In-plane dipole coupling anisotropy of a square ferromagnetic Heisenberg monolayer

Abstract

In this study we calculate the dipole-coupling-induced quartic in-plane anisotropy of a square ferromagnetic Heisenberg monolayer. This anisotropy increases with an increasing temperature, reaching its maximum value close to the Curie temperature of the system. At T=0 the system is isotropic, besides a small remaining anisotropy due to the zero-point motion of quantum mechanical spins. The reason for the dipole-coupling-induced anisotropy is the disturbance of the square spin lattice due to thermal fluctuations ('order-by-disorder' effect). For usual ferromagnets its strength is small as compared to other anisotropic contributions, and decreases by application of an external magnetic field. The results are obtained from a Heisenberg Hamiltonian by application of a mean field approach for a spin cluster, as well as from a many-body Green's function theory within the Tyablikov-decoupling (RPA).

6 pages, 2 figures, accepted for publication in RPB

References in corpus (2)

• Field-induced magnetic reorientation and effective anisotropy of a ferromagnetic monolayer within spin wave theory
• 'Theory for the enhanced induced magnetization in coupled magnetic trilayers in the presence of spin fluctuations'

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