Structural Transition and Magnetic Property of Bi1-xYbxFeO3

Bi1-xYbxFeO3（0〈x〈0.2） powders have been synthesized using a sol-gel method. The X- ray diffraction data show a structural transition from the rhombohedral R3c phase to the orthorhombic Pnma phase between x=0.1 and 0.125, which should induce a ferroelectric- paraelectric transformation. The phase transition is also proven by the Raman spectroscopy. A moderate signal on magnetization appears to illustrate the enhancement of magnetization at the transformation boundary, which is suggested to be the destruction of the spin cycloid structure at low concentration. The appearance of antiferromagnetic ordering is proposed to account for the afterward reduction of the magnetization at high concentration.

Structural and magnetic transition in stainless steel Fe-21Cr-6Ni-9Mn up to 250 GPa

Stainless steel Fe-21Cr-6Ni-9Mn （SS 21-6-9）, with ~21% Cr, ,~6% Ni, and ~ 9% Mn in weight percentage, has wide applications in extensive fields. In the present study, SS 21-6-9 is compressed up to 250 GPa, and its crystal structures and compressive behaviors are investigated simultaneously using the synchrotron angle-dispersive x-ray diffraction technique. The SS 21-6-9 undergoes a structural phase transition from fcc to hcp structure at ~ 12.8 GPa with neglectable volume collapse within the determination error under the quasi-hydrostatic environment. The hcp structure remains stable up to the highest pressure of 250 GPa in the present experiments. The antiferromagnetic-to-nonmagnetic state transition of hcp SS 21-6-9 with the changes of inconspicuous density and structure, is discovered at ~50 GPa, and revealed by the significant change in c/a ratio. The hcp SS-21-6-9 is compressive anisotropic： it is more compressive in the c-axis direction than in the a-axis direction. Both the equations of states （EOSs） of fcc and hcp SS 21-6-9, which are in accordance with those of fcc and hcp pure irons respectively, are also presented. Furthermore, the c/a ratio of hcp SS 21-6-9 at infinite compression, R∞, is consistent with the values of pure iron and Fe-10Ni alloy.

Structural and Magnetic Properties of MnO-P_2O_5-PbO Glasses

The xMnO(100-x)[2P2O5.PbO] glasses were prepared with MnO concentration being in the range of 0≤x≤50 mole fraction and were investigated by EPR spectroscopy and magneticsusceptibility measurements. Octahedral symmetric sites tetragonally distorted were detected for x≤5 mole fraction MnO. Only Mn2+ ions were identified in these glasses, involved in dipoledipole interactions

Tunable Electronic and Magnetic Properties from Structure Phase Transition of Layered Vanadium Diselenide

The atomic geometry, structure stability, electronic and magnetic properties of VSe2 were systematically investigated based on the density functional theory（DFT）. Varying from 3D to 2D four VSe2 structures, bulk 2H-VSe2 and 1T-VSe2, monolayer H-VSe2 and T-VSe2 are all demonstrated as thermodynamically stable by lattice dynamic calculations. More interestingly, the phase transition temperature is dramatically different due to the lattice size. Finally, owing to different crystal structures, H-VSe2 is semimetallic whereas T-VSe2 is totally metallic and also they have different magnetic moments. Our main argument is that being exfoliated from bulk to monolayer, 2H-VSe2 transforms to T-VSe2, accompanied by both semimetallic-metallic transition and dramatic magnetic moment variation. Our calculations provide a novel structure phase transition and an efficient way to modulate the electronic structure and magnetic moment of layered VSe2, which suggests potential applications as high-performance functional nanomaterial.

Structural and magnetic properties of (Sm_0.5Nd_0.5)_2(Fe_(1-x)Co_x)_(17)compounds

The structure, magnetization, and magnetocrystalline anisotropy wereinvestigated using X-ray diffraction, vibrating sample magnetometer, and AC susceptibility-meter Itis found that the microstructure of (Sm_(0.5)Nd_(0.5))_2(Fe_(1-x)Co_x)_(17) alloys is an(Sm,Nd)_2(Fe,Co)_(17) phase with the rhombohedral Th_2Zn_(17)-type structure. The Curie temperatureT_c increases with the Co concentration increasing, and the magnetization first increases as the Cocontent increases in (Sm_(0.5)Nd_(0.5))_2(Fe_(1-x)Co_x)_(17) alloys and then decreases slowly. Theeasy magnetization direction (EMD) of (Sm_(0.5)Nd_(0.5))_2(Fe_(0.25)Co_(0.75))_(17) is along thec-axis and a strong enhancement of the crystalline anisotropy energy constant K is produced by theaddition of some Co atoms. The anisotropy energy constant reaches the maximum when x = 0.75 and thendecreases slowly with the Co content further increasing. The(Sm_(0.5)Nd_(0.5))_2(Fe_(0.25)Co_(0.75))_(17) compound is an optical candidate for the new permanentmagnet, which possesses a high magnetization, a high Curie temperature, and a large anisotropy.

