Effects of thermal annealing in oxygen on the antiferromagnetic order and domain structure of epitaxial LaFeO3 thin films

The antiferromagnetic order and domain structure of LaFeO3 thin films, epitaxially deposited on LaAlO3(001) substrates, were investigated by X-ray magnetic linear dichroism (XMLD) spectroscopy and spectromicroscopy, using the soft X-ray photoelectron emission microscopy (PEEM) beamline at the Advanced Light Source. In particular, we have examined the effects of thermal annealing in oxygen on the antiferromagnetic domains and spin orientation in the near surface region of such films. The recorded PEEM micrographs show AFM domains for all samples, though the domains are on average larger for the thermally annealed films. XMLD spectra recorded for different angles between the electromagnetic field vector and the film surface normal suggest a characteristic difference in the spin orientation between the as-grown (epitaxially strained) and the thermally annealed (strain relaxed) samples. While temperature-dependent measurements reveal little difference in Néel temperature between an as-grown and a fully relaxed film (TN=645 K and 610 K, respectively), both are reduced compared to that of bulk LaFeO3 (TN=740 K).