Low-temperature anomalies of the dynamics of a paramagnetic crystal resonator
Almas F. Sadreev
The dynamics of a paramagnetic system (S = 1/2), thermodynamically equilibrium-linked with the radiation field of a resonator is considered by the methods of the quantum theory of fields. The spectrum of the resonance frequencies of the system is found for two relations of the size of the paramagnetic sample L and the wavelengths of the radiation field k−1. It is shown that when L ≪ k−1 Fain’s result, Eq. (1), is valid for the intrinsic line width, if the Zeeman frequency ω0 ≫ck. With L ≳ k−1, (the case of a crystal resonator), and kT>ω0>ρSμB2 (ρS is the paramagnetic ion density in the crystal), the temperature behavior of the intrinsic width is described by formula (33). It is shown that the critical temperature Tc is the temperature of the Bose-Einstein condensation of photons of the resonator radiation field, which is determined only by the paramagnetic ion density in the sample. Estimates are made of the intrinsic broadening of the Zeeman line in certain paramagnetic crystal resonators with impurities of rare-earth ions.
Soviet Journal of Low Temperature Physics•Aug 1, 1979•0 citations