title: Room-temperature local ferromagnetism and its nanoscale expansion in the ferromagnetic semiconductor Ge(1-x)Fex.
abstract: We investigate the local electronic structure and magnetic properties of the group-IV-based ferromagnetic semiconductor, Ge(1-x)Fex (GeFe), using soft X-ray magnetic circular dichroism. Our results show that the doped Fe 3d electrons are strongly hybridized with the Ge 4p states, and have a large orbital magnetic moment relative to the spin magnetic moment; i.e., morb/mspin ≈ 0.1. We find that nanoscale local ferromagnetic regions, which are formed through ferromagnetic exchange interactions in the high-Fe-content regions of the GeFe films, exist even at room temperature, well above the Curie temperature of 20-100 K. We observe the intriguing nanoscale expansion of the local ferromagnetic regions with decreasing temperature, followed by a transition of the entire film into a ferromagnetic state at the Curie temperature.
authors.affiliation: Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Yuki K
authors.initials: YK
authors.lastname: Wakabayashi
authors.affiliation: Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Shoya
authors.initials: S
authors.lastname: Sakamoto
authors.affiliation: Quantum Beam Science Center, JAEA, Sayo, Hyogo 679-5148, Japan.
authors.forename: Yuki-haru
authors.initials: YH
authors.lastname: Takeda
authors.affiliation: Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Ishigami
authors.affiliation: Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Takahashi
authors.affiliation: Quantum Beam Science Center, JAEA, Sayo, Hyogo 679-5148, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Saitoh
authors.affiliation: Quantum Beam Science Center, JAEA, Sayo, Hyogo 679-5148, Japan.|Department of Physics, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-Ku, Kyoto 603-8555, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamagami
authors.affiliation: Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Fujimori
authors.affiliation: Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Tanaka
authors.affiliation: Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Shinobu
authors.initials: S
authors.lastname: Ohya