Zn1-xMnxSe的低温磁化率和自旋玻璃现象

用超导量子干涉器(SQUID)磁强计对稀释磁性半导体Zn_1-xMn_xSe(0.1≤x≤0.50)的低温低场直流磁化率作了测量,测量温度从4.2K到30K,测量磁场为15Oe。当x≥0.30时,从磁化率-温度曲线的浑圆峰值,观察到了自旋玻璃的转变。自旋玻璃的转变温度T_f,对x=0.30,0.40,0.50,分别为10.5K,16K,19.5K。给出了顺磁相和自旋玻璃相的相图。比较了Zn_1-xMn_xSe和Cd_1-xMn_xSe的自旋玻璃转变温度,发现对同样的Mn离子浓度,Zn_1-xMn_xSe的T_f高于Cd_1-xMn_xSe的T_f,用交换作用的理论作了讨论。关键词：

MAGNETIC SUSCEPTIBILITY AND THE SPIN-GLASS TRANSITION OF Zn1-x Mnx Se AT LOW TEMPERATURES

Low-field magnetic susceptibility of the diluted magnetic semiconductors Zn_1-xMn_xSe was measured between 4.2 and 30 K for the Mn concentration range 0.1≤x≤0.50 using SQUID magnetometer. When x≥0.30, the system shows a spin-glass transition in the above temperature range, as evidenced by a somewhat rounded cusp in the susceptibility. The transition temperature of spin-glass is as follow: x=0.30, T_f=10.5 K; x=0.40, T_f=16.0 K; x=0.50, T_f=19.5 K. The phase diagrams for the boundary of the paramagnetic and the spin-glass phases are obtained for this system. The difference of spin-glass transition temperature between Zn_1-xMn_x Se and Cd_1-xMn_xSe is discussed. It is found that for any given Mn concentration x the spin-glass transition temperature T_f of Zn_1-xMn_xSe is higher than that of Cd_1-xMn_xSe.