Structural and paramagnetic properties of dilute Ga(1-x)Mn(x)N

Systematic investigations of the structural and magnetic properties of single crystal Ga(1-x)Mn(x)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 noninteracting 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(1-x)Mn(x)N/(Ga, Al)N: Mg heterostructures do not reproduce the high-temperature robust ferromagnetism reported recently for this system.