Magnetic properties of Y(Fe0.95Mn0.05)2 compound

Mössbauer spectroscopy, magnetization and X-ray diffrraction measurements of the ternary compound Y(Fe_0.95Mn_0.05)₂ prepared by melting were performed in order to investigate the effect of the substitution of Mn on the magnetic properties of YFe₂. The experimental results show change of the lattice parameter. The magnetization and the Curie temperature decrease with substitution of Fe by Mn.     

Electronic density of states in pseudobinary compounds Y(Fe-Co)2 and Y(Mn-Co)2

Densities of states in pseudobinary compounds are calculated by making use of the coherent potential approximation (CPA) [3] and the recursion method. Applications are made for Y(Fe-Co)₂, Y(Mn-Co)₂ and Zr(Fe-Co)₂. The total and local magnetic moments of Y(Fe-Co)₂ and Zr(Fe-Co)₂ are calculated and compared with the experimental results.     

Magnetic properties of Gd-substituted Y2Co7 hydrides

The magnetization of (Y_1−yGd_y)₂Co₇H_x(y = 0.1, 0.2, 0.4 and 1; 0 ⩽ x ⩽ 3) has been measured at 4.2K up to 30T. The exchange field introduced by the Gd substitution enhances the Co moment in the hydrides. The origin of the disappearance of ferromagnetism in the β_L hydride (y = 0; x = 1.7) has been discussed.     

Magnetic properties of CuInSe2-(FeSe)2 solid solutions

Measurements of the magnetic characteristics of Cu_{1 ? x} In_{1 ? x} Fe_2x Se₂ solid solutions and their approximation by Langevin and Curie equations show that the properties observed in samples are the result of antiferromagnetic clusters in which magnetic moments fall to ～0.8 μ_B/atom as x rises, confirming that the antiferromagnetic interaction in the samples grows stronger.     

混合自旋反铁磁材料Y2BaNiO5的磁学和热力学性质

在格林函数的理论框架下,采用一维自旋为1的各向异性Heisenberg模型来讨论Y2BaNiO5材料的磁学和热力学性质.得到了它的自旋关联函数、低激发谱、基态能(Eg)、比热(C)和静态磁化率(χ)在不同交换各向异性因子下的性质,所得结果与实验和数值模拟结果完全一致.     

Magnetic properties of (La,Gd)Al2 alloys

Theac anddc susceptibilities of (La_1–x Gd _x )Al₂ alloys were measured for moderate Gd concentrations (0.01x0.08) between 0.05 and 4.2 K. Sharp spin glass like maxima in ^AC are observed at temperaturesT _f which scale asT _f /x 26 K for all samples. However, scaling of ^AC is not observed indicating that the RKKY interaction at short distances which becomes more important with increasing Gd concentration, is ferromagnetic in this system. The amplitudeV ₀ of the RKKY interaction is obtained from both the approach to the saturation magnetization and ^AC forT0, yielding a mean value ₀=(1.5±0.3) 10^–26 eV cm³ which is in agreement with that observed in other systems with Gd impurities. Furthermore, the inferred value of the exchange integral is in accord with other measurements (T _c depression, reverse resistance anomaly) on (La, Gd)Al₂. A superposeddc magnetic field rounds the maximum of ^AC and shifts it to lower temperatures. ^AC is completely flat below 4.2 K in a field which saturates the isothermal remanent magnetization, showing once again the correlation between the peak in ^AC and the onset of irreversible properties.This work is part of the research program of the Sonderforschungsbereich 125 Aachen/Jülich/Köln     

氮掺杂(1120) ZnO 薄膜磁性质研究

采用基于密度泛函理论(DFT)和局域密度近似(LDA)的第一性原理分析了氮掺杂(1120) ZnO 薄膜的磁性质.首先,研究了一个N原子掺杂ZnO薄膜的磁性质,结果表明N 2p,O 2p和Zn 3d 发生自发自旋极化.其次,研究了二个N原子掺杂ZnO薄膜的磁性质,9个不同几何结构的计算结果表明N原子之间具有FM耦合稳定性,而且具体分析了N掺杂ZnO铁磁稳定性的产生原因.最后,讨论了氮 关键词： 第一性原理 半导体 铁磁性     

Magnetic properties of the pseudo-binary Fe2(Nb1-xMnx)

The magnetic behavior of the pseudo-binary system Fe₂(Nb_1-xMn_x) is investigated by means of the experimental techniques of X-ray diffraction (XRD), Mössbauer Spectroscopy (MS) and magnetization studies. The XRD results indicate that, up to x=0.3, all samples are single phase with hcp structure. This corresponds to the solubility limit of manganese in this phase. Above x=0.3, all prepared samples present the coexistence of three phases, two with hcp structure and one fcc. The magnetization measurements at low temperatures indicate that the transition temperature increases with the addition of Mn atoms in the Fe₂Nb host (T_N=10 K) up to 58 K for x=0.1. The Mössbauer spectra were fitted with a quadrupole splitting distribution, which indicates that the average quadrupolar splitting increases slightly with the increase of the manganese concentration.     

Magnetic properties of RNi2Si2 compounds (R= rre earth)

We report an extensive study of the magnetic properties of tetragonal RNi₂Si₂ compounds (R=Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm), through resistivity, neutron diffraction, susceptibility and magnetization experiments. All compounds exhibit complex incommensurate antiferromagnetic structures, while a transition occurs in TbNi₂Si₂ between a modulated phase and a simple antiferromagnetic structure, stable at low temperature. The magnitude of the bilinear exchange interactions deviates from the Gennes law and the direction of the ordered magnetic moments presents anomalies across the series, including the probable existence of other types of interactions between the rare earth ions.     

