Valence, exchange interaction, and location of Mn in polycrystalline Mn(x)Ga(1-x)N (x<0.04)

TL;DR

This study investigates the electronic and magnetic properties of Mn-doped GaN, revealing Mn valence, magnetic anisotropy, and antiferromagnetic coupling, with implications for understanding magnetic interactions in dilute magnetic semiconductors.

Contribution

The paper provides experimental evidence on Mn valence, magnetic anisotropy, and exchange interactions in Mn(x)Ga(1-x)N, clarifying controversial issues and challenging previous assumptions about hole-induced effects.

Findings

Mn ions are in the 2+ valence state.

Mn(2+) ions exhibit significant axial anisotropy.

Nearest-neighbor Mn(2+) ions are antiferromagnetically coupled.

Abstract

We present an experimental study for polycrystalline samples of the diluted magnetic semiconductor Mn(x)Ga(1-x)N (x<0.04) in order to address some of the existing controversial issues. Different techniques were used to characterize the electronic, magnetic, and structural properties of the samples, and inelastic neutron scattering was employed to determine the magnetic excitations associated with Mn monomers and dimers. Our main conclusions are as follows: (i) The valence of the Mn ions is 2+. (ii) The Mn(2+) ions experience a substantial single-ion axial anisotropy with parameter D=0.027(3) meV. (iii) Nearest-neighbor Mn(2+) ions are coupled antiferromagnetically. The exchange parameter J= 0.140(7) meV is independent of the Mn content x, i.e., there is no evidence for hole-induced modifications of J towards a potentially high Curie temperature postulated in the literature.