Room-temperature ferromagnetism in Cr-doped GaN single crystals

We report on the discovery of a room-temperature ferromagnetism in Cr-doped GaN single crystals with a $T_c\text{=280\hspace{0.17em}}\mathrm{K}.$ The addition of Cr into GaN single crystals grown by the flux method induces the lattice constant increase due to the larger Cr atomic radius. In x-ray photoelectron spectroscopy measurement, Cr ${\text{2p}}_{\text{3/2}}$ core-level exhibited spectra near 575.7 eV. This binding energy is similar to the reported value of CrN. The coercive field by magnetization–magnetic field $\mathrm{(M–H)}$ hysteresis curve at 250 K was 54 Oe. We verified the presence of ferromagnetic transition in the temperature dependence of the electrical resistance measurements. We discuss the ferromagnetic ordering in Cr-doped GaN bulk single crystals excluding the contribution of the substrate crystal structure.