Influence of Substitution of Transition Elements for Fe on the Structure and Magnetic Properties of the Nd_(16)Fe_(75)AI_2B_7 AHoy

1.IntroductionThe influence of substitution of variouselements for Fe on the magnetic propertiesof the NdFeBalloy has been investi-gated by several authors,among which theAl substitution can increase the coercivity[1]and the addition of both Co and Al has beenproved to have a positive effect on im-proving both the coercivity and other per-

Crystal structures, phase relationships, and magnetic phase transitions of R_5M_4 compounds (R = rare earths, M = Si, Ge)

Our recent studies of the crystal structures, phase transitions, and magnetic properties of intermetallic compounds RsM4 （R = rare earths; M = Si, Ge） are reviewed briefly. First, crystal structures, phase relationships, and magnetic prop- erties of several 5：4 compounds, including Nd5 Si4-xGex, Pr5 Si4_xGex, Gds-xLaxGe4, La5 Si4, and Gd5 Sn4, are presented. In particular, the canted spin structures as well as the magnetic phase transitions in PrsSi2Ge2 and PrsGe4 investigated by neutron powder diffractions and small-angle neutron scattering are reviewed. Second, the crystal structures and magnetic properties of the most studied compounds Gds（Si,Ge）4 are summarized. The focus is on the parent compound GdsGe4, which is an amazing material exhibiting magnetic anisotropy, angular dependent spin-flop transition, metastable magnetic response, Griffiths-like phase, thermal effect under pulsed fields, antiferromagnetic and ferromagnetic resonances, pro- nounced effects of impurities, and high-field induced magnetic transitions.

Levitation of Extended States in a Random Magnetic Field with a Finite Mean

We study the localization properties of electrons in a two-dimensional system in a random magnetic field with the average and the amplitude of the magnetic field fluctuations δB. The localization length of the system is calculated by using the finite-size scaling method combined with the transfer-matrix technique. In the case of weak δB, we find that the random magnetic field system is equivalent to the integer quantum Hall effect system, namely, the energy band splits into a series of disorder broadened Landau bands, at the centers of which states are extended with the localization length exponent . With increasing δB, the extended states float up in energy, which is similar to the levitation scenario proposed for the integer quantum Hall effect.

Magnetic Field Induction and Time Intervals of the Electron Transitions Approached in a Classical and Quantum-Mechanical Way

The motion of electron wave packets of a metal is examined classically in the presence of the magnetic field with the aim to calculate the time intervals between two states lying on the same Fermi surface. A lower limiting value of the transition time equal to about 10–18 sec is estimated as an average for the case when the states are lying on the Fermi surface having a spherical shape. Simultaneously, an upper limit for the electron circular frequency in a metal has been also derived. A formal reference of the classical transition time to the time interval entering the energy-time uncertainty relations known in quantum mechanics is obtained.

Effects of melt overheating degree on undercooling degree and amorphous forming of Nd_9Fe_(85-x)Ti_4C_2B_x(x=10, 12) magnetic alloys

The effectsof melt overheating degree on the undercooling degree and resultant solidification structures of Nd9Fe85-xTi4C2Bx（x=10, 12） glass-forming alloyswerestudied by differential thermal analysis combining with solidification structure analysis. The results indicate that the undercooling degree of Nd9Fe85-xTi4C2Bx（x=10, 12） alloys significantly increaseswith the rise of melt overheating degree, and two overheating degree thresholds corresponding to the drastic increase of the mean undercooling degree are found for each of the alloys. The existence of two turning points of the mean undercooling degreescan be linked to the structure transitions inside the overheated melts, which result in the evident increase of volume fraction of amorphous phasein the solidified structures.

NMR Study on Structural Characteristics of Rare Earth Doped Boro-Alumino-Silicate Glasses

The structural characteristics of Re2O3 doped B2O3-Al2O3-SiO2 glasses and factors such as the component and heat-treating conditions affecting the glass structure were investigated by magic angle spin nuclear magnetic resonance （MAS NMR） spectroscopy and differential thermal analysis （DTA）. It is found that, in B2O3-Al2O3-SiO2 glass, the boron （4）, and Al（5）, Al（6） changes to Al（4）. On the other hand, compared with Ba^2＋ , RE^3＋ can accumulate the boron network because of its higher field strength, which results in a large network structure. With the increase of samarium oxide, the silicate coordination Qa（3T） will have predominance gradually. Heat-treatment has little effect on the boron and aluminum coordination sites in the glass structure.

