Magnetic structure and spin dynamics of a buckled-honeycomb antiferromagnet Co4Ta2O9

Controlling magnetism by the electric field is one of the most important topics in correlated materials, which could be realized via magnetoelectric (ME) coupling. The discovery of ME in Cr2O3 [1] initiates intense research on related ME materials for practical applications. However, there are not many real materials that show strong ME coupling due to rather strict symmetrical conditions: the absence of the inversion and time-reversal symmetry.

The interest was renewed when the Co4Nb2O9 study found a large ME coupling with an antiferromagnetic ordering [2]. Keeping this interest, we present a combined measurement of magnetic susceptibility, neutron diffraction and inelastic neutron scattering on Co4Ta2O9 [3]. We determined a magnetic order by single-crystal neutron diffraction and also performed inelastic neutron scattering to prove spin dynamics. We will discuss the implication of our results on the magnetic structure and spin excitations in the context of the magnetoelectricity of this material.

[1] I. E. Dzyaloshinskii, Sov. Phys. JETP 10, 628 (1960).
[2] N. D. Khanh et al, PRB 93, 075117 (2016); G. Deng et al, PRB 97, 085154 (2018).
[3] S. Choi et al (in preparation).