Magnetic frustration : between micro and macro levels

by Mike Zhitomirsky (CEA Grenoble)

Wednesday 8 Feb 2012, 11:15 → 12:15 Europe/Zurich

Salle 727 Cubotron (EPFL)

I will discuss theoretically two recent examples of frustrated magnetic systems. The first example concerns an XY pyrochlore antiferromagnet Er2Ti2O7. This frustrated magnet orders into an unusual noncoplanar magnetic structure. I show how such a spin state is stabilized by quantum order from disorder mechanism. An interesting signature of the above mechanism is presence of an "acoustic" mode in this strongly anisotropic antiferromagnet. In the second example I consider ferro- antiferromagnetic bilayers, which are widely used in the field of Spintronics. In the case of a compensated antiferromagnetic interface the coupling between the two layers vanishes in the mean-field approximation. I discuss how the canting of the antiferromagnetic structure lifts the degeneracy and how the mutual orientation of the antiferromagnetic order parameter and the ferromagnetic magnetization changes with temperature.