Presentation Information
[15p-PB1-32]Triple-domain structure of RuO2 epitaxial films on c-Al2O3(0001) substrates
Sato Yukio1, Nguyen Anh2, Ohtsubo Yoshiyuki3, Ueno Tetsuro7, Kuroda Fumiaki4, Fukushima Tetsuya4, Haruto Ohboshi5, Ohya Shinobu5, 〇Hiroshi Naganuma6 (1.Kumamoto Univ., 2.Tohoku Univ. CSIS, 3.QST Nanoterasu, 4.AIST, 5.Univ.Tokyo, 6.Nagoya Univ., 7.QST)
Keywords:
RuO2,Triple-domain,STEM
Ruthenium dioxide (RuO2) is a prototypical altermagnetic material that exhibits long-range antiferromagnetic order together with momentum-dependent spin splitting, while maintaining zero net magnetization. Owing to these properties, RuO2 is regarded as a promising platform for antiferromagnetic spintronics, especially in high-quality epitaxial thin films. RuO2 thin films with a thickness of 50 nm were grown on c-Al2O3 (0001) substrates by reactive sputtering. Although a triple-domain epitaxial structure has been theoretically expected due to the threefold symmetry of the sapphire substrate, direct experimental evidence has been lacking. In this work, plane-view scanning transmission electron microscopy combined with inverse fast Fourier transform analysis enabled the first direct visualization of the triple-domain structure, clearly resolving three rotational domains and their spatial distribution. The antiferromagnetic properties were further investigated by X-ray magnetic linear dichroism measurements at the Ru M3,2 edge (KEK, PF BL16) and the Ru L3,2 edge (Nanoterasu, BL13U). No XMLD signal was detected under normal-incidence geometry, which is attributed to the cancellation of Néel vectors caused by the X-ray beam size being larger than the individual domain size. First-principles calculations incorporating spin-polarized core-level transitions successfully reproduced key features of the XMLD spectra. These results highlight the critical role of epitaxial domain structures in determining the magnetic response of altermagnetic RuO2 films.