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1

Complex Structure of Triangular Graphene: Electronic, Magnetic and Electromechanical Properties  

Microsoft Academic Search

We have investigated electronic and magnetic properties of graphene nanodisks (nanosize triangular graphene) as well as electromechanical properties of graphene nanojunctions. Nanodisks are nanomagnets made of graphene, which are robust against perturbation such as impurities and lattice defects, where the ferromagnetic order is assured by Lieb's theorem. We can generate a spin current by spin filter, and manipulate it by

Motohiko Ezawa

2011-01-01

2

Magnetic Properties and Moessbauer Spectra of Several Iron(III) Dicarboxylic Acid Complexes.  

National Technical Information Service (NTIS)

Polymeric iron (III) complexes of malonic, succinic, furmaric, and phthalic acids have been prepared and studied by variable-temperature (15-300 K) magnetic susceptibility, 57Fe Mossbauer spectroscopy, and infrared spectroscopy. In addition, properties of...

C. T. Dziobkowski J. T. Wrobleski D. B. Brown

1980-01-01

3

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

PubMed

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

Ezawa, Motohiko

2012-01-01

4

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

5

Magnetic properties and valence states of fullerene complexes  

Microsoft Academic Search

As a consequence of the bucky-ball structure of the fullerenes two kinds of fullerene complexes are formed: endohedral and exohedral complexes. The endohedral fullerenes Sc at C82, Y at C82 and La at C82 show ESR spectra with hyperfine splittings resulting from the nuclear spin of the metal ion. Scandium, yttrium and lanthanum are in the 3+ state in the

Anton Bartl; Lothar Dunsch; Juergen Froehner; Gotthard Seifert; Dieter Eckert; Manfred Wolf; Karl-Hartmut Mueller

1997-01-01

6

Magnetic Characteristics Analysis of Permanent Magnet Motor by using Complex Approximation taking account of Two-dimensional Magnetic Properties  

NASA Astrophysics Data System (ADS)

This paper presents a complex E&S modeling, which is developed with a complex approximation for the conventional E&S modeling. The complex E&S modeling is applied to analyze a permanent magnet motor and validity of the complex E&S modeling is demonstrated. The computation time of the complex E&S modeling can be considerably reduced in comparison with that of the conventional E&S modeling.

Zeze, Shingo; Todaka, Takashi; Enokizono, Masato

7

Magnetic properties and spin dynamics of 3d-4f molecular complexes  

NASA Astrophysics Data System (ADS)

We present the magnetic properties of three recently synthesized binuclear molecular complexes [NiNd], [NiGd], and [ZnGd] investigated by dc magnetization and proton nuclear magnetic resonance (NMR) measurements. The high-temperature magnetic properties are related to the independent paramagnetic behavior of the two magnetic metal ions within the binuclear entities both in [NiNd] and [NiGd]. On lowering the temperature, the formation of a magnetic dimer, with a low-spin ground state due to antiferromagnetic interaction (J/kB ? -25 K) between Ni2+ and Nd3+, is found in the case of [NiNd], while in [NiGd], a ferromagnetic interaction (J/kB ? 3.31 K) between the magnetic ions leads to a high-spin (S = 9/2) ground state. The temperature dependence of the proton nuclear spin lattice relaxation rate T1-1 in [NiNd] is driven by the fluctuation of the hyperfine field at the nuclear site due to relaxation of the magnetization. At high temperatures, the independent Ni2+ and Nd3+ spins fluctuate fast, while at low temperatures, we observe a slowing down of the fluctuation in the total magnetization of the dimer because of the insurgence of antiferromagnetic spin correlations. The relaxation mechanism in [NiNd] at low temperatures is interpreted by a single temperature-dependent correlation frequency ?c ? T3.5, which reflects the lifetime broadening of the exchange-coupled spins via spin-phonon interaction. The proton NMR signal in [NiGd] could just be detected at room temperature due to the shortening of relaxation times when T is decreased. The magnetic properties of [ZnGd] are the ones expected from a weakly interacting assembly of isolated moments except for anomalies in the susceptibility and NMR results below 15 K, which currently cannot be explained.

Khuntia, P.; Mariani, M.; Mahajan, A. V.; Lascialfari, A.; Borsa, F.; Pasatoiu, T. D.; Andruh, M.

2011-11-01

8

A model of magnetic and relaxation properties of the mononuclear [Pc2Tb](-)TBA+ complex.  

PubMed

The present work is aimed at the elaboration of the model of magnetic properties and magnetic relaxation in the mononuclear [Pc(2)Tb](-)TBA(+) complex that displays single-molecule magnet properties. We calculate the Stark structure of the ground (7)F(6) term of the Tb(3+) ion in the exchange charge model of the crystal field, taking account for covalence effects. The ground Stark level of the complex possesses the maximum value of the total angular momentum projection, while the energies of the excited Stark levels increase with decreasing |M(J)| values, thus giving rise to a barrier for the reversal of magnetization. The one-phonon transitions between the Stark levels of the Tb(3+) ion induced by electron-vibrational interaction are shown to lead to magnetization relaxation in the [Pc(2)Tb](-)TBA(+) complex. The rates of all possible transitions between the low-lying Stark levels are calculated in the temperature range 14 Kmagnetization, we solve the set of master equations for the populations of the Stark levels. The relaxation time is shown to diminish from 3.2 × 10(-2) s to 1.52 × 10(-4) s as the temperature increases from 27 K to 40 K. The obtained values of the relaxation time are in satisfactory agreement with the observed ones. The developed model also provides satisfactory description of the dc-magnetic data and paramagnetic shifts. PMID:23013596

Reu, O S; Palii, A V; Ostrovsky, S M; Tregenna-Piggott, P L W; Klokishner, S I

2012-09-26

9

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

2013-01-07

10

Theoretical Investigation of Electric and Magnetic Properties of Benzene-Vanadium Sandwich Complex Chain  

NASA Astrophysics Data System (ADS)

We investigate the electric and magnetic properties of a benzene-vanadium complex chain [V(C6H6)]?. By performing first principles calculation based on the spin-polarized density functional theory, we find that this system shows a half metallic ferromagnetic behavior, i.e., majority-spin (spin-up) electrons have a semiconducting band gap, while minority-spin (spin-down) electrons are metallic. We suggest that this ferromagnetic order is due to a double-exchange mechanism.

Rahman, Md. Mahmudur; Kasai, Hideaki; Dy, Eben Sy

2005-11-01

11

A dicopper complex with distant metal centers. Structure, magnetic properties, electrochemistry and catecholase activity  

Microsoft Academic Search

The crystal structure and magnetic properties of a dinuclear copper(II) complex of the ligand [2,8-dimethyl-5,11-di-(dimethylethyleneamine) 1,4,5,6,7,10,11,12-octahydroimidazo [4,5-h] imidazo [4,5-c] [1,6]diazecine] dimeim have been investigated. Also, its catecholase activity has been explored in different solvent mixtures: MeCN\\/H2O and OH\\/H2O, each at several pH values. In CH3OH\\/H2O, where the activity was superior, the optimal pH value for the catalytic activity was found

Laura Gasque; Víctor Manuel Ugalde-Saldívar; Ingrid Membrillo; Juan Olguín; Edgar Mijangos; Sylvain Bernès; Ignacio González

2008-01-01

12

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

13

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.

14

A dicopper complex with distant metal centers. Structure, magnetic properties, electrochemistry and catecholase activity.  

PubMed

The crystal structure and magnetic properties of a dinuclear copper(II) complex of the ligand [2,8-dimethyl-5,11-di-(dimethylethyleneamine) 1,4,5,6,7,10,11,12-octahydroimidazo [4,5-h] imidazo [4,5-c] [1,6]diazecine] dimeim have been investigated. Also, its catecholase activity has been explored in different solvent mixtures: MeCN/H2O and OH/H2O, each at several pH values. In CH3OH/H2O, where the activity was superior, the optimal pH value for the catalytic activity was found to be lower than in CH3CN/H2O. The study of the complex's electrochemical behavior (cyclic voltammetry) which was also investigated in these various media, revealed that although an increase in pH in both solvent mixtures results in an increase both in Me oxidizing power (E(1/2)) and reversibility (ipa/ipc) the change of solvent system seems to be a more influencing factor. The superior catalytic activity found in MeOH/H2O pH=8.0, is associated with a significantly more reversible behavior displayed in this medium. Potentiometric determination of the overall formation constant and three successive pKas for the complex, suggest the formation of stable hydroxo complexes which could be the catalytically active species. PMID:18291531

Gasque, Laura; Ugalde-Saldívar, Víctor Manuel; Membrillo, Ingrid; Olguín, Juan; Mijangos, Edgar; Bernès, Sylvain; González, Ignacio

2008-01-11

15

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

SciTech Connect

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

Liu Fuchen, E-mail: fuchenliutj@yahoo.co [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Xue Min; Wang Haichao [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Ouyang Jie, E-mail: ouyang@tjut.edu.c [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China)

2010-09-15

16

New tetranuclear Cu(II) complexes: synthesis, structure, and magnetic properties.  

PubMed

The synthesis, structure, and magnetic properties of two new tetranuclear Cu(II) complexes containing N,N,N',N'-tetraethylpyridine-2,6-dithiocarboxamide (S-dept) of formula [Cu(2)Cl(2)(mu-S-dept)(2)][Cu(2)Cl(4)(mu-Cl)(2)] (1) and [Cu(2)(mu-Cl)(2)(S-dept)(2)][CuCl(3)(EtOH)](2) (2) are reported. Their X-ray crystal structures reveal that the complexes are composed of anionic and cationic dimers, that in both cases contain the metal centers which interact via Coulombic and/or hydrogen bonding interactions. In both cases, the Cu centers in the anionic moieties adopt a slightly distorted tetrahedral geometry whereas for the cationic moieties they adopt a square-pyramidal type of geometry. Magnetic susceptibility data show that compounds 1 and 2 present an overall antiferromagnetic behavior arising from the contribution of both anionic and cationic moieties. For 1, the best fit obtained gave J(1) = -2.62 +/- 0.19 cm(-1), J(2) = -19.54 +/- 0.47 cm(-1), and g(2) = 2.164 +/- 0.004 cm(-1) (R = 8.28 x 10(-5)) whereas for 2 it gave J(1) = 4.48 +/- 2.73 cm(-1), g(1) = 2.20 +/- 0.03, J(2) = -11.26 +/- 2.01 cm(-1), and g(2) = 2.10 +/- 0.03 (R = 1.15 x 10(-4)). The nature of the superexchange pathways in 1 and 2 is discussed on the basis of structural, magnetic, and molecular orbital considerations. Theoretical calculations are performed at the extended Huckel level in order to obtain their molecular orbitals and energies using their crystallographic data. PMID:15476369

Kapoor, Ramesh; Kataria, Ashok; Venugopalan, Paloth; Kapoor, Pratibha; Corbella, Montserrat; Rodríguez, Montserrat; Romero, Isabel; Llobet, Antoni

2004-10-18

17

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

PubMed

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

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

2007-07-10

18

Theoretical description of the magnetic properties of ?3-hydroxo bridged trinuclear copper(II) complexes.  

PubMed

A theoretical study of the magnetic properties, using density functional theory, of a family of trinuclear ?3-OH copper(II) complexes reported in the literature is presented. The reported X-ray crystal structures of [Cu3(?3-OH)(aat)3(H2O)3](NO3)2 · H2O (HUKDUM), where aat: 3-acetylamine-1,2,4-triazole; [Cu3(?3-OH)(aaat)3(H2SO4)(HSO4)(H2O)] (HUKDOG), where aaat: 3-acetylamine-5-amine-1,2,4-triazole; [Cu3(?3-OH)(PhPyCNO)3(tchlphac)2] (HOHQUR), where PhPyCNO: phenyl 2-pyridyl-ketoxime and tchlphac: acid 2,4,5-trichlorophenoxyacetic; [Cu3(?3-OH)(PhPyCNO)3(NO3)2(CH3OH)] (ILEGEM); [Cu3(?3-OH)(pz)3(Hpz)3(ClO4)2] (QOPJIP), where Hpz = pyrazole; [Cu3(?3-OH)(pz)3(Hpz)(Me3CCOO)2] ? 2Me3CCOOH (DEFSEN) and [Cu3(?3-OH)(8-amino-4-methyl-5-azaoct-3-en-2-one)3][CuI3] (RITXUO), were used in the calculations. The magnetic exchange constants were calculated using the broken-symmetry approach. The calculated J values are for HUKDUM J1 = -68.6 cm(-1), J2 = -69.9 cm(-1), J3 = -70.4 cm(-1); for HUKDOG, J1 = -73.5 cm(-1), J2 = -58.9 cm(-1), J3 = -62.1 cm(-1); for HOHQUR J1 = -128.3 cm(-1), J2 = -134.1 cm(-1), J3 = -120.4 cm(-1); for ILEGEM J1 = -151.6 cm(-1), J2 = -173.9 cm(-1), J3 = -186.9 cm(-1); for QOPJIP J1 = -118.3 cm(-1), J2 = -106.0 cm(-1), J3 = -120.6 cm(-1); for DEFSEN J1 = -74.9 cm(-1), J2 = -64.0 cm(-1), J3 = -57.7 cm(-1) and for RITXUO J1 = -10.9 cm(-1), J2 = +14.3 cm(-1), J3 = -35.4 cm(-1). The Kahn-Briat model was used to correlate the calculated magnetic properties with the overlap of the magnetic orbitals. Spin density surfaces show that the delocalization mechanism is predominant in all the studied compounds. PMID:23224799

Cañon-Mancisidor, Walter; Spodine, Evgenia; Paredes-Garcia, Veronica; Venegas-Yazigi, Diego

2012-12-07

19

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

Microsoft Academic Search

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

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

2010-01-01

20

Electronic and magnetic properties of iron (III) dinuclear complexes with carboxylate bridges  

Microsoft Academic Search

A series of dinuclear iron (III) complexes with carboxylate bridges, of the type [Fe2L2(H20)4](NO3)2(H2O)m (m=1–3), where L=Schiff base derived from L-?-amino acids and salicylaldehyde have been prepared and characterised by different spectroscopic techniques, magnetic susceptibility, conductivity, and electrochemical measurements. The dimeric iron complexes contain hexacoordinated iron (III), with the metal ion surrounded by water molecules, the salicylidenimine ligand, and the

Verónica Paredes-Garc??a; Ramón O. Latorre; Evgenia Spodine

2004-01-01

21

The synthesis, spectral and magnetic properties of the complexes of chromium with chrysenequinone and chrysenequinonemonoxime1  

NASA Astrophysics Data System (ADS)

Reactions of the chromium hexacarbonyl with chrysenequinone and chrysenequinonemonoxime gave the tris(chrysenesemiquinone)chronium(III), Cr(ChrySQ) 3, and tris(chrysenesemiquinonemonoxime)chromium(III), Cr(ChrySQM) 3, complexes. From the stretching frequencies of the carbonyl groups in the IR spectra of the complexes, it was concluded that the ligands bonded to the metal in the semiquinone form. Also, the electronic absorption spectra of the two complexes showed strong UV bands due to metal-to-ligand charge transfer. The magnetic susceptibility determination for the Cr(ChrySQ) 3 complex at 300 K gave a value of 3.261 × 10 -6 e.m.u.g -1 with an effective magnetic moment (? eff) of 2.55 ? B. Investigation of Cr(ChrySQ) 3 and Cr(ChrySQM) 3 by EPR spectroscopy at room temperature showed isotropic g values of 1.997 and 1.991 for the two complexes, respectively. The isotropic g values are greater than those observed previously for various osemiquinone chromium complexes. Chrysenequinonemonoxime reacted with Cr(NO 3) 3 to give the bis(chrysenequinonemonoximato) (chrysenequinonemonoxime)chromium(III)nitrate. Spectroscopic studies of the complex suggested that the chrysenequinonemonoxime ligand is attached to the metal in both nitroso and oxime forms. Examination of the chromium complexes by cyclic voltammetry showed some reversible or quasireversible redox reactions due to tautomeric interconversions of the semiquinone—catechol couples through electron transfer.

Ramadan, Ramadan M.; Mahmoud, Wagiha H.; Attia, Attia S.; El-Shahat, M. F.

1993-01-01

22

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+) (), Eu(3+) (), Tb(3+) () and Dy(3+) ()] 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 , and 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 does not display any emission. The different luminescent intensities and lifetimes among them were further discussed in detail. Moreover, the magnetic properties of complexes were assessed with a special emphasis on the Dy(3+) complex . Alternating-current (ac) magnetic susceptibility measurements indicated that field-induced two-step slow magnetic relaxation processes were observed in , indicating the single-molecule magnet (SMM) behavior of . In addition, the noncentrosymmetric complexes 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

2013-10-15

23

Synthesis, crystal structure, and magnetic properties of oxime-bridged polynuclear Ni(II) and Cu(II) complexes.  

PubMed

Two new polynuclear complexes [Ni6(amox)6(mu6-O)(mu3-OH)2](Cl2).6H2O and [Cu3(amox)3(mu3-OH)(mu3-Cl)](ClO4).4H2O (amox- = anion of 4-amino-4-methyl-2-pentanone oxime) have been synthesized and characterized structurally and magnetically. The Ni(II) complex contains a novel Chinese-lantern-like Ni6 cage centered by an oxo ion. It contains the nearest octahedral Ni(II)...Ni(II) separation (<2.8 A) and exhibits strong antiferromagnetic properties. The Cu(II) complex has a cyclic trinuclear copper(II) core bridged by both mu3-OH(-) and mu3-Cl(-) ions. The magnetic susceptibilities of both antiferromagnetic complexes were fitted by using approximate models. PMID:15679406

Jiang, Yun-Bo; Kou, Hui-Zhong; Wang, Ru-Ji; Cui, Ai-Li; Ribas, Joan

2005-02-01

24

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

Microsoft Academic Search

Influence of chemical substitution in the FeII 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

Atsushi Suzuki; Motoi Iguchi; Takeo Oku; Motoyasu Fujiwara

2010-01-01

25

Ferromagnetic dinuclear mixed-valence Mn(II)/Mn(III) complexes: building blocks for the higher nuclearity complexes. structure, magnetic properties, and density functional theory calculations.  

PubMed

A series of six mixed-valence Mn(II)/Mn(III) dinuclear complexes were synthesized and characterized by X-ray diffraction. The reactivity of the complexes was surveyed, and structures of three additional trinuclear mixed-valence Mn(III)/Mn(II)/Mn(III) species were resolved. The magnetic properties of the complexes were studied in detail both experimentally and theoretically. All dinuclear complexes show ferromagnetic intramolecular interactions, which were justified on the basis of the electronic structures of the Mn(II) and Mn(III) ions. The large Mn(II)-O-Mn(III) bond angle and small distortion of the Mn(II) cation from the ideal square pyramidal geometry were shown to enhance the ferromagnetic interactions since these geometrical conditions seem to favor the orthogonal arrangement of the magnetic orbitals. PMID:23363337

Hänninen, Mikko M; Välivaara, Juha; Mota, Antonio J; Colacio, Enrique; Lloret, Francesc; Sillanpää, Reijo

2013-01-30

26

Magnetic, electrochemical and spectroscopic properties of iron(III) amine-bis(phenolate) halide complexes.  

PubMed

Eight new iron(III) amine-bis(phenolate) complexes are reported. The reaction of anhydrous FeX(3) salts (where X = Cl or Br) with the diprotonated tripodal tetradentate ligands 2-tetrahydrofurfurylamino-N,N-bis(2-methylene-4,6-di-tert-butylphenol), H(2)L1, 2-tetrahydrofurfurylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenol), H(2)L2, and 2-methoxyethylamino-N,N-bis(2-methylene-4,6-di-tert-butylphenol), H(2)L3, 2-methoxyethylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenol), H(2)L4 produces the trigonal bipyramidal iron(III) complexes, L1FeCl (1a), L1FeBr (1b), L2FeCl (2a), L2FeBr (2b), L3FeCl (3a), L3FeBr (3b), L4FeCl (4a), and L4FeBr (4b). All complexes have been characterized using electronic absorption spectroscopy, cyclic voltammetry and room temperature magnetic measurements. Variable temperature magnetic data were acquired for complexes 2b, 3a and 4b. Variable temperature Mössbauer spectra were obtained for 2b, 3a and 4b. Single crystal X-ray molecular structures have been determined for proligand H(2)L4 and complexes 1b, 2b, and 4b. PMID:22388465

Dean, Rebecca K; Fowler, Candace I; Hasan, Kamrul; Kerman, Kagan; Kwong, Philip; Trudel, Simon; Leznoff, Daniel B; Kraatz, Heinz-Bernard; Dawe, Louise N; Kozak, Christopher M

2012-03-02

27

[Pharmacological properties of complex iron oxide nanoparticles entering in magnetic resonance tomography contrast agent].  

PubMed

A colloidal solution of iron oxide nanoparticles has been obtained that ensures an increase in the accuracy of diagnostic information from magnetic resonance tomography (MRT) due to the acceleration of proton relaxation in tissues, which improves the contrast of T1- and T2-weighed images. Improved visualization of small vessels in rat brain has been observed after intravenous injection of 0.1 ml solution containing 5.0 mg of contrasting iron nanoparticles. The paramagnetic properties of iron oxide nanoparticles were studied by the method of proton relaxation, and their size was determined by the method of transmission electron microscopy. The toxic properties ofnanoparticles were determined by their effect on cultured HeLa cells (MTT test). It is recommended to use a colloidal solution of superparamagnetic nanoparticles (size, 8.2 nm) for obtaining a pharmaceutical form of the new magnetic-resonance contrast medium Ferotrast. PMID:20726347

Akopdzhanov, A G; Sergeev, A I; Manvelov, E V; Seme?kin, A V; Naumenko, V Iu; Panov, V O; Bykov, I V; Shimanovski?, N L

2010-06-01

28

Direct comparison of the magnetic and electronic properties of samarocene and ytterbocene terpyridine complexes.  

PubMed

A new complex, Cp* 2Sm(tpy) ( 1, where Cp* = C 5Me 5, tpy = 2,2':6',2''-terpyridine) and its one-electron oxidized congener [Cp* 2Sm(tpy)]PF 6 ([ 1] (+)) have been synthesized and characterized with the aim of comparing their electronic and magnetic behavior to the known ytterbium analogues: Cp* 2Yb(tpy) ( 2) and [Cp* 2Yb(tpy)]OTf ([ 2] ( + )). These new samarium complexes have been characterized using single-crystal X-ray diffraction, (1)H NMR spectroscopy, cyclic voltammetry, optical spectroscopy, and bulk magnetic susceptibility measurements. All data for 1 indicate a Sm(III)-tpy* (-)[(4f) (5)-(pi*) (1)] ground-state electronic configuration similar to that found previously for 2 [(4f) (13)-(pi*) (1)]. Structural comparisons reveal that there are no significant changes in the overall geometries associated with the neutral and cationic samarium and ytterbium congeners aside from those anticipated based upon the lanthanide contraction. The redox potentials for the divalent Cp* 2Ln(THF) n precursors ( E 1/2(Sm (2+)) = -2.12 V, E 1/2(Yb (2+)) = -1.48 V) are consistent with established trends, the redox potentials (metal-based reduction and ligand-based oxidation) for 1 are nearly identical to those for 2. The correlation in the optical spectra of 1 and 2 is excellent, as expected for this ligand-radical based electronic structural assignment, but there does appear to be a red-shift ( approximately 400 cm (-1)) in all of the bands of 1 relative to those of 2 that suggests a slightly greater stabilization of the pi* level(s) in the samarium(III) complex compared to that in the ytterbium(III) complex. Similar spectroscopic overlap is observed for the monocationic complexes [ 1] (+) and [ 2] (+). Bulk magnetic susceptibility measurements for 1 reveal significantly different behavior than that of 2 due to differences in the electronic-state structure of the two metal ions. The implications of these differences in magnetic behavior are discussed. PMID:18540594

Veauthier, Jacqueline M; Schelter, Eric J; Carlson, Christin N; Scott, Brian L; Da Re, Ryan E; Thompson, J D; Kiplinger, Jaqueline L; Morris, David E; John, Kevin D

2008-06-10

29

Mixed bridged dinuclear Ni(II) complexes: synthesis, structure, magnetic properties and DFT study.  

PubMed

The green coloured micro-phenoxo, micro-chloro and micro-phenoxo, micro(1,1)-azido bridged complexes of formula [Ni2(L)(Cl)(H2O)] x (C2H5)2O, 1 x (C2H5)2O, and [Ni2(L)(N3)(H2O)] x CH3OH x H2O, 2 x CH3OH x H2O have been synthesized, where L3- is the deprotonated form of 2,6-bis[N-(2-hydroxybenzyl)-N-{2-(dimethylamino)ethyl}aminomethyl]-4-methylphenol, H(3)L. In the complexes, one nickel(II) center has distorted square pyramidal (tau = 0.18 and 0.15) and other one has distorted octrahedral geometry. Both the complexes display a couple of one electron anodic responses near 0.70 and 1.10 V. Complexes 1 and 2 show weak antiferro and ferromagnetic interactions respectively. The calculated J value using broken symmetry DFT method is consistent with the experimentally observed value. Moreover, the calculation also reveals that the antiferromagnetic interaction between the Ni(II) centers takes place via the phenoxo bridge while that of ferromagnetic interaction is through the azido and chloro group. The presence of competitive interaction in the molecule reduces the overall magnetic behavior of the complex. PMID:19030615

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

2008-10-09

30

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

NASA Astrophysics Data System (ADS)

Influence of chemical substitution in the FeII 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

31

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

NASA Astrophysics Data System (ADS)

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

Zalich, Michael Andrew

32

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

PubMed

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

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

2013-02-01

33

Spectroscopic and magnetic properties of a Ni(II) complex with citric acid  

Microsoft Academic Search

The complex compound K2[Ni(cit)(H2O)2]24H2O (cit = triionized citrate ion) seems to be a good model for the investigation of Ni(II)\\/citrate interactions that are of\\u000a interest in relation to nickel metabolism and bioaccumulation. Its infrared and Raman spectra were recorded and analyzed on\\u000a the basis of its structural peculiarities. The magnetic susceptibility, investigated in the temperature range between 1.9\\u000a and 300

M. G. Bovi Mitre; N. R. Wierna; C. C. Wagner; E. J. Baran

2000-01-01

34

Syntheses, structures, and magnetic properties of seven-coordinate lanthanide porphyrinate or phthalocyaninate complexes with Kläui's tripodal ligand.  

PubMed

A series of seven-coordinate mononuclear lanthanide(III) complexes of the general formula [(TPP)Ln(L(OEt))]·0.25H2O and [(Pc)Ln(L(OEt))] (Ln(3+) = Dy(3+), Tb(3+), Ho(3+), and Gd(3+); TPP = 5,10,15,20-tetraphenylporphyrinate; Pc = phthalocyaninate; L(OEt)(-) = [(?(5)-C5H5)Co(P(=O)(OEt)2)3](-)) are synthesized on the basis of the tripodal ligand L(OEt)(-) and either porphyrin or phthalocyanine ligands. All of the complexes are characterized by X-ray crystallography and by static and dynamic magnetic measurements. The Dy and Tb complexes show the field-induced slow relaxation of magnetization, and they are interesting seven-coordinate single-lanthanide-based SMMs. The magnetic relaxation properties of these double-decker sandwich complexes are influenced by the local molecular symmetry and are sensitive to subtle distortions of the coordination geometry of the paramagnetic lanthanide ions, such as metal-to-plane distances, plane center distances, and bending angles. PMID:23692376

Gao, Feng; Yao, Min-Xia; Li, Yu-Yang; Li, Yi-Zhi; Song, You; Zuo, Jing-Lin

2013-05-21

35

Magnetic properties of iron dextran  

NASA Astrophysics Data System (ADS)

The magnetic properties of a freeze-dried iron dextran complex have been studied using Mössbauer spectroscopy and DC magnetisation. The Mössbauer spectra show superparamagnetic relaxation with the onset of superparamagnetic blocking occurring close to 120 K.

Kilcoyne, S. H.; Gorisek, A.

1998-01-01

36

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

37

Structural, Magnetic and Electronic Properties of the Sr2CoNbO6 Complex Perovskite  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

38

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

2007-01-23

39

Spectroscopic and magnetic properties of an iodo Co(I) tripodal phosphine complex.  

PubMed

Reaction of the tripodal phosphine ligand 1,1,1-tris((diphenylphosphino)phenyl)ethane (PhP3) with CoI(2) spontaneously generates a one-electron reduced complex, [(PhP3)Co(I)(I)] (1). The crystal structure of 1 reveals a distorted tetrahedral environment, with an apical Co-I bond distance of ~2.52 Å. Co(II/I) redox occurs at an unusually high potential (+0.38 V vs. SCE). The electronic absorption spectrum of 1 exhibits an MLCT peak at 320 nm (? = 8790 M(-1) cm(-1)) and a d-d feature at 850 nm (? = 840 M(-1) cm(-1)). Two more d-d bands are observed in the NIR region, 8650 (? = 450) and 7950 cm(-1) (? = 430 M(-1) cm(-1)). Temperature dependent magnetic measurements (SQUID) on 1 (solid state, 20-300 K) give ?(eff) = 2.99(6) ?(B), consistent with an S = 1 ground state. Magnetic susceptibilities below 20 K are consistent with a zero field splitting (zfs) |D| = 8 cm(-1). DFT calculations also support a spin-triplet ground state for 1, as optimized (6-31G*/PW91) geometries (S = 1) closely match the X-ray structure. EPR measurements performed in parallel mode (X-band; 0-15,000 G, 15 K) on polycrystalline 1 or frozen solutions of 1 (THF/toluene) exhibit a feature at g? 4 that arises from a (?m = 2) transition within the M(S) = <+1,-1> manifold. Below 10 K, the EPR signal decreases significantly, consistent with a solution zfs parameter (|D|? 8 cm(-1)) similar to that obtained from SQUID measurements. Our work provides an EPR signature for high-spin Co(I) in trigonal ligation. PMID:22903546

Rose, Michael J; Bellone, Donatela E; Di Bilio, Angel J; Gray, Harry B

2012-08-20

40

Structure, magnetic properties and nuclease activity of pyridine-2-carbaldehyde thiosemicarbazonecopper(II) complexes.  

PubMed

New complexes of formulae [Cu(HL(2))(H(2)O)(NO(3))](NO(3)) (1), [{Cu(L(1))(tfa)}(2)] (2), [{Cu(L(1))}(2)(pz)](ClO(4))(2) (3) and {[{Cu(L(1))}(2)(dca)](ClO(4))}(n) (4), where HL(1)=pyridine-2-carbaldehyde thiosemicarbazone, HL(2)=pyridine-2-carbaldehyde 4N-methylthiosemicarbazone, Htfa=trifluoroacetic acid (CF(3)COOH), pz=pyrazine (C(4)H(4)N(2)) and dca=dicyanamide [N(CN)(2)](-), have been synthesized and characterized. The crystal structures of these compounds are built up of monomers (1), dinuclear entities with the metal centers bridged through the non-thiosemicarbazone coligand (2 and 3) and 1D chains of dimers (4). In all the cases, square-pyramidal copper(II) ions are present, except for the square-planar ones in 3. Magnetic measurements show antiferromagnetic couplings in 2, 3 and 4. The susceptibility data were fitted by the Bleaney-Bowers' equation for copper(II) dimers derived from H=-2JS(1)S(2) being the obtained J/k values -4.8, -4.3 and -5.1K for compounds 2-4, respectively. The magnetic susceptibility of the already known [{Cu(HL(1))(tfa)}(2)](tfa)(2) compound has been also measured for the first time. The J/k value is -0.3K, lower than that in 2. The nuclease activity of 3 and 4 has been analyzed. PMID:18692903

Gómez-Saiz, Patricia; Gil-García, Rubén; Maestro, Miguel A; Pizarro, José Luis; Arriortua, María Isabel; Lezama, Luis; Rojo, Teófilo; González-Alvarez, Marta; Borrás, Joaquín; García-Tojal, Javier

2008-07-01

41

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

42

A trinuclear copper(II) cryptate and its ?3-CO3 cascade complex: thermodynamics, structural and magnetic properties.  

PubMed

The 2,4,6-triethylbenzene-capped hexaamine macrobicycle with pyridyl spacers (pyr) was able to coordinate three copper(II) ions within its cavity. Potentiometric studies performed at 298.2 K in MeOH/H(2)O (50:50 v/v) and at ionic strength 0.10 mol dm(-3) in KNO(3) revealed that trinuclear species predominate in solution from pH 5.0, the hydroxo complexes being the main species, which start forming at unusual very low pH values. The single-crystal X-ray determination of the trinuclear complex showed that the three copper centres have square-planar geometry, arranged in an almost equilateral triangle, and have carbonate bridging the three metal centres. The presence of carbonate resulted from fixation of atmospheric CO(2). The present study represents the first ?(3)-CO(3)-bridged trinuclear copper(II) complex located in the interior of a macrobicyclic cavity. The magnetic data of [Cu(3)(pyr)(?(3)-CO(3))]·(ClO(4))(4) showed ferromagnetic intramolecular interactions [J=3.80 cm(-1), based on the Hamiltonian H=-J(S(1)S(2)+S(2)S(3)+S(1)S(3))] yielding a spin quartet, S=3/2, ground state. Density functional calculations on the experimental geometry of the trinuclear complex showed that the ferromagnetic nature of the magnetic coupling can be attributed to the syn-anti conformation of the carbonato bridge, and a magneto-structural correlation, based on the different conformations (syn-anti, syn-syn and anti-anti), is presented. The interesting properties observed, namely the lowering of the pK(a) of coordinated water molecules to unusual values and the good fit of the carbonate anion between the copper centres, derive from the special architecture of pyr. PMID:21905134

Mateus, Pedro; Delgado, Rita; Lloret, Francesc; Cano, Joan; Brandão, Paula; Félix, Vítor

2011-08-23

43

Synthesis, characterization and magnetic properties of new homotrinuclear copper(II) complexes  

Microsoft Academic Search

Two new mononuclear bis(oxamato) complexes with the formula [nBu4N]2[M(nabo)] M=Ni (4), Cu (5), with nabo=2,3-naphthalene-bis(oxamato) have been synthesized as precursors for trinuclear oxamato-bridged transition metal complexes. Starting from 5 the homo-trinuclear complex [Cu3(nabo)(pmdta)2(BF4)](BF4)·MeCN·Et2O (7), with pmdta=N,N,N?,N?,N?-pentamethyldiethylenetriamine, has been prepared. The central N,N?-2,3-naphthalene bridge of 7 is so far the most extended ?-conjugated bridge of trinuclear bis(oxamato) type transition metal complexes.

Tobias Rüffer; Björn Bräuer; Annie K. Powell; Ian Hewitt; Georgeta Salvan

2007-01-01

44

A new ? 1,5-dicyanamide bridged cyclic tetranuclear copper (II) complex with 1,5,9-triazacycledodecane ligands: structure, ESR spectroscopic and magnetic properties  

Microsoft Academic Search

The tetranuclear complex [Cu2L2(dca)2(ClO4)2]2 (1) (L=1,5,9-triazacyclododecane, dca=dicyanamide [N(CN)2]?) has been synthesized and its crystal structure, ESR spectra and magnetic properties determined. The complex contains a tetranuclear copper (II) moiety in which two dimeric units are bridged by two dca ligands. In each dimeric moiety the two copper (II) ions are bridged by one ?1,5-dicyanamide ligand. Magnetic susceptibilities for the complex

Wen Gu; He-Dong Bian; Jing-Yuan Xu; Zhan-Quan Liu; Peng Cheng; Shi-Ping Yan; Dai-Zheng Liao; Zong-Hui Jiang

2003-01-01

45

Vapochromic ionic liquids from metal-chelate complexes exhibiting reversible changes in color, thermal, and magnetic properties.  

PubMed

Vapor- and gas-responsive ionic liquids (ILs) comprised of cationic metal-chelate complexes and bis(trifluoromethanesulfonyl)imide (Tf(2)N) have been prepared, namely, [Cu(acac)(BuMe(3)en)][Tf(2)N] (1?a), [Cu(Bu-acac)(BuMe(3)en)][Tf(2)N] (1?b), [Cu(C(12)-acac)(Me(4)en)][Tf(2)N] (1?c), [Cu(acac)(Me(4)en)][Tf(2)N] (1?d), and [Ni(acac)(BuMe(3)en)][Tf(2)N] (2?a) (acac = acetylacetonate, Bu-acac = 3-butyl-2,4-pentanedionate, C(12)-acac = 3-dodecyl-2,4-pentanedionate, BuMe(3)en = N-butyl-N,N',N'-tetramethylethylenediamine, and Me(4)en = N,N,N',N'-trimethylethylenediamine). These ILs exhibited reversible changes in color, thermal properties, and magnetic properties in response to organic vapors and gases. The Cu(II)-containing ILs are purple and turn blue-purple to green when exposed to organic vapors, such as acetonitrile, methanol, and DMSO, or ammonia gas. The color change is based on the coordination of the vapor molecules to the cation, and the resultant colors depend on the coordination strength (donor number, DN) of the vapor molecules. The vapor absorption caused changes in the melting points and viscosities, leading to alteration in the phase behaviors. The IL with a long alkyl chain (1?d) transitioned from a purple solid to a brown liquid at its melting point. The Ni(II)-containing IL (2?a) is a dark red diamagnetic liquid, which turned into a green paramagnetic liquid by absorbing vapors with high DN. Based on the equilibrium shift from four- to six-coordinated species, the liquid exhibited thermochromism and temperature-dependent magnetic susceptibility after absorbing methanol. PMID:22915372

Funasako, Yusuke; Mochida, Tomoyuki; Takahashi, Kazuyuki; Sakurai, Toshihiro; Ohta, Hitoshi

2012-08-22

46

Theoretical studies of electronic structures, magnetic properties and electron conductivities of one-dimensional Nin (n = 3, 5, 7) complexes.  

