Band structure tuning of Hensler compounds: Spin- and momentum-resolved electronic structure analysis of compounds with different band filling

Half-metallic ferromagnetic Heusler compounds represent an important class of materials for spintronic applications. We experimentally observe the dispersion of electronic bands with spin resolution in three representative Heusler compounds (Co2MnGa, Co2MnSi, and Co2Fe0.4Mn0.6Si). Bulk-sensitive measurements at very low photon energy are complemented by spin-integrated hard x-ray angular resolved photoemission spectroscopy. The dispersion of majority and minority electrons allows us to link exchange splitting and band filling to the number of valence electrons N-v. Photoexcitation at hv = 6.05 eV gives access to the spin-polarization texture P(E-B, k(x), k(y)) of the bulk bands covering a (k(x), k(y)) range of 60% of the Brillouin zone. We find that Co2MnSi and Co2Fe0.4Mn0.6Si exhibit minority band gaps of 0.5 and 0.35 eV, i.e., decreasing band gap with increasing Nv in contrast to the rigid-band expectation. For Co2MnGa, the minority valence state maximum lies at approx. 0.2 eV above E-F.

Automated summary

In this study, experimental observations were made on the dispersion of electronic bands with spin resolution in three representative Heusler compounds. The link between exchange splitting, band filling, and the number of valence electrons Nv was established. Furthermore, it was found that minority band gaps in Co2MnSi and Co2Fe0.4Mn0.6Si decrease with increasing Nv, contrary to rigid-band expectations.