Secondary phonon resonance scattering effect on the Ohrbach process of spin-lattice relaxation under phonon bottleneck conditions

Phonon bottle-neck conditions has been investigated experimentally and theoretically in the Ohrback process of spin-lattice relaxation (SLR) of Er3+ ions in LiYF4 monocrystals. Experiments were performed at 36.2 and 14.7 GHz frequencies in the temperature range T = 1.5 +- 20 K. Concentration, dimensional and orientation dependences of SLR time were investigated as well. The effect of the resonance increase in the relaxation rate under bottle-neck conditions for equality of splittings of basic and excited doublets of a paramagnetic ion in a magnetic field has been discovered. This effect was attributed to the mechanism of secondary phonon resonance scattering