R. G. Herb Condensed Matter Seminars |
Events on Thursday, May 22nd, 2008
- Order by distortion and chiral magnetism in frustrated pyrochlore magnet
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Gia-Wei Chern, Johns Hopkins University
- Abstract: Flexible pyrochlore antiferromagnet is known to be unstable
against lattice distortion which relieves the magnetic frustration
and makes long-range magnetic order possible. In many cases
the distortion breaks the inversion symmetry, thus making the
crystal structure chiral. The handedness is transferred to the
magnetic order by the relativistic spin-orbit coupling, which is manifested as the Dzyaloshinskii-Moriya (DM) interaction between nearest-neighbor spins. In this talk, I will discuss the basic mechanism of degeneracy-breaking through spin-lattice coupling in pyrochlore antiferromagnet. The chiral nature of the DM interaction is important to the determination of the resulting ground state magnetic order. Our theoretical model successfully describes the ground state of spinel CdCr2O4. I will also give other more complicated examples and our speculations on the magnetic order of ZnCr2O4. - Host: Natalia Perkins