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1

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

2

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

3

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

2012-10-15

4

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

5

Magnetic properties and structure of a Cu IIDy III heterodinuclear Schiff base complex  

NASA Astrophysics Data System (ADS)

The crystal structure of a new heterodinuclear lanthanide complex, L 2Cu(Me 2CO)Dy(NO 3) 3 (L 2= N, N'-bis(2-hydroxy-3-methoxy-benzylidene)-ethylenediamine) has determined and the magnetic properties of the complex investigated. (C 18H 18N 2O 4)Cu(C 3H 6O)Dy(NO 3) 3, monoclinic, space group P2 1/ c, with a=9.875(2), b=18.870(7), c=15.675(8) Å, ?=95.45(3)°, V=2908(2) Å 3, Z=4. The structure consists of ordered dinuclear units with Cu II and Dy III ions bridged by two phenolato oxygen atoms of the Schiff base ligand. The Cu II ion has a square-pyramidal geometry involving the basal N 2O 2 donor atoms of the Schiff base ligands and one oxygen atom of the acetone molecule at the apex position. The Dy III ion is decacoordinated by the four oxygen atoms of L 2 and six oxygen atoms from the three bidentate nitrate ions. The Cu⋯Dy separation is 3.461(2) Å. The ?T versus T plots, ? being the molar magnetic susceptibility per Cu IIDy III unit and T the temperature, has been measured in the 4.5-300 K temperature range. The magnetic properties of the compound are dominated by the crystal field effect on the Dy III site, masking the magnetic interaction between the paramagnetic centers.

Elmali, A.; Elerman, Y.

2005-02-01

6

Magnetic properties of copper(II) complexes containing peptides. Crystal structure of [Cu(phe-leu)  

NASA Astrophysics Data System (ADS)

A novel copper(II) complex containing the peptide phe-leu has been prepared and characterized. The crystal structure of [Cu(phe-leu)] ( 1) was determined by X-ray diffraction. The presence of carboxylate and amido bridges allows the formation of an extended 2D arrangement. This structure is similar to those found in [Cu(gly-val)] · 1/2H 2O ( 2), [Cu(val-gly)] ( 3), [Cu(val-phe)] ( 4), and [Cu(phe-phe)] ( 5). The magnetic properties of compounds 1- 5 were studied and analyzed comparatively. The experimental data show that the magnetic interactions are mainly transmitted through ? 2-COO - bridges, being ferromagnetic for 1 and 3, and antiferromagnetic for 2, 4 and 5.

Sanchiz, J.; Kremer, C.; Torre, M. H.; Facchin, G.; Kremer, E.; Castellano, E. E.; Ellena, J.

2006-09-01

7

Synthesis, crystal structure, magnetic property and nuclease activity of a new binuclear cobalt(II) complex.  

PubMed

One new binuclear Co(II) complex of N,N,N',N'-tetrakis(2-benzimidazolylmethyl)-2-hydroxyl-1,3-diaminopropane (HL), [Co(2)L(mu(2)-Cl)](ClO(4))(2) x 3CH(3)CN x C(2)H(5)OC(2)H(5) (1), has been synthesized and its crystal structure and magnetic properties are shown. In 1, each Co(II) atom has a distorted trigonal bipyramidal geometry with a N(3)OCl donor set. The central two Co(II) atoms are bridged by one alkoxo-O atom and one Cl atom with the Co1-Co2 separation of 3.239 A. Susceptibility data of 1 indicate strong intramolecular antiferromagnetic coupling of the high-spin Co(II) atoms. In this paper, the interaction with calf thymus DNA was investigated by UV absorption and fluorescent spectroscopy. Results show the complex binds to ct-DNA with a intercalative mode. The interaction between complex 1 and pBR322 DNA has also been investigated by submarine gel electrophoresis, noticeably, the complex exhibits effective DNA cleavage activity in the absence of any external agents. PMID:17140667

Tian, Jin-Lei; Feng, Li; Gu, Wen; Xu, Guang-Jun; Yan, Shi-Ping; Liao, Dai-Zheng; Jiang, Zong-Hui; Cheng, Peng

2007-02-01

8

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

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

9

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

10

Magnetic properties and electronic structure of neptunyl(VI) complexes: wavefunctions, orbitals, and crystal-field models.  

PubMed

The electronic structure and magnetic properties of neptunyl(VI), NpO2(2+), and two neptunyl complexes, [NpO2(NO3)3](-) and [NpO2Cl4](2-), were studied with a combination of theoretical methods: ab initio relativistic wavefunction methods and density functional theory (DFT), as well as crystal-field (CF) models with parameters extracted from the ab initio calculations. Natural orbitals for electron density and spin magnetization from wavefunctions including spin-orbit coupling were employed to analyze the connection between the electronic structure and magnetic properties, and to link the results from CF models to the ab initio data. Free complex ions and systems embedded in a crystal environment were studied. Of prime interest were the electron paramagnetic resonance g-factors and their relation to the complex geometry, ligand coordination, and nature of the nonbonding 5f orbitals. The g-factors were calculated for the ground and excited states. For [NpO2Cl4](2-), a strong influence of the environment of the complex on its magnetic behavior was demonstrated. Kohn-Sham DFT with standard functionals can produce reasonable g-factors as long as the calculation converges to a solution resembling the electronic state of interest. However, this is not always straightforward. PMID:24848696

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

2014-06-23

11

Synthesis, magnetic properties and dynamic behavior of cobalt complexes with an anthracene-containing dioxolene ligand.  

PubMed

The anthracene-functionalized cobalt complexes [Co(L)(TPA)]PF6 (1) and [Co(L)(Me(n)TPA)]PF6 (2, n = 1; 3, n = 2; 4, n = 3) were synthesized by the combination of 9-(3,4-dihydroxyphenyl)anthracene (H2L) and tris(2-pyridylmethyl)amine (TPA) or its derivatives (Me(n)TPA, n = 1, 2, 3). Characterization of complexes 1-4 was performed by UV-vis absorption, IR, (1)H NMR, and magnetic susceptibility measurements. In the solid state, the variable-temperature magnetic susceptibility data showed that complex 1 is low-spin cobalt(III) catecholate (Co(III)(LS)-Cat), while complex 4 is high-spin cobalt(II) semiquinonate (Co(II)(HS)-SQ) in the range 4.5-400 K. The susceptibility data of complexes 2 and 3 suggested valence tautomerism between the Co(III)(LS)-Cat and Co(II)(HS)-SQ forms. Light-induced valence tautomerism was observed in complexes 2 and 3 at 5 K by photo-irradiation. In solution, the temperature dependence of (1)H NMR spectra of 1 and 2 showed an equilibrium between their geometrical isomers. PMID:25075775

Katayama, Koichi; Hirotsu, Masakazu; Kinoshita, Isamu; Teki, Yoshio

2014-09-21

12

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

PubMed

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

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

2014-04-24

13

Synthesis, structure, and magnetic properties of two 1-D helical coordination polymeric Cu(II) complexes  

NASA Astrophysics Data System (ADS)

Two helical coordination polymeric copper(II) complexes bearing amino acid Schiff bases HL or HL', which are condensed from 2-hydroxy-1-naphthaldehyde with 2-aminobenzoic acid or L-valine, respectively, have been prepared and characterised by X-ray crystallography. In [CuL] n ( 1) the copper(II) atoms are bridged by syn- anti carboxylate groups giving infinite 1-D right-handed helical chains which are further connected by weak C-H⋯Cu interactions to build a 2-D network. While in [CuL'] n ( 2) the carboxylate group acts as a rare monatomic bridge to connect the adjacent copper(II) atoms leading to the formation of a left-handed helical chain. Magnetic susceptibility measurements indicate that 1 exhibits weak ferromagnetic interactions whereas an antiferromagnetic coupling is established for 2. The magnetic behavior can be satisfactorily explained on the basis of the structural data.

Bian, He-Dong; Yang, Xiao-E.; Yu, Qing; Chen, Zi-Lu; Liang, Hong; Yan, Shi-Ping; Liao, Dai-Zheng

2008-01-01

14

Ligand effects on the structures and magnetic properties of tricyanomethanide-containing copper(II) complexes.  

PubMed

The preparation, crystal structure and magnetic properties of four heteroleptic copper(II) complexes with the tricyanomethanide (tcm(-)) and the heterocyclic nitrogen donors 3,6-bis(2-pyridyl)pyridazine (dppn), 2,5-bis(2-pyridyl)pyrazine (2,5-dpp), 2,3-bis(2-pyridyl)pyrazine (2,3-dpp) and 2,3-bis(2-pyridyl)quinoxaline (2,3-dpq) are reported, {[Cu(2)(dppn)(OH)(tcm)(2)] x tcm}(n) (1), {[Cu(2,5-dpp)(tcm)] x tcm}(n) (2), {[Cu(2)(2,3-dpp)(2)(tcm)(3)(H(2)O)(0.5)] x tcm x 0.5H(2)O}(n) (3) and [Cu(2,3-dpq)(tcm)(2)](n) (4). 1 has a ladder-like structure with single mu-1,5-tcm ligands forming the sides and a bis-bidentate dppn and a single mu-hydroxo providing the rung. Each copper atom in 1 exhibits a distorted square pyramidal CuN(4)O surrounding: the basal plane is built by the hydroxo-oxygen, a nitrile-nitrogen atom from a tcm group and one pyrazine and a pyridyl nitrogen atoms from the dppn whereas the apical position is filled by a nitrile-nitrogen atom from a symmetry-related tcm ligand. The structures of 2-4 consists of zig-zag (2 and 3)/linear (4) chains of copper(II) ions which are bridged by either bis-bidentate 2,5-dpp (2) and 2,3-dpp (3) molecules or single mu-1,5-tcm (4) groups. The copper atoms in 2 and 4 are five coordinated with distorted trigonal bipyramidal (2) and square pyramidal (4) CuN(5) surroundings. The axial positions in 2 are occupied by two pyridyl-nitrogen atoms from two 2,5-dpp ligands whereas the trigonal plane is built by a nitrile-nitrogen from a terminally bound tcm group and two pyrazine nitrogen atoms from two 2,5-dpp molecules. The basal plane in 4 is defined by a pyridyl and a pyrazine nitrogen atoms from the bidentate 2,3-dpq ligand and two nitrile nitrogen atoms from two tcm groups (one terminal and the other bridging) whereas the apical position is filled by a nitrile nitrogen from another tcm ligand. The crystallographically independent copper atoms in 3 [Cu(1) and Cu(2)] exhibit elongated octahedral geometries being defined by four nitrogen atoms from two 2,3-dpp groups [Cu(1) and Cu(2)] either two terminally bound tcm ligands [Cu(1)] or a water molecule and a monodentate tcm ligand [Cu(2)] in cis positions. Magnetic susceptibility measurements for 1-4 in the temperature range 1.9-295 K reveal the occurrence of strong [J ca.-1000 cm(-1) (1); H = -JS(A) x S(B)] and weak [J = -0.13 (2), -0.67 (3) and -0.18 cm(-1) (4); H = -J Sigma(I)S(i) x S(i+1)] antiferromagnetic interactions in agreement with the different nature of the exchange pathways involved, diazine and single mu-hydroxo (1) and the extended 2,5-dpp (2), 2,3-dpp (3) and single mu-1,5-tcm (4) bridges with copper-copper separations of 3.363(8) (1), 7.111(1) (2), 6.823(1) and 7.056(1) (3) and 7.446(1) A (4). PMID:17985027

Yuste, Consuelo; Bentama, Abdeslem; Stiriba, Salah-Eddine; Armentano, Donatella; De Munno, Giovanni; Lloret, Francesc; Julve, Miguel

2007-11-28

15

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

PubMed

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

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

2014-03-14

16

Sandwich transitional metal complexes with tungstobismuthates and 1-methylimidazole ligands: Syntheses, structures and magnetic properties  

NASA Astrophysics Data System (ADS)

Two novel sandwich-type coordination compounds of tungstobismuthate Na 9[{Na(H 2O) 2} 3{Co II(mim)} 3(Bi IIIW VI9O 33) 2]·36H 2O ( 1) and Na 7H 2[{Na(H 2O) 2} 3{Mn II(mim)} 3(Bi IIIW VI9O 33) 2]·21H 2O ( 2) (mim = 1-methylimidazole) have been synthesized in alkaline aqueous solution. Their composition and structures were established by elemental analyses, IR spectra, and single crystal X-ray diffraction. These two complexes consist of two tri-vacant [?-B-Bi IIIW VI9O 33] 9- moieties linked through three Cu II or Mn II and three Na + ions. These Na + cations around the complex anion were bonded with some terminal and bridging oxo atoms from the complex anion and water molecules. In addition to tungstobismuthate ligands, 1-methylimidazoles also coordinate to sandwich transitional metal ions. Magnetic measurement indicates the existence of antiferromagnetic interaction between the trimeric transitional metal ions for 1 and 2.

Liu, Hong; Xu, Lin; Gao, Guanggang; Li, Fengyan; Jiang, Ning

2008-04-01

17

Structural, Magnetic and Electronic Properties of the Sr2CoNbO6 Complex Perovskite  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

18

Formation of a g-quartet-fe complex and modulation of electronic and magnetic properties of the fe center.  

PubMed

Although the G-quartet structure has been extensively investigated due to its biological importance, the formation mechanism, in particular, the necessity of metal centers, of an isolated G-quartet on solid surfaces remains ambiguous. Here, by using scanning tunneling microscopy under well-controlled ultra-high-vacuum conditions and density functional theory calculations we have been able to clarify that besides the intraquartet hydrogen bonding a metal center is mandatory for the formation of an isolated G-quartet. Furthermore, by subtly perturbing the local coordination bonding schemes within the formed G-quartet complex via local nanoscale scanning tunneling microscopy manipulations, we succeed in modulating the d orbitals and the accompanying magnetic properties of the metal center. Our results demonstrate the feasibility of forming an isolated G-quartet complex on a solid surface and that the strategy of modulating electronic and magnetic properties of the metal center can be extended to other related systems such as molecular spintronics. PMID:25347538

Wang, Likun; Kong, Huihui; Zhang, Chi; Sun, Qiang; Cai, Liangliang; Tan, Qinggang; Besenbacher, Flemming; Xu, Wei

2014-11-25

19

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

20

Relationships between electron density and magnetic properties in water-bridged dimetal complexes.  

PubMed

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

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

2014-11-01

21

The Unusual Magnetic Resonance Properties of Trigonal Prismatic Tc and Re Complexes  

Microsoft Academic Search

The electron paramagnetic resonance (EPR) spectra of the trigonal prismatic complexes Tc(abt)3, Tc(bdt)3, Re(abt)3 and Re(bdt)3 (abt, O-aminobenzenethiol; bdt, benzene-1,2-dithiol) in dilute frozen solution are interpreted in terms of an axially symmetric spin\\u000a Hamiltonian, with g values close to two, principal hyperfine couplings of |A\\u000a Tc| ~ 5–12 × 10?4 cm?1, nuclear quadrupole couplings of |P\\u000a Tc| ~ 0.3–0.35 × 10?4 cm?1 and the unusual values 5 × 10?4 cm?1 ~ |A\\u000a \\u000a zz\\u000a Re| P\\u000a Re| ~ |A\\u000a \\u000a xx

Simon C. Drew; John Baldas; John F. Boas

22

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

PubMed

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

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

2015-04-01

23

Ab initio study of magnetic properties of complexes formed by an Fe impurity and an intrinsic interstitial defect in ZnO  

NASA Astrophysics Data System (ADS)

By density factional supercell calculations we computed the total energy and the magnetic properties of isolated complexes formed in wurtzite ZnO doped with diluted Fe impurities in the presence of interstitial atoms of Zn or O. Interstitial O occupies preferentially a site with octahedral symmetry with substitutional Fe in the first neighbor shell, thus forming the complex FeZn-IO. In contrast, the complex FeZn-IZn is energetically unfavored with respect to the case where the two components are far apart. For oxygen-rich growth conditions, a significant population of complexes FeZn-IO is stable at (and above) room temperature, providing a key to understanding the room-temperature magnetism of this system. Interstitial oxygen, coupled with diluted Fe impurities, exhibit a density of states spin polarized at the Fermi energy.

Debernardi, A.; Fanciulli, M.

2011-07-01

24

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

PubMed

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

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

2014-09-01

25

Solution 1H NMR study of the active site molecular structure and magnetic properties of the cyanomet complex of the isolated, tetrameric ?-chain from human adult hemoglobin  

Microsoft Academic Search

The solution molecular structure and the electronic and magnetic properties of the heme pocket of the cyanomet complex of the isolated ?-chain of human adult hemoglobin, HbA, have been investigated by homonuclear 2D 1H NMR in order to assess the extent of assignments allowed by 1H NMR of a homo-tetrameric 65-kDa protein, to guide the future assignments of the heterotetrameric

Anh-Tuyet T. Tran; Urszula Kolczak; Gerd N. La Mar

2004-01-01

26

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

2011-04-01

27

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

PubMed

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

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

2014-06-01

28

Magnetic Properties of  

Microsoft Academic Search

Magnetic properties of LnTi{sub 0.5}V{sub 0.5}Oâ (Ln=Ce and Pr), which are solid solutions between the perovskites LnTiOâ and LnVOâ, have been investigated. Their crystal structures are an orthorhombic perovskite type (Pnma), where the Ti and V ions are settled with random occupation at the same crystallographic site. DC susceptibility-temperature (Ï-T) curves exhibit magnetic transitions at T{sub N}â¼50 K. These temperatures

K. Yoshii; H. Abe

2001-01-01

29

A racemic and enantiopure unsymmetric diiron(III) complex with a chiral o-carborane-based pyridylalcohol ligand: combined chiroptical, magnetic, and nonlinear optical properties.  

PubMed

The design of molecule-based systems combining magnetic, chiroptical and second-order optical nonlinear properties is still very rare. We report an unusually unsymmetric diiron(III) complex 1, in which three bulky chiral carboranylpyridinealkoxide ligands (oCBhmp(-)) bridge both metal ions and the complex shows the above-mentioned properties. The introduction of o-carborane into the 2-(hydroxymethyl)pyridine (hmpH) architecture significantly alters the coordination of the simple or aryl-substituted 2-hmpH. The unusual architecture observed in 1 seems to be triggered by the poor nucleophilicity of our alkoxide ligand (oCBhmp(-)). A very rare case of spontaneous resolution takes place on precipitation or exposure to solvent vapor for the bulk compound, as confirmed by a combination of single-crystal and powder X-ray diffraction, second-harmonic generation, and circular dichroism. The corresponding enantiopure complexes (+)1 and (-)1 have also been synthesized and fully characterized. This research provides a new building block with unique geometry and electronics to construct coordination complexes with multifunctional properties. PMID:24338928

Di Salvo, Florencia; Tsang, Min Ying; Teixidor, Francesc; Viñas, Clara; Planas, José Giner; Crassous, Jeanne; Vanthuyne, Nicolas; Aliaga-Alcalde, Núria; Ruiz, Eliseo; Coquerel, Gerard; Clevers, Simon; Dupray, Valerie; Choquesillo-Lazarte, Duane; Light, Mark E; Hursthouse, Michael B

2014-01-20

30

A series of weak ferromagnets based on a chromium-acetylide-TTF type complex: correlation of the structures and magnetic properties and origin of the weak ferromagnetism.  

PubMed

The crystal structures and magnetic properties of a series of new weak ferromagnets containing a chromium-acetylide-tetrathiafulvalene (TTF) type complex, [CrCyclam(C?C-5-methyl-4'5'-ethylenedithio-TTF)2](2+) ([1](2+)), were investigated. The six new isostructural weak ferromagnets [1][BF4]2(PhF)2(MeCN), [1][ClO4]2(PhF)2(MeCN), [1][ReO4]2(PhCl)2(MeCN), [1][ClO4]2(PhBr)3, [1][ReO4]2(PhBr)3, and [1][ClO4]2(PhI)3 contain ferrimagnetic chain structures of [1](2+)? with different interchain distances that are dependent on the sizes of the anions and solvent molecules. Magnetic measurements of the salts revealed that the weak ferromagnetic transition temperature gradually increases from 14.5 to 26.0 K as the interchain distance decreases from 3.997(2) to 3.803(2) Å, while the remanent magnetization at 2 K decreases from 0.0215 to 0.0079 ?B. The observed magnetic properties and crystal structures suggest that the weak ferromagnetism originates from the single-ion anisotropy of [1](2+), where a stronger interchain antiferromagnetic interaction not only causes a higher transition temperature but also suppresses the noncollinear canted spin alignment. PMID:24161267

Nishijo, Junichi; Enomoto, Masaya

2013-11-18

31

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

PubMed

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

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

2013-09-14

32

Essential properties of a D2+ molecular complex confined in ring-like nanostructures under external probes: Magnetic field and hydrostatic pressure  

NASA Astrophysics Data System (ADS)

A rigorous adiabatic approximation is used to investigate the energy states of the singly ionized double-donors D2+ complex formed by the coupling of a conduction band electron and two donor centers in a quantum ring with rectangular cross-section. The effects of changing the relative position between the Coulombic centers and the quantum ring geometry parameters, as well as the influence of external probes such as applied magnetic fields and hydrostatic pressure, are particularly studied, highlighting the important contribution of the repulsive inter-center interaction. The suppression of the Aharonov-Bohm ground state oscillations associated with the localization of the electron by the fixed donors is discussed. Comparison between the essential properties of an actual hydrogen ion H2+ and those of the D2+ complex trapped within a quantum ring shows that the strong electron confinement substantially increases the D2+ stability effects.

R-Fulla, M.; Marín, J. H.; Gutiérrez, W.; Mora-Ramos, M. E.; Duque, C. A.

2014-03-01

33

Crystal structure and magnetic properties of two isomeric three-dimensional pyromellitate-containing cobalt(II) complexes.  

PubMed

The hydrothermal preparation, crystal structure determination, and magnetic study of two isomers made up of 1,2,4,5-benzenetetracarboxylate and high-spin Co(II) ions of formula [Co2(bta)(H2O)4]n x 2n H2O (1 and 2; H4bta = 1,2,4,5-benzenetetracarboxylic acid) are reported. 1 and 2 are three-dimensional compounds whose structures can be described as (4,4) rectangular layers of trans-diaquacobalt(II) units with the bta(4-) anion acting as tetrakis-monodentate ligand through the four carboxylate groups, which are further connected through other trans-[Co(H2O)2](2+) (1) and planar [Co(H2O)4](2+) (2) entities, with the bridging units being a carboxylate group in either the anti-syn (1) or syn-syn (2) conformations and a water molecule (2). The study of the magnetic properties of 1 and 2 in the temperature range 1.9-300 K shows the occurrence of weak antiferromagnetic interactions between the high-spin Co(II) ions, with the strong decrease of chi(M)T upon cooling being mainly due to the depopulation of the higher energy Kramers doublets of the six-coordinated Co(II) ions. The computed values of the exchange coupling between the Co(II) ions across anti-syn carboxylate (1) and syn-syn carboxylate/water (2) bridges are J = -0.060 (1) and -1.90 (2) cm(-1) (with the Hamiltonian being defined as H = -Jsigma(i,j)S(i) x S(j)). These values follow the different conformations of the carboxylate bridge in 1 (anti-syn) and 2 (syn-syn) with the occurrence of a double bridge in 2 (water/carboxylate). PMID:18700754

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

2008-09-15

34

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

SciTech Connect

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

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

2013-02-15

35

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

36

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

E-print Network

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

Weston, Ken

37

Magnetic properties of iron nanoparticle  

SciTech Connect

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

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

2010-05-15

38

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

SciTech Connect

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

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

2013-10-15

39

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

PubMed

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

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

2011-09-28

40

From magnetic fluids up to complex biocompatible nanosized magnetic systems  

Microsoft Academic Search

The paper presents magnetic fluid as an excellent material platform for producing more complex magnetic drug delivery systems. In addition, the paper discusses the nanoparticle morphological (electron microscopy) and structural (X-ray diffraction) characterizations. Mossbauer spectroscopy and photoacoustic spectroscopy are revisited as key tools in the characterization of the magnetic core and diamagnetic shell of the magnetic nanoparticle, respectively.

P. C. MORAIS

41

Two-dimensional layer architecture assembled by Keggin polyoxotungstate, Cu(II)-EDTA complex and sodium linker: Synthesis, crystal structures, and magnetic properties  

SciTech Connect

Reaction of Keggin polyoxotungstate with copper(II)-EDTA (EDTA=ethylenediamine tetraacetate) complex under mild conditions led to the formation of hybrid inorganic-organic compounds Na{sub 4}(OH)[(Cu{sub 2}EDTA)PW{sub 12}O{sub 40}].17H{sub 2}O (1) and Na{sub 4}[(Cu{sub 2}EDTA)SiW{sub 12}O{sub 40}].19H{sub 2}O (2). The single-crystal X-ray diffraction analyses reveal their two structural features: (1) one-dimensional chain structure consisting of Keggin polyoxotungstate and copper(II)-EDTA complex; (2) Two-dimensional layer architecture assembled by the one-dimensional chain structure and sodium linker. The results of magnetic measurements in the temperature range 300-2 K indicated the existence of ferromagnetic exchange interactions between the Cu{sup II} ions for both compounds. In addition, TGA analysis, IR spectra, and electrochemical properties were also investigated to well characterize these two compounds. - Graphical abstract: Two new polyoxometalate-based hybrids, Na{sub 4}(OH)[Cu{sub 2}(EDTA)PW{sub 12}O{sub 40}].17H{sub 2}O (1) and Na{sub 4}[Cu{sub 2}(EDTA)SiW{sub 12}O{sub 40}].19H{sub 2}O (2), have been synthesized and structurally characterized, which consist of one-dimensional chain structure assembled by Keggin polyoxotungstate and copper(II)-EDTA complex. The chains are further connected to form two-dimensional layer architecture assembled by the one-dimensional chain structure and sodium linker.

Liu Hong [Key Laboratory of Polyoxometalates Science of Ministry of Education, College of Chemistry, Northeast Normal University, Changchun 130024 (China); College of Chemistry and Medicine, Jiamusi University, Jiamusi 154007 (China); Xu Lin [Key Laboratory of Polyoxometalates Science of Ministry of Education, College of Chemistry, Northeast Normal University, Changchun 130024 (China)], E-mail: linxu@nenu.edu.cn; Gao Guanggang [Key Laboratory of Polyoxometalates Science of Ministry of Education, College of Chemistry, Northeast Normal University, Changchun 130024 (China); Li Fengyan [Key Laboratory of Polyoxometalates Science of Ministry of Education, College of Chemistry, Northeast Normal University, Changchun 130024 (China); Yang Yanyan [Key Laboratory of Polyoxometalates Science of Ministry of Education, College of Chemistry, Northeast Normal University, Changchun 130024 (China); Li Zhikui [Key Laboratory of Polyoxometalates Science of Ministry of Education, College of Chemistry, Northeast Normal University, Changchun 130024 (China); Sun Yu [Key Laboratory of Polyoxometalates Science of Ministry of Education, College of Chemistry, Northeast Normal University, Changchun 130024 (China)

2007-05-15

42

Magnetic Properties of Diabase Dikes  

Microsoft Academic Search

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

D. W. Strangway

1961-01-01

43

Superconductivity and Magnetism: Materials Properties  

E-print Network

#12;#12;Superconductivity and Magnetism: Materials Properties and Developments #12;Copyright 2003 Risø National Laboratory Roskilde, Denmark ISBN 87-550-3244-3 ISSN 0907-0079 #12;Superconductivity LABORATORY ROSKILDE, DENMARK #12;Risø International Symposium on Superconductivity and Magnetism: Material

44

Modification of activation and evaluation properties of narratives by weak complex magnetic field patterns that simulate limbic burst firing.  

PubMed

In two separate experiments a total of 71 volunteers were asked to generate spontaneous narratives that were scored automatically by the Whissell Dictionary of Affect. During the narratives, weak (1 microT; 10 mG) magnetic fields were applied briefly through the temporal planes. In Experiment I, subjects who were exposed to simple sine wave or pulsed fields generated more scorable words that indicated lower activation and evaluation than sham-field conditions. In Experiment II subjects exposed to a computer-generated wave form, designed to simulate neuronal burst firing, generated narratives dominated by more pleasantness and less activation than a reference group. The possibility that this approach could be utilized to study the affective dimension of language selection was indicated. PMID:8407157

Richards, P M; Persinger, M A; Koren, S A

1993-01-01

45

Tuning the Magnetic Properties of Nanoparticles  

PubMed Central

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

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

2013-01-01

46

Synthesis, characterization and magnetic properties of transition metal salen complexes intercalated into layered MnPS 3  

Microsoft Academic Search

Three new intercalation compounds based on the cationic complexes [M(salen)]+ (M=Mn3+, Fe3+, Co3+; salen=N,N?-ethylene-bis(salicylaldimine)) and the layered MnPS3 have been synthesized and characterized by XRD, IR, TGA and elemental analysis. Compared with pure MnPS3, the lattice expansion (?d) of 9.6–9.7Å for [Fe(salen)]0.56Mn0.72PS3·0.5H2O and [Mn(salen)]0.26Mn0.87PS3·0.5H2O indicates that the guest molecular is arranged with its C2 axis in a titled way to

Xuan Zhang; Huiqiong Zhou; Xu Su; Xingguo Chen; Chuluo Yang; Jingui Qin; Makoto Inokuchi

2007-01-01

47

3D vector magnetic properties of soft magnetic composite material  

Microsoft Academic Search

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

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

2006-01-01

48

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

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

49

Synthesis, structure, and magnetic and electrochemical properties of quasi-linear and linear iron(I), cobalt(I), and nickel(I) amido complexes.  

