Bridgman法生长的MnxCd1-xIn2Te4晶体相形成规律和物理性能研究

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Mn_xCd_1-xIn₂Te₄晶体.研究了三根晶体中相的形貌、结构、成分和Mn_0.1Cd_0.9In₂Te₄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,Mn_xCd_1-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.

Phase Formation and Physical Properties of MnxCd1-xIn2Te4 Ingots Grown by the Bridgman Method

Diluted magnetic semiconductor Mn_xCd_1-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 Mn_xCd_1-xIn₂Te₄ ingot were analyzed. α+β+β₁ structures are formed at the tip of the Mn_xCd_1-xIn₂Te₄ ingots. Among them, α and β phases are crystallized from the melt while β1 is precipitated from α phase when temperature is below solidus. The content of β phase increases with the growth process, and finally, a pure β 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 Mn_xCd_1-xIn₂Te₄ shifts towards the high energy side with the increase of x. At higher temperatures(50～300K) the variation of magnetic susceptibility χ with T in Mn_xCd_1-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.