Bridgman法生长的Mn_xCd_(1-x)In_2Te_4晶体相形成规律和物理性能研究

Phase Formation and Physical Properties of Mn_xCd_1-XIn_2Te4 Ingots Grown by the Bridgman Method

采用Bridgman法生长了x为0.1,0.22和0.4的四元稀磁半导体化合物MnxCd1-xIn2Te4晶体.研究了三根晶体中相的形貌、结构、成分和Mn0.1Cd0.9In2Te4晶体中各组元沿轴向和径向的成分分布.晶体生长初始端的组织为α+β+β1,随着生长的进行,形成β相的单相区.在晶锭末端,形成In2Te3类面心立方结构化合物.组分x增大后,MnxCd1-xIn2Te4晶体的吸收边向短波方向移动,禁带宽度则线性增大.磁化率测量结果表明:晶体在高温区的x-1-T曲线服从居里-外斯定律,在低温区(<50K)则表现出顺磁增强现象.

Diluted magnetic semiconductor MnxCd1-xIn2Te4(X=0.1, 0.22 and 0.4) ingots were grown by the Bridgman method. The structure and composition of different phases and the compositional distribution along the axis and radius of the MnxCd1-xIn2Te4 ingot were analyzed. alpha+beta+beta(1) structures are formed at the tip of the MnxCd1-xIn2Te4 ingots. Among them, alpha and beta phases are crystallized from the melt while beta(1) is precipitated from alpha phase when temperature is below solidus. The content of beta phase increases with the growth process, and finally, a pure beta phase-region is formed. At the end of the ingots, an In2Te3-type phase with a fcc structure is crystallized. There exist two distinct interfaces between the different neighbouring phase-regions. The-band gap of MnxCd1-xIn2Te4 shifts towards the high energy side with the increase of x. At higher temperatures(50similar to300K) the variation of magnetic susceptibility chi with T in MnxCd1-xIn2Te4 follows the Curie-Weiss (C-W) law. However, a paramagnetic behavior exists at lower temperature (<50K). The antiferromagnetic exchange of Mn2+ increases with the composition, x.