Structural and paramagnetic properties of dilute Ga1-xMnxN

TL;DR

This study investigates the structural and magnetic properties of (Ga,Mn)N films, finding Mn substitutional sites and paramagnetic behavior without phase separation or high-temperature ferromagnetism.

Contribution

It provides detailed structural and magnetic characterization of (Ga,Mn)N, demonstrating the absence of phase separation and ferromagnetism, and clarifies the charge state and magnetic behavior of Mn ions.

Findings

Mn occupies Ga sites up to 1% concentration.

Magnetic behavior is paramagnetic, described by non-interacting Mn$^{3+}$ ions.

No evidence of high-temperature ferromagnetism in studied heterostructures.

Abstract

Systematic investigations of the structural and magnetic properties of single crystal (Ga,Mn)N films grown by metal organic vapor phase epitaxy are presented. High resolution transmission electron microscopy, synchrotron x-ray diffraction, and extended x-ray absorption fine structure studies do not reveal any crystallographic phase separation and indicate that Mn occupies Ga-substitutional sites in the Mn concentration range up to 1%. The magnetic properties as a function of temperature, magnetic field and its orientation with respect to the c-axis of the wurtzite structure can be quantitatively described by the paramagnetic theory of an ensemble of non-interacting Mn$^{3+}$ ions in the relevant crystal field, a conclusion consistent with the x-ray absorption near edge structure analysis. A negligible contribution of Mn in the 2+ charge state points to a low concentration of residual donors in the studied films. Studies on modulation doped p-type (Ga,Mn)N/(Ga,Al)N:Mg heterostructures do not reproduce the high temperature robust ferromagnetism reported recently for this system.