Intrinsic spin polarized electronic structure of CrO2 epitaxial film revealed by bulk-sensitive spin-resolved photoemission spectroscopy

TL;DR

This study uses bulk-sensitive spin-resolved photoemission spectroscopy to investigate the intrinsic electronic and spin structures of CrO2 epitaxial films, confirming its half-metallicity at low temperature and analyzing temperature-dependent spin polarization.

Contribution

It provides direct spectroscopic evidence of CrO2's half-metallicity and temperature-dependent spin polarization, advancing understanding of its electronic structure.

Findings

CrO2 exhibits a spin gap of 0.5 eV at low temperature

Spin polarization decreases at room temperature

Results support CrO2's half-metallic nature at low temperature

Abstract

We have performed bulk-sensitive spin-resolved photoemission spectroscopy in order to clarify the intrinsic spin-resolved electronic states of half-metallic ferromagnet CrO2. We used CrO2 epitaxial films on TiO2(100), which shows a peak at 1 eV with a clear Fermi edge, consistent with the bulk-sensitive PES spectrum for CrO2. In spin-resolved spectra at 40 K, while the Fermi edge was observed in the spin up (majority spin) state, no states at the Fermi level (EF) with an energy gap of 0.5 eV below EF was observed in the spin down (minority spin) state. At 300 K, the gap in the spin down state closes. These results are consistent with resistivity measurements and magnetic hysteresis curves of the fabricated CrO2 film, constituting spectroscopic evidence for the half-metallicity of CrO2 at low temperature and reducing the spin polarization at room temperature. We also discuss the electron correlation effects of Cr 3d.