Submillimeter EPR spectroscopy of Van Vleck paramagnets holmium nicotinate dihydrate and KY3F10:Ho

Abstract

Results of EPR measurements of the Van Vleck paramagnets (monoclinic holmium nicotinate dihydrate and activated cubic complex fluoride KY3F10:Ho3+) are presented. Spectra were taken with a wide-band spectrometer operating in the frequency range 65-535 GHz at liquid helium temperature for magnetic fields up to 1 T. Transformations of the hyperfine structure of the EPR spectra with the frequency of the radiation and the directions of the constant and alternating magnetic fields have been studied and compared with results of calculations based on a diagonalization of the complete electronic-nuclear Hamiltonian. Crystal field splittings between the ground and first excited singlets of 7.3 cm-1 in holmium nicotinate and 5.8 cm-1 in KY3F10:Ho have been estimated using extrapolations of the resonance frequency dependences on magnetic field to zero field strength.