In掺杂对Cd_(0.8)Mn_(0.2)Te巨法拉第效应的影响

Effect of In Doping on the Giant Faraday Rotation of Cd_(0.8)Mn_(0.2)Te Crystal

常温下测量了Cd0.8Mn0.2Te晶片和多个掺In浓度不同的Cd0.8Mn0.2Te（以下简称Cd0.8Mn0.2Te：In）晶片的法拉第旋转谱和吸收边附近的透射光谱。结果表明，随着入射光子能量的增大，Cd0.8Mn0.2Te和Cd0.8Mn0.2Te：In的Verdet常数随之增大。掺In晶片的Verdet常数的变化与掺杂浓度有关：当光子能量在1．63～1．72eV范围内逐渐增加时，未掺In的测量值的变化范围是710～1820（°）／cm·T；当In浓度为8．96×10^16 atoms／cm^3时，Verdet常数增大到720-1960（°）／cm·T：当In浓度n分别为2．39×10^17，4．48×10^18 atoms／cm^3时，Verdet常数分别减小到660～1630，490-1090（°）／cm·T；当In浓度达到2．99×10^19 atoms／cm^3时，在1．63～1．70eV的光子能量范围内，Verdet常数减小到460～740（°）／cm·T。低掺In条件下，Verdet常数的增大是由于价带电子数增多，价带类P电子与Mn^2＋离子3d电子交换相互作用增强引起的；在高掺In量下，由于导带类s电子与Mn^2＋离子3d电子交换相互作用增强，导带能级分裂进一步减小，导致Cd0.8Mn0.2Te：In的Verdet常数减小。

Faraday rotation and near infrared transmission properties of Cd0.8Mn0.2Te wafers and those with different In doping concentration in the range from 10^16 to 10^19 atoms/cm^3 were studied at room temperature. It was showed that with the increase of the photon energy, the Verdet constants of Cd0.8Mn0.2Te and Cd0.8Mn0.2Te：In were increased. Moreover, the Verdet constant of Cd0.8Mn0.2Te depended on In doping concentration. In the un-doped Cd0.8Mn0.2Te crystal, the Verdet constant was measured to be 710-1820（°）/cm·T in the photon energy range of 1.63-1.72 eV. When 8.96× 10^16atoms/cm^3 In was doped, the Verdet constant was increased to 720-1960（°）/cm·T However, the values was decreased to 660-1630, 490-1090（°）/cm·T when In doping concentration reached 2.39×10^17and 4.48×10^18atoms/cm^3 respectively. When 2.99× 10^19atoms/cm^3 In was doped, the Verdet constant was decreased to 460-740（°）/cm·T in the photon energy range of 1.63-1.70 eV. For low In concentration, the increase of the Verdet constant was a result of the increase of valence-band electrons, leading to an enhancement of exchange interaction between p-like valance-band electrons and 3d electrons of Mn^2＋. On the contrary, for high In concentration, the effects of the exchange interaction between s-like conduction-band electrons and 3d electrons of Mn^2＋ were enhanced, leading to the further decrease of the spin-split conduction-band and the decrease of the Verdet constant.