Spin order manipulations in nanostructures of II-VI ferromagnetic semiconductors

Present spintronic research [1,2,3] involves virtually all materials families but ferromagnetic semiconductors are particularly attractive as they combine resources of both semiconductors and ferromagnets. We describe here recent studies of ferromagnetic Crand Mn-based II-VI diluted magnetic semiconductors (DMS) excluding, however, oxides that are subject of another presentation [4]. Properties of III-V DMS are summarized elsewhere [5,6,7]; detail reviews of nitride DMS have also been recently completed [8,9]. A good starting point for the description of DMS is the Vonsovskii model, which assumes that the electronic structure consists of extended sp band states and highly localized d-shells of magnetic ions [10]. As depicted in Fig. 1, the positions of the lower and upper Hubbard levels in respect to band edges are universal if the relative positions of the band edges are shifted according to band offsets known from heterostructure studies [11,12]. This diagram makes it possible to asses the ion charge state and its variations with codoping by shallow impurities. For a given charge state, the ion spin is determined by Hund’s rule.