The samples of La0.80Sr0.15Ag0.05MnO3/x（CuO） （x = 0, 0.05, 0.10, 0.15, 0.20） were prepared by the solid-state reaction method, and the structure of the sampies was detected by X-ray diffraction （XRD）, scanning electron microscope （SEM） equipped with energy dispersive spectroscopy （EDS）, electric transport mechanism, and magnetoresistance enhancement, and the temperature stability of magnetoresistance of the samples was studied through resistivity-temperature （ρ-T） curves, ρ-T fitted curves, and magnetoresistance-temperature （MR-T） curves. The results indicate that ρ-T data can be fitted by the formula ρ = ρ0 ＋ AT^2 very well, and the electric transport mechanism of all the samples in metal-like area is the scattering of single magneton upon spin electron; the magnetoresistance of composite samples is far larger than that of the original material, and the MR peak value of the sample with x = 0.20 is nearly 4 times as large as that of the sample with x = 0; composite samples have comparatively good temperature stability of magnetoresistance in the temperature range of 200-260 K, and the magnetoresistance of the sample with x = 0.15 almost does not change with temperature and keeps at （5.03 ± 0.20） % in the temperature range of 210-260 K.
用固相反应法制备了Y1-xDyxCrO3(x=0,0.1)多晶样品。通过X射线衍射(XRD)图谱检测了样品的结构,测量了样品的磁性,作了磁化强度-温度(M-T)曲线、磁化强度-磁场(M-H)曲线,研究了Dy3+替代Y3+对Y1-xDyxCrO3体系磁性质的影响。结果表明,Dy3+替代多铁性YCrO3中的Y3+对YCrO3的磁性有效大影响。YCrO3在奈尔温度TN=139 K以下呈倾角反铁磁,显示弱铁磁性;Dy3+替代Y3+后的Y0.9Dy0.1CrO3样品,在50 K
First-principles calculations have been performed to study the structural, mechanical and magnetic properties of the MgYCo4 and MgYNi4 phases in AuBes-type structure. The obtained values of cohesive energy as well as formation energy prove that the MgYCo4 and MgYNi4 phases have a good combination of structural stability and alloying ability, which is also supported by electronic structure. It is found that the magnetic moment of the MgYCo4 phase is 19.06 ktB per unit cell mainly owed to the 3d state of Co atom, and the MgYNi4 phase exhibits no magnetism. Both the trigonal shear constant C44 and the shear modulus G of the MgYNi4 phase are larger than those of the MgYCo4 phase. Plasticity of alloys has been estimated by the C11-C12 and Young＇s modulus E, and C12-C44, shear to bulk modulus ratio G/B and Poisson＇s ratio v have been studied to predict the ductility of alloys. According to the calculated results, the MgYCo4 phase has better plasticity as well as ductility, compared with the MgYNi4 phase.
Na WangWei-Bing ZhangBi-Yu TangEn-Jie HeMao-Lian Zhang
