稀土正铁氧体Sm_(0.8)Tb_(0.2)FeO_3单晶的生长及性能（英文）

Crystal Growth and Characterization of the Rare-earth Orthoferrite Sm_(0.8)Tb_(0.2)FeO_3 Single Crystal

利用光学浮区法生长Sm_(0.8)Tb_(0.2)FeO_3单晶,采用劳尔背衍射仪对样品质量进行检测并定向。测试了c-切Sm_(0.8)Tb_(0.2)FeO_3单晶在零场冷却模式的磁温曲线,发现其自旋重取向温度范围为360~400 K。总结以前的工作发现Sm1-xTbxFe O_3系列材料的自旋重取向温度随着稀土铽(Tb)含量的增加而线性减小,这表明Sm_(1-x)Tb_xFe O_3系列材料中Fe^(3+)-Re^(3+)之间的超交换作用发生变化。热膨胀测试结果发现Sm_(0.8)Tb_(0.2)FeO_3存在三个温度转变区域:~250 K、350~480 K和~700 K。250 K发生的不正常相变是由于铁离子弱铁磁矩诱导的稀土离子磁矩方向的改变造成的,350~480 K是由于在这一温度范围发生铁离子自旋重取向,而~700 K发生的相变是由于铁离子自旋由反铁磁有序到顺磁无序的磁转变。

Sm0.8Tb0.2FeO3 single crystal was grown by the floating zone method. Laue back reflection was used to check the crystal＇s quality and orientation. The temperature dependence of the magnetization under ZFC process was measured in an external field 500 Oe along c-axis. A clear spin reorientation is observed in the range of 360-400 K. Considering the recent report that the spin reorientation transition temperature of Sm1-xTbxFeO3 is linear decreased with the increase of Tb ions content, the present data reveals the changed Fe^3＋-Re^3＋ super-exchange interaction. The curve of temperature dependence of thermal expansion exhibits three phase transitions at about 250 K, 350-480 K, and 700 K, respectively. The abnormal phase transition observed at 250 K may be resulted from the change of rare earth ions moment orientation polarized by Fe^3＋ sub-lattice net moment. The spin reorientation transition takes place in a temperature range from 350 K to 480 K. The iron spins transform from antiferromagnetic ordered arrangement to paramagnetic disordered arrangement at -700 K.