Giant temperature-independent ultraviolet circular dichroism in Co₂MnX (X=Ga,Ge) Heusler magnetic thin films

Optical circular dichroism (CD) is a useful method for investigating the role of chirality in natural and physical processes. A large magnitude of CD must be achieved for spectroscopy and sensing, particularly in the ultraviolet (UV) energy range where molecular chirality is identifiable. However, the strong absorption of UV wavelengths in many materials precludes large UV-CD responses. In this work, we observed a giant temperature-independent magnetic circular dichroism (MCD) in the UV regime in magnetic Co₂MnGa thin films. We demonstrated the MCD in this system is controlled by the magnetization and originates from the hybridization of Co and Mn 3d states, by referring to calculations of the spin-polarized density of states. Based on these results, we propose and test two general rules for identifying other magnetic materials expected to have large MCD. Our results open a route towards finding magnetic materials with large MCD excited at different energy ranges, for CD applications with immunity to temperature variation.