Optimization of ruthenium as a buffer layer for non-collinear antiferromagnetic Mn3X films

Two thin film deposition routes were studied for the growth of high quality single crystalline Ru (0001) epitaxial films on c-Al2O3 substrates using radio frequency-magnetron sputtering. Such films are very important as buffer layers for the deposition of epitaxial non-collinear antiferromagnetic Mn3X films. The first route involved depositing Ru at 700 degrees C, leading to a smooth 30nm thick film. Although, high resolution x-ray diffraction revealed twinned Ru film orientations, in situ post-annealing eliminated one orientation, leaving the film orientation aligned with the substrate, with no in-plane lattice rotation and a large lattice mismatch (13.6%). The second route involved the deposition of Ru at room temperature followed by in situ post-annealing at 700 degrees C. Transmission electron microscopy confirmed a very high quality of these films, free of crystal twinning, and a 30 degrees in-plane lattice rotation relative to the substrate, resulting in a small in-plane lattice mismatch of -1.6%. X-ray reflectivity demonstrated smooth surfaces for films down to 7nm thickness. 30nm thick high quality single-crystalline Mn3Ga and Mn3Sn films were grown on top of the Ru buffer deposited using the second route as a first step to realize Mn3X films for antiferromagnetic spintronics applications. Published under license by AIP Publishing.