Magnetic anisotropy of Zn-Cr alloys at very low temperatures

The temperature dependent magnetization of Zn-Cr single crystals was measured from 2K down to 10 mK using a SQUID magnetometer. A large anisotropy is observed for the magnetization along the parallel and perpendicular axes of the crystal. For low concentrations impurity-impurity reactions do not dominate the behavior of the system, although they are still present even in the 10 ppm impurity concentration range. The anisotropy in the magnetization, Mn-Mj, is negative which is in contrast with the Mn in Zn system where the anisotropy is positive. The results are analyzed in terms of crystal field splittings and exchange. These results have important implications for the Kondo effect in this system.