The structural and magnetic properties of hematite (α-Fe₂O₃) thin films with thicknesses ranging from 5 to 250 nm, grown by magnetron sputtering on c-Al₂O₃ substrates, have been investigated. The evolution of the lattice parameters with increasing film thickness has been analyzed. Experimental results show that the in-plane lattice parameters and the corresponding mechanical strain, arising from the lattice mismatch between the film and the substrate, gradually decrease with increasing film thickness. It is demonstrated that the Morin transition disappears as the thickness decreases from 250 to 162 nm and is not observed in thinner films. The magnetization continuously decreases with decreasing film thickness. Ab initio calculations of the structural parameters were performed, highlighting the importance of taking structural defects into account to describe adequately the observed trends.
A. P. Nosov (Wed,) studied this question.