Ferroelectric and non-collinear magnetic phases in lacunar spinel compounds

• Applicant: Dr. Peter Milde
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2016 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 310433647

Magnetic skyrmions are particle-like nanometer-sized spin textures that constitute a fascinating new variety of magnetic order in solid state materials. Due to their high potential for magnetic information storage, as well as their fundamental scientific appeal, the exploration of skyrmions has motivated a thriving research activity within the past few years.In the course of these studies, a lattice of skyrmions has been observed in various magnetic crystals, mostly metallic solids. Latest results demonstrated the existence of a so-called Néel-type skyrmion lattice within the novel class of lacunar spinel compounds. Intriguingly, it was found here that the skyrmions may magnetically induce an electric polarization, thus stimulating the prospect of an electric manipulation of skyrmions. Hence, we propose here to investigate these novel phenomena of magneto-electriccoupling in the lacunar spinel GaV4S8, and its related compounds, microscopically by means of various scanning probe techniques, such as magnetic force microscopy (MFM), Kelvin probe force microscopy (KPFM), piezo-response force microscopy and scanning near-field optical microscopy (SNOM) . We thus combine in this project our expertise in the field of microscopic imaging of magnetic textures (particularly, skyrmions), ferroelectric materials and optical near-field microscopy, as well as the strong experience of ourcooperation partners both in synthesizing these materials, and in theoretical understanding of the phenomena.In the first part of the project, we will implement the above mentioned methods for parallel and dynamic imaging of the polar electric and magnetic patterns that are created in GaV4S8 at cryogenic temperatures. Subsequently, we will use these imaging abilities to systematically study the complex entanglement of polar electric and magnetic order in this material using external stimuli, such as magnetic and electric fields. In the third part of the project we will broaden the scope beyond GaV 4 S 8 by searching for skyrmions and other non-collinear magnetic modulations in further lacunar spinel compounds.

• DFG Programme: Research Grants
• Co-Investigators: Professor Dr. Lukas M. Eng; Dr. Susanne Kehr