Correlation between Structure and Thermal Properties of N-vinyl-3-alkylimidazolium Magnetic Ionic Liquids

Influence of structural variations of N-vinylimidazolium tetrahalogenidoferrate(III) magnetic ionic liquids(MILs) on thermal properties was investigated. Using Gaussian09/B3 PW91/6-311 G(2d, p) density functional methods, the microstructure of the MILs were analyzed. With differential scanning calorimeter(DSC) and thermogravimetric analysis(TGA), the thermal properties of the MILs were performed. The results showed that the interaction energies of ion pairs decreased, the crystallization temperature increased first and then decreased, and the surfusion first decreased and then increased with the elongation of the alkyl chain length on cation;with the increase of Br atom, the interaction energies of ion pairs increased;the interaction energies of ion pairs increased in the MILs with the same cation or anion, the nature of polarity of MILs increased and the melting point rose;as the cation or anion in MILs had a smaller size, it could have the solidsolid transition temperature. The results indicated that the decomposition temperature with the same type of MILs increased with the interaction energies of ion pairs. The interaction energy of ion pairs can be used to illuminate the correlation between the thermal properties and the structure of MILs. ILs possesses the properties of macromolecular.

Equilibrium folding and unfolding dynamics to reveal detailed free energy landscape of src SH3 protein by magnetic tweezers

Src SH3 protein domain is a typical two-state protein which has been confirmed by research of denaturant-induced unfolding dynamics.Force spectroscopy experiments by optical tweezers and atomic force microscopy have measured the force-dependent unfolding rates with different kinds of pulling geometry.However,the equilibrium folding and unfolding dynamics at constant forces has not been reported.Here,using stable magnetic tweezers,we performed equilibrium folding and unfolding dynamic measurement and force-jump measurement of src SH3 domain with tethering points at its N-and C-termini.From the obtained force-dependent transition rates,a detailed two-state free energy landscape of src SH3 protein is constructed with quantitative information of folding free energy,transition state barrier height and position,which exemplifies the capability of magnetic tweezers to study protein folding and unfolding dynamics.

Magnetic and electric characteristics and abnormality of low-temperature resistivity in La_(0.67–x)Er_xSr_(0.33)MnO_3(0.00≤x≤0.20) system

M-T curves, ρ-T curves, and MR-T curves of La0.67-xErxSr0.33MnO3(x=0.00, 0.10, 0.20) system were studied by experiments. The experiments showed that: with increasing the doping amount, the magnetic structure of the system transformed from long-range ferromagnetic ordering to spin-cluster glass state, and M-T curves bent up in the extremely low temperature range; the resistivity of the system increased with increasing doping amount and exhibited the minimum phenomenon of low-temperature resistivity. The variation of the magnetic and electric properties came from the extra magnetic coupling induced by the doping and from the Kondo effect induced by the lattice distortion and local magnetic moments which was similar to that induced by the scattering of magnetic impurities on electron spins. © 2009 The Chinese Society of Rare Earths.

Structures and magnetic properties of Fe and Ni monoatomic chains encapsulated by an Au nanotube

Structures and magnetic properties of transition metal （TM） Fe or Ni monoatomic chains （MACs） encapsulated by a Au （5, 5） nanotube （Fe@Au and Ni@Au） are investigated using the density functional theory （DFT）. The calculated results show that both Fe@Au and Ni@Au prefer to adopt ferromagnetic （FM） orders as ground states. In particular, the Fe@Au keeps the magnetic properties of free-standing Fe MAC, indicating that this system may be viewed as a new candidate in electromagnetic devices.

Structural phase transition, precursory electronic anomaly, and strong-coupling superconductivity in quasi-skutterudite (Sr1-xCax)3Ir4Sn13 and Ca3Rh4Sn13

