Magnetic properties of Fe2O3(0001) thin layers studied by soft x-ray linear dichroism -: art. no. 224407

X-ray magnetic linear dichroism (XMLD) at the Fe L-2 absorption edge has been used for investigating the magnetic properties of thin epitaxial alpha -Fe2O3 layers (20 and 80 Angstrom thick). When cooling below 263 K, bulk hematite undergoes a 90 degrees rotation of the antiferromagnetic axes from perpendicular to parallel to the c axis (Morin transition). The L-2-XMLD results indicate that the 80-2k-thick layer does not undergo such a transition at least down to 125 K. This absence is attributed to important magnetoelastic interactions due to the 0.3% expansion of the lattice parameter in the c plane. In the case of a 20-Angstrom -thick layer, we do not detect any L-2-XMLD signal, regardless of the temperature. The absence of antiferromagnetic ordering might be caused by the combined effect of several factors: finite size effects, changes in the local crystal field of the Fe3+ ion, and magnetoelastic interactions, coming from the 0.8% expansion of the lattice parameter in the c-plane.