Cd0.8Mn0.2Te晶体的磁化强度和法拉第效应研究

摘要

The Cd0.8 Mn0.2 Te single-crystal ingot was grown by the vertical Bridgman method. The magnetization (M) measurements of Cd0.8 Mn0. 2 Te sample was performed at 2K under external magnetic field (H) from -1592-1592kA/m,and at 796Aim from 2-200K with magnetic field cooling and without magnetic field cooling respectively,using the superconducting quantum interference device (SQUID) magnetometer. Faraday rotation as a function of photon energy for Cd0. 8Mn0.2 Te crystal was measured at 300K under magnetic field less than 0.2 T. The M-H analysis indicates that there is an antiferromagnetic interaction between Mn2+ ions in the crystal. The results of susceptibility vs temperature fit Curie-Weiss laws at temperatures above 40K and a deviation from the Curie-Weiss law at temperatures from 2-40K, which indicate Cd0.8 Mn0. 2 Te crystal possess paramagnetic properties in the temperature range from 2-200 K and the paramagnetism enhances with the temperature decrease below 40K. The results of Faraday rotation show that Cd0.8 Mn0.2 Te has a Verdet constant up to 2 × 103deg/(cm · T) and a single-oscillator model fits the data very well with the exciton energy Eo = 1.83leV, which proves that the sp-d exchange interaction is the main reason that introduces Faraday rotation to Cd0. 8 Mn0. 2 Te.%采用垂直Bridgroan法制备出了x=0.2的Cd1-xMnxTe晶体(Cd0.8Mn0.2 Te).利用MPMS-7(magnetic property measurement system)型超导量子磁强计测量了Cd0.8Mn0.2Te晶体的磁化强度(M)与磁场强度(H)和温度(T)的关系,磁场强度范围为-1592～1592kA/m,温度范围为2～200K.Cd0.8Mn0.2Te晶体的法拉第效应测试在300K温度下进行,磁场强度<0.2T.2K温度下的M-H曲线表明,晶体的Mn2+离子之间存在反铁磁相互作用.796A/m恒磁场下的磁化率γ与温度T的关系研究表明,晶体在2～200K之间是顺磁态,当T>40K时,y与T满足居里-外斯定律;T<40K,γ与T的关系偏离居里-外斯定律,表现出顺磁增强现象.法拉第效应研究表明,晶体的Verdet常数的绝对值达到2×103deg/cm·T,采用单振子模型能够很好地拟合实验数据,得出晶体的激子能量Eo=1.831eV,说明sp-d交换相互作用引起的激子跃迁对晶体的巨法拉第效应起到主要作用.