Magnetic properties of Zr doped Y9Co7

Detailed measurements of magnetization and ac susceptibility at low temperatures of 1% Zr-substituted Y₉Co₇ are presented. All results are indicative of itinerant weak ferromagnetism withT _c ∼ 9.5 K. The zero-field magnetizations followT ² orT ^4/3 behaviour as in the Ni-substituted system. The estimated critical exponents areβ=0.38±0.03,γ=1.16±0.05. It is argued that the main effect of the non-magnetic Zr-substitution in Y₉Co₇ is to stabilize the ferromagnetic ordering by suppressing the ‘hopping’ of Co atoms along thec-axis sites of the hexagonal structure.     

Transport properties in the pseudobinary (Gd,Y) Al2 series

The temperature dependence of the electrical resistivity, the thermal conductivity and the thermopower of the cubic isostructural (Gd_xY_1–x)Al₂ series will be presented. The magnetic properties of this system are characterized by the existence of ferromagnetism for Gd concentrations x>0.3 while for low Gd contents cluster and spinglass behaviour is observed. The spin dependent scattering contribution to the transport phenomena has been obtained by comparing the experimental data of the magnetic compounds with those of the isostructural nonmagnetic YAl₂. For the ferromagnetic concentration range and forT>T _c (T _c =Curie temperature) we revealed a temperature independent contribution to the electrical resistivity, a contribution with a temperature variation of 1/T to the thermal resistivity and a linear temperature dependence of this part to the thermopower. These results are in good agreement with the temperature dependence calculated by solving the linearized Boltzmann equation for this type of scattering processes.     

Magnetic properties of RCr2Si2 compounds (R=Tb,Er)

We report on magnetic properties of RCr₂Si₂ compounds with R=Tb, Er. The polycrystalline samples were characterized by powder X-ray diffraction and found to be isostructurally crystallizing in the ThCr₂Si₂-type tetragonal structure. The samples were further investigated by specific heat, AC-susceptibility and magnetization methods in the temperature range 2–900 K and in magnetic fields up to 9 T. The magnetic measurements revealed the magnetic ordering of the rare-earth moments below about 2 K, whilst no high-temperature ordering of the Cr moments was observed. The evidence of for Cr magnetism is corroborated by results of first-principles calculations based on the density functional theory (DFT).     

Magnetic properties of poly(3-hexylthiophene)

A room temperature ferromagnetic phase is observed in samples of poly(3-hexylthiophene) partially doped with ClO₄⁻. The magnetic behavior presents a strong dependence on the sample preparation conditions, in particular, a dependence with the final potential of the sample after reduction. The origin of the ferromagnetism is proposed to be associated with interactions between spin 1/2 polarons formed in the polymeric chain upon doping. The dependence of saturation and spontaneous magnetization as the function of the final potential after reduction shows a way to control the magnetic properties of this polymer.     

Magnetic properties of multiferroics-semiconductors Eu(1-x)Ce(x)Mn2O5

Studies of magnetization, magnetoresistance, and magnetic oscillations in semiconductor-multiferroics Eu(1-x)Ce(x)Mn2O5 (x = 0.2-0.25) (ECMO) at temperatures ranging from 5 to 350 K in magnetic fields up to 6 T are presented. It is shown that phase separation and charge carrier self-organization in the crystals give rise to a layered superstructure perpendicular to the c axis. An effect of magnetic field cycling on the superstructure, magnetization, and magnetoresistance is demonstrated. X-ray diffraction studies of ECMO demonstrating the effect of magnetic field on the superstructure are presented. The de Haas-van Alphen magnetization oscillations in high magnetic fields and the temperature-induced magnetic oscillations in a fixed magnetic field are observed at low temperatures. Below 10 K the quantum corrections to magnetization due to the weak charge carrier localization in 2D superlattice layers occur. It is shown that at all the temperatures the Eu(1-x)Ce(x)Mn2O5 magnetic state is dictated by superparamagnetism of isolated ferromagnetic domains.     

Magnetic properties of R2Re2Si2C (R=Ho and Er)

We have investigated magnetic properties of R₂Re₂Si₂C (R=Ho and Er) using magnetic susceptibility, magnetization and heat capacity measurements. Both the materials order antiferromagnetically. The ordering temperatures (T_N) for Ho₂Re₂Si₂C and Er₂Re₂Si₂C are, ∼8.8 and ∼7.6 K, respectively. Our measurements indicate crystal field effects in the bulk properties of both these compounds. The experimental results have been analyzed by taking into account the effect of crystalline electric field and magnetic exchange interaction.     

Magnetic properties of (ErxY1−x)Al2: Magnetic measurements and neutron diffractions data

The ac susceptibility, the low field magnetization and neutron diffraction experiment have been performed for concentrations 0.1<x<1. For x<0.4 the typical spinglass properties have been observed: cusp in the susceptibility, the cusp is affected by small static magnetic fields of a few hundred Gauss. The thermal remanent magnetization has also been detected. However properties are also present for the high concentration x=0.6 or 0.8. Neutron diffraction experiments at the D1B of the ILL show that there exists $\text{no}$ sharp change from long range order to the spinglass regime. For higher x values approximately 80% of the Er ions form long range order whereas for x<40% most of the ions are in the frozen paramagnetic state. The magnetic phase diagram for the whole concentration range is discussed.