The interplay between superconductivity and structural phase transition has attracted enormous interest in recent years. For example, in Fe-pnictide high temperature superconductors, quantum fluctuations in association with structural phase transition have been proposed to lead to many novel physical properties and even the superconductivity itself. Here we report a finding that the quasi-skutterudite superconductors （Sr1-xCax）3Ir4Sn13 （x = 0, 0.5, 1） and Ca3Rh4Snl3 show some unusual properties similar to the Fe-pnictides, through 119Sn nuclear magnetic resonance （NMR） measurements. In （Sr1-xCax）3Ir4Sn13, the NMR linewidth increases below a temperature T＊ that is higher than the structural phase transition temperature Ts. The spin-lattice relaxation rate （1/T1 ） divided by temperature （T）, 1/TI T and the Knight shift K increase with decreasing T down to T＊, but start to decrease below T＊, and followed by more distinct changes at Ts. In contrast, none of the anomalies is observed in Ca3Rh4Sn13 that does not undergo a structural phase transition. The precursory phenomenon above the structural phase transition resembles that occurring in Fe-pnictides. In the superconducting state of Ca3Ir4Sn13, 1/T1 decays as exp（-△/kBT） with a large gap △ = 2.21kBTc, yet without a Hebel-Slichter coherence peak, which indicates strong-coupling superconductivity. Our results provide new insight into the relationship between superconductivity and the electronic-structure change associated with structural phase transition.

Crystal growth of CeMn_(0.85)Sb_(2):Absence of magnetic order of Ce-sublattice

Single crystals of CeMn_(0.85)Sb_(2) have been successfully synthesized by using the Bi as flux.Analysis of single crystal x-ray diffraction data confirms that CeMn_(0.85)Sb_(2) crystallizes in the HfCuSi_(2)-type structure with the space group P4/nmm(No.129).In the case of H‖c,CeMn_(0.85)Sb_(2) displays a robust antiferromagnetic transition at~160 K for Mn-sublattice,and there is no sign of magnetic order regarding Ce-sublattice.In the case of the Mn-sublattice shows signs of magnetic order at 160 K and 116 K,indicating a possible spin reorientation.There is no sign of magnetic order for the Cesublattice either,but,alternating current magnetic susceptibility measurements reveal a spin glass state below 18 K in the case of H⊥c.Isothermal magnetization curves measured below magnetic order with H⊥c show saturation and even large hysteresis at 2 K,indicating the presence of a ferromagnetic component.In addition,a field-induced spin-flop transition is observed in the case of H⊥c,indicating a field-induced spin reorientation of Mn spins.Electrical resistivity measurements indicate a metallic nature for CeMn_(0.85)Sb_(2) and large anisotropy which is consistent with its quasi-two-dimensional layered structure.

Study of magnetic and optical properties of Zn1-xTMxTe(TM = Mn,Fe,Co,Ni) diluted magnetic semiconductors：First principle approach

We present structural,magnetic and optical characteristics of Zn_（1-x）TM_xTe（TM = Mn,Fe,Co,Ni and x = 6.25%）,calculated through Wien2 k code,by using full potential linearized augmented plane wave（FP-LAPW） technique.The optimization of the crystal structures have been done to compare the ferromagnetic（FM） and antiferromagnetic（AFM） ground state energies,to elucidate the ferromagnetic phase stability,which further has been verified through the formation and cohesive energies.Moreover,the estimated Curie temperatures T_c have demonstrated above room temperature ferromagnetism（RTFM） in Zn_（1-x）TM_xTe（TM =Mn,Fe,Co,Ni and x= 6.25%）.The calculated electronic properties have depicted that Mn- and Co-doped ZnTe behave as ferromagnetic semiconductors,while half-metallic ferromagnetic behaviors are observed in Fe- and Ni-doped ZnTe.The presence of ferromagnetism is also demonstrated to be due to both the p-d and s-d hybridizations between the host lattice cations and TM impurities.The calculated band gaps and static real dielectric constants have been observed to vary according to Penn＇s model.The evaluated band gaps lie in near visible and ultraviolet regions,which make these materials suitable for various important device applications in optoelectronic and spintronic.

Structure and Magnetic Properties of a New Oxohalogenide Compound Ba_7CoV_6O_(21)Cl_4

A new oxohalogenide compound BaTCoV6021C14 was synthesized by a conven- tional high-temperature solid state reaction. The title compound is found to crystallize in the orthorhombic system of space group Cmcm with a = 16.726（4）, b = 10.568（3）, c = 14.808（4） A, V = 2617.4（12） A3, Z= 2, Mr = 1803.68, Dc= 3.411 g/cm3,/t= 11.396 mm1, F（000） = 3172, the final R = 0.0314 and wR = 0.0750 for 1531 observed reflections with I 〉 2δ（/）. Co2＋ ions are coordinated by four O and two Cl atoms, forming a COO4C12 octahedron, while V atoms are tetrahedrally coordinated, forming （V207）4＂ groups. The structure of Ba7CoV6021Ch exhibits a pseudo-one- dimensional chain running along the c-axis. Magnetic measurements confirm that Ba7CoV6021Cl4 shows a paramagnetic behavior down to 2 K.