Sm-Fe和Sm-Co非晶态合金薄膜的高场热磁效应

本文研究了Sm_xT_1-x(T=Fe,Co)非晶态薄膜的磁化强度σ与温度T的关系。发现在磁场H=7T下,对Sm_xCo_1-x样品(x=0.46,0.48,0.54,0.65)的升温过程测得的σ(T)曲线上有极大值,它对应的温度都在25—28K范围内,与成分关系不大。非晶态Sm_xFe_1-x(x=0.46,0.73)的结果与之不同,极大值对应的温度与成分有关。对上述样品,还发现在T≈6K附近σ(T)有极小值(和陡变),在近室温端,出现σ(T)下降缓慢的“拖尾巴”现象。我们认为,Sm-Co非晶态薄膜表现的高场热磁效应可能起源于Sm原子磁矩对磁化的贡献不可忽略,作用在Sm原子上的局域无规各向异性很强;这种各向异性在20—30K变化较大。而Sm-Fe薄膜的高场热磁效应可能起源于Fe原子磁矩的分散。σ(T)在6K附近的极小值(和陡变)及其在室温端变化缓慢的原因,可能是合金成分的涨落所致。 关键词：

THERMOMAGNETIC EFFECT OF THE Sm-T(T = Fe, Co ) AMORPHOUS THIN FILMS IN HIGH FIELDS

The temperature dependence of magnetization at H=0.1-7T for amorphous Sm_xT_1-x (T = Fe, Co) thin films was investigated in the range of 1.5 to 300 K. It was found that there was a maximum magnetization in the σ(T) curves, measured in the temperature rising process, for the Sm_xCo_1-x thin films (x=0.46, 0.48, 0.54, 0.65). For the Sm-Co alloys, the temperatures, corresponding to σ_max, are about 25-28 K and are independent of the composition. But the Sm-Fe amorphous alloys are different from the Sm-Co alloys, in the former the temperature corresponding to σ_max depends on both the field and the composition of the alloys. In addition, it was found that there was σ_min (or a repaid variation) at T≈6 K, and σ(T) decreased very slowly near room temperature. It was suggested that the thermomagnetic effect for the Sm-Co thin films at high field may be caused by the contribution of Sm moment to the magnetization, though the magnetic moment of Sm atoms is very small (≈0.1μB), and the random local anisotropy is strong at low temperatures and changes signicantly between 20-30 K. But the thermomagnetic effect of the Sm-Fe amorphous alloys may be caused by the dispersion of the Fe moments. The σ_min at T≈6 K and the slow decrease of σ(T) near room temperature may be caused by fluctuation of composition in these alloys.