PubMed

Three potassium crown ether salts, [K(Et2O)2(18-crown-6)][Fe{N(SiMe3)Dipp}2] (1a; Dipp = C6H3-2,6-Pr(i)2), [K(18-crown-6)][Fe{N(SiMe3)Dipp}2]·0.5PhMe (1b), and [K(18-crown-6)][M{N(SiMe3)Dipp}2] (M = Co, 2; M = Ni, 3), of the two-coordinate linear or near-linear bis-amido monoanions [M{N(SiMe3)Dipp}2](-) (M = Fe, Co, Ni) were synthesized by one-electron reduction of the neutral precursors M{N(SiMe3)Dipp}2 with KC8 in the presence of 18-crown-6. They were characterized by X-ray crystallography, UV-vis spectroscopy, cyclic voltammetry, and magnetic measurements. The anions feature lengthened M-N bonds in comparison with their neutral precursors, with slightly bent coordination (N-Fe-N = ca. 172°) for the iron(I) complex, but linear coordination for the cobalt(I) and nickel(I) complexes. Fits of the temperature dependence of ?MT of 1 and 2 reveal that the iron(I) and cobalt(I) complexes have large negative D zero-field splittings and a substantial orbital contribution to their magnetic moments with L = 2, whereas the nickel(I) complex has at most a small orbital contribution to its magnetic moment. The magnetic results have been used to propose an ordering of the 3d orbitals in each of the complexes. PMID:25119436

Lin, Chun-Yi; Fettinger, James C; Grandjean, Fernande; Long, Gary J; Power, Philip P

2014-09-01

50

Properties and biomedical applications of magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

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

Regmi, Rajesh Kumar

51

Synthesis, spectroscopic characterization and magnetic properties of homo- and heterodinuclear complexes of transition and non-transition metal ions with a new Schiff base ligand.  

PubMed

Four homodinuclear complexes of Ni(II)-Ni(II), Cu(II)-Cu(II), Co(II)-Co(II) and Co(III)-Co(II) and five heterodinuclear complexes of Co(III)-Zn(II), Co(III)-Cu(II), Co(III)-Ni(II), Cu(II)-Zn(II) and Zn(II)-Cu(II) with the octadentate Schiff base compartmental ligand 1,8-N-bis(3-carboxy)disalicylidene-3,6-diazaoctane-1,8-diamine (H4fsatrien) have been synthesized. The complexes have been characterized with the help of elemental analyses, molecular weights, molar conductances, magnetic susceptibilities and spectroscopic (UV-vis, IR, ESR) data. Cryomagnetic data also helped to elucidate the structural features of the Cu(II) complexes. PMID:18650125

Sarkar, Saikat; Biswas, Susobhan; Dey, Kamalendu

2008-12-15

52

Burnt clay magnetic properties and palaeointensity determination  

NASA Astrophysics Data System (ADS)

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

Avramova, Mariya; Lesigyarski, Deyan

2014-05-01

53

Magnetism of the oceanic crust: Evidence from ophiolite complexes  

SciTech Connect

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

Banerjee, S.K.

1980-07-10

54

A series of complexes with a [Mn 8O 8] 8+ saddle-like core: Facile synthesis, crystal structure and magnetic property  

NASA Astrophysics Data System (ADS)

Three manganese complexes formulated as [CeMn8IIIO 8(O 2CMe) 12(H 2O) 4]·4H 2O ( 1·4H 2O), [CeMn8IIIO 8(O 2CMe) 12(py) 3(H 2O)]·6.5H 2O ( 2·6.5H 2O), [CeMn8IIIO 8(O 2CMe) 12(bzd) 2(H 2O) 2]·10H 2O( 3·10H 2O) (where py = pyridine, bzd = benzimidazole), have been synthesized and characterized by elemental analysis, IR and single-crystal X-ray diffraction analyses. Complexes 1- 3 all consist of a central Ce 4+ ion surrounded by a nonplanar, saddle-like [Mn 8O 8] 8+ loop via eight ? 3sbnd O 2- ions, and peripheral ligation is provided by twelve acetate groups, four water molecules for complex 1, twelve acetate groups, three pyridines and one water molecule for complex 2, twelve acetate groups, two benzimidazoles and two water molecules for complex 3. Variable-temperature magnetic susceptibility measurements reveal the ground-state spin ( S) values of 8 for complexes 1 and 2, which are half of the analogous complex previously reported. An explanation for this difference is also included in the text.

Wang, Hui-Sheng; Ma, Cheng-Bing; Wang, Mei; Chen, Chang-Neng; Liu, Qiu-Tian

2008-03-01

55

MAGNETIC AND FLOW PROPERTIES OF HIGH MAGNETIZATION NANOFLUIDS  

Microsoft Academic Search

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

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

56

Magnetic clusters from polyoxometalate complexes  

Microsoft Academic Search

The present article highlights the increasing interest of polyoxometalates in molecular magnetism, providing at the same time a perspective of the state-of-the-art in this area. The main focus is the polyoxotungstates. The first aspect we discuss is that of the coordination chemistry of these metal–oxide ligands. We show that this chemistry leads to remarkable examples of well-insulated magnetic clusters of

Juan M. Clemente-Juan; Eugenio Coronado

1999-01-01

57

Magnetic Properties of Hematites  

NASA Astrophysics Data System (ADS)

Hysteresis loops were measured for submicron hematites with grain sizes between 0.12 and 0.52 micrometer and on 2 to 5 mm natural hematite crystals. The maximum field of 1.5 T was not sufficient to saturate the magnetization of the submicron SD hematites. Bulk coercive forces ranging from 140 to 670 mT were determined from the unsaturated loops but the coercivity spectrum extends to fields at least an order of magnitude higher. Shape and c-plane magnetocrystalline anisotropies are inadequate to explain these high coercivities. Their main source must be magnetoelastic anisotropy arising from internal stresses. Remanence ratios Mrs/M for all but one of the SD hematites ranged from 0.60 to 0.80, intermediate between the random- orientation values of 0.5-0.64 for uniaxial (magnetoelastic) anisotropy with an easy plane and 0.75-0.96 for triaxial (magnetocrystalline) anisotropy with an easy plane. Hysteresis was measured in the (0001) plane for the large single crystals. The loops closed in fields of a few hundred mT. Hc values were between 0.63 and 30 mT, an order of magnitude lower than SD values. Coercivity is determined by the motion of pinned domain walls and is much lower than in the SD case where domains must be bodily rotated. Walls are usually pinned at crystal defects such as multiple twins or dislocations. Saturation remanence ratios Mrs/Ms are 0.61-0.89, higher than for the SD hematites because measurements are made within the (0001) easy plane. Low-temperature hysteresis measurements were made on a mm-size natural hematites at selected temperatures from 300 K to 220 K. The shape of the hysteresis curves showed different features below and above the Morin transition Tm. Above Tm, the crystal has typical hematite hysteresis curves. In the vicinity of Tm, the loops were slightly constricted, indicating coexisting weakly ferromagnetic (WF) and antiferromagnetic (AF) phases with vastly different coercivities. The hysteresis effects are still observed well below Tm, although the crystal is nominally in a purely antiferromagnetic state. The observed low-temperature moment is probably due to a small fraction of spins pinned magnetoelastically by lattice defects. These spins do not participate in the general rotation from the WF c-plane to the AF c-axis on cooling through Tm of the bulk crystal.

Ozdemir, O.

2006-12-01

58

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

PubMed

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

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

2014-09-15

59

The magnetic properties of seamless steel pipe  

Microsoft Academic Search

The magnetic and metallurgical properties of seamless pipe steel have been investigated as a function of position around the pipe circumference. No changes in magnetic properties were found to be associated with the four cycle spiral variations in pipe wall thickness introduced during forging. A weaker single cycle thickness variation was accompanied by a change both in magnetic properties and

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

1987-01-01

60

Syntheses, crystal structures and magnetic properties of three new binuclear Ni(II) complexes derived from tripodal tetradentate (N 4) ligands  

Microsoft Academic Search

Three new binuclear Ni(II) complexes [{Ni(L22py)Cl}2](ClO4)2 (1), [{Ni(L23py)Cl}2](ClO4)2 (2), and [{Ni(L33py)Cl}2](ClO4)2 (3), {L22py=N-(2-pyridylmethyl)-N-(2-aminoethyl)-1,2-diaminoethane, L23py=N-(2-pyridylmethyl)-N-(2-aminoethyl)-1,3-diaminopropane, L33py=N-(2-pyridylmethyl)-N-(3-aminopropyl)-1,3-diaminopropane} have been synthesized. Single crystal X-ray structure analysis showed that in each complex two distorted octahedral Ni(II) ions are bridged asymmetrically by a pair of chloride anions. Variable temperature magnetic susceptibility measurements of 1 and 3 revealed dominant ferromagnetic exchange interactions.

Sadegh Salehzadeh; Reza Golbedaghi; Ian. S. Tidmarsh; Lorenzo Sorace; Harry Adams; Michael D. Ward

2009-01-01

61

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

NASA Astrophysics Data System (ADS)

Two novel heterotrinuclear Cu(II)-M(II)-Cu(II) (M=Ni and Mn) complexes, [Ni(H 2O) 4(CuL) 2]·7H 2O ( 1), [Mn(H 2O) 4(CuL) 2]·8H 2O ( 2), have been obtained by the self-assembly of the mononuclear tripeptide Schiff base complexes [CuL] - with bivalent metal ion M 2+, where H 3L= N-salicylideneglycylglycylglycine. Single crystal X-ray diffraction experiments indicate that the structures both 1 and 2, are made up of centrosymmetric trinuclear units with the M atom lying on an inversion center, formed the 1D supramolecular chain structures via hydrogen bondings and M⋯O weak interactions. The magnetic susceptibility data (2-300 K) revealed antiferromagnetic interactions between copper(II) ions and the central metal. The magnetic susceptibility data were quantitatively analyzed using the theoretical expressions deduced from the spin Hamiltonian for a symmetrical three-spin system Hˆ=-2JS(S+S) to give the coupling parameters JCuNi=-0.46 cm -1 and JCuMn=-0.15 cm -1.

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

2005-09-01

62

Growth, magnetic, and transport properties of magnetic superlattices.  

E-print Network

??Three series of epitaxial magnetic superlattices are grown on GaAs substrates: cobalt-gold, cobalt-copper, and cobalt-chromium. The interrelationship between crystal microstructure, magnetic, and magnetotransport properties is… (more)

Vavra, William Paul

1992-01-01

63

Magnetic properties of nanoscale conductors  

NASA Astrophysics Data System (ADS)

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

Adam, Shaffique

64

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

65

Magnetic properties of the Kondo lattice  

Microsoft Academic Search

We review the magnetic properties of the Konso lattice model using the functional integral technique: we discuss the magnetic and non-magnetic phases, and some properties of these phases. Comparison with other calculations is also made. Finally some open questions are discussed.

C. Lacroix

1991-01-01

66

Faraday rotation and magnetic properties of erbium gallium gallate under high magnetic field  

NASA Astrophysics Data System (ADS)

Magnetization (M) and Faraday rotation (FR) have been measured in Er3Ga5O12 single crystals in the 4.2-300 K temperature range under high dc magnetic field up to 300 kOe. Experimental data are reported for H applied parallel to the [111] and [100] directions at 633 and 550 nm wavelength. A strong anisotropy of both magneto-optical and magnetic properties is observed. At low temperature, FR and M are proportional only when the magnetization is weak (small magnetic field). In medium and high magnetic field, complex relationships between M and FR are found. The magnetization cannot account for the whole Faraday rotation anisotropy. These data are discussed taking into account the magnetic and magneto-optical properties of the isomorphous erbium iron garnet ferrite.

Guillot, M.; Schmiedel, T.; Xu, You

1998-06-01

67

Modeling Magnetic Properties in EZTB  

NASA Technical Reports Server (NTRS)

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

Lee, Seungwon; vonAllmen, Paul

2007-01-01

68

Magnetic properties in graphene-graphane superlattices  

E-print Network

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

Lee, Joo-Hyoung

69

Synthesis, structure, magnetism, and spectroscopic properties of heterobinuclear copper(II)-zinc(II) complexes and their copper(II)-copper(II) analogues in asymmetric ligand environments.  

PubMed

Heterobinuclear copper(II)-zinc(II) complexes and their homobinuclear dicopper(II) counterparts (1-4) of two asymmetric ligands (H2L1 and H2L2), based on 2-aminocyclopent-1-ene-1-dithiocarboxylate, are reported. The ligands are capable of providing both donor set and coordination number asymmetry in tandem. Metal centers in these complexes are connected by a micro-alkoxo and a bridging pyrazolate moiety, as confirmed by X-ray structure analyses of 1, 3, and 4. The Cu(1) site in the dicopper complex (1) is square planar and so are the copper sites in the Cu-Zn complexes 3 and 4. The pentacoordinated Zn sites in the latter complexes have distorted TBP geometry (tau = 0.74), while the corresponding Cu site in 1 has a highly distorted square pyramidal structure (tau = 0.54). The Cu...Zn separations in 3 and 4 are 3.3782 and 3.3403 angstroms, respectively, while the Cu...Cu distance in 1 is 3.3687 angstroms. The dicopper complexes are EPR silent at 77 K, in which the copper(II) centers are coupled by strong antiferromagnetic coupling (J = ca. -290 cm(-1)) as confirmed by variable-temperature (4-300 K) magnetic measurements. These compounds (1 and 2) undergo two one-electron reductions and a single step two-electron oxidation at ca. -0.26, -1.40, and 1.0 V vs Ag/AgCl reference, respectively, as indicated by cyclic and differential pulse voltammetry done at subambient temperatures. EPR spectra of 3 and 4 display axial anisotropy at 77 K with the gperpendicular region being split into multiple lines due to N-superhyperfine coupling (AN = 15.3 x 10(-4) cm(-1)). The observed trend in the spin-Hamiltonian parameters, gparallel > gperpendicular > 2.04 and |Aperpendicular| < |Aparallel| approximately (120-150) x 10(-4) cm(-1), indicates a d(x2-y2)-based ground state with tetragonal site symmetry for the Cu(II) center in these molecules. PMID:15360251

Ghosh, Dipesh; Kundu, Nabanita; Maity, Goutam; Choi, Ki-Young; Caneschi, Andrea; Endo, Akira; Chaudhury, Muktimoy

2004-09-20

70

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

PubMed

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

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

2014-01-01

71

Fractal properties of solar magnetic fields  

Microsoft Academic Search

We study the spatial properties of solar magnetic fields using data from the Solar Vector Magnetograph of the Marshall Space\\u000a Flight Center (MSFC) (FeI 5250.2 Å) and SOHO\\/MDI longitudinal magnetic field measurements (Ni 6767.8 Å) (96-min full-disk\\u000a maps). Our study is focused on two objects: the fractal properties of sunspots and the fractal properties of the spatial magnetic\\u000a field distribution

B. A. Ioshpa; V. N. Obridko; E. A. Rudenchik

2008-01-01

72

Fractal properties of solar magnetic fields  

Microsoft Academic Search

We study the spatial properties of solar magnetic fields using data from the Solar Vector Magnetograph of the Marshall Space Flight Center (MSFC) (FeI 5250.2 Å) and SOHO\\/MDI longitudinal magnetic field measurements (Ni 6767.8 Å) (96-min full-disk maps). Our study is focused on two objects: the fractal properties of sunspots and the fractal properties of the spatial magnetic field distribution

B. A. Ioshpa; V. N. Obridko; E. A. Rudenchik

2008-01-01

73

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

74

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

75

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

76

Depth profiling of interfacial spin complexities in magnetic heterostructures  

NASA Astrophysics Data System (ADS)

Attentively restrained interfaces or superlattices between two materials can lead to emergent functionalities not shown by either constituents in their bulk form. Direct quantitative investigation of spatio-temporal correlations of magnetic and electronic properties of such interfaces is crucial in controlling and tailoring the close proximity of competing energy landscape that naturally exist in these systems. Due to the smallness and buried nature of the magnetization, characterizing these materials at the appropriate length scale is of considerable challenge. In this talk I will give examples from a variety of systems where the unique sensitivity of soft x-ray beams in reflection geometry have been exploited to obtain a quantitative description of the complex magneto-chemical depth profile across the interface between ferromagnetic (F) and antiferromagnetic (AF) thin films. In exchanges bias Co/FeF2 heterostructures we have found antiferromagnetic coupling across the interface with the net magnetization having a twisted ``fan-like'' structure near the F/AF interface. For Py/CoO we observed a redox reaction driven novel interfacial layer that has magnetic properties very different from bulk. We found that 10% of the net spins in this layer get pinned antiparallel to the cooling magnetic field at low temperatures. In complex oxide BiFeO3-La0.7Sr0.3MnO3 we have obtained direct experimental evidence of transitory layers, ionic rearrangements and depleted magnetism at the BiFeO3-La0.7Sr0.3MnO3 interface. Our examples show that interface-selective probing of magnetism in thin film heterostructures can provide vital understanding needed for rational design of future nanoelectronic devices.

Roy, Sujoy

2013-03-01

77

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

78

Inverse problem in archeological magnetic surveys using complex wavelet transform.  

NASA Astrophysics Data System (ADS)

The wavelet transform applied to potential fields (electric, magnetic, or gravimetric, ...) has been now used from several years in geophysical applications, in particular to define the depth of potentiel sources verifying Poisson equation and responsible for potential anomalies measured at the ground surface. The complex continuous wavelet transform (CCWT) has been described, but the phase has not yet been exploited. (For these kinds of problem we construct a complex analyzing wavelet by Hilbert transforms of the Poisson or derivative of the Poisson wavelet which is real by definition). We show, here, that the phase of the CCWT provides useful information on the geometric and total magnetic inclination of the potential sources, as the modulus allows to characterize their depth and heterogenety degree. Regarding the properties of the phase compared to the modulus, it is more stable in presence of noise and we can defined it, independantly of the low level of energy of the signal. In this sense, information carried by the phase is more efficient to detect small objects or to separate close sources. We have applied a multi-scale analysis on magnetic measurements providing from a cesium magnetometer on the Fox-Amphoux site (France), to detect and localize buried structures like antik ovens. Conjointly, a rock magnetic study including susceptibility and magnetisations (induced or remanent) measurements give a better constrain on the magnetic parameters we want to extract.

Saracco, G.; Moreau, F.; Mathe, P. E.; Hermitte, D.

2003-04-01

79

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

SciTech Connect

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

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

2013-08-15

80

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

81

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

82

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

83

The magnetic properties of seamless steel pipe  

NASA Astrophysics Data System (ADS)

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

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

1987-03-01

84

Magnetic and optoelectronic properties of gold nanocluster-thiophene assembly.  

PubMed

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

Qin, Wei; Lohrman, Jessica; Ren, Shenqiang

2014-07-01

85

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

PubMed

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

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

2014-03-01

86

Topological Constraints on the Relaxation of Complex Magnetic Fields  

E-print Network

Newly emerging magnetic flux can show a complicated linked or interwoven topology of the magnetic field. The complexity of this linkage or knottedness of magnetic flux is related to the free energy stored in the magnetic field. Magnetic reconnection provides a process to release this energy on the time scale of the dynamics. At the same time it approximately conserves the total magnetic helicity. Therefore the conservation of total magnetic helicity is a crucial constraint for the relaxation of complex magnetic fields. However, the total magnetic helicity is only the first, most elementary, quantity of an infinite series of topological invariants of the magnetic field. All these invariants are strictly conserved in ideal magnetohydrodynamics. As an example a preliminary set of these invariants is derived. The relevance of these higher order invariants for the final state of relaxation under magnetic reconnection and their implications for the release of magnetic energy are discussed.

Gunnar Hornig

1999-09-27

87

Ordered magnetic nanostructures: fabrication and properties  

Microsoft Academic Search

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

J. I Mart??n; J. Nogués; Kai Liu; J. L Vicent; Ivan K Schuller

2003-01-01

88

MAGNETIC PROPERTIES OF DYSPROSIUM SINGLE CRYSTALS  

Microsoft Academic Search

Single crystals of metallic dysprosium have been grown by the Bridgman ; method and their magnetic properties have been determined in different ; crystallographic directions of the hexagonal close-packed structure. Below the ; Neel point of 178.5 deg K the individual magnetic moments are aligned ; perpendicular to the c\\/sub o\\/ axis. The moments are aligned in an ; antiferromagnetic

D. R. Behrendt; S. Legvold; F. H. Speddin

1958-01-01

89

Magnetic properties of thin-film Co/Fe/Ni magnetic systems  

NASA Astrophysics Data System (ADS)

The magnetic properties of Co/Fe/Ni thin-film structures grown by magnetron sputtering have been studied using magnetooptical techniques. The results of x-ray diffraction measurements showed that all samples possessed a nanocrystalline structure. The magnetization curves and hysteresis loops were measured using the equatorial Kerr effect for two orientations of the external magnetic field. It is established that the Co/Fe/Ni thinfilm structures exhibit a planar magnetic anisotropy. The magnetic behavior of each layer in the initial inhomogeneous Co/Fe/Ni structure is substantially influenced by stray fields of the adjacent layers. This circumstance accounts for the complex shapes of hysteresis loops. The annealing in vacuum at T = 500°C renders Co/Fe/Ni thin-film structures magnetically hard compared to the initial state. The experimental results are explained by certain features of the microstructure of samples.

Shalygina, E. E.; Perepelova, E. V.; Kozlovski?, L. V.; Tamanis, E.; Mukasheva, M. A.; Shalygin, A. N.

2007-06-01

90

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

PubMed

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

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

2014-02-28

91

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

PubMed Central

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

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

2013-01-01

92

Topological properties and dynamics of magnetic skyrmions.  

PubMed

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

Nagaosa, Naoto; Tokura, Yoshinori

2013-12-01

93

Magnetic properties of ZnO-based diluted magnetic semiconductors  

Microsoft Academic Search

We report a study of the magnetic properties of transition-metal doped Zn1?xTMxO (TM=Mn, Co, Fe). Polycrystalline powder samples were synthesized by both solid-state and liquid-phase reactions. From the Curie–Weiss behavior of susceptibility at high temperatures, it was found that the TM–TM interaction is dominated by antiferromagnetic coupling with effective nearest-neighbor exchange constants J=?90 to ?30 K. The magnetization data measured

S. W. Yoon; S.-B. Cho; S. C. We; B. J. Suh; H. K. Song; Y. J. Shin

2003-01-01

94

Magnetic properties of ZnO-based diluted magnetic semiconductors  

Microsoft Academic Search

We report a study of the magnetic properties of transition-metal doped Zn1-xTMxO (TM=Mn, Co, Fe). Polycrystalline powder samples were synthesized by both solid-state and liquid-phase reactions. From the Curie-Weiss behavior of susceptibility at high temperatures, it was found that the TM-TM interaction is dominated by antiferromagnetic coupling with effective nearest-neighbor exchange constants J=-90 to -30 K. The magnetization data measured

S. W. Yoon; S.-B. Cho; S. C. We; B. J. Suh; H. K. Song; Y. J. Shin

2003-01-01

95

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

96

Magnetotransport Properties of Magnetic Oxides  

NASA Astrophysics Data System (ADS)

Hybrid spintronic devices require high Curie temperature ferromagnets with a large transport spin polarization. It has been predicted that efficient spin injection is facilitated by matching the conductance of the ferromagnet to that of the semiconductor and in this respect dilute magnetic semiconductors look to be more attractive for application. Oxide dilute magnetic semiconductors are the only class to date that may offer Curie Temperatures above 300K. Here we review the effect of chemical substitution and/or growth parameters on the magnetic, magnetotransport and spin polarisation of charge carriers of a range of functional ferromagnetic oxides, such as Fe3O4, Nd2Mo2O7, CoxTi1-xO2 and CoxZn1-xO.

Branford, Will; Liu, Ying Lin; Parames, Maria Luisa; Morrison, Kelly

2005-03-01

97

MICRODYNAMICS OF MAGNETIC PARTICLES DISPERSED IN COMPLEX MEDIA  

E-print Network

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

Paris-Sud XI, Université de

98

Crystal field and magnetic properties  

NASA Technical Reports Server (NTRS)

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

Flood, D. J.

1977-01-01

99

Spin ground state and magnetic properties of cobalt(II): relativistic DFT calculations guided by EPR measurements of bis(2,4-acetylacetonate)cobalt(II)-based complexes.  

PubMed

The spin ground state of the core ion and structure of the bis(2,4-acetylacetonate)cobalt(II) model complex and its synthetic aqua and ethanol derivatives, Co(acac)(2)L(n), (L = EtOH, H(2)O), were examined by means of density functional theory (DFT) calculations supported by electron paramagnetic resonance (EPR) measurements. Geometry optimizations were carried out for low-spin (doublet) and high-spin (quartet) states. For the Co(acac)(2) complex two possible conformations, a square-planar and a tetrahedral one, were taken into account. For all structures relative energies were calculated with both "pure" and hybrid functionals. The calculated data were complemented with the results of the EPR investigations carried out at liquid helium temperature, allowing for definite assignment of the high-spin state for the Co(acac)(2)(EtOH)(2) complex. However, because of the unresolved spectral features, only effective g-values could be assessed, whereas the zero-field splitting parameters (ZFS) were calculated by means of the spin-orbit mean field (SOMF) relativistic DFT method for which direct spin-spin (SS) and spin-orbit coupling (SOC) contributions were quantified. PMID:21351791

Pietrzyk, Piotr; Srebro, Monika; Rado?, Mariusz; Sojka, Zbigniew; Michalak, Artur

2011-03-24

100

Soft magnetic thin films: influence of annealing on magnetic properties  

NASA Astrophysics Data System (ADS)

Soft magnetic materials are currently used in a variety of applications in electrical machines, sensors and elements of devices. If prepared in thin film form, they can be applied to micro- and nano-patterned devices. However, with respect to ribbons and bulk materials, thin films of the same composition usually display worse soft magnetic properties, thus requiring suitable solutions to restore high permeability and low coercivity. In this review, the magnetic properties of thin films prepared by sputtering are presented. Several compositions of soft magnetic materials are investigated, including Co-Fe-Si-B, Fe-Cu-Nb-Si-B, Fe-Si-B, Fe-Co-Nb-Si-P-B, Fe-Zr-Nb-Cu-B. Their amorphous-to-crystallization processes are studied by means of furnace annealing and Joule heating. Hysteresis loops and magnetic domain imaging, together with structural techniques, are used to follow the effects of annealing, which include stress relaxation and crystallization. The effects of magnetic field annealing are investigated and discussed.

Coïsson, Marco; Barrera, Gabriele; Celegato, Federica; Tiberto, Paola; Vinai, Franco

2012-05-01

101

Ordered Magnetic Nanostructures. Fabrication and Properties  

Microsoft Academic Search

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

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

2003-01-01

102

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

103

Magnetic properties of epitaxial ferrite multilayer films  

NASA Astrophysics Data System (ADS)

We have fabricated and studied the structure and magnetic properties of high quality single crystalline (Mn,Zn)Fe2O4, NiFe2O4, and CoFe2O4 films. Although (Mn,Zn)Fe2O4 and NiFe2O4 films grown directly on SrTiO3 and MgAl2O4 show mediocre structural and magnetic properties, these same films grown on SrTiO3 and MgAl2O4 buffered with CoCr2O4 or NiMn2O4 exhibit excellent crystallinity and bulk saturation magnetization values, thus indicating the importance of lattice match and structural similarity between the film and the underlying layer. X ray, Rutherford backscattering spectroscopy, atomic force microscopy, and transmission electron microscopy analysis provide a consistent picture of the structural properties of these ferrite films.

Suzuki, Y.; van Dover, R. B.; Gyorgy, E. M.; Phillips, Julia M.; Korenivski, V.; Werder, D. J.; Chen, C. H.; Felder, R. J.; Cava, R. J.; Krajewski, J. J.; Peck, W. F., Jr.

