Spin dynamics study and experimental realization of tunable single-ion anisotropy in multiferroic <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>Ba</mi><mn>2</mn></msub><msub><mi>CoGe</mi><mn>2</mn></msub><msub><mi mathvariant="normal">O</mi><mn>7</mn></msub></mrow></math> under external magnetic fields

Rajesh Dutta; Henrik Thoma; Igor Radelytskyi; Astrid Schneidewind; Vilmos Kocsis; Yusuke Tokunaga; Yasujiro Taguchi; Yoshinori Tokura; Vladimir Hutanu

doi:10.1103/PhysRevB.104.L020403

Letter

Spin dynamics study and experimental realization of tunable single-ion anisotropy in multiferroic ${Ba}_{2} {CoGe}_{2} O_{7}$ under external magnetic fields

Rajesh Dutta ^1,2,*, Henrik Thoma ^1,2, Igor Radelytskyi², Astrid Schneidewind ², Vilmos Kocsis^3,4,†, Yusuke Tokunaga^3,5, Yasujiro Taguchi ³, Yoshinori Tokura^3,6,7, and Vladimir Hutanu ^1,2

¹Institut für Kristallographie, RWTH Aachen Universität, 52066 Aachen, Germany
²Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum, 85747 Garching, Germany
³RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
⁴Department of Physics, Budapest University of Technology and Economics, and MTA-BME Lendület Magneto-optical Spectroscopy Research Group, 1111 Budapest, Hungary
⁵Department of Advanced Materials Science, University of Tokyo, Kashiwa 277-8561, Japan
⁶Quantum-Phase Electronics Center, Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
⁷Department of Applied Physics, University of Tokyo, Hongo, Tokyo 113-8656, Japan

^*Corresponding author: rajesh.dutta@frm2.tum.de
^†Present address: Institut für Festkörperforschung, Leibniz IFW Dresden, 01069 Dresden, Germany.

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Phys. Rev. B 104, L020403 – Published 7 July, 2021

DOI: https://doi.org/10.1103/PhysRevB.104.L020403

Abstract

We report a spin-wave study on multiferroic ${Ba}_{2} {CoGe}_{2} O_{7}$ under magnetic fields up to 12 T using low-energy inelastic neutron scattering. In-plane transverse $(T_{1})$ spin-wave modes are highly dispersive along $(h 00)$ and rather flat but strong in intensity along $(30 l)$ . In addition, two dispersive electromagnon modes have been observed around 3.5 meV. Dispersion of the out-of-plane transverse modes $(T_{2})$ under fields reveals that the single-ion anisotropy constant decreases with increasing magnetic field, which is consistent with the linear spin-wave theory. Our results imply that the field-dependent single-ion anisotropy plays a crucial role in determining the characteristics of $T_{2}$ and electromagnon modes in the three-dimensional anisotropic spin-wave spectrum.

Physical Review B

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Spin dynamics study and experimental realization of tunable single-ion anisotropy in multiferroic ${Ba}_{2} {CoGe}_{2} O_{7}$ under external magnetic fields

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Spin dynamics study and experimental realization of tunable single-ion anisotropy in multiferroic Ba2CoGe2O7 under external magnetic fields

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Spin dynamics study and experimental realization of tunable single-ion anisotropy in multiferroic ${Ba}_{2} {CoGe}_{2} O_{7}$ under external magnetic fields