Observation of Orbital Angular Momentum in the Chiral Magnet CrNb3S6 by Soft X-Ray Magnetic Circular Dichroism

The chiral magnet ${\mathrm{CrNb}}_{3}{\mathrm{S}}_{6}$ with its solitonic objects has novel magnetic and transport properties, in which the spin-orbit coupling (SOC) plays a central role. Aiming to address the possible existence of orbital moments driven by SOC, we perform soft x-ray magnetic circular dichroism spectroscopy at the Cr ${L}_{2,3}$ edges with in-plane magnetization. The dichroic signals provide direct experimental evidence that the Cr orbital magnetic moment is not quenched and is coupled antiparallel to the spin counterpart. Application of the orbital sum rule reveals that the magnitude of the Cr orbital moment is about 1% of the total magnetization. These findings are consistent with the first-principles electronic structure calculations that utilize the Cr $2p$ core radial function to define the Cr local $3d$ quantities. The distinct roles of the atomic SOC among the Cr $3d$ and Nb $4d$ states are discussed.