1996-04-01

104

Method for Measuring the Magnetic Properties of High-Density Magnetic Composites Under Compressive Stress  

Microsoft Academic Search

When using a powder magnetic core fabricated from iron powder coated with an insulator in motors, reactors, etc., the effect of stress on its magnetic properties should be considered. In this paper, a system for measuring the magnetic properties of a powder magnetic core under compressive stress was developed and applied to a powder magnetic core, namely a high-density magnetic

N. Takahashi; T. Imahashi; M. Nakano; D. Miyagi; T. Arakawa; H. Nakai; S. Tajima

2007-01-01

105

Magnetic properties of magnetoactive spin clusters  

SciTech Connect

A simple model is proposed for describing magnetic properties of magnetoactive nanoclusters, which permits exact analytic solution. Exact expressions are obtained for thermodynamic characteristics of the model, which hold in the entire range of temperatures, magnetic fields, and interaction parameters. It is found that in the case of easy-axis anisotropy, the field dependence of magnetization of a nanocluster consisting of N particles with a spin of 1/2 has [N/2] fractional plateaus ([ Horizontal-Ellipsis ] is the integer part) corresponding to polarized phases with ruptures singlet pairs. A nonmonotonic behavior observed for the magnetic susceptibility of an easy-plane cluster is typical of gap magnets. The spin gap between the ground state and excited states is proportional to the anisotropy parameter.

Khamzin, A. M., E-mail: airat.khamzin@rambler.ru [Kazan State Power Engineering University (Russian Federation); Nigmatullin, R. R., E-mail: nigmat@knet.ru [Kazan (Volga Region) Federal University (Russian Federation)

2010-01-15

106

Magnetic circular dichroism of porphyrin lanthanide M3+ complexes.  

PubMed

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

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

2014-10-01

107

Co(II) halide complexes with 2-amino-3-methylpyridinium and 2-amino-5-methylpyridinium: synthesis, crystal structures, and magnetic properties  

Microsoft Academic Search

Reaction of CoX2 · nH2O with either 2-amino-3-methylpyridine (3-MAP) or 2-amino-5-methylpyridine (5-MAP) in aqueous acid gave complexes, (3-MAPH)2CoX4 or (5-MAPH)2CoX4 (H2O)n [n = 0,1; X = Cl, Br; 3-MAPH = 2-amino-3-methylpyridinium, 5-MAPH = 2-amino-5-methylpyridinium]. The 3-MAPH salts are formed in the triclinic crystal system while the 5-MAPH salts are formed in the monoclinic crystal system. Three of these compounds exhibit

David J. Carnevale; Christopher P. Landee; Mark M. Turnbull; Mon Winn; Fan Xiao

2010-01-01

108

Domain structures in complex 3D magnetic fields  

NASA Astrophysics Data System (ADS)

The numerous magnetic fragments that populate the mixed-polarity, quiet-Sun photosphere give rise to many interesting topological features in the corona. In light of this, much recent work has gone into classifying the configurations that arise from simple, point-source potential-field models in efforts to determine the nature of the quiet-Sun magnetic field. These studies have ranged from systematic and detailed examinations of magnetic fields arising from only a handful of sources, involving classifying the configurations that arise (and how some states may bifurcate into other states), to statistical studies of the overall properties of fields arising from hundreds of magnetic sources. Such studies have greatly increased our understanding of what we might expect the magnetic field over the quiet Sun to behave like; the purpose of the study presented here is to extend this understanding further by examining the structure of the individual domains (the regions in space through which pairs of opposite-polarity sources are connected). In particular, the features of lesser-known domain structures that are absent from fields arising from only a few sources and overlooked by sweeping statistical studies are documented. In spite of the incredible complexity of the coronal field, previous studies have shown that there are only two types of building block in a potential field arising from coplanar point sources: namely, an isolated dome, bounded by a single unbroken separatrix surface, and a separator-ring domain, engirdled by a ring of separators. However, it is demonstrated here how both isolated domains and separator-ring domains may be categorised further depending upon their particular geometrical and topological traits. As many models predict coronal heating at topologically distinct features in magnetic fields such as null points, separators and separatrices, for any such models to be applied to general fields would require a scheme for identifying which topological features are related to a given domain. The study here explores some of the issues that would need to be taken into account by such a scheme, and in particular the problems associated with trying to deduce the properties of a general magnetic field from knowledge of domain footprints alone. Animated 3D-rotational views of some of the figures in this manuscript may be viewed in AVI, MPEG and animated-GIF formats by visiting http://www-solar.mcs.st-and.ac.uk/robertc/animations/blocks.html and following the desired link.

Close, R. M.; Parnell, C. E.; Priest, E. R.

109

Synthesis, structure, and magnetic properties of three 1D chain complexes based on high-spin metal-cyanide clusters: [Mn(III)6M(III)] (M = Cr, Fe, Co).  

PubMed

On the basis of high-spin metal-cyanide clusters of Mn(III)(6)M(III) (M = Cr, Fe, Co), three one-dimensional (1D) chain complexes, [Mn(salen)](6)[Cr(CN)(6)](2)·6CH(3)OH·H(2)O (1), [Mn(5-CH(3))salen)](6)[Fe(CN)(6)](2)·2CH(3)CN·10H(2)O (2), and [Mn(5-CH(3))salen)](6)[Co(CN)(6)](2)·2CH(3)CN·10H(2)O (3) [salen = N,N'-ethylenebis(salicylideneiminato) dianion], have been synthesized and characterized structurally as well as magnetically. Complexes 2 and 3 are isomorphic but slightly different from complex 1. All three complexes contain a 1D chain structure which is comprised of alternating high-spin metal-cyanide clusters of [Mn(6)M](3+) and a bridging group [M(CN)(6)](3-) in the trans mode. Furthermore, the three complexes all exhibit extended 3D supramolecular networks originating from short intermolecular contacts. Magnetic investigation indicates that the coupling mechanisms are intrachain antiferromagnetic interactions for 1 and ferromagnetic interactions for 2, respectively. Complex 3 is a magnetic dilute system due to the diamagnetic nature of Co(III). Further magnetic investigations show that complexes 1 and 2 are dominated by the 3D antiferromagnetic ordering with T(N) = 7.2 K for 1 and 9.5 K for 2. It is worth noting that the weak frequency-dependent phenomenon of AC susceptibilities was observed in the low-temperature region in both 1 and 2, suggesting the presence of slow magnetic relaxations. PMID:21718032

Zhou, Hong-Bo; Wang, Jun; Wang, Hui-Sheng; Xu, Yong-Lu; Song, Xiao-Jiao; Song, You; You, Xiao-Zeng

2011-08-01

110

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

111

Magnetic Properties of Ubiquitous yet Underrated Antiferromagnetic Nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

112

Magnetic dipole discharges. I. Basic properties  

NASA Astrophysics Data System (ADS)

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

Stenzel, R. L.; Urrutia, J. M.; Teodorescu-Soare, C. T.; Ionita, C.; Schrittwieser, R.

2013-08-01

113

Magnetic dipole discharges. I. Basic properties  

SciTech Connect

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

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

2013-08-15

114

Magnetic properties of heterotrophic bacteria (abstract)  

NASA Astrophysics Data System (ADS)

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

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

1994-05-01

115

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

116

Magnetic Properties of Mesoporous and Nano-particulate Metal Oxides   

E-print Network

The magnetic properties of the first row transition metal oxides are wide and varied and have been studied extensively since the 1930’s. Observations that the magnetic properties of these material types change with the ...

Hill, Adrian H

2009-01-01

117

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

PubMed

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

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

2014-06-11

118

Classification of Complex Networks Based on Topological Properties  

E-print Network

apply standard data mining tools to analyze these data. A cluster analysis reveals it is possible. Keywords--Complex Networks; Topological Measures, Properties Comparison, Cluster Analysis. I. INTRODUCTIONClassification of Complex Networks Based on Topological Properties Burcu Kantarci and Vincent

Paris-Sud XI, Université de

119

Tuning electronic and magnetic properties of silicene with magnetic superhalogens.  

PubMed

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

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

2014-11-14

120

Magnetic properties in graphene-graphane superlattices  

NASA Astrophysics Data System (ADS)

The magnetic properties of graphene-graphane superlattices with zigzag interfaces and separately varying widths are investigated by first-principles density functional calculations. It is demonstrated that magnetic states are energetically more stable than nonmagnetic ones due to the Stoner-type instability, and that antiferromagnetic spin configuration across the graphene strip is found to be the ground state, whereas the ferromagnetic ordering becomes metastable. The magnetic moments in the ferromagnetic states show a monotonic increase and saturation with the width of the graphene strip, independent of the graphane width due to the ?-character of the spin densities. These findings point toward an alternative route for graphene-based applications without requiring physical cutting as in graphene nanoribbons.

Lee, Joo-Hyoung; Grossman, Jeffrey C.

2010-09-01

121

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

122

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

PubMed

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

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

2015-01-20

123

Perovskite oxide superlattices: Magnetotransport and magnetic properties  

Microsoft Academic Search

We have fabricated perovskite superlattices consisting of two ferromagnetic metallic oxides: La0.67Ca0.33MnO3 (LCMO) and SrRuO3 (SRO). We have investigated the magnetotransport and magnetic properties of a series of samples, in which the layer thickness of LCMO is fixed and that of SRO varied from 0 to 20 unit cells. The magnetoresistance ratio in a superlattice can be increased by a

G. Q. Gong; A. Gupta; Gang Xiao; P. Lecoeur; T. R. McGuire

1996-01-01

124

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

125

The complexity of the certification of properties of Stable Marriage  

E-print Network

The complexity of the certification of properties of Stable Marriage Daniel J. Dougherty bounds on the certificate complexity of some problems concerning stable marriage, answering a question of Gusfield and Irving. Key words: stable marriage, combinatorial problems, computational complexity

Dougherty, Daniel J.

126

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

NASA Astrophysics Data System (ADS)

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

Chandra, Sulekh; Gupta, Nidhi; Gupta, Rachna

2006-03-01

127

Growth, magnetic, and transport properties of magnetic superlattices  

SciTech Connect

Three series of epitaxial magnetic superlattices are grown on GaAs substrates: cobalt-gold, cobalt-copper, and cobalt-chromium. The interrelationship between crystal microstructure, magnetic, and magnetotransport properties is explored with reflection high-energy electron diffraction (RHEED), magnetometry, Hall effect, and magnetoresistance. Perpendicular anisotropy is observed in the cobalt-gold and cobalt-copper superlattices with cobalt thickness less than 18[angstrom] and 9[angstrom], respectively. This anisotropy is found to significantly enhance magnetoresistance at cryogenic temperatures. A calculation of the magnetoelastic anisotropy due to epitaxial strain is presented, and when added to the magnetocrystalline and shape anisotropies, quantitatively accounts for the experimental data. In the cobalt-chromium superlattices a structural transition in the chromium layers from close-packed to body centered cubic in the Kurdjumov-Sachs and Nishiyama-Wasserman orientations is observed in real-time with a charge coupled device RHEED detection system.

Vavra, W.P.

1992-01-01

128

Magnetic properties of Cr Fe Mn alloys  

NASA Astrophysics Data System (ADS)

The magnetic behaviour of a Cr 80-xFe 20Mn x 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 phase regions and a spin-glass (SG) region at the lowest temperatures. Phase transition temperatures amongst these different magnetic phases could be identified from well-defined anomalies of magnetic origin that are displayed by graphs of the above-mentioned physical properties as a function of temperature. The time relaxation of the thermoremanent, isothermal remanent and field-cooled magnetizations below and above the SG freezing temperature show unusual aspects. These relaxations do not follow the usual superposition principle that is expected for typical SG materials. Negative giant magetoresistance (GMR) is observed in the alloys at 4 K. The GMR initially increases sharply on increasing the Mn content in the alloy system, followed by a tendency towards a saturation negative value for concentrations of more than about 10 at% Mn. Low-temperature plots of C p/ T vs. T2, where C p is the specific heat, present anomalous behaviour for alloys with x=2, 10 and 22. For x=2 the plot shows an upturn at the lowest temperatures that changes over to a prominent downturn for x=10 and 22. This behaviour is attributed to Fe concentration fluctuations in the alloys, confirming the theoretical model of Matthews.

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

2009-01-01

129

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

NASA Astrophysics Data System (ADS)

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

Cornelison, Steven G.

1982-03-01

130

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

131

Electron spin resonance and magnetic studies on some copper(II) azobarbituric and azothiobarbituric acid complexes.  

PubMed

Electron spin resonance and magnetic susceptibility on some copper(II) complexes prepared from phenylazobarbituric and phenylazothiobarbituric acid compounds containing 2,5-dichloro and 2,5-dimethyl groups were discussed. The thio complexes exist in dimer-monomer mixture. The corresponding copper(II) complexes of the oxygen homologous failed to exhibit association. Singlet-triplet separation values equal to -321 and -263 cm(-1) for the 2,5-dimethyl and 2,5-dichloro complexes, respectively, of the thio series. An empirical measure of the amount of tetrahedral deformation based on the values of g||/A|| assigned the square-planar geometry of the dimethyl-oxygen complex while the other complexes are with tetrahedral planar geometries. The effect of temperature on the ESR data was discussed. The diamagnetic properties of the complexes derived from 2,5-dichloro and 2,5-dimethyl thiobarbituric acid suggested the formation of Cu(I) complexes. PMID:15683807

Masoud, M S; Khalil, E A; Hafez, A M; El-Husseiny, A F

2005-03-01

132

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

NASA Astrophysics Data System (ADS)

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 for MF. The ferrites synthesized by the wet chemical method have different magnetic characteristics if compared to the ferrites prepared by standard ceramic methods. In this paper, the physical properties of ultrafine complex spinel-type Fe _{2}Co _{0.3}Zn _{0.6}Ca _{0.1}O_{4}, Fe _{1.9}Cd _{0.1}Mn _{0.54}Zn _{0.46}O_{4}, Fe _{2}CoO_{4} and Fe _{2}Zn _{0.6}Mn _{0.3}Ca _{0.1}O_{4} ferrite particles and MF on its base, after their special thermal treatment, are studied. Tables 1, Figs 6, Refs 8.

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

2008-03-01

133

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

134

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

PubMed

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

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

2013-12-01

135

Study of magnetic properties of magnetic force microscopy probes using micronscale current rings  

E-print Network

Study of magnetic properties of magnetic force microscopy probes using micronscale current rings, fabricated using electron-beam lithography, were used to calibrate magnetic force microscopy MFM . A MFM tip magnetic force microscopy MFM is an essential tool for characterizing magnetic ma- terials in submicron

136

Synthesis and magnetic properties of nanostructured maghemite  

SciTech Connect

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

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

1997-08-01

137

Magnetic properties of periodically organized cobalt frameworks  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

138

Magnetic properties of substituted barium ferrite powders  

SciTech Connect

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

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

1994-03-01

139

Different annealing treatments for improvement of magnetic and electrical properties of soft magnetic composites  

Microsoft Academic Search

This paper investigates the effect of two steps, annealing and magnetic annealing, on the magnetic and electrical properties of iron powder particles with high purity used in soft magnetic composite materials. It was found that at low frequencies (<10kHz) the magnetic loss in the high-temperature magnetic annealed state is smaller than that in the low-temperature magnetic, magnetic annealed and without

H. Shokrollahi; K. Janghorban

2007-01-01

140

Modeling graphene: Magnetic, transport and optical properties  

NASA Astrophysics Data System (ADS)

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

Chang, Yi Chen

141

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

142

Magnetic Properties of Rhombohedral Graphene Thin Films  

NASA Astrophysics Data System (ADS)

Ever since the fabrication of single and few layers graphene, the graphene thin films have been attracting so much attention in the field not only of low-dimensional sciences but also of nano-scale technologies due to their perfect two-dimensional network. One of fascinating issues in this carbon allotrope is the intrinsic magnetism that is inherent in their topological properties. We have demonstrated that the (0001) surfaces of graphene thin film with rhombohedral-stacked arrangement exhibit ferrimagnetic spin ordering induced by flat dispersion band associated with the peculiar surface localized electron states classified as the ``edge state'' [1]. In this work, we systematically investigate how the electronic and magnetic properties of the rhombohedral-stacked graphene thin films depend on the number of graphene layers, BN substrate, and uniaxial pressure using first-principles total-energy calculations in the framework of density functional theory [2]. [4pt] [1] M. Otani, M. Koshino, Y. Takagi, and S. Okada, Phys. Rev. B 81 (2010) 161403(R). [0pt] [2] N. T. Cuong, M. Otani, and S. Okada, Surf. Sci. (2011), doi:10.1016/j.susc.2011.10.001

Cuong Nguyen, Thanh; Otani, Minoru; Okada, Susumu

2012-02-01

143

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

PubMed

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

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

2013-04-15

144

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

SciTech Connect

The Nd-Fe-B bulk magnets with a slab shape of 0.9 x 4 x 15 mm{sup 3} were prepared by injection casting into a copper mold. The effects of applying a magnetic field during the casting process on the magnetic properties and microstructure of Nd{sub 9.5}Fe{sub 71.5}Ti{sub 2.5}Zr{sub 0.5}Cr{sub 1}B{sub 14.5}C{sub 0.5} alloy have been studied. The results show that the sample cast with magnetic field has a stronger (00L) texture of Nd{sub 2}Fe{sub 14}B phase with the c-axis perpendicular to the slab plane than the sample cast without magnetic field. The intensity of the texture weakens from surface to inner region of the bulk magnets. Applying a magnetic field during the casting process is helpful to refine the grain size effectively. As a result, the magnetic properties are improved from B{sub r} = 5.8 kG, {sub i}H{sub c} = 6.5 kOe, and (BH){sub max} = 5.9 MGOe for thesample cast without magnetic field to B{sub r} = 6.1 kG, {sub i}H{sub c} = 10.3 kOe, and (BH){sub max} = 7.3 MGOe for the sample cast with a 3.7 kOe magnetic field.

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

2011-04-01

145

Electron holography and magnetic properties of exsolved synthetic titanomagnetites  

E-print Network

Electron holography and magnetic properties of exsolved synthetic titanomagnetites Church, N S nc-ulvospinel assemblages. These exsolved samples were examined using electron holography to quantitatively measure

Dunin-Borkowski, Rafal E.

146

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

SciTech Connect

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

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

2013-03-31

147

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

PubMed

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

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

2012-01-14

148

Magnetic Properties of the Chelyabinsk meteorite  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

149

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

Microsoft Academic Search

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

Jian Guo Zhu; YouGuang Guo

2004-01-01

150

High temperature magnetic properties of SmCo5/-Fe(Co) bulk nanocomposite magnets  

E-print Network

-compaction route. Up to 30% of the Fe soft magnetic phase has been added to the composites with grain size High temperature magnetic properties of SmCo5/-Fe(Co) bulk nanocomposite magnets Chuanbing Rong on perpendicular magnetic anisotropy of CoFeB films in MgO/Mg/CoFeB/Ta structure Appl. Phys. Lett. 101, 122414

Liu, J. Ping

151

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

E-print Network

Annealing effects on magnetic properties of silicone-coated iron-based soft magnetic composites Available online 1 October 2011 Keywords: Silicone resin Soft magnetic composites Annealing treatment Permeability a b s t r a c t This paper focuses on novel iron-based soft magnetic composites synthesis

Volinsky, Alex A.

152

2652 IEEE TRANSACTIONS ON MAGNETICS, VOL. 38, NO. 5, SEPTEMBER 2002 Interface Magnetic Properties of Epitaxial  

E-print Network

effect, and X-ray magnetic circular dichronism. The magnetic properties at room temperature were found-optical Kerr effect (MOKE), and X-ray magnetic circular dichronism (XMCD) study of the interface magnetic on InAs (100)-4 2 have been studied using low-energy electron diffraction, in situ magneto-optical Kerr

Xu, Yongbing

153

Magnetic Memory in an Isotopically Enriched and Magnetically Isolated Mononuclear Dysprosium Complex.  

PubMed

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

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

2014-12-01

154

Magnetic properties of single-crystalline Mott insulator YVO{sub 3}  

SciTech Connect

Single crystals of YVO{sub 3} were grown using the floating-zone technique. YVO{sub 3} crystallizes in the orthorhombic Pbnm structure, and the structural parameters were determined by means of neutron diffraction. Using a superconducting quantum interference device magnetometer, we have studied the magnetic properties of YVO{sub 3} along the three principal directions. Our single crystal exhibits two magnetic transitions at about 115 and 75 K. For temperatures above the magnetic ordering, almost isotropic Curie{endash}Weiss behavior is found for the magnetic susceptibility. Below the ordering, however, we find a highly anisotropic response with the {ital c} axis as the easy-magnetization direction. Both magnetic phases exhibit a weak ferromagnetic component along the {ital c} axis. A complex low-field magnetization behavior indicates that YVO{sub 3} orders ferrimagnetically for temperatures between 75 and 115 K. {copyright} {ital 1999 American Institute of Physics.}

Nakotte, H.; Laughlin, L. [Physics Department, MSC 3D, New Mexico State University, Las Cruces, New Mexico 88003 (United States)] [Physics Department, MSC 3D, New Mexico State University, Las Cruces, New Mexico 88003 (United States); Kawanaka, H. [Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba 305-8568 (Japan)] [Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba 305-8568 (Japan); Argyriou, D.N.; Sheldon, R.I. [LANSCE-12, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [LANSCE-12, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Nishihara, Y. [Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba 305-8568 (Japan)] [Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba 305-8568 (Japan)

1999-04-01

155

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

156

A new Cu–cysteamine complex: structure and optical properties  

SciTech Connect

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

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

2014-06-07

157

Physicochemical properties and antioxidant activities of luteolin-phospholipid complex.  

PubMed

A luteolin and phospholipid complex was prepared to improve the lipophilic properties of luteolin. The physicochemical properties of the complex were analyzed by ultraviolet-visible spectrometry (UV), infrared spectrometry (IR), X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). The results showed that luteolin and phospholipid in the complex were joined by non-covalent-bonds and did not form a new compound. It was found that the complex was an effective scavenger of DPPH radicals, with an IC(50) value of 28.33 microg/mL. In the Rancimat antioxidant test using lard oil as substrate, the complex also showed the strong antioxidant activity. PMID:19783938

Xu, Keyong; Liu, Benguo; Ma, Yuxiang; Du, Jiquan; Li, Guanglei; Gao, Han; Zhang, Yuan; Ning, Zhengxiang

2009-01-01

158

Ligands effects on the magnetic anisotropy of tetrahedral cobalt complexes.  

PubMed

The effect of ligands with heavy donor atoms on the magnetic anisotropy of the pseudo-tetrahedral cobalt complexes, Co(quinoline)2I2 (1) and Co(EPh3)2I2 (2-3) (E = P, As) has been investigated. The axial zero-field splitting parameter D was found to vary from +9.2 cm(-1) in 1 to -36.9 cm(-1) in 2 and -74.7 cm(-1) in 3. Compounds 2 and 3 exhibit slow relaxation of the magnetization up to 4 K under an applied dc field, indicating SMM behavior. PMID:25183324

Saber, Mohamed R; Dunbar, Kim R

2014-10-21

159

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

160

Synthesis, characterization, in vitro cytotoxicity, and apoptosis-inducing properties of ruthenium(II) complexes.  

PubMed

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

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

2014-01-01

161

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

PubMed Central

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

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

2014-01-01

162

The magnetic properties of potassium holmium double tungstate  

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

163

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

SciTech Connect

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

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

2009-12-17

164

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

165

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

SciTech Connect

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

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

2006-07-15

166

Synthesis, structure, and magnetic properties of valence ambiguous dinuclear antiferromagnetically coupled cobalt and ferromagnetically coupled iron complexes containing the chloranilate(2-) and the significantly stronger coupling chloranilate(*3-) radical trianion.  

PubMed

Dinuclear [(TPyA)MII(CA2-)MII(TPyA)]2+ [TPyA=tris(2-pyridylmethyl)amine; CA2-=chloranilate dianion; M=Co (1(2+)), Fe (2(2+))] complexes have been prepared by the reaction of M(BF4)(2).6H2O, TPyA, H2CA, and triethylamine in MeOH solution. Their reduced forms [(TPyA)MII(CA*3-)MII(TPyA)]+ [M=Co(1+), Fe (2+)] have been synthesized by using cobaltocene, and oxidized forms of 1, [(TPyA)CoIII(CAn)CoIII(TPyA)]z+ [z=3, n=3- (1(3+)); z=4, n=2- (1(4+))], have been obtained by using FcBF4 and ThianBF4 (Fc=ferrocenium; Thian=thianthrinium), respectively. The dinuclear compound bridged chloranilates (CA2- or CA*3-) were isolated and characterized by X-ray crystallography, electrochemistry, magnetism, and EPR spectroscopy. Unlike the other redox products, valence ambiguous 13+ forms via a complex redox-induced valence electron rearrangement whereby the one-electron oxidation of the [CoIICA2-CoII]2+ core forms [CoIIICA*3-CoIII]3+, not the expected simple 1-e- transfer mixed-valent [CoIICA2-CoIII]3+ core. The M ions in 1 and 2 have a distorted octahedral geometry by coordination with four nitrogens of a TPyA, two oxygens of a chloranilate. Due to the interdimer offset face-to-face pi-pi and/or herringbone interactions, all complexes show extended 1-D and/or 2-D supramolecular structures. The existence of CA*3- in 1(3+) is confirmed from both solid-state magnetic and solution EPR data. Co-based 1n+ exhibit antiferromagnetic interactions [1(2+): g=2.24, J/kB=-0.65 K (-0.45 cm-1); 1+: g=2.36, J/kB=-75 K (52 cm-1)], while Fe-based 2n+ exhibit ferromagnetic interactions [2(2+): g=2.08, J/kB=1.0 K (0.70 cm-1); 2+: g=2.03, J/kB=28 K (19 cm-1)] [H=-2JS1.S2 for 12+ and 2(2+); H=-2J(S1.S2+S2.S3) for 1+ and 2+]. Thus, due to direct spin exchange CA*3- is a much strong spin coupling linkage than the superexchange spin-coupling pathway provided by CA2-. PMID:17269771

Min, Kil Sik; DiPasquale, Antonio G; Golen, James A; Rheingold, Arnold L; Arif, Atta M; Miller, Joel S

2007-02-28

167

Magnetic properties of intermediate-mass stars  

E-print Network

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

G. A. Wade

2006-01-30

168

Photothermal investigation of local and depth dependent magnetic properties  

NASA Astrophysics Data System (ADS)

To achieve a spatially resolved measurement of magnetic properties two different pho-tothermal approaches are used which rely on heat dissipated by magnetic resonance absorption or thermal modulation of the magnetic properties, respectively. The heat produced by modulated microwave absorption is detected by the classical photothermal methods such as photoacoustic effect and mirage effect. Examples comprise depth resolution of the magnetization of layered tapes and visualisation of magnetic excitations in ferrites. The second photothermal technique relies on the local modulation of magnetic properties by a thermal wave generated with an intensity modulated laser beam incident on the sample. This technique has a higher spatial resolution and sensitivity and has been used to characterize lateral magnetic properties of multilayers and spintronic media. To extend the lateral resolution of the ferromagnetic resonance detection into the nm-range techniques have been developed which are based on the detection of the modulated thermal microwave response by the thermal probe of an atomic force microscope (AFM) or by detection the thermal expansion of the magnetic sample in the course of the resonant microwave absorption with an AFM or tunnelling microscope. These thermal near field based techniques in ferromagnetic resonance have been successfully applied to image magnetic inhomogeneities around nano-structures and to measure the ferromagnetic resonance from magnetic nano-dots.

Pelzl, J.; Meckenstock, R.

2010-03-01

169

Magnetic properties of LaNi 5-based compounds  

NASA Astrophysics Data System (ADS)

Magnetic properties of the La(Ni 4.5M 0.5), (La 1- xR x)Ni 5 (M=Fe, Co, Mn, Cu, Cr, Si and R=Nd, Pr) and their hydride compounds have been studied by magnetization measurement using a VSM. The susceptibility ( ?) of the samples increases with Co, Mn, Fe, Nd, Pr but decreases with Cu, Cr, Si additives. The hydrogenation changes magnetic properties of the La(Ni 4.5M 0.5), (La 1- xR x)Ni 5 parent compounds. Specially, the milling process changes magnetic properties of LaNi 5. This work indicates that besides electrochemical measurements, the study of magnetic properties also gives important information on the quality of rechargeable sealed nickel-metal hydride batteries.

Tai, L. T.; Hang, B. T.; Thuy, N. P.; Hien, T. D.

