title: Observation of Orbital Order in the Half-Filled 4f Gd Compound.
abstract: Half-filled electron systems, even with the maximized spin angular moment, have been given little attention because of their zero-orbital angular moment according to Hund's rule. Nevertheless, there are several measurements that show evidence of a nonzero orbital moment as well as spin-orbit coupling. Here we report for the first time the orbital order in a half-filled 4f-electron system GdB_{4}, using the resonant soft x-ray scattering at Gd M_{4,5}-edges. Furthermore, we discovered that the development of this orbital order is strongly coupled with the antiferromagnetic spin order. These results clearly demonstrate that even in half-filled electron systems the orbital angular moment can be an important parameter to describe material properties, and may provide significant opportunities for tailoring new correlated electron systems.
authors.affiliation: Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: H
authors.initials: H
authors.lastname: Jang
authors.affiliation: School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 61005, Korea.
authors.forename: B Y
authors.initials: BY
authors.lastname: Kang
authors.affiliation: School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 61005, Korea.
authors.forename: B K
authors.initials: BK
authors.lastname: Cho
authors.affiliation: Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: M
authors.initials: M
authors.lastname: Hashimoto
authors.affiliation: Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: D
authors.initials: D
authors.lastname: Lu
authors.affiliation: Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.|Department of Physics, Western Michigan University, Kalamazoo, Michigan 49008, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Burns
authors.affiliation: SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: C-C
authors.initials: CC
authors.lastname: Kao
authors.affiliation: Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: J-S
authors.initials: JS
authors.lastname: Lee