Structure and magnetic properties of Cr-doped GaN

Structure and magnetic properties of the Ga1-x Crx N (x=0.013, 0.063, and 0.101) have been investigated. The lattice constant of the c axis is systematically decreased with increasing Cr content. The local structure around a Cr atom maintains tetrahedral symmetry up to x=0.101 the same as the local symmetry of GaN by x-ray absorption fine structure analysis. The analysis on x=0.013 indicated that the second nearest neighbor around the absorbing Cr atoms consists of only 12 Ga atoms. However, for x=0.063, the second nearest neighbor around the absorber consists of Ga and Cr atoms with an unexpectedly high ratio of about Ga:Cr=2:1. In Cr K -edge x-ray absorption near edge structure, we observed the oxidation state of Cr ion increases with increasing Cr content. Ferromagnetic behavior was observed in all Ga1-x Crx N films. However, the paramagnetic component also coexists with the ferromagnetic component. Total effective magnetic moment per Cr atom decreased from 3.17 μB atom for x=0.013 to 1.05 and 0.79 μB atom for x=0.063 and 0.101, respectively. The decreased magnetic moments of the x=0.063 and 0.101 is possibly caused by antiferromagnetic interaction of Cr-N-Cr networks in the high Cr content samples.