Mechanism of temperature dependence of the magnetic anisotropy energy in   ultrathin Cobalt and Nickel films
  Temperature dependent FMR-measurements of Ni and Co films are analysed using a microscopic theory for ultrathin metallic systems. The mechanism governing the temperature dependence of the magnetic anisotropy energy is identified and discussed. It is reduced with increasing temperature. This behavior is found to be solely caused by magnon excitations. 
J. Kienert, S. Schwieger, K. Lenz, J. Lindner, K. Baberschke, and W.   Nolting