2003-06-01

170

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

Microsoft Academic Search

This paper focuses on novel iron-based soft magnetic composites synthesis utilizing high thermal stability silicone resin to coat iron powder. The effect of an annealing treatment on the magnetic properties of synthesized magnets was investigated. The coated silicone insulating layer was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. Silicone uniformly coated the powder surface, resulting in a

Shen Wu; Aizhi Sun; Fuqiang Zhai; Jin Wang; Qian Zhang; Wenhuan Xu; Philip Logan; Alex A. Volinsky

171

Systematic investigation of particle size dependence of magnetic properties in soft magnetic composites  

Microsoft Academic Search

The particle size dependence of selected magnetic properties of soft magnetic composites filled with iron particles at 60vol.% was measured. For an ideal magnetization the maximum permeability ?max shows an increase with increased particle size d due to a decreased inner demagnetizing field, while the initial permeability ?i stays constant. The coercivity Hc shows a linear increase with increased inverse

M. Anhalt

2008-01-01

172

Magnetic and microstructural properties of some lodestones  

NASA Technical Reports Server (NTRS)

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

Wasilewski, P. J.

1977-01-01

173

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)(H 2O)], [Zn(His)(Ox)(H 2O)] (or [Zn(His)(Ox)]·(H 2O)), [Cd(His)(Ox)(H 2O) 2] and [Co(His)(Ox)(H 2O)], 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)(H 2O)] complex has a supramolecular structure constructed by two different non-covalent interactions as hydrogen bond and C-H⋯? interactions. EPR studies on [Cu(His)(Ox)(H 2O)], Cu 2+-doped [Zn(His)(Ox)(H 2O)] and [Cd(His)(Ox)(H 2O) 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

174

Synthesis and magnetic properties of Co-Zn magnetic fluid  

NASA Astrophysics Data System (ADS)

Co 1-xZn xFe 2O 4 (with x varying from 0 to 0.7) nanoparticles to be used for ferrofluid preparation were prepared by chemical co-precipitation method. The fine particles were suitably dispersed in transformer oil using oleic acid as the surfactant. The magnetization ( Ms) and the size of the particles were measured at room temperature. The magnetization ( Ms) was found to decrease with the increase in zinc substitution. The magnetic particle size ( Dm) of the fluid was found to vary from 11.19 to 4.25 nm decreasing with the increase in zinc substitution.

Vaidyanathan, G.; Sendhilnathan, S.

175

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

176

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

Microsoft Academic Search

This paper reports the measurement and modelling of magnetic properties of SOMALOYTM 500, a soft magnetic composite (SMC) material, under different 2D vector magnetisations, such as alternating along one direction, circularly and elliptically rotating in a 2D plane. By using a 2D magnetic property tester, the B–H curves and core losses of the SMC material have been measured with different

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

2006-01-01

177

The electric properties of low-magnetic-loss magnetic composites containing Zn-Ni-Fe particles.  

PubMed

Recently, magnetic composites consisting of magnetic particles dispersed in a polymer matrix have been widely discussed for miniaturizing high-frequency electronic components such as antennae. Previously, we investigated the influence of the manufacturing process on the homogeneous dispersion of magnetic particles in the polymer and on the magnetic properties of the magnetic composites. In order to miniaturize electronic components, it is crucial to be able to independently control the permeability and permittivity in magnetic composites. This paper investigates the anisotropy and frequency dependence of the dielectric properties of magnetic composites fabricated from 20 vol% Zn(5)Ni(75)Fe(20) flaked particles. The permittivity of magnetic composites fabricated from Zn(5)Ni(75)Fe(20) flaked particles is anisotropic: at 1 GHz, the relative permittivities parallel and perpendicular to the plane of the specimens are 27.2 and 16.9, respectively. The permittivity varied little between frequencies of 50 MHz and 10 GHz. PMID:21832455

Hidaka, Nobuhiro; Ishitsuka, Masayuki; Shirakata, Yasushi; Teramoto, Akinobu; Ohmi, Tadahiro

2009-10-28

178

The growing complexity of international policy in intellectual property.  

PubMed

Intellectual property has historically been a self-contained policy at the international level. With the introduction of the TRIPs Agreement in 1994 and developments since the conclusion of the TRIPs Agreement, the relationship between intellectual property policy and other areas of public policy has become much more complex and interactive. This shift reflects the centrality of intellectual property in the knowledge economy, the rapid development of enabling technologies, notably the Internet and biotechnology, and the advent of the networked society. The consequences of this shift are manifold and herald the increased sophistication and complexity that may be expected of intellectual property regimes in the knowledge economy. PMID:15726995

Gurry, Francis

2005-01-01

179

Magnetic properties of Be or Cu-substituted NiZn ferrites  

NASA Astrophysics Data System (ADS)

Polycrystalline NiZn ferrites with the chemical formula (Ni0.3Zn0.7)MexFe2O4 where Me is Be or Cu and x=0.05, 0.1 and 0.25 have been prepared by a ceramic method. Selected magnetic properties such as Curie temperature Tc and saturation magnetization Ms of the ferrites have been measured and discussed. Complex initial (relative) permeability ?˜=?'-j?? measurements have also been performed on the samples in the frequency range from 100 kHz to 100 MHz and the contribution of magnetization mechanisms is discussed.

Sláma, Jozef; Dosoudil, Rastislav; Ušáková, Marianna; Ušák, Elemír; Grusková, Anna; Jan?árik, Vladimír

2006-09-01

180

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

PubMed

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

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

2006-05-21

181

Tuning the photophysical properties of amidophosphine complexes of copper  

E-print Network

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

Mickenberg, Seth F. (Seth Fox)

2009-01-01

182

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

PubMed

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

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

2014-11-24

183

Magnetic properties and crystal structure of ?-Ta  

NASA Astrophysics Data System (ADS)

Polycrystalline samples of ?-Ta with Frank-Kasper ?-phase structure prepared by electrolysis are studied. The atomic parameters are determined by the Rietveld method. The magnetic susceptibility is measured in the temperature range 4.2 < T < 273 K and the dependence of the magnetization on the magnetic field strength is measured at 4.2 and 77 K. The analysis of interatomic distances and the results of magnetic measurements indicate that clusters with a localized excess charge exist in ?-Ta. The data obtained in this study suggest structural changes in ?-Ta at T < 77 K.

Shamra?, V. F.; Warhulska, J. K.; Arakcheeva, A. V.; Grinevich, V. V.

2004-11-01

184

Complex Fuzzy Set-Valued Complex Fuzzy Measures and Their Properties  

PubMed Central

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

Ma, Shengquan; Li, Shenggang

2014-01-01

185

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

186

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

PubMed

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

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

2013-11-18

187

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

NASA Astrophysics Data System (ADS)

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

Shahmansouri, Mehran

2014-07-01

188

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

SciTech Connect

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

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

2014-01-21

189

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

PubMed

The magnetic and magnetothermal properties of a high purity terbium single crystal have been re-investigated from 1.5 to 350 K in magnetic fields ranging from 0 to 75 kOe using magnetization, ac magnetic susceptibility and heat capacity measurements. The magnetic phase diagram has been refined by establishing a region of the fan-like phase broader than reported in the past, by locating a tricritical point at 226 K, and by a more accurate definition of the critical fields and temperatures associated with the magnetic phases observed in Tb. PMID:24451321

Zverev, V I; Tishin, A M; Chernyshov, A S; Mudryk, Ya; Gschneidner, K A; Pecharsky, V K

2014-02-12

190

EM Properties of Magnetic Minerals at RADAR Frequencies  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

191

Electronic and structural properties of complex oxides  

NASA Astrophysics Data System (ADS)

This thesis focuses on oxides whose crystalline forms are isomorphic with silica (SiO2) in order to understand their electronic and structural properties. Silica is one of the most widely investigated oxides due to its important electronic, geophysical arid chemical properties. As many as 40 crystalline polymorphs along with amorphous and liquid forms have been described and studied in the literature. The alpha-quartz structure of silica exhibits interesting mechanical and pressure induced behavior. For example, when it is subjected to pressure, it will undergo a slow amorphization. There are many materials that are isostructural with SiO2. Isostructural materials should have similar properties and exhibit similar characteristics. Here we examine three materials: AlPO4, GaAsO4 and GeO 2. AlPO4 has attracted considerable attention owing to the potential technological importance of its high pressure behavior as a memory glass. GaAsO4 is another III-V analog compound, but shows no evidence of pressure induced amorphization as quartz does. GeO2, like silica, undergoes pressure induced amorphization in the alpha-quartz structure, but unlike silica, occurs only in two stable polymorphs. The objective of this thesis is to present a comprehensive picture of oxides that are isostructural with silica. We have computed a variety of properties of each material: (1) Equation of state in the form of volume versus pressure, (2) Structural properties as a function of pressure such as lattice constants and the internal coordinates describing the positions of constituent atoms within the cell, (3) Elastic properties such as the bulk modulus, (4) Electronic properties such as density of states, band structure, and charge density. Computations were performed using a quantum mechanical method based on "soft" ab initio pseudopotentials constructed within a local density approximation. The pseudopotentials required can be extracted from atomic structure calculations. A key element of the pseudopotential includes the elimination of chemically inert states, i.e., the core states. The resulting pseudopotential is weak and the wavefunctions can be described by simple basis sets such as plane waves. This approach is attractive for its reliability and its high predictive power.

Christie, Diane Marie

192

Magnetic properties of Ni substituted Y-type barium ferrite  

SciTech Connect

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

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

2014-05-07

193

Magnetic properties of Ni substituted Y-type barium ferrite  

NASA Astrophysics Data System (ADS)

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

Won, Mi Hee; Kim, Chul Sung

2014-05-01

194

Magnetic Properties and Structure of Oxyhemoglobin  

Microsoft Academic Search

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

Linus Pauling

1977-01-01

195

Magnetic properties of new Haldane gap materials  

NASA Astrophysics Data System (ADS)

High-field magnetization and susceptibility measurements have been performed on the linear-chain Heisenberg antiferromagnets Ni(dmpn) 2N 3(CIO 4) and catena-(?-N 3)?Ni(323-tet)](CIO 4). These compounds have an energy gap at low temperatures, and the values of energy gap, crystalline field constants are estimated from the high-field magnetization data.

Takeuchi, T.; Yosida, T.; Inoue, K.; Yamashita, M.; Kumada, T.; Kindo, K.; Merah, S.; Verdaguer, M.; Renard, J. P.

1995-02-01

196

Magnetic properties of dense holographic QCD  

E-print Network

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

Oren Bergman; Gilad Lifschytz; Matthew Lippert

2009-04-30

197

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

PubMed

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

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

2014-03-01

198

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

PubMed Central

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

Nishida, Keiji; Silver, Pamela A.

2012-01-01

199

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

PubMed

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

Nishida, Keiji; Silver, Pamela A

2012-01-01

200

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

201

Magnetic and Transport Properties of FeAs Single Crystals  

Microsoft Academic Search

Magnetic susceptibility and transport properties of an itinerant helimagnet FeAs are studied in single-crystalline samples of this binary compound. A kink due to the magnetic transition is observed in the temperature dependences of both the susceptibility and the resistivity. The Hall coefficient shows a reentrant sign change with temperature, signifying a complicated competition between multiple bands. In the helical ordered

Kouji Segawa; Yoichi Ando

2009-01-01

202

Distribution of Helical Properties of Solar Magnetic Fields  

Microsoft Academic Search

We summarize studies of helical properties of solar magnetic fields such as current helicity and twist of magnetic fields in solar active regions (ARs), that are observational tracers of the alpha-effect in the solar convective zone (SCZ). Information on their spatial distribution is obtained by analysis of systematic magnetographic observations of active regions taken at Huairou Solar Observing Station of

Kirill M. Kuzanyan; Victor G. Lamburt; Hong-Qi Zhang; Shu-Dong Bao

2003-01-01

203

Electronic and magnetic properties of Am and Cm  

SciTech Connect

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

Edelstein, N.

1985-02-01

204

Magnetic properties of substituted M-type hexagonal ferrites  

Microsoft Academic Search

We have studied the BaFe12-2xMxTixO19 system where M = Co, Ni and Zn and 0 < x < 1. We have measured static and dynamic properties of single crystal platelets. We find that Co introduces a strong temperature dependence of the magnetic anisotropy field Ha, and large intrinsic magnetic relaxation, but Ni and Zn do not.

P. Lubitz; C. Vittoria; J. Schelleng; W. G. Maisch

1980-01-01

205

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

NASA Astrophysics Data System (ADS)

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

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

206

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

PubMed Central

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

2012-01-01

207

Colossal anisotropy of the magnetic properties of doped lithium nitrodometalates  

SciTech Connect

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

Antropov, Vladimir P [Ames Laboratory; Antonov, Victor N [Ames Laboratory

2014-09-01

208

Complex magnetism of the Fe monolayer on Ir(111)  

NASA Astrophysics Data System (ADS)

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. Both stackings of the monolayer, i.e. face centered cubic (fcc) and hexagonal closed packed (hcp), are observed experimentally. The magnetic structure of both types is imaged with SP-STM. From these experiments, we propose a nanoscale magnetic mosaic structure for the fcc-stacking with 15 atoms in the unit cell. For hcp-stacking, the tunneling spectra are similar to the fcc case, however, the magnetic contrast in the SP-STM images is not as obvious. In our first-principles calculations, a collinear antiferromagnetic (AFM) state with a 15 atom in-plane unit cell (AFM 7 : 8 state) is found to be more favorable than the ferromagnetic state for both fcc- and hcp-stacking. Calculated SP-STM images and spectra are also in good agreement with the experimental data for the fcc case. We performed spin spiral calculations which are mapped to a classical Heisenberg model to obtain the exchange-interaction constants. From these calculations, it is found that the AFM 7 : 8 state is energetically more favorable than all solutions of the classical Heisenberg model. While the obtained magnetic exchange constants are rather similar for the fcc and hcp stacking, a comparison with the experiments indicates that competing interactions could be responsible for the differences observed in the magnetically sensitive measurements.

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

2007-10-01

209

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

PubMed

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

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

2007-06-01

210

Properties of Nucleoprotein Complexes Containing Replicating Polyoma DNA  

PubMed Central

Short-lived nucleoprotein complexes (r-py complex) containing replicating polyoma DNA were isolated from infected cells after lysis with Triton X-100. The Triton lysing procedure of Green, Miller, and Hendler (1971) releases most complexes containing supercoiled viral DNA (py complex) from nuclei, but liberates only a portion of r-py complexes. r-py Complexes are associated more strongly with nuclear sites but can be extracted by prolonged incubation of nuclei in lysing solution. Complexes containing replicating polyoma DNA appear to be precursors to stable complexes containing supercoiled DNA. Sedimentation and buoyant density studies indicate that protein is bound to both r-py complexes and py complexes at a ratio of protein to DNA of about 1 to 2/1. Both types of complexes sediment as if the viral DNA is more compact than free DNA and both undergo major reversible configurational changes with increased salt concentration. Changes resulting from enzymatic and chemical treatment indicate that there may be two or more protein components in both r-py complex and py complex. One component is digested by Pronase and trypsin while another is resistant to the enzymes but released by deoxycholate. The abundance and similarity in chemical and physical properties of protein bound to all forms of polyoma DNA suggest that part of the protein molecules may serve in a structural capacity. PMID:4359957

Goldstein, David A.; Hall, Mark R.; Meinke, William

1973-01-01

211

Complex studies of properties of nanostructured silicon  

NASA Astrophysics Data System (ADS)

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

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

2006-08-01

212

Mechanical properties of individual focal adhesions probed with a magnetic microneedle.  

PubMed

A permanent magnetic microneedle was developed to apply tensional forces to integrin receptors via ligand-coated magnetic microbeads while optically analyzing the mechanical properties of individual focal adhesions. Force application (130 pN for 3 s) through activated beta1 integrins produced less bead displacement than when unligated integrins were stressed. This strengthening response differed markedly on a bead-by-bead basis, correlated directly with local focal adhesion assembly, and was similar when analyzed at 4 degrees C, indicating that it was due to passive material properties of the cell. Viscoelastic analysis clarified that recruitment of focal adhesion proteins increased the local elastic stiffness of the adhesion complex without changing its viscous behavior. These data indicate that individual focal adhesions exhibit distinct mechanical properties that depend upon local focal adhesion assembly, and that these local variations in micromechanics can be detected and analyzed within living cells using the permanent magnetic microneedle technique. PMID:14697256

Matthews, Benjamin D; Overby, Darryl R; Alenghat, Francis J; Karavitis, John; Numaguchi, Yasuchi; Allen, Philip G; Ingber, Donald E

2004-01-16

213

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

NASA Astrophysics Data System (ADS)

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

Shoukry, Azza A.; Shoukry, Mohamed M.

2008-08-01

214

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

215

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

216

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

PubMed

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

Cervetti, Christian; Heintze, Eric; Bogani, Lapo

2014-03-21

217

Effect of microscopic disorder on magnetic properties of metamaterials.  

PubMed

We analyze the effect of microscopic disorder on the macroscopic properties of composite metamaterials and study how weak statistically independent fluctuations of the parameters of the structure elements can modify their collective magnetic response and left-handed properties. We demonstrate that even a weak microscopic disorder may lead to a substantial modification of the metamaterial magnetic properties, and a 10% deviation in the parameters of the microscopic resonant elements may lead to a substantial suppression of the wave propagation in a wide frequency range. A noticeable suppression occurs also if more than 10% of the resonant magnetic elements possess strongly different properties, and in the latter case the defects can create an additional weak resonant line. These results are of a key importance for characterizing and optimizing novel composite metamaterials with the left-handed properties at terahertz and optical frequencies. PMID:16803055

Gorkunov, Maxim V; Gredeskul, Sergey A; Shadrivov, Ilya V; Kivshar, Yuri S

2006-05-01

218

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

219

Electronic and magnetic properties of ultrathin rhodium nanowires  

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

220

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

221

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

222

Magnetic Properties of Plutonium Hydride and Deuteride  

Microsoft Academic Search

Magnetic investigations on plutonium hydride (PuH2.74) and deuteride (PuD2.74) have shown these compounds to be either ferromagnetic, like the corresponding uranium compounds, or ferrimagnetic. The Curie temperatures of plutonium hydride and deuteride are the same, within experimental error, and are 107°K. The magnetic moment for the hydride and deuteride are greater than 0.24 and 0.13 Bohr magnetons per mole of

C. E. Olsen; T. A. Sandenaw; B. T. MATTHIAst

1963-01-01

223

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

224

Geometric properties of magnetic field lines on toroidal magnetic surfaces in the context of plasma equilibrium  

SciTech Connect

An analysis of plasma equilibrium in a magnetic confinement system includes studies of how the shape of the magnetic surfaces is distorted with varying magnitude and profile of the plasma pressure. Such studies allow one, in particular, to determine the maximum {beta} value consistent with equilibrium, {beta}{sub eq}, i.e., the maximum plasma pressure above which the equilibrium in a confinement system under analysis is impossible. Since the magnetic field lines form magnetic surfaces, their global relationship with equilibrium is obvious. Here, special attention is paid to a local relationship between equilibrium and geometric properties of the magnetic field lines.

Skovoroda, A. A. [Russian Research Centre Kurchatov Institute, Nuclear Fusion Institute (Russian Federation)

2007-08-15

225

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

226

Magnetic properties of carbonyl iron particles in magnetorheological fluids  

NASA Astrophysics Data System (ADS)

Knowledge of the magnetic properties of dispersed magnetic particles is a prerequisite to the design an MR fluid with desired performance. A term specific susceptibility is introduced for characterization of particle susceptibility. The study was performed with the Bartington MS2B magnetic susceptibility system on small samples volume. Specific magnetic susceptibility of iron particles was found to be a linear function of median particle size. Structural change in the fluid, including particle organization, led to susceptibility drift and may affect fluid performance. It was shown that susceptibility data can be used for evaluation of the concentration of carbonyl iron particles in MR fluids.

Gorodkin, S. R.; James, R. O.; Kordonski, W. I.

2009-02-01

227

Reactivity of 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole, structures and magnetic properties of polynuclear and polymeric Mn(II), Cu(II) and Cd(II) complexes.  

PubMed

Five new complexes were obtained from solution or hydrothermal reactions of M(OAc)(2) (M = Mn, Cu and Cd) or CuCl(2) with 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (abpt) and NaN(3) or 1,3,5-benzenetricarboxylic acid (btcH(3)) in different molar ratios. Structural analysis reveals that Cd(abpt) units in [Cd(abpt)(mu(1,1)-N(3))(2)](n) (1) are bridged by double mu(1,1) end-on (EO) azides into 1D zigzag coordination chains. Similar structural motifs, i.e. the chelation of abpt to the metal center and the double bridges of EO azides, are found in [Mn(4)(abpt)(4)(mu(1,1)-N(3))(8)(H(2)O)(2)] (2). The terminal aqua molecules and the monodentate N(3)(-) groups lead to the formation of a tetranuclear complex rather than a polymeric compound. The abpt underwent deamination in the presence of copper ions during the process of coordination and became 3,5-bis(pyridin-2-yl)-1,2,4-triazolate (bpt-H) in 3-5. [Cu(4)(bpt-H)(4)(N(3))(4)].4.5H(2)O (3) is a neutral tetranuclear grid-like complex, in which the azides act as monodentate ligands. A similar [Cu(4)(bpt-H)(4)](4+) grid-like unit was found in [Cu(4)(bpt-H)(4)(mu-btcH)Cl(2)].2H(2)O (4) and a pair of symmetry-related copper atoms are bridged by the mu-btcH(2)(-) coligand in a butterfly-shaped structure. In [Cu(2)(bpt-H)(mu(6)-btc)(H(2)O)](n) (5), the tetranuclear {Cu(4)(mu-bpt-H)(2)(mu(3)-carboxylate)(2)}(4+) units are bridged by mu(6)-btc(3-) ligands in a 2D step-like layer structure. Temperature-dependent magnetic susceptibility measurements reveal that the double mu(1,1)-N(3)(-) bridges in 2 transmit the ferromagnetic interactions between Mn(2+) centers (J(1) = J(2) = +3.09(4) cm(-1), g(Mn(II)) = 2.02(1)), and the mu-(bpt-H)(-) bridges transmit moderate antiferromagnetic interactions in both 3 (J = -12.78(13) cm(-1)) and 4 (J(1) = -14.96(11) cm(-1)). In 4 the antiferromagnetic coupling via the mu-btcH(2-) bridge was found as the second coupling pathway (J(2) = -9.48(7) cm(-1)). The coexistence of ferromagnetic and antiferromagnetic coupling between four Cu(2+) centers occurs in 5 (J(1) = -0.88(3) cm(-1) and J(2) = +5.01(2) cm(-1)). The magneto-structural relationship for tetranuclear copper pyrazolate/triazolate compounds has been discussed. PMID:19921064

Meng, Zhao-Sha; Yun, Lei; Zhang, Wei-Xiong; Hong, Chao-Gang; Herchel, Radovan; Ou, Yong-Cong; Leng, Ji-Dong; Peng, Meng-Xia; Lin, Zhuo-Jia; Tong, Ming-Liang

2009-12-14

228

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

229

On the theory of rheological properties of bimodal magnetic fluids  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

230

Magnetic properties of some high strained soft magnetic alloys  

NASA Astrophysics Data System (ADS)

The coercivity and saturation magnetic polarization of the Fe-16wt%Al, Fe-6wt%Si alloys and pure iron specimens after high degree of deformation by cold rolling were investigated. High density defect areas are taken as an individual phase called the interfacial phase similarly to that in nanocrystalline materials. Dependences of the magnetic parameters on the deformation degree are discussed from the point of view of content and state of interfacial phase as determined from Mössbauer spectra. The changes are more pronounced in Fe-16wt%Al and Fe-6wt%Si specimens in comparison with the pure iron ones. This is ascribed to the atomic order extinction and to enlarged formation of interfacial phase due to low mobility of dislocations.

Schneeweiss, O.; ?ák, T.; Jirásková, Y.

1992-01-01

231

The synthesis, structure, magnetic and luminescent properties of a new tetranuclear dysprosium (III) cluster  

SciTech Connect

The synthesis and characterization of [Dy{sub 4}(dhampH{sub 3}){sub 4}(NO{sub 3}){sub 2}](NO{sub 3}){sub 2} (1), a new tetranuclear dysprosium (III) complex, is described. The compound was characterized by its X-ray structure, magnetic properties as well as the luminescent spectra. The compound crystallizes in a P1-bar space group with a zig-zag linear form of geometry. The ac magnetic susceptibilities of the molecule indicate that it is a magnetic molecule with a slow magnetization relaxation. The molecule also exhibits an emission spectrum that was confirmed to be ligand based. These results indicate that this molecule has both a slow magnetization relaxation (that could be potentially a SMM) and luminescent properties. - Graphical Abstract: A new tetranuclear dysprosium (III) complex [Dy{sub 4}(dhampH{sub 3}){sub 4}(NO{sub 3}){sub 2}](NO{sub 3}){sub 2} is synthesized and reported in this paper. This molecule has luminescence and can potentially act as a SMM. Highlights: Black-Right-Pointing-Pointer A new designed ligand (dhampH{sub 5}) was syntheisized. Black-Right-Pointing-Pointer A new tetra-dysprosium cluster [Dy{sub 4}(dhampH{sub 3}){sub 4}(NO{sub 3}){sub 2}](NO{sub 3}){sub 2} was made. Black-Right-Pointing-Pointer Slow magnetization relaxation phenomenon was observed. Black-Right-Pointing-Pointer Ligand-based luminescence was observed.

Chen, Yen-Han; Tsai, Yun-Fan [Department of Chemistry, Fu Jen Catholic University, Hsinchuang, Taipei, 24205 Taiwan (China); Lee, Gene-Hsian [Instrument Centre, College of Science, National Taiwan University, Taipei, 106 Taiwan (China); Yang, En-Che, E-mail: 071549@mail.fju.edu.tw [Department of Chemistry, Fu Jen Catholic University, Hsinchuang, Taipei, 24205 Taiwan (China)

2012-01-15

232

MAGNETIC PROPERTIES OF AN ANTIFERROMAGNETIC TWO-SINGLET SYSTEM.  

E-print Network

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

Paris-Sud XI, Université de

233

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

E-print Network

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

Li, Jing

234

One-pot synthesis of CoFeFe3O4 nanocomposites with tunable magnetic properties and long term stability  

E-print Network

One-pot synthesis of CoFe­Fe3O4 nanocomposites with tunable magnetic properties and long term by thermal decomposition of iron­oleate complex [2]. The magnetic metals (Co, Fe) or their alloys exhibit-octadecene and oleic acid. The CoFe­Fe3O4 nanocomposites exhibit tunable saturation magnetization values

Qi, Limin

235

Optical properties of magnetic-plasmonic nanoparticle multilayers  

NASA Astrophysics Data System (ADS)

Magnetic-plasmonic materials are an interesting class of materials for both fundamental and applied research. Knowledge of the optical properties and their origin in the materials is a must. Using a layer-by-layer method, we fabricated magnetic-plasmonic nanoparticle multilayers and measured their optical properties. Discrete dipole approximation calculations to model the optical properties of such materials allow us to understand the observed optical features. Comparing experimental and theoretical results provides us with a detailed insight in the build-up of the nanoparticle multilayers and shows that nanoparticles of the added layers fill holes in previous layers and improve the quality of the sample.

Brullot, Ward; Verbiest, Thierry

2014-09-01

236

Calculation of microscopic exchange interactions and modelling of macroscopic magnetic properties in molecule-based magnets.  

PubMed

The state-of-the-art theoretical evaluation and rationalization of the magnetic interactions (J(AB)) in molecule-based magnets is discussed in this critical review, focusing first on isolated radical···radical pair interactions and afterwards on how these interactions cooperate in the solid phase. Concerning isolated radical pairwise magnetic interactions, an initial analysis is done on qualitative grounds, concentrating also on the validity of the most commonly used models to predict their size and angularity (namely, McConnell-I and McConnell-II models, overlap of magnetic orbitals,…). The failure of these models, caused by their oversimplified description of the magnetic interactions, prompted the introduction of quantitative approaches, whose basic principles and relative quality are also evaluated. Concerning the computation of magnetic interactions in solids, we resort to a sum of pairwise magnetic interactions within the Heisenberg Hamiltonian framework, and follow the First-principles Bottom-Up procedure, which allows the accurate study of the magnetic properties of any molecule-based magnet in an unbiased way. The basic principles of this approach are outlined, applied in detail to a model system, and finally demonstrated to properly describe the magnetic properties of molecule-based systems that show a variety of magnetic topologies, which range from 1D to 3D (152 references). PMID:21321725

Novoa, J J; Deumal, M; Jornet-Somoza, J

2011-06-01

237

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

PubMed

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

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

2015-02-01

238

Influence of nitrogen on magnetic properties of indium oxide  

NASA Astrophysics Data System (ADS)

Magnetic properties of indium oxide (In2O3) prepared by the decomposition of indium nitrate/indium hydroxide in the presence of ammonium chloride (NH4Cl) has been investigated. Structural and optical characterizations confirm that nitrogen is incorporated into In2O3. Magnetization has been convoluted to individual diamagnetic paramagnetic and ferromagnetic contributions with varying concentration of NH4Cl. Spin wave with diverging thermal exponent dominates in both field cool and zero field cool magnetizations. Uniaxial anisotropy plays an important role in magnetization as a function of magnetic field at higher concentration of NH4Cl. Avrami analysis indicates the absence of pinning effect in the magnetization process. Ferromagnetism has been interpreted in terms of local moments induced by anion dopant and strong hybridization with host cation.

