Correlations in Magnetic-Nonmagnetic Semiconductor Superlattices - Simple Model

The magnetic interactions in superlattices formed by alternating layers of magnetic and nonmagnetic semiconductors with common anions were studied theoretically. Within a one-dimensional tight-binding model by minimising the total electronic energy we show the existence of an efficient long range mechanism of magnetic correlations between the neighbouring magnetic layers in such superlattices. The cases of magnetic ions in the barriers (e.g., EuTe/PbTe) and in the wells, with the order within the magnetic layers being either ferromagnetic or antiferromagnetic, have been considered and compared with the paramagnetic case. In the case of antiferromagnetic ordering within magnetic layers we have found that for even and odd numbers of magnetic monolayers different magnetic superlattices are energetically favourable.