Unusual ferrimagnetic ground state in rhenium ferrite

Through comprehensive density functional calculations, we predict the stability of a rhenium-based ferrite, ReFe₂O₄, in a distorted spinel-based structure. In ReFe₂O₄, all Re and half of the Fe ions occupy the octahedral sites while the remaining Fe ions occupy the tetrahedral sites. All Re ions are predicted to be at a + 4 oxidation state with a low spin configuration (S = 3/2), while all Fe ions are predicted to be at a + 2 oxidation state with a high-spin state configuration (S = 2). Magnetically, ReFe₂O₄ adopts an unconventional ferrimagnetic state in which the magnetic moment of Re opposes the magnetic moments of both tetrahedral and octahedral Fe ions. The spin–orbit coupling is found to cause a slight spin canting of ~ 1.5°. The predicted magnetic ground state is unlike the magnetic alignment usually observed in ferrites, where the tetrahedral cations oppose the spin of the octahedral cations. Given that the density of states analysis predicts a half-metallic character driven by the presence of Re t_2g states at the Fermi level, this compound shows promise towards potential spintronics applications.