Abstract:

The sample of La_0.67Ca_0.33MnO₃ was prepared by a conventional solid state reaction method. The electron spin resonance behavior of La_0.67Ca_0.33MnO₃ was studied experimentally. The variations of electron spin resonance linewidth were investigated by spin wave theory. A self\|consistent calculation of spin wave energy was carried out in the regime of renormalization group theory, and a renormalization factor           {1-e(T)/S} was obtained to correct the temperature dependent spin wave energy. It shows that the spin wave frequency is softened with the increase of the temperature, leading to an unstable state. Therefore, the reason of the disappearance of spin wave energy at the critical temperature is well understood theoretically. We theoretically validate the conclusion that the decrease of the electron spin resonance line\|width with temperature increase is the  result of the decrease of the number of the spin wave coupling modes.

Key words: La_0.67Ca_0.33MnO₃, electron spin resonance linewidth, spin wave theory