Al(Ga)原子择优占位对Gd_2Co_(17)化合物磁晶各向异性的影响

Influence of site preference of Al(Ga) atoms on magneto crystalline anisotropy of Gd_2Co_17 compounds

用磁性测量和磁取向粉末X射线衍射方法,研究了Gd2Co17-xMx(M=Al,Ga;x≤4)化合物的磁晶各向异性与Al(Ga)原子浓度的依赖关系.随着x的增加, Gd2Co17-xAlx(x≥1)和Gd2Co17-xGax(x≥2)化合物的室温磁晶各向异性由易面转变为易轴;在Al、Ga原子的浓度分别为x=0.9和x=1.8附近时,室温各向异性常数K1由负变正,在x=3时达到最大值,且含Al化合物的K1最大值约为含Ga化合物的四倍根据Al(Ga)原子在Gd2Co17化合物不同Co晶位择优占位的事实,讨论了Co亚点阵磁晶各向异性的演变.结果表明, Al原子择优占据6c晶位是导致Al原子对Co亚点阵各向异性正贡献大于Ga原子的主要原因.

Al(Ga) concentration dependence of the magnetocrystalline anisotropy of Gd2Co17-xMx (M=Al, Ga&le4) compounds was investigated by magnetic measurements and X-ray diffraction on magnetically aligned powders. There is a change of magnetocrystalline anisotropy at room temperature from planar to axial for Gd2Co17-xAlx (≥1) and Gd2Co17-xGax (x≥2) with increasing x. The sign reversal of the anisotropy constants K1 at room temperature occurs around x=0.9 and x=1.8 for Al-containing and Ga-containing compounds, respectively. The maximum positive value of K1 is reached in compounds for x=3, and the value of Al-containing compounds is about three times higher than that of Ga-containing compounds. The evolution of Co-sublattice magnetocrystalline anisotropy is explained in terms of preferred site occupancy of Co sites in Gd 12Co 17 compound by Al(Ga). The results show that strong preferential occupancy by Al of 6c sites results in Al atom having a much stronger positive contribution to Co-sublattice anisotropy than Ga atom.