Helical spin structure in the langasite family multiferroic Ba3TaFe3Si2O14, determined by Mössbauer spectroscopyI. S. Lyubutin, M. A. Chuev, S. S. Starchikov, K. O. Funtov and I. Yu. StarchikovaEPL, 128 6 (2019) 67005DOI: https://doi.org/10.1209/0295-5075/128/67005