Experimental and theoretical investigations on ferromagnetic nature of Mn-doped dilute magnetic semiconductors

X-ray absorption fine structure (XAFS) and first-principles calculations are effectively combined to establish correlations of fabrications, atomic and electronic structures as well as ferromagnetism for the Mn-doped dilute magnetic semiconductors (DMS), and to shed light on the magnetism origin for a variety of ZnO-, GaN-, and Si-based DMSs. The results of Mn:ZnO and (Mn,N):ZnO thin films reveal that either the existence of Zn vacancy or N substitution of O sites can stabilize the ferromagnetic interactions between neighboring Mn-Mn pairs, and enhance the magnetic moment per Mn. In a 2.5at.% Mn-doped GaN film, a part of substantial Mn ions is found to locate at the interstitial sites near the substitutional Mn ions, forming Mn-Mn dimers that possess unique electronic and magnetic properties. Similar phenomena have also been found in the Mn-doped Si system in which the interstitial Mn atoms intend to assemble together via an intervening substitutional Mn ion. We have proposed a pathway to understand the microscopic origin of ferromagnetism in the DMS materials from the viewpoint of experimental determination and theoretical calculations.