Observation of Intrinsic Half-metallic Behavior of CrO$_2$ (100) Epitaxial Films by Bulk-sensitive Spin-resolved PES

TL;DR

This study uses bulk-sensitive spin-resolved photoemission spectroscopy to reveal the intrinsic half-metallic behavior and non-quasiparticle states in CrO$_2$ (100) epitaxial films, showing temperature-dependent spin polarization.

Contribution

It provides direct experimental evidence of NQP states in CrO$_2$ and compares their temperature dependence with magnetization, advancing understanding of its half-metallic properties.

Findings

Spin polarization is nearly 100% at 40 K and 40% at 300 K.

Observation of spin depolarization at the Fermi level at 100 K.

Support for NQP states from theoretical calculations.

Abstract

We have investigated the electronic states and spin polarization of half-metallic ferromagnet CrO$_2$ (100) epitaxial films by bulk-sensitive spin-resolved photoemission spectroscopy with a focus on non-quasiparticle (NQP) states derived from electron-magnon interactions. We found that the averaged values of the spin polarization are approximately 100% and 40% at 40 K and 300 K, respectively. This is consistent with the previously reported result [H. Fujiwara et al., Appl. Phys. Lett. 106, 202404 (2015).]. At 100 K, peculiar spin depolarization was observed at the Fermi level ($E_{F}$), which is supported by theoretical calculations predicting NQP states. This suggests the possible appearance of NQP states in CrO$_2$. We also compare the temperature dependence of our spin polarizations with that of the magnetization.