Abstract
Complex low-temperature-ordered states in chiral magnets are typically governed by a competition between multiple magnetic interactions. The chiral-lattice multiferroic Cu2OSeO3 became the first insulating helimagnetic material in which a long-range order of topologically stable spin vortices known as skyrmions was established. Here we employ state-of-the-art inelastic neutron scattering to comprehend the full three-dimensional spin-excitation spectrum of Cu2OSeO3 over a broad range of energies. Distinct types of high- and low-energy dispersive magnon modes separated by an extensive energy gap are observed in excellent agreement with the previously suggested microscopic theory based on a model of entangled Cu4 tetrahedra. The comparison of our neutron spectroscopy data with model spin-dynamical calculations based on these theoretical proposals enables an accurate quantitative verification of the fundamental magnetic interactions in Cu2OSeO3 that are essential for understanding its abundant low-temperature magnetically ordered phases.
Highlights
Complex low-temperature-ordered states in chiral magnets are typically governed by a competition between multiple magnetic interactions
It was shown soon afterwards that this skyrmion lattice can be manipulated by the application of either magnetic9 or electric10 field, and more recently by chemical doping11, which indicates a delicate balance of the magnetic exchange and DM interactions with the spin anisotropy effects
The cubic copper(II)-oxoselenite Cu2OSeO3 crystallizes in a complex chiral structure with 16 formula units per unit cell19
Summary
Complex low-temperature-ordered states in chiral magnets are typically governed by a competition between multiple magnetic interactions. The chiral-lattice multiferroic Cu2OSeO3 became the first insulating helimagnetic material in which a long-range order of topologically stable spin vortices known as skyrmions was established. We employ state-of-the-art inelastic neutron scattering to comprehend the full three-dimensional spin-excitation spectrum of Cu2OSeO3 over a broad range of energies. The comparison of our neutron spectroscopy data with model spin-dynamical calculations based on these theoretical proposals enables an accurate quantitative verification of the fundamental magnetic interactions in Cu2OSeO3 that are essential for understanding its abundant low-temperature magnetically ordered phases. The interest in the multiferroic ferrimagnet Cu2OSeO3 with a chiral crystal structure has been intensified in recent years after the discovery of a skyrmion-lattice phase in this system, making it the first known insulator that exhibits a skyrmion order. Understanding the complex magnetic phase diagram of Cu2OSeO3 requires detailed knowledge of the spin Hamiltonian with precise quantitative estimates of all interaction parameters, which can be obtained from measurements of the spin-excitation spectrum
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