Ashok, Vishal Dev; De, S. K.

2013-07-01

239

PREDICTION OF THERMODYNAMIC PROPERTIES OF COMPLEX FLUIDS  

SciTech Connect

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

Marc Donohue

2006-01-05

240

Magnetic properties of neptunium and plutonium hydrides  

Microsoft Academic Search

The magnetic susceptibility and magnetization of NpHx and PuHx (2.0<=x<=3.0) compounds have been measured between 4 and 700 K. The susceptibility of the NpHx compounds is weakly temperature dependent and a crystal-field calculation based on the 5f4(Np3+) ground-state configuration was in reasonable agreement with the experimental results for the dihydride (cubic CaF2-type structure). The cubic plutonium dihydride has a susceptibility

A. T. Aldred; G. Cinader; D. J. Lam; L. W. Weber

1979-01-01

241

Nuclear magnetic resonance investigations of the structure and magnetic properties of metallic multilayers and nanocomposites  

Microsoft Academic Search

As a probe of the short-range chemical and topological order, nuclear magnetic resonance (NMR) has proved useful to investigate\\u000a the nanostructure of magnetic multilayers or granular systems and, in particular, to evaluate the nature, sharp or diffuse,\\u000a of interfaces in such nanocomposites. These structural aspects are shortly reviewed in the paper. A larger emphasis is given\\u000a to the magnetic properties

P. Panissod; C. Mény

2000-01-01

242

Effect of coupling strength on magnetic properties of exchange spring magnets  

E-print Network

can be characterized by ferromagnetic exchange coupling between a magnetically soft phase, is a key parameter in controlling the spring magnet properties. A ferromagnetically coupled hard­soft are nanocomposites of mag- netically soft and hard phases. These composites have the potential of very high (BH

Liu, J. Ping

243

Magnetic properties of soft magnetic composites prepared with crystalline and amorphous powders  

Microsoft Academic Search

Physical properties of soft magnetic composites prepared with a mixture of amorphous (FeSiBC) and crystalline (Fe) powders coated with distinct electrical insulator contents are reported. Density, saturation polarization, permeability and coercivity of the cores reduce linearly with the increase of the softer magnetic phase amount and a general relation can be expressed by a rule of mixtures. The behavior of

E. A. Périgo; S. Nakahara; Y. Pittini-Yamada; Y. de Hazan; T. Graule

2011-01-01

244

Magnetic Nanoparticles Size-Dependent Magnetic Properties of Colloidal  

E-print Network

for technological applica- tions owing to their unique size-dependent properties and excellent processability temperature to form a brown suspension. After centrifugation at 3000 rpm for 10 min, the supernatant precipitate to give a brown suspension, which was sonicated for 10 min to form a clear solution. Removal

Kim, Bongsoo

245

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

PubMed Central

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

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

2013-01-01

246

DFT Study of Optical Properties of Pt-based Complexes  

Microsoft Academic Search

We report Density Functional Theory (DFT) calculations providing the geometrical and electronic structures, as well as the vibrational and optical properties of the homologous series of Pt-pyramidalized olefin complexes (CH2)n-(C8H10)Pt(PH3)2, where n = 0, 1, and 2, in their neutral and oxidized states. All complexes were geometry optimized for the singlet ground state in vacuum using DFT methods with B3LYP

Corneliu I. Oprea; Anca Dumbrava; Florin Moscalu; Atnanassios Nicolaides; Mihai A. Gîrtu

2010-01-01

247

Luminescent Cyclometalated Platinum and Palladium Complexes with Novel Photophysical Properties  

NASA Astrophysics Data System (ADS)

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

Turner, Eric

248

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

PubMed

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

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

2014-03-01

249

Metal complexes and solvent extraction properties of isonitrosoacetophenone 2-aminobenzoylhydrazone.  

PubMed

Three types of copper complexes as well as an oximate-bridged nickel complex with isonitrosoacetophenone 2-aminobenzoylhydrazone (H(2)L) have been prepared in ethanolic solution and characterized by elemental analyses, IR, (1)H NMR, UV-vis and magnetic susceptibility measurement. IR spectra show the ligand coordinates as a neutral, monoanionic and dianionic O,N,N-tridentate acylhydrazoneoxime ligand depending reaction conditions and metal salts employed. The elemental analyses results, spectroscopic and magnetic data are consistent with the formation of mononuclear copper complexes and binuclear complexes with both copper and nickel. The effects of varying pH and solvent on the absorption behavior of both ligand and complexes have been investigated. The extraction ability of acylhydrazoneoxime ligand has been examined by the liquid-liquid extraction of selected transition metal [Cu(2+), Ni(2+), Co(2+), Cr(3+), Hg(2+), Zn(2+), Cd(2+) and Mn(2+)] cations. The ligand shows strong binding ability toward copper(II) ion. PMID:16495123

Gup, Ramazan; Giziro?lu, Emrah

2006-11-01

250

3D Magnetic Reluctivity Tensor of Soft Magnetic Composite Material  

Microsoft Academic Search

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

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

2006-01-01

251

Structural and magnetic properties of TM-SiO2 (TM = Fe, Co, Ni) films  

NASA Astrophysics Data System (ADS)

TMx-(SiO2)1-x (TM=Fe, Co, Ni) thin films were prepared in a wide concentration range (0.35 ?x?1). Structure was studied with transmission electron microscopy (TEM), X-ray diffraction (XRD) and small angle X-ray scattering (SAXS). Magnetic and magnetotransport properties were investigated by means of magnetization and Hall effect measurements. TEM images display nanometric spherical structures embedded in a SiO2 amorphous matrix, with typical sizes increasing from 3 to 5nm when TM volume concentration x is increased. SAXS measurements indicate a complex structure formed by nanosized objects. XRD measurements show that the structure is composed by amorphous SiO2 and TM crystallites. Slightly above the percolation threshold all samples display giant Hall effect. The observed magnetic properties are dependent on x, and display an evolution resulting from the progressive increase of the mean particle size.

Socolovsky, L. M.; Denardin, J. C.; Brandl, A. L.; Knobel, M.; Zhang, X. X.

2003-05-01

252

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

253

Photometric properties of resolved and unresolved magnetic elements  

E-print Network

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

Serena Criscuoli; Mark Rast

2008-12-09

254

The symmetry properties of planetary magnetic fields  

NASA Technical Reports Server (NTRS)

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

Raedler, Karl-Heinz; Ness, Norman F.

1990-01-01

255

Basic magnetic properties of bituminous coal  

USGS Publications Warehouse

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

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

1979-01-01

256

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

257

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

NASA Astrophysics Data System (ADS)

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

Kou, Xiaoming

2011-12-01

258

High Field Properties of Geometrically Frustrated Magnets  

Microsoft Academic Search

Above the saturation field, geometrically frustrated quantum antiferromagnets have dispersionless low-energy branches of excitations corresponding to localized spin-flip modes. Transition into a partially magnetized state occurs via condensation of an infinite number of degrees of freedom. The ground state below the phase transition is a magnon crystal, which breaks only translational symmetry and preserves spin-rotations about the field direction. We

M. E. Zhitomirsky; Hirokazu Tsunetsugu

2005-01-01

259

Magnetic properties of nanoscale iron particles  

NASA Astrophysics Data System (ADS)

Nanoscale iron particles have been prepared by iron atom clustering in cold pentane. Particle growth was terminated by adsorption of oleic acid, yielding air stable particles ranging in size from 2 to 12 nm, that were amorphous according to XRD analysis. TEM analysis showed that the larger particles were prolate spheroids while the smaller ones were spherical. The as-prepared sample had a room-temperature saturation magnetization of Ms=12.3 emu/g and a coercivity of Hc=60 Oe. Following heat treatment under argon, the XRD results showed the following reaction scheme; oxidation to Fe3O4 at 360 °C and reduction to ?-Fe at 520 °C (processes apparently due to adsorbed oleic acid). For the 520 °C treated sample, the room-temperature saturation magnetization and coercivity were Ms=200 emu/g and Hc=20 Oe, respectively. By pentane washing of the as-prepared sample, the smaller particles could be separated by filtration leaving the larger 8-12 nm particles on the filter. This powdered sample trapped on the filter had Ms=54.9 emu/g and Hc=60 Oe. Heat treatment of this sample also caused oxidation to Fe3O4 at 360 °C and an incomplete reduction to ?-Fe and FeO at 520 °C. For the 520 °C treated sample, the recorded room-temperature saturation magnetization and coercivity were Ms=123.6 emu/g and Hc=20 Oe, respectively.

Kerznizan, Carl F.; Klabunde, Kenneth J.; Sorensen, Christopher M.; Hadjipanayis, George C.

1990-05-01

260

Microstructure and magnetic properties of FINEMET nanowires  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

261

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

2012-12-21

262

Effect of pressure on the magnetic properties of lanthanum manganite  

SciTech Connect

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

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

2010-08-15

263

Magnetic properties of substituted M-type hexagonal ferrites  

NASA Astrophysics Data System (ADS)

We have studied the BaFe 12-2 xM xTi xO 19 system where M = Co, Ni and Zn and 0 < x < 1. We have measured static and dynamic properties of single crystal platelets. We find that Co introduces a strong temperature dependence of the magnetic anisotropy field Ha, and large intrinsic magnetic relaxation, but Ni and Zn do not.

Lubitz, P.; Vittoria, C.; Schelleng, J.; Maisch, W. G.

1980-01-01

264

Magnetic properties of a long, thin-walled ferromagnetic nanotube  

NASA Astrophysics Data System (ADS)

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

Sun, Chen; Pokrovsky, Valery L.

2014-04-01

265

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

PubMed Central

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

2013-01-01

266

Control of Magnetic Properties of Carbon Nanotubes Filled with Iron  

NASA Astrophysics Data System (ADS)

Carbon nanotubes (CNTs) filled with iron nanowires show high coercivity owing to their shape anisotropy originating from the high-aspect-ratio shapes of the iron nanowires. In this study, CNTs filled with iron were prepared by the thermal chemical vapor deposition (T-CVD) method using ferrocene as a precursor, and the magnetic properties of the synthesized CNTs were examined in detail. It was found that the CVD temperature and the amount of the ferrocene introduced into the CVD reactor influence the amount of CNT growth and the magnetic properties. The high coercivity of approximately 1.6 kOe or higher was obtained under certain CVD conditions. The selected-area electron diffraction analysis showed that the magnetic properties of the CNTs filled with iron are determined by the crystal structure (?-Fe or Fe3C) of the iron nanowires, which can be controlled by the amount of the ferrocene supplied during CVD.

Sato, Hideki; Nagata, Atsushi; Kubonaka, Nobuo; Fujiwara, Yuji

2013-11-01

267

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

PubMed

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

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

2010-11-14

268

Improvements of magnetic properties of Sr ferrite magnets by substitutions of La and Co  

SciTech Connect

Recently, it is intensively required to improve the magnetic properties of Sr ferrite magnets in order to decrease the weight of motors used in automobiles and to improve the efficiency of motors used in electric appliances such as air conditioners. The effect of the simultaneous partial substitution of Co{sup 2+} for Fe{sup 3+} and of La{sup 3+} for Sr{sup 2+} ion in Sr ferrite on the magnetic properties of anisotropic Sr ferrite magnets was investigated. It was found that the coercive force of Sr ferrite magnets is increased without significant decrease in residual flux density by La-Co substitution. Temperature coefficients of coercive force were found to be also improved by La-Co substitution.

Ogata, Yasunobu; Kubota, Yutaka; Takami, Takashi; Tokunaga, Masaaki; Shinohara, Tadashi

1999-09-01

269

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

PubMed

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

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

2014-10-01

270

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

271

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

E-print Network

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

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

2014-09-24

272

Magnetic properties of Ni-implanted ITO thin films  

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

273

Magnetic and Transport Properties of FeAs Single Crystals  

NASA Astrophysics Data System (ADS)

Magnetic susceptibility and transport properties of an itinerant helimagnet FeAs are studied in single-crystalline samples of this binary compound. A kink due to the magnetic transition is observed in the temperature dependences of both the susceptibility and the resistivity. The Hall coefficient shows a reentrant sign change with temperature, signifying a complicated competition between multiple bands. In the helical ordered state, we found an unexpected formation of some anisotropic antiferromagnetic domains, which is reflected in a spin-glass like behavior observed only in the c-axis magnetic susceptibility.

Segawa, Kouji; Ando, Yoichi

2009-10-01

274

Magnetic properties of a single transverse Ising ferrimagnetic nanoparticle  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

275

Some properties of the circular waveguide with azimuthally magnetized ferrite  

Microsoft Academic Search

A comprehensive analysis of normal rotationally symmetric TE modes in a circular waveguide, filled with ferrite, magnetized azimuthally to remanence by a coaxial switching conductor of finite radius, is presented. The characteristic equation of the structure, derived in terms of Kummer and Tricomi confluent hypergeometric functions of complex parameter and variable, is solved numerically, using specially compiled tables of wave

Kamen P. Ivanov; Georgi N. Georgiev

1990-01-01

276

Spectral, thermal and electrical properties of some new azo complexes  

NASA Astrophysics Data System (ADS)

Cobalt(II), nickel(II) and copper(II) acetates react with thymine compound (H 2L) to form complexes having the general formula [MH 2L(OAC) 2(H 2O) 2] nH 2O. However, the interaction of iron(III) chloride with thymine in acetic acid-water medium yields a new complex of the type [FeH 2L(OAC) 2H 2O]OAC.H 2O. All the thymine complexes have been characterized by elemental analyses, spectral and magnetic studies where thymine acts as a neutral ligand and the acetate ion behaves as a strong nucleophile during complexation. 6-aryl and thiazolylazo thymine compounds and their metal complexes were synthesized and characterized where the ligands act as a bidentate dibasic. The azo group is not involved in the structure. Thermal decomposition studies of the azo complexes were explained to give more information on the structure of the investigated materials. The effect of some transition metal cations such as Co II, Ni II and Cu II on the electrical behaviour of 6-(2-thiazolylazo)thymine compound is studied. The data obtained obeyed the relation ?= ?° exp (- E/2 kT) over the temperature range 30-150°C. The observed conductivities of the different complexes follow the order Cocomplexes. The calculated mobility of charge carriers is ranged from 10 -5 to 10 -9cm 2/V s suggesting that the conduction of the studied complexes takes place by hopping mechanism.

Zaki, Zenat M.

2000-09-01

277

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

278

Synthesis, molecular structure and magnetic properties of a rhenium(IV) compound with catechol  

NASA Astrophysics Data System (ADS)

A novel Re(IV) complex containing catechol as ligand has been prepared and characterized. The crystal structure of (HNEt 3)(NBu 4)[ReCl 4(cat)]·H 2cat was determined. The rhenium ion presents a distorted octahedral geometry, being bonded to a bidentate catecholate group and four chloride anions. The magnetic properties of the complex were studied, a /2 D/ (the energy gap between ±3/2 and ±1/2 Kramers doublets) value of 190(10) cm -1. This is the largest /2 D/ value reported for Re(IV) up to now.

Cuevas, A.; Geis, L.; Pintos, V.; Chiozzone, R.; Sanchíz, J.; Hummert, M.; Schumann, H.; Kremer, C.

2009-03-01

279

Syntheses and Magnetic Properties of Dye Included Organometallic Magnets: DAMS[MCr(ox)3  

Microsoft Academic Search

A series of dye-included metal complex-based magnets, DAMS[MCr (ox)3] (DAMS = 4-[2-(4-dimethylaminophenyl)ethenyl]-l-methylpyridinium cation; M=Mn, Fe, Ni; ox =Oxalate Ion), were synthesized. In these compounds different kinds of metal cations are bridged to each other by ox- ions. The compounds have a layered-structure and molecules of DAMS are enclathrated between the layers. Field-cooled magnetization (FCM) measurement showed that these compounds exhibit

Zhongze Gu; O. Sato; T. Iyoda; K. Hashimoto; A. Fujishima

1996-01-01

280

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

SciTech Connect

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

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

2014-05-07

281

Magnetic properties of xenoliths from Yakut kimberlite pipes  

NASA Astrophysics Data System (ADS)

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

Tselebrovskiy, Alexey; Maksimochkin, Valeriy

2014-05-01

282

Magnetic resonance properties of some lunar material.  

PubMed

Paramagnetic resonance spectra of Apollo 11 fines and rocks were measured at 9 and 35 gigahertz and at 4 degrees , 80 degrees , and 300 degrees K. At both frequencies the material has an intense absorption at g = 2, with a line width of approximately 950 gauss. Fe ions with strong exchange interactions produce this resonance. A comparison of the resonance absorption due to Fe(3+) showed that the energy of the crystal field interaction was approximately 0.1 per centimeter. Mn(2+) was identified in several samples, and an absorption at g = 1.89 was tentatively attributed to Ti(3+). The nuclear magnetic resonance spectra of (27)Al had a distribution of asymmetry parameters eta ranging from 0.25 to 0.75 and had nuclear quadrupole coupling constants e(2)qQ/h of approximately 3 megahertz. PMID:17781555

Weeks, R A; Chatelain, A; Kolopus, J L; Kline, D; Castle, J G

1970-01-30

283

Microstructure and magnetic properties of soft magnetic powder cores of amorphous and nanocrystalline alloys  

NASA Astrophysics Data System (ADS)

With the development of modern ferromagnetic technology, soft magnetic powder cores (MPCs) of amorphous and nanocrystalline alloys have been intensively studied for their excellent soft magnetic properties such as high flux density, low coercivity and reduced core loss due to amorphous state and nanocrystalline grains of 10-20 nm dispersed in a residual amorphous matrix. In this paper, the microstructures and soft magnetic properties, i.e., maximum magnetic induction Bm, effective permeability ?e, DC-bias properties and volume power losses PCV of MPCs made from amorphous powder of gas atomization and nanocrystalline powder of pulverized melt-spun ribbon were investigated and also compared on the basis of the same level of ?e. It is found that ?e of both kinds of MPC keeps unchanged up to 1 MHz. The amorphous MPC has lower PCV at lower frequency range, while the nanocrystalline MPC has lower PCV at high frequency range instead. Also, the nanocrystalline MPC has better DC-bias property. Moreover, the DC magnetic properties and the changes of PCV of both MPCs with frequency and flux density are also studied. Furthermore, the electromagnetic characteristics, the microstructures and the mechanisms accounting for these phenomena of both MPCs are also discussed.

Liu, Yapi; Yi, Yide; Shao, Wei; Shao, Yanfang

2013-03-01

284

Magnetism in Complex Oxides Probed by Magnetocaloric Effect and Transverse Susceptibility  

NASA Astrophysics Data System (ADS)

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

Bingham, Nicholas S.

285

On the Effective Magnetic Properties of Magnetorheological Fluids \\Lambda  

E-print Network

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

286

Hard X-ray properties of magnetic cataclysmic S. Scaringi  

E-print Network

, Roma, Italy Abstract. We have constructed a new sample of magnetic cataclysmic variables (mCVs CVs and included mCVs observed with either Swift/BAT or SUZAKU/HXD. Here we review the properties arising from this hard X-ray selected sample and find that most hard X-ray detected mCVs have Pspin

Norton, Andrew J.

287

Spectra and magnetic properties of large spins in external fields  

E-print Network

of Physics, Texas A & M University 2Landau Institute for Theoretical Physics, ~Received 24 Decembe Spectra and magnetic properties of large spins J ~e.g. crystal electric field ~CEF! of an arbitrary symmetry changes by 1/2 or 1. At a fixed field symmetry...

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

1999-01-01

288

In Brief: Magnetic properties database; Inquiry into Beagle 2[  

NASA Astrophysics Data System (ADS)

The National Aeronautic and Space Administration and the U.S. Geological Survey are teaming up to create one of the most complete data bases of magnetic properties of Earth's lithosphere ever assembled. A commission of inquiry into the failure of the Beagle 2 Mars lander last December, led by the inspector general of the European Space Agency, released its findings on 24 May.

Jacobs, Judith

2004-06-01

289

Transport properties of graphene under periodic and quasiperiodic magnetic superlattices  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

290

Magnetic property improvement of niobium doped with rare earth elements  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

291

Magnetic properties of tephras from Lake Van (Eastern Turkey)  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

292

Magnetic properties prediction of NdFeB magnets by using support vector regression  

NASA Astrophysics Data System (ADS)

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

Cheng, Wende

2014-09-01

293

Magnetic properties of obliquely evaporated Co thin films  

NASA Astrophysics Data System (ADS)

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

Kharmouche, Ahmed

2014-10-01

294

Low-Temperature Magnetic Properties of Pyrochlore Stannates  

NASA Astrophysics Data System (ADS)

We report the magnetic properties of pyrochlore rare earth oxides R2Sn2O7 (R=Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm and Yb). The magnetic susceptibility has been measured at temperatures down to 0.1 K. Among them, some compounds show the magnetic anomaly below 1 K. Nd2Sn2O7 and Gd2Sn2O7 show an antiferromagnetic ordering at 0.9 K and 1.0 K, respectively. Tb2Sn2O7 shows a ferromagnetic ordering at 0.87 K. Although both Er3+ and Yb3+ are a Kramers ion, no magnetic anomaly is observed at least down to 0.15 K. We found that Dy2Sn2O7 and Ho2Sn2O7 show ‘spin ice’ behavior. In addition, it is suggested that Pr2Sn2O7 is a new spin ice compound.

Matsuhira, Kazuyuki; Hinatsu, Yukio; Tenya, Kenichi; Amitsuka, Hiroshi; Sakakibara, Toshiro

2002-06-01

295

Magnetic properties of submicrometric antidot arrays in cobalt films  

NASA Astrophysics Data System (ADS)

Arrays of elliptical and square shaped submicrometric antidots were successfully prepared in a continuous cobalt layer using a technique combining electron beam lithography and ion beam etching. Their dynamic magnetic properties were investigated using Brillouin light scattering (BLS) spectroscopy. The BLS results are interpreted with the help of a semi quantitative model taking account of the demagnetizing field arising from the antidots array. In addition, we present magnetic force microscopy (MFM) images showing magnetic domains connecting each square antidot to its neighbours: this indicates that the antidots behave as pinning sites for domain walls through the whole patterned array. The MFM observations are compared to the magnetic topography calculated using the public OOMMF code.

Chérif, S.-M.; Roussigné, Y.; Moch, P.

2006-09-01

296

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

SciTech Connect

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

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

2014-01-01

297

Magnetic properties of HITPERM ,,Fe,Co...88Zr7B4Cu1 magnets M. A. Willard,a)  

E-print Network

composition Fe, Co ­M­B­Cu where M Zr, Hf, Nb, etc. have been named HITPERM. They offer large magnetic inductions and excellent soft magnetic properties at elevated temperatures. Thermomagnetic properties power applications requires new bulk soft magnetic materials that 1 are capable of operating at higher

Laughlin, David E.

298

Preparation and Properties of Various Magnetic Nanoparticles  

PubMed Central

The fabrications of iron oxides nanoparticles using co-precipitation and gadolinium nanoparticles using water in oil microemulsion method are reported in this paper. Results of detailed phase analysis by XRD and Mössbauer spectroscopy are discussed. XRD analysis revealed that the crystallite size (mean coherence length) of iron oxides (mainly ?-Fe2O3) in the Fe2O3 sample was 30 nm, while in Fe2O3/SiO2 where the ?-Fe2O3 phase dominated it was only 14 nm. Gd/SiO2 nanoparticles were found to be completely amorphous, according to XRD. The samples showed various shapes of hysteresis loops and different coercivities. Differences in the saturation magnetization (MS) correspond to the chemical and phase composition of the sample materials. However, we observed that MS was not reached in the case of Fe2O3/SiO2, while for Gd/SiO2 sample the MS value was extremely low. Therefore we conclude that only unmodified Fe2O3 nanoparticles are suitable for intended biosensing application in vitro (e.g. detection of viral nucleic acids) and the phase purification of this sample for this purpose is not necessary. PMID:22574017

Drbohlavova, Jana; Hrdy, Radim; Adam, Vojtech; Kizek, Rene; Schneeweiss, Oldrich; Hubalek, Jaromir

2009-01-01

299

Structural and Magnetic Properties of Codoped ZnO based Diluted Magnetic Semiconductors  

Microsoft Academic Search

Zn1-xCoxO (x = 0.01, 0.02, 0.05, 0.10 and 0.20) diluted magnetic semiconductors are prepared by the sol-gel method. The structural and magnetic properties of the samples are studied using x-ray diffraction (XRD), extended x-ray absorption fine structure (EXAFS) and superconducting quantum interference device (SQUID). The XRD patterns does not show any signal of precipitates that are different from wurtzite type

Bin-Bin Li; Hong-Lie Shen; Rong Zhang; Xiang-Qiang Xiu; Zhi Xie

2007-01-01

300

Magnetic properties of the anisotropic MnBi/Sm2Fe17Nx hybrid magnet  

NASA Astrophysics Data System (ADS)

In order to improve the magnetic properties of MnBi compound, anisotropic MnBi/Sm2Fe17Nx hybrid magnet was prepared by grinding of high purity MnBi ribbons and Sm2Fe17Nx particles together. The smooth hysteresis loops of the hybrid magnets indicated that the mixture of the hard/hard phase magnetic components was well exchange coupled. As compared to the single MnBi phase magnet, the remanent magnetization and maximum energy product (BH)max of the composited magnets were improved. As an optimized result, the exchange coupled magnet of MnBi/Sm2Fe17Nx = 3/7 yielded both high remanence and coercivity from 250 K to 380 K. A maximum energy product (BH)max of 18 MGOe was achieved at 300 K, and remained 10 MGOe at 380 K, implying the MnBi/Sm2Fe17Nx magnets can be specially utilized in the high temperature environment.

Yang, Y. B.; Wei, J. Z.; Peng, X. L.; Xia, Y. H.; Chen, X. G.; Wu, R.; Du, H. L.; Han, J. Z.; Wang, C. S.; Yang, Y. C.; Yang, J. B.

2014-05-01

301

Chemical tuning of the magnetic relaxation in dysprosium(iii) mononuclear complexes.  

PubMed

A dysprosium(iii) complex, exhibiting slow relaxation of magnetization, was prepared. Crystallographic studies showed a perturbation of local symmetry upon deprotonation of the ligand, with concomitant faster relaxation of magnetization. This was attributed to a large shift in the direction of the main magnetic axis, as indicated by ab initio calculations. PMID:24827003

Batchelor, Luke J; Cimatti, Irene; Guillot, Régis; Tuna, Floriana; Wernsdorfer, Wolfgang; Ungur, Liviu; Chibotaru, Liviu F; Campbell, Victoria E; Mallah, Talal

2014-08-28

302

Magnetorheological properties of a magnetic nanofluid with dispersed carbon nanotubes  

NASA Astrophysics Data System (ADS)

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

Felicia, Leona J.; Philip, John

2014-02-01

303

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

SciTech Connect

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

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

2010-07-15

304

Magnetorheological properties of a magnetic nanofluid with dispersed carbon nanotubes.  

PubMed

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

Felicia, Leona J; Philip, John

2014-02-01

305

Electronic Properties of a Square Lattice in a Periodically Modulated Magnetic Field  

NASA Astrophysics Data System (ADS)

Electronic properties of quantum-dot systems are of great current interest. For a quantum dot array forming a simple square lattice of lattice constant a and with one electron on each dot, the electron motion can be regarded as strongly localized on the lattice sites. The energy spectrum of these two-dimensional lattice electrons under a constant magnetic field exhibit complex self-similarity and Cantor-set-like structure as a function of magnetic field, with rather interesting topological properties. The system is known as a quantum fractal system. In this work we consider such a quantum dot system under a periodic magnetic field with a period b. We have solved the eigenvalue problem of the electrons in this system. It is found that the energy spectrum is strongly dependent on the ratio ?=a/b. For odd fraction of ?, there is an additional energy branch with narrow bandwidth. The calculated eigenvalues and eigenvectors are then employed to calculate the static magnetoconductivity ?_xx and ?_yy. The conductivity exhibits fast quasiperiodic quantum magnetic oscillations, reflecting the complex nature of the energy band structure and population of these bands.

