Crystallographically oriented Fe nanocrystals formed in Fe-implanted TiO2

A comprehensive characterization of the structural and magnetic properties of Fe-implanted rutile TiO2(110) is presented. Fe and FeTiO3 (Ilmenite) nanocrystals (NCs) are identified by synchrotron-radiation X-ray diffraction. The majority of Fe NCs are crystallographically oriented with respect to the matrix following the relation Fe(001)[010]kTiO2(110)[110]. Post-annealing induced the out-diffusion of Fe and the growth of FeTiO3 at the cost of Fe NCs. Mössbauer spectroscopy and SQUID magnetometry reveal the corresponding evolution of magnetic properties, i.e. magnetization, and superparamagnetic blocking temperature. We unambiguously identify Fe NCs as the origin of the ferromagnetism. These Fe NCs possess a uniaxial in-plane magnetic anisotropy, such that the two Fe[100] axes are inequivalent.