The samples of La0.80Sr0.15Ag0.05 Mn O3/x(Cu O)(x = 0, 0.05, 0.10, 0.15, 0.20) were prepared by the solid-state reaction method, and the structure of the samples 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(q-T) curves, q-T fitted curves, and magnetoresistance–temperature(MR-T) curves.The results indicate that q-T data can be fitted by the formula q = q0 AT2 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 MgYCo_4 and MgYNi_4 phases in AuBe_5-type structure.The obtained values of cohesive energy as well as formation energy prove that the MgYCo_4 and MgYNi_4 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 MgYCo_4 phase is 19.06 μ_B per unit cell mainly owed to the 3d state of Co atom,and the MgYNi_4 phase exhibits no magnetism.Both the trigonal shear constant C_(44) and the shear modulus G of the Mg YNi_4 phase are larger than those of the MgYCo_4 phase.Plasticity of alloys has been estimated by the C_(11)-C_(12) and Young's modulus E,and C_(12)-C_(44),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 MgYCo_4 phase has better plasticity as well as ductility,compared with the MgYNi_4 phase.
Na WangWei-Bing ZhangBi-Yu TangEn-Jie HeMao-Lian Zhang
