Electric-field control of the chiral magnetism of multiferroicMnWO4as seen via polarized neutron diffraction

Abstract

The chiral components in the magnetic order in multiferroic MnWO 4 have been studied by neutron diffraction using spherical polarization analysis as a function of temperature and of external electric field. We show that sufficiently close to the ferroelectric transition at T = 12.3 K it is possible to switch the chiral component by applying moderate electric fields at constant temperature. Full hysteresis cycles can be observed which indicate strong pinning of the magnetic order. MnWO 4 , furthermore, exhibits a magnetoelectric memory effect across heating into the paramagnetic and paraelectric phase.

Kinetics of the multiferroic switching inMnWO4

“…This is in accordance with the large coercive fields found in the quasi-static experiments 17,32 . The slow multiferroic rise times underline the importance of the lattice in the control of domains.…”

“…Therefore also the rotation of neutron polarization can be analyzed. The chiral ratio can be measured equally well in several channels of the neutron polarization matrix 17,25 . It can be detected in the spin-flip scattering with polarization parallel to the scattering vector:…”

“…The chiral ratio for a mono-domain sample can easily be calculated from the magnetic structure 17 . The deviation with the experiment then directly gives the distribution of the chiral domains.…”

Strong magnetoelastic coupling at the transition from harmonic to anharmonic order inNaFe(WO4)2with3d5Simon1, Ackermann2, Chapon3 et al. 2016Phys. Rev. BSelf Cite134220View full textAdd to dashboardCite

“…This is an essential difference to MnWO 4 where the incommensurate magnetic modulation is much further away from the commensurate value. Anharmonic components were also observed in the AF2 phase of MnWO 4 22 and there they are related with magnetoelectric memory effects observed for the electric-field control of multiferroic domains 23,24 .…”

“…Note, however, that this incommensurate vector is very close to (0.5, 0.5, 0.5), so that the magnetic structure still locally resembles the up-up-down-down sequence shown in TABLE II: Character table and symmetry conditions of the little Group G k ic = P c, kic = (δH , 0.5, δL) with a = e −i2π·δ L ·rz = e −i2π·0. 24 .…”