We report x-ray magnetic linear dichroism (XMLD) measurements at the Fe $L_{2,3}$ absorption edges of thin antiferromagnetic (AFM) ${\mathrm{LaFeO}}_3$ films grown epitaxially on ${\mathrm{SrTiO}}_3$ (100) and (110) substrates and a stepped (100) substrate with a 2° 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 ${\mathrm{LaFeO}}_3.$ 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 ${\mathrm{SrTiO}}_3$ substrate, with its projection on the film surface parallel to the c axis of the orthorhombic ${\mathrm{LaFeO}}_3$ 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.

• Received 23 August 2002

DOI:https://doi.org/10.1103/PhysRevB.67.214433