Institute of Physics ASCR, Cukrovarnická 10, 162 00 Prague 6, Czech Republic.
J Phys Condens Matter. 2014 Mar 19;26(11):116003. doi: 10.1088/0953-8984/26/11/116003. Epub 2014 Mar 3.
Crystal and magnetic structures of the x = 0.2 member of the La0.8-xTbxCa0.2CoO3 perovskite series have been determined from powder neutron diffraction. Enhancement of the diffraction peaks due to ferromagnetic or cluster glass ordering is observed below TC = 55 K. The moments first evolve on Co sites, and ordering of Ising-type Tb(3+) moments is induced at lower temperatures by a molecular field due to Co ions. The final magnetic configuration is collinear Fx for the cobalt subsystem, while it is canted FxCy for terbium ions. The rare-earth moments align along local Ising axes within the ab-plane of the orthorhombic Pbnm structure. The behavior in external fields up to 70-90 kOe has been probed by magnetization and heat capacity measurements. The dilute terbium ions contribute to significant coercivity and remanence that both steeply increase with decreasing temperature. A remarkable manifestation of the Tb(3+) Ising character is the observation of a low-temperature region with an anomalously large linear term of heat capacity and its field dependence. Similar behaviors are detected also for other terbium dopings x = 0.1 and 0.3.
钙钛矿型 La0.8-xTbxCa0.2CoO3（x=0.2）系列的晶体和磁性结构已通过粉末中子衍射确定。在 TC=55K 以下，观察到由于铁磁或团簇玻璃有序化导致的衍射峰增强。磁矩首先在 Co 位上演变，并且由于 Co 离子的分子场，在较低温度下诱导出 Ising 型 Tb(3+)磁矩的有序化。最终的磁构型是钴子系统的共线 Fx，而对于铽离子则是倾斜的 FxCy。稀土磁矩沿正交 Pbnm 结构的 ab 面内的局部 Ising 轴排列。通过磁化和热容测量研究了高达 70-90kOe 的外场中的行为。稀有的铽离子对显著的矫顽力和剩余磁化强度有贡献，这两者都随温度的降低而急剧增加。Tb(3+)Ising 特性的一个显著表现是观察到热容的低温区域具有异常大的线性项及其对磁场的依赖性。对于其他的铽掺杂 x=0.1 和 0.3，也检测到了类似的行为。
