Magnetic properties and spontaneous distortion in TbCo2
Magnetic properties and spontaneous distortion in TbCo2
复制标题
DOI：
10.1088/0305-4608/9/5/005
复制
发表时间：
1979-05
期刊：
影响因子：
--
通讯作者：
D. Gignoux;F. Givord;R. D. L. Bâthie;F. Sayetat
中科院分区：
文献类型：
--
作者：
D. Gignoux;F. Givord;R. D. L. Bâthie;F. Sayetat
作者介绍了对 TbCo2 单晶进行的磁化强度测量以及通过 X 射线粉末衍射研究的自发变形。在低于 Tc (240K) 的任何温度下，容易磁化方向为 (111)，而最难磁化方向为 (100)。在Tc以下出现巨大的菱面体畸变；在 4.2K 时，立方体边缘之间的角度变化为 epsilon =4.4*10-3 rad。由于钴引起的各向异性可以忽略不计，作者根据作用于 Tb3+ 离子 7F6 基态多重态的三个贡献来分析结果：晶体场、交换场和磁弹性能。在 4.2K 时，由于 Tb 的各向异性非常高，沿 (100) 或 (110) 施加的 135 kOe 磁场不足以使磁化强度平行于这些轴对齐。与 TbFe2 一样，大的自发菱面体畸变是由与强晶体场效应相关的强分子场引起的。分子场几乎导致基本能级 Jz=6（μ Tb 大约=9 μ B），这是一个非常各向异性的 4f 分布，并且正如通常观察到的那样，结晶场本质上是由导带的 d 特性产生的。
The authors present magnetisation measurements performed on a single crystal of TbCo2 as well as spontaneous distortion studied by X-ray powder diffraction. At any temperature below Tc (240K) the easy magnetisation direction is (111) while the most difficult is (100). A huge rhombohedral distortion appears below Tc; at 4.2K the angular variation between the cube edges is epsilon =4.4*10-3 rad. The anisotropy due to cobalt being negligible, the authors have analyzed the results in terms of the three contributions acting on the 7F6 ground state multiplet of the Tb3+ ions: crystal field, exchange field and magnetoelastic energy. At 4.2K, as the anisotropy of Tb is very high, a 135 kOe field applied along the (100) or the (110) is not strong enough to align the magnetisation parallel to these axes. As in TbFe2, the large spontaneous rhombohedral distortion results from a strong molecular field associated with strong crystal field effects. The molecular field leads to almost the fundamental level Jz=6 ( mu Tb approximately=9 mu B) that is a very anisotropic 4f distribution and the crystalline field essentially arises, as generally observed, from the d character of the conduction band.