ESR Study of Fe³⁺ Ions Doped in KDP Crystal

The ESR spectra of Fe 3+ ion doped in KDP crystal were measured. From the angular dependence of the spectra, the spin Hamiltonian parameters were determined in the paraelectric phase. The g tensor was isotropic within the experimental error. The principle values of D tensor were determined to be D X =526, D Y =-481, D Z =-45 in Gauss. From the Principle axes of D tensor, it was concluded that the FE 3+ ion was doped in the K + ion site, and a site of a hydrogen near the Fe 3+ ion was vacant. Each line in the Spectra splits into two below the Curie temperature. One of the splitting lines became broad and weak on cooling. This peculiar temperature dependence of the lines was explained qualitatively by considering the jumping of a proton vacancy.