On the theory of Bose-Einstein condensation of quasiparticles: on the possibility of condensation of magnons at high temperatures

摘要

Bose condensation of quasiparticles in physical systems of finite size izconsidered for the case of ferromagnetic thin films. It is shown that inaccordance with present-day experimental capabilities which permit one toachieve densities of long-wave spin excitation of 1018-1019 cm-3, in such filmsthe formation of condensate of such quasiparticles begins at temperatures T~100K (room one including). It is found that Bose condensation is accompanied byscaling phenomenon according to which the main thermodynamic variable is notthe number N of particles but the ratio N/T. This indicates that condensationof magnons can be observed at relatively low magnon densities. The roles playedby the shape of the spectrum and film thickness are analyzed.