Binary ferromagnetic ${\mathrm{Mn}}_{3-\delta }\mathrm{Ga}$ ($1.2<3-\delta \le 1.5$) crystalline thin films have been epitaxially grown on wurtzite GaN(0001) surfaces using rf $N$-plasma molecular beam epitaxy. The film structure is face-centered tetragonal with CuAu type-I ($L{1}_0$) ordering with (111) orientation. The in-plane epitaxial relationship to GaN is nearly ideal with $[1\overline{1}0{]}_{\mathrm{MnGa}}\parallel [1\overline{1}00{]}_{\mathrm{GaN}}$ and $[11\overline{2}{]}_{\mathrm{MnGa}}\parallel [11\overline{2}0{]}_{\mathrm{GaN}}$. We observe magnetic anisotropy along both the in-plane and out-of-plane directions. The magnetic moments are found to depend on the $\mathrm{Mn}/(\mathrm{Mn}+\mathrm{Ga})$ flux ratio and can be controlled by observation of the surface reconstruction during growth, which varies from $1\times 1$ to $2\times 2$ with increasing Mn stoichiometry.

• Received 16 July 2006

DOI:https://doi.org/10.1103/PhysRevLett.97.146101