The 5^th DXMag-CMSM Special Seminar
(The 264^th Special CMSM seminar)

* Two talks will be held consecutively.

(Talk#1) Magnetic Stability in Monolayer Transition-Metal Dihalides

Dr. Thi Phuong Thao Nguyen Center for Spintronics Research Network,
Osaka University

Date & Time: 10:00 - 11:30, March 1^st (Fri), 2024.
Place: 8^th Floor Middle Conference Room, 8F, Main Bldg., Sengen site.

  Two-dimensional (2D) magnets have recently received increasing attention, not only in intrinsic ferromagnetic (FM) materials such as VI₃, and CrI₃ [1,2] but also in antiferromagnetic (AFM) materials. In 2D systems, triangular lattice typically causes magnetic frustration and often results in non-collinear magnetic orderings such as 120˚ AFM configuration. Recently, we have investigated the magnetism in a series of monolayer MCl₂ (M=V, Mn, and Ni) [3,4]. The resulting magnetic stability manifests a distinct chemical trend; VCl₂ and MnCl₂ show the 120˚ AFM ground states, and NiCl₂ shows the FM ground state. The microscopic mechanism behind the magnetic interaction is explained using the exchange coupling constants and the hopping integrals via the Wannier-function scheme. We also referred to the Goodenough-Kanamori-Anderson rules to explain the trend of magnetic interaction.

References
[1] T. P. T. Nguyen, K. Yamauchi, T. Oguchi, D. Amoroso, and S. Picozzi, Phys. Rev. B 104, 014414 (2021).
[2] A. De Vita, T. P. T. Nguyen, ..., K. Yamauchi, S. Picozzi, and G. Panaccione, Nano Lett. 22, 7034 (2022).
[4] K. Riedl, D. Amoroso, S. Backes, A. Razpopov, T. P. T. Nguyen, K. Yamauchi, P. Barone, S. M. Winter, S. Picozzi, and R. Valentí, Phys. Rev. B 106, 035156 (2022).
[5] T. P. T. Nguyen, and K. Yamauchi, arXiv:2308.06068. (to be published at JPSJ)

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Dr. Kunihiko Yamauchi Center for Spintronics Research Network,
Osaka University

Date & Time: 10:00 - 11:30, March 1^st (Fri), 2024.
Place: 8^th Floor Middle Conference Room, 8F, Main Bldg., Sengen site.

  “Altermagnetism” has emerged as a new class of magnetism, manifesting the spin splitting phenomena in the reciprocal space owing to the magnetic ordering that breaks the PT (parity times time-reversal) symmetry while the alternating spin configuration leads to vanishing magnetization in real space [1]. Several collinear antiferromagnetic materials are identified to exhibit altermagnetism, including RuO₂ and MnTe [2]. Recently, we have reported a theoretical study on CaCrO₃ as a prototypical perovskite transition-metal oxide that exhibits the altermagnetism and the sizable anomalous Hall effect [3]. Our symmetry analysis clarified that the antiferromagnetic order parameter belongs to the same irreducible representation as the ferromagnetic order parameter in the nonsymmorphic space group, allowing the nonvanishing Berry curvatures in the reciprocal space. By performing a first-principles calculation, we found that the Berry-curvature “hot spots” lie along the gapped nodal lines where spin-orbit coupling induces the spin splitting of Cr-3d bands near the Fermi energy and enhances the anomalous Hall effect in CaCrO₃.

References
[1] L. Šmejkal, J. Sinova, and T. Jungwirth, Phys. Rev. X 12, 031042 (2022); L. Šmejkal, J. Sinova, and T. Jungwirth, Phys. Rev. X 12, 040501 (2022).
[2] T. Osumi, S. Souma, T. Aoyama, K. Yamauchi, A. Honma, K. Nakayama, T. Takahashi, K. Ohgushi, and T. Sato, arXiv:2308.10117.
[3] T. P. T. Nguyen and K. Yamauchi, Phys. Rev. B 107, 155126 (2023).

Y.K. Takahashi, Magnetic Recording Materials Group
E-mail: TAKAHASHI.Yukiko[at]nims.go.jp