Electron paramagnetic resonance spectroscopy of Cr3+from the growth bands of potassium dihydrogen phosphate

Samples taken from the growth band region of a KDP:Cr crystal have been studied by EPR spectroscopy at room temperature. The observed lines are consistent with a centre in which Cr 2+ substitutes for K + with two proton vacancies in nearest positions. From the powder spectrum and the angular variation of the resonance fields the defect principal axes and the spin-Hamiltonian parameters have been calculated. The experimental spectra, the angular variation and the parameters obtained resemble those from samples taken from regions out of the growth bands. The differences between Cr 3+ spectra in both types of sample are attributed to variations in the crystal-field strength produced by changes in the lattice parameters.