Antiferromagnetic Resonance Absorption

Abstract

The line widths of antiferromagnetic resonance absorption in the vicinity of the Neél point are investigated by the use of a method of relaxation function similar to that employed by the present authors in studying the dynamical behavior of ferromagnetic spins. Above the Neél point, the line width of the high frequency mode is shown to increase rapidly when the temperature approaches the Neél point, being proportional to (T-TN)−3/4 in the vicinity of this point. This anomalous increase is due to the critical fluctuation of spins and is in agreement with the observation on MnF2. Below the Neél point, the situation is more complicated and the effects of the anomalous fluctuation upon the line widths are discussed.