First Principles Search for Fully-Compensated Ferrimagnetic Spin Filter Materials in the Equiatomic Quaternary Heusler Family

Fully-compensated ferrimagnets (FCFs) are ideal candidates for spin filter applications due to their intrinsic asymmetric band gap between the opposite spin channels. In FCFs, magnetic moments of various atoms cancel to produce a net zero magnetic moment. The strong spin polarization is generated purely by intrinsic exchange splittings and covalent bonding between the atomic species. The FCFs are robust against external coercive fields, making this class of materials suitable for use in nanoscale devices without the need to correct for the deleterious effects of stray coercive fields. Using state-of-the-art first-principles calculations we systematically examine the equiatomic quaternary Heusler family of CrMNAl (M= Ti, Zr, Hf and N = V, Nb, Ta). We identify several new FCFs with large exchange splitting of ~200 meV and small band gaps of ~100 meV beyond CrVTiAl, which has already been shown to be a promising spin-filter candidate material. Robustness against combinatorial mixing and hydrostatic stress is presented.