Comparative study of magnetic and electronic properties of room-temperature polar magnets ScFeO3 and InFeO3

We performed calculations based on collinear and non-collinear spin density functional theory to investigate magnetic and electronic properties of new room-temperature polar magnetic compounds AFeO₃ (A = Sc, In). Exchange and correlation effects were simulated by standard local spin density approximation and the generalized gradient approximation. We determined that the canted G-type antiferromagnetic (G-AFM) structure of the Fe spin moments is the most stable magnetic structure for both compounds, in accordance with experimental facts. The calculated Fe spin magnetic moments and resulting weak ferromagnetic components perpendicular to the c-axis also agree well with the experiment. The magnitude of the Fe spin moment does not depend on the fact if the G-AFM structure is collinear or canted. The energy difference between these two structures is found to be much larger for InFeO₃, so as the exchange interaction constant J_nn between nearest-neighbor magnetic Fe ions. The ScFeO₃ and InFeO₃ electronic structures, which reproduce well their magnetic properties are presented and discussed. By comparing them with the band structures of some typical multiferroics, we conclude that different electronic mechanisms should be responsible for their ferroelectric distortion. In ScFeO₃, the cause of this distortion should be attributed to the hybridization between almost empty Sc 3d and occupied O 2p states along the hexagonal c-axis. For InFeO₃, however, the stereochemical activity of the In 5s localized electrons should be the principal driving force for ferroelectric distortion.