Pr_2AlFe_(16-x)Mn_x化合物的反常热膨胀及磁性

Thermal expansion anomaly and magnetic properties in Pr_2AlFe_(16-x) Mn _x compounds

通过X射线衍射及磁测量实验研究了Pr2 AlFe16-xMnx 化合物的结构与磁性 ,结果表明Pr2 AlFe16-xMnx 化合物具有Th2 Zn17型结构 ;随着锰替代量的增加 ,化合物的单胞体积呈现先小后大的非线性增加 ,分析表明该类化合物在其磁相变点附近存在较大的正的本征磁致伸缩现象。进一步对Pr2 AlFe13 Mn3 化合物进行的变温X射线衍射研究表明 ,该化合物在其居里点附近 (180～ 198K)存在负热膨胀现象 ,其热膨胀系数为 -3 .6× 10 -4/K。磁性测量表明随着锰含量的增加Pr2 AlFe16-xMnx 化合物的居里温度及自发磁化强度都急剧下降 ,对这些现象进行了解释。

Structure and magnetic properties of Pr 2AlFe 16- x Mn x compounds have been investigated by means of X ray diffraction and magnetization measurements. The Pr 2AlFe 16- x Mn x compounds have a rhombohedral Th 2Zn 17 type structure. Their unit cell volumes increase slowly with increasing x , then rapidly with the further increase of x . This implies there is a positive spontaneous volume magnetostriction in the magnetic state for Pr 2AlFe 16- x Mn x compounds. X ray diffraction of Pr 2AlFe 13 Mn 3 compound from 160K to 300K shows that there appears a negative coefficient of thermal expansion near its Curie temperature,α≈-3.6×10 -4 /K, from 180K to 198K. The magnetization measurements shows that the Curie temperature and the saturation magnetization of these compounds decrease rapidly with increasing x .