We report on the metamagnetic transition observed in oxides Ba₂LnFeO₅ (Ln = Tb, Dy, Ho, Er, Yb), which contain two magnetic sublattices: Fe^3+ and Ln^3+. The magnetic ordering in these materials results from a competition between several types of interaction (Fe-Fe, Fe-Ln, and Ln-Ln), combined in most cases with a strong easy-axis anisotropy of the Ln^3+ magnetic moments induced by the crystal electric field (CEF). A specific mechanism is proposed to account for the peculiar metamagnetism in this class of materials, and its variation along the Ln series. This study is based on a set of results including magnetization, x-ray magnetic circular dichroism, neutron powder diffraction, and calculations of the CEF.
Hardy et al. (Fri,) studied this question.