Role of Antisymmetric Exchange in Selecting Magnetic Chirality inBa3NbFe3Si2O14

We present an electron spin resonance (ESR) investigation of the acentric ${\mathrm{Ba}}_{3}\mathrm{Nb}{\mathrm{Fe}}_{3}{\mathrm{Si}}_{2}{\mathrm{O}}_{14}$, featuring a unique single-domain double-chiral magnetic ground state. Combining simulations of the ESR linewidth anisotropy and the antiferromagnetic-resonance modes allows us to single out the Dzyaloshinsky-Moriya (DM) interaction as the leading magnetic anisotropy term. We demonstrate that the rather minute out-of-plane DM component ${d}_{c}=45\text{ }\text{ }\mathrm{mK}$ is responsible for selecting a unique ground state, which endures thermal fluctuations up to astonishingly high temperatures.