Magnetocapacitance effect and magnetoelectric coupling in type-II multiferroic HoFeWO6

Abstract

We have investigated the multiferroicity and magnetoelectric (ME) coupling in $\mathrm{Ho}\mathrm{Fe}\mathrm{W}{\mathrm{O}}_{6}$. With a noncentrosymmetric polar structure (space group Pna${2}_{1}$) at room temperature, this compound shows an onset of electric polarization with an antiferromagnetic ordering at the N\'eel temperature (${T}_{N}$) of 17.8 K. The magnetic properties of the polycrystalline samples were studied by DC and AC magnetization and heat capacity measurements. The metamagnetic behavior at low temperatures was found to be directly related to the dielectric properties of the compound. In particular, field-dependent measurements of capacitance show a magnetocapacitance (MC) effect with double-hysteresis loop behavior in direct correspondence with the magnetization. Our x-ray diffraction results show the Pna${2}_{1}$ structure down to 8 K and suggest the absence of a structural phase transition across ${T}_{N}$. Soft x-ray absorption spectroscopy and soft x-ray magnetic circular dichroism (XMCD) measurements at the Fe $L{}_{2,3}$ and Ho $M{}_{4,5}$ edges revealed the oxidation state of Fe and Ho cations to be $3+$. Fe $L{}_{2,3}$ XMCD further shows that ${\mathrm{Fe}}^{3+}$ cations are antiferromagnetically ordered in a noncollinear fashion with spins arranged ${90}^{\ensuremath{\circ}}$ with respect to each other. Our findings show that $\mathrm{Ho}\mathrm{Fe}\mathrm{W}{\mathrm{O}}_{6}$ is a type-II multiferroic exhibiting a MC effect. The observed MC effect and the change in polarization by the magnetic field, as well as their direct correspondence with magnetization, further support the strong ME coupling in this compound.