Optical properties and magnetic properties of antisite-disordered Ni_(1-x)Co_xCr_2O_4 spinels

反位紊乱Ni_(1-x)Co_xCr_2O_4尖晶石的光学特性与磁学特性（英文）

From the UV?Vis absorption spectra,the FT-IR absorption spectra and the Raman spectra,it is deduced that Co ionsprimarily occupy the tetrahedral(A)site,with a minor number of them entering into the octahedral(B)site in the Ni1?xCoxCr2O4compounds.The origin of the position disorder of the Co ions is consistent with the similar ionic radii of the Co ion(0.65?)and theCr ion(0.62?)at B site.The FT-IR peak at about510cm?1shifts towards high frequency side with the increasing cobalt content.Itis resulted from the reduction of the cation?oxygen distance in the octahedron by the replacement of the Ni2+with the Co2+ions.Themagnetic measurement shows that Curie temperatures(TC)are75and90K for the compounds with x=0.2and0.8,respectively.

通过对化合物Ni_(1-x)Co_xCr_2O_4的紫外吸收光谱,红外吸收光谱和拉曼光谱分析,说明Co离子中绝大多数占据了四面体(A)位置,少部分占据了八面体(B)位置。Co离子占位紊乱是由于八面体中Co离子的半径(r=0.65?)接近于八面体中Cr离子的半径(r=0.62?)引起的。随着Co含量的增加,在510 cm^(-1)附近出现的红外吸收峰向高频方向移动,这是由于Co离子替代四面体中Ni离子使八面体中阳离子与氧之间的距离减小,导致键能增强引起的。磁性测量展示了x=0.2和0.8的居里温度(T_C)分别为75 K和90 K。