Paramagnetic resonance of Ho3+ in a trigonal site in SrF2

A paramagnetic-resonance spectrum of Ho3+ in a trigonal site in SrF2 was observed. The spectrum is characteristic of a non-Kramers ion, and the asymmetric line shape indicates that the non-Kramers ground doublet requires low-symmetry strain distortions to split the doublet and observe paramagnetic-resonance transitions of the magnetic dipole type. The spectrum is interpreted in terms of a standard spin Hamiltonian for a non-Kramers doublet with the parameters g=18.2±0.1, Δ0=0.033±0.001 cm-1, |A|=0.397±0.005 cm-1. The possibility of observing paraelectric resonance in this site, which lacks inversion symmetry, was investigated. A discussion of various possible eigenfunctions, transitions, and line shapes in crystal fields of threefold and fourfold symmetry is given. © 1969 The American Physical Society.