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Ferromagnetic moment in the magnetoelectric antiferromagnet Co4Ta2O9: Evidence of the P1 magnetic space group

Rahul Goel1,2,3, Kwanghyo Son4,5, Matthias J. Gutmann6, Dong Gun Oh7, Kapil Kumar3, Anzar Ali1,2,8, Suk Jin Mun1,2, Dnyaneshwar Bhosale1,2,*, Gideok Kim1,8,9 et al.

Nara Lee7, Young Jai Choi7, Sang-Wook Cheong10,11, Valery Kiryukhin10, and Sungkyun Choi1,2,3,10,†

  • *Present address: Forschungszentrum Jülich, Lichtenbergstrasse 1, 85747 Garching, Germany.
  • †Contact author: sungkyunchoi@ibs.re.kr
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Phys. Rev. Research 7, 043196 – Published 20 November, 2025

DOI: https://doi.org/10.1103/7gx9-wx2b

Abstract

Exploring ferromagnetic moments in magnetoelectric materials is of both fundamental and technological importance. It enables the control of the correlated state using an uncompensated moment. However, its material realization is challenging owing to its exclusive microscopic mechanisms. Here, we report a nearly isotropic ferromagnetic moment in the magnetoelectric antiferromagnet Co4Ta2O9, by performing dc and ac magnetic susceptibility, magnetization, and neutron diffraction measurements on identical single crystals. Combined with the group theory analysis, we demonstrate a P1 magnetic space group. This implies that physical activities can occur along any crystallographic direction, which explains the unusual magnetoelectric property of Co4Ta2O9. The ground state is classified as the M-type altermagnet based on the magnetic point group. Our study provides essential information to resolve the debate on the magnetic ground state and understand the magnetoelectric properties of the related compound with the prospect of observing and examining the P1 magnetic space group or ferromagnet in ferroelectrics.

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Phys. Rev. Research 7, 043196– Published 20 November, 2025
  • Received 10 March 2025
  • Accepted 22 October 2025
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