Possible chiral spin-liquid phase in noncentrosymmetric RBaCo4O7

Based on a symmetry approach, we propose a possible explanation of the weak ferromagnetic component recently observed in YBaCo3FeO7 [M. 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 behavior of the chiral order parameter.