Based on a symmetry approach, we propose a possible explanation of the weak ferromagnetic component recently observed in YBaCo3FeO7 (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.
@article{arxiv.1204.2168,
title = {A possible chiral spin-liquid phase in non-centrosymmetric $R$BaCo$_4$O$_7$},
author = {D. D. Khalyavin and P. Manuel and L. C. Chapon},
journal= {arXiv preprint arXiv:1204.2168},
year = {2015}
}