VANVLECK PARAMAGNETISM OF CHROMIUM-DOPED AND IRON-DOPED-II-VI SEMICONDUCTORS

We present a study of the Van Vleck paramagnets A1-xCrxB and A1-xFexB, where AB is a II-VI semiconductor having the zinc-blende or the wurtzite structure. In cubic zinc-blende hosts the nonlinear magnetization M depends on the orientation of the external magnetic field B with respect to the cubic axes of the crystal. We show that, while for iron M is largest when B is along a cubic axis and a minimum for B parallel-to [111], for chromium the anisotropy is reversed and the largest value of M occurs for B parallel-to [111]. Expansions of the angular variation of the magnetization in terms of combinations of spherical harmonics invariant under the operations of the symmetry group (T(d) or C3v) of the site of the impurity are used to analyze the anisotropy. The magnetic-field dependence of the coefficients in the expansion is investigated. The magnetic susceptibility of Cr2+ in wurtzite-structure hosts is expected to be particularly large.