Zhang, Chao; Gumbs, Godfrey

2000-03-01

306

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

PubMed

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

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

2012-01-01

307

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

PubMed Central

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

2012-01-01

308

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

PubMed Central

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

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

2014-01-01

309

Magnetic and Electronic Properties of Heusler Alloy Films Investigated by X-Ray Magnetic Circular Dichroism  

Microsoft Academic Search

We have investigated the magnetic properties of epitaxial Heusler alloy films using x-ray absorption spectroscopy (XAS) and\\u000a x-ray magnetic circular dichroism?dex{x-ray!magnetic circular dichroism} (XMCD) in the transmission (TM) and in the surface\\u000a sensitive total electron yield (TEY) mode. We have investigated Ni_2MnGa based shape memory alloys and half-metallic Co2Cro.6Feo.4 films. Single crystalline Ni2MnGa(110)\\/Al2O3(1120) and Ni2MnGa(100)\\/MgO(100) films show a martensitic transition

Hans-Joachim Elmers; Andres Conca; Tobias Eichhorn; Andrei Gloskovskii; Kerstin Hild; Gerhard Jakob; Martin Jourdan; Michael Kallmayer

2009-01-01

310

Rational synthesis and magnetic properties of a family of low-dimensional heterometallic Cr-Mn complexes based on the versatile building block [Cr(2,2'-bipyridine)(CN)4]-.  

PubMed

Six heterometallic compounds based on the building block [Cr(bpy)(CN)4]- (bpy = 2,2'-bipyridine) with secondary and/or tertiary coligands as modulators, {Mn(H2O)2[Cr(bpy)(CN)4]2}n (1), {Mn(bpy)(H2O)[Cr(bpy)(CN)4]2 x H2O}n (2), [Mn(bpy)2][Cr(bpy)(CN)4]2 x 5H2O (3), {[Mn(dca)(bpy)(H2O)][Cr(bpy)(CN)4] x H2O}n (4) (dca = N(CN)2(-)), {Mn(N3)(CH3OH)[Cr(bpy)(CN)4] x 2H2O}n (5), and {Mn(bpy)(N3)(H2O)[Cr(bpy)(CN)4] x H2O}2 (6), have been prepared and characterized structurally and magnetically. X-ray crystallography reveals that the compounds 1, 2, 4, and 5 consist of one-dimensional (1D) chains with different structures: a 4,2-ribbon-like chain, a branched zigzag chain, a 2,2-CC zigzag chain, and a 3,3-ladder-like chain, respectively. It also reveals that compound 3 has a trinuclear [MnCr2] structure, and compound 6 has a tetranuclear [Mn2Cr2] square structure. Magnetic studies show antiferromagnetic interaction between Cr(III) and Mn(II) ions in all compounds. All of the chain compounds exhibit metamagnetic behaviors with different critical temperatures (Tc) and critical fields (Hc; at 1.8 K): 3.2 K and 3.0 kOe for 1; 2.3 K and 4.0 kOe for 2; 2.1 K and 1.0 kOe for 4; and 4.7 K and 5.0 kOe for 5, respectively. The noncentrosymmetric compound 2 is also a weak ferromagnet at low temperature because of spin canting. The magnetic analyses reveal Cr-Mn intermetallic magnetic exchange constants, J, of -4.7 to -9.4 cm(-1) (H = -JS(Cr) x S(Mn)). It is observed that the antiferromagnetic interaction through the Mn-N-C-Cr bridge increases as the Mn-N-C angle (theta) decreases to the range of 155-180 degrees, obeying an empirical relationship: J = -40 + 0.2theta. This result suggests that the best overlap between t(2g) (high-spin Mn(II)) and t(2g) (low-spin Cr(III)) occurs at an angle of approximately 155 degrees. PMID:15962960

Zhang, Yuan-Zhu; Gao, Song; Wang, Zhe-Ming; Su, Gang; Sun, Hao-Ling; Pan, Feng

2005-06-27

311

Coagulation property of hyaluronic acid–collagen\\/chitosan complex film  

Microsoft Academic Search

Biomacromolecule has been widely used as biomedical material. Because different biomacromolecules possess different properties,\\u000a how to exhibit the respective advantages of different components on one type of biomaterial becomes the hot spot in the field\\u000a of biomaterial studying. This work reported a type of complex film that consisted of hyaluronic acid (HA), type I collagen\\u000a (Col-I), and chitosan (CS) (HA–Col-I\\/CS,

Yangzhe Wu; Yi Hu; Jiye Cai; Shuyuan Ma; Xiaoping Wang

2008-01-01

312

The role of unintentional hydrogen on magnetic properties of Co doped ZnO  

NASA Astrophysics Data System (ADS)

The correlation between the positioning of hydrogen and magnetic properties of Co doped ZnO are investigated using ab initio methodology. It is found that hydrogen can both sit in interstitial Zn-O mid bonds and substitute oxygen forming multicentre bonds with zinc. However the substitutional hydrogen is slightly more stable by 0.37 eV than the interstitial hydrogen. It is also found that mobile hydrogen ions in ZnO are trapped by Co ions or Co complexes to form variety of highly stable Co-H complexes in ZnO host lattice. Charge transfer from hydrogen to neighboring Co's 3d orbitals leads to both the stabilization of ferromagnetic ordering among Co ions and the reduction of Co ion magnetic moment.

Assadi, M. H. N.; Zhang, Y. B.; Li, S.

2011-12-01

313

Magnetic antenna excitation of whistler modes. I. Basic properties  

NASA Astrophysics Data System (ADS)

Properties of magnetic loop antennas for exciting electron whistler modes have been investigated in a large laboratory plasma. The parameter regime is that of large plasma frequency compared to the cyclotron frequency and signal frequency below half the cyclotron frequency. The antenna diameter is smaller than the wavelength. Different directions of the loop antenna relative to the background magnetic field have been measured for small amplitude waves. The differences in the topology of the wave magnetic field are shown from measurements of the three field components in three spatial directions. The helicity of the wave magnetic field and of the hodogram of the magnetic vector in space and time are clarified. The superposition of wave fields is used to investigate the properties of two antennas for small amplitude waves. Standing whistler waves are produced by propagating two wave packets in opposite directions. Directional radiation is obtained with two phased loops separated by a quarter wavelength. Rotating antenna fields, produced with phased orthogonal loops at the same location, do not produce directionality. The concept of superposition is extended in a Paper II to generate antenna arrays for whistlers. These produce nearly plane waves, whose propagation angle can be varied by the phase shifting the currents in the array elements. Focusing of whistlers is possible. These results are important for designing antennas on spacecraft or diagnosing and heating of laboratory plasmas.

Urrutia, J. M.; Stenzel, R. L.

2014-12-01

314

Axisymmetric Flow Properties for Magnetic Elements of Differing Strength  

NASA Technical Reports Server (NTRS)

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

Rightmire-Upton, Lisa; Hathaway, David H.

2012-01-01

315

Anisotropy of magnetic properties of Fe1+yTe  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

316

Anisotropy of magnetic properties of Fe(1+y)Te.  

PubMed

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

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

2014-10-29

317

Properties of the manganese(II) binding site in ternary complexes of Mnter dot ADP and Mnter dot ATP with chloroplast coupling factor 1: Magnetic field dependence of solvent sup 1 H and sup 2 H NMR relaxation rates  

SciTech Connect

The influence of the binding of ADP and ATP on the high-affinity Mn(II) binding site of chloroplast coupling factor 1 (CF{sub 1}) was studied by analysis of field-dependent solvent proton and deuteron spin-lattice relaxation data. In order to characterize metal-nucleotide complexes of CF{sub 1} under conditions similar to those of the NMR experiments, the enzyme was analyzed for bound nucleotides and Mn(II) after incubation with AdN and MnCl{sub 2} and removal of labile ligands by extensive gel filtration chromatography. In the field-dependent NMR experiments, the Mn(II) binding site of CF{sub 1} was studied for three mole ratios of added Mn(II) to CF{sub 1}, 0.5, 1.0, and 1.5, in the presence of an excess of either ADP or ATP. The results were extrapolated to zero Mn(II) concentration to characterize the environment of the first Mn(II) binding site of Cf{sub 1}. In the presence of both adenine nucleotides, pronounced changes in the Mn(II) environment relative to that in Mn(II)-CF{sub 1} were evident; the local relaxation rate maxima were more pronounced and shifted to higher field strengths, and the relaxation rate per bound Mn(II) increased at all field strengths. Analysis of the data revealed that the number of exchangeable water molecules liganded to bound Mn(II) increased from one in the binary Mn(II)-CF{sub 1} complex to three and two in the ternary Mn(II)-ADP-CF{sub 1} and Mn(II)-ATP-CF{sub 1} complexes, respectively; these results suggest that a water ligand to bound Mn(II) in the Mn(II)-ADP-CF{sub 1} complex is replaced by the {gamma}-phosphate of ATP in the Mn(II)-ATP-CF{sub 1} complex. A binding model is presented to account for these observations.

Haddy, A.E.; Frasch, W.D.; Sharp, R.R. (Univ. of Michigan, Ann Arbor (USA))

1989-05-02

318

Magnetic properties of bio-synthesized zinc ferrite nanoparticles  

SciTech Connect

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

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

2011-01-01

319

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

NASA Astrophysics Data System (ADS)

Magnetic properties of chemical vapour deposited (CVD) Fe3O4 and ?-Fe2O3 obtained by co-pyrolysis of ferric and cobaltus acetyl acetonate complexes are described. Saturation magnetization, remanent magnetization and coercivity value of 3.7 kG, 2.2 kG and 820 Oe respectively have been obtained for Co-? Fe2O3 films. Chemically vapour deposited Co-Fe3O4 films are laterally inhomogeneous with only a fraction of Co2+ ions at octahedral sites (B sites) of spinnel ferrite and excess Co2+ ions distributed in the interstitial matrix. Oxidation conversion to ?-Fe2O3 phase at temperatures above 350°C lead to Co2+ ion diffusion to B sites with activation energy of 0.27 eV. Consequent increase in magneto-crystalline anisotropy results in considerable enhancement in coercivity.

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

1992-12-01

320

Magnetic properties, crystal and molecular stucture of (NBu 4) 2[ReCl 4(ox)  

NASA Astrophysics Data System (ADS)

The synthesis, structure and magnetic properties of the rhenium(IV) complex (NBu 4) 2[ReCl 4(ox)] is reported. The crystal and molecular structure (NBu 4) 2[ReCl 4(ox)] has been solved by the heavy atom method and refined anisotropically to R1=0.049 for 5636 unique observed reflections. The title compound crystallizes in the monoclinic space group P21/ n with Z=4. The Re atom is of six-coordinate distorted octahedral configuration being bonded to one bidentate oxalate group and four chloride anions. The asymmetric unit contains one [ReCl 4(ox)] - 2 anion and two [NBu 4] + cations. The magnetic behavior of (NBu 4) 2[ReCl 4(ox)] has been investigated over the temperature range 1.72-300 K. This measurement revealed that examined compound is magnetically diluted with the great value of zero-field splitting parameter D=53 cm-1.

Tomkiewicz, A.; Bartczak, T. J.; Kruszy?ski, R.; Mrozi?ski, J.

2001-09-01

321

Magnetic properties of the molecular nanomagnet Cr7Cd: single ion and exchange anisotropy effects.  

PubMed

In order to verify two microscopic models of the molecular nanomagnet Cr7Cd we analyze a number of thermodynamic quantities calculated for two sets of parameters. The first model, with only single ion anisotropy, was established on the basis of the thermodynamic properties (by fitting susceptibility and magnetization) whereas the second, with single ion and bond-dependent exchange anisotropies, was based on the inelastic neutron scattering and EPR spectra. The calculations are performed by means of non-perturbative, numerically exact quantum transfer matrix technique on large scale parallel computers. We demonstrate that the predictions of the models are consistent in the region of small magnetic fields which do not exceed 10 T and differ significantly in higher fields. Comparison with the experiment leads to a conclusion that better modeling of magnetic torque requires more complex microscopic model with single ion and bond-dependent exchange anisotropies. PMID:22400319

Koz?owski, P; Kamieniarz, G

2011-10-01

322

Magnetic properties of magnetically soft nanocomposite Co-SiO2 prepared via mechanical milling.  

PubMed

Nanocomposite of Co-SiO2, a soft magnetic material, with Co weight fraction x = 0.3 and 0.7 was prepared via mechanical milling. The magnetic properties of these samples, both zero-field-cooled (ZFC) and field-cooled (FC), have been measured as a function of x, milling time, and temperature. The structural assessment of the composite indicates a presence of only ferromagnetic (FM) hcp-Co phase in the composite. However, reported magnetic properties of these composites appear to be dependent on the presence of antiferromagnetic (AFM) phases of cobalt oxide as well. The observed enhancement in ZFC coercivity and a reduction in saturation magnetization with the milling time are due to an increase in defect density upon milling. The ZFC coercivity for the x = 0.3 samples has been found to be much higher than the x = 0.7 samples for all milling times. The coercivity above 50 K depends on temperature according to the law corresponding to isotropic uniaxial superparamagnetic particles. Below 50 K the presence of an AFM phase Co3O4 (TN approximately 33 K) and increased interparticle interactions bring in a departure from that law. The saturation magnetization is found to be temperature dependent for the x = 0.3 samples and temperature independent for the x = 0.7 samples, which further provides evidence of the presence of higher AFM phase fraction in the composite with a low metal volume fraction. The FC magnetic measurements show a presence of an exchange bias field and an enhanced coercivity which are higher than the ZFC measurements. All magnetic measurements indicate that the overall magnetic properties of the composite are dictated by the presence of a trace amount of cobalt oxides. PMID:16430144

Mishra, S R; Dubenko, I; Losby, J; Marasinghe, K; Ali, Mehdi; Ali, N

2005-12-01

323

Aging of magnetic properties in MgO films  

SciTech Connect

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

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

2010-12-20

324

Hydrothermal synthesized bismuth ferrites particles: thermodynamic, structural, and magnetic properties.  

PubMed

A family of bismuth ferrites (BFO), including Bi2Fe4O9, BiFeO3, and Bi25FeO39 with different morphologies, has been prepared by the hydrothermal method assisted by different alkaline mineralizers. X-ray diffraction refinement calculations are carried out to study the crystal structures of bismuth ferrites. A thermodynamic calculation based on the dissolution-precipitation model was carried out to analyze the hydrothermal synthesis of BFO powders. Magnetic measurements of the obtained bismuth ferrites show different magnetic properties from 5 K to 350 K. PMID:22630029

Du, Yi; Cheng, Zhenxiang; Yu, Zhenwei; Dou, Shi Xue; Wang, Xiaolin; Liu, L Q

2012-02-01

325

Magnetic properties of mixed cobalt–zinc ferrite nanoparticles  

Microsoft Academic Search

Solid solutions of nonstoichiometric mixed cobalt–zinc ferrite nanoparticles Co0.73yZn0.73(1?y)Fe2.18□0.09O4, were prepared in order to study their magnetic properties as a function of cobalt content y. The saturation magnetization changes with increasing y due to the various occupancies of cations in tetrahedral and octahedral sites and\\/or to an increase in the disorder of the ferrimagnetic structure. The cobalt content and particle

J. F. Hochepied; M. P. Pileni

2000-01-01

326

Magnetic properties of mixed cobalt-zinc ferrite nanoparticles  

Microsoft Academic Search

Solid solutions of nonstoichiometric mixed cobalt-zinc ferrite nanoparticles Co0.73yZn0.73(1-y)Fe2.18□0.09O4, were prepared in order to study their magnetic properties as a function of cobalt content y. The saturation magnetization changes with increasing y due to the various occupancies of cations in tetrahedral and octahedral sites and\\/or to an increase in the disorder of the ferrimagnetic structure. The cobalt content and particle

J. F. Hochepied; M. P. Pileni

2000-01-01

327

Synthesis, crystal structure and study of magnetocaloric effect and single molecular magnetic behaviour in discrete lanthanide complexes.  

PubMed

The synthesis, crystal structure and magnetic properties of four polynuclear lanthanide coordination complexes having molecular formulae, [Gd3(2)(1)L(H2O)8(Cl)](Cl)4·10H2O (1), [Dy3L(2)(1)(H2O)9](Cl)5·6H2O (2) [Gd6L(2)(2)(HCO2)4(?3-OH)4(DMF)6(H2O)2](Cl)2·4H2O (3) and [Dy6L(2)(2)(HCO2)4(?3-OH)4(DMF)6(H2O)2](Cl)2·4H2O (4) (where H2L(1) = bis[(2-pyridyl)methylene]pyridine-2,6-dicarbohydrazide and H4L(2) = bis[2-hydroxy-benzylidene]pyridine-2,6-dicarbohydrazide) are reported. Structural investigation by X-ray crystallography reveals similar structural features for complexes 1 and 2 and they exhibit butterfly like shapes of the molecules. Non-covalent interactions between the molecules create double helical arrangements for both molecules. Complexes 3 and 4 are isostructural and the core structures feature four distorted hemi-cubanes connected by vertex sharing. Magnetic studies unveil significant magnetic entropy changes for complexes 1, 3 and slow relaxation of magnetization for both dysprosium analogues 2 and 4. PMID:24818564

Adhikary, Amit; Sheikh, Javeed Ahmad; Biswas, Soumava; Konar, Sanjit

2014-06-28

328

Synthesis, characterization and magnetic properties of carbon nanotubes decorated with magnetic MIIFe2O4 nanoparticles  

NASA Astrophysics Data System (ADS)

In this study, a simple, efficient and reproducible microemulsion method was applied for the successful decoration of carbon nanotubes (CNTs) with magnetic MIIFe2O4 (M = Co, Ni, Cu, Zn) nanoparticles. The structure, composition and morphology of the prepared nanocomposite materials were characterized using X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The magnetic properties were investigated by the vibrating sample magnetometer (VSM). The SEM results illustrated that large quantity of MIIFe2O4 nanoparticles were uniformly decorated around the circumference of CNTs and the sizes of the nanoparticles ranged from 15 to 20 nm. Magnetic hysteresis loop measurements revealed that all the MIIFe2O4/CNTs nanocomposites displayed ferromagnetic behavior at 300 K and can be manipulated using an external magnetic field. The CoFe2O4/CNTs nanocomposite showed maximum value of saturation magnetization which was 37.47 emu g-1. The as prepared MIIFe2O4/CNTs nanocomposites have many potential application in magnetically guided targeted drug delivery, clinical diagnosis, electrochemical biosensing, magnetic data storage and magnetic resonance imaging.

Ali, Syed Danish; Hussain, Syed Tajammul; Gilani, Syeda Rubina

2013-04-01

329

Magnetic and Electronic Properties in Rattling Systems, an Experimental and Theoretical Study  

E-print Network

several ab-initio models have been considered to understand the structural, vibrational and magnetic properties observed in these compounds. Among the studied compounds, the Fe-Al-Zn materials showed interesting magnetic properties combined...

Rodriguez Robles, Sergio

2012-10-19

330

Morphology, magnetic, magnetoresistance and optical properties of Co-Ni-Mo alloys thin films  

NASA Astrophysics Data System (ADS)

We present in this paper several results concerning the preparation by means of electrolysis and characterization of Co-Ni-Mo thin films. Co-Ni-Mo thin films with different molybdenum content in the range 0-25 at% Mo were prepared from a complex solution containing ions of Co, Ni and Mo, using galvanostatic control, on aluminum substrates. The effects of applied current density on the morphology, magnetic, magnetoresistance, and optical properties of the electrodeposited Co-Ni-Mo films were investigated. The applied current density significantly influenced the film composition and their magnetic properties. The increase of molybdenum content in Co-Ni films (up to 25 at% Mo) enhances the resistivity, but it reduces the magnetoresistance effect. We report the first observation of magnetoresistance as high as 8% in Co-Ni-Mo thin films.

Tanase, S. I.; Tanase, D. Pinzaru; Dobromir, M.; Georgescu, V.

2011-10-01

331

Density functional theory calculations on magnetic properties of actinide compounds.  

PubMed

We have performed a detailed analysis of the magnetic (collinear and non-collinear) order and the atomic and electron structures of UO(2), PuO(2) and UN on the basis of density functional theory with the Hubbard electron correlation correction (DFT + U). We have shown that the 3-k magnetic structure of UO(2) is the lowest in energy for the Hubbard parameter value of U = 4.6 eV (and J = 0.5 eV) consistent with experiments when Dudarev's formalism is used. In contrast to UO(2), UN and PuO(2) show no trend for a distortion towards rhombohedral structure and, thus, no complex 3-k magnetic structure is to be anticipated in these materials. PMID:20714591

Gryaznov, Denis; Heifets, Eugene; Sedmidubsky, David

2010-10-14

332

Density functional theory calculations on magnetic properties of actinide compounds  

NASA Astrophysics Data System (ADS)

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

Gryaznov, Denis; Heifets, Eugene; Sedmidubsky, David

333

Transport and magnetic properties of RTX and related compounds  

NASA Astrophysics Data System (ADS)

Physical properties of RTX compounds (R = Rare earth, T = Transition metal and X = main group element from B, C or N group) compounds have been studied by means of electrical resistivity, heat capacity, dc magnetization and NMR. Searching for new magnetic materials is always an interesting topic from both a technological and basic research prospective; it is even more interesting when unusual magnetic phases are observed. Ternary intermetallic plumbides are interesting because of their unconventional magnetic ordering and variety of multiple magnetic transitions. Crystalline electric fields (CEF) also strongly effect the magnetic properties of these intermetallics. To understand the phase transitions, CEF effects, and magnetic interactions, a systematic study of the RNiPb, R 2Ni2Pb, R5NiPb3 and RCuGe systems were conducted. Among the results for NdNiPb a single antiferromagnetic transition was found at 3.5K, while the superconductivity found in some ingots of this material was shown not to correspond to a bulk behavior for this phase. Nd2Ni 2Pb was shown to have a canted zero field magnetic structure with a low temperature metamagnetic transition 3 T. In NdCuGe, a 3K AF transition was found along with a corresponding magnon contribution to the specific heat and magnetic and thermodynamic behavior from which the detailed CEF configuration was obtained. In a series of measurements on recently-synthesized R 5NiPb3 (R=Ce, Nd, Gd), for Ce5NiPb 3 a transition at 48 K was found, which was confirmed to be ferromagnetic character from field dependent heat capacity and Curie-Weiss susceptibility. Nd5NiPb3 exhibits two transitions, an antiferromagnetic transition at 42 K and an apparently weak ferromagnetic canting transition at 8 K. For Gd5NiPb3, a ferro- or ferrimagnetic transition was found at 68 K. For the Ce and Nd materials metamagnetism was also observed at low temperatures. In addition, very large metallic type gamma terms were found in the specific heat, as well as a reduced value of the magnetic entropy, for all three systems. These results imply a lack of ordering for one of the two in-equivalent chains in these materials. This is discussed in terms of possible geometrical frustration on one of the spin chains.

Goruganti, Venkateshwarlu

334

Synthesis and magnetic properties of Fe-Pt-B nanocomposite permanent magnets with low Pt concentrations  

SciTech Connect

Microstructure and magnetic properties of melt-spun Fe{sub 80-x}Pt{sub x}B{sub 20} (x=20,22,24) alloy ribbons have been investigated. A homogeneous nanoscale mixed structure with amorphous and fcc {gamma}-FePt phases was formed in the melt-spun ribbons. The average sizes of the amorphous and fcc {gamma}-FePt phases are about 5 nm, and the enrichment phenomenon of B is recognized in the coexistent amorphous phase. The melt-spun ribbons exhibit soft magnetic properties. The nanocomposite structure consisting of fct {gamma}{sub 1}-FePt, fcc {gamma}-FePt, and Fe{sub 2}B phases was obtained in the melt-spun ribbons annealed at 798 K for 900 s, and their average grain sizes are about 20 nm. The remanence (B{sub r}), reduced remanence (M{sub r}/M{sub s}), coercivity ({sub i}H{sub c}), and maximum energy product (BH){sub max} of the nanocomposite alloys are in the range of 0.93-1.05 T, 0.79-0.82, 375-487 kA/m, and 118-127 kJ/m{sup 3}, respectively. The good hard magnetic properties are interpreted as resulting from exchange magnetic coupling between nanoscale hard fct {gamma}{sub 1}-FePt and soft magnetic fcc {gamma}-FePt or Fe{sub 2}B phases.

Zhang Wei; Louzguine, Dmitri V.; Inoue, Akihisa [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

2004-11-22

335

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

336

Suppression of mitochondrial complex I influences cell metastatic properties.  

PubMed

Despite the fact that mitochondrial dysfunction has an important role in tumorigenesis and metastasis, the underlying mechanism remains to be elucidated. Mitochondrial Complex I (NADH:ubiquinone oxidoreductase) is the first and the largest protein complex of the mitochondrial electron-transport chain (ETC),which has an essential role in maintaining mitochondrial function and integrity. In this study, we separately knocked down two subunits of mitochondrial complex I, GRIM-19 or NDUFS3, and investigated their effects on metastatic behaviors and explored the possible mechanisms. Our data showed that stable down-modulation of GRIM-19 or NDUFS3 decreased complex I activity and reactive oxygen species (ROS) production; led to enhanced cell adhesion, migration, invasion, and spheroid formation; and influenced the expressions of extracellular matrix (ECM) molecules and its related proteins. We also observed that the expressions of GRIM-19, NDUFS3, and ECM elements were correlated with invasive capabilities of breast cancer cell lines. These results suggest that inhibition of complex I affects metastatic properties of cancer cells, and mitochondrial ROS might play a crucial role in these processes by regulating ECM. PMID:23630608

He, Xuelian; Zhou, Aifen; Lu, Hao; Chen, Yong; Huang, Guochang; Yue, Xin; Zhao, Peiwei; Wu, Yanxiang

2013-01-01

337

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

PubMed

The magnetic structure and magnetic transport properties of hydrogen-passivated sawtooth zigzag-edge graphene nanoribbons (STGNRs) are investigated theoretically. It is found that all-sized ground-state STGNRs are ferromagnetic and always feature magnetic semiconductor properties, whose spin splitting energy gap Eg changes periodically with the width of STGNRs. More importantly, for the STGNR based device, the dual spin-filtering effect with the perfect (100%) spin polarization and high-performance dual spin diode effect with a rectification ratio about 10(10) can be predicted. Particularly, a highly effective spin-valve device is likely to be realized, which displays a giant magnetoresistace (MR) approaching 10(10)%, which is three orders magnitude higher than the value predicted based on the zigzag graphene nanoribbons and six orders magnitude higher than previously reported experimental values for the MgO tunnel junction. Our findings suggest that STGNRs might hold a significant promise for developing spintronic devices. PMID:25533701

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

2014-01-01

338

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

339

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

PubMed Central

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

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

2014-01-01

340

Switchable molecular magnets  

PubMed Central

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

SATO, Osamu

2012-01-01

341

UNIVERSITY of CALIFORNIA EFFECT OF BISMUTH DOPING ON THE MAGNETIC PROPERTIES  

E-print Network

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

Belanger, David P.

342

Ferromagnetism of dense matter and magnetic properties of neutron stars  

E-print Network

Possible consequences of ferromagnetic transition in dense matter suggested recently by Kutschera and W{\\'o}jcik, for the magnetic properties of neutron stars, are studied. Specific model of dense matter, in which a small admixture of protons is completely polarized due to their interaction with neutrons, is considered. Magnetic field of neutron stars with a ferromagnetic core is calculated within the framework of general relativity. Two types of boundary conditions at the ferromagnetic core edge are considered, corresponding to normal and superconducting liquid envelope, respectively. Numerical results for the neutron star magnetic dipole moment are confronted with pulsar timing. To be consistent with observations, ferromagnetic cores surrounded by a non-superconducting envelope, should consist of weakly ordered ferromagnetic domains. If domains are highly ordered, ferromagnetic core should be screened by a superconducting envelope.

P. Haensel; S. Bonazzola

1996-05-24

343

Evaluating the effect of magnetocaloric properties on magnetic refrigeration performance  

NASA Astrophysics Data System (ADS)

Active magnetic regenerator (AMR) refrigerators represent an alternative to vapor compression technology that relies on the magnetocaloric effect in a solid refrigerant. Magnetocaloric materials are in development and properties are reported regularly. Recently, there has been an emphasis on developing materials with a high entropy change with magnetization while placing lower emphasis on the adiabatic temperature change. This work uses model magnetocaloric materials and a numerical AMR model to predict how the temperature change and entropy change with magnetization interact and how they affect the performance of a practical system. The distribution of the magnetocaloric effect as a function of temperature was also studied. It was found that the adiabatic temperature change in a magnetocaloric material can be more important than the isothermal entropy change for certain conditions. A material that exhibits a sharp peak in isothermal entropy change was shown to produce a significantly lower cooling power than a material with a wide peak in a practical AMR system.

