Reconstruction control of magnetic properties during epitaxial growth of ferromagnetic Mn3-δGa on wurtzite GaN(0001)

Binary ferromagnetic Mn3-delta Ga (1.2 < 3-delta <= 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 (L1(0)) ordering with (111) orientation. The in-plane epitaxial relationship to GaN is nearly ideal with [1 (1) over bar0](MnGa)parallel to[1 (1) over bar 00](GaN) and [11 (2) over bar](MnGa)parallel to[11 (2) over bar0](GaN). We observe magnetic anisotropy along both the in-plane and out-of-plane directions. The magnetic moments are found to depend on the Mn/(Mn+Ga) flux ratio and can be controlled by observation of the surface reconstruction during growth, which varies from 1x1 to 2x2 with increasing Mn stoichiometry.