [SPINTEC, UMR 8191, CEA-INAC/CNRS/UJF-Grenoble 1/Grenoble-INP, 38054 Grenoble Cedex (France)

2014-08-04

400

Structures and magnetic properties of Co-Zr-B magnets studied by first-principles calculations  

E-print Network

The structures and magnetic properties of the Co-Zr-B alloys near the Co5Zr composition were studied using adaptive genetic algorithm and first-principles calculations to guide further experimental effort on optimizing their magnetic performances. Through extensive structural searches, we constructed the contour maps of the energetics and magnetic moments of the Co-Zr-B magnet alloys as a function of composition. We found that the Co-Zr-B system exhibits the same structural motif as the "Co11Zr2" polymorphs, which plays a key role in achieving high coercivity. Boron atoms can either substitute selective cobalt atoms or occupy the interstitial sites. First-principles calculation shows that the magnetocrystalline anisotropy energies can be significantly improved through proper boron doping.

Zhao, Xin; Nguyen, Manh Cuong; Wang, Cai-Zhuang; Ho, Kai-Ming

2015-01-01

401

Magnetic properties of IV-VI compound GeTe based diluted magnetic semiconductors  

NASA Astrophysics Data System (ADS)

Magnetic properties of IV-VI compound GeTe based diluted magnetic semiconductors with 3d transition metals from Ti to Ni have been investigated. Ferromagnetic order is observed for the Cr, Mn, and Fe doped GeTe films, whereas the Ti, V, Co, and Ni doped films are paramagnetic. The ferromagnetic order could give rise to p-d exchange interaction because amplitudes of negative magnetoresistance and the anomalous Hall effect are proportional to that of spontaneous magnetization. The Curie temperatures determined by extrapolating the steep linear part of the temperature dependence of the squared residual magnetization for the Cr, Mn, and Fe doped GeTe films are 12, 47, and 100 K, respectively.

Fukuma, Y.; Asada, H.; Miyashita, J.; Nishimura, N.; Koyanagi, T.

2003-05-01

402

Structural and magnetic properties of chromium doped zinc ferrite  

SciTech Connect

Zinc chromium ferrites with chemical formula ZnCr{sub x}Fe{sub 2?x}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared by Sol - Gel technique. The structural as well as magnetic properties of the synthesized samples have been studied and reported here. The structural characterizations of the samples were analyzed by using X – Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). The single phase spinel cubic structure of all the prepared samples was tested by XRD and FTIR. The particle size was observed to decrease from 18.636 nm to 6.125 nm by chromium doping and induced a tensile strain in all the zinc chromium mixed ferrites. The magnetic properties of few samples (x = 0.0, 0.4, 1.0) were investigated using Vibrating Sample Magnetometer (VSM)

Sebastian, Rintu Mary; Thankachan, Smitha; Xavier, Sheena; Mohammed, E. M., E-mail: emmohammed2005@gmail.com [Research Department of Physics, Maharaja's College, Ernakulam, Kerala (India); Joseph, Shaji [Department of Physic, St. Albert's College, Ernakulam, Kerala (India)

2014-01-28

403

Electronic and magnetic properties of partially open carbon nanotubes.  

PubMed

On the basis of the spin-polarized density functional theory calculations, we demonstrate that partially open carbon nanotubes (CNTs) observed in recent experiments have rich electronic and magnetic properties which depend on the degree of the opening. A partially open armchair CNT is converted from a metal to a semiconductor and then to a spin-polarized semiconductor by increasing the length of the opening on the wall. Spin-polarized states become increasingly more stable than nonmagnetic states as the length of the opening is further increased. In addition, external electric fields or chemical modifications are usable to control the electronic and magnetic properties of the system. We show that half-metallicity may be achieved and the spin current may be controlled by external electric fields or by asymmetric functionalization of the edges of the opening. Our findings suggest that partially open CNTs may offer unique opportunities for the future development of nanoscale electronics and spintronics. PMID:19911795

Huang, Bing; Son, Young-Woo; Kim, Gunn; Duan, Wenhui; Ihm, Jisoon

2009-12-16

404

Segmental inertial properties in dogs determined by magnetic resonance imaging.  

PubMed

Data regarding the segmental inertial properties of the dog are currently unavailable, although such parameters are needed for dynamic analyses of canine motion. The purpose of this study was to measure the segmental inertial properties in three medium sized dogs of average build using magnetic resonance imaging. The parameters included the mass, location of centre of mass and moments of inertia for each body segment. The normalised results will serve as a preliminary foundation for various biomechanical studies in dogs, although further study is required to characterise them for specific dog breeds and to determine how they may be affected by age and gender. PMID:18691919

Amit, T; Gomberg, B R; Milgram, J; Shahar, R

2009-10-01

405

Fermi surface, magnetic, and superconducting properties in actinide compounds  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

406

Switchable molecular magnets  

PubMed Central

Various molecular magnetic compounds whose magnetic properties can be controlled by external stimuli have been developed, including electrochemically, photochemically, and chemically tunable bulk magnets as well as a phototunable antiferromagnetic phase of single chain magnet. In addition, we present tunable paramagnetic mononuclear complexes ranging from spin crossover complexes and valence tautomeric complexes to Co complexes in which orbital angular momentum can be switched. Furthermore, we recently developed several switchable clusters and one-dimensional coordination polymers. The switching of magnetic properties can be achieved by modulating metals, ligands, and molecules/ions in the second sphere of the complexes. PMID:22728438

SATO, Osamu

2012-01-01

407

Structural, dielectric and magnetic properties of Ni substituted zinc ferrite  

NASA Astrophysics Data System (ADS)

NixZn1-xFe2O4 ferrite has been synthesized by the ceramic method using Ni CO3, ZnO, Fe2O3 precursors. The influence of Ni content on the structural, morphological, electrical and magnetic properties of NixZn1-xFe2O4 ferrites is studied. The X-ray diffraction (XRD) analysis reveals that the samples are polycrystalline with spinel cubic structure. The SEM images of NixZn1-xFe2O4 ferrite show that the grain size decreases with an increase in the Ni content. The tetrahedral and octahedral vibrations in the samples are studied by IR spectra. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. Conduction mechanism due to polarons has been analyzed by measuring the AC conductivity. Impedance spectroscopy is used to study the electrical behavior. Magnetic properties of NixZn1-xFe2O4 are studied by using hysteresis loop measurement. The maximum value of saturation magnetization of 132.8 emu/g obtained for the composition, x=0.8, is attributed to magnetic moment of Fe3+ ions.

Kumbhar, S. S.; Mahadik, M. A.; Mohite, V. S.; Rajpure, K. Y.; Kim, J. H.; Moholkar, A. V.; Bhosale, C. H.

2014-08-01

408

The X-ray properties of magnetic massive stars  

NASA Astrophysics Data System (ADS)

Early-type stars are well-known to be sources of soft X-rays. However, this high-energy emission can be supplemented by bright and hard X-rays when magnetically confined winds are present. In an attempt to clarify the systematics of the observed X-ray properties of this phenomenon, a large series of Chandra and XMM observations was analyzed, over 100 exposures of 60% of the known magnetic massive stars listed recently by Petit et al. (2013). It is found that the X-ray luminosity is strongly correlated with mass-loss rate, in agreement with predictions of magnetically confined wind models, though the predictions of higher temperature are not always verified. We also investigated the behaviour of other X-ray properties (absorption, variability), yielding additional constraints on models. This work not only advances our knowledge of the X-ray emission of massive stars, but also suggests new observational and theoretical avenues to further explore magnetically confined winds.

Nazé, Yaël; Petit, Vé