A possible chiral spin-liquid phase in non-centrosymmetric $R$BaCo${}_4$O${}_7$

Abstract

Based on a symmetry approach, we propose a possible explanation of the weak ferromagnetic component recently observed in YBaCo${}_3$FeO${}_7$ (Valldor et al. Phys Rev B, $84$ 224426 (2011)) and other isostructural compounds in the high-temperature spin-liquid phase. Due to the polar nature of their crystal structure, a coupling between time-odd scalar spin chirality which we suggest as the primary order parameter and macroscopic magnetization is possible as follows from the general form of the appropriate free-energy invariant. The deduced pseudoproper coupling between both physical quantities provides a unique possibility to study the critical behaviour of the chiral order parameter.