A research group of Prof. Shin-ichi Kimura at Institute for Molecular Science, National Institute of Nature Sciences and Prof. Toshiro Takabatake at Graduate School of Advanced Sciences of Matter, Hiroshima University has clarified a novel mechanism of magnetism in rare-earth compounds. They observed the temperature-dependent electronic structure of a rare-earth compound CeOs2Al10 using a polarized optical reflectivity measurement in the very wide wavelength region from 10 nm to 1 mm from a synchrotron radiation light source UVSOR-II, Institute for Molecular Science.
In rare-earth compounds, the Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction (Fig. 1a) is known to be the origin of the ferro- and antiferro-magnetism. The magnetic transition temperature in compounds with cerium (Ce) element, which is one of rare-earth elements, is predicted to be less than 1 Kelvin (-274 degree-Celcius). However, a recently discovered Ce compound CeOs2Al10 shows an antiferromagnetic transition at 29 K. The origin cannot be explained by the RKKY interaction and has not been revealed. The research group observed the anisotropic changes in the electronic structure of CeOs2Al10 across the antiferromagnetic ordering temperature. The spectra in the ac plane indicate that an energy gap due to the hybridization between conduction bands and nearly local 4f states emerges from a higher temperature. Along the b axis, on the other hand, another energy gap with a peak at 20 meV fully opens at the antiferromagnetic ordering temperature because of a charge instability. This result implies that the appearance of the energy gap, as well as the change in the electronic structure along the b axis, induces the antiferromagnetic ordering (Fig. 1b).
Fig 1. Magnetic coupling mechanism due to the RKKY interaction (a) and the charge instability (b).
Contact
Prof. Shin-ichi Kimura, Institute for Molecular Science, National Institute of Nature Sciences
Prof. Toshiro Takabatake at Graduate School of Advanced Sciences of Matter, Hiroshima University
Paper Information
Journal: Physical Review Letters, vol. 106, 056404 (2011).
Title: Electronic-Structure-Driven Magnetic Ordering in a Kondo Semiconductor CeOs2Al10
Author: Shin-ichi Kimura, Takuya Iizuka, Hidetoshi Miyazaki, Akinori Irizawa, Yuji Muro, and Toshiro Takabatake
