Nature of Magnetoelectric coupling in corundum antiferromagnet Co4Ta2O9

TL;DR

This study investigates the magnetoelectric coupling in Co4Ta2O9, revealing that dielectric changes are proportional to magnetization squared and that electric polarization depends on magnetic field cooling, with implications for multiferroic behavior.

Contribution

The paper provides a phenomenological analysis of magnetocapacitance and estimates key magnetoelectric parameters in Co4Ta2O9, highlighting the non-ferroelectric ground state.

Findings

Dielectric constant change proportional to magnetization squared

Saturation polarization of 52 μC/m² at 6 Tesla

Magnetoelectric coupling coefficient γ = 1.4 x 10⁻³ (emu/g)⁻²

Abstract

We study the magnetocapacitance (MC) effect and magnetoelectric (ME) coupling in spin-flop driven antiferromagnet Co4Ta2O9. The magnetocapacitance data at high magnetic fields are analyzed by phenomenological Ginzburg-landau theory of ferroelectromagnets and it is found that change in dielectric constant is proportional to the square of magnetization. The saturation polarization and magnetoelectric coupling are estimated to be 52microC/m2 and $\gamma$ = 1.4 x10-3 (emu/g)-2 respectively at 6 Tesla. Electric polarization is achieved below Neel temperature only when the sample is cooled in the presence of magnetic field and it is established that the ground state is non-ferroelectric implying that magnetic lattice does not lead to spontaneous symmetry breaking in Co4Ta2O9.