Phonon spectrum, electron spin–lattice relaxation and spin–phonon coupling of Cu2+ ions in BaF2 crystal

Electron spin relaxation rate governed by Raman process reflects crystal phonon spectrum allowing calculation of the spin–phonon coupling. Debye-type phonon spectrum is a rough approximation. [Display omitted] •Raman processes dominate in the spin–lattice relaxation.•The relaxation rate theory suitable for using real phonon spectra is presented.•Perfect description of relaxation is obtained with real phonon spectrum.•The spin–phonon coupling parameter is 1362cm−1. Electron spin–lattice relaxation rate is determined by electron spin echo method in temperature range 4–60K. The Raman relaxation processes dominate and its theory is outlined in a form suitable for calculations of relaxation rate using real phonon spectrum. A few approximations have been considered: when phonon spectrum and Debye temperature are not available; when Debye temperature is available but phonon spectrum is not; and when spin–phonon coupling is known. All these approximations use the Debye model of phonons and give a non-satisfactory description the temperature dependence of the relaxation rate. A perfect description of experimental results is obtained when real phonon spectrum is considered. The value of the spin–phonon coupling parameter was determined as G=〈a|V|b〉=1362cm-1. This value is discussed by a comparison with G-values published for various ions and crystals.