Diluted Magnetic Semiconductors in High Magnetic Fields

Magnetization studies of diluted magnetic semiconductors in high fields are reviewed. Magnetization steps due to pairs were originally used to measure the near neighbor exchange constant J$\text{}_{1}$. They are now also used to determine: (1) the smaller exchange constants J$\text{}_{2}$ and J$\text{}_{3}$, (2) the difference between J$\text{}_{1}$'s for inequivalent near neighbors in wurtzite diluted magnetic semiconductors, and (3) the Dzyaloshinski-Moriya interaction. A different type of magnetization step, due to isolated ions, is used to determine the uniaxial anisotropy of Co$\text{}^{++}$ ions in wurtzite diluted magnetic semiconductors. In Fe-based diluted magnetic semiconductors the high-field magnetization exhibits two effects: (1) strong dependence on field direction in cubic diluted magnetic semiconductors, and (2) reversal of the uniaxial magnetization-anisotropy in wurtzite diluted magnetic semiconductors. In (100) EuTe/PbTe superlattices the antiferromagnetic transition, both at zero and finite H, is depressed when the EuTe layer becomes only a few monolayers thick. The easy directions are in the (100) plane of the layer, which is explained by the dipole-dipole anisotropy.