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Chiral Ferromagnets: The Search for New Materials

Event Details

Event Dates: 

Thursday, May 3, 2012 - 6:00am

Speaker Name(s): 

David Mandrus

Speaker Affiliation(s): 

University of Tennessee and ORNL
Seminar Type/Subject

Event Details & Abstract: 

A few itinerant magnets are known that form incommensurate, long period spirals.  The chiral nature of these magnets means that the spirals in a particular material have a certain handedness, and that right- and left-handed spirals are not degenerate.  These helicoidal structures have long been recognized as being related (at least at the level of Landau theory) to helical phases in cholesteric liquid crystals. A key structure-property relationship is that systems lacking inversion symmetry support Dzyaloshinskii-Moriya (DM) spin-orbit interactions.  These interactions add a term to the free energy favoring perpendicular orientation of the spins.  In insulating systems, the DM interactions can produce weak ferromagnetism and can also lead to multiferroic coupling.  In metallic systems the DM term can lead to helimagnetism and, as has recently been discovered, to complex spin textures when the helimagnetism is destabilized.  In this talk I will review some recent developments in the field and will discuss some new, related families of materials that we are exploring at UT and ORNL.