Engelbrecht, K.; Bahl, C. R. H.

2010-12-01

344

Magnetic properties of superparamagnetic nanoparticles loaded into silicon nanotubes  

PubMed Central

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

2014-01-01

345

Magnetic properties of ion irradiated epitaxial Fe films  

NASA Astrophysics Data System (ADS)

Magnetic properties of a heavy-ion irradiated single crystalline iron film were investigated. A high quality Fe (001) film with a thickness of 250 nm was fabricated on MgO (001) using the molecular beam epitaxy technique. The film was irradiated by 3.2 MeV Ni ions at room temperature using a tandem accelerator. Formation of dislocation loops with nanometer size was observed by TEM observation, and that of sub-nanometer size vacancy clusters was confirmed indirectly from a resistivity increase. However, M-H hysteresis curves and magnetic domain structure did not change significantly. These results indicate the formation of irradiation defects of pure iron in nanometer scale range has little influence on the magnetization process of the iron.

Kamada, Y.; Watanabe, H.; Mitani, S.; Echigoya, J.; Mohapatra, J. N.; Kikuchi, H.; Kobayashi, S.; Takanashi, K.

2011-01-01

346

Magnetic properties of non-stoichiometric Y-type hexaferrite  

NASA Astrophysics Data System (ADS)

The magnetic characterization of Y-type hexaferrites series with Ba 2Zn 0.6Co 0.6Cu 0.8Fe 12- xO 22-1.5 x has been investigated. Y-type polycrystalline hexaferrite powders were prepared by the solid-state reaction method. The samples were characterized by X-ray diffraction and scanning electron microscopy. An investigation of the magnetic permeability over a wide frequency range was done using an impedance analyzer. Experimental results show that cation deficiency leads to a decrease in sintering temperature. It is indicated that Y-type hexaferrite samples with proper cation deficiency sintered at low temperatures possess excellent magnetic properties for application.

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

2002-09-01

347

Magnetic properties of Al/57Fe/Cr multilayers  

NASA Astrophysics Data System (ADS)

Conversion Electron Mössbauer Spectroscopy (CEMS) and DC magnetization are used to compare magnetic properties of as-deposited multilayer (MLS) and Fe2CrAl thin film made from Al/57Fe/Cr MLS deposited by ion beam sputtering and then annealed in UHV. Interdiffusion of elements on annealing sample-1 at 500°C leads to formation of a single, disordered film of Fe2CrAl as evidenced by hyperfine field values obtained by CEMS in the film which compares well with that in bulk Fe2CrAl. CEMS also shows contributions from Fe, Fe/Cr and Fe/Al interfaces in the MLS. Saturation magnetization of as-deposited sample-1 is much less than pure Fe due to reduced Fe thickness because of interface formation and also reduction in Fe-Fe interaction due to intervening Al and Cr layers.

Jani, Snehal; Lakshmi, N.; Jain, Vishal; Reddy, V. R.; Gupta, Ajay; Venugopalan, K.

2013-06-01

348

Discontinuous properties of current-induced magnetic domain wall depinning  

PubMed Central

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

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

2013-01-01

349

Magnetic nanoparticles supported ionic liquids improve firefly luciferase properties.  

PubMed

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

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

2014-03-01

350

Magnetic Properties of Nanocrystalline Nickel-Cobalt Ferrites  

NASA Astrophysics Data System (ADS)

In this study, the nanocrystalline nickel-cobalt ferrites were prepared via the citrate route method at . The samples were calcined at for 3 h. The crystalline structure and the single-phase formations were confirmed by X-ray diffraction (XRD) measurements. Prepared materials showed the cubic spinel structure with m3m symmetry and Fd3m space group. The analyses of XRD patterns were carried out using POWD software. It gave an estimation of lattice constant “” of 8.3584 Å, which was in good agreement with the results reported in JCPDS file no. 742081. The crystal size of the prepared materials calculated by Scherer’s formula was 27.6 nm and the electrical conductivity was around . The permeability component variations with frequency were realized. The magnetic properties of the prepared materials were analyzed by a vibrating sample magnetometer (VSM). It showed a saturation magnetization of and the behavior of a hard magnet.

Tiwari, D. K.; Villaseñor-Cendejas, L. M.; Thakur, A. K.

2013-09-01

351

Magnetic Properties and Hyperfine Interactions in Iron Containing Metallic Glasses  

NASA Astrophysics Data System (ADS)

Amorphous samples of Fe(,x)B(,100-x) (30 (LESSTHEQ) x (LESSTHEQ) 90), Fe(,x)Ag(,100-x) (40 (LESSTHEQ) x (LESSTHEQ) 50), and Fe(,x)Zr(,100-x) (20 (LESSTHEQ) x (LESSTHEQ) 93) have been prepared, and their magnetic properties and hyperfine interactions studied by ('57)Fe Mossbauer spectroscopy. Each system is representative of either Fe-metalloid (Fe-B), Fe-noble metal (Fe-Ag), or Fe-early transition metal (Fe -Zr) amorphous alloys. Therefore, by studying these three amorphous solids an overview is obtained, not only of the properties of the individual alloys, but also of the wider class of alloys of which they are representative. The amorphous Fe-B and Fe-Zr systems have been successfully fabricated over very wide ranges in composition, allowing the evolution of the magnetic properties and hyperfine interactions to be systematically studied. As a result it has been possible to determine the critical concentration for magnetic order (x(,c)). It has been shown that the loss of magnetic order below x(,c) is the result of the reduction and eventual disappearance of the Fe moment. The isomer shifts (IS) and quadrupole splittings (QS) have also been determined over wide composition ranges. This has led to the observation of a maximum in IS with decreasing Fe concentration in amorphous alloys of Fe and B. On the other hand, IS in the amorphous Fe-Zr alloys has been found to decrease monotonically over the same concentration range. In the paramagnetic region all the samples display quadrupole split doublets characteristic of site symmetries lower than cubic. It has been found that the observed asymmetry in the quadrupole spectra can be correlated with the relative changes in IS and QS as a function of composition. Amorphous alloys of Fe and Ag have been prepared for the first time and have been found to be stable at room temperature. The somewhat unusual magnetic properties of these alloys suggests that they may be simpler magnetically than previously studied magnetic amorphous solids. The very existence of this kind of amorphous alloy raises a number of interesting questions on the nature of the amorphous state. Two tests of the quasi-crystalline model have also been undertaken. In the first instance crystalline and amorphous FeB have been directly compared. The quasi -crystalline model cannot account for the significant differences that exist between the amorphous alloy and the crystalline compound. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI.

Unruh, Karl Marlin

352

Magnetic properties and energy absorption of CoFe2O4 nanoparticles for magnetic hyperthermia  

E-print Network

We have studied the magnetic and power absorption properties of three samples of CoFe2O4 nanoparticles with sizes from 5 to 12 nm prepared by thermal decomposition of Fe (acac)3 and Co(acac)2 at high temperatures. The blocking temperatures TB estimated from magnetization M(T) curves spanned the range 180 < TB < 320 K, reflecting the large magnetocrystalline anisotropy of these nanoparticles. Accordingly, high coercive fields HC \\approx 1.4 - 1.7 T were observed at low temperatures. Specific Power Absorption (SPA) experiments carried out in ac magnetic fields indicated that, besides particle volume, the effective magnetic anisotropy is a key parameter determining the absorption efficiency. SPA values as high as 98 W/g were obtained for nanoparticles with average size of \\approx12 nm.

Torres, T E; Morales, M P; Ibarra, A; Marquina, C; Ibarra, M R; Goya, G F; 10.1088/1742-6596/200/7/072101

2011-01-01

353

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

354

Structure and magnetic properties of bulk nanocrystalline SmCo7-xHfx sintered magnets  

NASA Astrophysics Data System (ADS)

The structure and magnetic properties of the bulk nanocrystalline SmCo7-xHfx (x =0,0.1,0.2) magnets prepared using the spark plasma sintering technology were studied. SmCo7-xHfx magnet exhibits a single phase with the TbCu7-type structure. The Rietveld structure refinement results show that Hf prefers to occupy the 1a site, which in turn leads to an enhancement of the anisotropy field of the SmCo7 compounds. Microstructure analysis indicates that the average grains size is about 35nm. With increasing Hf contents from x =0 to 0.2, the coercivity increases from 0.89to2.08T. The coercivity of SmCo6.8Hf0.2 magnet decreases almost linearly from 2.08to0.4T with increasing temperatures from 300to773K.

Zhang, Dongtao; Yue, Ming; Pan, Lijun; Li, Yangchao; Xu, Gang; Liu, Weiqiang; Zhang, Jiuxing; Liu, Xubo; Altounian, Zaven

2008-04-01

355

Physicochemical [corrected] properties of the inclusion complex of puerarin and glucosyl-?-cyclodextrin.  

PubMed

Puerarin is a natural isoflavone, found in the Chinese medicinal plant Ge-gen, with many reported health-promoting properties. However, its low water solubility impedes its application in pharmaceutical and functional food products. This study explores the formation of inclusion complex between puerarin and glucosyl-?-cyclodextrin (G-?-CD) to improve the aqueous solubility of puerarin. The complex was prepared by mixing an equal molar mixture of puerarin and G-?-CD for 24 h, followed by freeze-drying. The obtained complex was analyzed by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, X-ray diffractometry, and proton nuclear magnetic resonance spectroscopy. Results showed clearly that the process led to the formation of a supramolecular complex in which the guest molecule, puerarin, was entrapped inside the cavity of the host, G-?-CD. The close association between puerarin and G-?-CD resulted in changes in some of the characteristic spectral, phase-transitional, and morphological properties of puerarin. PMID:23215052

Liu, Benguo; Zhao, Jian; Liu, Yanhong; Zhu, Xiaoai; Zeng, Jie

2012-12-26

356

Structural and magnetic properties of chromium doped zinc ferrite  

SciTech Connect

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

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

2014-01-28

357

Symmetry properties of the large-scale solar magnetic field  

E-print Network

We investigate symmetry properties of the solar magnetic field in the framework of the linear Parker's migratory dynamo model. We show that the problem can be mapped onto the well-known quantum-mechanical double-well problem. Using the WKB approximation, we construct analytical solutions for the dipole and quadrupole configurations of the generated magnetic field. Our asymptotic analysis within the equatorial region indicates the existence of an additional weak dynamo wave which violates the Hale's polarity law. We estimate the spatial decay decrement of this wave. We also calculate explicitly the splitting of the eigenvalues corresponding to the dipole and quadrupole modes. The real part of the dipole eigenvalue is shown to exceed the quadrupole one. A sufficiently long time after generation the dipole mode should dominate the quadrupole one. The relevant observational evidences of the properties obtained are discussed.

Victor Galitski; K. M. Kuzanyan; D. D. Sokoloff

2001-08-03

358

Fermi surface, magnetic, and superconducting properties in actinide compounds  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

359

Magnetic properties of vanadium-doped silicon carbide nanowires  

Microsoft Academic Search

This study reports the magnetic properties of vanadium (V) doped single crystalline silicon carbide nanowires. The first principle\\u000a calculation indicated that the V-doped cubic SiC phase can exhibit half-metallic ferromagnetic properties that are essential\\u000a for the realization of spintronic devices. Based on this calculation, V-doped SiC nanowires were fabricated in a chemical\\u000a vapor deposition process. The single crystalline ?-SiC nanowires,

Han-Kyu Seong; Tae-Eon Park; Seung-Cheol Lee; Kwang-Ryeol Lee; Jae-Kwan Park; Heon-Jin Choi

2009-01-01

360

Sputtered Sm-Co films: Microstructure and magnetic properties  

NASA Astrophysics Data System (ADS)

Films of Sm-Co have been sputtered on heated polycrystalline Al2O3 substrates. The effect of variations of the Sm content on microstructure and hard magnetic properties was studied for otherwise constant process parameters. As generally observed, the samples possess a magnetic texture where the easy magnetization directions of the grains lay preferably in the film plane. For a lower Sm content the TbCu7-type structure is stabilized and for a higher Sm content the CaCu5-type structure is stabilized. The crossover occurs for a Sm content of around 17 at. %. Consistent with the changes in the intrinsic properties, coercivity increases and remanence decreases with increasing the Sm content. The grain size increases with increasing the Sm content and is attributed to a higher surface mobility during crystallization and grain growth. This behavior is also assumed to cause the improvement in the in-plane texture with increasing the Sm content, that had been quantified by magnetic and crystallographic investigations.

Neu, V.; Shaheen, S. A.

1999-12-01

361

Structural, dielectric and magnetic properties of Ni substituted zinc ferrite  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

362

The X-ray properties of magnetic massive stars  

NASA Astrophysics Data System (ADS)

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

Nazé, Yaël; Petit, Véronique; Rinbrand, Melanie; Cohen, David; Owocki, Stan; ud-Doula, Asif; Wade, Gregg

2015-01-01

363

Growth and magnetic properties of ultrathin Fe on Pd(110).  

SciTech Connect

We have investigated the growth and magnetic properties of 0-3 ML (monolayer) Fe on stepped Pd(110) with reflection high-energy electron diffraction (RHEED), low-energy electron diffraction (LEED) and the surface magneto-optic Kerr effect (SMOKE) in order to relate the morphology, structure and magnetic properties in a low-dimensional system. The Fe films, grown at 340 K, are smooth and pseudomorphic up to 1.5 ML, where three-dimensional growth and lateral lattice relaxation ensues. The in-plane row spacing along the [110] decreases by {approximately}5-6 % at 3 ML. RHEED oscillations with l-ML period are observed in the (1,0), (2,0) and the center of the (0,0) streak intensity. The tail of the (0,0) streak at low exit angle, however, has a 0.5-ML period oscillation, which suggests step decoration growth. Submonolayer Fe films remain ferromagnetic above {approximately}0.3 ML. The magnetic easy axis is initially perpendicular to the surface and is in-plane for Fe thickness >1.5 ML. Between 0.9-1.2 ML, there appear to be mixed magnetic phases as indicated by an increase in coercivity.

Cuenya, B. R.; Pearson, J.; Yu, C.; Li, D.; Bader, S. D.

2000-11-01

364

Magnetic Structure and Magnetic Properties of CaMn2Sb2  

NASA Astrophysics Data System (ADS)

The AM2X2 ternary intermetallic (A = rare or alkaline earth, M = transition metal) compounds have revealed interesting magnetic properties due to the interplay between their magnetic sublattices. Pursuing the idea that the coupling between Mn-Mn ions can significantly affect electric transport properties, we investigated (Ca,Sr)Mn2Sb2 intermetallic compounds which presents two secondary magnetic transitions at 82K and 250K. Field dependent dc-magnetization curves for CaMn2Sb2 were obtained at two different temperatures, above and below 250K, show a relatively steep increase of the magnetization upon increasing the field to H &_slash; 5 kOe, followed by a less steep and almost linear increase with the field and no tendency for saturation. The net macroscopic moment on the Mn at 300 K and 50 kOe is only a fraction of a Bohr magneton (ca. 0.15 {'í}B/ Mn), and evidently, a simple interpretation of its value in terms of localized high/low spin Mn2+ ions is unrealistic. The low moment can be viewed as a signature of the counterbalanced coupling between Mn atoms that are sitting on two inequivalent magnetic sites as predicted by theory [1]. In order to understand CaMn2Sb2 magnetic structure, we also performed neutron scattering measurements to clarify the magnetic structure and the origin of the low temperature transition. [1] S. Boved, J. Merz, A. L. Lima, V. Fritsch, J. D. Thompson, J. L. Sarrao, M. Gillessen, and R. Dronskowski. {Inorg. Chem.}, 45:4047, 2006.

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

2008-03-01

365

Magnetic properties of 3d impurities in GaAs  

Microsoft Academic Search

Electronic structure, thermodynamic, and magnetic properties of 3d-transition metal (TM) impurities in GaAs have been studied from first principles using Green's function approach. The studied TM impurities (V, Cr, Mn, and Fe) are found to form substitutional alloys on the Ga sublattice. The possibility of raising the Curie temperature TC in (GaMn)As by co-doping it with Cr impurities was examined

V. I. Baykov; P. A. Korzhavyi; E. A. Smirnova; I. A. Abrikosov; B. Johansson

2007-01-01

366

Microstructure and magnetic properties of commercial barium ferrite powders  

Microsoft Academic Search

Purpose: Microstructural and magnetic properties analysis of commercial barium ferrite powder BaFe12O19. Design\\/methodology\\/approach: The X-ray diffraction methods were utilized not only for qualitative and quantitative phase analysis of studied powder sample, but also for the determination of lattice parameters, crystallite size and the lattice distortion. The Rietveld method was used in the verification of the qualitative phase composition and in

R. Nowosielski; R. Babilas; J. Wrona

367

Magnetic Properties of Potassium Iron Group Fluorides KMF3  

Microsoft Academic Search

Evidence of antiferromagnetism in perovskite-type potassium iron group fluoride KMF3 was found through the susceptibility measurements made between 80°K and 700°K. The obtained results are as follows: \\\\includegraphics{dummy.eps} Additional thermal analysis was also made in order to confirm the Néel points. The magnetic properties of these compounds are reviewed and brief discussions of our results are given.

Kinshiro Hirakawa; Kazuyoshi Hirakawa; Takasu Hashimoto

1960-01-01

368

Magnetoresistance and magnetic properties of epitaxial magnetite thin films  

Microsoft Academic Search

The magnetotransport and magnetic properties of epitaxial Fe3O4 thin films grown on (001)-oriented MgO substrates by pulsed-laser deposition have been investigated. The magnetoresistance (MR) exhibits a peak around the Verwey transition (Tnu) as has also been reported previously for single crystals. Additionally, we have observed that the MR increases monotonically below 100 K with decreasing temperature. MR values as high

G. Q. Gong; A. Gupta; Gang Xiao; W. Qian; V. P. Dravid

1997-01-01

369

Magnetic and transport properties of magnetite thin films  

Microsoft Academic Search

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

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

2005-01-01

370

Magnetic and Structural Properties of Fully Epitaxial for Spin Injection  

Microsoft Academic Search

In this paper, the authors report on the investigation on the effect of inserting an epitaxial MgO layer on the structural and magnetic properties of Fe3O4 ultrathin films grown on GaAs(100) by combined techniques of molecular beam epitaxy and postgrowth annealing in an oxygen atmosphere. The MgO films were grown with a cube-on-cube orientation to GaAs. The epitaxial Fe3O4 lattice

P. K. J. Wong; Wen Zhang; Yongbing Xu; Sameh Hassan; S. M. Thompson

2008-01-01

371

Magnetic properties of geometrically frustrated SrGd2O4  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

372

Cryogenic properties of dispersion strengthened copper for high magnetic fields  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

373

Cryogenic properties of dispersion strengthened copper for high magnetic fields  

SciTech Connect

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

Toplosky, V. J.; Han, K.; Walsh, R. P. [National High Magnetic Field Laboratory, Tallahassee, FL 32310 (United States); Swenson, C. A. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

2014-01-27

374

Magnetic properties of the ferrimagnetic glass-ceramics for hyperthermia  

NASA Astrophysics Data System (ADS)

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

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

2006-10-01

375

Synthesis and magnetic properties of single phase titanomagnetites  

SciTech Connect

The focus of this paper is the study of cation distributions and resulting magnetizations in titanomagnetites (TMs), (1?x)Fe{sub 3}O{sub 4?x}Fe{sub 2}TiO{sub 4} solid solutions. TM remnant states are hypothesized to contribute to planetary magnetic field anomalies. This work correlates experimental data with proposed models for the TM pseudobinary. Improved synthesis procedures are reported for single phase Ulvöspinel (Fe{sub 2}TiO{sub 4}), and TM solid solutions were made using solid state synthesis techniques. X-ray diffraction and scanning electron microscopy show samples to be single phase solid solutions. M-H curves of TM75, 80, 85, 90, and 95 (TMX where X?=?at.?% of ulvöspinel) were measured using a Physical Property Measurement System at 10?K, in fields of 0 to 8?T. The saturation magnetization was found to be close to that predicted by the Neel model for cation distribution in TMs. M-T curves of the remnant magnetization were measured from 10?K to 350?K. The remnant magnetization was acquired at 10?K by applying an 8?T field and then releasing the field. Experimental Neel temperatures are reported for samples in the Neel model ground state.

Schoenthal, W., E-mail: wms@andrew.cmu.edu; Liu, X.; Cox, T.; Laughlin, D. E.; McHenry, M. E. [Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Mesa, J. L.; Diaz-Michelena, M. [Instituto Nacional de Tecnica Aeroespacial, Madrid (Spain); Maicas, M. [Universidad Politecnica de Madrid, ISOM-ETSIT, Madrid (Spain)

2014-05-07

376

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

USGS Publications Warehouse

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

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

2011-01-01

377

Synthesis, photoluminescence and magnetic properties of barium vanadate nanoflowers  

SciTech Connect

Graphical abstract: The flower-shaped barium vanadate was obtained for the first time. The photoluminescence and magnetic properties of the barium vanadate nanoflowers were investigated at room temperature. Research highlights: {yields} In the paper, the flower-shaped barium vanadate were obtained for the first time. The CHM method used here is new and simple for preparation of barium vanadate. {yields} The photoluminescence and magnetic properties of the barium vanadate nanoflowers were investigated at room temperature. The strong bluish-green emission was observed. {yields} The ferromagnetic behavior of the barium vanadate nanoflowers was found with saturation magnetization of about 83.50 x 10{sup -3} emu/g, coercivity of 18.89 Oe and remnant magnetization of 4.63 x 10{sup -3} emu/g. {yields} The mechanisms of PL and magnetic property of barium vanadate nanoflowers have been discussed. -- Abstract: The flower-shaped barium vanadate has been obtained by the composite hydroxide mediated (CHM) method from V{sub 2}O{sub 5} and BaCl{sub 2} at 200 {sup o}C for 13 h. XRD and XPS spectrum of the as-synthesized sample indicate it is hexagonal Ba{sub 3}V{sub 2}O{sub 8} with small amount of Ba{sub 3}VO{sub 4.8} coexistence. Scan electron microscope and transmission electron microscope display that the flower-shaped crystals are composed of nanosheets with thickness of {approx}20 nm. The UV-visible spectrum shows that the barium vanadate sample has two optical gaps (3.85 eV and 3.12 eV). Photoluminescence spectrum of the barium vanadate flowers exhibits a visible light emission centered at 492 and 525 nm which might be attributed to VO{sub 4} tetrahedron with T{sub d} symmetry in Ba{sub 3}V{sub 2}O{sub 8}. The ferromagnetic behavior of the barium vanadate nanoflowers has been found with saturation magnetization of about 83.50 x 10{sup -3} emu/g, coercivity of 18.89 Oe and remnant magnetization of 4.63 x 10{sup -3} emu/g, which is mainly due to the presence of a non-orthovanadate phase with spin S = 1/2.

Xu, Jing [Department of Applied Physics, Chongqing University, 174 Shapingba Street, Chongqing 400044 (China) [Department of Applied Physics, Chongqing University, 174 Shapingba Street, Chongqing 400044 (China); Chongqing University of Science and Technology, Chongqing 401331 (China); Hu, Chenguo, E-mail: hucg@cqu.edu.cn [Department of Applied Physics, Chongqing University, 174 Shapingba Street, Chongqing 400044 (China)] [Department of Applied Physics, Chongqing University, 174 Shapingba Street, Chongqing 400044 (China); Xi, Yi [Department of Applied Physics, Chongqing University, 174 Shapingba Street, Chongqing 400044 (China)] [Department of Applied Physics, Chongqing University, 174 Shapingba Street, Chongqing 400044 (China); Peng, Chen [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China)] [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Wan, Buyong; He, Xiaoshan [Department of Applied Physics, Chongqing University, 174 Shapingba Street, Chongqing 400044 (China)] [Department of Applied Physics, Chongqing University, 174 Shapingba Street, Chongqing 400044 (China)

2011-06-15

378

Magnetic properties changes due to hydrocarbon contaminated groundwater table fluctuations  

NASA Astrophysics Data System (ADS)

This study aims to understand the mechanisms and conditions which control the formation and transformation of ferro(i)magnetic minerals caused by hydrocarbon contaminated groundwater, in particular in the zone of fluctuating water levels. The work extends previous studies conducted at the same site. The study area is a former military air base at Hrad?any, Czech Republic (50°37'22.71"N, 14°45'2.24"E). The site was heavily contaminated with petroleum hydrocarbons, due to leaks in petroleum storage tanks and jet fuelling stations over years of active use by the Soviet Union, which closed the base in 1991. The site is one of the most important sources of high quality groundwater in the Czech Republic. In a previous study, Rijal et al. (2010) concluded that the contaminants could be flushed into the sediments as the water level rose due to remediation processes leading to new formation of magnetite. In this previous study three different locations were investigated; however, from each location only one core was obtained. In order to recognize significant magnetic signatures versus depth three cores from each of these three locations were drilled in early 2012, penetrating the unsaturated zone, the groundwater fluctuation (GWF) zone and extending to about one meter below the groundwater level (~2.3 m depth at the time of sampling). Magnetic susceptibility (MS) profiles combined with other magnetic properties were analyzed to obtain a significant depth distribution of the ferro(i)magnetic concentration. Sediment properties, hydrocarbon content and bacterial activity were additionally studied. The results show that the highest ferrimagnetic mineral concentrations exist between 1.4-1.9 m depth from the baseline which is interpreted as the top of the GWF zone. Spikes of MS detected in the previous studies turned out to represent small-scale isolated features, but the trend of increasing MS values from the lowermost position of the groundwater table upward was verified. Mineral magnetic parameters indicate that magnetite is responsible for the MS signal which confirms the previous results (Rijal et al., 2010). The so far existing uncertainty of the groundwater level position could be solved. Bacterial activity is studied at particular depth horizons as it is assumed to be responsible for iron mineralogy changes. References: Rijal M.L., Appel E., Petrovský E. and Blaha U., 2010. Change of magnetic properties due to fluctuations of hydrocarbon contaminated groundwater in unconsolidated sediments. Environ.Pollut., 158, 1756-1762.

Ameen, Nawrass

2013-04-01

379

Structural and magnetic properties of nanostructured Mn Al C magnetic materials  

NASA Astrophysics Data System (ADS)

Pre-alloyed Mn 50+x-yAl 50-xC y ( x=0, 2, 4, 6, 8; y=0, 1.7, 3) powders were mechanically milled (MM), and the as-milled powders subsequently annealed at temperatures from 350 to 600 °C to produce the ferromagnetic metastable L1 0-structured ?-phase. Bulk Mn 54Al 46 specimens were also annealed under the same conditions for comparison. The effects of the Mn concentration and C additions on phase formation, microstructure, magnetic properties, as well as on the magnetization mechanism of the Mn-Al-C alloys were systematically investigated. It was found that the magnetic properties are strongly dependent both on the fraction of the ?-phase and its microstructure. There exists a strong influence of the microstructural refinement, due to the ball milling, on the rate of ?-phase to ?-phase transformation and on the stability of the ?-phase. The kinetics of formation and subsequent decomposition of the magnetic ?-phase were markedly different in the MM and bulk alloys. Both remanence curves and ?M plots showed no exchange coupling among the ?-phase nanograins. The mechanism for the magnetization process was determined to be domain wall pinning.

Zeng, Q.; Baker, I.; Cui, J. B.; Yan, Z. C.

2007-01-01

380

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

381

Dynamical magnetic and nuclear polarization in complex spin systems: semi-magnetic II-VI quantum dots  

NASA Astrophysics Data System (ADS)

Dynamical magnetic and nuclear polarization in complex spin systems is discussed on the example of transfer of spin from exciton to the central spin of magnetic impurity in a quantum dot in the presence of a finite number of nuclear spins. The exciton is described in terms of electron and heavy-hole spins interacting via exchange interaction with magnetic impurity, via hyperfine interaction with a finite number of nuclear spins and via dipole interaction with photons. The time evolution of the exciton, magnetic impurity and nuclear spins is calculated exactly between quantum jumps corresponding to exciton radiative recombination. The collapse of the wavefunction and the refilling of the quantum dot with a new spin-polarized exciton is shown to lead to the build up of magnetization of the magnetic impurity as well as nuclear spin polarization. The competition between electron spin transfer to magnetic impurity and to nuclear spins simultaneous with the creation of dark excitons is elucidated. The technique presented here opens up the possibility of studying optically induced dynamical magnetic and nuclear polarization in complex spin systems.

