Prof. Hajime Yamamoto（山本 孟）[Tohoku University, Japan]

Title: High-pressure synthesis and cation dimerization phenomenon in ilmenite-type vanadium oxides  

Language:  English presentation

Time: 10:00 - 12:00, Tuesday, December 17, 2024

Place: Onsite：Conference room A417, HPSTAR (Beijing)

          Online:  Tencent Meeting: https://meeting.tencent.com/dm/sHkXGlY7aHci    Meeting ID: 599-267-653

Host:  Dr. Runze Yu

Abstract:

Cation dimerization refers to the formation of direct chemical bonds between neighboring cations in crystalline compounds. Such a phenomenon is known as the Peierls transition in VO2 and has been a topic of interest in the field of solid-state physics and chemistry. Recently, we found that the cation dimerization (V-V dimerization) was observed in the ilmenite-type vanadium oxides, such as MgVO3, CoVO3, MnVO3, NiVO3, and ZnVO3.1-6 These compounds are synthesized using a high-pressure synthesis method. Synchrotron X-ray powder diffraction experiments reveal that the V-V dimerization occurs around 500 K, which induces a structure phase transition from a rhombohedral to a triclinic phase. The V-V dimers are arranged in a ladder-like order in the vanadium′s honeycomb lattice. The V-V dimerization is accompanied by a magnetic (metal) to nonmagnetic (insulator) phase transition, which is ascribed to the formation of the covalent bond between adjacent vanadium ions. Considering that the V-V dimerization leads to changes in crystal symmetry and electronic structure, the magnetic properties of MVO3 (in the case that M is a magnetic ion) can be switched by the dimerization.3,7 In this presentation, we will discuss the details of the V-V dimerization and characteristic properties in some ilmenite-type vanadium oxides.

1. H. Yamamoto et al., J. Am. Chem. Soc., 144, 1082-1086 (2022).

2. H. Yamamoto et al., Appl. Phys. Lett., 120, 201901 (2022).

3. S. Kamiyama, H. Yamamoto, et al. Inorg. Chem., 61, 7841-7864 (2022).

4. S. Kamiyama, H. Yamamoto, et al. Cryst. Growth Design, 23, 2296-2300 (2023).

5. H. Yamamoto et al., Phys. Rev. Mater., 8, 094402 (2024).

6. H. Yamamoto et al., Dalton Trans., 53, 16195-16201 (2024). 

7. H. Yamamoto et al., Appl. Phys. Lett., 123, 132404 (2023).

Biography of the Speaker:

Hajime Yamamoto (山本 孟) is an assistant professor of the Institute of Multidisciplinary Research for Advanced Materials, Tohoku University (東北大学), Japan. He received his PhD from Tokyo Institute of Technology under the supervision of Prof. Masaki Azuma (東正樹), and joined Tohoku University as an assistant professor in 2018. He was a visiting researcher at Northwestern University in 2016 and at Néel Institute, CNRS in 2024. His research interest liesin high-pressure synthesis, quantum beam experiments including synchrotronx-ray and neutron, and exploration of novel properties such as magnetism, strongly correlated electron phenomena, ferroelectricity, and exotic electronic transitions.