Thickness-dependent magnetic properties and strain-induced orbital magnetic moment in SrRuO thin films

SrRuO薄膜における膜厚に依存した磁気的性質と歪誘起軌道磁気モーメント

石上 啓介*; 吉松 公平*; 豊田 大介*; 滝沢 優*; 吉田 鉄平*; 芝田 悟朗*; 原野 貴幸*; 高橋 文雄*; 門野 利治*; Verma, V. K.*; Singh, V. R.*; 竹田 幸治   ; 岡根 哲夫  ; 斎藤 祐児  ; 山上 浩志; 小出 常晴*; 尾嶋 正治*; 組頭 広志*; 藤森 淳*

Ishigami, Keisuke*; Yoshimatsu, Kohei*; Toyota, Daisuke*; Takizawa, Masaru*; Yoshida, Teppei*; Shibata, Goro*; Harano, Takayuki*; Takahashi, Yukio*; Kadono, Toshiharu*; Verma, V. K.*; Singh, V. R.*; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Yamagami, Hiroshi; Koide, Tsuneharu*; Oshima, Masaharu*; Kumigashira, Hiroshi*; Fujimori, Atsushi*

Thin films of the ferromagnetic metal SrRuO (SRO) show a varying easy magnetization axis depending on the epitaxial strain, and undergo a metal-to-insulator transition with decreasing film thickness. We have investigated the magnetic properties of SRO thin films with varying thicknesses fabricated on SrTiO(001) substrates by soft X-ray magnetic circular dichroism at the Ru M2,3 edge. Results have shown that, with decreasing film thickness, the film changes from ferromagnetic to nonmagnetic at around 3 monolayer thickness, consistent with previous magnetization and magneto-optical Kerr effect measurements. The orbital magnetic moment perpendicular to the film was found to be 0.1B/Ru, and remained nearly unchanged with decreasing film thickness while the spin magnetic moment decreases. A mechanism for the formation of the orbital magnetic moment is discussed based on the electronic structure of the compressively strained SRO film.