The physical properties of two chiral systems with localized and delocalized magnetic moments, Cu₂OSeO₃ and MnSi, are reviewed. It is concluded that the longitudinal fluctuations of magnetic moments affect little the qualitative picture of phase transitions and the magnetic phase diagrams of chiral systems.

Keywords: chiral magnetic systems, phase transitions, longitudinal fluctuations of the magnetic moment PACS: 75.10.−b, 75.10.Lp, 75.30.Kz (all) DOI: 10.3367/UFNe.2016.04.037781 URL: https://ufn.ru/en/articles/2016/9/c/ 000391228000003 2-s2.0-85006154135 2016PhyU...59..866S Citation: Stishov S M "Notes on phase transitions and the role of spin fluctuations" Phys. Usp. 59 866–868 (2016) BibTexBibNote ® (generic)BibNote ® (RIS)MedlineRefWorks Received: 29th, December 2015, revised: 8th, March 2016, accepted: 12th, April 2016 Оригинал: Стишов С М «Заметки о фазовых переходах и роли спиновых флуктуаций» УФН 186 953–956 (2016); DOI: 10.3367/UFNr.2016.04.037781