|日時||平成28年7月1日 (金) 14:00 – 15:00|
|場所||電子科学研究所 1階 セミナー室1-3|
|講演者||Woo Seok Choi 先生|
|タイトル||Topotactic phase transformation in SrFeOx epitaxial thin films （SrFeOxエピタキシャル薄膜のトポタクティック相転移）|
|概要||Topotactic phase transformation is a prominent platform for studying phase transition, redox activity, and ionic transport in a solid. In particular, for transition metal oxide thin films, the spontaneous oxygen vacancy ordering results in emergent physical ground states that can be tuned by crystal field energy and epitaxial strain. Designing and controlling such parameters might lead to novel opto-electronic and energy device concept. In this presentation, we report topotactic phase transformation in SrFeOx (SFO) epitaxial thin films grown by Pulsed Laser Epitaxy (PLE). Multivalent SFO show rich x-dependent magnetic and electronic ground state, ranging from antiferromagnetic insulator (x = 2.5) to ferromagnetic metal (x = 3.0). The valence state of Fe changes from 3+ to 4+ when x changes from 2.5 to 3.0, and determines the material’s physical and chemical properties. Eventually, a phase transition in electromagnetic phase, as well as in structural phase, is observed by changing x. Using real-time spectroscopic ellipsometry, we observe the x-dependent evolution of the phases in epitaxial SFO thin films. The topotactic phase transition illustrates strong correlation among defect concentration, atomic and electronic structure, and functional properties such as oxygen ionic transport and hydrogen storage capacity in complex oxide thin films.
参考文献：Nature Mater. 12, 1057 (2013), Nature Commun. 6, 7424 (2015)など
|連絡先||北海道大学 電子科学研究所 薄膜機能材料研究分野 太田裕道（内線 9428）|