Anisotropic spin-density distribution and magnetic anisotropy of strained La1−xSrxMnO3 thin films: angle-dependent x-ray magnetic circular dichroism

• Published in: npj quantum materials Vol. 3; no. 1
• Main Authors: Shibata, Goro, Kitamura, Miho, Minohara, Makoto, Yoshimatsu, Kohei, Kadono, Toshiharu, Ishigami, Keisuke, Harano, Takayuki, Takahashi, Yukio, Sakamoto, Shoya, Nonaka, Yosuke, Ikeda, Keisuke, Chi, Zhendong, Furuse, Mitsuho, Fuchino, Shuichiro, Okano, Makoto, Fujihira, Jun-ichi, Uchida, Akira, Watanabe, Kazunori, Fujihira, Hideyuki, Fujihira, Seiichi, Tanaka, Arata, Kumigashira, Hiroshi, Koide, Tsuneharu, Fujimori, Atsushi
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 26.01.2018; Nature Publishing Group
• Subjects: 639/766/119/2793; 639/766/119/544; 639/766/119/995; 639/766/119/997; Anisotropy; Compressive properties; Condensed Matter Physics; Density distribution; Dichroism; Electron spin; Electrons; Epitaxial growth; Ferromagnetic materials; Magnetic anisotropy; Magnetic moments; Magnetism; Physics; Physics and Astronomy; Quantum Physics; Spatial distribution; Strontium titanates; Structural Materials; Substrates; Surfaces and Interfaces; Tensile strain; Thin Films
• ISSN: 2397-4648
• DOI: 10.1038/s41535-018-0077-4

Magnetic anisotropies of ferromagnetic thin films are induced by epitaxial strain from the substrate via strain-induced anisotropy in the orbital magnetic moment and that in the spatial distribution of spin-polarized electrons. However, the preferential orbital occupation in ferromagnetic metallic La 1− x Sr x MnO 3 (LSMO) thin films studied by x-ray linear dichroism (XLD) has always been found out-of-plane for both tensile and compressive epitaxial strain and hence irrespective of the magnetic anisotropy. In order to resolve this mystery, we directly probed the preferential orbital occupation of spin-polarized electrons in LSMO thin films under strain by angle-dependent x-ray magnetic circular dichroism (XMCD). Anisotropy of the spin-density distribution was found to be in-plane for the tensile strain and out-of-plane for the compressive strain, consistent with the observed magnetic anisotropy. The ubiquitous out-of-plane preferential orbital occupation seen by XLD is attributed to the occupation of both spin-up and spin-down out-of-plane orbitals in the surface magnetic dead layer. Magnetic anisotropy: spatial anisotropy of spin-polarized electrons probed Enabled by an angular dependent magneto-optical technique, the orbital states of spin-polarized electrons in La 1-x Sr x MnO 3 thin films are directly probed. Goro Shibata from University of Tokyo and colleagues in Japan use an angular dependent x-ray magnetic circular dichroism (XMCD) technique to study the magnetic anisotropy of epitaxial La 1− x Sr x MnO 3 (LSMO) thin films grown on SrTiO 3 (STO) or LaAlO 3 (LAO) substrate. The different substrates provide either tensile (STO) strain or compressive (LAO) strain. The strain modifies the orbital shapes of the spin-polarized electrons in LSMO layer, which can be directly probed by XMCD. The results show that the LSMO thin film under tensile (compressive) strain has in-plane (out-of-plane) spin-density distribution, which can be attributed to the preferential occupation of out-of-plane spin states at the surface. This helps to understand the strain controlled magnetic anisotropy in related materials.