2005/03/31 by M. G. Pini, P. Politi, Paolo Politi +1 · 3 citations
Physics and Astronomy · #Magnetic properties of thin films #Physics of Superconductivity and Magnetism #Theoretical and Computational Physics #cond-mat.mtrl-sci
paper · pdf · doi:10.1103/physrevb.72.014454
published as Phys. Rev. B 72, 014454 (2005) (11 journal pages) · Final version accepted for publication in Physical Review B (with three figures)
openalex publication_date 2005/07/21 · arxiv created 2005/07/22 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
The field-driven reorientation transition of an anisotropic ferromagnetic monolayer is studied within the context of a finite-temperature Green's-function theory. The equilibrium state and the field dependence of the magnon energy gap E0 are calculated for static magnetic field H applied in plane along an easy or hard axis. In the latter case, the in-plane reorientation of the magnetization is shown to be continuous at T=0, in agreement with free-spin-wave theory, and discontinuous at finite temperature T>0, in contrast with the prediction of mean-field theory. The discontinuity in the orientation angle creates a jump in the magnon energy gap, and it is the reason why, for T>0, the energy does not go to zero at the reorientation field. approach. Above the Curie temperature TC, the magnon energy gap E0(H) vanishes for H=0 in both the easy and hard cases. As H is increased, the gap is found to increase almost linearly with H, but with different slopes depending on the field orientation. In particular, the slope is smaller when H is along the hard axis. Such a magnetic anisotropy of the spin-wave energies is shown to persist well above TC\phantom\rule0.3em0ex(T\ensuremath≈1.2TC).