Optical spectroscopy of the geometrically frustrated pyrochlore Ho2Ti2O7

Abstract Optical absorption and fluorescence spectra of Ho3+ in the geometrically frustrated pyrochlore Ho2Ti2O7 have been measured in the 27,000–4000 cm−1 spectral and 295–8 K temperature range. The energy positions of the Stark levels have been deduced. The Judd–Ofelt analysis has been performed by fitting the room temperature absorption spectra, and the calculated Judd–Ofelt parameters have been used to evaluate the Ho3+ radiative transition probabilities and the branching ratio. The obtained results show that although the lowest crystal field levels of Ho3+ in Ho2Ti2O7 are well separated, this separation (104 cm−1) is smaller than that previously suggested on the basis of neutron and magnetic studies (150–166 cm−1).