Invariable Simultaneous Emergence of Antiferromagnetic Order and Tetragonal Deformation in CoO Nanocrystals

It remains unclear why type-II antiferromagnetic order with a propagation vector along a trigonal axis and a tetragonal Jahn–Teller deformation coexist in a low-temperature phase of CoO. Nanocrystals generally have a lower magnetic transition temperature but crystal size reduction does not affect st...

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Bibliographic Details
Published in:	Journal of the Physical Society of Japan Vol. 93; no. 4; p. 1
Main Authors:	Ishiwata, Yoichi, Kawahara, Gaku, Akase, Keisuke, Tominaga, Taisuke, Miyazaki, Hayato, Ishii, Hirofumi, Matsuo, Akira, Kindo, Koichi, Inagaki, Yuji, Akashi, Kenta, Kawae, Tatsuya, Kida, Tetsuya, Suehiro, Satoshi, Nantoh, Masashi, Ishibashi, Koji
Format:	Journal Article
Language:	English
Published:	Tokyo The Physical Society of Japan 15-04-2024
Subjects:	Antiferromagnetism Cobalt Deformation Electron spin Jahn-Teller effect Low temperature Magnetic properties Magnetic transitions Nanocrystals Transition temperature
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Summary:	It remains unclear why type-II antiferromagnetic order with a propagation vector along a trigonal axis and a tetragonal Jahn–Teller deformation coexist in a low-temperature phase of CoO. Nanocrystals generally have a lower magnetic transition temperature but crystal size reduction does not affect structural transition locally induced by a crystal field. On this basis, we investigated the magnetic and structural properties of CoO nanocrystals. Both transition temperatures were equally reduced in nanocrystals, which indicates that magnetic order triggers the tetragonal deformation. This observation is consistent with a model that the Jahn–Teller deformation is assisted by spin–orbit energy splitting of t2g electrons in the high-spin Co2+ ion, proposed by Kugel and Khomskii.
ISSN:	0031-9015 1347-4073
DOI:	10.7566/JPSJ.93.044603