Carrier-induced enhancement and suppression of ferromagnetism in Zn1-xCrxTe and Ga1-xCrxAs: origin of the spinodal decomposition

Abstract

Ferromagnetism in Zn1- xCrxTe shows some interesting but puzzling dependence on p-type (nitrogen) and n-type (iodine) dopings that seems to contradict the current understanding of carrier-induced ferromagnetism based on the d–d double exchange mechanism. Using first-principles calculations combined with a phenomenological band coupling model to describe the magnetic interactions, we show that the formation of Cr-rich regions (spinodal decomposition) is driven mainly by the energy gain due to the magnetic interaction between Cr atoms. Thus, the previously proposed Coulomb repulsion between the magnetic Cr ions does not play a major role in the formation of Cr-rich aggregates. Similar results are predicted for Ga1-xCrxAs.