Different spin axis orientation and large antiferromagnetic domains in Fe-doped NiO/Ru(0001) epitaxial films

We present a spatially resolved X-ray magnetic dichroism study of high-quality, in situ grown nickel oxide films. NiO thin films were deposited on a Ru(0001) substrate by high temperature oxygen-assisted molecular beam epitaxy. We found that by adding a small amount of Fe, the growth mode can be modified in order to promote the formation of micron-sized, triangular islands. The morphology, shape, crystal structure and composition are determined by low-energy electron microscopy and diffraction, and synchrotron based X-ray absorption spectromicroscopy. The element specific XMLD measurements reveal strong antiferromagnetic contrast at room temperature and domains with up to micron sizes, reflecting the high structural quality of the islands. By means of vectorial magnetometry, the spin axis orientation was determined with nanometer spatial resolution, and found to depend on the relative orientation of the film and substrate lattices.