Single-domain perpendicular magnetization induced by the coherent O <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>2</mml:mn><mml:mi>p</mml:mi></mml:mrow></mml:math>-Ru <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>4</mml:mn><mml:mi>d</mml:mi></mml:mrow></mml:math> hybridized state in an ultra-high-quality <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>SrRu</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math> film
Yuki K. Wakabayashi, Masaki Kobayashi, Yukiharu Takeda, Kosuke Takiguchi, Hiroshi Irie, Shin‐ichi Fujimori, Takahito Takeda, Ryo Okano, Yoshiharu Krockenberger, Yoshitaka Taniyasu, Hideki Yamamoto
Abstract
We investigated the Ru $4d$ and O $2p$ electronic structure and magnetic properties of an ultrahigh-quality $\mathrm{SrRu}{\mathrm{O}}_{3}$ film on $\mathrm{SrTi}{\mathrm{O}}_{3}$ grown by machine-learning assisted molecular-beam epitaxy. The high itinerancy and long quantum lifetimes of the quasiparticles in the Ru $4d$ ${t}_{2g}$-O $2p$ hybridized valence band are confirmed by observing the prominent well-screened peak in the Ru $3d$ core-level photoemission spectrum, the coherent peak near the Fermi energy in the valence-band spectrum, and quantum oscillations in the resistivity. The element-specific magnetic properties and the hybridization between the Ru $4d$ and O $2p$ orbitals were characterized by Ru ${M}_{2,3}$-edge and O $K$-edge soft x-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements. The ultrahigh-quality $\mathrm{SrRu}{\mathrm{O}}_{3}$ film with the residual resistivity ratio of 86 shows the large orbital magnetic moment of oxygen ions induced by the strong orbital hybridization of the O $2p$ states with the spin-polarized Ru $4d$ ${t}_{2g}$ states. The film also shows single-domain perpendicular magnetization with an almost ideal remanent magnetization ratio of 0.97. These results provide detailed insights into the relevance between orbital hybridization and the perpendicular magnetic anisotropy in $\mathrm{SrRu}{\mathrm{O}}_{3}/\mathrm{SrTi}{\mathrm{O}}_{3}$ systems.