Magnetic phase diagram of rare-earth orthorhombic perovskite oxides

Abstract

Spin reorientation and magnetization reversal are two important features of the rare-earth orthorhombic perovskites ($RM{\mathrm{O}}_{3}$) that have attracted a lot of attention, though their exact microscopic origin has eluded researchers. Here, using density functional theory and classical atomistic spin dynamics we build a general Heisenberg magnetic model that allows to explore the whole phase diagram of the chromite and ferrite compounds and to scrutinize the microscopic mechanism responsible for spin reorientations and magnetization reversals. We show that the occurrence of a magnetization reversal transition depends on the relative strength and sign of two interactions between rare-earth and transition-metal atoms: superexchange and Dzyaloshinskii-Moriya. We also conclude that the presence of a smooth spin reorientation transition between the so-called ${\mathrm{\ensuremath{\Gamma}}}_{4}$ and the ${\mathrm{\ensuremath{\Gamma}}}_{2}$ phases through a coexisting region, and the temperature range in which it occurs, depends on subtle balance of metal-metal (superexchange and Dzyaloshinskii-Moriya) and metal--rare-earth (Dzyaloshinsky-Moriya) couplings. In particular, we show that the intermediate coexistence region occurs because the spin sublattices rotate at different rates.