SPECIAL CM Seminar: Negative thermal expansion in the plateau state of a magnetically-frustrated spinel

Karlo Penc
Hungarian Academy of Sciences
Tuesday, November 26, 2019
2:00 pm
RH 142
*Special Day / Time / Location
In the seminar I will discuss the negative thermal expansion in the high–field, half–magnetization plateau phase of the frustrated magnetic insulator CdCr2O4. In a collaboration with experimentalists, the phase diagram at fields of up to 30 T has been characterized using dilatometry. In the measurements a strong negative thermal expansion associated with the collinear half– magnetization plateau for B > 27 T has been identified. After discussing the experimental measurements, I will provide a simple microscopic theory for spin-lattice coupling, identifying the origin of the thermal expansion as a large negative change in magnetization with temperature, coming from a nearly–localised band of spin excitations in the plateau phase.
Judit Romhanyi