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Magnetic skyrmions are spin textures somewhat analogous to vortices, which might become the elementary bricks of future electronics. Although industrial applications mostly deal with thin layers, studying bulk materials yields detailed information about the nature of magnetic interactions, which could be crucial for a fine tuning of the material. Such compounds are often frustrated, resulting in low transitions temperatures TC (a few dozens of Kelvin). Small angle neutron scattering (SANS) allow one to observe such spin textures, and they were historically the first ones to visualize skyrmion lattices. Single crystals neutron studies are crucial to discriminate skyrmion phases from casual helixes.
The thesis at the interface of physics and chemistry consists in the synthesis and neutron study of CoZnMn alloys in poly-crystal and single crystal form, hosting magnetic skyrmions in the neighborhood of TC. Their transition temperatures can go beyond 300K and strongly vary with concentration. The goal is to determine for each compound the magnetic phase diagram, then the spin fluctuations. The thesis will be performed in close collaboration between ICMMO (synthesis, magnetic and X ray study directed by C. Decorse) and LLB (neutron experiments performed at Orphée and ILL-Grenoble, directed by I. Mirebeau and N. Martin)