We consider orthoferrite and orthochromite perovskites with the formula $\mathit{RM}{\mathrm{O}}_3$, where $R$ is a lanthanide and $M$ is Fe or Cr. We identify an atomistic interaction that couples the magnetic moments of the $R$ and $M$ cations with the oxygen octahedral rotations characterizing these crystals. We show that this interaction results in an effective magnetic field acting on the $R$ atoms, which in turn explains several intriguing features of these compounds, such as the existence (or absence) of a net magnetization associated with the $R$ sublattice and its crystallographic direction. Further, considered together with the couplings described by L. Bellaiche et al. [J. Phys.: Condens. Matter 24, 312201 (2012)], this interaction explains why some $\mathit{RM}{\mathrm{O}}_3$ compounds display a compensation temperature at which the magnetization cancels and changes sign, while others do not.

• Received 3 September 2015
• Revised 3 November 2015

DOI:https://doi.org/10.1103/PhysRevB.93.014417