Abolfath, Ramin M.; Trojnar, Anna; Roostaei, Bahman; Brabec, Thomas; Hawrylak, Pawel

2013-06-01

382

Full 3D MHD calculations of accretion flow structure in magnetic cataclysmic variables with strong, complex magnetic fields  

NASA Astrophysics Data System (ADS)

We have performed three-dimensional magnetohydrodynamical calculations of stream accretion in cataclysmic variable stars for which the white dwarf primary possesses a strong, complex magnetic field. These calculations were motivated by observations of polars: cataclysmic variables containing white dwarfs with magnetic fields sufficiently strong to prevent the formation of an accretion disk. In this case, an accretion stream flows from the L1 point and impacts directly onto one or more spots on the surface of the white dwarf. Observations indicate that the white dwarfs in some binaries possess complex (non-dipolar) magnetic fields. We performed simulations of ten polars, with the only variable being the azimuthal angle of the secondary with respect to the white dwarf. These calculations are also applicable to asynchronous polars, where the spin period of the white dwarf differs by a few percent from the orbital period. Our results are equivalent to calculating the structure of one asynchronous polar at ten different spin-orbit beat phases. Our models have an aligned dipolar plus quadrupolar magnetic field centered on the whitedwarf primary. We find that, with a sufficiently strong quadrupolar component, an accretion spot arises near the magnetic equator for slightly less than half our simulations, while a polar accretion zone is active for most of the remaining simulations. For two configurations, accretion at a dominant polar region and in an equatorial zone occurs simultaneously. Most polar studies assume that the magnetic field is dipolar, especially for single-pole accretors. We demonstrate that, with the orbital parameters and magnetic-field strengths typical of polars, the accretion flow patterns can vary widely in the case of a complex magnetic field. This may make it difficult formany polars to determine observationally whether the field is pure dipolar or is more complex, but there shoulid be indications for some systems. In particular, a complex magnetic field should be suspected if there is an accretion zone near the white dwarf's equator (assumed to be in the orbital plane) or if there are two or more accretion regions that cannot be fitted by dipolar magnetic field. Magnetic-field constraints are expected to be substantially stronger for asynchronous polars, with clearer signs of complex field geometry due to changes in the accretion flow structure as a function of azimuthal angle. These indications become clearer in asynchronous polars because each azimuthal angle corresponds to a different spin-orbit beat phase.

Zhilkin, A. G.; Bisikalo, D. V.; Mason, P. A.

2012-04-01

383

Magnetic and magnetodielectric properties of erbium iron garnet ceramic  

SciTech Connect

An Er{sub 3}Fe{sub 5}O{sub 12} ceramic has been sintered in oxygen atmosphere at 1400 Degree-Sign C for dielectric measurements. Its structural quality at room temperature has been checked by combining transmission electron microscopy and X-ray diffraction. It crystallizes in the cubic space group Ia3d with a = 12.3488(1). The dielectric permittivity ({epsilon} Prime ) and losses (tan {delta}) measurements as a function of temperature reveal the existence of two anomalies, a broad one between 110 K and 80 K, attributed to the Er{sup 3+} spin reorientation, and a second sharper feature at about 45 K associated to the appearance of irreversibility on the magnetic susceptibility curves. In contrast to the lack of magnetic field impact on {epsilon} Prime for the former anomaly, a complex magnetic field effect has been evidenced below 45 K. The isothermal {epsilon} Prime (H) curves show the existence of positive magnetodielectric effect, reaching a maximum of 0.14% at 3 T and 10 K. Its magnitude decreases as H is further increased. Interestingly, for the lowest H values, a linear regime in the {epsilon} Prime (H) curve is observed. From this experimental study, it is concluded that the {epsilon} Prime anomaly, starting above the compensation temperature T{sub c} (75 K) and driven by the internal magnetic field, is not sensitive to an applied external magnetic field. Thus, below 45 K, it is the magnetic structure which is responsible for the coupling between spin and charge in this iron garnet.

Maignan, A.; Singh, K.; Simon, Ch.; Lebedev, O. I.; Martin, C. [Laboratoire CRISMAT, UMR 6508 CNRS/ENSICAEN, 6 bd du Marechal Juin, F-14050 Caen Cedex 4 (France); Tan, H.; Verbeeck, J.; Van Tendeloo, G. [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium)

2013-01-21

384

Magnetic Properties of Ba-Zn-System W-Type Hexagonal Ferrite Magnets  

Microsoft Academic Search

Ba-Zn system W-type hexagonal ferrite magnets were prepared by a new manufacturing method in which BaO was added after semisintering treatment, and without atmosphere control. This process was found to be very useful in stabilizing the W-type hexagonal structure. The optimum conditions for making magnets, and some properties of typical specimens, are as follows: chemical analysis Ba1.092Zn1.725-Fe2+ 0.410Fe3+15.848O27; semisintering conditions

H. Yamamoto; A. Ishii

1993-01-01

385

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

E-print Network

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

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

2014-10-10

386

Spin-polarized transport through single-molecule magnet Mn6 complexes  

NASA Astrophysics Data System (ADS)

The coherent transport properties of a device, constructed by sandwiching a Mn6 single-molecule magnet between two gold surfaces, are studied theoretically by using the non-equilibrium Green's function approach combined with density functional theory. Two spin states of such Mn6 complexes are explored, namely the ferromagnetically coupled configuration of the six MnIII cations, leading to the S = 12 ground state, and the low S = 4 spin state. For voltages up to 1 volt the S = 12 ground state shows a current one order of magnitude larger than that of the S = 4 state. Furthermore this is almost completely spin-polarized, since the Mn6 frontier molecular orbitals for S = 12 belong to the same spin manifold. As such the high-anisotropy Mn6 molecule appears as a promising candidate for implementing, at the single molecular level, both spin-switches and low-temperature spin-valves.The coherent transport properties of a device, constructed by sandwiching a Mn6 single-molecule magnet between two gold surfaces, are studied theoretically by using the non-equilibrium Green's function approach combined with density functional theory. Two spin states of such Mn6 complexes are explored, namely the ferromagnetically coupled configuration of the six MnIII cations, leading to the S = 12 ground state, and the low S = 4 spin state. For voltages up to 1 volt the S = 12 ground state shows a current one order of magnitude larger than that of the S = 4 state. Furthermore this is almost completely spin-polarized, since the Mn6 frontier molecular orbitals for S = 12 belong to the same spin manifold. As such the high-anisotropy Mn6 molecule appears as a promising candidate for implementing, at the single molecular level, both spin-switches and low-temperature spin-valves. Electronic supplementary information (ESI) available: Calculated total and projected density of states of an isolated [Mn6O2(Et-sao)6{O2CPh(Me)2}2(EtOH)6] original SMM complex (Fig. S1). Calculated total and projected density of states of an isolated [Mn6O2(Me-sao)6{O2CPh(SH)}2(MeOH)6] model complex (Fig. S2). Transmission spectra calculated at different voltages corresponding to the S = 12 and S = 4 ground states for the Mn6-Au(111) layer system (Fig. S3). Cell parameters and Cartesian coordinates of the Mn6-Au(111) layer system. See DOI: 10.1039/c3nr00054k

Cremades, Eduard; Pemmaraju, C. D.; Sanvito, Stefano; Ruiz, Eliseo

2013-05-01

387

Electron carrier concentration dependent magnetization and transport properties in ZnO:Co diluted magnetic semiconductor thin films  

E-print Network

for ferromagnetic exchange in ZnO:Co diluted magnetic semiconductor materials. © 2008 American Institute of PhysicsElectron carrier concentration dependent magnetization and transport properties in ZnO:Co diluted October 2008; published online 4 December 2008 Diluted magnetic semiconducting ZnO:Co thin films

Yang, Zheng

388

The effects of explosive-driven shocks on the natural remanent magnetization and the magnetic properties of rocks  

Microsoft Academic Search

The effects of shock waves on the natural remanent magnetization and the intrinsic magnetic properties of geological materials remain poorly known. Still, hypervelocity impact phenomena are of primary importance in the evolution of many extraterrestrial bodies and of Earth. We present new experiments in which four rocks with different lithology and magnetic mineralogy (titanomagnetite, magnetite, monoclinic pyrrhotite, titanohematite) were shocked

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

2007-01-01

389

Some properties of the circular waveguide with azimuthally magnetized ferrite  

NASA Astrophysics Data System (ADS)

A comprehensive analysis of normal rotationally symmetric TE modes in a circular waveguide, filled with ferrite, magnetized azimuthally to remanence by a coaxial switching conductor of finite radius, is presented. The characteristic equation of the structure, derived in terms of Kummer and Tricomi confluent hypergeometric functions of complex parameter and variable, is solved numerically, using specially compiled tables of wave functions. Families of theoretically calculated nonreciprocal phase characteristics of the gyrotropic waveguide are shown in normalized form for the two latched states of remanent magnetization, a variety of ferrite parameters, and different values of switching conductor to waveguide radius ratio. The influence of structure geometry and parameters of anisotropic ferrite on normalized differential phase shift and cutoff frequency spectrum of the TE01 mode is discussed.

Ivanov, Kamen P.; Georgiev, Georgi N.

1990-05-01

390

In vitro cartilage formation using TGF-beta-immobilized magnetic beads and mesenchymal stem cell-magnetic bead complexes under magnetic field conditions.  

PubMed

We evaluated the efficacy of transforming growth factor (TGF)-beta-immobilized magnetic beads for chondrogenesis in vitro using a mesenchymal stem cell (MSC) delivery system and an external magnetic force (EMF). MSCs isolated from the bone marrow of Sprague Dawley rats were mixed with carboxyl group-combined magnetic beads (Ferri Sphere 100C) coated with anti-rat CD44 mouse monoclonal antibodies. TGF-beta3 (10 and 1 ng/mL) was attached magnetically to such other Ferri Sphere 100C beads via an amide bond formed between a primary amino group on the TGF-beta3 and the carboxyl groups on the surface of the beads. MSC-magnetic bead complexes were centrifuged to form a pellet and cultured in chondrogenic differentiation medium (CDM) supplemented with either 10 or 1 ng/mL TGF-beta-immobilized magnetic beads (10 or 1 ng/mL TGF-beta-immobilized magnetic bead groups) or in CDM supplemented with 1 or 10 ng/mL TGF-beta (1 or 10 ng/mL TGF-beta group). TGF-beta-immobilized magnetic beads were gathered effectively under an EMF. Chondrogenesis was achieved from the MSC-magnetic bead complexes in the presence of 1 ng/mL TGF-beta-immobilized magnetic beads. PMID:19172619

Motoyama, Mitsuru; Deie, Masataka; Kanaya, Atsushi; Nishimori, Makoto; Miyamoto, Ayato; Yanada, Shinobu; Adachi, Nobuo; Ochi, Mitsuo

2010-01-01

391

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

PubMed

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

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

2013-11-21

392

Full-field velocity and temperature measurements using magnetic resonance imaging in turbulent complex internal flows  

Microsoft Academic Search

Flow and heat transfer in complex internal passages are difficult to predict due to the presence of strong secondary flows and multiple regions of separation. Two methods based on magnetic resonance imaging called 4D magnetic resonance velocimetry (4D-MRV) and thermometry (4D-MRT) are described for measuring the full-field mean velocities and temperatures, respectively, in complex internal passage flows. 4D-MRV measurements are

C. J. Elkins; M. Markl; A. Iyengar; R. Wicker; J. K. Eaton

2004-01-01

393

Jovian magnetic fields is complex, Pioneer 11 shows  

NASA Technical Reports Server (NTRS)

An analysis of the magnetic field of the planet Jupiter is presented. The data are based on the information returned by Pioneer 11 space probe. It was determined that the magnetic field stretches across 9 million miles of space at some times and shrinks in volume by three-fourths or more at other times. It was also determined that electrons trapped in the magnetic field of Jupiter are 10,000 times more intense than those in the Van Allen radiation belts which circle the earth. Additional data were obtained on the polar regions, atmospheric circulation, and the nature of the moons.

Panagakos, N.; Waller, P.

1975-01-01

394

ON THE INFLUENCE OF 3d4 IONS ON THE MAGNETIC AND CRYSTALLOGRAPHIC PROPERTIES OF MAGNETIC OXIDES (1)  

E-print Network

155 ON THE INFLUENCE OF 3d4 IONS ON THE MAGNETIC AND CRYSTALLOGRAPHIC PROPERTIES OF MAGNETIC OXIDES properties of several Mn3+-containing, perovskite-type oxides can be interpreted as due to this peculiar ferrimagnétisme dans les réseaux perovskites contenant des cations Mn3+, Abstract. 2014 After a brief reference

Boyer, Edmond

395

Growth process and magnetic properties of ?-FeSe nanostructures  

SciTech Connect

Growth process and magnetic properties of PbO-type ?-Fe{sub x}Se nanostructures with shape changing from nanocacti to nanopetals and then to nanosheets are investigated. With iron acetylacetonate [Fe(acac){sub 3}] and Se powder as raw materials, the diffusion process of Fe atoms dominates the synthesis of ?-Fe{sub x}Se nanocacti following phase transitions from FeSe{sub 2} to Fe{sub 3}Se{sub 4} and finally to ?-Fe{sub x}Se. When a mixed solution containing Se precursor and Fe(acac){sub 3} was used as the raw material, the formation of FeSe{sub 2} and Fe{sub 3}Se{sub 4} can be avoided and, bended ?-Fe{sub x}Se nanopetals can be prepared at 345?°C, which became flat nanosheets with a [001] preferred orientation as extending the reaction time from 1 to 4 h. No superconducting transition occurs in the ?-Fe{sub x}Se (0.84???x???1.05) nanostructures due to composition heterogeneity or size effect. Magnetic measurements indicate that an antiferromagnetic component with a Néel point at about 45 K dominates the magnetic properties of the ?-Fe{sub 0.87}Se nanosheets.

Li, S. J.; Li, D., E-mail: dali@imr.ac.cn; Jiang, J. J.; Liu, G. B.; Ma, S.; Liu, W.; Zhang, Z. D. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, and International Centre for Materials Physics, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China)

2014-05-07

396

Nano-structured magnetic metamaterial with enhanced nonlinear properties  

PubMed Central

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

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

2012-01-01

397

Magnetic properties of graphite irradiated with MeV ions  

SciTech Connect

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

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

2010-06-01

398

Magnetic and magnetocaloric properties of bulk dysprosium chromite  

SciTech Connect

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

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

2013-09-21

399

Structural And Magnetic Properties Of Ni-Zn Ferrite Nanoparticles  

NASA Astrophysics Data System (ADS)

Nickel zinc ferrite nanoparticles of the composition NixZn1-xFe2O4 (x = 0.1, 0.3, 0.5) have been synthesized by the chemical co-precipitation method. The samples were characterized by X-ray diffraction, TEM, EPR, DC magnetization and AC susceptibility measurements. The X-ray diffraction patterns confirm the synthesis of single crystalline phase of NixZn1-xFe2O4 (x = 0.1, 0.3, 0.5) nanoparticles. Lattice parameter decreases with the increase in nickel content. The magnetic measurements shows superparamagnetic nature of the samples for x = 0.1 and 0.3 whereas for x = 0.5 the material shows ferromagnetic nature. The saturation magnetization is low and increases with increase in nickel content. The superparamagnetic nature of the samples is supported by the EPR and ac susceptibility measurement studies. The blocking temperature increases with the nickel concentration. The changes in the magnetic properties have been explained by the redistribution of the cations on A and B sites.

Shahane, G. S.; Kumar, Ashok; Pant, R. P.; Lal, Krishan

2010-10-01

400

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

SciTech Connect

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

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

2012-01-15

401

Tailoring the magnetic properties of Fe asymmetric nanodots  

NASA Astrophysics Data System (ADS)

Asymmetric dots as a function of their geometry have been investigated using three-dimensional (3D) object oriented micromagnetic framework (OOMMF) code. The effect of shape asymmetry of the disk on coercivity and remanence is studied. Angular dependence of the remanence and coercivity is also addressed. Asymmetric dots are found to reverse their magnetization by nucleation and propagation of a vortex, when the field is applied parallel to the direction of asymmetry. However, complex reversal modes appear when the angle at which the external field is applied is varied, leading to a non-monotonic behavior of the coercivity and remanence.

Leighton, B.; Vargas, N. M.; Altbir, D.; Escrig, J.

2011-06-01

402

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Magnetic properties and magnetocaloric effect in Ndx La1-x Fe11.5 Al1.5 compounds  

NASA Astrophysics Data System (ADS)

Effects of Nd-doping on the magnetic properties and magnetocaloric effects (MCEs) of NdxLa1-x Fe11.5 Al1.5 have been investigated. Substitution of Nd leads to a weakening of the antiferromagnetic (AFM) coupling and an enhancement of the ferromagnetic (FM) coupling. This in turn results in a complex magnetic behaviour for Nd0.2La0.8Fe11.5Al1.5 characterized by the occurrence of two phase transitions at ~188K (PM-AFM) and ~159K (AFM-FM). As a result, a table-like MCE (9 J/kg·K) is found in a wide temperature range (160-185 K) for a field change of 0-5T around the transition temperature, as evidenced by both the magnetic and calorimetric measurements. Based on the analysis of low-temperature heat capacity, it is found that the AFM-FM phase transition modifies the electron density significantly, and the major contribution to the entropy change comes from the electronic entropy change.

Wang, Fang; Wang, Guang-Jun; Sun, Ji-Rong; Shen, Bao-Gen

2008-08-01

403

Effect of warm compaction on the magnetic and electrical properties of Fe-based soft magnetic composites  

Microsoft Academic Search

This paper investigates the effect of warm compaction on the magnetic and electrical properties of Fe-based soft magnetic composites at operating frequencies between 0.1 and 10kHz. The magnetic and electrical properties of samples were measured by an LCR meter and morphology of the samples was characterized by scanning electron microscopy. It was shown that the compacted sample prepared at 800MPa

H. Shokrollahi; K. Janghorban

2007-01-01

404

Soft magnetic composites of iron-phenolic and the influence of silane coupling agent on the magnetic properties  

Microsoft Academic Search

This paper investigates the effect of silane coupling agent on the magnetic properties of iron-phenolic soft magnetic composite materials at operating frequencies between 50Hz and 1000kHz. Coupling agents, cause a better wetting and a uniform coating distribution between the iron powders and the phenolic coating. The magnetic properties of the samples were measured by an LCR meter. The phase identification

A. H. Taghvaei; H. Shokrollahi; A. Ebrahimi; K. Janghorban

2009-01-01

405

Electronic, optical and magnetic properties of self-assembled quantum dots containing magnetic ions  

NASA Astrophysics Data System (ADS)

There is currently interest in developing control over the spin of a single Manganese (Mn) ion, the atomic limit of magnetic memory, in semiconductor quantum dots (QDs). In this work we present theoretical results showing how one can manipulate the spin of Mn ion with light in a QD by engineering Mn-multi-exciton interactions through quantum interference, design of exciton and bi-exciton states and application of the magnetic field. We develop a fully microscopic model of correlated exciton and bi-exciton interacting with the Mn ion. The electrons and heavy holes, confined in the QD, approximated as a two-dimensional harmonic oscillator (HO), interact via direct and short- and long-range exchange Coulomb interactions. The matrix elements of the exchange interaction are computed for the first time in the harmonic oscillator basis and for arbitrary magnetic fields. The exciton and bi-exciton energies and states are computed using the configuration interaction method. The interaction between carriers and the Mn spin is accounted for by the Heisenberg electron-Mn and Ising hole-Mn exchange interactions. For a single exciton confined in a magnetic dot, a novel quantum interference (QI) effect between the electron-hole Coulomb scattering and the scattering by Mn ion is obtained. The QI significantly affects the exciton-Mn coupling, modifying the splitting of the emission/absorption lines from the exciton-Mn complex depending on the degree of electronic correlations in the exciton state. The second signature of the QI are the nonuniform energy gaps between the consecutive emission peaks due to the scattering of carriers by Mn among single-particle orbitals. Magneto-photoluminescence experiments show that the coupling between the exciton and Mn ion does not change in the magnetic field. We report that electron-hole correlations counteract the magnetic squeezing of the single-particle wave functions strengthening the carrier-Mn interactions. As a result, the rate of change of the magneto-photoluminescence spectra with magnetic field is reduced as observed in the experiment. We develop here for the first time a microscopic theory of bi-exciton-Mn complex, and report the presence of the fine structure of bi-exciton-Mn complex, even though as a spin-singlet it is expected to decouple from the localized spin. Theoretical results are compared with experiments in Grenoble and Warsaw.

Trojnar, Anna

406

Magnetotransport properties in magnetic nanotubes studied using Monte Carlo simulations  

NASA Astrophysics Data System (ADS)

The dependences of the magnetoelectric transport properties of nanotubes on the temperature, diameter and anisotropy were simulated using the Monte Carlo method, the Heisenberg model and the Drude formula. The simulations included the effects of an external magnetic field, magnetocrystalline anisotropy and nearest neighbor interactions. Two types of nanotubes with different unit cells (square and hexagonal) were implemented. The influence of the nanotube geometry was also analyzed. A smaller dependence of the resistivity on the nanotube diameter and magnetocrystalline anisotropy was observed for the square unit cell nanotubes compared to the results obtained for the hexagonal unit cell nanotubes. Furthermore, lower fluctuations in the resistivity were observed in the former. In contrast, an external magnetic field had a greater influence on the resistivity of the square unit cell nanotubes than for the hexagonal unit cell nanotubes.

Salazar-Enriquez, C. D.; Restrepo-Parra, E.; Restrepo, J.

2013-08-01

407

The magnetic and hyperfine properties of iron in silicon carbide  

NASA Astrophysics Data System (ADS)

The magnetic and hyperfine properties of iron impurities in 3C- and 6H- silicon-carbide are calculated using the abinitio method of full-potential linear-augmented-plane-waves. The iron atoms are introduced at substitutional carbon, Fe C , and silicon, Fe Si , sites as well as at the tetrahedral interstitial sites with four nearest neighbours carbon atoms, Fe I (C), and four nearest neighbours silicon atoms, Fe I (Si). The effect of introducing vacancies at the neighbours of these sites is also studied. Fe atoms with complete neighbors substituted at Si or C sites are found to be nonmagnetic, while Fe atoms at interstitial sites are magnetic. Introduction of a vacancy at a neighboring site reverse the picture.

Elzain, M.; Al-Harthi, S. H.; Gismelseed, A.; Al-Rawas, A.; Yousif, A.; Widatallah, H.; Al-Barwani, M.

2014-04-01

408

Structure and magnetic properties of epitaxial spinel ferrite thin films  

NASA Astrophysics Data System (ADS)

We have grown epitaxial spinel ferrite thin films of (Mn,Zn) Fe2O4 and CoFe2O4 on (100) and (110) SrTiO3 and MgAl2O4 buffered by spinel structure buffer layers. High quality spinel ferrite films were grown at 400 °C on buffer layers that were grown at 600 °C and postannealed at 1000 °C. Although (Mn,Zn) Fe2O4 grown directly on SrTiO3 and MgAl2O4 shows mediocre structural and magnetic properties, ferrite films grown on (100) and (110) SrTiO3 and MgAl2O4 buffered with CoCr2O4 exhibit excellent crystallinity and bulk saturation magnetization values, thus indicating the importance of lattice match and structural similarity between the film and the immediately underlying layer.

Suzuki, Y.; van Dover, R. B.; Gyorgy, E. M.; Phillips, Julia M.; Korenivski, V.; Werder, D. J.; Chen, C. H.; Cava, R. J.; Krajewski, J. J.; Peck, W. F., Jr.; Do, K. B.

1996-01-01

409

Magnetic properties of the Hubbard model on the fcc lattice  

NASA Astrophysics Data System (ADS)

As a possible model for ferromagnetism, we study the magnetic properties of the Hubbard model on an fcc lattice. Near-neighbor and next-near-neighbor hopping parameters are included to examine the effect of band structure. We use exact diagonalization and the Constraint Path Monte Carlo (CPMC) ootnotetextS. Zhang, J. Carlson, and J. Gubernatis, Phys. Rev. B 55, 7464 (1997); C.-C. Chang and S. Zhang, Phys. Rev. B 78, 165101 (2008). methods. Several methodological improvements in CPMC, for example the release of the constraint, will be discussed. We present benchmark quality results on the paramagnetic ground state and partially polarized states, as a function of interaction strength. A magnetic phase diagram is obtained from our many-body calculations, and comparison will be made with results from Dynamical Mean Field theory ootnotetext M. Ulmke, The Eur. Phys. J. B. 1, 301 (1998) .

Shi, Hao; Zhang, Shiwei

2012-02-01

410

Electrical and magnetic properties of ion-exchangeable layered ruthenates  

SciTech Connect

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

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

2004-12-01

411

Magnetic Resonance Based Electrical Properties Tomography: A Review  

PubMed Central

Frequency-dependent electrical properties (EPs; conductivity and permittivity) of biological tissues provide important diagnostic information (e.g. tumor characterization), and also play an important role in quantifying radiofrequency (RF) coil induced Specific Absorption Rate (SAR) which is a major safety concern in high- and ultrahigh-field Magnetic Resonance Imaging (MRI) applications. Cross-sectional imaging of EPs has been pursued for decades. Recently introduced Electrical Properties Tomography (EPT) approaches utilize the measurable RF magnetic field induced by the RF coil in an MRI system to quantitatively reconstruct the EP distribution in vivo and non-invasively with a spatial resolution of a few millimeters or less. This paper reviews the Electrical Properties Tomography approach from its basic theory in electromagnetism to the state of the art research outcomes. Emphasizing on the imaging reconstruction methods rather than experimentation techniques, we review the developed imaging algorithms, validation results in physical phantoms and biological tissues, as well as their applications in in vivo tumor detection and subject-specific SAR prediction. Challenges for future research are also discussed. PMID:24803104

Zhang, Xiaotong; Liu, Jiaen

2014-01-01

412

Structure and magnetic properties of Nb-doped FeZrB soft magnetic alloys  

Microsoft Academic Search

Structure and magnetic properties of Nb-doped (FeZrB)100?xNbx alloy are investigated by X-ray diffraction (XRD), differential scanning calorimetry and vibrating sample magnetometer. The fully amorphous structure of the as-quenched ribbons is confirmed by the XRD pattern. With increasing Nb, the glass transition temperature and the onset crystallization temperature are increased, indicating increased stability of the amorphous structure. For x=1, the saturation

L. H. Kong; Y. L. Gao; T. T. Song; Q. J. Zhai

2011-01-01

413

Structure and magnetic properties of Nb-doped FeZrB soft magnetic alloys  

Microsoft Academic Search

Structure and magnetic properties of Nb-doped (FeZrB)100-xNbx alloy are investigated by X-ray diffraction (XRD), differential scanning calorimetry and vibrating sample magnetometer. The fully amorphous structure of the as-quenched ribbons is confirmed by the XRD pattern. With increasing Nb, the glass transition temperature and the onset crystallization temperature are increased, indicating increased stability of the amorphous structure. For x=1, the saturation

L. H. Kong; Y. L. Gao; T. T. Song; Q. J. Zhai

2011-01-01

414

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

Microsoft Academic Search

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

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

2010-01-01

415

Properties of a magnetic superconductor with weak magnetization-application to ErNi2B2C  

NASA Astrophysics Data System (ADS)

Using a Ginsburg-Landau free-energy functional, we study the H-T phase diagram of a weak magnetic superconductor, where the magnetization from the magnetic component is marginal in supporting a spontaneous vortex phase. In particular, the competition between the spiral state and spontaneous vortex phase is analysed. Our theory is applied to understand the magnetic properties of ErNi2B2C.

Ng, T.-K.; Leung, W.-T.

2001-03-01

416

Optical, Electrochemical, and Magnetic Properties of Pyrrole- and Thiophene-Bridged 5,15-Diazaporphyrin Dimers.  

PubMed

The first examples of pyrrole- and thiophene-bridged 5,15-diazaporphyrin (DAP) dimers are prepared through Stille coupling reactions of nickel(II) and copper(II) complexes of 3-bromo-10,20-dimesityl-5,15-diazaporphyrin (mesityl=2,4,6-trimethylphenyl) with the respective 2,5-bis(tributylstannyl)heteroles. The effects of the heterole spacers and meso nitrogen atoms on the optical, electrochemical, and magnetic properties of the DAP dimers are investigated by UV/Vis absorption spectroscopy, density functional theory calculations, magnetic circular dichroism spectroscopy, cyclic voltammetry, and EPR spectroscopy. The heterole spacers are found to have a significant impact on the electronic transitions over the entire ?-system. In particular, the pyrrole-bridged DAP dimers exhibit high light-harvesting potential in the low-energy visible/near-infrared region owing to the intrinsic charge-transfer character of the lowest excitation. PMID:25429923

Omomo, Satoshi; Maruyama, Yasuhisa; Furukawa, Ko; Furuyama, Taniyuki; Nakano, Haruyuki; Kobayashi, Nagao; Matano, Yoshihiro

2014-11-27