Journal Article Spin state ordering of strongly correlating LaCoO3 induced at ultrahigh magnetic fields

Ikeda, Akihiko  ,  Nomura, Toshihiro  ,  Matsuda, Yasuhiro H.  ,  Matsuo, Akira  ,  Kindo, Koichi  ,  Sato, Keisuke

93 ( 22 ) 2016-06-06 , American Physical Society , Institute for Solid State Physics, University of Tokyo , Ibaraki National College of Technology, Department of Natural Science
ISSN:1550-235X (online)
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UTokyo Research掲載「半世紀に渡るコバルト酸化物の謎を解き明かす」 URI: http://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/solving-the-problem-of-half-a-century-over-cobalt-oxides.html
UTokyo Research "Solving the problem of half a century over cobalt oxides" URI: http://www.u-tokyo.ac.jp/en/utokyo-research/research-news/solving-the-problem-of-half-a-century-over-cobalt-oxides.html
Magnetization measurements of LaCoO3 have been carried out up to 133 T, generated with a destructive pulse magnet at a wide temperature range from 2 to 120 K. A novel magnetic transition was found atB > 100 T and T >T * = 32 ± 5 K, which is characterized by its transition field increasing with increasing temperature. At T <T*, the previously reported transition at B ∼ 65 T was observed. Based on the obtained B-T phase diagram and the Clausius-Clapeyron relation, the entropy of the high-field phase at 80 K is found to be smaller for about 1.5 J K-1 mol-1 than that of the low-field phase.We suggest that the observed two high-field phasesmay originate in different spatial orders of the spin states and possibly other degrees of freedom such as orbitals. An inherent strong correlation of spin states among cobalt sites should have triggered the emergence of the ordered phases in LaCoO3 at high magnetic fields.
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