代In的BCVIG单晶的磁光克尔旋转

我们测量了分子式为{Bi_3-2xCa_2x}[Fc_2-yIn_y](Fe_{(3x)Vx)O12的铁石榴石单晶(简记为代In的BCVIG)在0.45—0.80μm内的饱和极向磁光克尔旋转谱。在0.47μm附近观察到一个强的旋转峰值。通过改变In,V(Bi)的替代量获得了室温下磁矩抵消点附近0.47μm磁光旋转值与成份的关系。发现当替代量的变化通过磁矩抵消点时,克尔旋转的符号突然由正变负,但其绝对值并不依替代量趋近磁矩抵消点(总4πMs下降)而逐渐下降。还发现In的代入使磁光旋转有所增强,在y≈0.15时增强最大。借助总磁光旋转为Bi增强了的次点阵磁光旋转迭加的模型解释了代In引起的旋转增强。按此拟合实验结果导出了0.47μm下四、八面体次晶格旋转系数之比为α4/α8≈1.5即单位Fe³⁺在四面体比在八面体对磁光旋转的贡献大。实验结果还表明,在x<1.0的配方区,并有小量In代入(y<0.15)时可望得到大磁光旋转材料。考虑到低而可变的4πMs,高的居里点和相当大的磁光旋转,该配方区的代In的BCVIG在磁光各种应用中将是强有力的竞争者。关键词：}

THE MAGNETO-OPTIC KERR ROTATION OF INDIUM-SUBSTITUTED SINGLE CRYSTAL BCVIG

We have measured the saturated polar Kerr rotation of In-substituted single crystal BCVIG, {Bi_3-2xCa_2x}[Fc_2-yIn_y] (Fe_{(3x)Vx)O12, in the spectra range of 0.45-0.80 μm. A rotation peak near 0.47 μm was found. The room temperature dependence of the rotation peak value 2θK(0.47μm) on the composition was obtained by varying the substitution quantity of In³⁺ and Bi³⁺. It was found that the Kerr rotation change sign abruptly when varying the composition across the magnetization compensation point, however, the absolute value of the rotation does not reduce when the composition approaches that point, while the total magnetization 4πMs, does decrease, we also found that, with the In³⁺ content increasing, the Kerr rotation is "enhanced" at first, reaching a maximum at y～0.15, and then reduces. Using a model that the total Kerr rotation is the Bi³⁺ enhanced superposition of the sublattice Kerr rotation, we explained the "enhancement" of Kerr rotation by indium substitution. From fitting the experiment results, we deduced the ratio of the sublattice rotation coefficients (α4/α8) to be about 1.5, that is, the absolute contribution of every Fe³⁺ on tetrahedral site to the magneto-optic rotation is about 1.5 times as large as that on octahedral site. The results demonstrated that a good magneto-optic material can be synthesized in x<1.0 composition region with small amount of In³⁺ substitution. Considering its low and variable magnetization, high Curie temperature and rather large magneto-optic rotation, the In-BCVIG system, surely, is a promising cadidate in the variety of usage of the magneto-optic devices.}