Structure and magnetic properties of an epitaxial Fe(110)/MgO(111)/GaN(0001) heterostructure

We present the structural and magnetic properties of fully epitaxial Fe(110)/MgO(111)/GaN(0001) tunnel barrier structures grown by molecular beam epitaxy. In-situ reflection high-energy electron diffraction and ex-situ X-ray diffraction measurements indicate epitaxial Fe(110) films on top of an epitaxial 2 nm MgO(111) tunnel barrier on GaN(0001). X-ray reflectivity measurements confirm a roughness of approximately 0.3 nm and 0.7 nm for the MgO/GaN and the Fe/MgO interfaces, respectively. Results of in-situ magneto-optical Kerr effect measurements indicate that 1 nm thick Fe film shows signs of in-plane ferromagnetism at room temperature. Vibrating sample magnetometer measurements determine the saturation magnetisation of the 5 nm thick film to be 1660 +/- 100 emu/cm(3) and show that this system has a predominant uniaxial anisotropy contribution despite the presence of cyclic twinned crystals. We estimate the values of effective uniaxial (K-U(eff)) and cubic (K-1(eff)) anisotropy constants to be 11700 +/- 170 erg cm(-3) and -3300 +/- 700 erg cm(-3) by fitting the angular dependence of the magnetising energy. Published by AIP Publishing.