Determination of the antiferromagnetic spin axis in epitaxial LaFeO3 films by x-ray magnetic linear dichroism spectroscopy -: art. no. 214433

We report x-ray magnetic linear dichroism (XMLD) measurements at the Fe L-2,L-3 absorption edges of thin antiferromagnetic (AFM) LaFeO3 films grown epitaxially on SrTiO3 (100) and (110) substrates and a stepped (100) substrate with a 2degrees miscut. The spin structure in the near-surface region of the thin films, and in particular the orientation of the AFM axis, has been derived from the observed polarization dependence. We show that in all cases, the orientation of the AFM axis differs from that of bulk LaFeO3. In particular, we find that the AFM axis is rotated away from its bulk orientation and lies parallel to the (111) plane of the underlying cubic SrTiO3 substrate, with its projection on the film surface parallel to the c axis of the orthorhombic LaFeO3 crystal lattice. Our results are of importance in light of existing models for the exchange coupling and bias of antiferromagnetic/ferromagnetic multilayers. They indicate the inadequacy of models that assume a bulk like spin structure near surfaces and interfaces.