PubMed

Electronic structures, magnetic properties and electron conductivities of linearly aligned one-dimensional (1-D) Ni(ii)3, Ni(ii)5 and Ni(ii)7 complexes, i.e. [Ni3(dpa)4NCS2], [Ni5(tpda)4X2] (X = Cl, CN, N3, NCS) and [Ni7(teptra)4Cl2], are systematically investigated by the broken-symmetry B3LYP calculations and simulations based on an elastic scattering Green's function theory. Calculated spin densities appear only at terminal Ni ions, while inner Ni ions are the closed-shell. The calculated effective exchange integrals (Jab) values reproduce well the experimental results that indicate anti-ferromagnetic (AF) interactions between two terminal Ni ions. Natural orbitals and their occupation numbers show that a change in the weak AF couplings by axial ligands in penta-nickel complexes originates in ?-type orbitals. Simulated electron conductivities of [Ni3(dpa)4NCS2] and [Ni5(tpda)4NCS2] semi-quantitatively correspond to the experimental results. By the analyses, it is elucidated that electrons are mainly transmitted by ?-type orbitals, but the bonds between Au and axial ligands are also dominant factors for conductivity. PMID:24091592

Kitagawa, Yasutaka; Matsui, Toru; Nakanishi, Yasuyuki; Shigeta, Yasuteru; Kawakami, Takashi; Okumura, Mitsutaka; Yamaguchi, Kizashi

2013-10-03

47

Synthesis, structure and magnetic properties of an asymmetric dinuclear oxocitratovanadate(IV) complex  

Microsoft Academic Search

Evaporation of an aqueous solution containing VO2+, citric acid and neocuproine (2,9-dimethyl-1,10-phenanthroline=neo) produces blue crystals of (Hneo)3[(VO)2(cit)(Hcit)]·4H2O (1). An X-ray structural analysis showed that 1 consists of a discrete, asymmetric, dinuclear oxocitratovanadate(IV) complex and three neocuproinium cations. The complex contains one six-coordinate V(IV) atom with a distorted octahedral geometry and one five-coordinate V(IV) atom with a distorted square pyramidal geometry.

Suzana Burojevic; Itzhak Shweky; Avi Bino; David A. Summers; Robert C. Thompson

1996-01-01

48

Magnetic and spectral properties of nickel(II) complexes of ligands containing O, N, and S donor atoms  

Microsoft Academic Search

Several complexes of nickel(II) with Schiff bases derived from 3-substituted-4-amino-5-mercapto-1,2,4-triazoles (H2L) have been synthesised. The complexes have a stoichiometry NiL · 2H2O. The bonding of the ligands has been inferred from i.r. spectroscopy. The ligands preserve the thiol in the complexes. Magnetic moments obtained at room temperature and electronic spectra are consistent with octahedral geometry.

Sangamesh A. Patil; Basavantappa M. Badiger; Shreeshail M. Kudari; Vasant H. Kulkarni

1983-01-01

49

Structure, magnetic properties and catecholase activity study of oxo-bridged dinuclear copper(II) complexes  

Microsoft Academic Search

Six alkoxy-bridged dinuclear copper(II) complexes with catecholase-like sites, [Cu(L1)(NCS)]2 (1), [Cu(L2)(CH3CO2)]2·2H2O (2), [Cu(L3)(NCO)]2 (3), [Cu(L4)(NCS)]2 (4), [Cu(L5)(NCS)]2 (5), and [Cu(L4)(Cl)]2 (6), where HL1=2-(hydroxymethyl)-pyridine, HL2=6-methyl-2-pyridine-methanol, HL3=2-(2-hydroxyethyl)-pyridine, HL4=1-dimethylamino-2-methyl-1-propanol, and HL5=1-dimethylamino-2-propanol, respectively), have been prepared and characterized. The single crystal X-ray analysis show that the structures of complexes 1–6 are dimeric with two adjacent copper(II) atoms bridged by pairs of ?-oxy atoms from

Sheng-Chuan Cheng; Ho-Hsiang Wei

2002-01-01

50

Synthesis, characterization, and magnetic properties of new binuclear Cu IICu II bis(oxamato) complexes  

Microsoft Academic Search

Two new neutral, binuclear CuIICuII bis(oxamato) complexes with the formula [Cu2(opba)(pmdta)(MeOH)]·1\\/2MeOH·dmf (3) and [Cu2(nabo)(pmdta)(MeOH)] (4), with opba=o-phenylene-bis(oxamato), nabo=2,3-naphthalene-bis(oxamato), pmdta=N,N,N?,N?,N?-pentamethyldiethylenetriamine and dmf=dimethylformamide have been synthesized and their crystal structures have been determined. The structure of 3 consists of dimeric [Cu2(opba)(pmdta)(MeOH)] entities, joined together by mutual intermolecular Cu?O contacts of the Cu2+ ion of one [Cu(opba)]2? complex fragment and one carboxylate atom

Tobias Rüffer; Björn Bräuer; François Eya’ane Meva; Lorenzo Sorace

2009-01-01

51

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

Microsoft Academic Search

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

Nahed M. H. Salem

2005-01-01

52

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

SciTech Connect

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

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

1989-07-05

53

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

Microsoft Academic Search

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

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

1997-01-01

54

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

SciTech Connect

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

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

2007-10-15

55

Structure, magnetic properties and nuclease activity of pyridine-2-carbaldehyde thiosemicarbazonecopper(II) complexes  

Microsoft Academic Search

New complexes of formulae [Cu(HL2)(H2O)(NO3)](NO3) (1), [{Cu(L1)(tfa)}2] (2), [{Cu(L1)}2(pz)](ClO4)2 (3) and {[{Cu(L1)}2(dca)](ClO4)}n (4), where HL1=pyridine-2-carbaldehyde thiosemicarbazone, HL2=pyridine-2-carbaldehyde 4N-methylthiosemicarbazone, Htfa=trifluoroacetic acid (CF3COOH), pz=pyrazine (C4H4N2) and dca=dicyanamide [N(CN)2]?, have been synthesized and characterized. The crystal structures of these compounds are built up of monomers (1), dinuclear entities with the metal centers bridged through the non-thiosemicarbazone coligand (2 and 3) and 1D chains

Rubén Gil-García; Miguel A. Maestro; José Luis Pizarro; María Isabel Arriortua; Luis Lezama; Teófilo Rojo; Marta González-Álvarez; Joaquín Borrás; Javier García-Tojal

2008-01-01

56

Magnetic and Electrical Properties.  

National Technical Information Service (NTIS)

The development of controlled growth of monolayers and thin metallic films has led to a number of studies in which the magnetic and electrical properties are modified by interfaces. The thrust of his paper is to consider cases where the property modificat...

M. B. Brodsky J. E. Mattson

1989-01-01

57

End-on azido-bridged 3d-4f complexes showing single-molecule-magnet property.  

PubMed

Four tetranuclear 3d-4f complexes with the 4f centers bridged solely by end-on azide bridges were reported. The [CuTb]2 compound displays single-molecule-magnet behavior with hysteresis loops observed at up to 2.4 K. PMID:23746362

Huang, Xing-Cai; Zhou, Chun; Wei, Hai-Yan; Wang, Xin-Yi

2013-06-07

58

Complex magnetic phases in  

Microsoft Academic Search

DC magnetization and AC susceptibility measurements on LuFeO single crystals reveal a ferrimagnetic transition at 240 K followed by additional magnetic transitions at 225 K and 170 K, separating cluster glass phases, and a kinetically arrested state below 55 K. The origin of giant magnetic coercivity is attributed to the collective freezing of ferrimagnetic clusters and enhanced domain wall pinning

M. H. Phan; N. A. Frey; M. Angst; J. de Groot; Brian C Sales; David Mandrus; H. Srikanth

2010-01-01

59

3D supramolecular architectures of copper(II) complexes with 6-methylpicolinic and 6-bromopicolinic acid: Synthesis, spectroscopic, thermal and magnetic properties  

Microsoft Academic Search

Copper(II) complexes of 6-methylpicolinic (6-MepicH) and 6-bromopicolinic acid (6-BrpicH), namely [Cu(6-Mepic)2(H2O)] (1), [Cu(6-Mepic)2(py)] (2) and [Cu(6-Brpic)2(H2O)] (3) were prepared and characterized by spectroscopic methods (IR, EPR). Their molecular and crystal structures were determined by X-ray crystal structure analysis, their thermal stability by TGA\\/DTA methods, while their magnetic properties were elucidated by the measurement of the magnetic susceptibility. X-ray structural analysis

Boris-Marko Kukovec; Zora Popovi?; Bojan Kozlev?ar; Zvonko Jagli?i?

2008-01-01

60

Synthesis, crystal structures, magnetic and luminescent properties of unique 1D p-ferrocenylbenzoate-bridged lanthanide complexes  

SciTech Connect

Treatments of p-ferrocenylbenzoate [p-NaOOCH{sub 4}C{sub 6}Fc, Fc=(eta{sup 5}-C{sub 5}H{sub 5})Fe(eta{sup 5}-C{sub 5}H{sub 4})] with Ln(NO{sub 3}){sub 3}.nH{sub 2}O afford seven p-ferrocenylbenzoate lanthanide complexes {l_brace}[Ln(OOCH{sub 4}C{sub 6}Fc){sub 2}(mu{sub 2}-OOCH{sub 4}C{sub 6}Fc){sub 2}(H{sub 2}O){sub 2}](H{sub 3}O){r_brace}{sub n} [Ln=Ce (1), Pr (2), Sm (3), Eu (4), Gd (5), Tb (6) and Dy (7)]. X-ray crystallographic analysis reveals that the isomorphous complexes {l_brace}[Ce(OOCH{sub 4}C{sub 6}Fc){sub 2}(mu{sub 2}-OOCH{sub 4}C{sub 6}Fc){sub 2}(H{sub 2}O){sub 2}](H{sub 3}O){r_brace}{sub n} (1) and {l_brace}[Pr(OOCH{sub 4}C{sub 6}Fc){sub 2}(mu{sub 2}-OOCH{sub 4}C{sub 6}Fc){sub 2}(H{sub 2}O){sub 2}](H{sub 3}O){r_brace}{sub n} (2) form a unique 1D double-bridged infinite chain structure bridged by mu{sub 2}-OOCH{sub 4}C{sub 6}Fc groups. Each Ln(III) ion adopts a dodecahedron coordination environment with eight coordinated oxygen atoms from two terminal monodentate coordinated FcC{sub 6}H{sub 4}COO{sup -} units, two terminal monodentate coordinated H{sub 2}O molecules and four mu{sub 2}-{sup -}OOCH{sub 4}C{sub 6}Fc units. The luminescent spectra reveal that only 4 and 6 exhibit characteristic emissions of lanthanide ions, Eu(III) and Tb(III) ions, respectively. The variable-temperature magnetic properties of 5 and 7 suggest that a ferromagnetic coupling between spin carriers may exist in 5. - Graphical abstract: Seven p-ferrocenylbenzoate lanthanide coordination polymers were synthesized. Given is the perspective view of a unique 1D double-bridged infinite chain structure of 1, excitation and emission spectra of 6 and plots of chi{sub m}T vs. T and chi{sub m}{sup -1} vs. T of 5.

Yan, P.F.; Zhang, F.M. [Key Laboratory of Functional Inorganic Material Chemistry (Heilongjiang University), Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, No. 74, Xuefu Road, Nangang District, Harbin 150080 (China); Li, G.M., E-mail: gmli@hlju.edu.c [Key Laboratory of Functional Inorganic Material Chemistry (Heilongjiang University), Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, No. 74, Xuefu Road, Nangang District, Harbin 150080 (China); Zhang, J.W.; Sun, W.B. [Key Laboratory of Functional Inorganic Material Chemistry (Heilongjiang University), Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, No. 74, Xuefu Road, Nangang District, Harbin 150080 (China); Suda, M. [Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522 (Japan); Einaga, Y., E-mail: einaga@chem.keio.ac.j [Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522 (Japan)

2009-07-15

61

Structure and magnetic properties of an unprecedented syn-anti ?-nitrito-1?O:2?O' bridged Mn(III)-salen complex and its isoelectronic and isostructural formate analogue.  

PubMed

The preparation, crystal structures and magnetic properties of two new isoelectronic and isomorphous formate- and nitrite-bridged 1D chains of Mn(III)-salen complexes, [Mn(salen)(HCOO)](n) (1) and [Mn(salen)(NO(2))](n) (2), where salen is the dianion of N,N'-bis(salicylidene)-1,2-diaminoethane, are presented. The structures show that the salen ligand coordinates to the four equatorial sites of the metal ion and the formate or nitrite ions coordinate to the axial positions to bridge the Mn(III)-salen units through a syn-anti?-1?O:2?O' coordination mode. Such a bridging mode is unprecedented in Mn(III) for formate and in any transition metal ion for nitrite. Variable-temperature magnetic susceptibility measurements of complexes 1 and 2 indicate the presence of ferromagnetic exchange interactions with J values of 0.0607 cm(-1) (for 1) and 0.0883 cm(-1) (for 2). The ac measurements indicate negligible frequency dependence for 1 whereas compound 2 exhibits a decrease of ?(ac)' and a concomitant increase of ?(ac)'' on elevating frequency around 2 K. This finding is an indication of slow magnetization reversal characteristic of single-chain magnets or spin-glasses. The ?-nitrito-1?O:2?O' bridge seems to be a potentially superior magnetic coupler to the formate bridge for the construction of single-molecule/-chain magnets as its coupling constant is greater and the ?(ac)' and ?(ac)'' show frequency dependence. PMID:21344112

Kar, Paramita; Biswas, Rituparna; Drew, Michael G B; Ida, Yumi; Ishida, Takayuki; Ghosh, Ashutosh

2011-02-23

62

Microstructure and magnetic properties  

Microsoft Academic Search

The relationship between the microstructure and magnetic properties of heat treated Fe-23 wt percent Cr--15 wt percent Co--5 wt percent V has been studied by transmission electron microscopy and Lorentz microscopy. Three different heat treatments were adopted for the present investigations viz., (1) isothermal aging, (2) TMT (thermomagnetic treatment) + step-aging, (3) continuous cooling. It has been found that the

Y. Belli; M. Okada; G. Thomas; M. Homma; H. Kaneko

1977-01-01

63

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

NASA Astrophysics Data System (ADS)

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

Chibotaru, L. F.; Ungur, L.

2012-08-01

64

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

Microsoft Academic Search

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

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

2006-01-01

65

Syntheses, crystal structures and magnetic properties of chromato-, sulfato-, and oxalato-bridged dinuclear copper(II) complexes  

Microsoft Academic Search

Four dinuclear copper(II) complexes of formula [Cu2(bpca)2(H2O)3(CrO4)]·H2O (1), [Cu2(bpca)2(H2O)3(SO4)]·H2O (2), [Cu2(bpca)2(H2O)2(C2O4)]·2H2O (3), and [Cu2(bpca)2(C2O4)] (4) [bpca=bis(2-pyridylcarbonyl)amide anion] have been synthesized and their magnetic behavior has been investigated as a function of temperature. The structures of 1–3 have been determined by single-crystal X-ray diffraction, whereas the structure of 4 was already known. The structures of this family of complexes are made

Mar??a Luisa Calatayud; Isabel Castro; Francesc Lloret

2000-01-01

66

Magnetic properties of heteropolyoxometalates  

Microsoft Academic Search

The progress of the study on the magnetic properties of heteropolyoxometalates during the late decade is reviewed. Some anions\\u000a of heteropolyoxometalates containing magnetic atoms, such as [M4(H2O)4(PW9O34)2\\u000a 10? and [M4(H2O)4(P2W15O56)2\\u000a 16? [M = Co(II), Zn(II), CU(II), Mn(II), Ni(II)], and [GaW9O37M3 (H2O)3]n? [M = Fe(III), CU(II), CO(II)], showed ferromagnetic and antiferrmagnetic properties. The combination of heteropoly anions\\u000a and organic ?-donor of

Lin Xu; Changwen Hu; Enbo Wang

1999-01-01

67

Synthesis, crystal structure and magnetic properties of the Re(ii) complexes NBu4[Re(NO)Br4(L)] (L = pyridine and diazine type ligands).  

PubMed

Four novel Re(ii) complexes of formula NBu4[Re(NO)Br4(L)] [NBu4(+) = tetra-n-butylammonium cation and L = pyridine (), pyrazine (), pyrimidine (), pyridazine ()] have been prepared by a substitution reaction involving NBu4[Re(NO)Br4(EtOH)] and L. Their crystal structures have been determined by single crystal X-ray diffraction. They are all mononuclear complexes whose structure is made up of [Re(NO)Br4L](-) anions and NBu4(+) cations. Each Re(ii) ion is six-coordinate with four bromide ligands, a linear nitrosyl group and one monodentate nitrogen donor L building a tetragonally distorted octahedral surrounding. The Re-Br bond distances cover a narrow range [2.5048(8)-2.5333(5) Å] and they are longer than the Re-NO [1.688(15)-1.736(3) Å] and Re-N bonds [2.219(4)-2.234(3) Å]. The magnetic properties of have been investigated in the temperature range 1.9-295 K. They behave like quasi magnetically isolated spin doublets with very weak antiferromagnetic interactions through intermolecular BrBr contacts. Their magnetic properties are discussed through a deep analysis of the influence of the ligand field, spin-orbit coupling, tetragonal distortion and covalence effects. The values of the temperature-independent paramagnetism for are also substantiated and compared to those previously reported in related systems. PMID:24005773

Pacheco, Mario; Cuevas, Alicia; González-Platas, Javier; Faccio, Ricardo; Lloret, Francesc; Julve, Miguel; Kremer, Carlos

2013-10-15

68

Synthesis of a novel ?-acetate bridged dinuclear Cu(II) complex as model compound for the active site of tyrosinase: crystal structure, magnetic properties and catecholase activity  

Microsoft Academic Search

Reaction of the ligand N,N,N?,N?-bis[(2-hydroxybenzyl)(N-methylimidazolyl)]-2-ol-1,3-propendiamine (Hbhbmipo) with copper(II) perchlorate and sodium acetate in acetonitrile\\/ethanol leads to the assembly of a novel dinuclear copper(II) complex. The crystal structure, magnetic properties and its catecholase activity are reported. Both copper(II) ions are set in a distorted square pyramidal coordination sphere with a N2O3 donor set resulting in a Cu?Cu distance of 3.382(5) Å.

Pavel Gentschev; Matthias Lüken; Niclas Möller; Annette Rompel; Bernt Krebs

2001-01-01

69

Linear and nonlinear two-coordinate vanadium complexes: synthesis, characterization, and magnetic properties of V(II) amides.  

PubMed

The synthesis and characterization of the first stable two-coordinate vanadium complexes are described. The vanadium(II) primary amido derivative V{N(H)Ar(iPr6)}2 [Ar(iPr6) = C6H3-2,6-(C6H2-2,4,6-iPr3)2] (1) was synthesized via the reaction of LiN(H)Ar(iPr6) with the V(III) complex VCl3·2NMe3 or the V(II) salt [V2Cl3(THF)6](+)I(-) in a 2:1 and 4:1 stoichiometry, respectively. Reaction of the less crowded LiN(H)Ar(Me6) with [V2Cl3(THF)6](+)I(-) afforded V{N(H)Ar(Me6)}2 [Ar(Me6) = C6H3-2,6-(C6H2-2,4,6-Me3)2] (2), which has a nonlinear [N-V-N = 123.47(9)°] vanadium coordination. Magnetometry studies showed that V{N(H)Ar(iPr6)}2 and V{N(H)Ar(Me6)}2 have ambient temperature magnetic moments of 3.41 and 2.77 ?B, respectively, which are consistent with a high-spin d(3) electron configuration. These values suggest a significant spin orbital angular momentum contribution that leads to a magnetic moment that is lower than their spin-only value of 3.87 ?B. DFT calculations showed that the major absorptions in their UV-vis spectra were due to ligand to metal charge transfer transitions. Exposure of the reaction mixture for 2 to dry O2 resulted in the formation of the diamagnetic V(V) oxocluster [V{N(H)Ar(Me6)}2]2(?-O-Li-O)2 (3). PMID:23782062

Boynton, Jessica N; Guo, Jing-Dong; Fettinger, James C; Melton, Christopher E; Nagase, Shigeru; Power, Philip P

2013-07-10

70

MAGNETIC NANOPARTICLES: PROPERTIES AND APPLICATIONS  

Microsoft Academic Search

Nanostructured materials often have unique electrical, chemical, structural and magnetic properties. Magnetic nanoparticles may be produced by physical vapour deposition, mechanical attritioning and chemical routes from solution. Through the control of the magnetic field gradient produced by an electromagnet or permanent magnet, these particles can be used to target or manipulate and transport targeted species to a desired location1,2,3. The

L L Vatta

71

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

PubMed

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

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

2013-01-14

72

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

PubMed

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

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

2007-07-13

73

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

74

Gels with magnetic properties  

Microsoft Academic Search

Materials producing strain in magnetic field are known as magnetoelastic or magneto strictive materials. A new type has been\\u000a developed by preparing magnetic field sensitive gels, called ferrogels. Single domain, magnetic particles of colloidal size\\u000a are incorporated into chemically cross-linked polyvinyl-alcohol hydrogels. The finely distributed colloidal particles having\\u000a superparamgnetic behavior couple the shape of the gel to the nonuniform external

L. Barsi; A. Biiki; D. Szabó; M. Zrinyi

75

Magnetic properties of ultimate torsatrons  

NASA Astrophysics Data System (ADS)

The nature and properties of the magnetic surface structure of a torsatron plasma confinement device with helical windings designed so as to eliminate the need for vertical compensation coils are investigated. The winding law necessary to produce a zero vertical field component in a toroidal helix is presented, and the vacuum magnetic properties of the ultimate torsatron are calculated numerically based on the modeling of the winding as many small straight segments of filamentary current. The general size and shape of the magnetic surfaces are found to depend on the number of field periods, the poloidal multiplicity and the aspect ratio, while the coil modulation principally determines the magnetic axis radial position. Means for the variation of magnetic properties through the use of small perturbation coils or the choice of the poloidal multiplicity and the number of field periods are indicated, and the effects of a finite conductor size are pointed out.

Kruckewitt, T. W.; Shohet, J. L.

1980-11-01

76

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

77

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

78

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

PubMed

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

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

2011-08-05

79

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

NASA Astrophysics Data System (ADS)

A non-coplanar dicarboxylate ndca (H2ndca=5-norbornene-2,3-dicarboxylic acid), combining with various dipyridyl-typed tectons, constructs six Cd(II)/Co(II) coordination polymers under hydrothermal conditions, namely [Co(ndca)(H2O)]n (1), {[Co(ndca)(bpe)(H2O)]·H2O}n (2), [Co(ndca)(bpa)0.5(H2O)]n (3), [Cd(ndca)(bpe)(H2O)]n (4), {[Cd(ndca)(bpa)(H2O)]·0.5H2O}n (5), and {[Cd(ndca)(bpp) (H2O)]·H2O}n (6) (bpe=1,2-di(4-pyridyl)ethylene, bpa=1,2-bi(4-pyridyl)ethane, and bpp=1,3-bis(4-pyridyl)propane). All these compounds contain various metal(II)-carboxylate motifs, including carboxylate binuclear (2, 4, 5), carboxylate chain (1, 6) and carboxylate layer (3), which are further extended by dipyridyl-typed coligands to afford a vast diversity of the structures with 2D pyknotic layers (1, 6), 2D open layer (5), 2D?3D interpenetrated networks (2,4), and 3D pillared-layer framework (3), respectively. In addition, fluorescent spectra of Cd(II) complexes and magnetic properties of Co(II) complexes are also given.

Xin, Ling-Yun; Liu, Guang-Zhen; Ma, Lu-Fang; Wang, Li-Ya

2013-10-01

80

Family of dumbbell Ni4Ln2 (Ln = Pr, Sm, Eu, Gd, Tb, Ho, Er) complexes: syntheses, structures, luminescent and magnetic properties.  

PubMed

The synthesis and characterization of a family of heterometallic Ni4Ln2 complexes (Ln = Pr(1), Sm(2), Eu(3), Gd(4), Tb(5), Ho(6) and Er(7)) of the formula [Ni2LnL1L2(OH)(H2O)]2 are reported, where H4L1 is 3,3?-(1E,1?E)-(2,2?-(2-aminoethylazanediyl)bis(ethane-2,1-diyl)bis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)bis(2-hydroxybenzoic acid) and H2L2 is 3-formyl-2-hydroxybenzoic acid. The molecular structures of 1–7 were determined by single-crystal X-ray diffraction and reveal that they are isostructural. In all of these compounds, the six metal ions are held together to form a novel Ni4Ln2O10 core and exhibit a relatively rare dumbbell-type structure. In these compounds, the Ni ions are in slightly distorted square-pyramidal or octahedral environments. An all-oxygen coordination environment (8O) is present around the central lanthanide ion, which is present in a distorted square antiprismatic geometry. The Ln–Ln and Ln–Oavg bond distances in 1–7 show a gradual reduction proceeding from 1 to 7, in accordance with the lanthanide contraction. The luminescent properties of all the compounds have been studied. The magnetic susceptibility analysis demonstrate antiferromagnetic interactions within complex 4. PMID:23396382

Liu, Baolin; Liu, Qingxia; Xiao, Hongping; Zhang, Wu; Tao, Ruojie

2013-04-14

81

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

PubMed

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

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

2012-12-27

82

Synthesis, crystal structure and magnetic properties of an oxalato-bridged Re(IV)Mo(VI) heterobimetallic complex.  

PubMed

The Re(IV)-Mo(VI) compound of formula (PPh(4))(2)[ReCl(4)(?-ox)MoO(2)Cl(2)] (1) constitutes the first example of a heterodinuclear oxalato-bridged complex in the coordination chemistry of molybdenum. PMID:21180753

Martínez-Lillo, José; Armentano, Donatella; De Munno, Giovanni; Lloret, Francesc; Julve, Miguel; Faus, Juan

2010-12-23

83

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

Microsoft Academic Search

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

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

2011-01-01

84

Physical and Chemical Properties of Squarate Complexes. 2. Moessbauer Spectroscopy and Magnetic Susceptibility Studies of Several Dimeric and Trimeric Iron (III) Complexes Containing the Squarate Dianion.  

National Technical Information Service (NTIS)

Products obtained by the reaction of certain bases with micro-dihydroxo-bis(squaratodiaquoiron(III)) dihydrate, (Fe(C4O4)(H2O))(OH))2.2H2O, I, have been isolated and studied by the complementary methods of iron 57 Mossbauer spectroscopy and magnetic susce...

J. T. Wrobleski D. B. Brown

1979-01-01

85

Magnetic properties of binuclear complexes with an oxygen bridge in the light of methods of valence schemes and molecular orbits  

Microsoft Academic Search

Using the results of investigations and x ray diffraction data given in the literature for the metal-oxygen bond, we assume that there is a double bond in the nucleus Me=O=Me. A nucleus of this kind shouldbe considered as one whole in which the properties of the bond belong to the oxygen. A scheme of molecular orbits is pr op0sed which

B. Jezowska-Trzebiatowska; W. Wojciechowski

1963-01-01

86

Syntheses, crystal structures and magnetic properties of mono- and polynuclear [bis(2-arylcarbonyl)amidate]copper(II) complexes  

Microsoft Academic Search

Five copper(II) complexes of formulas [Cu(bpcam)(CN)(H2O)] (1), [Cu(bpcam)(N3)(H2O)]2 (2), [Cu(bpcam)(NCS)(H2O)] (3), [Cu(bpcam)(dca)(H2O)]2 (4) and [Cu(bpca)(tcm)]n (5) [bpcam=bis(2-pyrimidylcarbonyl)amidate, bpca=bis(2-pyridylcarbonyl)amidate, dca=dicyanamide and tcm=tricyanomethanide] have been prepared and their structures determined by single crystal X-ray diffraction. Compounds 1 and 3 are mononuclear species where each copper atom is five coordinated with a tridentate bpcam and a terminally bound cyanide (1)\\/thiocyanate (3) ligands creating

Danielle Cangussu de Castro Gomes; Luminita Marilena Toma; Humberto O. Stumpf; Harry Adams; Jim A. Thomas; Francesc Lloret; Miguel Julve

2008-01-01

87

Genesis of supported carbon-coated Co nanoparticles with controlled magnetic properties, prepared by decomposition of chelate complexes  

Microsoft Academic Search

Following procedures formerly developed for the preparation of supported heterogeneous catalysts, carbon-coated cobalt nanoparticles\\u000a dispersed on porous alumina have been prepared by impregnation of ?-Al2O3 with (NH4)2[Co(EDTA)] and thermal decomposition in inert atmosphere. Below 350 °C, Co(II) ions are complexed in a hexa-coordinated way\\u000a by the EDTA ligand. The thermal treatment at 400–900 °C leads to the EDTA ligand decomposition and recovering

Konstantin Tarasov; Patricia Beaunier; Michel Che; Eric Marceau; Yanling Li

2011-01-01

88

Syntheses, crystal structures and magnetic properties of two dicopper(II) complexes and a zigzag 1-D Cu(II) complex of a bidentate pyridyl-pyrazole ligand  

Microsoft Academic Search

Two new dinuclear copper compounds, [Cu2(pypz)2(N3)2(NO3)2] (1) and [Cu2(pypz)2(OH)2(NO3)2] (2), and one 1-D polymeric Cu(II) complex, [Cu(pypz)(dca)3]n (3) [‘pypz’=(3,5dimethyl-1-(2?-pyridyl)pyrazole) and dca=(dicyanamide)], have been synthesized and characterized crystallographically and spectroscopically. Complex 1 is pseudo-octahedral, adjacent Cu atoms are connected by a pair of ?(1,1) azido groups and the structure is stabilized by ?–? interactions between two pyridyl moieties from two different

Kinsuk Das; Tarak Nath Mandal; Somnath Roy; Atanu Jana; Saugata Konar; Cai-Ming Liu; Anil Kumar Barik; Susanta Kumar Kar

2011-01-01

89

Magnetic properties of oxyhemoglobin.  

PubMed Central

When the magnetic susceptibility of frozen aqueous solutions of human oxyhemoglobin was measured in the range between 25 and 250 K, it showed a temperature-dependent behavior typical of a thermal equilibrium between a ground singlet state and an excited triplet state for two electrons per heme, the energy separation being [2J] = 146 cm-1. By contrast, within the same temperature range, carboxyhemoglobin was found to be diamagnetic, as already reported.

Cerdonio, M; Congiu-Castellano, A; Mogno, F; Pispisa, B; Romani, G L; Vitale, S

1977-01-01

90

Magnetic properties of oxyhemoglobin.  

PubMed

When the magnetic susceptibility of frozen aqueous solutions of human oxyhemoglobin was measured in the range between 25 and 250 K, it showed a temperature-dependent behavior typical of a thermal equilibrium between a ground singlet state and an excited triplet state for two electrons per heme, the energy separation being [2J] = 146 cm-1. By contrast, within the same temperature range, carboxyhemoglobin was found to be diamagnetic, as already reported. PMID:265510

Cerdonio, M; Congiu-Castellano, A; Mogno, F; Pispisa, B; Romani, G L; Vitale, S

1977-02-01

91

Synthesis, structure, and magnetic properties of (6-9)-nuclear Ni(II) trimethylacetates and their heterospin complexes with nitroxides.  

PubMed

New polynuclear nickel trimethylacetates [Ni6(OH)4(C5H9O2)8(C5H10O2)4] (6), [Ni7(OH)7(C5H9O2)7(C5H10O2)6(H2O)] x 0.5 C6H14 x 0.5 H2O (7), [Ni8(OH)4(H2O)2(C5H9O2)12] (8), and [Ni9(OH)6(C5H9O2)12(C5H10O2)4] x C5H10O2 x 3 H2O (9), where C5H9O2 is trimethylacetate and C5H10O2 is trimethylacetic acid, have been found. Their structures were determined by X-ray crystallography. Because of their high solubility in low-polarity organic solvents, compounds 6-9 reacted with stable organic radicals to form the first heterospin compounds based on polynuclear Ni(II) trimethylacetate and nitronyl nitroxides containing pyrazole (L(1)-L(3)), methyl (L(4)), or imidazole (L(5)) substituent groups, respectively, in side chain [Ni7(OH)5(C5H9O2)9(C5H10O2)2(L(1))2(H2O)] x 0.5 C6H14 x H2O (6+1a), [Ni7(OH)5(C5H9O2)9(C5H10O2)2(L2)2(H2O)] x H2O (6+1b), [Ni7(OH)5(C5H9O2)9(C5H10O2)2(L(3))2(H2O)] x H2O (6+1c), [Ni6(OH)3(C5H9O2)9(C5H10O2)4(L(4))] x 1.5 C6H14 (6''), and [Ni4OH)3(C5H9O2)5(C5H10O2)4(L(5))] x 1.5 C7H8 (4). Their structures were also determined by X-ray crystallography. Although Ni(II) trimethylacetates may have varying nuclearity and can change their nuclearity during recrystallization or interactions with nitroxides, this family of compounds is easy to study because of its topological relationship. For any of these complexes, the polynuclear framework may be derived from the [Ni6] polynuclear fragment {Ni6(mu4-OH)2(mu3-OH)2(mu2-C5H9O2-O,O')6(mu2-C5H9O2-O,O)(mu4-C5H9O2-O,O,O',O')(C5H10O2)4}, which is shaped like an open book. On the basis of this fragment, the structure of 7-nuclear compounds (7 and 6+1a-c) is conveniently represented as the result of symmetric addition of other mononuclear fragments to the four Ni(II) ions lying at the vertexes of the [Ni6] open book. The 9-nuclear complex is formed by the addition of trinuclear fragments to two Ni(II) ions lying on one of the lateral edges of the [Ni6] open book. This wing of the 9-nuclear complex preserves its structure in another type of 6-nuclear complex (6'') with the boat configuration. If, however, two edge-sharing Ni(II) ions are removed from [Ni6] (one of these lies at a vertex of the open book and the other, on the book-cover line), we obtain a 4-nuclear fragment recorded in the molecular structure of 4. Twinning of this 4-nuclear fragment forms highly symmetric molecule 8, which is a new chemical version of cubane. PMID:16813397

Ovcharenko, Victor; Fursova, Elena; Romanenko, Galina; Eremenko, Igor; Tretyakov, Evgeny; Ikorskii, Vladimir

2006-07-10

92

Complex magnetic properties of Mn 3Ni 20P 6 and ferromagnetic structure of the new isostructural compound Mn 3Pd 20P 6  

Microsoft Academic Search

A new compound, Mn3Pd20P6, has been synthesized and the crystal and magnetic structures have been determined by neutron powder diffraction. The crystal structure is cubic, with a=11.9563(2)Å, space group Fm3¯m, and is isostructural to Mn3Ni20P6, a ternary ordering variant of the Cr23C6-type structure. The magnetic properties of Mn3Pd20P6 and Mn3Ni20P6 were studied by magnetization measurements. For Mn3Pd20P6 a transition, suggested

T. Eriksson; M. Vennström; S. Ronneteg; Y. Andersson; P. Nordblad

2007-01-01

93

Electron transport properties of magnetic granular films  

NASA Astrophysics Data System (ADS)

In this paper, we present a review of electron transport properties of magnetic granular films. Magnetic granular films are nanocomposite materials which consist of magnetic nanoparticles embedded in a nonmagnetic matrix or assembling of magnetic nanoparticles. According to the style of the nonmagnetic matrix, microstructure and the electron transport mechanism of the films, the magnetic granular films were divided into three groups: (1) magnetic metal-metal granular films, (2) magnetic metal-insulator granular films and (3) magnetic nanocluster-assembled granular films. Moreover, we also systematically review the magnetic properties, transport properties and magnetoresistance effect of size-monodispersed Co and Fe nanocluster-assembled films.

Peng, DongLiang; Wang, JunBao; Wang, LaiSen; Liu, XiaoLong; Wang, ZhenWei; Chen, YuanZhi

2013-01-01

94

Diphenoxo-bridged Ni(II)Ln(III) dinuclear complexes as platforms for heterotrimetallic (Ln(III)Ni(II))2Ru(III) systems with a high-magnetic-moment ground state: synthesis, structure, and magnetic properties.  

PubMed

The first examples of pentanuclear heterotrimetallic [(LnNi)(2)Ru] [Ln(3+) = Gd (1) and Dy (2)] complexes were prepared and magnetostructurally characterized. They exhibit ferromagnetic interactions, leading to a high-magnetic-moment ground state. PMID:22712828

Palacios, María A; Mota, Antonio J; Ruiz, José; Hänninen, Mikko M; Sillanpää, Reijo; Colacio, Enrique

2012-06-19

95

Anion influence on the structure and magnetic properties of a series of multidimensional pyrimidine-2-carboxylato-bridged copper(II) complexes.  

