Condensed Matter Physics Seminar

2 p.m., Thursday, April 12, 2007
Room 1201, Physics Building

Electromagnons in Multiferroics

Andrei Sushkov

(University of Maryland)

Abstract: In multiferroic materials the simultaneous magnetic and ferroelectric order can produce cross coupling between electric and magnetic signals. This has important implications for electronic memory and logic applications which has stimulated renewed interest in these materials. On the other hand, multiferroics exhibit interesting new fundamental features. The absence of both time and inversion space symmetry in relatively low symmetry crystal structures can produce a rich array of novel magneto-electric phenomena. One such effect is the coupling between the low lying magnetic and lattice excitations to produce spin waves that interact strongly with light by acquiring electric dipole activity from the phonons. Therefore these excitations, called electromagnons, produce a contribution to the static dielectric constant which is the origin of the giant magneto-capacitance effect observed in these materials. We have recently observed a colossal coupling between spin waves and phonons in (Eu,Y)MnO₃ in which more than 50% of the dipole oscillator strength of a phonon is transferred to a spin excitation. The properties of these novel excitations will be reviewed.

Host: Drew
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