thin films

Theoretical calculations indicate that NiCo₂O₄ is a half-metal with fully spin polarized carriers [1], although realization of half metallicity is in fact very doubtful [2] especially at finite temperatures. It remains important, nonetheless, to ascertain whether NiCo₂O₄ is a high polarization material and whether the spin polarization has a projection in the plane of the thin film. We observed in-plane net spin polarized unoccupied states of NiCo₂O₄ near Fermi level using spin-polarized inverse photoemission spectroscopy (SPIPES) which is an extremely surface sensitive technique. Although NiCo₂O₄ is thought to possess a perpendicular magnetic anisotropy, the presence of in-plane spin-resolved unoccupied states could indicate the influence of the surface on magnetic ordering.

[1] P. F. Ndione et al., Adv. Funct. Mater. 24, 610 (2014).

[2] P.A. Dowben and R. Skomski, J. Appl. Phys. 95, 7453 (2004).