【摘要】 通过磁性测量和X-射线衍射研究了Gd2Co17-xAlx化合物的结构和磁晶各向异性。当x≤4时,样品具有菱方Th2Zn17型结构,x=5时,具有六方CaCu5型结构。随着Al浓度增加,晶格常数和单胞体积单调增大,而居里温度和自发磁化强度近似线性地减小;在x≥1时,观察到Co亚点阵的磁晶各向异性变号,室温易磁化方向由易面转变为易轴,且易轴各向异性场和各向异性常数随Al原子浓度增加出现极大值;基于补偿温度(65K)下自由粉末颗粒的磁化曲线,导出了亚点阵间的分子场系数和Gd-Co交换耦合常数,结果表明,Al原子对Gd-Co交换耦合作用的影响较小。根据Al原子在Co亚点阵4种晶位的择优占位,分析了磁晶各向异性的演变。更多还原

【Abstract】 The structure and the magnetocrystalline anisotropy of Gd2Co17 Alx compounds were investigated by magnetic measurements -x and X-ray diffraction. All samples have the rhombohedral Th2Zn17 structure for x ≤ 4 but the hexagonal CaCu5 structure for x = 5. There is a monotonic increase of the lattice parameters and unit-cell volume and an almost linear decrease of the Curie temperature and spontaneous magnetization, respectively, with the increase of Al concentration. It was observed that the sign reversal of the Co-sublattice anisotropy occur,the easy magnetization direction switching at room temperature from perpendicular to the c-axis to parallel to the c-axis for the samples with x ≥ 1, and also the maximum in both anisotropy field and anisotropy constant exists with the increase of Al concentration. The inter-sublattice molecular-field coefficient and Gd-Co exchange coupling constant were derived from the magnetic isotherm at compensation temperature (65 K) made on free powder particles, and found to be not much influence of Al substitution on the strength of the Gd-Co exchange coupling. The evolution of magnetic anisotropy is analyzed mainly in terms of the preferential substitution of Al into the four different crystallographic Co sites for Co-sublattice.更多还原