Effect of oxygen nonstoichiometry on magnetic phase transitions in frustrated cobaltites YBaCo4O7+x (x = 0, 0.1, 0.2)Zoya Kazei, Vyacheslav Snegirev, Ludmila Kozeeva, Margarita Kameneva and Alexander LavrovEPJ Web Conf., 185 (2018) 06004DOI: https://doi.org/10.1051/epjconf/201818506004