Magnetic frustration : from lattice geometry to multilayers

Orateur : Mike ZHITOMIRSKY (INAC/SPSMS, CEA Grenoble)

Search for new magnetic materials and means for their control is central for both fundamental and applied research in Magnetism. Recently, a lot of attention in fundamental research was focused on magnetically frustrated systems. In the first part, I shall provide a general introduction into geometrically frustrated magnets focusing on fundamental, the order from disorder effect, and applied aspects, enhanced magnetocaloric effect. In the second part, I discuss a simple example of frustration relevant to the exchange bias systems : ferro-/antiferromagnetic bilayer with compensated antiferromagnetic interface. At low temperatures the bilayer exhibits an orthogonal magnetic state with 90-degree orientation between ferromagnetic magnetization and antiferromagnetic sublattices. Using analytic theory and Monte Carlo simulations we investigate how such an orthogonal structure changes with temperature. In particular, we predict a reorientatinal transition to a collinear state, which may occur either above or below the Neel temperature depending on dimensionality of the antiferromagnetic film.

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