Sumanta Tewari
Condensed Matter Theory Center
Department of Physics
University of Maryland

Abstract

''Phenomenological Theory of the Non-Collinear Magnetic States in Multiferroics''

Multiferroics are materials that display an amazing coexistence and interplay of long range ferromagnetic and ferroelectric orders. The magnetization (ferroelectric polarization) of these materials can be altered by applying an electric (magnetic) field, such cross-correlations leading to intense interest in the possibility of novel magnetoelectric devices. It was observed recently that the multiferroics that show the strongest sensitivity of polarization to an applied magnetic field are non-collinear spiral magnets. The spiral magnetic ordering, in which the local magnetization rotates around a direction in space (pitch vector), spontaneously breaks coordinate space inversion symmetry giving rise to the macroscopic polarization. Since the polarization is inherently of magnetic origin, the cross-correlations between the colluding order parameters are anomalously large. With hints from the theories of some liquid crystals, which bear a family resemblance to these systems, in  this talk I shall develop a phenomenological description of this new class of multiferroics. The resulting theory will allow us to explain as well as predict many unusual and outstanding experimental observations.

Please come meet the speaker over refreshments from 3:45-4:10pm in the foyer on floor G above the lecture hall. All Welcome Host: Doerte Blume