Fig. 2: Linear absorption spectrum, magnetic circular dichroism, and the magnetic behavior of different Fe centers in (LuFeO₃)₃/(LuFe₂O₄)₁.

a Linear absorption spectrum of the (3, 1) superlattice. The three most important Fe-related excitations are indicated. b Magnetic circular dichroism spectra of the (3, 1) superlattice at  ±25 and  ±0 T after substrate correction. c Fixed energy cut of the magnetic circular dichroism spectrum at 1.33 eV as a function of magnetic field at various temperatures. d Optical hysteresis loop obtained from the analysis of the Fe²⁺ → Fe³⁺ charge-transfer excitation in the spin-up channel compared to that in the spin-down channel. e Hysteretic behavior of the Fe²⁺ on-site d-to-d excitation in the spin-down channel. f Coercive fields extracted from the optical hysteresis loops for each type of excitation as a function of temperature. The model fit is described in the text. Bulk magnetization is included for comparison²¹.