Karolina Z. Milowska, Malgorzata Wierzbowska
The most investigated dilute magnetic semiconductor (Ga,Mn)As is believed to be ferromagnetic due to the p-d Zener model, with the interactions mediated by extended holes in the valence bands, since the work by T. Dietl et al. [{Science} {\bf 287}, 1019 (2000)]. Recent experimental work by M. Dobrowolska et al. [Nature Mater. {\bf 11}, 444 (2012)] presents a diverse view with the holes localized within the Mn-3d derived impurity states. In this work, we investigate this system applying the density functional theory (DFT) with the pseudopotential self-interaction correction (pSIC) and maximally localized Wannier functions (MLWFs). Our results clearly show the sp3 character of a hole introduced by the substitution of Ga with Mn. Contribution of the Mn-3d states to that hole amounts to 3-12% depending on the method and doping level between 1% and 3%. Very extended nature of this hole, ranging beyond the second shell of the As-neighbors along the 110-axis, confirms by means of the ab-initio methods well established mechanism of the ferromagnetic order in this system. Under low doping of 1%, the Fermi level is still pinned to the valence band, and the impurity states within the gap are spin unpolarized and of the s-type.
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http://arxiv.org/abs/1302.5282
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