MAGNETIC-PROPERTIES OF FE-BASED DILUTED MAGNETIC SEMICONDUCTORS

In recent years considerable interest was focused on diluted magnetic semiconductors (DMS), mainly Mn-based DMS. Mn++ ions in these materials possess only spin momentum (S=5/2), which is the source of the permanent magnetic moment localized on Mn ions. On the other hand, a new class of Fe-type DMS can serve as a much more general example, since Fe++ ions possess both spin and orbital momenta (S=2, L=2). Consequently the ground state of an Fe++ ion is a magnetically inactive singlet, and one is dealing only with field induced magnetic moments associated with Fe ions. This situation yields a substantially different magnetic behavior of Fe-based DMS with respect to Mn-type materials. In that respect, we review the magnetic properties of Fe-type DMS-like ZnFeSe, CdFeSe, HgCdFeSe, and HgFeSe. The influence of nonvanishing orbital momentum on specific heat, susceptibility, and magnetization is pointed out. We also show evidence of antiferromagnetic exchange interaction between Fe ions in these crystals. A possible (superexchange) mechanism of this interaction is discussed. A survey of exchange interaction parameters is presented.