Ruiwen Xie, Hamza Zerdoumi, Hongbin Zhang
Hematite α − Fe 2 O 3 is a g -wave altermagnetic material which has an easy-axis phase and easy-plane weak ferromagnetic phase below and above the Morin transition temperature, respectively. The presence of these phases renders it a good candidate to study the characteristic spin splitting in altermagnets under the impacts of the relativistic effect and finite temperature. In this regard, we calculate the band structure of α − Fe 2 O 3 based on density functional theory (DFT) which also considers the Hubbard U correction and spin-orbit coupling (SOC) effects. Additionally, charge self-consistent DFT plus dynamical mean-field theory (DMFT) calculations are performed at finite temperatures. We find that the altermagnetic spin splitting in α − Fe 2 O 3 is preserved by taking either SOC or the temperature effect into account. Furthermore, we present a numerical simulation of the x-ray magnetic circular dichroism (XMCD) of the L 2 , 3 edge of Fe using a combination of DFT and multiplet ligand-field theory. In terms of the different Néel vectors present in α − Fe 2 O 3 , we calculate the x-ray absorption spectroscopy of the L 2 , 3 edge of Fe in the form of a conductivity tensor and analyze the XMCD response from the perspective of symmetry. A characteristic XMCD line shape is expected when the Néel vector is along the [010] direction (magnetic point group 2 ′ / m ′ ) and the light propagation vector is perpendicular to the Néel vector, which can be further distinguished from the XMCD response originating from weak ferromagnetism with the light propagation vector parallel to the Néel vector.