Field dependence of magnetic correlations through the polarization flop transition in multiferroic TbMnO3 : evidence for a magnetic memory effect

摘要

The field-induced multiferroic transition in TbMnO3 has been studied byneutron scattering. Apart strong hysteresis, the magnetic transition associatedwith the flop of electronic polarization exhibits a memory effect: after afield sweep, TbMnO3 does not exhibit the same phase as that obtained byzero-field cooling. The strong changes in the magnetic excitations across thetransition perfectly agree with a rotation of the cycloidal spiral planeindicating that the inverse Dzyaloshinski-Moriya coupling causes the giantmagnetoelectric effect at the field-induced transition. The analysis of thezone-center magnetic excitations identifies the electromagnon of themultiferroic high-field phase.