Crystal structure, incommensurate magnetic order, and ferroelectricity inMn1−xCuxWO4 (0 ≤x≤ 0.19)

Abstract

We have carried out a systematic study on the effect of Cu doping on nuclear, magnetic, and dielectric properties in ${\mathrm{Mn}}_{1\ensuremath{-}x}{\mathrm{Cu}}_{x}{\mathrm{WO}}_{4}$ for $0\ensuremath{\le}x\ensuremath{\le}0.19$ by a synergic use of different techniques, viz, heat capacity, magnetization, dielectric, and neutron powder diffraction measurements. Via heat capacity and magnetization measurements we show that with increasing Cu concentration magnetic frustration decreases, which leads to the stabilization of commensurate magnetic ordering. This was further verified by temperature-dependent unit cell volume changes derived from neutron diffraction measurements which was modeled by the Gr\"uneisen approximation. Dielectric measurements show a low temperature phase transition below about 9--10 K. Furthermore, magnetic refinements reveal no changes below this transition indicating a possible spin-flop transition which is unique to the Cu doped system. From these combined studies we have constructed a magnetoelectric phase diagram of this compound.