Speaker
Description
As they often stabilize with complex non-collinear magnetic structures, frustrated magnets are potential candidates for type-II multiferroism, where both magnetic and electric orders appear at the same temperature and are strongly coupled [1]. In these materials, the proper understanding of the coupling between spin and charge degrees of freedom is a key to identify the microscopic mechanism at the origin of the multiferroic properties [2]. Here we focus on the normal cubic spinel GeFe2O4, crystallizing in the Fd-3m space group. In this compound, the Fe magnetic ions form a pyrochlore sublattice, consisting of a network of corner-sharing tetrahedra prone to magnetic frustration [3]. In this talk I will present our recent study combining experiments (single-crystal neutron diffraction and inelastic neutron scattering) with meticulous modeling of the experimental data. I will show how this complementary approach has been successful to evidence, in this system, a non-coplanar spin texture described by a combination of 6 symmetry-equivalent propagation vectors [4]. We will also see how this complex multi-q magnetic order plays a crucial role in the emergence of ferroelectric properties recently observed at the magnetic transition temperature [5].
[1] D. Khomskii, Physics 2, 20 (2009).
[2] H. Katsura et al., Phys. Rev. Lett. 95, 057205 (2005); I. A. Sergienko & E. Dagotto, Phys. Rev. B 73, 094434 (2006).
[3] M. D. Welch et al., Mineral. mag. 65, 441–444 (2001).
[4] L. Chaix et al., to be submitted to Phys. Rev. Lett.
[5] E. Chan et al., in preparation.