PubMed

Seven new polynuclear copper(II) complexes of formula [Cu(mu-pymca)2] (1) (pymca(-) = pyrimidine-2-carboxylato), [Cu(mu-pymca)Br] (2), [Cu(mu-pymca)Cl] (3), [Cu(mu-pymca)(SCN)(H2O)] x 4 H2O (4), [Cu(mu-pymca)N3] (5), [Cu2(mu1,5-dca)2(pymca)2] (6) (dca = dicyanamide), and K{[mu-Au(CN)2]2[(Cu(NH3)2)2(mu-pymca)]}[Au(CN)2]2 (7) have been synthesized by reactions of K-pymca with copper(II) ions in the presence of different counteranions. Compound 1 is a linear neutral chain with a carboxylato bridging ligand in a syn-anti coordination mode, whereas complexes 2 and 3 consist of cationic linear chains with cis and trans bis(chelating) pymca bridging ligands. Complex 4 adopts a helical pymca-bridged chain structure. In complex 5, zigzag pymca-bridged chains are connected by double end-on azide bridging ligands to afford a unique honeycomb layer structure. Complex 6 is a centrosymmetric dinuclear system with double mu 1,5-dicyanamide bridging ligands and pymca end-cap ligands. Complex 7 is made of pymca-bridged dinuclear [Cu(NH3)2(mu-pymca)Cu(NH3)2](3+) units connected by [Au(CN)2](-) anions to four other dinuclear units, giving rise to cationic (4,4) rectangular nets, which are linked by aurophilic interactions to afford a singular 3D network. Variable-temperature magnetic susceptibility measurements show that complex 1 exhibits a very weak antiferromagnetic coupling through the syn-anti (equatorial-axial) carboxylate bridge (J = -0.57 cm(-1)), whereas complexes 2-4 and 7 exhibit weak to strong antiferromagnetic couplings through the bis(chelating) pymca bridging ligand J = -17.5-276.1 cm(-1)). Quantum Monte Carlo methods have been used to analyze the experimental magnetic data for 5, leading to an antiferromagnetic coupling (J = -34 cm(-1)) through the pymca ligand and to a ferromagnetic coupling (J = 71 cm(-1)) through the azide bridging ligands. Complex 6 exhibits a very weak antiferromagnetic coupling through the dicyanamide bridging ligands (J = -5.1 cm(-1)). The magnitudes of the magnetic couplings in complexes 2-5 have been explained on the basis of the overlapping between magnetic orbitals and DFT theoretical calculations. PMID:18698761

Suárez-Varela, José; Mota, Antonio J; Aouryaghal, Hakima; Cano, Joan; Rodríguez-Diéguez, A; Luneau, Dominique; Colacio, Enrique

2008-08-13

96

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

2009-06-23

97

Properties and biomedical applications of magnetic nanoparticles  

Microsoft Academic Search

Magnetic nanoparticles have a number of unique properties, making them promising agents for applications in medicine including magnetically targeted drug delivery, magnetic hyperthermia, magnetic resonance imaging, and radiation therapy. They are biocompatible and can also be coated with biocompatible surfactants, which may be further functionalized with optically and therapeutically active molecules. These nanoparticles can be manipulated with non-invasive external magnetic

Rajesh Kumar Regmi

2011-01-01

98

Mononuclear thiocyanate containing nickel(II) and binuclear azido bridged nickel(II) complexes of N4-coordinate pyrazole based ligand: Syntheses, structures and magnetic properties  

NASA Astrophysics Data System (ADS)

Two mononuclear nickel(II) complexes [NiL1(NCS)2] (1) and [NiL2(NCS)2] (2) and two azido bridged binuclear nickel(II) complexes [Ni(()2()2] (3) and [Ni(()2()2] (4), where L1, L2, L1? and L2? are N,N-diethyl-N?,N?-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine (L1), N,N-bis((1H-pyrazol-1-yl)methyl)-N?,N?-diethylethane-1,2-diamine (L2), N,N-diethyl-N?-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine (L1?) and N-((1H-pyrazol-1-yl)methyl)-N?,N?-diethylethane-1,2-diamine (L2?) have been synthesized and characterized by microanalyses and physico-chemical methods. Single crystal X-ray diffraction analyses revealed that complexes 1 and 2 are mononuclear NCS- containing Ni(II) complex with octahedral geometry and complexes 3 and 4 are end-on (?-1,1) azido bridged binuclear Ni(II) complexes with distorted octahedral geometry. Variable temperature magnetic studies of the complexes 3 and 4 display ferromagnetic interaction with J values 19 and 32 cm-1, respectively.

Solanki, Ankita; Monfort, Montserrat; Kumar, Sujit Baran

2013-10-01

99

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

100

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

NASA Astrophysics Data System (ADS)

Two binuclear copper(II) complexes one (complex 1) with a macrocyclic ligand (H2L1) and other (complex 2) with a macroacyclic (end-off type) compartmental ligand (HL2) have been synthesized from single pot template synthesis involving copper(II) nitrate, 1,2-diaminoethane, 4-methyl-2,6-diformylphenol, and sodium azide. Structure analysis of complex 1 reveals that there are actually two half molecules present in the asymmetric unit and so two complexes (molecule-I and molecule-II) are present in unit cell, although they show slight differences. The two Cu(II) centers are in distorted square pyramidal coordination environment with two endogenous phenoxo bridges provided by the phenolate of H2L1 having Cu Cu separations of 2.9133(10) Å and 2.9103(10) in the two molecules. In complex 2 the coordination environments around two Cu(II) centers are asymmetric, Cu1 is in distorted square pyramidal environment whereas, the coordination environment around Cu2 is distorted octahedral. The two Cu(II) centers in complex 2 are connected by two different kinds of bridges, one is endogenous phenoxo bridge provided by the phenolate of the ligand HL2 and the other is exogenous azido bridge (?-1,1 type) with Cu Cu distance of 3.032(10) Å. Variable temperature magnetic studies show that two Cu(II) centers in both the complexes are strongly antiferromagnetically coupled with J = -625 ± 5 cm-1 and J = -188.6 ± 1 cm-1 for complex 1 and 2, respectively.

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

2007-05-01

101

Magnetic Properties of the Rare Earth Garnets  

Microsoft Academic Search

The magnetic properties, in static fields, of the rare earth garnets are described. The Ne´el molecular field theory of ferrimagnetism is extended to treat three sublattices of magnetic ions and is shown to account quantitatively for the observed properties. At low temperature, the magnetic moments of those rare earth ions which have nonzero orbital angular momentum, are much less than

R. Pauthenet

1959-01-01

102

Magnetic Properties of Materials and Thin Films  

SciTech Connect

Magnetic and electromagnetic properties of materials and thin films are used extensively. Applications include actuators, storage devices, memory devices, EMI shielding devices, smart sensors, and motors. Magnetism basics must first be understood before the magnetic properties of thin films can be discussed.

Martin, Peter M.

2005-03-15

103

Formation and magnetic properties of Mn-Zn ferrites nanoparticles  

Microsoft Academic Search

The magnetic properties of ferrites are dependent on the crystalline structure and the location of metal ions in the material. The correct crystalline structure of a certain ferrite is formed by a special, very complex, technology. Bulk ferrites are synthesized at high temperatures (> 1300 K) under a special, very complex, thermal treatment. On the other hand, the preparation of

G. Kronkalns

2003-01-01

104

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

105

Hydrothermal synthesis, crystal structure and magnetic properties of a new 2D layered vanadium oxide complex: [Ni(phen)(H2O)]2V4O12  

Microsoft Academic Search

A new organic–inorganic hybrid vanadium oxide complex, [Ni(phen)(H2O)]2V4O12, 1 (phen?=?1,10-phenanthroline), has been synthesized using a hydrothermal method and structurally characterized. Complex 1 exhibits a layered structure in which vanadium oxide chains, {V2O6}, are linked to [Ni(phen)(H2O)] subunits to form a two-dimensional (2D) topology. Crystals are triclinic, space group with a?=?7.869(2), b?=?9.437(2), c?=?20.992(4)?Å, ??=?89.95(3), ??=?89.84(3), ??=?67.22(3)°, V?=?1437.3(5)?Å and Z?=?2. Magnetic measurements

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

2005-01-01

106

Magnetic properties of hexagonal ferrite dot arrays  

Microsoft Academic Search

Patterned magnetic media have been considered as one of the promising candidates for future ultra-high-density magnetic recording. In this paper, a new kind of patterned medium based on hexagonal ferrite have been studied. We have successfully fabricated strontium ferrite dot arrays by electron beam lithography. Their magnetic properties are evaluated by magnetic force microscopy (MFM) and superconducting quantum interference device

Xiaoxi Liu; Akimitsu Morisako

2006-01-01

107

A cyanide-bridged trinuclear Fe(II)-Ru(II)-Fe(II) complex with three stable states: synthesis, crystal structures, electronic couplings and magnetic properties.  

PubMed

Treatment of trans-(Ph-tpy)Ru(PPh(3))(CN)(2) (Ph-tpy = 4'-phenyl-2,2':6',2''-terpyridine, PPh(3) = triphenylphosphine) with 2 equiv of Cp(dppe)Fe(NCCH(3))Br (dppe = bis(diphenylphosphino)ethane) in the presence of NH(4)PF(6) produced a trinuclear cyanide-bridged complex, trans-[Cp(dppe)Fe(CN)(Ph-tpy)Ru(PPh(3))(CN)Fe(dppe)Cp][PF(6)](2) (1[PF(6)](2)). Its one-electron oxidation product (1[PF(6)](3)) and two-electron-oxidation product (1[PF(6)](4)) were obtained by oxidation with (Cp)(2)FePF(6) and AgPF(6), respectively. Firstly, the crystal structures of the cyanide-bridged complexes with three stable states were fully characterized. The reversible electrochemistry measurement of 1(2)(+) shows the presence of a long range intervalence interaction between the external iron centres. Both 1(3)(+) and 1(4)(+) were considered to be Class II mixed valence complexes according to the classification of Robin and Day. Magnetic analysis indicated the presence of a moderately strong antiferromagnetic coupling between the two remote Fe(III) ions across the Fe-NC-Ru-CN-Fe array in 1(4)(+). This proves that the Ru(II)-dicyano complex is a bridging ligand that can transmit electro- and magneto-communication. PMID:22930286

Ma, Xiao; Hu, Sheng-Min; Tan, Chun-Hong; Wen, Yue-Hong; Zhu, Qi-Long; Shen, Chao-Jun; Sheng, Tian-Lu; Wu, Xin-Tao

2012-10-21

108

The Magnetic Properties Experiments on Mars Pathfinder  

NASA Astrophysics Data System (ADS)

A remarkable result from the Viking missions was the discovery that the Martian soil is highly magnetic, in the sense that the soil is attracted by permanent magnets. Both the strong and weak magnets on the Viking landers were saturated with dust throughout the mission. Appropriate limits for the spontaneous magnetization sigma_S were advanced: 1 Am(2) (kg soil)(-1) < sigma_S < 7 Am(2) (kg soil)(-1) . The essential difference between the Magnet Arrays for Mars Pathfinder and the Viking Magnetic Properties Experiment is that Magnet Arrays on Pathfinder will include magnets of lower strengths that the weakest Viking magnet. The five magnets consist of small ring magnets concentric with oppositely polarized cylindrical magnets. The outer diameter of the ring magnets is 18 mm. Discrete (single phase) particles of strongly magnetic minerals (gamma -Fe2O3 or Fe3O4) will stick to all five magnets, while composite (multiphase) particles will stick preferentially to the strongest magnets. Two Magnet Arrays are placed on the Pathfinder lander, with a distance of 1180 and 1450 mm, respectively, from the Imager for Mars Pathfinder (IMP). The magnets will attract airborne dust, and the dust on the magnets will be periodically viewed by the IMP. The images transmitted to Earth are the data on which conclusions on the magnetic properties of the dust will be based. Besides the Magnet Arrays the Pathfinder lander carries two other types of magnets. The Tip Plate Magnet is placed at a distance of 10 cm from the IMP, and thus allows a rather high resolution imaging of the dust clinging to the magnet. The Ramp Magnets are placed near the end of the ramps by which the micro-rover will descend to the surface. The dust on the Ramp Magnets will be studied by the APX-spectrometer of the micro-rover.

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

1996-09-01

109

Backstepping-based lag synchronization of a complex permanent magnet synchronous motor system  

NASA Astrophysics Data System (ADS)

Through introducing the concept of complex current and resetting cross-coupling term, this paper proposes a novel complex permanent magnet synchronous motor system and analyzes its properties. Based on a complex permanent magnet synchronous motor system, we design controllers and achieve lag synchronizations both in real part and imaginary part with backstepping method. In our study, we take complex current, time delay, and structure of complex system into consideration. Numerical simulation results demonstrate the validity of controllers.

Wang, Xing-Yuan; Zhang, Hao

2013-04-01

110

pH-controlled change of the metal coordination in a dicopper(II) complex of the ligand H-BPMP: crystal structures, magnetic properties, and catecholase activity.  

PubMed

The dinucleating ligand 2,6-bis[(bis(2-pyridylmethyl)amino)methyl]-4-methylphenol (H-BPMP) has been used to synthesize the three dinuclear Cu(II) complexes [Cu2(BPMP)(OH)][ClO4](2).0.5C4H8O (1), [Cu2(BPMP)(H2O)2](ClO4)(3).4H2O (2), and [Cu2(H-BPMP)][(ClO4)4].2CH3CN (3). X-ray diffraction studies reveal that 1 is a mu-hydroxo, mu-phenoxo complex, 2 a diaqua, mu-phenoxo complex, and 3 a binuclear complex with Cu-Cu distances of 2.96, 4.32, and 6.92 A, respectively. Magnetization measurements reveal that 1 is moderately antiferromagnetically coupled while 2 and 3 are essentially uncoupled. The electronic spectra in acetonitrile or in water solutions give results in accordance with the solid-state structures. 1 is EPR-silent, in agreement with the antiferromagnetic coupling between the two copper atoms. The X-band spectrum of powdered 2 is consistent with a tetragonally elongated square pyramid geometry around the Cu(II) ions, in accordance with the solid-state structure, while the spectrum in frozen solution suggests a change in the coordination geometry. The EPR spectra of 3 corroborate the solid-state and UV-visible studies. The 1H NMR spectra also lead to observations in accordance with the conclusions from other spectroscopies. The electrochemical behavior of 1 and 2 in acetonitrile or in water solutions shows that the first reduction (Cu(II)Cu(II)-Cu(II)Cu(I) redox couple) is reversible and the second (formation of Cu(I)Cu(I) irreversible. In water, 1 and 2 are reversibly interconverted upon acid/base titration (pK 4.95). In basic medium a new species, 4, is reversibly formed (pK 12.0), identified as the bishydroxo complex. Only 1 exhibits catecholase activity (oxidation of 3,5-di-tert-butylcatechol to the corresponding quinone, vmax = 1.1 x 10(-6) M-1 s-1 and KM = 1.49 mM). The results indicate that the pH dependence of the catalytic abilities of the complexes is related to changes in the coordination sphere of the metal centers. PMID:11196811

Torelli, S; Belle, C; Gautier-Luneau, I; Pierre, J L; Saint-Aman, E; Latour, J M; Le Pape, L; Luneau, D

111

Mononuclear manganese(III) complexes as building blocks for the design of trinuclear manganese clusters: study of the ligand influence on the magnetic properties of the [Mn3(mu3-O)](7+) core.  

PubMed

The synthesis, crystal structure, and magnetic properties of three new manganese(III) clusters are reported, [Mn 3(mu 3-O)(phpzH) 3(MeOH) 3(OAc)] (1), [Mn 3(mu 3-O)(phpzMe) 3(MeOH) 3(OAc)].1.5MeOH (2), and [Mn 3(mu 3-O)(phpzH) 3(MeOH) 4(N 3)].MeOH (3) (H 2phpzH = 3(5)-(2-hydroxyphenyl)-pyrazole and H 2phpzMe = 3(5)-(2-hydroxyphenyl)-5(3)-methylpyrazole). Complexes 1- 3 consist of a triangle of manganese(III) ions with an oxido-center bridge and three ligands, phpzR (2-) (R = H, Me) that form a plane with the metal ions. All the complexes contain the same core with the general formula [Mn 3(mu 3-O)(phpzR) 3] (+). Methanol molecules and additional bridging ligands, that is, acetate (complexes 1 and 2) and azide (complex 3), are at the terminal positions. Temperature dependent magnetic susceptibility studies indicate the presence of predominant antiferromagnetic intramolecular interactions between manganese(III) ions in 1 and 3, while both antiferromagnetic and ferromagnetic intramolecular interactions are operative in 2. PMID:18543906

Viciano-Chumillas, Marta; Tanase, Stefania; Mutikainen, Ilpo; Turpeinen, Urho; de Jongh, L Jos; Reedijk, Jan

2008-06-11

112

Structural characterization and magnetic properties of sandwich-type tungstoarsenate complexes. Study of a mixed-valent VIV2/VV heteropolyanion.  

PubMed

Complexes K11Na1[As2W18(Mn(H2O))3O66]x27H2O (1) and Na12[As2W18(Co(H2O))3O66]x34H2O (2) have been characterized. 1 crystallizes in the orthorhombic space group Pnma, with a = 30.6484(4) A, b = 14.9946(2) A, and c = 19.17080(10) A (Z = 4), while 2 crystallizes in the monoclinic space group C2/c, with a = 14.124(2) A, b = 23.294(3) A, c = 32.247(3) A, and beta = 98.935(10) degrees (Z = 4). Structures of the anions of 1 and 2 are similar, the divalent metals adopting a square pyramidal environment. K11[As2W18(VO)3O66]x23H2O (3) crystallizes in the orthorhombic space group Pnma, with a = 30.6240(5) A, b = 14.9861(2) A, and c = 19.2651(3) A (Z = 4). The structure has revealed a disorder on two of the three metals linking the [alpha-AsW9O33]9- parts. For these two vanadium atoms, the V=O bonds are directed alternatively toward the inside or the outside of the [alpha-AsW9O33]9- cavity. The remaining vanadium shows a V=O bond always directed toward the outside of the cavity. Titration of VIV by CeIV revealed that 3 is the mixed-valent VIV2VV species. Magnetic measurements are in agreement with this formulation. The high-temperature molar magnetic susceptibility of a powdered sample of 3 clearly confirms the presence of two d1 centers. The two VIV are antiferromagnetically coupled, with J = -2.9 cm-1 and g = 1.93. Crystallographic data do not permit the location of the two VIV to be distinguished from the location of the VV. As expected, the Mn(II) are very weakly antiferromagnetically coupled in compound 1. The complex Na8[Ni(H2O)6]2[As2W18(Ni(H2O))3O66]x20H2O (4) has been synthesized. The anion crystallized with two octahedral [Ni(H2O)6]2+ as counterions. Magnetic data have been fitted assuming that the only exchange-coupled centers are the nickels of the polyanion. 4 exhibits an antiferromagnetic coupling with J = -1.7 cm-1, g = 2.27, and theta = -1.5 K. PMID:11195387

Mialane, P; Marrot, J; Rivière, E; Nebout, J; Hervé, G

2001-01-01

113

Discovering the "Hidden" Properties of Magnets  

NSDL National Science Digital Library

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

Thill, Nancy

114

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

115

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

NASA Astrophysics Data System (ADS)

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

Maeda, Yoshitaka; Todaka, Takashi; Enokizono, Masato

116

Magnetic Properties of Ordered Nanoporous Nickel Films  

NASA Astrophysics Data System (ADS)

Nanoporous materials have been of great interest for applications such as biosensors and energy storage. Magnetic properties and the magnetization reversal mechanism of nanoporous magnetic materials remain to be fully understood. In this work, we report the fabrication and magnetic properties of ordered nanoporous nickel (Ni) films. The fabrication involved the following steps: self-assembly of monodispersed polystyrene spheres, electrochemical deposition of desired materials, and sphere removal by a dissolution process. Scanning electron microscopy (SEM) images confirmed the highly ordered three-dimensional hexagonal closed pack structures of the Ni films. We characterized magnetic properties of the three-dimensional nanoporous Ni films using vibrating sample magnetometer (VSM). Magnetic hysteresis loops and first-order reversal curves (FORCs) were measured on the nanoporous Ni films of 200 nm pore size with different thicknesses. Analysis on hysteresis loops and FORC distributions shed light on the reversal mechanism of magnetization and magnetostatic interactions of ordered three-dimensional porous structures.

Liu, Jiabin; Yang, Han-Chang; Cheng, X. M.

2012-02-01

117

Complex magnetic fields in an active region  

NASA Astrophysics Data System (ADS)

High-resolution observations of the full Stokes vector in Fe\\sc i spectral lines around 5250 Angstroms obtained at the Swedish Vacuum Solar Telescope on La Palma with the ZIMPOL I Stokes polarimeter in a complex active region reveal the presence of anomalously shaped Stokes profiles indicating the coexistence of at least two magnetic components within the same spatial resolution element. These Stokes profiles have been analyzed with an inversion code based on a 3-component atmospheric model with two magnetic and one field-free component. The fits to the observations in a magnetic region that resembles a small penumbra reveal the presence of a horizontal magnetic field component with an average field strength of /line{B}=840 G, a mean filling factor of /line?=0.12, and an average temperature /line{T}=5400 K at log {tau_ {5000}}=-1.5 embedded in the main ``penumbral'' magnetic field that has /line{B}=1500 G, /line?=0.56, and /line{T}=4900 K. The horizontal component exhibits a mean outflow of 2.7 km s(-1) which is mainly due to the Evershed flow. In a region where there are strong downflows up to 7 km s(-1) , we infer the possible presence of a shock front whose height changes along the slit. The height variation can be explained by a change of the gas pressure at the base of the photosphere below the shock front as proposed by Thomas & Montesinos (1991). Small plages with field strengths below 900 G have been observed in the vicinity of some pores. Finally, we present a puzzling field structure at the boundary between two adjacent pores. Ambiguous results suggest that although the inversion code is able to successfully invert even very complex Stokes profiles, we are far from a complete description of the field structure in complex magnetic regions. We warn that magnetograms and fits to data involving only a single magnetic component may hide the true complexity of the magnetic structure in at least some parts of active regions.

Bernasconi, P. N.; Keller, C. U.; Solanki, S. K.; Stenflo, J. O.

1998-01-01

118

Emergence of atypical magnetic and electronic properties in graphitic nanowiggles  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

119

Study by Mössbauer spectroscopy of the properties of magnetic carriers for medicines  

NASA Astrophysics Data System (ADS)

The morphology, Mossbauer spectra and magnetic properties of ultrafine particles (10nm) as a core of magnetic carriers (MC) and dextran-ferrite microspheres are studied. The result suggested the presence of two ferrimagnetic at 300K ferric phases, inheriting their valency, crystallographic state and magnetic properties at creating iron-dextran complexes.

Novakova, A. A.; Gendler, T. S.; Brusentsov, N. A.

1992-04-01

120

Synthesis, crystal structure, and magnetic properties of an alkoxo-hydroxo-bridged octanuclear copper(II) complex showing chemically significant hydrogen-bonding interactions involving a metallamacrocyclic core.  

PubMed

A novel 16-member metallamacrocyclic octanuclear copper(II) complex of formulation [Cu8L4(OH)4] (1) has been prepared from a reaction of [Cu2L(O2CMe)] and NaOH in methanol, where L is a pentadentate trianionic Schiff base ligand N,N'-(2-hydroxypropane-1,3-diyl)bis(salicylaldimine). The complex has been characterized by analytical, structural, and spectral methods. It crystallizes in the monoclinic space group C2/c with the following unit cell dimensions: a = 30.365(3) A; b = 14.320(2) A; c = 19.019(2) A; beta = 125.33(2) degrees; V = 6746.7(13) A3; Z = 4. A total of 4589 unique data with l > 2 sigma (l) were used to refine the structure to R1(F0) = 0.0525 and wR2 = 0.1156. The structure consists of four binuclear [Cu2L]+ units linked covalently by four hydroxide ligands to form an octanuclear core which is stabilized by strong hydrogen-bonding interactions involving the hydroxide ligands. Each binuclear unit has a pentadentate ligand L showing N2O3 coordination with an endogenous alkoxide bridging atom. The magnetic susceptibility data of 1, obtained in the temperature range 14-306 K, show the presence of antiferromagnetic exchange interactions between adjacent spin-1/2 Cu(II) ions. The mu eff values are 1.54 and 0.26 microB (per copper) at 295 and 15 K, respectively. The magnetic data have been theoretically fitted using a Heisenberg spin-1/2 Hamiltonian with nearest-neighbor antiferromagnetic interactions. The spin coupling in the metallamacrocyclic ring has been modeled using four different coupling constants (J) on the basis of the structural parameters of the octanuclear core. The coupling constants obtained are J1 = -318.8, J2 = -293.3, J3 = -111.6, and J4 = -63.8 cm-1. The theoretical modeling of the susceptibility data gives a higher magnitude of the antiferromagnetic interaction within the binuclear [Cu2L]+ unit compared to those involving adjacent dimeric units. PMID:12693228

Mukherjee, Arindam; Rudra, Indranil; Nethaji, Munirathinam; Ramasesha, Suryanarayanasastry; Chakravarty, Akhil R

2003-01-27

121

Syntheses, structures, electrochemical measurements and magnetic properties of two iron(III) complexes derived from N,N?-o-phenylenebis(3-ethoxysalicylaldimine)  

NASA Astrophysics Data System (ADS)

The work in this paper presents syntheses, characterizations, crystal structures, electrochemical measurements and magnetic properties of two iron(III) compounds [FeIIIL(H2O)(MeOH)](ClO4) (1) and [FeIIIL(H2O)2](NO3)·H2O (2) derived from the Schiff base compartmental ligand N,N?-o-phenylenebis(3-ethoxysalicylaldimine) (H2L). The two compounds are characterized by elemental analyses, IR, electrospray ionization mass (ESI-MS positive), UV-Vis spectra and conductance values. The structures of 1 and 2 show that these are mononuclear compounds having the metal ion in the N2O2 compartment. Two mononuclear moieties in both the compounds are self-assembled due to bifurcated hydrogen bonds involving coordinated water molecule and O(phenoxo)/O(ethoxy) oxygen atoms. The neighboring dimeric self-assemblies in 2 are further interlinked due to hydrogen bonds involving coordinated and solvated water molecules and nitrate anions to generate a one-dimensional topology. Variable-temperature (2-300 K) magnetic susceptibility measurements reveal that iron(III) centers in 1 and 2 belong to high-spin state and there exist weak antiferromagnetic interactions (J = -0.25 cm-1 for 1 and -0.20 cm-1 for 2) between the metal centers in the dimeric self-assembly. Cyclic voltammetric and square wave voltammetric studies of the two compounds reveal that compounds 1 and 2 undergo reversible Fe(II)/Fe(III) reduction process at E½ = -312 mV and -311 mV, respectively.

Majumder, Samit; Dutta, Supriya; Carrella, Luca M.; Rentschler, Eva; Mohanta, Sasankasekhar

2011-12-01

122

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

123

The Structure and Properties of Highly Conducting Polyacetylene Complexes  

NASA Astrophysics Data System (ADS)

The physicochemical characteristics of polyacetylene and its charge-transfer complexes have been examined. Data on the structural, electrical, magnetic, and optical properties have been discussed from a single viewpoint. Particular attention has been paid to a critical analysis of the soliton concept in relation to the structural and electrophysical properties. The probable mechanisms of the conductivity of polyacetylene have been examined. The bibliography contains 118 references.

Skorobogatov, V. M.; Krivoshei, I. V.

1988-05-01

124

Magnetic properties in textured fine-particles magnets  

NASA Astrophysics Data System (ADS)

The effect of texture on the magnetic properties of single domain particle magnets is discussed. Analytical formulae are derived which enable us to correlate the initial susceptibility, coercive force, anisotropy field and remanence with series expansion coefficients of Legendre Polynomials describing the texture. The analysisof texture influence on the magnetic properties of alnico 5 is presented. This analysis indicates that the initial susceptibility is most strongly affected by the texture changes. The remanence does not change significantly with the texture. The influence of various texture harmonics on magnetic properties is discussed. Also it is demonstrated that the popular use of simple parameters characterizing texture like mean deviation angle or maximum deviation angle may give incorrect results. The problem of calculating the texture from the magnetic data is discussed.

Szpunar, B.; Szpunar, J.

1984-08-01

125

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

126

Investigating the Properties of Magnets  

NSDL National Science Digital Library

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

Eichinger, John

2009-05-15

127

Mononuclear single-molecule magnets: tailoring the magnetic anisotropy of first-row transition-metal complexes.  

PubMed

Magnetic anisotropy is the property that confers to the spin a preferred direction that could be not aligned with an external magnetic field. Molecules that exhibit a high degree of magnetic anisotropy can behave as individual nanomagnets in the absence of a magnetic field, due to their predisposition to maintain their inherent spin direction. Until now, it has proved very hard to predict magnetic anisotropy, and as a consequence, most synthetic work has been based on serendipitous processes in the search for large magnetic anisotropy systems. The present work shows how the property can be predicted based on the coordination numbers and electronic structures of paramagnetic centers. Using these indicators, two Co(II) complexes known from literature have been magnetically characterized and confirm the predicted single-molecule magnet behavior. PMID:23586965

Gomez-Coca, Silvia; Cremades, Eduard; Aliaga-Alcalde, Núria; Ruiz, Eliseo

2013-04-25

128

Heterometallic Cu/Co and Cu/Co/Zn complexes bearing rare asymmetric tetranuclear cores: synthesis, structures, and magnetic and catalytic properties toward the peroxidative oxidation of cycloalkanes.  

PubMed

The three novel heterometallic complexes [CuCo(III)Co(II)(2)(MeDea)(3)Cl(3)(CH(3)OH)(0.55)(H(2)O)(0.45)](H(2)O)(0.45) (1), [CuCo(III)Zn(2)(MeDea)(3)Cl(3)(CH(3)OH)(0.74)(H(2)O)(0.26)](H(2)O)(0.26) (2), and [CuCo(III)Zn(2)(MeDea)(3)Cl(3)(DMF)] (3) have been prepared using a one-pot reaction of copper powder with cobalt chloride (1) and zinc nitrate (2, 3) in a methanol (1, 2) or dimethylformamide (3) solution of N-methyldiethanolamine. A search of the Cambridge Structural Database shows that the tetranuclear asymmetric cores M(4)(?(3)-X)(?-X)(5) of 1-3 represent an extremely rare case of M(4)X(6) arrays. The magnetic investigations of 1 disclose antiferromagnetic coupling in a Co(II)-Cu(II)-Co(II) exchange fragment with J(Co-Cu)/hc = -4.76 cm(-1), J(Co-Co)/hc = -2.76 cm(-1), and D(Co)/hc = +34.3 cm(-1). Compounds 1-3 act as precursors for the mild peroxidative oxidation of cyclohexane to cyclohexanol and cyclohexanone with overall yields up to 23%. The synthetic and structural features as well as the thermogravimetric behavior and electrospray ionization mass spectrometry data are discussed. PMID:21506552

Nesterov, Dmytro S; Kokozay, Volodymyr N; Jezierska, Julia; Pavlyuk, Oleksiy V; Bo?a, Roman; Pombeiro, Armando J L

2011-04-20

129

Soft magnetic properties of nano-structure-controlled magnetic materials  

Microsoft Academic Search

The soft magnetic properties of nano-structure-controlled NANOCON magnetic materials have been studied. The NANOCON materials consist of Fe-based soft magnetic metal particles which are separated from each other by insulation layers of metal oxides on the order of 10 nm thick. The permeability of NANOCON materials was constant up to 10 MHz due to the small isolated particles size compared

Y. Sugaya; O. Inoue; K. Kugimiya

1994-01-01

130

The effect of intrinsic magnetic properties on permanent magnet repulsion  

Microsoft Academic Search

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

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

1972-01-01

131

Magnetic properties of single domain ferromagnetic particles  

NASA Astrophysics Data System (ADS)

Fine ferromagnetic particles occur in very many practical materials of scientific and technological importance. These include spin glasses, rocks, ferrofluids, magnetic recording tapes, permanent magnets, magnetotactic bacteria and other living organisms. It is hence beneficial to consider the magnetic properties of such particles which are small enough to be single domain and to contrast these properties for this wide variety of substances. The discussion is here for the most part concerned with magnetization changes within particles. The following topics are discussed: saturation and remanent magnetization, coercive forces, magnetization mechanisms, remanence curves, interaction field factor, anhysteretic and thermoremanence curves, thermal relaxation processes and superparamagnetism, Vogel-Fulcher law, brief review of typical materials. As an example of magnetization changes by a bulk rotation of the particles a brief account is given of the DORF effect of Pearce.

Wohlfarth, E. P.

1983-11-01

132

Tailoring magnetic properties of Co-ferrite soft magnetic nanoparticles  

Microsoft Academic Search

Monodisperse Co-ferrite soft magnetic nanoparticles with particle size from 3 nm to 20 nm and different Co concentration have been synthesized by chemical solution methods. The composition was controlled by varying the mole ratios of the precursors in the solution. It has been found that magnetic properties of the nanoparticles can be tailored by changing the composition, particle size, as

N. Poudyal

2005-01-01

133

First Principles Studies of the Magnetic Properties of Alnico Permanent Magnet Materials  

NASA Astrophysics Data System (ADS)

Until the advent of rare earth based magnets Alnico was one of the highest energy product hard magnets available. Recently, interest in this system has been rekindled as system whose properties and utility may be further enhanced but does not contain rare earth elements. Recent experiments on Alnico alloy suggest that there is no sharp interface between the disordered bcc FeCo magnetic phase and the ordered B2 NiAl non-magnetic phase; thereby undermining our understanding of the large coercivity of this material. By utilizing several electronic structure methods we first study the issue of the effect of substitutions of additional elements into B2 NiAl phase. We also calculate the magnetic moment distribution across the interface and examine the magnetic ground state. These calculations suggest that the magnetic structure of the B2-phase as well as the interface in much more complex than previously thought.

Ujfalussy, Balazs; Samolyuk, German; Odbadrakh, Khorgolkhuu; Stocks, G. Malcolm

2013-03-01

134

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

SciTech Connect

The object of this program was to demonstrate the feasibility of magnetizing large rare earth/cobalt permanent magnets subsequent to their assembly in complex rotor structures. A safe demagnetization (to near zero remanence) technique was optimized and demonstrated on individual magnets with insignificant detrimental affect on the magnet physical properties. Magnetic finite element analysis was completed which optimized the winding location requirements for the magnetization and substantiated that remagnetization of large rare earth/cobalt permanent magnets assembled in complex rotor structures is feasible if the magnetic field could be obtained.

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

1982-06-01

135

Complex magnetically insulated transmission line oscillator  

NASA Astrophysics Data System (ADS)

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, Yu-Wei; Zhong, Hui-Huang; Shu, Ting; Li, Zhi-Qiang

2008-08-01

136

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

137

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

138

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

139

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

140

Nuclear quantum effects on molecular magnetic properties  

Microsoft Academic Search

We have proposed the computational method to analyze the nuclear quantum effect on the molecular magnetic properties and applied to some small molecules. Our method is based on the multi-component molecular orbital (MC_MO) procedure with the gauge-including atomic orbital (GIAO) and continuous set of gauge transformation (CSGT) methods. The absolute magnetic shielding constants and the magnetic susceptibility are evaluated by

Yukiumi Kita; Masanori Tachikawa

2009-01-01

141

High temperature magnetic properties of oxide superconductors  

Microsoft Academic Search

The magnetic properties of MBa2Cu3O7-x with M = Y and La have been investigated above room temperature up to 1700 K. A pronounced difference in the high temperature magnetic susceptibility behavior between these compounds and samples containing Eu and Gd is reported. Initial results on the in situ magnetic susceptibility variation during the preparation process of YBa2Cu3O7-x are presented.

H. Jenny; G. Leemann; B. Walz; H.-J. Güntherodt

1988-01-01

142

Oxide magnetic semiconductors: Materials, properties, and devices  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

143

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

144

Magnetic Properties of Frustrated Pyrochlore Antiferromagnets  

Microsoft Academic Search

The magnetic properties of polycrystalline samples of pyrochlore antiferromagnets were investigated. The metal atoms in pyrochlores form a 3 dimensional network of comer sharing tetrahedra. Antiferromagnetic ordering is frustrated on such a lattice in the sense that all nearest neighbor microscopic interactions cannot be simultaneously satisfied. A number of experimental (Neutron diffraction, magnetic susceptibility and heat capacity) and theoretical techniques

Jan Naess Reimers

1990-01-01

145

Magnetic properties of frustrated pyrochlore antiferromagnets  

Microsoft Academic Search

The magnetic properties of polycrystalline samples of pyrochlore antiferromagnets were investigated. The metal atoms in pyrochlores form a 3 dimensional network of corner sharing tetrahedra. Antiferromagnetic ordering is frustrated on such a lattice in the sense that all nearest neighbor microscopic interactions cannot be simultaneously satisfied. A number of experimental (Neutron diffraction, magnetic susceptibility and heat capacity) and theoretical techniques

Jan Naess Reimers

1990-01-01

146

Magnetic Properties of Arsenic Cluster Assemblies  

Microsoft Academic Search

Clusters have the potential to serve as building blocks of materials, enabling the tailoring of materials with novel properties. Recently, we synthesized a magnetic cluster assembled material using the As7 cluster and cryptated K, which are the elements from main group. X-ray studies show that the As cluster is distorted to accompany two cryptated K. We have investigated the magnetic

Meichun Qian; A. C. Reber; S. N. Khanna; A. Sen; S. Mandal; N. K. Chaki

2009-01-01

147

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

148

Magnetic properties of some opal-based nanocomposites  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

149

Structural and magnetic properties of three novel complexes with the versatile ligand 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one.  

