Observation of spin-dependent dual ferromagnetism in perovskite ruthenates

TL;DR

This study uses ARPES and SARPES to reveal spin-dependent electron correlations in SrRuO₃, showing how ferromagnetism relates to electronic band structures and spin polarization, supported by theoretical calculations.

Contribution

It provides direct experimental evidence of spin-dependent band structures and clarifies the connection between ferromagnetism and electronic correlations in SrRuO₃.

Findings

Spin-lifted band structures observed via ARPES and SARPES.

Spin polarization varies with momentum near the Fermi level.

Spin-splitting gap decreases with temperature, leading to incoherent bands.

Abstract

We performed in-situ angle-resolved photoemission spectroscopy (ARPES) and spin-resolved ARPES (SARPES) experiments to investigate the relationship between electronic band structures and ferromagnetism in SrRuO$_3$ (SRO) thin films. Our high-quality ARPES and SARPES results show clear spin-lifted band structures. The spin polarization is strongly dependent on momentum around the Fermi level, whereas it becomes less dependent at high-binding energies. This experimental observation matches our dynamical mean-field theory (DMFT) results very well. As temperature increases from low to the Curie temperature, spin-splitting gap decreases and band dispersions become incoherent. Based on the ARPES study and theoretical calculation results, we found that SRO possesses spin-dependent electron correlations in which majority and minority spins are localized and itinerant, respectively. Our finding explains how ferromagnetism and electronic structure are connected, which has been under debate for decades in SRO.