Thickness dependence and dimensionality effects on charge and magnetic orderings in La_(1/3_Sr_(2/3)FeO_3 thin films

摘要

We investigate the thickness effects on charge and magnetic orderings in Fe perovskite oxide La_(1/3)Sr_(2/3)FeO_3/SrTiO_3 thin films by hard x-ray and resonant soft x-ray scattering (RSXS) with changing thin-film thickness systematically. We found that the correlation lengths of the magnetic ordering along the in-plane and out-of-plane directions are comparable and proportional to the thickness, and show stronger thickness dependence than those of charge ordering. The magnetic ordered states disappear when the correlation length of magnetic ordering decreases to that of charge ordering through the intrinsic thickness effects. Surface-sensitive grazing-incident RSXS revealed that the orderings exist even in the surface region, which indicates that the observed orderings are not affected by surface effects like oxygen vacancies. Critical thickness is in 5-15 nm, which corresponds to 4-11 antiferromagnetic ordering period. This critical value seems to be common to other ferromagnetic oxide thin films.