PubMed

Conventional reactions of the versatile multidentate ligand 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO) with metallic(II) salts lead to three novel multidimensional complexes [Cu(HmtpO)(2)(H(2)O)(3)](ClO(4))(2)·H(2)O (1), {[Cu(HmtpO)(2)(H(2)O)(2)](ClO(4))(2)·2HmtpO}(n) (2) and {[Co(HmtpO)(H(2)O)(3)](ClO(4))(2)·2H(2)O}(n) (3). In each compound, the triazolopyrimidine ligand shows a different and unusual coordination mode, giving rise to structures with diverse topologies and dimensionality. Compound 1 is a monomeric complex, in which HmtpO shows both N3-monodentate and N1,O71-bidentate modes. 2 is a bidimensional framework with the ligand showing a N3,O71 bidentate-bridging mode. The structure of 3 consists of 1D chains, in which HmtpO displays a N1,N3,O71-tridentate-bridging mode. It should be noted that these coordination modes of the HmtpO ligand are unique in the case of compounds 2 and 3. On the other hand, the magnetic properties of the polynuclear complexes 2 and 3 have been studied showing weak ferromagnetic and antiferromagnetic behaviour, respectively. PMID:21479329

Caballero, Ana B; Rodríguez-Diéguez, Antonio; Lezama, Luis; Barea, Elisa; Salas, Juan M

2011-04-11

150

Magnetic properties of iron yoke laminations for SSC dipole magnets  

SciTech Connect

We examine the magnetic properties for the iron used in the SSC yoke laminations so that the accelerator tolerances can be met. The accelerator requirements for field quality specify a tolerance on the variation in the central field. At machine injection the variation in field is attributed to coercivity, H{sub c}. Requirements on the magnitude and the variation of H{sub c} are presented. At the 6.65 tesla operating field the variation in the saturation magnetization dominates the magnetic tolerance for the iron. 4 refs., 3 figs., 2 tabs.

Kahn, S.A.; Morgan, G.H.

1991-01-01

151

Complex Y-type hexagonal ferrites: an ideal material for high-frequency chip magnetic components  

NASA Astrophysics Data System (ADS)

The magnetic properties of complex Y-type hexaferrites series with Ba2Me2Fe12O22 (Me=Zn, Co, Cu) have been investigated. Y-type polycrystalline hexaferrite powders prepared by the solid-state reaction method were characterized by X-ray diffraction and vibrating sample magnetometer. Permeabilities of the samples were investigated using an impedance analyzer. Experimental results show that the substitution of Co for Zn leads to a decrease of saturation magnetization and an increase of magnetic anisotropy. At room temperature, saturation magnetization does not increase linearly as Zn content increases due to the effect of the thermal agitation. The saturation magnetization and magnetic anisotropy of the sample determine the variation of initial permeability. Cu additions can lower the sintering temperature distinctly as the magnetic properties debase slightly. It is shown that these materials should be promising for next generation of high-frequency chip magnetic components (including chip inductors and chip EMI filters).

Bai, Yang; Zhou, Ji; Gui, Zhilun; Yue, Zhenxing; Li, Longtu

2003-08-01

152

Properties of slow magnetic clouds  

NASA Astrophysics Data System (ADS)

Slow (VSW<400kms-1) magnetic clouds have been analyzed to determine their characteristics and geoeffectiveness. It is found that slow clouds have mean magnetic field strengths of ~13nT, peak BS~9nT, and dawn-dusk electric fields of ESW~2.5mVm-1. The clouds are small in spatial size, typically ~0.18AU. The slowest events may have been accelerated to their speeds by interaction with the slow solar wind. Slow clouds are surprisingly geoeffective. Five out of 27 events caused major (DST<=-100nT) magnetic storms. Likewise, these geoeffective clouds may have been decelerated to VSW<400kms-1. The issue of interplanetary acceleration/deceleration will be examined with SOHO coronal mass ejection data in the near future.

Tsurutani, B. T.; Gonzalez, W. D.; Zhou, X.-Y.; Lepping, R. P.; Bothmer, V.

2004-01-01

153

Magnetic properties of the Esquel Pallasite  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

154

Dynamics of a complex quantum magnet.  

SciTech Connect

We have computed the low energy quantum states and low frequency dynamical susceptibility of complex quantum spin systems in the limit of strong interactions, obtaining exact results for system sizes enormously larger than accessible previously. The ground state is a complex superposition of a substantial fraction of all the classical ground states, and yet the dynamical susceptibility exhibits sharp resonances reminiscent of the behavior of single spins. These results show that strongly interacting quantum systems can organize to generate coherent excitations and shed light on recent experiments demonstrating that coherent excitations are present in a disordered spin liquid. The dependence of the energy spectra on system size differs qualitatively from that of the energy spectra of random undirected bipartite graphs with similar statistics, implying that strong interactions are giving rise to these unusual spectral properties.

Landry, James W.; Coppersmith, S. N. (University of Wisconsin, Madison, WI)

2003-01-01

155

Binuclear copper(II) complexes with N4O3 coordinating heptadentate ligand: synthesis, structure, magnetic properties, density-functional theory study, and catecholase activity.  

PubMed

The N4O3 coordinating heptadentate ligand afforded binuclear complex [Cu 2(H 2L)(mu-OH)](ClO4)2 (1) and [Cu2(L)(H2O)2]PF6 (2). In complex 1, two copper ions are held together by mu-phenoxo and mu-hydroxo bridges, whereas in complex 2, the copper centers are connected only by a mu-phenoxo bridge. In 1, both the Cu(II) centers have square pyramidal geometry (tau=0.01-0.205), whereas in the case of 2, one Cu(II) center has square pyramidal (tau=0.2517) and other one has square based pyramidal distorted trigonal bipyramidal (tau=0.54) geometry. Complexes 1 and 2 show an strong intramolecular and very weak antiferromagnetic interaction, respectively. Density-functional theory calculations were performed to establish the magneto structural correlation between the two paramagnetic copper(II) centers. Both of the complexes display a couple of one-electron reductive responses near -0.80 and -1.10 V. The complexes show significant catalytic activity at pH 8.5 on the oxidation of 3,5-di- tert-butylcatechol (3,5-DTBC) to 3,5-di- tert-butylquinone (3,5-DTBQ), and the activity measured in terms of kcat=29-37 h(-1). PMID:18412334

Banerjee, Atanu; Sarkar, Sumana; Chopra, Deepak; Colacio, Enrique; Rajak, Kajal Krishna

2008-04-16

156

Properties of magnetic vortices at elevated temperatures  

NASA Astrophysics Data System (ADS)

Thermal properties of steady-state magnetic vortices in soft materials are numerically evaluated using the recently proposed Landau-Lifshitz-Bloch approach. Circular samples with permalloy-like parameters are simulated. Relevant properties of the vortex core, as its radius, the magnetization drop in its center, and the radius of this magnetization drop are extracted. The dependence of the vortex core radius on temperature agrees well with the theoretical predictions, if only temperature-dependent parameters are taken into account. A new effect is found, which we call magnetization squeezing, resulting from the thermodynamic nature of the Landau-Lifshitz-Bloch approach. Our results show, however, that this squeezing in vortices is a rather weak effect in permalloy.

Lebecki, Kristof M.; Nowak, Ulrich

2013-01-01

157

Magnetic properties of colloidal cobalt nanoclusters  

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

158

Preparation, magnetic and electromagnetic properties of organic magnetic prepolymer containing copper phthalocyanine ring  

NASA Astrophysics Data System (ADS)

A novel kind of organic magnetic prepolymer containing copper phthalocyanine ring was prepared via the polymerization of ferrocenyl organic metal magnetic resin (FOMR) with cuprous chloride. The process of prepolymerization was monitored by Fourier transform infrared spectroscopy and ultraviolet-visible spectrophotometry. Magnetic behavior of the samples was studied by a vibrating sample magnetometer.The experimental results indicated that the organic magnetic prepolymer containing copper phthalocyanine ring showed ferromagnetic property and the magnetism of the samples can be finely tuned by controlling the condition of the reaction. The maximum saturation magnetization of the organic magnetic prepolymer containing copper phthalocyanine ring increased from 3.69 to 8.38 emu/g by increasing the reaction time. Meanwhile, the remnant magnetization increased from 1.06 to 2.36 emu/g. Measurement of electromagnetic parameters of the samples showed that complex permittivity and complex permeability also increased with increase in the reaction time. Among these, the imaginary part of permittivity increased from 0.22 to 0.38 at the frequency of 10.0 GHz.

Wei, Junji; Xu, Mingzhen; Zhang, Jiandong; Zhao, Rui; Liu, Xiaobo

2012-09-01

159

Magneto--optical properties of complex oxides  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

160

Soft magnetic properties of metallic glasses  

Microsoft Academic Search

Recent developments in non-crystalline soft magnetic materials are reviewed in terms of their properties and applications. The glassy alloys intended for use in low-frequency (50\\/60 Hz) applications are shown to outperform any existing crystalline materials including the most advanced electrical steels. Use of Co- and Fe-based metallic glasses in high-frequency devices such as sensors, transducers and magnetic switches is discussed.

Ryusuke Hasegawa

1984-01-01

161

Magnetism of uranium/iron multilayers: II. Magnetic properties  

NASA Astrophysics Data System (ADS)

Well-defined U/Fe multilayers of varying layer thicknesses and bilayer repeat numbers were prepared by a dc magnetron sputtering method. Polarized neutron reflectometry, off-specular neutron diffraction and magnetic moment measurements were used to determine the physical properties of the multilayers leading to an evaluation of the magnetic moments associated with the U and Fe atoms. The multilayers exhibit ferromagnetic behaviour with the easy axis in the plane of the multilayer. The saturation magnetization was found to increase with increasing Fe-layer thickness and the magnetic moment averaged over the structured iron layers was below the bulk value of 2.2 ?B/Fe atom. No anomalies were observed in the magnetization from 4.2 to 375 K in temperature-dependent scans at 0.005 and 0.1 T or in magnetic field scans from 0 to 7 T at 4.2 and 295 K. The hysteresis curves exhibited a small degree of perpendicular magnetic anisotropy. The Curie temperatures for the multilayers were determined from ac susceptibility measurements and were found to be less than the bulk Fe value of 1043 K.

Beesley, A. M.; Zochowski, S. W.; Thomas, M. F.; Herring, A. D. F.; Langridge, S.; Brown, S. D.; Ward, R. C. C.; Wells, M. R.; Springell, R.; Stirling, W. G.; Lander, G. H.

2004-12-01

162

Magnetic properties of Mn doped BN compound  

NASA Astrophysics Data System (ADS)

Electronic and magnetic properties of diluted B1-xMnxN alloys are calculated by means of the full potential linearized augmented plane wave (FP-LAPW) method and the generalized gradient approximation (GGA). A half-metallic state is predicted for a composition of 6.25%. The spin majority being metallic and minority being semiconducting. We found a total magnetic moment of 2 ?B (Bohr-magnetons) per supercell, in agreement with the half-metallic behaviour. The main contribution of the cell magnetic moment is localized at the transition metal site Mn, with a local moment of 1.24 ?B.

Boukra, A.; Zaoui, A.; Ferhat, M.

2012-10-01

163

Rock magnetic properties of uncultured magnetotactic bacteria  

NASA Astrophysics Data System (ADS)

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 fact that only a few cultivable strains are available. Here we report the first series of magnetic measurements on two air-dried samples containing solely MTBs (wild-type cocci and Magnetobacterium bavaricum), which were directly isolated from carbonaceous lake sediments. Systematic rock magnetic studies show that: 1) the magnetosomes in cells are dominated by single-domain (SD) magnetite; 2) the samples have delta ratios ?FC / ?ZFC higher than 2; 3) the measured low-temperature remanence cycling curves as well as the first-order-reversal-curve (FORC) diagrams are significantly different to those measured on synthetic SD-magnetite samples; and 4) the Verwey transition temperature (Tv, ˜100 K) of MTB cells is distinctly lower than that from stoichiometric magnetite (Tv, 120 125 K). Our results provide new insights on the magnetic properties of bacterial magnetite and advance the use of magnetic proxies for decoding the paleomagnetic signals of sediments containing bacterial magnetite.

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

2005-09-01

164

A new modeling of the vector magnetic property  

Microsoft Academic Search

This paper presents a new modeling of the vector magnetic property with an integration term. Recently, the studies of the two-dimensional (2-D) magnetic property have made progress rapidly and the achievements have become a center of attention. The 2-D magnetic measuring technique shows us practical vector constitutive relations in magnetic materials. We enable the magnetic field analysis, which considered the

Hiroyasu Shimoji; Masato Enokizono; Takashi Todaka; Tatsuya Honda

2002-01-01

165

Electronic Properties and Bonding in Transition Metal Complexes: Influence of Pressure  

Microsoft Academic Search

Changes undergone by optical and magnetic properties of Oh, Td and D4h Transition metal (TM) complexes induced by variations of the metal-ligand distance, R, are explored in this work. In parallel, the corresponding variations experienced by the chemical bonding in the complex are analysed in detail. Particular attention is addressed to TM complexes associated with impurities in insulating lattices with

M. Moreno; J. A. Aramburu; M. T. Barriuso

166

Density functional theory study of the structural, electronic, and magnetic properties of a mu-oxo bridged dinuclear Fe(IV) complex based on a tetra-amido macrocyclic ligand.  

PubMed

Recently, the synthesis, crystallographic structure, and Mossbauer characterization of the first example of an [(Fe(IV)TAML)2O](2-) (TAML = tetra-amido microcyclic ligand) complex were reported. Here, we elucidate the prominent structural, electronic, and magnetic properties of this complex on the basis of density functional theory (DFT) calculations. While the torsion between the molecular halves is caused by hydrogen bonding between the TAML moieties, the bending of the Fe-O-Fe unit is an intrinsic property of the bridge. The values for the (57)Fe isomer shift and quadrupole splitting obtained with DFT are in good agreement with experimental results and indicate that the irons have intermediate spin states (S1 = S2 = 1). The iron spins are coupled by strong antiferromagnetic exchange to yield a ground state with system spin S = 0. The Fe-O distances in the excited S > 0 states are significantly longer than in the ground state. Since the wave function of the ground state, in which the iron spins are antiferromagnetically coupled to give system spin S = 0, is a linear combination of Slater determinants that cannot be treated with existing DFT codes, the Fe-O distance for the S = 0 state has been estimated by extrapolation from the optimized geometries for the ferromagnetic state (S = 2) and the broken symmetry state to be 1.748 A, in good agreement with the crystallographic distance 1.728 A. To accommodate the spin-dependent reorganization energies, the conventional bilinear spin Hamiltonian has been extended with a biquadratic coupling term: H(ex) = c' + j0S1 x S2 + j1(S1 x S2)(2). A computational scheme is presented for estimating the exchange parameters, yielding the values j0 = 199 cm(-1) and j1 = -61 cm(-1) for [(Fe(IV)B*)2O](2-). Two mechanisms for biquadratic exchange are discussed. PMID:18817379

Chanda, Arani; de Oliveira, Filipe Tiago; Collins, Terrence J; Münck, Eckard; Bominaar, Emile L

2008-09-26

167

Measurement of dielectric and magnetic properties of soil  

SciTech Connect

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

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

1995-11-01

168

Anion-controlled assembly of four manganese ions: structural, magnetic, and electrochemical properties of tetramanganese complexes stabilized by xanthene-bridged Schiff base ligands.  

PubMed

The reaction of manganese(II) acetate with a xanthene-bridged bis[3-(salicylideneamino)-1-propanol] ligand, H(4)L, afforded the tetramanganese(II,II,III,III) complex [Mn(4)(L)(2)(?-OAc)(2)], which has an incomplete double-cubane structure. The corresponding reaction using manganese(II) chloride in the presence of a base gave the tetramanganese(III,III,III,III) complex [Mn(4)(L)(2)Cl(3)(?(4)-Cl)(OH(2))], in which four Mn ions are bridged by a Cl(-) ion. A pair of L ligands has a propensity to incorporate four Mn ions, the arrangement and oxidation states of which are dependent on the coexistent anions. PMID:22191477

Hirotsu, Masakazu; Shimizu, Yuu; Kuwamura, Naoto; Tanaka, Rika; Kinoshita, Isamu; Takada, Ryoichi; Teki, Yoshio; Hashimoto, Hideki

2011-12-22

169

Magnetic properties and heating effect in bacterial magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

A suspension of bacterial magnetosomes was investigated with respect to structural and magnetic properties and hyperthermic measurements. The mean particle diameter of about 35 nm was confirmed by transmission electron microscopy (TEM), X-ray and magnetic analysis. The X-ray powder diffraction peaks of magnetosomes fit very well with standard Fe3O4 reflections. The found value for specific absorption rate (SAR) of 171 W/g at 5 kA/m and 750 kHz means that magnetosomes may be considered as good materials for the biomedical applications in hyperthermia treatments. Moreover, they have biocompatible phospholipid membrane.

Timko, Milan; Dzarova, Anezka; Kovac, Jozef; Skumiel, Andrzej; Józefczak, Arkadiusz; Hornowski, Tomasz; Goj?ewski, Hubert; Zavisova, Vlasta; Koneracka, Martina; Sprincova, Adriana; Strbak, Oliver; Kopcansky, Peter; Tomasovicova, Natalia

2009-05-01

170

New application of complex magnetic materials to the magnetic refrigerant in an Ericsson magnetic refrigerator  

NASA Astrophysics Data System (ADS)

A complex new magnetic refrigerant, suitable for the ideal Ericsson cycle, has been investigated. Above 15 K, it is necessary to use ferromagnets as a magnetic refrigerant. However, temperature variation for the magnetic entropy change in a homogeneous ferromagnet is not suitable for the Ericsson cycle. The present paper verifies, from theoretical analysis, that a complex ferromagnetic material, for instance, (ErAl2)0.312 (HoAl2)0.198 (Ho/0.5/Dy/0.5/Al2)0.490, has the most suitable characteristics for the ideal Ericsson cycle, including two kinds of isomagnetic field processes. On the basis of the above consideration, a sintered layer structural complex has been prepared, composed of three kinds of RAl(2.15) layers, where R's are rare-earth atoms. From specific heat measurements made on this complex, its entropy and entropy change have been determined. It has been concluded that the complex magnetic material is the most hopeful refrigerant for the Ericsson cycle.

Hashimoto, T.; Kuzuhara, T.; Shashi, M.; Inomata, K.; Tomokiyo, A.

1987-11-01

171

On magnetic properties of the U(Fe,Ti)2 system  

Microsoft Academic Search

The U(Fe1-xTix)2 compounds x < 0.09 show complex magnetic properties depending on concentration of titanium. Magnetic measurements of the U(Fe0.94Ti0.06)2 compound have been carried out in fields up to 3.3 T at temperatures between 4.2 and 270 K. A new concept of the origin of magnetic properties of the whole system is discussed.

M. Zelený; F. Zounová

1993-01-01

172

Factors affecting the magnetic properties of consolidated amorphous powder cores  

Microsoft Academic Search

It has been shown that it is possible to produce high density amorphous metal compacts on a routine basis, that have interesting soft magnetic properties. A study of some of the parameters determining their magnetic properties has been made. As expected, interparticle insulation and compact thickness affect the a.c. properties. Surprisingly, the magnetic properties were found to be relatively independent

D. Raybould; K. S. Tan

1985-01-01

173

Soft magnetic moldable composites: Properties and applications  

NASA Astrophysics Data System (ADS)

A new type of electromagnetic soft magnetic material (SMM) is introduced, based on spherical iron powder particles and a suitable polymer binder. A key feature of this material is that it can be cast or molded into almost any 3D shape, hence the denotation soft magnetic moldable composite (SM2C). The SM2C is compared with a set of reference materials, such as ferrites, laminated steels, and soft magnetic composites, in terms of primary properties such as permeability and loss, and other properties, such as thermal conductivity and manufacturability. The SM2C has the obvious disadvantage of relatively low permeability, but offers benefits such as relatively low losses and high potential for close integration into electromagnetic circuits. Some recent SM2C applications are illustrated, and design and manufacturing aspects are discussed.

Svensson, Leif; Frogner, Kenneth; Jeppsson, Peter; Cedell, Tord; Andersson, Mats

2012-09-01

174

The effective magnetic properties of magnetorheological fluids  

Microsoft Academic Search

Magnetorheological (MR) fluids represent a class of smart materials whose rheological properties change in response to the application of a magnetic field. These fluids typically consist of small (?m) magnetizable particles dispersed in a nonmagnetic carrier fluid that generally contains additives such as surfactants and antiwear agents [1]. Due to such additives, there is an outer nonmagnetic layer on the

K. Ito; H. T. Banks

2001-01-01

175

Slow magnetic relaxation in homoleptic trispyrazolylborate complexes of neodymium(III) and uranium(III).  

PubMed

Lanthanide- and actinide-based single-molecule magnets are rapidly gaining prominence due to the unique properties of f-orbitals, yet no direct comparison of slow magnetic relaxation of an isostructural and valence isoelectronic lanthanide and actinide complex exists. We present the dynamic magnetic properties of two f-element single-molecule magnets, NdTp(3) and UTp(3) (Tp(-) = trispyrazolylborate), demonstrating that, although neither complex displays the full anisotropy barrier predicted from its electronic structure, relaxation is slower in the uranium congener. Magnetic dilution studies performed with NdTp(3) reveal that, while intermolecular interactions partially account for the faster relaxation dynamics, they are not uniquely responsible. PMID:22878433

Rinehart, Jeffrey D; Long, Jeffrey R

2012-08-10

176

Synthesis, structure and magnetic properties of Mn(II) and Cu(II) complexes with the dicyano-acetic acid methyl ester anion  

Microsoft Academic Search

The preparation of the sodium salt of dicyano-acetic acid methyl ester (NaCH3OC(O)C(CN)2) (NaL) is reported. The structure of this anion is related to the structure of the dicyanamide, whose chelating capability has been used to develop 2D networks. Two new complexes of formula [M(L)2(H2O)2] (M=Mn2+ (1) and Cu2+ (2)) have been synthesized and their crystal structures determined by single-crystal X-ray

Carlos Kremer; Cecilia Melián; Julia Torres; Mar??a P Juanicó; Claudia Lamas; Horacio Pezaroglo; Eduardo Manta; Herbert Schumann; Joachim Pickardt; Frank Girgsdies; Oscar N Ventura; Francesc Lloret

2001-01-01

177

Correcting Aberrations in Complex Magnet Systems for Muon Cooling Channels  

Microsoft Academic Search

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

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

2011-01-01

178

Magnetic properties of the iron laminations for CBA magnets  

SciTech Connect

The required magnetic properties of the iron for CBA dipoles are for the most part the same as those for conventional accelerators, namely: low coercive force, high permeability at both low and high inductions, and high saturation induction. There are two main differences in the CBA application, (1) the iron is at 3.8/sup 0/K, and (2) the magnetic field in the iron can go as high as 6 Tesla, which is well above saturation. Measurements of the magnetization curves for CBA iron laminations at 300/sup 0/K and 4.2/sup 0/K are presented. The data are analyzed in terms of a simple model in which the variation in saturation induction can be separated from the low field permeability variation. Tolerances on coercive force, permeability, and saturation induction are discussed.

Tannenbaum, M.J.; Ghosh, A.K.; Robins, K.E.; Sampson, W.B.

1983-01-01

179

Magnetic properties of metal-substituted haematite  

NASA Astrophysics Data System (ADS)

Mineral and isothermal magnetic properties of Al-, Mn- and Ni-substituted haematites were characterized and their relationships evaluated in order to interpret better the results of magnetic analyses of soils and recent sediments. Aluminium, manganese and nickel haematites generally behaved as single-domain (SD) particles. The influence of incorporated Al on the magnetic behaviour of haematite was consistent with Al acting as a paramagnetic dilutent. Mass magnetic susceptibility (chi) and SIRM_800 decreased as the level of Al substitution increased. Incorporation of Mn and Ni increased chi, which could be associated with enhancement of the spin canting effect of haematite. The stability of SIRM_800 to demagnetization for Al-haematite appears to be related to a defect mechanism associated with the development of smaller crystallites arising from Al substitution. Magnetic domain rotation or flipping was probably inhibited, being blocked by structural defects during magnetization and demagnetization, and resulted in a low but stable partial SIRM (SIRM_800). %IRM/SIRM_800 demagnetization curves and estimated (B_o)_CR values of <=100 mT for Mn-haematite indicate pseudo-single-domain/multidomain-like behaviour despite Mn-haematite having particle and crystallite dimensions similar to Ni-haematite, which did not show this behaviour. Data indicate that parameters involving unsaturated, partial SIRM should be used with caution in magnetic studies of soils and sediments.

Wells, M. A.; Fitzpatrick, R. W.; Gilkes, R. J.; Dobson, J.

1999-08-01

180

Magnetic properties of the Imilac Pallasite  

NASA Astrophysics Data System (ADS)

Pallasites are a type of stony-iron meteorite containing olivine crystals within an iron-nickel alloy. Magnetic inclusions, which can be found in the olivine crystals, may contain a memory of exposure to ancient magnetic fields. By studying the properties of the magnetic inclusions, we can learn more about the fields present during formation and how this relates to the evolution of the parent bodies. An important step in this research is to find appropriate samples to measure. The best magnetic recorders are single domain (SD) magnetic grains; to search for potential carriers of SD grains we separated gem-like olivine crystals from a sample of the Imilac pallasite. Crystal fragments were cleaned to remove iron staining; the fragments were further scanned with a visible light microscope to exclude samples with large (potentially multidomain) magnetic inclusions. Measurements of these select samples with an Alternating Gradient Force Magnetometer (AGFM) suggest the presence of single domain magnetic inclusions suitable for the preservation of paleofields. We will present preliminary paleointensity analyses of these samples. This is a presentation of results collected during a REU summer program at the University of Rochester.

Hopkins, J.; Tarduno, J. A.; Cottrell, R. D.

2009-12-01

181

Size-dependent x-ray photoelectron spectroscopy and complex magnetic properties of CoMn2O4 spinel nanocrystals  

NASA Astrophysics Data System (ADS)

A facile nonaqueous route has been developed for the preparation of tetragonal CoMn2O4 nanocrystals. In a simple reaction process, cobalt (II) acetylacetonate and manganese (II) acetylacetonate were dissolved in oleylamine and allowed to decompose at 230 °C. This process led to nearly monodisperse nanocrystals with sizes ranging from 5.3 to 12 nm, as shown by x-ray diffraction analysis and transmission electron microscopy. An x-ray photoelectron spectroscopy study revealed that the lower oxidation state Mn2+ ions increased with decreasing particle size, accompanied by an increase in higher oxidation state cations (such as: Mn4+, Co3+ and Co4+ ions) due to charge balancing. The broad metastable cation distribution reveals that the nanoparticles have potential applications for catalysts. Magnetic measurements revealed that the nanoparticles were ferrimagnetic at low temperature and paramagnetic at room temperature, and possess blocking temperatures of 30-40 K. The blocking temperature did not increase when the samples' size increased from 6.7 to 9.0 nm, partly because of the broad metastable cation distribution and partly due to the dipolar interactions between the nanoparticles. In addition, the nanoparticles showed exchange bias behaviour due to the ferrimagnetic-ferromagnetic exchange coupling between the ferrimagnetic core and ferromagnetic shell.

Zhang, H. T.; Chen, X. H.

2006-03-01

182

Magnetic Properties of Three Impact Structures in Canada  

NASA Astrophysics Data System (ADS)

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

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

1995-09-01

183

All -cis-1,2,3,4,5,6-cyclohexanehexacarboxylate two-dimensional gadolinium(III) complexes: Synthesis, X-ray crystal structure and magnetic properties  

Microsoft Academic Search

The first gadolinium(III) complexes with the trideprotonated form of the 1,2,3,4,5,6-cyclohexanehexacarboxylic acid (H3clhex3?) of formulae [Gd(H3clhex)(H2O)4]n·3nH2O (1) and [Gd(H3clhex)(H2O)4]n·6nH2O (2) have been prepared through the gel technique and their structures determined by single crystal X-ray diffraction. The structure of 1 is made up of 63 honey-comb layers which are generated by [Gd(H2O)4]3+ cations and H3clhex3? anions acting as three-fold nodes

Laura Cañadillas-Delgado; Oscar Fabelo; Jorge Pasán; Miguel Julve; Francesc Lloret; Catalina Ruiz-Pérez

2010-01-01

184

Trinuclear copper(II) complexes of bis(acylhydrazone) ligands. Structural analysis and magnetic properties of a sulfato-bridged hexanuclear dimer  

Microsoft Academic Search

The synthesis and spectroscopic characterization of the new symmetric, O2N2N2?O2?N? ligand bis(salicylaldehyde)methyliminodiacetylhydrazone (H4MeImds) is reported. The reactions of H4 MeImds with copper(II) chloride, nitrate and sulfate give trinuclear metal complexes of formula Cu3(MeImds)Cl2·CHCl3·H2O, Cu3(MeImds)(NO3)2·2H2O and Cu3(MeImds)(SO4)·8H2O; the trinuclear species are obtained in spite of the used metal:ligand molar ratio. The X-ray crystal structure of [Cu3(MeImds)(SO4)(H2O)3]·5H2O is determined; it consists of

Alessia Bacchi; Mauro Carcelli; Giancarlo Pelizzi; Costantino Solinas; Lorenzo Sorace

2006-01-01

185

Structure and magnetic properties of powder soft magnetic materials  

Microsoft Academic Search

Purpose: The paper presents influence of high-energy mechanical milling process, isothermal annealing and to a combination of these two technologies of cobalt base metallic glasses Co77Si11.5B11.5 on magnetic properties and their structure. Design\\/methodology\\/approach: The powder test piece obtained from the input amorphous ribbon in high- energy ball milling. The diffraction examinations and examinations of thin foils were made on the

J. Konieczny; L. A. Dobrza?ski a; A. Przyby?

2007-01-01

186

Optical Properties of Magnetic Semiconductors  

NASA Astrophysics Data System (ADS)

We have employed Infrared Sprectroscopy (IR) and Ellipsometry to explore the band structure of thin films and digitally doped superlattices of Ga1-xMnxAs, prepared in the group of D.D. Awschalom (UCSB). These measurements reveal the important role played by the Mn induced impurity band in the band structure and ferromagnetism of Ga1-xMnxAs. Our IR work on Digital Ferromagnetic Heterostructures reveals a unique ability to tune their optical properties as well as their intrinsic electronic structure without changing the doping/defect level. This work is in collaboration with E.J. Singley, D.N. Basov (University of California, San Diego) J. Stephens, R.K. Kawakami, and D.D. Awschalom(University of California, Santa Barbara).

Burch, Kenneth

2005-03-01

187

Preparation, Magnetic Properties, and Pressure-Induced Transitions of Some MIIMIVF6 (MII=Ni, Pd, Cu; MIV=Pd, Pt, Sn) Complex Fluorides  

NASA Astrophysics Data System (ADS)

MIIMIVF6 (MII=Ni, Pd, Cu; MIV=Pd, Pt) and PdSnF6 complex fluorides have been synthesized via different preparative methods using either BrF3 as oxidizer and solvent, or solid state reactions. For MII=Ni, Pd, the phases crystallize in the rhombohedral space group R3 (LiSbF6 type). Cationic ordering has been studied by X-ray diffraction and 119Sn Mössbauer resonance for PdSnF6. A lowering of symmetry has been observed when the involved divalent cation presents a Jahn-Teller configuration (CuII). Except for PdSnF6, which is paramagnetic down to 4 K, all compounds are Pd2F6-type ferromagnets at low temperature. This behavior has been related to the ordering between half-filled eg orbitals of the divalent cation and empty eg orbitals of the tetravalent cation. A drastic increase in conductivity has been observed under high pressures. In particular the insulator-semiconductor transition induced under pressure (up to 80 kbar) in Pd2F6 corresponds to a decrease of the electrical resistivity by six orders of magnitude. The assumption of an electronic transition induced under pressure from mixed oxidation states (MII+MIV) to an unique trivalent MIII oxidation state has been proposed. .

Tressaud, Alain; Bartlett, Neil

2001-12-01

188

Magnetic properties of nickel hydroxide nanoparticles  

NASA Astrophysics Data System (ADS)

The magnetic properties of 10 nm size Ni(OH)2 nanoparticles prepared by sol-gel method have been studied. The magnetic moments increase with decreasing temperature in a low applied field, which is due to the spin-frozen-like state at low temperatures, and the metamagnetic transition is not clearly observed even in an applied field of 70 kOe due to the size effect. Furthermore, the transition from paramagnetic to antiferromagnetic in the Ni(OH)2 nanoparticles occurs at lower temperature (22 K).

Liu, X. H.; Liu, W.; Lv, X. K.; Yang, F.; Wei, X.; Zhang, Z. D.; Sellmyer, D. J.

2010-04-01

189

Magnetic Properties of Low-Dimensional Cuprates  

Microsoft Academic Search

\\u000a The interest in quasi low-dimensional cuprates originated from the discovery of high-Tc superconductors typically consisting\\u000a of intermediate valence (“doped”) copper oxide planes with strongly correlated d-electrons. For understanding the mechanism\\u000a of superconductivity in these materials their magnetic properties, even in the non-doped state, have to be considered. The\\u000a magnetism of the cuprates mainly originates from the d-electrons of copper in

K.-H. MÜLLER

190

Magnetic properties of transition-metal nitrides  

NASA Astrophysics Data System (ADS)

The structural stability of transition-metal nitrides (TMN's) and their magnetic properties in different phases are investigated using first-principles calculations. The early TMN, ScN-CrN, are found to have rocksalt as equilibrium structure at ambient pressure while the later ones (MnN, FeN, and CoN) prefer zincblende. However, the early ones can also adopt the zincblende structure under tensile strain. The tendency towards magnetism is stronger in the rocksalt phase than in the zincblende phase. Antiferromagnetic versus ferromagnetic ordering in the different phases and the relevance of the results to TM-doped GaN are discussed.

Lambrecht, Walter R. L.; Miao, M. S.; Lukashev, Pavel

2005-05-01

191

Influence of the Ligand Field on Slow Magnetization Relaxation versus Spin Crossover in Mononuclear Cobalt Complexes.  

PubMed

The electronic and magnetic properties of the complexes [Co(terpy)Cl2 ] (1), [Co(terpy)(NCS)2 ] (2), and [Co(terpy)2 ](NCS)2 (3) were investigated. The coordination environment around Co(II) in 1 and 2 leads to a high-spin complex at low temperature and single-molecule magnet properties with multiple relaxation pathways. Changing the ligand field and geometry with an additional terpy ligand leads to spin-crossover behavior in 3 with a gradual transition from high spin to low spin. PMID:24009214

Habib, Fatemah; Luca, Oana R; Vieru, Veacheslav; Shiddiq, Muhandis; Korobkov, Ilia; Gorelsky, Serge I; Takase, Michael K; Chibotaru, Liviu F; Hill, Stephen; Crabtree, Robert H; Murugesu, Muralee

2013-09-05

192

Magnetic and relaxometric properties of Mn ferrites  

NASA Astrophysics Data System (ADS)

We present the magnetic properties and the 1H nuclear magnetic resonance dispersion profiles of Mn-ferrites-based compounds, as possible novel contrast agents (CAs) for magnetic resonance imaging (MRI). The samples consist of nanoparticles (NPs) with the magnetic core made of Mn1+xFe2-xO4, obtained by the rapid decomposition of metalcarbonyl into a hot solvent containing an oxidizer and a coordinating surfactant; by this procedure, monodisperse capped NPs with different sizes have been obtained. We have performed structural and morphological investigation by x-ray powder diffraction and transmission electron microscopy techniques and SQUID magnetometry experiments to investigate the magnetic behaviour of the samples. As required for MRI applications using negative CAs, the samples are superparamagnetic at room temperature, having blocking temperatures in the range 14-80 K. The longitudinal r1 and transverse r2 nuclear relaxivities appear to vary strongly with the magnetic core size, their values being comparable to commercial compounds in the high-frequency range ? > 100 MHz. The experimental results suggest that our samples are suitable for high-frequency MRI imagers in general and in particular for the 3 T clinical imager, as indeed suggested by a recent report (Tromsdorf et al 2007 Nanoletters 7 2422).

Boni, A.; Marinone, M.; Innocenti, C.; Sangregorio, C.; Corti, M.; Lascialfari, A.; Mariani, M.; Orsini, F.; Poletti, G.; Casula, M. F.

