2019/12/05 by Irina V. Tyulkina, Denis S. Goldobin, Lyudmila S. Klimenko +2
Engineering · Materials Science · Physics and Astronomy · #Antiferromagnetism #Characterization and Applications of Magnetic Nanoparticles #Ferromagnetism #Magnetic field #Magnetic structure #Magnetization #Material Dynamics and Properties #Metastability #Phase diagram #Phase transition #Square lattice #Superparamagnetism #Theoretical and Computational Physics #cond-mat.stat-mech
paper · pdf · doi:10.1098/rsta.2019.0259
18 pages, 3 figures
arxiv created 2019/12/05 · openalex created_date 2019/12/13 · openalex publication_date 2020/04/12 · arxiv updated 2021/03/17 · openalex updated_date 2026/08/05
The problem of magnetic transitions between the low-temperature (macrospin ordered) phases in two-dimensional XY arrays is addressed. The system is modelled as a plane structure of identical single-domain particles arranged in a square lattice and coupled by the magnetic dipole–dipole interaction; all the particles possess a strong easy-plane magnetic anisotropy. The basic state of the system in the considered temperature range is an antiferromagnetic (AF) stripe structure, where the macrospins (particle magnetic moments) are still involved in thermofluctuational motion: the superparamagnetic blocking T b temperature is lower than that ( T af ) of the AF transition. The description is based on the stochastic equations governing the dynamics of individual magnetic moments, where the interparticle interaction is added in the mean-field approximation. With the technique of a generalized Ott–Antonsen theory, the dynamics equations for the order parameters (including the macroscopic magnetization and the AF order parameter) and the partition function of the system are rigorously obtained and analysed. We show that inside the temperature interval of existence of the AF phase, a static external field tilted to the plane of the array is able to induce first-order phase transitions from AF to ferromagnetic state; the phase diagrams displaying stable and metastable regions of the system are presented. This article is part of the theme issue ‘Patterns in soft and biological matters’.