A study was made of the Er3+ electron spin resonance spectra of garnet monocrystals which were doped with Cr3+. It was shown that there was a dependence of the spectra upon temperature, between 4.2 and 30K, in which the broadening of the Cr3+ resonances was attributed to Cr-Er interactions. The principal g-values for Er3+ were obtained by fitting the spectra to Lorentzian lines.

I.J.Moraes, R.R.De Souza, O.R.Do Nascimento, M.C.Terrile, G.E.Barberis: Solid State Communications, 1995, 95[4], 251-4