2008-07-01

193

Properties of Magnetic Nanoparticles for Magnetic Immunoassays Utilizing a Superconducting Quantum Interference Device  

Microsoft Academic Search

Properties of magnetic nanoparticles are studied for application to magnetic immunoassays utilizing a superconducting quantum interference device (SQUID). In this application, a magnetic marker is made of magnetic nanoparticles, and the binding reaction between an antigen and its antibody is detected by measuring the magnetic field from the marker. Magnetization of an assembly of the particles is simulated when the

Keiji Enpuku; Katsuhiro Inoue; Kazuyuki Soejima

2005-01-01

194

Relationships Between Magnetic Properties and Weathering Indices of Basaltic Rocks  

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

195

Synthesis, properties, and applications of magnetic iron oxide nanoparticles  

Microsoft Academic Search

Magnetic nanoparticles exhibit many interesting properties that can be exploited in a variety of applications such as catalysis and in biomedicine. This review discusses the properties, applications, and syntheses of three magnetic iron oxides – hematite, magnetite, and maghemite – and outlines methods of preparation that allow control over the size, morphology, surface treatment and magnetic properties of their nanoparticles.

Amyn S. Teja; Pei-Yoong Koh

2009-01-01

196

Thickness dependent properties of magnetic ultrathin films  

NASA Astrophysics Data System (ADS)

The dependence of magnetic properties on the thickness of few-layer thin films is investigated at finite temperature using the functional integral method for solving the Heisenberg spin model. The temperature dependence of the ultra-thin film's magnetization and Curie temperature are calculated in terms of the mean field theory and of the Gaussian spin fluctuation approximations. It has been shown that both Curie temperature and temperature interval, where the magnetization is non-zero, are strongly reduced with the thickness reduction by using the spin fluctuation approximations in comparison with the mean field results. Curie temperature dependence on the film thickness calculated numerically well agrees with the experimental data for Ni/Cu(1 0 0) and Ni/Cu(1 1 1) ultrathin films.

Cong, Bach Thanh; Thao, Pham Huong

2013-10-01

197

Magnetic properties of artificially synthesized ferritins  

NASA Astrophysics Data System (ADS)

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

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

2005-05-01

198

Magnetic properties of fine SFMO particles: Superparamagnetism  

NASA Astrophysics Data System (ADS)

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

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

2007-02-01

199

Magnetic Compton scattering: A reliable probe to investigate magnetic properties  

NASA Astrophysics Data System (ADS)

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

Ahuja, B. L.

2013-02-01

200

Effects of magnetic atoms on the properties of ternary superconductors  

SciTech Connect

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

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

1980-01-01

201

Orbital Magnetization as a Local Property  

NASA Astrophysics Data System (ADS)

The modern expressions for polarization P and orbital magnetization M are k-space integrals. But a genuine bulk property should also be expressible in r space, as an unambiguous function of the ground-state density matrix, “nearsighted” in insulators, independently of the boundary conditions—either periodic or open. While P—owing to its “quantum” indeterminacy—is not a bulk property in this sense, M is. We provide its r-space expression for any insulator, even with a nonzero Chern invariant. Simulations on a model Hamiltonian validate our theory.

Bianco, Raffaello; Resta, Raffaele

2013-02-01

202

Magnetic Polymer Nanocomposites with Tunable Microwave Properties  

Microsoft Academic Search

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

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

2010-01-01

203

Magnetic Properties of Iron in Nanocapsules  

Microsoft Academic Search

We have studied the magnetic properties of fine particles of iron and iron carbide nested in carbon cages (nanocapsules), which were synthesized by arc discharge of carbon rods. It is clarified by Mössbauer spectroscopy and thermomagnetic ( M-T ) curve that these particles consist of alpha-Fe, gamma-Fe and Fe3C. Their coercive force is larger than that of bulk alpha-iron, being

Takehiko Hihara; Hideya Onodera; Kenji Sumiyama; Kenji Suzuki; Atsuo Kasuya; Yuichiro Nishina; Yahachi Saito; Tadanobu Yoshikawa; Mitsumasa Okuda

1994-01-01

204

Thermal Transport and Magnetic Properties of Superconductors  

Microsoft Academic Search

We address several aspects of the thermal transport and magnetic properties of conventional and high-T c superconductors. We first derive an expression for the effects of boundaries on phonon transport in small samples of circular and rectangular cross section. A variation of this treatment is then applied to calculate the thermal conductivity and phonon mean-free path of Y Ba_2Cu_3O_{7 -delta}

Raymond Adams Richardson

1993-01-01

205

Magnetic field properties caused by stress concentration  

Microsoft Academic Search

Measurements of the effects of tensile stress on magnetic field properties, infrared thermography and acoustic emission of\\u000a a cuboid sample with an elliptical hole in its center were presented. The tensile stress was applied perpendicularly to the\\u000a sample by electro-tension machine according to a step-loading curve. The changes of the sample temperature was recorded by\\u000a an infrared thermography system and

Song-ling Huang; Lu-ming Li; Ke-ren Shi; Xiao-feng Wang

2004-01-01

206

Complex windmill transformation producing new purely magnetic fluids  

Microsoft Academic Search

Minimal complex windmill transformations of G2IB(ii) spacetimes (admitting a two-dimensional Abelian group of motions of the so-called Wainwright B(ii) class) are defined and the compatibility with a purely magnetic Weyl tensor is investigated. It is shown that the transformed spacetimes cannot be perfect fluids or purely magnetic Einstein spaces. We then determine which purely magnetic perfect fluids (PMpfs) can be

C. Lozanovski; L. Wylleman

2011-01-01

207

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

208

Non-destructive evaluation of mechanical properties of magnetic materials  

SciTech Connect

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

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

2000-07-01

209

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

210

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

211

Earth Nanoparticles with Novel Magnetic Properties  

NASA Astrophysics Data System (ADS)

Our previous studies on Dy nanoparticles showed unique and interesting properties different from bulk^1. In this study we used another technique to prepare Dy and Gd nanoparticles in large quantities needed for further characterization. The rare earth (R=Dy,Gd) nanoparticles were made from sputtered R/W multilayers which were annealed in the temperature range of 500-700°C to form R nanoparticles in the W matrix. The magnetic properties were measured with a SQUID magnetometer. The microstructure and crystal structure were studied with a Jeol JEM-2000FX TEM. The as-made films exhibit amorphous like structure. At the early stages of annealing, the systems showed superparagmagnetic behavior with the blocking temperature increasing with particle size. The magnetic transition in the range of 90-120 K was observed when the particle size increased to about 8 nm. However, the antiferromagnetic to paramagnetic transition which for bulk Dy is at 176K is not observed in these films as consistent with our previous studies. More interestingly, after prolonged annealing, the magnetic transition temperature is decreased instead of increasing as expected for larger particles. EXAFS studies are being planned to further understand the behavior of the Dy nanoparticles. Work supported by NSF under Grant No. DMR 9972035 1. N.B. Shevchenko, et al., Appl. Phys. Lett. 74, 1478

Huang, Yunhe; Okumura, Hideyuki; Christodoulides, Joseph; Hadjipanayis, George; Harris, Vince

2000-03-01

212

Paleoenvironmental conditions in a Travertine Complex deduced from rock magnetism  

NASA Astrophysics Data System (ADS)

We present a rock magnetic study on ca. 100 specimens from a 7.5 m travertine section (BMH) and a parallel 1.0 m profile (BMP) to evaluate vertical and lateral variations. Concentration dependent parameters and inter-parametric ratios point to varying redox conditions through time and space suggesting local paleoenvironmental rather than paleoclimatic control of the rock magnetic properties.

Reinders, Jan; Hambach, Ulrich

213

Database Design for Magnetic Properties Oriented to Electromagnetic Field Analysis  

NASA Astrophysics Data System (ADS)

This paper describes the preliminary investigation of the database of magnetic properties of magnetic materials to realize the highly accurate magnetic field analysis. By showing the various measured properties, the contents of database, which are possible to be prepared by means of current measurement techniques, were shown.

Kitagawa, Wataru; Hattori, Yosuke; Fujiwara, Koji; Ishihara, Yoshiyuki; Todaka, Toshiyuki

214

Synthesis, structure and magnetic properties of a linear-chain manganese(II) complex [Mn(?-Cl) 2(mppma)] n , where mppma is N-(3-methoxypropyl)- N-(pyridin-2-ylmethyl)amine  

Microsoft Academic Search

N-(3-methoxypropyl)-N-(pyridin-2-ylmethyl)amine (abbreviated as mppma) and its complex [Mn(?-Cl)2(mppma)]n have been synthesized. Single-crystal X-ray diffraction analysis has revealed that in the complex, mppma acts as a didentate ligand bound to the Mn(II) ion through two nitrogen atoms; [MnCl2(mppma)] units are connected by double chloride bridges to form one-dimensional zigzag chains of edge-sharing distorted MnCl4(mppma) octahedra. The temperature-dependent magnetic susceptibility data have

Jian-Zhong Wu; Stefania Tanase; Elisabeth Bouwman; Jan Reedijk; Allison M Mills; Anthony L Spek

2003-01-01

215

First-principles studies of magnetic complex oxide heterointerfaces  

NASA Astrophysics Data System (ADS)

Despite the technological advancements driven by conventional semiconductors, continued improvements in nanoelectronics will require new materials with greater functionality. Perovskite-structured transition metal oxides with ABO3 stoichiometry are leading candidates that display amyriad of useful phenomena: ferroelectricity, magnetism, and superconductivity. Since these properties arise from correlated electronic interactions, field-tuning techniques make possible ultra-fast phase transitions between dramatically different states. Unfortunately, the integration of these materials into microelectronics has not yet occurred because of a fundamental lack in understanding how to predict and control these phase transitions at oxide--oxide heterointerfaces. The exceedingly difficult challenge of identifying the microscopic origins of interface electronic behavior is crucial to the functional design and discovery of next generation electronic materials. This dissertation focuses on developing that understanding at magnetic perovskite oxide heterointerfaces using first-principles (parameter free) density functional calculations. New ideas for oxide-oxide superlattice design emerge by considering the interfaces as entirely new complex materials: the interfacial electronic and magnetic structure in artificial geometries is genuinely different from those of the parent bulk materials due to changes in symmetry- and size-dependent properties. By isolating the role of the interacting electron-, orbital-, and spin-lattice degrees of freedom at the interfaces, I identify that the primary interaction governing the ground state derives from latent instabilities present in the bulk phases. The heteroepitaxial structural constraints enhance these modes to re-normalize the low energy electronic structure. To develop insight into the role of thin film thickness and strain effects, I explore how the electronic and magnetic structures of single component films respond to the elastic constraints, in particular, whether ultra-thin layers of SrRuO3 are susceptible to a metal-insulator transition and if strained LaCoO3 films support reversible magnetic spin state transitions. I then examine how the interface between two dissimilar materials---a polarizable dielectric SrTiO3 and a ferromagneticmetal SrRuO 3---responds to an external electric field; I find a spin-dependent screening effect at the heterointerface that manifests as an interfacial magnetoelectric effect and makes possible electric-field control of magnetization. I then explore how the orbital degree of freedom in the electronically degenerate and magnetic SrFeO3 is modified by geometric confinement and changes in chemical bonding at a heterointerface with SrTiO3. I find lattice instabilities are enhanced in the superlattice, and their condensation leads to an electronic phase transition. By isolating the chemical effects at the heterointerface, I identify an additional route to control octahedral rotation patterns pervasive in perovskite oxides films through structural coherency. This study suggests a complementary strain-free avenue for functional thin film design. The materials understanding obtained from these first-principles calculations, when leveraged with new synthesis techniques, offers to have substantial impact on the search and control of new functionalities in oxide heterostructures.

Rondinelli, James M.

216

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

217

FLARES AND THEIR UNDERLYING MAGNETIC COMPLEXITY  

SciTech Connect

SphinX (Solar PHotometer IN X-rays), a full-disk-integrated spectrometer, observed 137 flare-like/transient events with active region (AR) 11024 being the only AR on disk. The Hinode X-Ray Telescope (XRT) and Solar Optical Telescope observe 67 of these events and identified their location from 12:00 UT on July 3 through 24:00 UT 2009 July 7. We find that the predominant mechanisms for flares observed by XRT are (1) flux cancellation and (2) the shearing of underlying magnetic elements. Point- and cusp-like flare morphologies seen by XRT all occur in a magnetic environment where one polarity is impeded by the opposite polarity and vice versa, forcing the flux cancellation process. The shearing is either caused by flux emergence at the center of the AR and separation of polarities along a neutral line or by individual magnetic elements having a rotational motion. Both mechanisms are observed to contribute to single- and multiple-loop flares. We observe that most loop flares occur along a large portion of a polarity inversion line. Point- and cusp-like flares become more infrequent as the AR becomes organized with separation of the positive and negative polarities. SphinX, which allows us to identify when these flares occur, provides us with a statistically significant temperature and emission scaling law for A and B class flares: EM = 6.1 x 10{sup 33} T{sup 1.9{+-}0.1}.

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

2011-01-01

218

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

219

Insertion of a hydroxido bridge into a diphenoxido dinuclear copper(II) complex: drastic change of the magnetic property from strong antiferromagnetic to ferromagnetic and enhancement in the catecholase activity.  

PubMed

A diphenoxido-bridged dinuclear copper(II) complex, [Cu(2)L(2)(ClO(4))(2)] (1), has been synthesized using a tridentate reduced Schiff base ligand, 2-[[2-(diethylamino)ethylamino]methyl]phenol (HL). The addition of triethylamine to the methanolic solution of this complex produced a novel triple bridged (double phenoxido and single hydroxido) dinuclear copper(II) complex, [Cu(2)L(2)(OH)]ClO(4) (2). Both complexes 1 and 2 were characterized by X-ray structural analyses, variable-temperature magnetic susceptibility measurements, and spectroscopic methods. In 1, the two phenoxido bridges are equatorial-equatorial and the species shows strong antiferromagnetic coupling with J = -615.6(6.1) cm(-1). The inclusion of the equatorial-equatorial hydroxido bridge in 2 changes the Cu···Cu distance from 3.018 Å (avg.) to 2.798 Å (avg.), the positions of the phenoxido bridges to axial-equatorial, and the magnetic coupling to ferromagnetic with J = 50.1(1.4) cm(-1). Using 3,5-di-tert-butylcatechol as the substrate, the catecholase activity of the complexes has been studied in a methanol solution; compound 2 shows higher catecholase activity (k(cat) = 233.4 h(-1)) than compound 1 (k(cat) = 93.6 h(-1)). Both complexes generate identical species in solution, and they are interconvertible simply by changing the pH of their solutions. The higher catecholase activity of 2 seems to be due to the presence of the OH group, which increases the pH of its solution. PMID:22963285

Biswas, Apurba; Das, Lakshmi Kanta; Drew, Michael G B; Diaz, Carmen; Ghosh, Ashutosh

2012-09-10

220

Dosimetric properties of magnetically collimated electron beams for radiation therapy  

Microsoft Academic Search

A method of generating magnetically collimated electron beams is developed and the dosimetric properties of magnetically collimated electrons are investigated. An in-air magnetic collimator device was designed and constructed for the study. The magnetic collimator was placed above the exit port of a 14x14 cm² electron cone. Axial magnetic field of approximately 0.6 Tesla is generated inside the collimator via

Lijun Ma

2004-01-01

221

Magnetic properties of Ga-added die-upset Nd-Fe-B magnets  

SciTech Connect

The authors describe the magnetic properties of Ga-added die-upset Nd-Fe-B magnet measured between 4.2 and 473 {Kappa}. The die-upset magnets show larger stepwise decrease in the demagnetization curve than the sintered magnet below the spin reorientation temperature, because of the low alignment of grains in the die-upset magnets. In the temperature range above room temperature, the high coercivity Ga-added die-upset magnet has excellent properties compared with the Ga-free die-upset magnet. The addition of Ga increases the pinning force, resulting in the increase of iHc.

Endoh, M.; Tokunaga, M. (Magnetic and Electronic Materials Research Lab., Hitachi Metals Ltd., Kumagaya, Saitama (JP)); Boltich, E.B.; Wallace, W.E. (Carnegie-Mellon Univ., Pittsburgh, PA (USA). Dept. of Metallurgical Engineering and Materials Science)

1989-09-01

222

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

223

The effect of thermal treatment on the magnetic properties of spinel ferrite nanoparticles in magnetic fluids  

Microsoft Academic Search

Magnetic properties of ferrites are dependent on the crystalline structure and location of metal ions in the material. The most commonly used materials of nanoparticles in magnetic fluids are chemical stable spinel (2-3) ferrites. The preparation of ferrite nanoparticles for magnetic fluids synthesis needs a special technology. More commonly used is the wet chemical coprecipitation production technology of magnetic nanoparticles

G. Kronkalns; A. Dreimane; M. M. Maiorov

2008-01-01

224

Magnetic nanoparticles and concentrated magnetic nanofluids: Synthesis, properties and some applications  

Microsoft Academic Search

This paper reviews some recent results concerning chemical synthesis of magnetic nanoparticles and preparation of various types of magnetic nanofluids. Structural properties and behaviour in external magnetic field of magnetic nanofluids will be emphasized with relation to their use in leakage-free rotating seals and in biomedical applications.

Ladislau Vékás; Doina Bica; Mikhail V. Avdeev

2007-01-01

225

Magnetic properties of anorthosites: A forgotten source for planetary magnetic anomalies?  

Microsoft Academic Search

Anorthosites, igneous rocks very rich in plagioclase, rarely considered to be strongly magnetic, are common on Earth, and the Moon, and inferred to be on other planets. Magnetic properties of anorthosites could be important in investigating associated mineral deposits and in studying magnetic anomalies, especially on Mars. Here we investigate three late Proterozoic anorthosites in Rogaland, Norway, for magnetic and

Laurie L. Brown; Suzanne A. McEnroe

2008-01-01

226

Determination of the Magnetic Moments of Transition Metal Complexes Using Rare Earth Magnets  

Microsoft Academic Search

This paper describes how powerful neodymium magnets and an electronic balance can be used to determine magnetic moments and susceptibilities of transition metal complexes. The technique is an improvement on one previously reported (J. Chem. Educ. 1998, 75, 61) and allows the effect of temperature on paramagnetism to be studied. Results consistent with the Curie law are reported and a

Kevin C. de Berg; Kenneth J. Chapman

2001-01-01

227

Synthesis, crystal structure, spectroscopic and magnetic properties of copper(II) complexes with 2-(2-pyridyl)imino-N-(2-thiazolin-2-yl)thiazolidine (PyTT)  

Microsoft Academic Search

The copper(II) complexes [Cu(PyTT)2(H2O)](NO3)2 (A) and [CuCl2(?-PyTT)2CuCl(H2O)]Cl·3H2O (B) were synthesized and characterized by single crystal X-ray diffraction, IR spectroscopy, UV–Vis–NIR diffuse reflectance and magnetic susceptibility measurements. In the mononuclear compound A the copper ion is in a distorted square pyramidal geometry, with the equatorial plane formed by two thiazoline nitrogen atoms, one imino nitrogen atom and one water molecule, whereas

F. J. Barros-Garc??a; A. Bernalte-Garc??a; F. J. Higes-Rolando; F. Luna-Giles; M. A. Maldonado-Rogado; E. Viñuelas-Zah??nos

2004-01-01

228

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

PubMed

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

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

2002-03-25

229

Rare example of mu-nitrito-1kappa2O,O':2kappaO coordinating mode in copper(II) nitrite complexes with monoanionic tridentate Schiff base ligands: structure, magnetic, and electrochemical properties.  

PubMed

Three new copper(II) complexes, [CuL(1)(NO(2))](n) (1), [CuL(2)(NO(2))] (2), and [CuL(3)(NO(2))] (3), with three similar tridentate Schiff base ligands [HL(1) = 6-amino-3-methyl-1-phenyl-4-azahept-2-en-1-one, HL(2) = 6-amino-3-methyl-1-phenyl-4-azahex-2-en-1-one, and HL(3) = 6-diethylamino-3-methyl-1-phenyl-4-azahex-2-en-1-one] have been synthesized and characterized structurally and magnetically. In all three complexes, the tridentate Schiff base ligand and one oxygen atom of the nitrite ion constitute the equatorial plane around Cu(II), whereas the second oxygen atom of the nitrite ligand coordinates to one of the axial positions. In 1, this axially coordinated oxygen atom of the nitrite ligand also coordinates weakly to the other axial position of a Cu(II) ion of another unit to form a one-dimensional chain with the mu-nitrito-1kappa(2)O,O':2kappaO bridging mode. Complexes 2 and 3 are discrete monomers that are joined together by intermolecular H bonds and C-H....pi interactions in 2 and by only C-H....pi interactions in 3. A weak antiferromagnetism (J = -1.96(2) cm(-1)) is observed in complex 1 due to its asymmetric nitrite bridging. Complexes 2 and 3 show very weak antiferromagnetic interactions (J = -0.089 and -0.096 cm(-1), respectively) attributed to the presence of intermolecular H-bonding and C-H....pi interactions. The corresponding Cu(I) species produced by the electrochemical reduction of complexes 1 and 2 disproportionate to Cu(0) and Cu(2+,) whereas the reduced Cu(I) species of complex 3 seems to be stable presumably due to a higher tetrahedral distortion of the equatorial plane in 3 compared to that in 1 and 2. PMID:18998624

Sarkar, Biswarup; Konar, Sanjit; Gómez-García, Carlos J; Ghosh, Ashutosh

2008-12-15

230

Optical and magnetic properties of boron fullerenes.  

PubMed

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

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

2009-04-09

231

Magnetic properties of graphene quantum dots  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

232

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

Microsoft Academic Search

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

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

2000-01-01

233

Matching Martian Magnetic Anomalies and Snc Magnetic Properties  

Microsoft Academic Search

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

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

2002-01-01

234

The flow properties of complex fluids  

NASA Astrophysics Data System (ADS)

"Complex fluids" are a class of systems exhibiting "unusual" mechanical responses to applied stress or strain that are not well understood. Theoretically, these systems have been considered in several different contexts such as glasses and plastics as well as other thermal and "athermal" systems. Significant agreement has been found in considering these from a variety of theoretical perspectives. However inconsistent and controversial conclusions concerning their material properties still persists. The careful study of these systems has the exciting potential to lead to "new physics" and new states of matter. For example, it has been suggested that these systems can jam and a "jamming phase diagram" can be used to consider how these systems can jam and unjam. Is such a theoretical framework useful? Is there really a new state of matter that is jammed? This large body of theoretical work has thus far been poorly supported with experiments. In this thesis, we will examine the rheological properties of two experimental systems: a bubble raft and a sphere raft. These systems were studied because they represent "generic" complex fluids that can be explored over a wide range of parameters. In this way, these systems can be considered a good sample study to understand this broad class of systems. This thesis considers first the characterization of these materials. We then go on to address questions related to jamming including the jamming transition and description of fluctuations through various theoretical frameworks. This experimental work was considered with two main experimental setups: a Couette viscometer capable of measuring stress with a torsion pendulum and a parallel plate shearing apparatus. In the bubble raft we consider different ways energy is injected into the system. By measuring how energy is dissipated in the system in the form of "stress drops", we are able to probe different time scales and length scales. In the bead raft, we consider experimental methods to measure an "effective temperature". A measurement of such a quantity in a nonequilibrium system can be a very important step in applying the "machinery" of current physical theories to these poorly understood systems. These two geometries and the investigation of two similar yet distinct complex fluids provides a preliminary experimental overview in considering the characteristics and dynamics of this interesting system class.

Twardos, Michael John

2005-12-01

235

The effects of magnetic nanoparticle properties on magnetic fluid hyperthermia  

Microsoft Academic Search

Magnetic fluid hyperthermia (MFH) is a noninvasive treatment that destroys cancer cells by heating a ferrofluid-impregnated malignant tissue with an ac magnetic field while causing minimal damage to the surrounding healthy tissue. The strength of the magnetic field must be sufficient to induce hyperthermia but it is also limited by the human ability to safely withstand it. The ferrofluid material

Ravi Kappiyoor; Monrudee Liangruksa; Ranjan Ganguly; Ishwar K. Puri

2010-01-01

236

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

237

Magnetic properties of hydrides of uranium ternary intermetallics  

NASA Astrophysics Data System (ADS)

We demonstrate the effect of hydrogenation on magnetic properties of several groups of uranium ternary intermetallics. The H absorption leads quite generally to stronger magnetic interactions and/or larger U magnetic moments. The effect is partly attributed to the volumes expansion reducing the 5f-5f overlap, partly to weakening of the 5f-ligand hybridization.

Havela, L.; Miliyanchuk, K.; Kolomiets, A. V.; Andreev, A. V.; Pereira, L. C. J.; Gonçalves, A. P.

2006-05-01

238

Magnetic properties of polymer nanocomposites containing iron oxide nanoparticles  

Microsoft Academic Search

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

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

2003-01-01

239

Magnetic properties of glasses with high iron oxide content  

Microsoft Academic Search

A study of the magnetic properties of glasses with high iron oxide content has been carried out. This glass series was obtained by recycling goethite (FeOOH) industrial waste, with dolomite and glass cullet as complementary raw materials. The magnetisation as a function of applied magnetic field for these glasses was measured. According to the magnetic behaviour, which closely correlates with

Maximina Romero-Perez; Jesús Ma. Rincón; Carlos J. R. González Oliver; Claudio D’Ovidio; Daniel Esparza

2001-01-01

240

Magnetic properties of polymer nanocomposites containing iron oxide nanoparticles  

Microsoft Academic Search

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

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

2003-01-01

241

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

242

Static and dynamic properties of vortices in anisotropic magnetic disks  

Microsoft Academic Search

We investigate the effect of the magnetic anisotropy (Kz) on the static and dynamic properties of magnetic vortices in small disks. Our micromagnetic calculations reveal that for a range of Kz there is an enlargement of the vortex core. We analyze the influence of Kz on the dynamics of the vortex core magnetization reversal under the excitation of a pulsed

Tiago S. Machado; Tatiana G. Rappoport; Luiz C. Sampaio

2008-01-01

243

Magnetic screening properties of superconductor-ferromagnet bilayers  

NASA Astrophysics Data System (ADS)

We study theoretically the magnetic screening properties of thin, diffusive superconductor/ferromagnet bilayers subject to a perpendicular magnetic field. We find that the effective penetration depth characterizing the magnetic response oscillates with the thickness of the ferromagnetic layer on the scale of the ferromagnetic coherence length.

Houzet, Manuel; Meyer, Julia S.

2009-07-01

244

Magnetic Properties of Lattice Imperfections in Alkali Halide Single Crystals  

Microsoft Academic Search

Using a torque magnetometer, experimental results are reported on some new magnetic properties in high-purity, optical-quality single crystals of lithium fluoride, potassium chloride, and sodium chloride. Since the torque observations are not produced by the gross diamagnetism of these salts, the magnetic centers may be along dislocations because the magnetic susceptibility is observed to possess uniaxial anisotropy. Soft x irradiation

T. W. Adair; E. J. Sharp; C. F. Squire

1966-01-01

245

Magnetic properties of oolitic iron ore on Bell Island, Newfoundland  

Microsoft Academic Search

Magnetic properties of samples from Bell Island sedimentary rocks have been studied. X-ray analysis indicates that the main magnetic mineral is hematite in all samples. The other iron-bearing minerals identified are siderite and chamosite. Microscope observations of thin sections suggest that the rocks consist of oolitic hematite in a matrix of siderite or calcite. The intensity of natural remanent magnetization

Ö. Özdemir; E. R. Deutsch

1984-01-01

246

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

247

Size dependent magnetic properties of iron oxide nanoparticles  

Microsoft Academic Search

?Fe2O3 nanoparticles has been synthesized by a combination of chemical and ultrasonication procedure and further stabilized with surfactant. Their magnetic properties are compared with the different fractions (10–12, 20–30, 100–150nm) of commercially available iron oxide. The sizes obtained from the scanning transmission electron micrographs are correlated with the magnetic properties of the particles.

Jhunu Chatterjee; Yousef Haik; Ching-Jen Chen

2003-01-01

248

Intergranular Phase in Nanocrystalline Alloys: Structural Aspects and Magnetic Properties  

Microsoft Academic Search

The nanocrystalline alloys consist of nanocrystalline grains embedded in a residual amorphous phase. Such a structure provides excellent soft magnetic properties, as evidenced in FINEMET, NANOPERM, and HITPERM systems. Apart from recognizing the important role of nanocrystalline grains governing these soft magnetic properties, we focused our attention on the amorphous remainder which shows heterogeneous chemical composition and structure, thus influencing

J.-M. Greneche

249

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

2011-10-31

250

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

251

Magnetic twist: a source and property of space weather  

NASA Astrophysics Data System (ADS)

Aim: We present evidence for finite magnetic helicity density in the heliosphere and numerical models thereof, and relate it to the magnetic field properties of the dynamo in the solar convection zone. Methods: We use simulations and solar wind data to compute magnetic helicity either directly from the simulations or indirectly using time series of the skew-symmetric components of the magnetic correlation tensor. Results: We find that the solar dynamo produces negative magnetic helicity at small scales and positive at large scales. However, in the heliosphere these properties are reversed and the magnetic helicity is now positive at small scales and negative at large scales. We explain this by the fact that a negative diffusive magnetic helicity flux corresponds to a positive gradient of magnetic helicity, which leads to a change of sign from negative to positive values at some radius in the northern hemisphere.

Warnecke, Jörn; Brandenburg, Axel; Mitra, Dhrubaditya AB(; )

2012-08-01

252

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

PubMed

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

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

2013-03-18

253

Soft Magnetic Properties of FeN\\/FeBN Multilayers  

Microsoft Academic Search

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

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

1992-01-01

254

Soft Magnetic Properties of Fe5 wt%Al Alloy  

Microsoft Academic Search

In this investigation, a new soft magnetic material (iron with 5 wt% aluminum) has been developed using powder metallurgy processing. The microstructure and the magnetic properties of this new P\\/M alloy have been characterized at both room and elevated temperatures (up to 500°C). The influence of post-sintering (after initial processing) on the porosity and magnetic properties of this material has also

Elizabeth C. Buc; Susil K. Putatunda; Ratna Naik

2008-01-01

255

Magnetic properties of sedimentary greigite (Fe3S4): An update  

NASA Astrophysics Data System (ADS)

Greigite (Fe3S4) is an authigenic ferrimagnetic mineral that grows as a precursor to pyrite during early diagenetic sedimentary sulfate reduction. It can also grow at any time when dissolved iron and sulfide are available during diagenesis. Greigite is important in paleomagnetic, environmental, biological, biogeochemical, tectonic, and industrial processes. Much recent progress has been made in understanding its magnetic properties. Greigite is an inverse spinel and a collinear ferrimagnet with antiferromagnetic coupling between iron in octahedral and tetrahedral sites. The crystallographic c axis is the easy axis of magnetization, with magnetic properties dominated by magnetocrystalline anisotropy. Robust empirical estimates of the saturation magnetization, anisotropy constant, and exchange constant for greigite have been obtained recently for the first time, and the first robust estimate of the low-field magnetic susceptibility is reported here. The Curie temperature of greigite remains unknown but must exceed 350°C. Greigite lacks a low-temperature magnetic transition. On the basis of preliminary micromagnetic modeling, the size range for stable single domain behavior is 17-200 nm for cubic crystals and 17-500 nm for octahedral crystals. Gradual variation in magnetic properties is observed through the pseudo-single-domain size range. We systematically document the known magnetic properties of greigite (at high, ambient, and low temperatures and with alternating and direct fields) and illustrate how grain size variations affect magnetic properties. Recognition of this range of magnetic properties will aid identification and constrain interpretation of magnetic signals carried by greigite, which is increasingly proving to be environmentally important and responsible for complex paleomagnetic records, including widespread remagnetizations.

Roberts, Andrew P.; Chang, Liao; Rowan, Christopher J.; Horng, Chorng-Shern; Florindo, Fabio

2011-01-01

256

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

NASA Astrophysics Data System (ADS)

The effects of surface modification on the magnetic properties of polymer-bonded Nd-Fe-B magnets have been studied. Two sets of Nd-Fe-B powders, coated and uncoated, were blended and compression molded with polyphenylene sulfide in isotropic form. Their magnetic properties were measured using a Helmholtz coil and a SQUID. The results showed that the effect of the coating significantly improved the irreversible loss in flux and energy product of the polymer-bonded magnets. The results have been interpreted using an isotropic model of hysteresis that takes into account energy losses. The modeling showed that the presence of soft magnetic materials in the Nd-Fe-B powders caused by oxidation reduces the interaction among magnetic particles, however, the coating treatment alters the magnetic properties by increasing the remanence of polymer-bonded magnets via increasing the interparticle coupling coefficient.

Xiao, J.; Otaigbe, J. U.; Jiles, D. C.

2000-07-01

257

Fabrication and magnetorheological property of nano-sized magnetic particles  

Microsoft Academic Search

Magnetorheological (MR) fluid, a suspension of synthesized nano-sized magnetic particle in non magnetic carrier fluid, was prepared and then their various characteristics were examined in this study. Magnetic particle was at first synthesized in a rather simple process of decomposition of penta carbonyl iron (Fe(CO)5) using oleyl amine and kerosene. Magnetic property and morphology of the synthesized nanoparticle were confirmed

Kang Hyun Song; Bong Jun Park; Hyoung Jin Choi

2010-01-01

258

Magnetic properties of neodymium--samarium--cobalt alloys. Technical report  

Microsoft Academic Search

The magnetic properties of the pseudo-binary alloy system Nd(1-x)Sm(x)Co5, in particular the variation of the magnetization and magnetocrystalline anisotropy with temperature and composition, were determined. The special interest in these variables stems from their quantative relationships to magnetic domain wall characteristics and the relationship of domain walls to RCo5 coercivity, the key parameter in the development of permanent magnets. The

W. G. D. Frederick; H. J. Garrett; M. Hoch

1975-01-01

259

Electronic response properties of carbon nanotubes in magnetic fields.  

PubMed

Magnetic linear response properties for achiral and chiral carbon nanotubes were investigated with first-principles electronic structure methods. We have computed the magnetic shielding inside and outside the tubes originating from electronic current densities induced by the application of an external magnetic field. This electronic response of the nanotubes was analyzed for external magnetic fields both parallel and perpendicular to the tube axis. The magnetic screening would be experienced by guest molecules inside the tubes, measurable by NMR spectroscopy on isotopically labeled samples. Special attention is given to chiral nanotubes, in which longitudinal fields induce a non-zero longitudinal current density and thus tangential magnetic fields outside the tubes. PMID:19206596

Sebastiani, Daniel; Kudin, Konstantin N

2008-04-01

260

Superconductivity and magnetism of complex rhodium borides  

NASA Astrophysics Data System (ADS)

A number of complex rhodium borides with an LuRu4B4-type structure is synthesized; these are DyRh4B4 (samples HP) with T c ? 4.5 K, DyRh3.8Ru0.2B4 (samples AM) with T c ? 4.5 K, Dy0.8Er0.2Rh3.8Ru0.2B4 (samples AM) with T c ? 6.3 K, and HoRh3.8Ru0.2B4 (samples AM) with T c ? 6.0 K. The temperature dependence of upper critical field B c2( T) for all the samples under study exhibits an anomalous behavior. In all cases, the curve B c2( T) demonstrates a point of inflection, after which the curve deviates from the classical parabolic law abruptly upward for DyRh4B4 and DyRh3.8Ru0.2B4 (the 1st group of compounds) and downward for the Dy0.8Er0.2Rh3.8Ru0.2B4 and HoRh3.8Ru0.2B4 compounds (the 2nd group). These compounds are found to be characterized by of the following phase transitions: paramagnet ? ferrimagnet ? superconductor (retained ferrimagnetism) ? antiferromagnet (retained superconductivity). The latter transition to the antiferromagnetic state occurs only in the compounds of the 1st group. It is found that, for the DyRh3.8Ru0.2B4 compound, no traditional Meissner effect is observed but the so-called Volleben effect (paramagnetic Meissner effect) takes place.

Burkhanov, G. S.; Lachenkov, S. A.; Khlybov, E. P.; Dankin, D. G.; Kulikova, L. F.

2013-05-01

261

Synthesis, crystal structures, magnetic properties and catecholase activity of double phenoxido-bridged penta-coordinated dinuclear nickel(II) complexes derived from reduced Schiff-base ligands: mechanistic inference of catecholase activity.  

