Date/Time
Date(s) - 02/03/2005
3:30 pm - 4:30 pm

Title: FERROELECTRIC MAGNETS

Speaker: Dr. Brooks Harris

Institute: University of Pennsylvania

Location: ABB 102

Description:

Ferroelectric materials which become magnetic when the temperature is reduced are not uncommon. In contrast, materials in which ferroelectric and magnetic long range order occur simultaneously in a single phasetransition are rare. These magnetoferroelectrics are often associated with incommensurate magnetic order, although their behavior has not been understood theoretically. Here I discuss an approach based on symmetry and a Landau expansion which gives a phenomenological explanation of the observed properties of a magneto-electric quantum magnet Ni3V2O8 (NVO). This approach is only possible because the magnetic structure of NVO has been comprehensively studied [see PRL 93, 247201 (2004)]. Unlike classifications based solely on crystal symmetry, this theory leads to a prediction of the dependence of the spontaneous polarization on magnetic field and temperature. This explanation undoubtedly applies to other magnetoferroelectrics.