Investigations on the origin of ferromagnetism in Ga1-xCrxN and Si-doped Ga1-xCrxN films: Experiments and theory

摘要

In this paper, we combined experiments and first-principles calculations to investigate the physical properties especially the magnetic properties of Ga(1-x)C(r)xN and Si-doped Ga1-xCrxN thin films grown by molecular beam epitaxy. The results of experiments indicate that Si doping improved the crystallinity by improving the substitution of Ga in Si-doped Ga1-xCrxN. And the size and/or the number of vacancy defects are reduced in the Si-doped Ga1-xCrxN thin films. All the samples show room-temperature ferromagnetism, and the measured saturation magnetizations are 15 emu/cm(3) (2.26 mu(B) per Cr atom) and 10 emu/cm(3) (1.31 mu(B) per Cr atom) respectively for Ga1-xCrxN and Si-doped Ga1-xCrxN thin films. First-principles calculations based density-functional theory show that there is a strong magnetic coupling between the Ga vacancies and the impurities of Cr and Si ions. And Si doping reduced the saturation magnetization in Si-doped Ga1-xCrxN thin films which is in agreement with the experiment results. This intrinsic defect derived magnetic interaction plays an important role on improving the ferromagnetism in Ga1-xCrxN and Si-doped Ga1-xCrxN, and the ferromagnetism of the system is the result of long-range mediation between V-Ga, Cr and Si ions. (C) 2015 Elsevier B.V. All rights reserved.