PubMed

Three double phenoxido-bridged dinuclear nickel(II) complexes, namely [Ni(2)(L(1))(2)(NCS)(2)] (1), [Ni(2)(L(2))(2)(NCS)(2)] (2), and [Ni(2)(L(3))(2)(NCS)(2)] (3) have been synthesized using the reduced tridentate Schiff-base ligands 2-[1-(3-methylamino-propylamino)-ethyl]-phenol (HL(1)), 2-[1-(2-dimethylamino-ethylamino)-ethyl]-phenol (HL(2)), and 2-[1-(3-dimethylamino-propylamino)-ethyl]-phenol (HL(3)), respectively. The coordination compounds have been characterized by X-ray structural analyses, magnetic-susceptibility measurements, and various spectroscopic methods. In all complexes, the nickel(II) ions are penta-coordinated in a square-pyramidal environment, which is severely distorted in the case of 1 (Addison parameter ? = 0.47) and 3 (? = 0.29), while it is almost perfect for 2 (? = 0.03). This arrangement leads to relatively strong antiferromagnetic interactions between the Ni(II) (S = 1) metal centers as mediated by double phenoxido bridges (with J values of -23.32 (1), -35.45 (2), and -34.02 (3) cm(3) K mol(-1), in the convention H = -2JS(1)S(2)). The catalytic activity of these Ni compounds has been investigated for the aerial oxidation of 3,5-di-tert-butylcatechol. Kinetic data analysis following Michaelis-Menten treatment reveals that the catecholase activity of the complexes is influenced by the flexibility of the ligand and also by the geometry around the metal ion. Electrospray ionization mass spectroscopy (ESI-MS) studies (in the positive mode) have been performed for all the coordination compounds in the presence of 3,5-DTBC to characterize potential complex-substrate intermediates. The mass-spectrometry data, corroborated by electron paramagnetic resonance (EPR) measurements, suggest that the metal centers are involved in the catecholase activity exhibited by the complexes. PMID:22759340

Biswas, Apurba; Das, Lakshmi Kanta; Drew, Michael G B; Aromí, Guillem; Gamez, Patrick; Ghosh, Ashutosh

2012-07-03

262

Process and Magnetic Properties of Rare-Earth Bonded Magnets  

Microsoft Academic Search

Bonded magnets can be manufactured by compression molding, extrusion, injection molding or calendering processes. For compression\\u000a molding, the magnet powders coated with epoxies are compression molded into required geometries and then cured at an appropriate\\u000a temperature. Bonded magnets manufactured by this process can be held to tight tolerances, which eliminates the need for secondary\\u000a or finish machining. For injection molding,

Jinfang Liu; Michael Walmer

263

Complex Dielectric Properties of Several Igneous and Metamorphic Rocks.  

National Technical Information Service (NTIS)

The complex dielectric properties of rocks are interesting scientifically and important practically. The scientific interest derives from a desire to understand the properties of materials, the electrical structure of the earth's crust, and the (electrica...

G. Simmons L. Caruso F. Miller

1980-01-01

264

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

265

Magnetic properties of iron-rich oxisols  

Microsoft Academic Search

Four occurrences of highly magnetic soil in Brazil have been analysed with a view to identifying the magnetic minerals and quantifying the soil magnetization. Techniques used include X-ray diffraction, X-ray fluorescence and Mössbauer spectroscopy. This approach leads us to identify several ways that these soils, which have spontaneous magnetization in the range 1s<35 J\\/T\\/kg, can come about.

Jacqueline E. M. Allan; J. M. D. Coey; Mauro Resende; J. D. Fabris

1988-01-01

266

Magnetic properties of Cr Fe Mn alloys  

Microsoft Academic Search

The magnetic behaviour of a Cr80-xFe20Mnx alloy system with x=2, 7, 10, 13 and 22 has been investigated in the temperature range 2 400 K through measurements of magnetization, electrical resistivity, magnetoresistivity, specific heat and thermal expansion. The temperature vs. Mn concentration magnetic phase diagram of the system is rich in magnetic behaviour with ferromagnetic (FM), antiferromagnetic (AFM) and paramagnetic

B. Li; H. L. Alberts; A. M. Strydom; B. M. Wu; A. R. E. Prinsloo; Zh. J. Chen

2009-01-01

267

Electronic structure and magnetic properties of solids  

Microsoft Academic Search

We review basic computational techniques for simulations of various magnetic\\u000aproperties of solids. Several applications to compute magnetic anisotropy\\u000aenergy, spin wave spectra, magnetic susceptibilities and temperature dependent\\u000amagnetisations for a number of real systems are presented for illustrative\\u000apurposes.

Sergej Y. Savrasov; A. Toropova; M. I. Katsnelson; A. I. Lichtenstein; Vladimir Antropov; Gabriel Kotliar

2005-01-01

268

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

269

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

270

Structure and magnetic properties of mechanically-alloyed SmZr(CoFe) nanophase hard magnets  

Microsoft Academic Search

Summary form only given. In the recent search for new high temperature permanent magnetic materials, research has concentrated on bulk Sm2Co17 type magnets. The usual approach to development of coercivity in these bulk materials is to prepare a nanophase cellular microstructure with cell walls which act as pinning sites. In this work, a systematic investigation of structural and magnetic properties

K. Gallagher; A. le Gouil; M. Venkatesan; J. M. D. Coey

2002-01-01

271

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

PubMed

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

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

2012-08-17

272

Are Polarization and Magnetization really Bulk Properties?  

NASA Astrophysics Data System (ADS)

Microscopic understanding of P and of (orbital) M was achieved only recently; the modern theories express both as BZ integrals. Since k-space is an artificial construct, all bulk properties must be embedded in the ground state density matrix ?(r,r'), ``nearsighted'' in insulators, independently of the boundary conditions, either periodic (PBCs) or open (OBCs). A basic tenet of the modern theory is that the bulk electron distribution determines P only modulo a ``quantum'': therefore P is not independent of the boundaries. Instead M is not affected by any quantum indeterminacy and an expression in terms of the bulk ? is not ruled out: we explicitly find such expression. In a finite homogeneous sample, within OBCs, the macroscopic magnetization is cast as a function of the bulk ?(r,r'). Remarkably, our approach applies even to topological (Chern) insulators, where M explicitly depends on the chemical potential. The boundary currents contribute to M, but even their contribution is ``bulk'' in the above sense; the value of M is robust and cannot be altered by acting on the boundaries only. Instead, P can be varied (by a quantum) by acting on the boundaries only. Simulations performed on a 2d model Hamiltonian within OBCs demonstrate our approach.

Bianco, Raffaello; Resta, Raffaele

2013-03-01

273

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

274

Bacterial magnetite and the magnetic properties of sediments in a Swedish lake  

NASA Astrophysics Data System (ADS)

A comparison of the magnetic properties of lake sediments and catchment materials from Pajep Njakajaure (north Sweden) demonstrates that high concentrations of single-domain (SD) magnetite in the upper 70 cm of gyttja in the deepest part of the basin are not of detrital origin. Transmission electron microscopy (TEM) and light microscope examination revealed the existence of bacterial cells and magnetosomes in the upper sediments which are responsible for the presence of the SD magnetite. Most of the fossil magnetosomes appear to have been dissolved through reductive processes at lower depths, although some are preserved in the lower sediments and carry a post-depositional remanent magnetization (PDRM). The results highlight the complex effects of post-depositional processes on mineral magnetic assemblages and natural remanent magnetization aquisition, and demonstrate how mineral magnetic measurements may be used to identify magnetic grain-size changes brought about by sediment diagenesis.

Snowball, Ian F.

1994-08-01

275

Magnetic property and electronic structure of itinerant PdxCoyO2 magnets  

NASA Astrophysics Data System (ADS)

The electronic structure of the delafossite-type compound PdCoO2 is calculated by the full potential linear muffin-tin orbital method and the magnetic property of the composition modified (defect injection introduced) compound Pd0.72Co0.68O2 was investigated. The calculation reveals that the density of states of PdCoO2 around the Fermi level is mainly composed of Pd 4d and Co 3d and O 2p orbitals, and the Fermi level is located just at the depression of the density of states. The magnetic nature of the composition modified Pd0.72Co0.68O2 compound is quite complex. The slow spin dynamics found below Tf can be interpreted by considering that the weak ferromagnetic moment in each CoO6 plane is itself disordered. This behavior is explained by the short-range character of the randomness which leads to a finite-size magnetized cluster, and suggests that the presence of these clusters would induce a spin-glass like feature for T

Okabe, H.; Matoba, M.; Kyomen, T.; Itoh, M.

2003-05-01

276

Complex magnetic fields enable static magnetic field cue use for rats in radial maze tasks.  

PubMed

Male Wistar rats were trained in an eight-arm radial maze task (two sessions per day, delayed-non-matching-to-sample) that included an intramaze static magnetic field "cue" (185 microT) specific to the entrance point of one of the arms. Rats were exposed daily for 60 min to a complex magnetic field waveform (theta-burst pattern, 200-500 nT), presented with several different interstimulus intervals (ISIs), either immediately following training sessions or immediately preceding testing sessions. Application of the theta-burst stimulus with a 4000 ms ISI significantly improved the rats' memory for the arm of the radial maze whose position was indicated by the presence of a static magnetic field cue. Reference memory errors were homogeneously distributed among all eight arms of the maze for sham-exposed rats, and among the other seven arms of the maze for complex magnetic field-treated rats. These results suggest that static magnetic field cues may be salient orienting cues even in a microenvironment such as a radial maze, but their use as a cue during maze learning in rats is dependent on whole-body application of a specific time-varying complex magnetic field. PMID:15823929

McKay, B E; Persinger, M A

2005-05-01

277

Structure and Magnetic Properties of Low Neodymium Magnets Containing Minor Addition of Molybdenum  

Microsoft Academic Search

Rapidly solidified nanocomposite Nd9Fe77-xB14Mox alloys, consisting of magnetic Nd2Fe14B phase and soft magnetic phases, were investigated. The effect of the molybdenum addition on the structure and magnetic properties was studied. It was found that 3-4 at% Mo addition leads to a substantial increase of the coercivity and maximum energy product maintaining the remanence to be almost unchanged. The highest properties

Marzena Spyra; Marcin Leonowicz

2008-01-01

278

Synthesis and fluorescence properties of pyrimidine mono- and bisboron complexes.  

PubMed

Novel fluorescent mono- and bisboron complexes based on pyrimidine bearing ?-iminoenolate ligands were synthesized, and their fluorescence properties were investigated. The nonsubstituted and trifluoromethyl-substituted monoboron complexes showed higher fluorescence quantum yield in solid state than in solution. The dimethylamino derivative of the monoboron complex exhibited positive solvatochromism in the fluorescence spectra. The bisboron complex showed significantly higher molar absorption coefficient and red-shifted maximum absorption and maximum fluorescence wavelengths than the corresponding monoboron complex. PMID:23829606

Kubota, Yasuhiro; Ozaki, Yousuke; Funabiki, Kazumasa; Matsui, Masaki

2013-07-05

279

Intrinsic and extrinsic magnetic properties of the naturally layered manganites  

SciTech Connect

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

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

1999-11-30

280

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

National Technical Information Service (NTIS)

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

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

1990-01-01

281

Tunable magnetic properties in ultrathin Co/garnet heterostructures  

NASA Astrophysics Data System (ADS)

We demonstrate how the magnetic properties of metal/dielectric Co/yttrium iron garnet heterostructures can be engineered by both changing the garnet thickness and adding an ultrathin Co cover layer. The observed magnetization reversal process in the heterostructures is explained by both cubic and perpendicular growth-induced magnetic anisotropy of the garnet films. In particular, the perpendicular magnetic anisotropy can be strongly increased for reduced thickness. A strong influence of a 2 nm Co layer on the domain structure geometry and magnetization processes has been found for 1.8 µm garnet films.

Pashkevich, M.; Stupakiewicz, A.; Kirilyuk, A.; Maziewski, A.; Stognij, A.; Novitskii, N.; Kimel, A.; Rasing, Th.

2012-01-01

282

Magnetic Properties of Magnetic Fluids near Melting Point  

Microsoft Academic Search

The magnetization (M), field-induced magnetic anisotropy (Ku), rotational hysteresis loss (Erot) and melting point (Tm) of water-and paraffin-base ferrofluids were investigated in the temperature range from 77 K~300°K, as functions of the density of the colloidal particles. Both paraffin and paraffin-base fluids were melted down at temperatures between 180 and 210°K. In this range, the values of M and Erot

N. Inaba; H. Miyajima; S. Taketomi; S. Chikazumi

1990-01-01

283

Low complexity turbo equalization for high density magnetic recording  

Microsoft Academic Search

In the context of iterative decoding and equalization (a.k.a. turbo equalization) of high density magnetic recording (MR) channels, we propose a low complexity soft-in soft-out (SISO) algorithm which implements the constrained delay a-posteriori probability (CD-APP) estimation utilizing either hard or soft decision feedback (HDF\\/SDF). Through BER simulation, we show that for an MR channel with user density 3.2, our proposed

Farshid Rafiee Rad; Jaekyun Moon

2005-01-01

284

Complex polarization propagator calculations of magnetic circular dichroism spectra  

NASA Astrophysics Data System (ADS)

It is demonstrated that the employment of the nonlinear complex polarization propagator enables the calculation of the complete magnetic circular dichroism spectra of closed-shell molecules, including at the same time both the so-called Faraday and terms. In this approach, the differential absorption of right and left circularly polarized light in the presence of a static magnetic field is determined from the real part of the magnetic field-perturbed electric dipole polarizability. The introduction of the finite lifetimes of the electronically excited states into the theory results in response functions that are well behaved in the entire spectral region, i.e., the divergencies that are found in conventional response theory approaches at the transition energies of the system are not present. The applicability of the approach is demonstrated by calculations of the ultraviolet magnetic circular dichroism spectra of para-benzoquinone, tetrachloro-para-benzoquinone, and cyclopropane. The present results are obtained with the complex polarization propagator approach in conjunction with Kohn-Sham density functional theory and the standard adiabatic density functionals B3LYP, CAM-B3LYP, and BHLYP.

Solheim, Harald; Ruud, Kenneth; Coriani, Sonia; Norman, Patrick

2008-03-01

285

Matching Martian Magnetic Anomalies and Snc Magnetic Properties  

NASA Astrophysics Data System (ADS)

Understanding the origin of Martian magnetic anomalies is a major challenge for Martian studies, both in terms of planetary geodynamics and of magnetic petrology. Present models require a crustal magnetization of 15-30 A/m with a thickness of 20-50 km [e.g. 1]. SNC meteorites are the only material available to make a magnetominer- alogical model for this crustal magnetization. Here will be presented a synthesis based on 16 independant SNCs, with all the falls and non Antarctic finds except NWA480. Titanomagnetite is the major magnetic carrier only in the four Nakhlites, Los Angeles, ALH75005 and Chassigny. Due to high titanium substitution, the Curie point based on high temperature magnetic measurements or microprobe analysis is only about 150C in the nakhlites and Los Angeles. High coercivity pyrrhotite is the major car- rier in the other eight basaltic shergottites measured. We estimate in-situ NRM for SNCs Noachian equivalent by using saturation remanent magnetization and use the proposed upper bound of 5% for NRM/IRM in case of TRM in an Earth-like field for magnetite or pyrrhotite Taking the lower bound of 15 A/m for crustal NRM and a density of 3 leads to a minimum Mrs of 10-1 Am2/kg. Only Los Angeles, NWA817 and 1068, i.e. the most magnetic Nakhlites and basaltic shergottites, are above this threshold. ALH84001, the only SNC with the right age, is two orders of magnitude below, like Chassigny, while lherzolitic ALH75005 is one order of magnitude below. This confirms the contention that magnetic sources are rather mafic than ultramafic rocks. Titanomagnetite is the preferred candi-date mineral in the litterature but the Curie point of 150C found on SNCs is at odd with a Curie depth of 20-50 km during NRM acquisition. Although fundamental drawbacks exist in the use of SNCs to put forward a magnetomineralogical model for magnetic anomalies, sulfides appear as a serious alternative to oxydes in the martian case.

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

286

Alternating antiferromagnetic and ferromagnetic exchange interactions in the S = 1 Heisenberg chain. Theory and magnetic properties  

NASA Astrophysics Data System (ADS)

We focus on the magnetic properties of the S = 1 Heisenberg chain with alternating antiferromagnetic and ferromagnetic exchange interactions J1 and J2. The magnetic behavior of this system is calculated as a function of the alternation parameter ? = J2/| J1|, from a general numerical procedure based on closed spin chains of increasing length. These theoretical results are fitted to rational unified expressions, which are subsequently used to describe the magnetic behavior of a nickel (II) complex, [Ni(bipy)(N 3) 2] n, exhibiting an alternating chain structure with a dominant ferromagnetic exchange.

Borrás-Almenar, Juan J.; Clemente-Juan, Juan M.; Coronado, Eugenio; Lloret, Francesc

1997-08-01

287

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

288

Properties of Magnetic Neutral Lines and Filament Formation  

NASA Astrophysics Data System (ADS)

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

Karachik, N.; Pevtsov, A. A.

2011-12-01

289

Electrostatic Properties of Protein-Protein Complexes  

Microsoft Academic Search

Statistical electrostatic analysis of 37 protein-protein complexes extracted from the previously developed database of protein complexes (ProtCom, http:\\/\\/www.ces.clemson.edu\\/compbio\\/protcom) is presented. It is shown that small interfaces have a higher content of charged and polar groups compared to large interfaces. In a vast majority of the cases the average pKa shifts for acidic residues induced by the complex formation are negative,

Petras J. Kundrotas; Emil Alexov

2006-01-01

290

The magnetic properties of powdered and compacted microcrystalline permalloy  

NASA Astrophysics Data System (ADS)

The aim of this work is to investigate the magnetic properties of powdered and compacted microcrystalline Ni Fe (81 wt% of Ni) permalloy. It was found by investigating the influence of mechanical milling on the magnetic properties of powder samples prepared by milling of the ribbon that the alloy remains a solid solution with stable structure during the whole milling process. With decreasing particle size the rotation of magnetization vector gradually becomes dominant magnetization process and thus coercivity increases. After compaction of the powder by uniaxial hot pressing the magnetic contact between powder particles is recreated and for resulting bulk the displacement of the domain walls becomes dominant magnetization process with coercivity of 11 A/m (comparable with the coercivity of conventional permalloy).

Kollár, P.; Olekšáková, D.; Füzer, J.; Ková?, J.; Roth, S.; Pola?ski, K.

2007-03-01

291

Spectroscopic Properties of Antenna Complexes from Purple Bacteria  

Microsoft Academic Search

This chapter describes the known factors which shape the electronic (and thus the functional) properties of light-harvesting\\u000a (LH) complexes of purple bacteria. Although a variety of high- and low-resolution structures from LH complexes are now available,\\u000a they do not provide, per se, a detailed picture of the electronic properties of the pigments in these complexes. However they\\u000a constitute a framework

Bruno Robert

292

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

SciTech Connect

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

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

2011-04-01

293

Complex magnetism of the Fe monolayer on Ir(111)  

Microsoft Academic Search

The electronic and magnetic properties of Fe on Ir(111) have been investigated experimentally by spin-polarized scanning tunneling microscopy (SP-STM) and theoretically by first-principles calculations based on density functional theory. While the growth of an Fe monolayer is in-plane commensurate, deposition of a double-layer shows a rearrangement of atoms due to strain relief accompanied by local variations of the electronic structure.

Kirsten von Bergmann; Stefan Heinze; Matthias Bode; Gustav Bihlmayer; Stefan Blügel; Roland Wiesendanger

2007-01-01

294

Magnetic properties of iron-rich Fe-Zr glasses  

Microsoft Academic Search

A systematic study of the magnetic properties of melt-spun amorphous Fe\\/sub x\\/Zrââââ\\/sub x\\/ alloys with 88less than or equal toxless than or equal to93 using Moessbauer and magnetization measurements has established the magnetic phase diagram. The ordering temperature T\\/sub c\\/ falls sharply with increasing x; below a second transition T\\/sub x\\/\\/sub y\\/, associated with the freezing of transverse-spin components, all

D. H. Ryan; J. M. D. Coey; E. Batalla; Z. Altounian; J. O. Stroem-Olsen

1987-01-01

295

Processing, properties and some novel applications of magnetic nanoparticles  

Microsoft Academic Search

Magnetic nanoparticles have been prepared by various soft chemical methods including self-assembly. The bare or surface-modified\\u000a particles find applications in areas such as hyperthermia treatment of cancer and magnetic field-assisted radioactive chemical\\u000a separation. We present here some of the salient features of processing of nanostructured magnetic materials of different sizes\\u000a and shapes, their properties and some possible applications. The materials

D. Bahadur; J. Giri; Bibhuti B. Nayak; T. Sriharsha; P. Pradhan; N. K. Prasad; K. C. Barick; R. D. Ambashta

2005-01-01

296

The Preparation and Magnetic Properties of Iron Oxide Particles  

Microsoft Academic Search

Samples of spherical hematite particles of narrow size distribution with mean diameters ranging between 0.065 and 0.62 (mu)m have been prepared by homogeneous precipitation. Magnetic properties of these particles were examined as a function of temperature (80 to 295 K) and applied magnetic field (to 24,000 Oe). It was observed that so prepared and annealed particles possess magnetic defects. The

Nurul Amin

1987-01-01

297

Magnetic properties of neodymium-samarium-cobalt alloys  

Microsoft Academic Search

The purpose of this investigation is to determine the magnetic properties of the pseudo-binary alloy system Nd(1-x)Sm(x)Co5, in particular the variation of the magnetization and magnetocrystalline anisotropy with temperature and composition. The special interest in these variables stems from their quantitative relationships to magnetic domain wall characteristics and the relationship of domain walls to RCo5 coercivity, the key parameter in

W. G. D. Frederick; H. J. Garrett; M. Hoch

1975-01-01

298

Magnetic properties of some iron-poor natural olivines  

NASA Astrophysics Data System (ADS)

Three natural iron-poor samples of the forsterite-fayalite solid-solution series were studied by Mössbauer spectroscopy and magnetization measurements to determine their magnetic properties. The samples exhibit a normal para- to antiferromagnetic transition at low temperatures. The paramagnetic susceptibility follows a Curie-Weiss law at temperatures above 60 K. The Mössbauer spectra of the samples at low temperatures are interpreted as due to different magnetic environmental configurations of Fe2+ in two distinct crystallographic sites.

de Oliveria, J. C. P.; da Costa, M. I.; Schreiner, W. H.; Vasquez, A.

1991-08-01

299

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

NASA Astrophysics Data System (ADS)

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

Wang, Xiang; Pu, Shengli; Ji, Hongzhu; Yu, Guojun

2012-05-01

300

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

PubMed

Ferronematic materials composed of 4-cyano-4'-pentylbiphenyl nematic liquid crystal and oil-based Fe3O4 magnetic fluid were prepared using ultrasonic agitation. The birefringence (?n) and figure of merit of optical properties (Q?=??n/?, where ? is the extinction coefficient) of pure magnetic fluids and the as-prepared ferronematic materials were examined and compared. The figure of merit of optical properties weighs the birefringence and extinction of the materials and is more appropriate to evaluate their optical properties. Similar magnetic-field- and magnetic-particle-concentration-dependent properties of birefringence and figure of merit of optical properties were obtained for the pure magnetic fluids and the ferronematic materials. For the ferronematic materials, the values of Q increase with the volume fractions of nematic liquid crystal under certain fixed field strength and are larger than those of their corresponding pure magnetic fluids at high field region. In addition, the enhancement of Q value increases monotonously with the magnetic field and becomes remarkable when the applied magnetic field is beyond 50 mT. The maximum relative enhanced value of QR exceeds 6.8% in our experiments. The results of this work may conduce to extend the pragmatic applications of nanostructured magnetic fluids in optical field. PMID:22587542

Wang, Xiang; Pu, Shengli; Ji, Hongzhu; Yu, Guojun

2012-05-15

301

Magnetic Properties of Beta-Uranium Hydride  

Microsoft Academic Search

A thorough magnetic investigation of beta-uranium hydride has been carried out. The curve of reciprocal paramagnetic susceptibility against temperature generally follows the Curie-Weiss law and shows the same curvatures near the Curie point and at high temperatures as do the data for the ferromagnetic elements above their Curie points. A considerable number of magnetization curves have been obtained for a

S. T. Lin; A. R. Kaufmann

1956-01-01

302

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

303

MAGNETIC PROPERTIES OF IRON-BERYLLIUM COMPOUNDS WITH HEXAGONAL STRUCTURE  

Microsoft Academic Search

Polycrystalline specimen (beta-phase) Fe-Be compounds were prepared with ; 71.0 and 68.0 at.% Be in vacuum induction furnace. Data are given for ; crystallographic and magnetic properties and magnetic anisotropy, including ; temperature levels in deg K, Curie temperature, and deg C, liquid O level, and ; the system phase diagrain. (P.C.H.);

K. Ohta; Y. Kobayshi

1961-01-01

304

Magnetic properties of dense holographic QCD  

SciTech Connect

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 pseudoscalar 'pion', which carries a nonvanishing 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 a large magnetic field.

Bergman, Oren; Lifschytz, Gilad; Lippert, Matthew [School of Natural Sciences, Institute for Advanced Study, Princeton, New Jersey 08540 (United States); Department of Mathematics and Physics and CCMSC, University of Haifa at Oranim, Tivon 36006 (Israel); Department of Physics, Technion, Haifa 32000, Israel and Department of Mathematics and Physics, University of Haifa at Oranim, Tivon 36006 (Israel)

2009-05-15

305

Influence of switchable magnetic field on the modulation property of nanostructured magnetic fluids  

NASA Astrophysics Data System (ADS)

Magnetic fluid is a kind of colloidal material with tunable microstructure and unique optical properties. The tunable magneto-optical modulation property of magnetic fluid under externally switchable magnetic field with various modulation periods is investigated theoretically and experimentally. The transitional modulation period (lower limit of the working frequency) between the square-like and oscillation-like modulation is achieved and found to be magnetic-field- and sample-concentration-dependent. The modulation mechanism is analyzed and ascribed to the dynamic microstructure of magnetic fluid under different modulation periods of external magnetic fields. The result of this work may be helpful for the pragmatic applications of magnetic fluid based on the square-like modulation.

Ji, Hongzhu; Pu, Shengli; Wang, Xiang; Yu, Guojun

2012-10-01

306

Magnetic Properties of Compositionally Modulated Cu-Ni Thin Films  

NASA Astrophysics Data System (ADS)

The magnetic properties of modulated Cu-Ni films with Ni thickness ranging from 6 to 60 Å and for various Cu thickness have been measured at room temperature, 77°K, and 4.2°K. The results show that the magnetic properties do not depend on the Cu thickness but only on the surface to volume ratio of the Ni. The Ni behavior is interpreted in terms of a large surface anisotropy, and not in terms of an enhanced moment.

Gyorgy, E. M.; Dillon, J. F., Jr.; McWhan, D. B.; Rupp, L. W., Jr.; Testardi, L. R.; Flanders, P. J.

1980-07-01

307

Magnetic Properties of Compositionally Modulated Cu-Ni Thin Films  

Microsoft Academic Search

The magnetic properties of modulated Cu-Ni films with Ni thickness ranging from 6 to 60 Å and for various Cu thickness have been measured at room temperature, 77°K, and 4.2°K. The results show that the magnetic properties do not depend on the Cu thickness but only on the surface to volume ratio of the Ni. The Ni behavior is interpreted

E. M. Gyorgy; J. F. Dillon Jr.; D. B. McWhan; L. W. Rupp Jr.; L. R. Testardi; P. J. Flanders

1980-01-01

308

Magnetic, structural and computational studies on transition metal complexes of a neurotransmitter, histamine  

NASA Astrophysics Data System (ADS)

In this study, the transition metal complexes of histamine (His) prepared with oxalate (Ox), that is, [Cu(His)(Ox)(H2O)], [Zn(His)(Ox)(H2O)] (or [Zn(His)(Ox)]·(H2O)), [Cd(His)(Ox)(H2O)2] and [Co(His)(Ox)(H2O)], are investigated experimentally and computationally as part of ongoing studies on the mode of complexation, the tautomeric form and non-covalent interactions of histamine in supramolecular structures. The structural properties of prepared complexes are experimentally studied by X-ray diffraction (XRD) technique and Fourier transform infrared (FT-IR) spectroscopy and computationally by density functional theory (DFT). The magnetic properties of the complexes are investigated by electron paramagnetic resonance (EPR) technique. The [Cu(His)(Ox)(H2O)] complex has a supramolecular structure constructed by two different non-covalent interactions as hydrogen bond and C-H\\ctdot ? interactions. EPR studies on [Cu(His)(Ox)(H2O)], Cu2+-doped [Zn(His)(Ox)(H2O)] and [Cd(His)(Ox)(H2O)2] complexes show that the paramagnetic centers have axially symmetric g values. It is also found that the ground state of the unpaired electrons in the complexes is dominantly d and unpaired electrons' life time is spent over this orbital.

Ka?ta?, Gökhan; Pa?ao?lu, Hümeyra; Karabulut, Bünyamin

2011-08-01

309

The magnetic properties experiments on Mars Pathfinder  

NASA Astrophysics Data System (ADS)

The Mars Pathfinder lander carried two magnet arrays, each containing five small permanent magnets of varying strength. The magnet arrays were passively exposed to the wind borne dust on Mars. By the end of the Mars Pathfinder mission a bull's-eye pattern was visible on the four strongest magnets of the arrays showing the presence of magnetic dust particles. From the images we conclude that the dust suspended in the atmosphere is not solely single phase particles of hematite (?-Fe2O3) and that single phase particles of the ferrimagnetic minerals maghemite (?-Fe2O3) or magnetite (Fe3O4) are not present as free particles in any appreciable amount. The material on the strongest magnets seems to be indistinguishable from the bright surface material around the lander. From X-ray fluorescence it is known that the soil consists mainly of silicates. The element iron constitutes about 13% of the soil. The particles in the airborne dust seem to be composite, containing a few percent of a strongly magnetic component. We conclude that the magnetic phase present in the airborne dust particles is most likely maghemite. The particles thus appear to consist of silicate aggregates stained or cemented by ferric oxides, some of the stain and cement being maghemite. These results imply that Fe2+ ions were leached from the bedrock, and after passing through a state as free Fe2+ ions in liquid water, the Fe2+ was oxidized to Fe3+ and then precipitated. It cannot, however, be ruled out that the magnetic particles are titanomagnetite (or titanomaghemite) occurring in palagonite, having been inherited directly from the bedrock.

Madsen, M. B.; Hviid, S. F.; Gunnlaugsson, H. P.; Knudsen, J. M.; Goetz, W.; Pedersen, C. T.; Dinesen, A. R.; Mogensen, C. T.; Olsen, M.; Hargraves, R. B.

1999-04-01

310

Combining magnetic field induced locomotion and supramolecular interaction to micromanipulate glass fibers: toward assembly of complex structures at mesoscale.  

PubMed

The formation of ordered complex structures is one of the most challenging fields in the research of biomimic materials because those structures are promising with respect to improving the physical and mechanical properties of man-made materials. In this letter, we have developed a novel approach to fabricating complex structures on the mesoscale by combining magnetic-field-induced locomotion and supramolecular-interaction-assisted immobilization. We have employed a magnetic field to locomote the glass fiber, which was modified by the layer-by-layer self-assembly of magnetic nanoparticles, to desired positions and have exploited the supramolecular interaction to immobilize glass fiber onto the appointed position. By magnetically induced micromanipulation, we can drive another fiber across the former one and finally obtain a crossing structure, which can lead to more complex structures on the mesocale. Moreover, we have constructed a mesoscale structure, termed "CHEM", to demonstrate further the application of this method. PMID:21542598

Cheng, Mengjiao; Gao, Haitao; Zhang, Yajun; Tremel, Wolfgang; Chen, Jian-Feng; Shi, Feng; Knoll, Wolfgang

2011-05-04

311

Exotic Magnetic Properties in {sup 17}C  

SciTech Connect

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

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

2008-12-15

312

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

PubMed Central

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

Nishida, Keiji; Silver, Pamela A.

2012-01-01

313

Electrical Properties of Nanostructured Magnetic Colloid and Influence of Magnetic Field  

NASA Astrophysics Data System (ADS)

We investigate the electrical properties of the nanostructured magnetic colloid without and with magnetic field. The competition between the directional motion of the charged magnetic nanoparticles and other minor nonmagnetic impurities (also small amount of ions) under applied voltage and their random orientation due to thermal activation is implemented to elaborate the electrically conduction mechanism under zero magnetic field. Two equivalent electric circuits are employed for explaining the charging and discharging processes. The tunnelling conduction mechanism upon application of externally magnetic field may exist in the nanostructured magnetic colloid. The alternation of the two conduction mechanisms accounts for the current spikes when the magnetic field is switched on or off. This work presents the peculiar electrical phenomena of the magnetically colloidal system.

Pu, Sheng-Li; Chen, Xian-Feng; Di, Zi-Yun; Geng, Tao; Xia, Yu-Xing

2007-11-01

314

Properties of Magnetic Nanoparticles for Magnetic Immunoassays Utilizing a Superconducting Quantum Interference Device  

NASA Astrophysics Data System (ADS)

Properties of magnetic nanoparticles are studied for application to magnetic immunoassays utilizing a superconducting quantum interference device (SQUID). In this application, a magnetic marker is made of magnetic nanoparticles, and the binding reaction between an antigen and its antibody is detected by measuring the magnetic field from the marker. Magnetization of an assembly of the particles is simulated when the effects of the thermal noise and the distribution of the particle size are taken into account. Magnetic signals from the assembly of the particles are clarified for three detection methods, i.e., susceptibility, relaxation and remanence. From the comparison with experimental results, it was shown that the demagnetization effect also significantly influences the magnetic signal from the particles. When these effects are taken into account, the simulation results agree semi-quantitatively with the experimental ones.

Enpuku, Keiji; Inoue, Katsuhiro; Soejima, Kazuyuki

2005-01-01

315

Hard magnetic properties of FePd nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

316

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

317

Magnetic and microstructure properties of iron-rare earth-boron magnets  

SciTech Connect

The new generation of cobalt-free Fe-Nd-B permanent magnets have excellent hard magnetic properties attributed to a tetragonal Fe/sub 14/Nd/sub 2/B phase that has a high anisotropy and a high magnetic moment. The purpose of this work was 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 was found to drop drastically with partial substitution of Fe by Ni, Mn and B by C, Si. The origin of high coercivity was examined by correlating the hard magnetic properties with the microstructure. The high coercivities can be explained by domain wall pinning at grain boundaries.

Tao, Y.F.

1986-01-01

318

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

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

319

Properties of Magnetized Quark-Hybrid Stars  

NASA Astrophysics Data System (ADS)

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

Orsaria, Milva; Ranea-Sandoval, Ignacio F.; Vucetich, H.; Weber, Fridolin

320

Magnetic and transport properties of the ? alloys  

Microsoft Academic Search

Magnetization and transport measurements have been performed to study the martensitic and pre-martensitic transitions for a series of ferromagnetic Heusler 0953-8984\\/11\\/13\\/016\\/img10 alloys. Both magnetization and resistivity measurements show a clear jump at the martensitic transition and a discontinuous slope change at the pre-martensitic transition. The characteristic temperatures correspond well with those derived from previous direct structural results from neutron scattering,

F. Zuo; X. Su; P. Zhang; G. C. Alexandrakis; F. Yang; K. H. Wu

1999-01-01

321

Magnetic properties and structure of oxyhemoglobin.  

PubMed Central

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 bond lengths and bound angles for carbonmonoxyhemoglobin and oxyhemoglobin are given.

Pauling, L

1977-01-01

322

Two-dimensional Magnetic Properties Of Silicon Steel Sheet Under Rotating Field  

Microsoft Academic Search

rbstract We have studied the new concept regard on rotational magnetic properties which is called twoimensional rotational magnetic properties. It is measured making use of the vector relation between magnetic field trength H and magnetic flux density B. ntroduction The evaluation of magnetic properties in materials is very important to develop he highly efficient electrical machine and apparatus. Also the

M. Enokizono; T. Todaka; S. Kanao; J. Sievert

1993-01-01

323

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

324

Magnetic properties of PdNi alloys and multilayers  

NASA Astrophysics Data System (ADS)

Magnetic properties of PdNi alloys and multilayers (MLs) were investigated. The alloy films sputtered at higher Ar pressure exhibit uniaxial magnetic anisotropy Ku with the easy axis perpendicular to the film plane. This anisotropy is ascribed to the stress due to substrate constraint. Perpendicular magnetic anisotropy of the MLs sputtered under nearly stress-free conditions increases with decreasing bilayer period and the perpendicular magnetization is realized for the bilayer period of 15 Å. The surface anisotropy is estimated to be about 0.05 erg/cm2.

Takahashi, H.; Tsunashima, S.; Fukatsu, S.; Uchiyama, S.

1991-02-01

325

Complexities in diluted magnetic semiconductors-a theoretical perspective from ab-initio electronic structure calculations  

NASA Astrophysics Data System (ADS)

Diluted magnetic semiconductors (DMS), the essential materials for semiconductor spintronics, show a variety of complex properties, e.g., defect-mediated (ferro/antiferro)magnetic interactions and the disorder leading to magnetic percolation effects. Using the ab-initio Korringa-Kohn-Rostoker-Coherent-Potential-Approximation, the magnetic pair exchange parameters of a Heisenberg model have been calculated for Mn doped ZnO and half-Heusler NiTiSn hosts followed by the calculation of transition temperatures using Monte-Carlo simulations. Zinc vacancies and nitrogen substituting oxygen atoms lead to ferromagnetic interactions in Mn doped ZNO while in a defect free case, the interaction between Mn atoms is antiferromagnetic. The calculated critical temperatures are low (˜35 K) due to the short-ranged exchange interactions and low defect concentration. In the other case, Mn doped NiTiSn shows a high critical temperature (˜300 K) for 22 % Mn concentration. Below 3% Mn, there is no magnetic long range order as the magnetic percolation is not established. The results are in good agreement with experiments.

