Y_2Fe_(15)Al_2化合物的反常热膨胀及本征磁致伸缩(英文)

THERMAL EXPANSION ANOMALY AND SPONTANEOUS MAGNETOSTRICTION OF Y_2Fe_(15)Al_2COMPOUND

通过X射线衍射及磁测量手段研究了Y2Fe15Al2化合物的结构及磁学性质。结果表明:Y2Fe15Al2化合物具有六角相的Th2Ni17型结构。X射线热膨胀测量表明:在363～466 K的温度范围内,Y2Fe15Al2化合物出现负热膨胀现象,其平均热膨胀系数为α= -2.45 × 10-5/K。通过比较实际测量得到的晶格参数和外延计算得到的顺磁态的晶格参数之间的差别,在282～466 K的温度区间内计算了化合物的本征磁致伸缩系数。结果表明:化合物的本征体磁致伸缩随着温度的升高从282 K时的 11.3 × 10-3下降到466 K时的接近于零;化合物沿 c 轴方向和基面内的本征线磁致伸缩都随着温度的升高而下降,并且在400 K以下沿c轴方向的本征线磁致伸缩比基面内的本征线磁致伸缩大,这表明沿c轴方向的磁弹耦合强度高于基面内的磁弹耦合强度。

The structure and magnetic properties of a Y2Fe15Al2 compound have been investigated by means of X-ray diffraction and magnetization measurements. The Y2Fe15Al2 compound has a hexagonal Th2Nil7-type structure. Negative thermal expansion was found in the Y2Fe15Al2 compound in the temperature range from 363 to 466 K by X-ray dilatometry. The coefficient of the average thermal expansion of the compound is -2.45 × 10^-5/K. The spontaneous magnetostrictive deformations from 282 to 466 K have been calculated by means of the differences between the experimental values of the lattice parameters and the corresponding values ex-trapolated from the paramagnetic range. The results show that the volume magnetostrictive deformation ωs decreases from 11.3× 10^-3 to near zero with the temperature increasing from 282 to 466 K. The spontaneous linear magnetostrictive deformations λc along the c axis and λa along the a axis in the basal plane decrease with the increase of temperature and λc is much larger than λa at the same temperature below 400 K. This shows that the intensity of the magneto-elastic effect along the c axis for the Y2Fe15Al2 compound is much stronger than that along the a axis in the basal plane.