Anisotropic interactions in magnetic crystals with S-state ions. Nanostructures

Anisotropy mechanisms in compounds with S-state ions are discussed, including the 'single-ion' exchange mechanism that was developed theoretically by Nikiforov and coworkers based on the two-ion model and which has only recently received detailed experimental study. Results demonstrating the significant role of the 'single-ion' source are presented. An independent generalized method for quantitatively describing and predicting the anisotropy of magnetically ordered crystals is discussed, and its potential for the investigation of the BiFeO3 multiferroic in the region of the existence of a spin cycloid is examined. The anisotropic interactions responsible for the formation of nanostructures in the form of spin vortices (skyrmions) in MnSi and Cu2OSeO3 are analyzed.