Sanyal, Biplab; Iusan, Diana; Eriksson, Olle

2007-03-01

326

Magnetic properties of ferromagnetic nanowire arrays: Theory and experiment  

NASA Astrophysics Data System (ADS)

Magnetic nanowires are good candidates for microwave filters, sensors and data storage applications. An investigation of magnetic properties of single-component nanowires as a function of diameter and aspect ratio is performed in this work. Nickel nanowire (with 15 and 100 nm diameter and 6000 nm length) are grown with electrodeposition in polycarbonates templates. Two reversal modes (coherent and curling) are studied versus nanowire diameter. Magnetostatic interaction among wires and its effect on nanowire magnetic properties is also studied. Using vibrating magnetometer (VSM) and X-band ferromagnetic resonance (FMR) experiments at room temperature we infer that the interaction field Hc value may vary significantly and may cause a change of magnetic easy axis orientation along geometrical wire axis (for large diameter) to an easy magnetic plane perpendicular to the nanowire axis (for small diameter).

Ghaddar, A.; Gloaguen, F.; Gieraltowski, J.

2010-01-01

327

Effects of prestraining on the magnetic properties of 4340 steels  

NASA Astrophysics Data System (ADS)

The use of the magnetization method for assessing the extent of monotonically prestrained levels in 4340 steels is addressed in order to determine whether magnetic inspection techniques can be used to provide advanced indications of the likely problems related to failure or degradation of material resulting from monotonic or cyclic prestrain. Magnetic property measurements provided clear indications of the material strength levels in the steel samples. The increasing number of dislocations due to prestraining produces an increase in the yield strength and the coercivity. The coercivity can thus be used as an indication of the yield strength of the material. The correlations between the magnetic properties and material strength levels were not as clear for the cyclically prestrained specimens due to the shape of the dislocation network after cycling. Plastic deformation gradients were also found to affect the magnetic hysteresis measurements.

Devine, M. K.; Apostol, J.; Jiles, D. C.; Liaw, P. K.

328

Fabrication and magnetic property of MnB alloy  

SciTech Connect

Manganese is a common dopant to achieve dilute magnetic semiconductors. Most magnetic semiconductors are hole-type and the Curie temperature is critically depending on the holes concentration. Boron can be used to increase the holes concentration and enhance the Curie temperature. In systems with both Mn and B dopants, one must consider the magnetic properties of MnB. In this study, single phase MnB alloy has been fabricated and characterized. Magnetic properties have been studied using superconducting quantum interference device and vibrating sample magnetometer over a broad temperature range. Very high magnetization of about 113 emu/g at room temperature has been observed, which is much higher than previous reports. The Curie temperature is around 306 deg. C, similar to previously reported value.

Zhu Hao; Ni Chaoying; Zhang Fengming; Du Youwei; Xiao, John Q. [Physics and Astronomy Department, University of Delaware, Room 223, Sharp Laboratory, Newark, Delaware 19716 (United States); Material Science and Engineering, University of Delaware, 022 Spencer Laboratory, Newark, Delaware 19716 (United States); National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, 22 Hankou Rd., Nanjing 210093 (China); Physics and Astronomy Department, University of Delaware, Room 223, Sharp Laboratory, Newark, Delaware 19716 (United States)

2005-05-15

329

Analysis of magnetic properties of the European XFEL undulator prototype  

NASA Astrophysics Data System (ADS)

In this contribution, we present an analysis of the experimentally measured magnetic field data from the planar hybrid 40 mm period undulator prototype for the European XFEL, and a simulation of expected radiation properties. Because of manufacturing errors, the magnetic field data include a small horizontal component, as well as some irregularities in its vertical (leading) component. A Fourier harmonics analysis was carried out. It was found that the vertical component of the measured magnetic field includes a sufficiently noticeable (about 6 percent relative to the fundamental) third harmonic component in addition to the fundamental harmonic. The spontaneous radiation properties are simulated from the experimentally measured magnetic field. Relying on computed radiation distributions, the effective magnetic field amplitude, the effective undulator period and deflection parameter are calculated.

Tomin, S.; Smolyakov, N.; Geloni, G.; Pflueger, J.; Li, Y.

2013-03-01

330

Complex windmill transformation producing new purely magnetic fluids  

NASA Astrophysics Data System (ADS)

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

Lozanovski, C.; Wylleman, L.

2011-04-01

331

The effects of magnetic nanoparticle properties on magnetic fluid hyperthermia  

NASA Astrophysics Data System (ADS)

Magnetic fluid hyperthermia (MFH) is a noninvasive treatment that destroys cancer cells by heating a ferrofluid-impregnated malignant tissue with an ac magnetic field while causing minimal damage to the surrounding healthy tissue. The strength of the magnetic field must be sufficient to induce hyperthermia but it is also limited by the human ability to safely withstand it. The ferrofluid material used for hyperthermia should be one that is readily produced and is nontoxic while providing sufficient heating. We examine six materials that have been considered as candidates for MFH use. Examining the heating produced by nanoparticles of these materials, barium-ferrite and cobalt-ferrite are unable to produce sufficient MFH heating, that from iron-cobalt occurs at a far too rapid rate to be safe, while fcc iron-platinum, magnetite, and maghemite are all capable of producing stable controlled heating. We simulate the heating of ferrofluid-loaded tumors containing nanoparticles of the latter three materials to determine their effects on tumor tissue. These materials are viable MFH candidates since they can produce significant heating at the tumor center yet maintain the surrounding healthy tissue interface at a relatively safe temperature.

Kappiyoor, Ravi; Liangruksa, Monrudee; Ganguly, Ranjan; Puri, Ishwar K.

2010-11-01

332

Magnetic properties and heavy metal contents of automobile emission particulates*  

PubMed Central

Measurements of the magnetic properties and total contents of Cu, Cd, Pb and Fe in 30 automobile emission particulate samples indicated the presence of magnetic particles in them. The values of frequency dependent susceptibility (? fd) showed the absence of superparamagnetic (SP) grains in the samples. The IRM20 mT (isothermal remanent magnetization at 20 mT) being linearly proportional to SIRM (saturation isothermal remanent magnetization) (R 2=0.901), suggested that ferrimagnetic minerals were responsible for the magnetic properties of automobile emission particulates. The average contents of Cu, Cd, Pb and Fe in automobile emission particulates were 95.83, 22.14, 30.58 and 34727.31 mg/kg, respectively. Significant positive correlations exist between the magnetic parameters and the contents of Pb, Cu and Fe. The magnetic parameters of automobile emission particulates reflecting concentration of magnetic particles increased linearly with increase of Pb and Cu content, showed that the magnetic measurement could be used as a preliminary index for detection of Pb and Cu pollution.

Lu, Sheng-gao; Bai, Shi-qiang; Cai, Jing-bo; Xu, Chang

2005-01-01

333

Properties of Microwave Cavities Containing Magnetic Resonant Samples  

Microsoft Academic Search

Properties of TE011 cylindrical, microwave cavities containing cylindrical samples of various radii and dielectric constants are calculated. The properties considered are the resonant frequency, quality factor (Q), relevant magnetic filling factor for spin transitions (&eegr;), and a signal sensitivity factor (Q&eegr;) for a lossless sample. Sample sizes range from zero radius to full cavity radius with some experimental data on

Kathy A. Rages; Robert E. Sawyer; Edward B. Hale

1973-01-01

334

Electric and Magnetic Properties of Transition Metals and Their Compounds.  

National Technical Information Service (NTIS)

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

1976-01-01

335

Focusing properties of a plane wiggler magnetic field  

NASA Astrophysics Data System (ADS)

We have considered the focusing properties of an inhomogeneous magnetic field. General analytic formulae for the horizontal and vertical properties are deduced. The focusing of a relativistic charged particle beam in a wiggler is analyzed, and the effect of the superconducting wiggler upon the betatron tunes in the SIBERIA-2 storage ring is computed.

Smolyakov, N. V.

1991-10-01

336

Influence of sintering temperature on magnetic properties of samarium-cobalt magnets  

Microsoft Academic Search

Sintering of Sm-Co magnets was first reported on in 1969. Because of success in sintering, Sm-Co magnets are now enjoying added importance. Many processing parameters are critical in the preparation of high quality permanent magnets of Sm-Co. One of these is the sintering temperature. Varying the sintering temperature over a narrow range can produce great variations in properties. One particular

D. Das

1971-01-01

337

Thermodynamic and magnetic properties in two artificial frustrated lattices  

NASA Astrophysics Data System (ADS)

With the Monte Carlo simulation, we investigate the thermodynamics and magnetic properties of the artificial frustrated square and honeycomb lattices. The results from the Ising-like dipolar model show that there occurs one magnetic order transition for the square lattice while the honeycomb lattice exhibits two magnetic order phase transitions. When the magnetic field is applied perpendicular to one of sublattices, a sharp field-independent peak in the specific heat curves appears at a very low temperature for both frustrated lattices due to the occurrence of a long-range ordered state induced by the magnetic field. For the square lattice, the coercive field slightly increases with the angle of field relative to the vertical axis. For both frustrated lattices, the magnetic reversal is achieved mostly via flipping a chain of the nearest neighbor spins.

Li, Y.; Wang, T. X.; Liu, G. D.

2013-10-01

338

Tables of crystallographic properties of magnetic space groups.  

PubMed

Tables of crystallographic properties of the reduced magnetic superfamilies of space groups, i.e. the 7 one-dimensional, 80 two-dimensional and 1651 three-dimensional group types, commonly referred to as magnetic space groups, are presented. The content and format are similar to that of non-magnetic space groups and subperiodic groups given in International Tables for Crystallography. Additional content for each representative group of each magnetic space-group type includes a diagram of general positions with corresponding general magnetic moments, Seitz notation used as a second notation for symmetry operations, and general and special positions listed with the components of the corresponding magnetic moments allowed by symmetry. PMID:18421131

Litvin, D B

2008-04-18

339

Magnetic properties of bacterial magnetosomes and chemosynthesized magnetite nanoparticles  

NASA Astrophysics Data System (ADS)

In this work, the magnetic properties of biologically produced magnetite (magnetosomes) by a mineralization process of magnetotactic bacteria {Magnetospirillum sp.} AMB-1 were compared to those of chemically synthesized magnetite nanoparticles and nanorods. X-ray diffraction data reveal that for all samples the peaks come from magnetite. A sharp magnetic transition (Verwey transition) is clearly observed in magnetosomes at 105 K (magnetite nanocrystals obtained by mineralization) and nanorodes at 112 K, in opposite, this transition is significantly smeared in Fe_{3}O_{4} powder, where the magnetic nanoparticles are separated and the magnetic fluctuations are strong to overcome magnetic anisotropy and randomize magnetic moment. The existence of coercivity of 71 Oe at room temperature is related to the fact that the mean diameter (34 nm) is larger than the critical size for the transition from superparamagnetic to ferromagnetic behaviour. Figs 6, Refs 14.

Timko, M.; Dzarova, A.; Zavisova, V.; Koneracka, M.; Sprincova, A.; Kopcansky, P.; Kovac, J.; Vavra, I.; Szlaferek, A.

2008-06-01

340

Effects of sintering temperature and composition variations on the magnetic properties of samarium cobalt magnets  

Microsoft Academic Search

A systemic study has been made of the effects of various sintering temperatures and variations in composition on the magnetic properties of samarium cobalt magnets. Residual induction, coercive force, and energy product were measured. Samarium content was varied between 35.0% to 36.5% at temperatures 1116, 1126, and 1136 degrees Celcius. A study was also made of the effect of the

L. Wolverton; L. R. Falce

2008-01-01

341

Study of some magnetic properties of ferrofluids filtered in magnetic field gradient  

Microsoft Academic Search

The magnetic properties of some ferrofluids obtained by a new technique, in which the stabilization of particles was done by hydrofobization in the absence of the dispersion medium, and the filtration was done in the presence of a magnetic field gradient, are studied. Measurements were performed on three samples originated from the same ferrofluid with magnetite particles dispersed in kerosene.

I. Malaescu; L. Gabor; F. Claici; N. Stefu

2000-01-01

342

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

Microsoft Academic Search

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

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

1997-01-01

343

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

Microsoft Academic Search

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

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

1997-01-01

344

Magnetic properties of multisegmented cylindrical nanoparticles with alternating magnetic wire and tube segments  

NASA Astrophysics Data System (ADS)

The magnetic properties in multisegmented cylindrical nanostructures comprised of nanowire and nanotube segments are investigated numerically as a function of their geometry. In this work we report systematic changes in the coercivity and remanence in these systems. Besides, we have found the ideal conditions for a magnetic configuration with two antiparallel domains that could be used to help to stabilize magnetic nanoparticles inside ferromagnetic multisegmented cylindrical nanoparticles. This magnetic behavior is due to the fact that the tube segment reverses its magnetization before the wire segment, allowing the control of the magnetic domain walls motion between two segments. In this way, these magnetic nanoobjects can be an alternative to store information or even perform logic functions.

Salazar-Aravena, D.; Corona, R. M.; Goerlitz, D.; Nielsch, K.; Escrig, J.

2013-11-01

345

Modeling the properties of ferrogels in uniform magnetic fields.  

PubMed

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 the magnetic grains is influenced by the application of a magnetic field during gel formation, leading to a pronounced anisotropy in the mechanical response of the ferrogel to an applied magnetic field. In particular, the elastic moduli can be enhanced to different degrees depending on the mutual orientation of the fields during and after ferrogel formation. The model represents ferrogels by ensembles of dipolar spheres dispersed in elastic matrices. Experimental trends are shown to be reflected accurately in the simulations of the microscopic model. In addition, the simulations yield microscopic insights on the organization of the magnetic grains. Finally, simple relationships between the elastic moduli and the magnetization are proposed. If supplemented by the magnetization curve, these relationships yield the dependencies of the elastic moduli on the applied magnetic field, which are often measured directly in experiments. PMID:21405693

Wood, Dean S; Camp, Philip J

2011-01-07

346

Modeling the properties of ferrogels in uniform magnetic fields  

NASA Astrophysics Data System (ADS)

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 the magnetic grains is influenced by the application of a magnetic field during gel formation, leading to a pronounced anisotropy in the mechanical response of the ferrogel to an applied magnetic field. In particular, the elastic moduli can be enhanced to different degrees depending on the mutual orientation of the fields during and after ferrogel formation. The model represents ferrogels by ensembles of dipolar spheres dispersed in elastic matrices. Experimental trends are shown to be reflected accurately in the simulations of the microscopic model. In addition, the simulations yield microscopic insights on the organization of the magnetic grains. Finally, simple relationships between the elastic moduli and the magnetization are proposed. If supplemented by the magnetization curve, these relationships yield the dependencies of the elastic moduli on the applied magnetic field, which are often measured directly in experiments.

Wood, Dean S.; Camp, Philip J.

2011-01-01

347

Free-space measurement of complex permittivity and complex permeability of magnetic materials at microwave frequencies  

Microsoft Academic Search

A free-space measurement system operating in the 8.2-40-GHz frequency range is used to measure the reflection and transmission coefficients, S11 and S21, of planar samples. The complex electric permittivity and the magnetic permeability are calculated from the measured values of S11 and S21. The measurement system consists of transmit and receive horn lens antennas, a network analyzer, mode transitions, and

D. K. Ghodgaonkar; V. V. Varadan; V. K. Varadan

1990-01-01

348

Complex conductivity of UTX compounds in high magnetic fields  

SciTech Connect

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

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

2009-01-01

349

Complex conductivity of UTX compounds in high magnetic fields  

SciTech Connect

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

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

2008-01-01

350

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

SciTech Connect

Several permanent magnet alloys based on the ternary Nd{sub 2}Fe{sub 14}B (2-14-1) composition have been prepared by inert gas atomization (IGA). The microstructure and magnetic properties of these alloys have been studied as a function of particle size, both before and after heat treatment. Different particle sizes have characteristic properties due to the differences in cooling rate experienced during solidification from the melt. These properties are also strongly dependent on the alloy composition due to the cooling rate{close_quote}s effect on the development of the phase structure; the use of rare earth rich compositions appears necessary to compensate for a generally inadequate cooling rate. After atomization, a brief heat treatment is necessary for the development of the optimal microstructure and magnetic properties, as seen from the hysteresis loop shape and improvements in key magnetic parameters (intrinsic coercivity H{sub ci}, remanence B{sub r}, and maximum energy product BH{sub max}). By adjusting alloy compositions specifically for this process, magnetically isotropic powders with good magnetic properties can be obtained and opportunities for the achievement of better properties appear to be possible. {copyright} {ital 1997 American Institute of Physics.}

Sellers, C.H.; Hyde, T.A.; Branagan, D.J. [Idaho National Engineering Laboratory, Idaho Falls, Idaho 83402-2211 (United States); Lewis, L.H. [Department of Applied Science, Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States); Panchanathan, V. [Magnequench International, Anderson, Indiana 46013 (United States)

1997-02-01

351

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

352

Experimental Shocks on Rock Samples and Their Effects on Magnetic Properties and Remanent Magnetization  

NASA Astrophysics Data System (ADS)

Hypervelocity impacts play a key role in the magnetic records of many extraterrestrial bodies (asteroids, Mars, the Moon...). The understanding of magnetization changes induced by hypervelocity impacts is crucial for the interpretation of planetary magnetic anomalies and of the paleomagnetic signal of meteorites. Shocks may also permanently modify the intrinsic magnetic properties of rocks. In this work, we investigate the effects of shocks on both the intrinsic (hysteresis, susceptibility, magnetic anisotropy) and extrinsic (remanent magnetization) magnetic properties of magmatic and metamorphic terrestrial rocks, meteorites (ordinary chondrites and Martian meteorites) and synthetic samples. In order to span a large spectrum of shock duration bracketing the natural case (10-3 to 1 s), we use different experimental techniques: pulsed laser (~10-9-10-8s, up to 50 GPa), high-order explosives (~10-6s, up to 25 GPa) and measurement under pressure in a non-magnetic pressure cell (~102-103 s, up to 1.5 GPa). In order to calibrate experimentally the pressure profile in the impacted materials, we applied shocks induced by laser on rock slices of different thickness (0.5-4mm) to evaluate material response under strong and short pressure loading. Rear free surface velocity has been measured with VISAR (Velocimeter Interferometry for Any Reflector) technique. Velocity profiles are reproduced by simulation using hydrodynamic code including elasto-plastic behaviour of material. The agreement between calculations and experiment is rather good allowing an estimation of the pressure seen by the impacted rocks. The shock experiments demonstrate that above ~10 GPa, the intrinsic properties of all investigated magnetic minerals (magnetite, titanomagnetite, pyrrhotite) are permanently modified: coercivity increases, susceptibility decreases and in some cases a magnetic foliation is created perpendicular to the direction of shock. Therefore, the magnetic properties of shocked meteorites (e.g. Martian meteorites) may not be representative of the magnetism of their parent body. The effects on remanent magnetization are already noticeable at ~1 GPa. The efficiency of the shock remagnetization is strongly dependent on the magnetic mineralogy. For pressure of a few GPa, most magnetic minerals present in meteorites (taenite, kamacite, titanomagnetite, magnetite, pyrrhotite) are already largely demagnetized and/or remagnetized. Therefore, in the vast majority of cases, the paleomagnetic signal of meteorites cannot be original. Records of the possible original magnetic fields may only be looked for in very weakly shocked meteorites. Nevertheless the paleomagnetic signal of shocked meteorites can provide clues on the magnetic fields present during the impacts.

Gattacceca, J.; Bezaeva, N.; Berthe, L.; Boustie, M.; Rochette, P.; Lamali, A.

2006-12-01

353

Characterisation and properties of the inclusion complex of 24-epibrassinolide with ?-cyclodextrin  

Microsoft Academic Search

This paper reports the first study of an inclusion complex of abrassinosteroid with ß-cyclodextrin. The formation of inclusion complexesbetween 24-epibrassinolide and ß-cyclodextrin was confirmed by theirphysicochemical properties and the compounds were analysed by differentialscanning calorimetry, powder X-ray diffraction, nuclear magnetic resonancespectrometry and scanning electron microscopy. Theoretical calculations usingthe MM+ HyperChem force field showed a preference for inclusion of thesidechain of

M. B. M. De Azevedo; M. A. T. Zullo; J. B. Alderete; M. M. M. De Azevedo; T. J. G. Salva; N. Durán

2002-01-01

354

Structure and magnetic properties of nanocrystalline PrCo3  

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

355

/sup 13/C nuclear magnetic resonance study of the complexation of calcium by taurine  

SciTech Connect

/sup 13/C Nuclear magnetic resonance chemical shifts, /sup 1/J/sub c-c/ scalar coupling constants, spin-lattice relaxation times, and nuclear Overhauser effects were determined for taurine-(1, 2 /sup 13/C) and a taurine-(1 /sup 13/C) and taurine-(2 /sup 13/C) mixture in the presence and absence of calcium. Comparison of taurine titration shifts to values for related compounds reveals some unusual electronic properties of the taurine molecule. Stability constants of 1:1 calcium complexes with taurine zwitterions and anions, as well as their /sup 13/C chemical shifts, were obtained by least squares analysis of titration curves measured in the presence of calcium. The stability constants of calcium-taurine complexes were significantly lower than previous values and led to estimates that only approximately one percent of intracellular calcium of mammalian myocardial cells would exist in a taurine complex.

Irving, C.S.; Hammer, B.E.; Danyluk, S.S.; Klein, P.D.

1980-01-01

356

Cisplatin carbonato complexes. Implications for uptake, antitumor properties, and toxicity.  

PubMed

The reaction of aquated cisplatin with carbonate which is present in culture media and blood is described. The first formed complex is a monochloro monocarbonato species, which upon continued exposure to carbonate slowly forms a biscarbonato complex. The formation of carbonato species under conditions that simulate therapy may have important implications for uptake, antitumor properties, and toxicity of cisplatin. PMID:16159248

Centerwall, Corey R; Goodisman, Jerry; Kerwood, Deborah J; Dabrowiak, James C

2005-09-21

357

Complex studies of properties of nanostructured silicon  

NASA Astrophysics Data System (ADS)

Nanocrystalline silicon layers ( 3-35nm ) 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.

2006-09-01

358

Improvement of the magnetic properties of low-neodymium magnets by minor addition of titanium  

Microsoft Academic Search

Rapidly solidified nanocomposite Nd9Fe77?xB14Tix alloys, consisting of magnetic Nd2Fe14B phase and soft magnetic phases, were investigated. The effect of titanium addition on the structure and magnetic properties was studied. It was found that 2–4at% Ti addition leads to substantial increase of the coercivity and maximum energy product, maintaining the remanence unchanged. The highest properties: Jr=0.81T, JHc=907kA\\/m, (BH)max=99kJ\\/m3, were achieved for

Marzena Spyra; Marcin Leonowicz

2008-01-01

359

Analysis of the vector magnetic fields of complex sunspots  

NASA Astrophysics Data System (ADS)

An analysis of the vector magnetic field in the delta-configurations of two complex sunspot groups is presented, noting several characteristics identified in the delta-configurations. The observations of regions 2469 (S12E80) and 2470 (S21E83) took place in May, 1980 with a vector magnetograph, verified by optical viewing. Longitudinal magnetic field plots located the delta-configurations in relation to the transverse field neutral line. It is shown that data on the polarization yields qualitative information on the magnetic field strengths, while the azimuth of the transverse field can be obtained from the relative intensities of linear polarization measurements aligned with respect to the magnetograph analyses axis at 0 and 90 deg, and at the plus and minus 45 deg positions. Details of the longitudinal fields are discussed. A strong, sheared transverse field component is found to be a signature of strong delta. A weak delta is accompanied by a weak longitudinal gradient with an unsheared transverse component of variable strength.

Patty, S. R.

360

Matrix and interaction effects on the magnetic properties of Co nanoparticles embedded in gold and vanadium.  

PubMed

The study of the magnetic properties of Co nanoparticles (with an average diameter of 10.3 nm) grown using a gas-phase aggregation source and embedded in Au and V matrices is presented. We investigate how the matrix, the number of embedded nanoparticles (counted by coverage percentage), the interparticle interactions and the complex nanoparticles/matrix interface structure define the magnetic properties of the studied systems. A threshold coverage of 3.5% of a monolayer was found in both studied systems: below this coverage, nanoparticles behave as an assembly of independent single-domain magnetic entities with uniaxial anisotropy. Above the threshold it is found that the magnetic behavior of the systems is more matrix dependent. While magnetic relaxation and Henkel plots measurements stress the importance of the dipolar interactions and the formation of coherent clusters in the case of the Au matrix, the magnetic behavior of cobalt clusters embedded in the vanadium matrix is explained through the formation of a spin glass-like state at the V-Co interface that screens the magnetic interactions between NPs. PMID:23165521

Ruano, M; Díaz, M; Martínez, L; Navarro, E; Román, E; García-Hernandez, M; Espinosa, A; Ballesteros, C; Fermento, R; Huttel, Y

2012-11-20

361

Laser-Induced Magnetic Nanostructures with Tunable Topological Properties  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

362

Laser-induced magnetic nanostructures with tunable topological properties.  

PubMed

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

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

2013-04-22

363

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

364

Effect of Mo addition on magnetic properties of Fe–28Cr–15Co hard magnets  

Microsoft Academic Search

The present work describes the developments of hard magnets by thermo-magnetic treatment. The magnetic properties of Fe–28Cr–15Co–(1–5)Mo (wt%) alloys after different heat treatment conditions are studied and compared with ternary Fe–28Cr–15Co alloys. Fe–28Cr–15Co–3.5Mo have produced a coercive force of 840Oe (66.83kA\\/m), remanence of 11kG (1.1T) and energy product of 5.4MGOe (43kJ\\/m3) that are comparable to Alnico 6 magnets. It was

Z Ahmad; A ul Haq; S. W Husain; T Abbas

2002-01-01

365

Effect of Mo addition on magnetic properties of Fe28Cr15Co hard magnets  

Microsoft Academic Search

The present work describes the developments of hard magnets by thermo-magnetic treatment. The magnetic properties of Fe-28Cr-15Co-(1-5)Mo (wt%) alloys after different heat treatment conditions are studied and compared with ternary Fe-28Cr-15Co alloys. Fe-28Cr-15Co-3.5Mo have produced a coercive force of 840Oe (66.83kA\\/m), remanence of 11kG (1.1T) and energy product of 5.4MGOe (43kJ\\/m3) that are comparable to Alnico 6 magnets. It was

Z. Ahmad; A. Ul Haq; S. W. Husain; T. Abbas

2002-01-01

366

Synthesis, spectral, bioactivity, and NLO properties of chalcone metal complexes  

Microsoft Academic Search

A series of metal(II) complexes ML and ML2 [where M?=?Cu(II), Co(II), Ni(II), Zn(II), Mn(II), Cd(II), and VO(II); L?=?2-hydroxyphenyl-3-(1H-indol-3-yl)-prop-2-en-1-one (HPIP)] have been prepared and characterized by elemental analysis, magnetic susceptibility, molar conductance, IR, UV-Vis, NMR, Mass, and ESR spectral studies. Conductivity measurements reveal that the complexes are non-electrolytes, except VO(II) complex. Spectroscopy and other data show square pyramidal geometry for oxovanadium

S. Sumathi; P. Tharmaraj; C. D. Sheela; R. Ebenezer

2011-01-01

367

Magnetic properties of novel epitaxial films  

SciTech Connect

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

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

1986-09-01

368

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

PubMed

In the present study, a new ligand is prepared by condensation of hydralazine (1-Hydralazinophthalazine) with 2-butanon-3-oxime. The acid-base equilibria of the schiff-base and the complex formation equilibria with the metal ions as Cu(II), Ni(II), Co(II), Cd(II), Mn(II) and Zn(II) are investigated potentiometrically. The stability constants of the complexes are determined and the concentration distribution diagrams of the complexes are evaluated. The effect of metal ion properties as atomic number, ionic radius, electronegativity and ionization potential are investigated. The isolated solid complexes are characterized by conventional chemical and physical methods. The potential coordination sites are assigned using the i.r. and (1)H NMR spectra. The structures of the isolated solid complexes are proposed on the basis of the spectral and magnetic studies. PMID:17950027

Shoukry, Azza A; Shoukry, Mohamed M

2007-09-07

369

Effect of Mo addition on magnetic properties of Fe-28Cr-15Co hard magnets  

NASA Astrophysics Data System (ADS)

The present work describes the developments of hard magnets by thermo-magnetic treatment. The magnetic properties of Fe-28Cr-15Co-(1-5)Mo (wt%) alloys after different heat treatment conditions are studied and compared with ternary Fe-28Cr-15Co alloys. Fe-28Cr-15Co-3.5Mo have produced a coercive force of 840Oe (66.83kA/m), remanence of 11kG (1.1T) and energy product of 5.4MGOe (43kJ/m3) that are comparable to Alnico 6 magnets. It was found that addition of Mo up to 3.5wt% to the ternary alloys causes to extend the ?-phase microstructure at annealed state and stimulates the spinodal decomposition of Fe, Co-rich ?1-particles in a preferred direction <100> that leads to increase the magnetic properties of the alloys.

Ahmad, Z.; Ul Haq, A.; Husain, S. W.; Abbas, T.

2002-08-01

370

Low-dimensional copper(II) complexes with the trinucleating ligand 2,4,6-tris(di-2-pyridylamine)-1,3,5-triazine: synthesis, crystal structures, and magnetic properties.  

PubMed

The preparation and structural characterization of three new copper(II) complexes of formula [Cu(3)(dipyatriz)(2)(H(2)O)(3)](ClO(4))(6) x 2 H(2)O (1), {[Cu(4)(dipyatriz)(2)(H(2)O)(2)(NO(3))(2)(ox)(2)](NO(3))(2) x 2 H(2)O}(n) (2), and [Cu(6)(dipyatriz)(2)(H(2)O)(9)(NO(3))(3)(ox)(3)](NO(3))(3) x 4 H(2)O (3) [dipyatriz = 2,4,6-tris(di-2-pyridylamine)-1,3,5-triazine and ox = oxalate] are reported. The structure of 1 consists of trinuclear units [Cu(3)(dipyatriz)(2)(H(2)O)(3)](6+) and uncoordinated perchlorate anions. The two dipyatriz molecules in 1 act as tris-bidentate ligands with the triazine cores being in a quasi eclipsed conformation. Each copper atom in 1 exhibits a distorted square pyramidal geometry CuN(4)O with four pyridyl-nitrogen atoms from two dipyatriz ligands building the basal plane and a water molecule occupying the axial position. The values of the intratrimer copper-copper separation are 8.0755(6) and 8.3598(8) A. Compound 2 exhibits a layered structure of copper(II) ions which are connected through bis-bidentate dipyatriz ligands and bidentate/outer monodentate oxalato groups. The copper atoms in 2 exhibit six- [Cu(1)N(4)O(2)] and five-coordination [Cu(2)N(2)O(3)]. A water molecule and three pyridyl-nitrogen atoms [Cu(1)] and two pyridyl-nitrogen plus two oxalate-oxygen atoms [Cu(2)] define the equatorial plane whereas either an oxalate-oxygen and a pyridyl-nitrogen [Cu(1)] or a nitrate-oxygen [Cu(2)] fill the axial positions. The copper-copper separation through the bridging oxalato is 5.6091(6) A whereas those across dipyatriz vary in the range 7.801(1)-9.079(1) A. The structure of compound 3 contains discrete cage-like hexacopper(II) units [Cu(6)(dipyatriz)(2)(H(2)O)(9)(NO(3))(3)(ox)(3)](3+) where two trinuclear [Cu(3)(dipyatriz)](6+) fragments are connected by three bis-bidentate oxalate ligands, the charge being balanced by three non-coordinated nitrate anions. The values of the intracage copper-copper distance are 5.112(3)-5.149(2) A (across oxalato) and 7.476(2)-8.098(2) A (through dipyatriz). Magnetic susceptibility measurements of polycrystalline samples of 1-3 in the temperature range 1.9-295 K show the occurrence of a weak antiferromagnetic interaction across dipyatriz in 1 [J = -0.08(1) cm(-1), the Hamiltonian being defined as (wedge)H = -J ((wedge)S(1).(wedge)S(2) + (wedge)S(1) x (wedge)S(3) + (wedge)S(2) x (wedge)S(3))] and weak ferro- (2) and strong antiferromagnetic (3) interactions through the oxalato bridge in 2 [J = +0.45(2) cm(-1)] and 3 [J = -390(1) cm(-1)]. The use of the dipyatriz-containing copper(II) species as a building block to design homo- and heterometallic magnetic compounds is analyzed and discussed. PMID:20507110

Yuste, Consuelo; Cañadillas-Delgado, Laura; Labrador, Ana; Delgado, Fernando S; Ruiz-Pérez, Catalina; Lloret, Francesc; Julve, Miguel

2009-07-20

371

Magnetic properties of rare-earth metallofullerenes  

Microsoft Academic Search

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

Hideyuki Funasaka; Kenji Sugiyama; Kazunori Yamamoto; Takeshi Takahashi

1995-01-01

372

Magnetic properties of monodisperse iron oxide nanoparticles  

Microsoft Academic Search

We have synthesized a set of monodisperse iron oxide nanoparticles ranging from 7.8 to 17.9 nm by thermal decomposition methods. Based on the evidence of high-resolution transmission electron microscopy, the iron oxide nanoparticles appear as spherical dots with size standard deviations of less than 5%. Blocking temperatures of the set of nanoparticles were measured by the zero-field-cooled magnetization measurements. The

Chun-Rong Lin; Ray-Kuang Chiang; Jiun-Shen Wang; Ti-Wen Sung

2006-01-01

373

Morphological structures and magnetic properties of sputtered thin film media  

Microsoft Academic Search

Morphological structures and magnetic properties of sputtered Co-Ni-Zr\\/Cr films are investigated in order to clarify the origin of an undesirable magnetic anisotropy induced by inline sputter deposition during disk transfer. The film deposition onto nontextured substrates at lower Ar pressure makes this anisotropy larger. Co-Ni-Zr\\/Cr films deposited at 1.3 Pa are observed to have bow-like columnar structures of Cr films

K. Furusawa; H. Kataoka; T. Takagaki; K. Abe; Y. Shiroishi; S. Funamoto; S. Kojima; M. Hayashi

1990-01-01

374

Synthesis and magnetic properties of iron oxide silica aerogel nanocomposites  

NASA Astrophysics Data System (ADS)

Iron oxide silica nanocomposite aerogels were produced by sol gel procedure followed by the hypercritical evaporation of the solvent. Aerogels hosting maghemite were synthesized from the precursors TEOS and TMOS. Mean oxide particle size seems to be strongly influenced by the solvent. The magnetic properties of the iron oxide particles hosted in silica aerogeles pores were studied by means of magnetometry and AC susceptometry. Interrelation between synthesis parameters, structure and magnetic behavior is discussed.

Fernández van Raap, M. B.; Sanchez, F. H.; Leyva, A. G.; Japas, M. L.; Cabanillas, E.; Troiani, H.

