Magnetic structures

Publication date: Available online 26 July 2019Source: Comptes Rendus PhysiqueAuthor(s): Juan Rodríguez-Carvajal, Jacques VillainAbstractWhile ferromagnetism has been known since many centuries, more complex magnetic structures have only been identified in the twentieth century: ferrimagnetism, antiferromagnetism, helimagnetism, modulated structures… Incommensurable or long-period structures have first been deduced as consequences of phenomenological models, e.g., the Heisenberg Hamiltonian. The more fundamental explanation of Rudermann, Kittel, Kasuya, and Yoshida relies on the general phenomenon of Friedel oscillations. The coexistence of crystallographic order and magnetic order is sometimes antagonistic and results in sequences of transitions that may be continuous or not. The most effective experimental technique to observe magnetic order is neutron diffraction, but the analysis is sometimes very complicated and requires sophisticated numerical methods involving group theory. In the case of incommensurable structures, it may be useful to consider the three-dimensional system as the section of a higher-dimensional crystal. The determination of magnetic structures from neutron scattering data is facilitated by computers and adequate programs.RésuméAlors que le ferromagnétisme est connu depuis des siècles, ce n'est qu'au vingtième siècle qu'on identifia des structures magnétiques plus complexes, comme le ferrimagnétisme, l'antiferromagnétisme, l'hélimagnétisme...

Source: Comptes Rendus Physique - July 28, 2019 Category: Physics Source Type: research