Stabilized helical spin order and multiferroic phase coexistence in MnWO4: Consequence of4dRu substitution of Mn

Abstract

[Abstract] So far most of earlier works on the effect of chemical substitution in multiferroic MnWO 4 have focused on the 3d transition metal substitution of Mn. In this work we investigate the Ru substitution of Mn in polycrystalline Mn 1-x Ru x/2 WO 4 in order to unveil the consequence of 4d transition metal substitution in terms of magnetic transitions and ferroelectricity. It is found that the Ru substitution substantially reshuffles the magnetic frustration and stabilizes the incommensurate helical spin order phase (AF2) by partially suppressing the collinear spin order phase (AF1 phase). The coexistence of the AF2 phase and AF1 phase at low temperature is suggested. Consequently, the ferroelectric polarization is remarkably enhanced, in accompanying with significant response of the polarization to magnetic field. It is argued that the structural distortion and enhanced spin-orbital coupling associated with the Ru substitution may be responsible for this ferroelectricity enhancement.

Modulated multiferroic phases and electric polarization in Mn1−xRuxWO4+δ

“…The magnetic behaviors are quite similar to those reported in earlier work 18 and no details of them are presented here. More attention is paid to the ferroelectric behaviors.…”

“…These features remain similar qualitatively to those observed in Mn 1Àx Ru x/2 WO 4 . 18 These observed phenomena can be reasonably understood from several aspects. First, the lattice constants decrease gradually with increasing x, while angle b remains roughly unchanged.…”

“…In fact, preliminary experiments on Ru substitution of Mn in Mn 1Àx Ru x/2 WO 4 revealed a spontaneous polarization almost one order of magnitude larger than that of pure MWO. 18 The AF1 phase was gradually suppressed by the AF2 phase, while the polarization at x ¼ 0.20 reached up to 60 lC/m 2 . However, our understanding of the microscopic mechanism for the high stability of the AF2 phase against the AF1 phase remains elusive.…”

“…18 Here, only a brief description of the preparation procedure is given. Stoichiometric amount of WO 3 , RuO 2 , and MnO were chosen as reagents and thoroughly mixed for 24 h. The dried mixture was ground for 1 h and then annealed in air for 12 h at 600 C. After several intermediate grindings, the mixture was compressed into pellets with diameter of 20 mm and then annealed at 950 C for 20 h in air.…”

Pressure effects on magnetic ground states in cobalt-doped multiferroicMn1−xCoxWO4

“…The system is susceptible to different perturbations including magnetic field [13,[22][23][24][25] and chemical doping [26][27][28][29][30][31].…”