2007-09-01

375

Soft magnetic properties of Co\\/Ti multilayers  

Microsoft Academic Search

We report on the structural and magnetic properties of Co\\/Ti multilayers in which the soft magnetic state is related to a structural transformation within the crystalline Co sublayers. For all samples with dTi > 1.5 nm, a sudden drop in the coercivity from Hc ? 1.4 to ? 0.2 kA\\/m was observed at critical thickness dcritCo ? 3 nm. Results

K. Chrzumnicka; J. Dubowik; R. Gontarz; I. Go?cia?ska; H. Ratajczak; L. Smardz; F. Stobiecki; B. Szymanski

1996-01-01

376

Magnetic properties of the three-band Hubbard model  

Microsoft Academic Search

:   We present magnetic properties of the three-band Hubbard model in the para- and antiferromagnetic phase on a hypercubic lattice\\u000a calculated with the Dynamical Mean-Field Theory (DMFT). To allow for solutions with broken spin-symmetry we extended the approach\\u000a to lattices with AB-like structure. Above a critical sublattice magnetization one can observe rich structures in the spectral-functions similar to the t-J

T. Maier; M. B. Zölfl; T. Pruschke; J. Keller

1999-01-01

377

Magnetic properties of Pb1 - xMnxTe  

Microsoft Academic Search

Magnetic and transport properties of Pb1?xMnxTe have been investigated for Mn concentrations x<0.2. A spin glass behavior is observed below a freezing temperature characterized by a cusp in the reversible part of the magnetic susceptibility. Irreversible effects below Tg have been studied in detail. Although the materials are p type with hole concentrations ranging from 6×1016 to 6×1019 cm?3, the

J. Tholence; A. Mauger; M. Escorne; R. Triboulet

1984-01-01

378

Synthesis and magnetic properties of iron-iron oxide nanoparticles  

Microsoft Academic Search

Monodisperse magnetic nanoparticles are of much interest for data storage and biomedical applications as well as for studies of the fundamental characteristics of magnetism on small length scales. In light of this attention, we have been investigating the properties of iron-iron oxide nanoparticles, prepared by modifying a recently developed solvent-based synthesis method that produces particles of well-defined size [1]. By

Anna Clausen; Yumi Ijiri

2004-01-01

379

Silica aerogel–iron oxide nanocomposites: structural and magnetic properties  

Microsoft Academic Search

Magnetic nanocomposites formed by iron oxide particles hosted in silica aerogels pores have been synthesized by sol–gel processes and supercritical evacuation of the solvent. Two iron-containing salts have been essayed: (A) Fe(NO3)·9H2O and (B) FeNa(EDTA)·2H2O. The synthetic routes made use of the gel pores as nanoreactors. Structural and magnetic properties have been studied by combining X-ray diffraction (XRD), N2 adsorption

L. Casas; A Roig; E Rodr??guez; E Molins; J Tejada; J Sort

2001-01-01

380

Magnetic properties of strained single-walled carbon nanotubes  

Microsoft Academic Search

Strong effects of uniaxial and torsional strains on the magnetic properties of single-walled carbon nanotubes have been investigated by tight binding calculations and the Green function analyses. The strain-induced peaks of susceptibility are found in the carbon nanotubes, and paramagnetic-diamagnetic transition takes place at certain strains. The critical magnetic flux for semiconductor-metal transition changes linearly with strains depending on the

Zhuhua Zhang; Wanlin Guo

2007-01-01

381

Magnetic Properties on Ferromagnetic FeAlO  

Microsoft Academic Search

FeAlO3 polycrystalline sample was fabricated by the sol-gel method. The crystallographic and magnetic properties of the sample were measured using X-ray diffractometer, Mossbauer spectroscopy, and vibrating sample magnetometer (VSM). The crystal structure was found to be an orthorhombic with the space group Pna21, which has four cation sites labeled Fe1, Fe2, Al2(octahedral sites), and Al1(tetrahedral site). Magnetic hysteresis curves of

Jee Hoon We; Sam Jin Kim; Chul Sung Kim

2006-01-01

382

Texture and magnetic properties of exchange bias systems  

Microsoft Academic Search

We report on the magnetic and structural properties of IrMn\\/CoFe exchange bias systems deposited onto a dual seed layer of NiCr(X)\\/Ru(5 nm), with X=2, 6, and 20 nm. Samples with the structure NiCr (Xnm)\\/IrMn (7 nm)\\/CoFe (3 nm)\\/Ta (10 nm) with X=2, 6, and 20 nm were prepared by dc sputtering for magnetic characterization. A second set of samples with

N. P. Aley; M. Bowes; R. Kroeger; K. O'Grady

2010-01-01

383

Magnetic properties of (Co, Ni, Mn) 3O4 spinels  

Microsoft Academic Search

Magnetic properties of new materials, based on the general formula CoxNiyMnzO4 (x+y+z= 3), have been investigated as a function of magnetic field and temperature. The behavior observed in the paramagnetic regime (220 K ? T ? 400 K) shows a direct correlation with the nominal cation concentration. The paramagnetic-ferrimagnetic transition which takes place at T = Tc depends on the

YANWEI MA; P. DuráN; Inorganique Moléculaire

384

Martian magnetic anomalies in light of fundamental properties of magnetic material  

NASA Astrophysics Data System (ADS)

The intense remanent magnetization of the Mars crust must be due to one or more of a very few candidate minerals. The most efficient magnetic minerals capable of producing stable magnetization on Mars are dispersed magnetite and pyrrhotite grains of less than 100 nm in diameter and dispersed (exsolved) hematite regardless of grain size. Larger magnetite and pyrrhotite grains (greater than 1000 nm) have large intrinsic demagnetizing fields causing low values of acquired remanence. Hematite has 2 orders of magnitude lower demagnetizing field, allowing preservation of SD -like behavior for grain diameters reaching 0.2 mm. The larger amplitude of magnetic anomalies on Mars relates either to larger volume or large magnetic density of the rocks that were magnetized in a uniform direction. The nature of the magnetic source could include intrusive and/or metamorphic rocks with predominantly coarse-grained granular texture. We analyzed hematite ilmenite series of exsolved minerals commonly found in deep crustal rocks on Earth. Finely exsolved titanohematite within ferrian ilmenite host and titanohematite with fine ferrian ilmenite exsolution both have sufficiently strong magnetization to explain magnetic anomalies on Mars. We also analyzed the mineral acquisition properties for magnetite and hematite, and found grain size regions that may allow amplification of the preexisting magnetization without the presence of the ambient magnetic field. This amplification depends on the nature of the thermal gradient across the Curie isotherm.

Kletetschka, G.; Ness, N. F.; Connerney, J. E. P.; Acuna, M. H.; Wasilewski, J. P.

2003-04-01

385

Flow properties and heap shape of magnetic powders  

NASA Astrophysics Data System (ADS)

The flow properties of powders are mainly related to the interplay of cohesive forces and intergrain frictional forces. Indeed, the formation of large aggregates and the presence of arches modify the dynamic and the static properties of a powder. We have experimentally investigated a ``smart powder'' for which the interparticle interaction can be tuned by an external magnetic field. Through our experimental results, we show that the rheological and the static properties of such a system can be controlled, (i) Different dynamical flowing regimes have been observed through the output of funnel like a ``dry liquid state'' forming conic droplets as well as a ``layered soft state.'' (ii) The morphology of a cohesive heap have been also analyzed. The increase of the heap height h with the applied magnetic field strength has been measured for different orientations of the field. Moreover, a strong anisotropy of the heap shape is observed when the magnetic field is oriented perpendicularly to the gravity.

Vandewalle, N.; Lumay, G.

2009-06-01

386

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

387

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

PubMed

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

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

2013-04-27

388

Magnetic property mapping system for analyzing three-dimensional magnetic components  

NASA Astrophysics Data System (ADS)

A magnetic measurement system utilizing a vector magnetic sensor for analyzing and mapping low frequency magnetic properties of metals has been developed for nondestructive evaluation. The measurement system consists mainly of an induction coil which can expose a large sample area, a vector magnetic sensor for detecting magnetic fields emanating from a sample, a lock-in amplifier, and a two-dimensional scanning stage. The system was determined to have a high magnetic sensitivity corresponding to less than 1 nT in the locked-in state. The magnetic field strength change was detected in a sample that contained a slit of width greater than 1 mm. Time sequential vector component (normal and tangential) maps were developed. An iron plate as an example of a ferromagnetic metal and an aluminum plate as an example of a good conducting and nonferromagnetic material were compared using this system. Analyzing the vector component maps could differentiate differences in the magnetic properties, such as permeability, eddy current distribution, and residual magnetism.

Tsukada, Keiji; Kiwa, Toshihiko

2006-06-01

389

Structural and magnetic properties of bulk MnBi permanent magnets  

NASA Astrophysics Data System (ADS)

Structural and magnetic properties of bulk nanostructural Mn100-xBix (x = 40, 45, 52) permanent magnets prepared by spark plasma sintering technique were studied. The effect of the Mn/Bi ratio on the MnBi low temperature phase (LTP) formation and its magnetic properties were investigated. An increase of the bismuth amount in the magnets leads to better formation of LTP, resulting in the improvement of both magnetization (Ms) and remanence (Mr), but decreasing the coercivity (Hc) of the magnets. At room temperature, Ms increases from 27.87 emu/g for Mn60Bi40 to 45.31 emu/g for Mn48Bi52, whereas Hc decreases from 12 to 7.9 kOe. The microstructure of Mn48Bi52 magnet is composed of fine and uniform grains with an average size of 140 nm as shown in the TEM image. The Mn48Bi52 magnet shows a high Hc of 19 kOe at 423 K, indicating a strong positive temperature coefficient of coercivity for the MnBi magnet.

Zhang, D. T.; Cao, S.; Yue, M.; Liu, W. Q.; Zhang, J. X.; Qiang, Y.

2011-04-01

390

Properties of Sintered Al Substituted NdFeB Magnets  

NASA Astrophysics Data System (ADS)

The effect of partial substitution of Fe by Al (Al, Al2O3) on the magnetic properties and the corrosion resistance of the sintered NdFeB magnet has been investigated. With the increasing amount of Al, the anisotropy field and the saturation magnetization decrease, but the coercivity increases up to 4 at.% Al and further alloying of Al leads to a decrease of the coercivity. Different substances like Al (metallic Al or Al2O3) modify the microstructure to different increase in the coercivity and especially to changes in the remanence. Alloying Al via metallic Al decreases the remanence, whereas via Al2O3) up to 4 at.%0 Al increases it. The Al additions inhibit atmospheric corrosion of the magnet. We have found that Al2O3 in sintered NdFeB magnet substantially improves the coercivity and the corrosion resistance with the improved remanence.

Szymura, S.; Bala, H.; Rabinovich, Yu. M.; Wiechu?a, J.

391

Magnetic properties of the natural pyrope-almandine garnets  

NASA Astrophysics Data System (ADS)

Four natural samples of the pyrope-almandine solid-solution series have been studies by Mössbauer spectroscopy and magnetization measurements have been made to determine their magnetic properties. The samples exhibit a normal para- to antiferromagnetic transition at low temperatures. The paramagnetic susceptibilities of the pyrope-almandine samples follow a Curie-Weiss law at temperatures above 60 K. The Néel temperature (TN), and the paramagnetic Curie temperature (?c) change with chemical composition. Mössbauer spectra of the almandine taken in the magnetically ordered phase can be fitted with two Fe2+ eight-line magnetic hyperfine patterns of equal intensities. The Mössbauer spectra of the other samples of the series at low temperatures are interpreted as due to different magnetic environmental configurations of Fe2+.

de Oliveira, J. C. P.; da Costa, M. I.; Schreiner, W. H.; Vasquez, A.

1989-04-01

392

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

393

Magnetic properties of NdAu 2Ge 2  

Microsoft Academic Search

Physical properties of NdAu2Ge2, crystallising with the tetragonal ThCr2Si2-type crystal structure, were investigated by means of magnetic, calorimetric and electrical transport measurements as well as by neutron diffraction. The compound exhibits antiferromagnetic ordering below TN=4.5K with a collinear magnetic structure of the AFI-type. The neodymium magnetic moments are parallel to the c-axis and amount to 1.04(4)?B at 1.5K. The observed

A. Szytula; D. Kaczorowski; ?. Gondek; A. Arulraj; S. Baran; B. Penc

2009-01-01

394

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

395

The magnetic properties of disordered Fe-Al alloy system  

NASA Astrophysics Data System (ADS)

Using the effective field theory with a probability distribution technique that accounts for the self-spin correlation functions, the magnetic properties of disordered Fe-Al alloys on the basis of a site-diluted quantum Heisenberg spin model are examined. We calculated the critical temperature and the hysteresis loops for this system. We find a number of characteristic phenomena. In particular, the effect of concentration c of magnetic atoms and the reduced exchange anisotropic parameter ? on both the critical temperature and magnetization profiles are clarified.

Oubelkacem, A.; Essaoudi, I.; Ainane, A.; Dujardin, F.; Ricardo de Sousa, J.; Saber, M.

2010-09-01

396

Magnetic and structural properties of amorphous transition metals and alloys  

Microsoft Academic Search

In this paper a neutron scattering study of local order and magnetic\\u000a properties of the Fe1-xCox amorphous system is presented. A wide\\u000a momentum transfer range has been used for studying local order. The\\u000a better resolution associated with higher neutron wavelengths provided\\u000a one with a description of the magnetic contribution measured with and\\u000a without an applied magnetic field. Preliminary results are

R. Bellissent; G. Galli; T. Hyeon; P. Migliardo; G. Parette; K.S. Suslick

1996-01-01

397

Magnetic and Transport Properties of doped half-Heusler alloys.  

NASA Astrophysics Data System (ADS)

We present results of a study of small-gap semiconductors which crystallize in the MgAgAs half-Heusler structure. In particular TiNiSn and ScNiSb have been studied. We report the results of doping into the metallic state via substitution onto each of the three sublattices. We have also studied the role of magnetic impurities, for example, Ce, in the otherwise non-magnetic host. Magnetic and transport properties of flux-grown single crystals of Ti_1-xCe_xNiSn and Sc_1-xCe_xNiSb which display small-moment ferromagnetism will be reported.

Torelli, M. E.; Sarrao, J. L.; Fisk, Z.

1996-03-01

398

Magnetic properties of electroplated wires coated by ferrofluid  

Microsoft Academic Search

Low-frequency magnetic properties of ferromagnetic composite wires were studied with and without coating by ferrofluid. Non-magnetic CuBe wires of 0.1mm diameter were electroplated with FeCoNi layer of 1?m thickness. Magnetization curves were measured in the frequency range of 10Hz–3kHz. The composite CuBe\\/FeCoNi\\/ferrofluid material shows a hysteretic behaviour in a small field. The hysteresis loop of ferrofluid covered electroplated wire is

H. García-Miquel; G. V. Kurlyandskaya; V. I. Levit

2006-01-01

399

Pressure vessel steel embrittlement monitoring by magnetic properties measurements  

SciTech Connect

The magnetic properties of specimens of one heat of A533B nuclear pressure vessel grade steel have been examined in the as-received condition and after neutron irradiation to various fluence levels up to 4 [times] 10[sup 18] cm[sup [minus]2] (E > 0.1 MeV) in the University of Illinois Advanced TRIGA reactor core at two temperatures, approximately 120 and 260[degrees]C. The effect of some heat treatments was also investigated. The magnetic properties were measured by an automated hysteresis curve tracing method using a miniature transformer which incorporated the specimens in its core. Changes in magnetic hysteresis energy loss were correlated with neutron fluence in the case of certain irradiated specimens, and with microhardness measurements in the case of heat treated specimens. At the higher irradiation temperatures, no significant changes in either the magnetic hysteresis properties or the microhardness were noted for the present fluences. The relationship between the observed magnetic properties response and irradiation-induced embrittlement is discussed.

Stubbins, J.F.; Shong, W-J.; Giacobbe, M.; Ougouag, A.M. (Illinois Univ., Urbana, IL (United States). Dept. of Nuclear Engineering); Williams, J.G. (Arizona Univ., Tucson, AZ (United States). Dept. of Nuclear Engineering)

1992-01-01

400

Pressure vessel steel embrittlement monitoring by magnetic properties measurements  

SciTech Connect

The magnetic properties of specimens of one heat of A533B nuclear pressure vessel grade steel have been examined in the as-received condition and after neutron irradiation to various fluence levels up to 4 {times} 10{sup 18} cm{sup {minus}2} (E > 0.1 MeV) in the University of Illinois Advanced TRIGA reactor core at two temperatures, approximately 120 and 260{degrees}C. The effect of some heat treatments was also investigated. The magnetic properties were measured by an automated hysteresis curve tracing method using a miniature transformer which incorporated the specimens in its core. Changes in magnetic hysteresis energy loss were correlated with neutron fluence in the case of certain irradiated specimens, and with microhardness measurements in the case of heat treated specimens. At the higher irradiation temperatures, no significant changes in either the magnetic hysteresis properties or the microhardness were noted for the present fluences. The relationship between the observed magnetic properties response and irradiation-induced embrittlement is discussed.

Stubbins, J.F.; Shong, W-J.; Giacobbe, M.; Ougouag, A.M. [Illinois Univ., Urbana, IL (United States). Dept. of Nuclear Engineering; Williams, J.G. [Arizona Univ., Tucson, AZ (United States). Dept. of Nuclear Engineering

1992-12-01

401

Detection of fatigue in structural steels by magnetic property measurements  

NASA Astrophysics Data System (ADS)

The magnetic properties of ferromagnetic materials are sensitive to the mechanical and microstructural condition of the material. Fatigue can affect the magnetic properties due to microstructural changes, primarily dislocation production. Magnetic hysteresis measurements have been used to monitor the changes in the parameters due to low cycle fatigue, with the overall objective of developing a new tool to enhance the present NDE techniques for detecting failure. The magnetic measurements were performed using the Magnescope, a portable magnetic inspection system. Materials for fatiguing included plain low carbon steel and samples of quenched and tempered AISI 4340. The coercivity and remanence of the low carbon steel samples increased during the early stages of fatigue, reflecting strain hardening. As cycling progressed, the magnetic parameters leveled off and dropped sharply shortly before failure. The coercivity and remanence of the 4340 samples decreased during the initial stages of cycling, reflecting fatigue softening. The parameters plateaued, then decreased shortly before failure. The amount of change in the magnetic parameters was found to depend on the strain amplitude of the cycling.

Devine, M. K.; Kaminski, D. A.; Sipahi, Lb.; Jiles, D. C.

1992-03-01

402

The Influence of Geometry on the Magnetic Properties of Ybco  

NASA Astrophysics Data System (ADS)

The purpose of the present study was to investigate the influence of geometry on the magnetic properties of the high temperature superconductor YBa_2 Cu_3O_{7 -delta}. In particular, this study was interested in addressing what effects a flat geometry has on the magnetic properties of a superconductor when a magnetic field is applied perpendicular to the flat plane. Much of the past data concerning magnetic hysteresis in these materials has been collected using bulk magnetic measurement techniques. Unfortunately, bulk measurements must be interpreted using models which describe physical behavior apparent only at smaller length scales. To avoid this interpreted step, and to test some traditionally accepted ideas regarding the spatial dependence of current density in these samples, the present study uses a novel approach to observing the local magnetic behavior at the surface of these superconductors. The local magnetic flux density was directly monitored using micro Hall sensors placed at the surface of the sample. It was found that demagnetization effects are extremely important for large aspect ratio samples and that the observed magnetic behavior cannot be described by the standard elliptical approximation. A modified critical state model valid for thin samples was developed which incorporates demagnetization effects for the perpendicular geometry. This model can be used to explain the observed magnetic hysteresis, magnetic relaxation, and the effects transport current has on the critical state. Novel evidence for surface barriers in YBCO thin films is briefly presented. A geometrical barrier to flux penetration is found to exist in a detwinned YBa _2CU_3O _{7-delta} single crystal and also in a YBa_2CU_3 O_{7-delta} polycrystalline system. This barrier cannot exist in samples which have elliptical cross-sections and is the result of the flat geometry.

Darwin, Michael John

1995-01-01

403

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

404

Magnetic properties in polycrystalline and single crystal Ca-doped LaCoO3  

NASA Astrophysics Data System (ADS)

Polycrystalline (PC) and single crystalline (SC) Ca-doped LaCoO3 (LCCO) samples with the perovskite structure were synthesized by conventional solid-state reaction and the floating-zone growth method. We present the results of a comprehensive investigation of the magnetic properties of the LCCO system. Systematic measurements have been conducted on dc magnetization, ac susceptibility, exchange-bias, and the magnetocaloric effect. These findings suggest that complex structural phases, ferromagnetic (FM), and spin-glass/cluster-spin-glass (CSG), and their transitions exist in PC samples, while there is a much simpler magnetic phase in SC samples. It was also of interest to discover that the CSG induced a magnetic field memory effect and an exchange-bias-like effect, and that a large inverse irreversible magnetocaloric effect exists in this system.

Zeng, R.; Debnath, J. C.; Chen, D. P.; Shamba, P.; Wang, J. L.; Kennedy, S. J.; Campbell, S. J.; Silver, T.; Dou, S. X.

2011-04-01

405

Exogenous bridging and nonbridging in copper(II) complexes of a binculeating 2,6-bis((N-methylpiperazino)methyl)-4-chlorophenolate ligand. Crystal structures and magnetic properties of Bis(. mu. -acetato), dinitrito, and bis(azido) complexes. Possible relevance to the type 3 depleted laccase active site  

SciTech Connect

As part of a wide study of the structure/magnetism/redox relations {sup 1{minus}5} in binuclear copper(II) complexes, the authors have employed a binucleating ligand, LH, obtained by a Mannich reaction between a para-substituted phenol, formaldehye, and N-methylpiperazine{sup 6,7}. Molecular models are given which show that simultaneous coordination of the phenol oxygen and the four piperazine nitrogen atoms to two Cu(II) ions, in the presence of absence of an exogenous bridging ligand, would be difficult in view of the sterically constrained ligand conformation.

Bertoncello, K.; Fallon, G.D.; Hodgkin, J.H.; Murray, K.S. (Monash Univ., Clayton (Australia))

1988-12-28

406

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

2010-09-30

407

Properties of magnetic nanoparticles in the Brownian relaxation range for liquid phase immunoassays  

Microsoft Academic Search

Properties of magnetic nanoparticles in the Brownian relaxation region were studied. Using the magnetic nanoparticles that exhibit remanence, we measured the magnetic properties, such as static magnetization, magnetic relaxation, and alternating current susceptibility, in a solution. Comprehensive comparisons were made between the experimental results and the theoretical ones predicted from the Brownian relaxation. From the comparison, the distributions of the

K. Enpuku; T. Tanaka; T. Matsuda; F. Dang; N. Enomoto; J. Hojo; K. Yoshinaga; F. Ludwig; F. Ghaffari; E. Heim; M. Schilling

2007-01-01

408

Microstructure and magnetic properties of sintered Nd-Fe-B magnets with high hydrogen content  

NASA Astrophysics Data System (ADS)

The effects of hydrogen contents after the process of hydrogen decrepitation on the magnetic properties and corrosion resistance of sintered Nd-Fe-B permanent magnets have been studied. The intrinsic coercivity of the magnets increases and the remanence decreases with increasing hydrogen content. High residue hydrogen content in the starting ingot leads to the reaction of hydrogenation, disproportionation, desorption and recombination in the sinter process resulting in magnets with low remanence. The results of highly accelerated temperature/humidity stress test indicate that excessive hydrogen contents are harmful to the corrosion resistance of the magnets. The influences of residue hydrogen contents on the corrosion resistance of magnets dominate only when the residue hydrogen content exceeds 1300 parts per million.

Guo, S.; Zhou, Q. Y.; Chen, R. J.; Lee, D.; Yan, A. R.

2011-04-01

409

[Synthesis and luminescence properties of europium (III) complexes].  

PubMed

Three types of europium complexes were synthesized by introducing benzoylacetone as the first ligand and 1, 10-phenanthroline, triphenylphosphine oxide, 2,2'-bipyridyl as the second ligand, respectively. The properties of above materials were characterized by infrared absorption spectra, UV-Vis absorption spectra and fluorescence spectra. Then, it was discussed that the different second ligands of europium complexes can affect their luminescence properties, and their intramolecular energy transfer models had been set up. The results indicated that ligands and complexes have a strong absorption of UV light and the three types of europium complexes exhibit characteristic luminescence of europium ion when excited by UV light. In addition, it is suggested that the fluorescence yield of europium complexes mostly depend on both the energy difference between the second ligand and the Eu3+ ion and the energy difference between the second ligand and the first ligand. PMID:21105388

Zhou, He-feng; Zhang, Ting; Hao, Yu-ying; Xu, Hui-xia; Wang, Hua

2010-09-01

410

Magnetic properties of ilmenite-hematite films and bulk samples  

NASA Astrophysics Data System (ADS)

Ilmenite-hematite [(FeTiO3)1-x-(Fe2O3)x] is a solid solution system with intrinsic ferrimagnetic and semiconducting properties. Bulk ceramic samples and epitaxial thin films have been prepared with magnetization values of up to 1500 G (bulk) and 700 G (thin films) at room temperature. Superparamagnetic behavior was discriminated from ferrimagnetic properties using field cooled and zero field cooled measurements. The blocking temperature exceeds room temperature for samples with composition x>0.25. Using magnetic force microscopy, the domain structure in the thin ilmenite-hematite films was detected.

Dou, J.; Navarrete, L.; Schad, R.; Padmini, P.; Pandey, R. K.; Guo, H.; Gupta, A.

2008-04-01

411

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

2007-02-27

412

Microwave absorption properties of carbon nanocoils coated with highly controlled magnetic materials by atomic layer deposition.  

PubMed

In this work, atomic layer deposition is applied to coat carbon nanocoils with magnetic Fe(3)O(4) or Ni. The coatings have a uniform and highly controlled thickness. The coated nanocoils with coaxial multilayer nanostructures exhibit remarkably improved microwave absorption properties compared to the pristine carbon nanocoils. The enhanced absorption ability arises from the efficient complementarity between complex permittivity and permeability, chiral morphology, and multilayer structure of the products. This method can be extended to exploit other composite materials benefiting from its convenient control of the impedance matching and combination of dielectric-magnetic multiple loss mechanisms for microwave absorption applications. PMID:23171130

Wang, Guizhen; Gao, Zhe; Tang, Shiwei; Chen, Chaoqiu; Duan, Feifei; Zhao, Shichao; Lin, Shiwei; Feng, Yuhong; Zhou, Lei; Qin, Yong

2012-12-05

413

Magnetic properties, magnetoresistivity and magnetocaloric effect in Gd x La 1? x- MnSi alloys  

Microsoft Academic Search

The results of magnetization, magnetoresistivity and magnetocaloric effect (MCE) studies performed on polycrystalline samples of the GdxLa1?xMnSi (x=0.5, 0.6, 0.7, 0.8, 0.9, 1.0) compounds were presented. Complex measurements were carried out on the GdxLa1?xMnSi compounds to determine the influence of substitution in the rare earth (R) sublattice on the magnetic and related properties of these compounds. The compounds with x?0.6

T. I. Ivanova; S. A. Nikitin; W. Suski; G. A. Tskhadadze; I. A. Ovtchenkova; D. Badurski

2009-01-01

414

Mössbauer effect study and magnetic properties of a ferromagnetic homologue of bromobis(diethyldithiocarbamato)iron(III)  

NASA Astrophysics Data System (ADS)

Mossbauer spectroscopy and magnetic susceptibility properties of a crystal modification of the title complex, denoted Fe(dtc) 2Br, show that the iron atoms in this material become ferromagnetically ordered with Tc = 1.52 × 0.02 K. This result is consistent with a magnetic specific heat anomaly recently observed in similar material by Yoshikawa et al. Mössbauer effect hfs show that the lower Kramers doublet from the orbital singlet, spin quartet ground term is of composition | S = 3/2, MS = ± 1/2).

Decurtins, S.; Wells, F. V.; Sun, K. C.-P.; Wickman, H. H.

1982-06-01

415

Magnetic properties of FeAl2 and Fe2Al5  

NASA Astrophysics Data System (ADS)

We have investigated magnetic properties of the FeAl2 and Fe2Al5 intermetallic compounds. By measuring the zero-field-cooled and field-cooled static (dc) magnetic susceptibilities in low and high magnetic fields, the frequency-dependent (ac) susceptibility, the magnetization versus the magnetic field, and the thermoremanent magnetization time decay, we found that the magnetic structures of FeAl2 and Fe2Al5 are richer than those published so far in the literature. FeAl2 undergoes complex two-step magnetic ordering. At T ? 32 K, a magnetic phase transition (not yet specified) takes place in which a small fraction of the Fe spins participate, whereas at Tf2 ? 12 K, the majority spin fraction undergoes a spin-freezing transition to a spin glass phase. Fe2Al5 undergoes a transition to a spin glass phase at the spin freezing temperature Tf ? 3 K, which was not reported previously. The spin glass phase in Fe2Al5 is “soft” and fragile with respect to the external magnetic field and can only be observed in low magnetic fields below ˜100 Oe. The origins of the spin glass ordering in the FeAl2 and Fe2Al5 phases are randomness and frustration that are present on the Fe sublattices of both compounds. In FeAl2, the Fe spins are positioned randomly on the three mixed-occupation Al/Fe sites of the unit cell, whereas in Fe2Al5, partial occupation of the Fe-neighboring Al2 and Al3 atomic sites imposes different degrees of Fe moment screening by the electron cloud, resulting in a random distribution of the magnetic moment sizes. Geometric frustration because of positioning of the antiferromagnetically coupled Fe spins on triangles is present in both compounds as well.

Jagli?i?, Z.; Vrtnik, S.; Feuerbacher, M.; Dolinšek, J.

2011-06-01

416

Chromium removal by combining the magnetic properties of iron oxide with adsorption properties of carbon nanotubes  

Microsoft Academic Search

The adsorption features of multiwall carbon nanotubes (MWCNTs) with the magnetic properties of iron oxides have been combined in a composite to produce a magnetic adsorbent. Composites of MWCNT\\/nano-iron oxide were prepared, and were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and Fourier transform infrared spectroscopy (FTIR). XRD suggests that the magnetic phase formed is maghemite

V. K. Gupta; Shilpi Agarwal; Tawfik A. Saleh

2011-01-01

417

Magnetic properties of ultrasmall iron oxide nanoclusters in a polymer matrix  

Microsoft Academic Search

The synthesis of iron oxide nanoclusters in the matrix of an interpolyelectrolyte complex based on poly(acrylic acid) and\\u000a polyethylenimine is described. The effect of the method of cluster formation (by the oxidation or reduction of iron ions)\\u000a on the magnetic properties of polymer nanocomposites was studied. The influence of the surface modification of iron oxide\\u000a nanoclusters in a polymer matrix

I. P. Suzdalev; Yu. V. Maksimov; V. E. Prusakov; V. V. Matveev; V. K. Imshennik; S. V. Novichikhin; A. B. Zezin; V. B. Rogozeva; S. P. Valueva

2008-01-01

418

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

419

Magnetic Anisotropy and Magneto-Transport Properties of Co–Ni–N Granular Alloys Thin Films  

Microsoft Academic Search

The effect of nitrogen addition on the morphology, magnetic anisotropy, and magnetoresistance properties of Co–Ni–N granular\\u000a thin films were investigated. The films were grown by electrodeposition onto aluminum substrates at room temperature. By a\\u000a complex process of cationic catalysis occurring at the cathode\\/electrolyte interface, nitrogen is adsorbed in the Co–Ni film.\\u000a Finally, a granular film grows by a tridimensional progressive

S. I. Tanase; V. Georgescu

420

Numerical Modeling of Magnetic Properties of Ferromagnetic Shape Memory Materials Depending on Temperature and Stress  

Microsoft Academic Search

This paper deals with a numerical modeling of nonlinear magnetic properties of ferromagnetic shape memory alloys (FSMAs). In order to design new magnetic actuators by using the FSMAs, it is necessary to develop an effective engineering modeling, which can represent the nonlinear magnetic properties depending on stress and temperature. This paper presents measured relationship among stress, temperature and magnetic properties

Takashi Todaka; Daisuke Yamamichi; Masato Enokizono

2011-01-01

421

Magnetic properties of Fe/Zr multilayers  

SciTech Connect

Measurements of ferromagnetic resonance (FMR), magnetic moment, and torque curves have been made for three series of Fe/Zr multilayers (MLs) with thickness ratio of Fe to Zr sublayers equal to 2:1, 1:1, and 1:2, respectively. The authors show that Fe/Zr MLs readily yield to amorphization by a solid-state reaction (SSR) during the deposition process. Nevertheless, the resulting structure may be regarded as inhomogeneous one; there still exist some ferromagnetic phases that they relate to the Fe atoms in various surroundings.

Dubowik, J.; Stobiecki, F.; Szymanski, B. [Polish Academy of Sciences, Poznan (Poland). Inst. of Molecular Physics

1994-03-01

422

Magnetic properties of Fe/Tb multilayers  

SciTech Connect

Multilayered Fe/Tb samples were prepared under ultrahigh vacuum conditions ({ital p}{lt}10{sup {minus}9} mbar) on kapton substrates. A total of four different samples were prepared. Three of them correspond to a series where the Tb thickness is constant at 26 A and Fe varies from 10 to 30 A. The fourth one is the first of a new series where Tb is 7 A thick and Fe 40 A. The samples were investigated by means of SQUID magnetometry and Moessbauer spectroscopy. All samples show perpendicular magnetic anisotropy at low temperature (4.2 K), but only two of them are able to show it at room temperature.

Badia, F.; Badry, M.A.; Zhang, X.X.; Tejada, J. (Dep. Fisica Fonamental, Universitat de Barcelona, Diagonal, 647, E-08028 Barcelona (Spain)); Brand, R.A.; Scholz, B.; Keune, W. (Laboratorium fuer Angewandte Physik, 4100 Duisburg (Germany))

1991-11-15

423

Synthesis and Properties of Ortho-Nitro-Fe Complex  

SciTech Connect

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

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

2011-07-15

424

Tunable electronic and magnetic properties of WS2 nanoribbons  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

425

Control of Magnetic Properties Across Metal to Insulator Transitions  

NASA Astrophysics Data System (ADS)

Controlling the magnetic properties of ferromagnetic (FM) thin films without magnetic fields is an on-going challenge in condensed matter physics with multiple technological implications. External stimuli and proximity effects are the most used methods to control the magnetic properties. An interesting possibility arises when ferromagnets are in proximity to materials that undergo a metal-insulator (MIT) and structural phase transition (SPT). The stress associated with the structural changes produces a magnetoelastic anisotropy in proximity coupled ferromagnetic films that allows controlling the magnetic properties without magnetic fields. Canonical examples of materials that undergo MIT and SPT are the vanadium oxides (VO2 and V2O3). VO2 undergoes a metal/rutile to an insulator/monoclinic phase transition at 340 K. In V2O3 the transition at 160 K is from a metallic/rhombohedral to an insulating/ monoclinic phase. We have investigated the magnetic properties of different combinations of ferromagnetic (Ni, Co and Fe) and vanadium oxide thin films. The (0.32%) volume expansion in VO2 or the (1.4%) volume decrease in V2O3 across the MIT produces an interfacial stress in the FM overlayer. We show that the coercivities and magnetizations of the ferromagnetic films grown on vanadium oxides are strongly affected by the phase transition. The changes in coercivity can be as large as 168% and occur in a very narrow temperature interval. These effects can be controlled by the thickness and deposition conditions of the different ferromagnetic films. For VO2/Ni bilayers the large change in the coercivity occurring above room temperature opens the possibilities for technological applications.

de La Venta, Jose

2013-03-01

426

Investigation on microstructure, texture, and magnetic properties of hot deformed Nd-Fe-B ring magnets  

NASA Astrophysics Data System (ADS)

Radially oriented Nd-Fe-B ring magnets have been prepared by backward extrusion of melt-spun powder. The position dependent of the microstructure, the magnetic properties, and the crystal alignment of the extruded rings have been investigated. The magnetic properties in radial direction increase slightly along the axis from the bottom to the middle then steeply decrease at the upper end of the ring. The magnetic properties and x-ray diffraction patterns of the upper end are very close to that of the isotropic pressed precursor. It suggests that the extruded ring approximately retains the initial structure at its upper end which is because the formation of texture is difficult at the initial stage of hot extrusion. Characteristic microstructure morphologies were found at different spatial positions: flake-shaped grains for the inner, elongated grains for the middle, and particle-shaped grains for the outer region in the cross section. Only particle-shaped grains were observed at the upper end of the ring. But the circumferential homogeneity of the surface magnetic flux densities is better in an extruded ring magnet than in a radially oriented ring prepared by sintering method. The deformation and texture formation processes were discussed. The deformation and texture formation in backward extruded magnets from melt-spun Nd-Fe-B precursors may possibly involve grain boundary sliding and grain rotation, solution-precipitation process, and preferred growth of Nd2Fe14B nanograins along the easy growth a-axis.

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

2010-05-01

427

Magnetic and crystallographic properties of synthetic titanomaghemite  

NASA Astrophysics Data System (ADS)

Systematic magnetic and crystallographic studies were made on 57 titanomaghemite samples produced from sintered titanomagnetites with x values of 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0. Curie temperature and lattice parameter values are often significantly different from results of previous studies (Ozima and Sakamoto, 1971; Readman and O'Reilly, 1972; Nishitani, 1979), particularly for x values of 0.4 and 0.6. Other important results are: (1) Oxidation of titanomagnetite is mainly a function of temperature. Atmosphere and Ti content have little influence. (2) Progressive oxidation of homogeneous titanomaghemites can take place in the presence of a rhombohedral phase. The amount of rhombohedral phase produced during oxidation increases with increasing temperature and (less conclusively) with decreasing Ti content. (3) Saturation magnetization measurements at low temperatures show both P- and Q-type ferrimagnetic behavior in titanomaghemites, and also show the Verwey (?) transition in titanomaghemites with composition x=0.0. (4) The temperature of spinel inversion increases with degree of oxidation. Slightly oxidized samples invert near 300°C; for samples with z > 0.8 the inversion temperature is above 450°C. This last result, although neither expected nor understood, is supported by results of thermomagnetic studies on some oceanic basalts.

Keefer, C. M.; Shive, P. N.

1982-12-01

428

Nanocrystalline Sm12.5(Co,Zr)87.5 magnets: synthesis and magnetic properties  

NASA Astrophysics Data System (ADS)

Isotropic nanostructured Sm12.5Co87.5-xZrx (/0<=x<=5) magnets with the TbCu7 structure have been synthesized by mechanical milling and subsequent annealing. The remanence is found much enhanced in the nanostructured Sm(Co,Zr)7 magnets with a grain size of 10-20nm. A suitable amount of Zr addition (/x=1, 2) is helpful to improve hard magnetic properties, including high remanence ratio of 0.71, coercivities up to 21kOe, and energy products up to 13.0MGOe, and hard magnetic properties are sensitive to the milling time and the annealing temperature. The dependence of hard magnetic properties on milling time may be correlated to the refinement of grain size and the intergranular structure induced during the milling and the subsequent annealing. The enhancement of remanence due to a small amount of Zr in this series of Sm12.5Co87.5-xZrx powders results from the enhanced exchange coupling between the nanosized grains. The hard magnetic properties are discussed with correlation to the milling process and in terms of the nanostructure developed in these materials.

Tang, H.; Liu, Y.; Sellmyer, D. J.

2002-03-01

429