Structural and Magnetic Chirality of Cu2OSeO3

Abstract

We determine the chirality of the magnetic and crystal structures, respectively, for the magnetoelectric insulator Cu2OSeO3using small-angle diffraction of polarized neutrons and resonant contribution to X-ray single crystal diffraction of synchrotron radiation. This compound crystallizes in the P213 space group similar to other chiral but metallic magnets, such as MnSi, MnGe, MnSi1+xGex, Fe1+xCoxSi, Mn1+xFexSi, Mn1+xCoxSi, FeGe, Mn1+xFexGe. It has recently been shown that the structural and magnetic chiralities for metallic helimagnets are linked to each other [1], also in the so-called skyrmion phase [2]. Here we measure the spin chirality by comparing neutron scattering maps from Cu2OSeO3with the reference MnSi, which has left-handed magnetic spiral and absolute crystal structure denoted as left-handed [1]. Similar to the reference MnSi system, the crystallographic chirality of Cu2OSeO3is fixed on the basis of absolute structure determination taking into account the refinement of the Flack parameter. We find that the crystal and magnetic structures of Cu2OSeO3have the same chirality. The similar relationship is found for MnSi, Mn1+xFexSi, MnGe, while FeGe and Fe1+xCoxSi always show the opposite chiral correlation between magnetic and crystal structures. Notably, the relationship between two chiralities for Cu2OSeO3found in the experiment is opposite to that proposed from recent theoretical calculations [3], thus calling for a revision of the theory of possible microscopic mechanisms contributing to the phenomenological antisymmetric magneto-lattice coupling.