Tm_2CrFe_(14.5)Si_(1.5)化合物的反常热膨胀性质研究

Negative Thermal Expansion of Tm_2CrFe_(14.5)Si_(1.5)

通过X射线衍射手段研究了Tm2CrFe14.5Si1.5化合物的热膨胀性质及本征磁致伸缩性质。研究结果表明,Tm2CrFe14.5Si1.5化合物在303～623 K范围内,具有单相的Th2Ni17型结构;Tm2CrFe14.5Si1.5化合物的居里温度约为453 K,比其母合金Tm2Fe17高约163 K;沿a轴方向上,Tm2CrFe14.5Si1.5化合物在423～448 K温度范围内出现负热膨胀现象,其热膨胀系数αa为-0.716×10-5/K;沿c轴方向上,在303～398 K温度范围内也出现负热膨胀现象,其热膨胀系数αc为-0.547×10-5/K。两者综合的结果使得在423～448 K温度范围内,Tm2CrFe14.5Si1.5化合物的体热膨胀系数αv为-0.794×10-5/K。对本征磁致伸缩的研究结果表明,Tm2CrFe14.5Si1.5化合物中存在着较强的各向异性的本征磁致伸缩。

The thermal expansion and spontaneous magnetostriction of Tm2CrFe14.5Si1.5 were investigated by X-ray diffraction. The result showed that the Tm2CrFe14.5Si1.5 had a hexagonal Th2Nil7-type struc- ture in the temperature range of 303 -623 K. The Cu- rie temperature was 453,163 K higher than the mother alloy. Along the a-axis, a negative thermal expansion was found in 423 -448 K, and the average linear ther- mal expansion coefficient cta = - 0. 716 × 10-5/K. Along the c-axis, a negative thermal expansion was also found in the temperature range of 303 -398 K, and the average linear thermal expansion coefficient ac = -2.04 × 10-5/K. The two results made the average volume thermal expansion coefficient av = - 0. 794 × 10-5/K in the temperature range of 423 -448 K. The spontaneous magnetostriction of Tm2CrFe14.5Si1.5 was also discussed. The result showed that the Tm2CrFe14.5Si1.5 compound had a strong and anisotrop- ic spontaneous magnetostriction.