The electron spin resonance study of Gd3+ in natural zircon

X-band ESR spectra of natural zircon were measured at room temperature with the applied magnetic field parallel and perpendicular to the crystal axis [0 0 1]. Seven resonance absorption peaks of Zeeman interaction are obtained, due to a trace of the Gd3+ present in the natural zircon. The ground state of Gd3+, 8S7/2 give rise to seven resonance absorption peaks under an applied magnetic field. In addition, the weak hyperfine structure lines are observed between adjacent Zeeman lines, due to isotope 157Gd3+ and 155Gd3+. The ESR spectra were also measured at the different rotation angle θ and φ from 0 to 180° with respect to the applied magnetic field. The angular variation of ESR spectra of Gd3+ with the applied magnetic field clearly reflected that the crystal field symmetry of the surrounding of Gd3+ is D2d, and hence Gd3+ substituted Zr4+ in the lattice. According to the crystal field, it was shown that the ground state energy level of the Gd3+was split into four doublets.