Energy Levels of Er3+ in Three Rare Earth Hydroxides

Abstract

Energy levels of Er3+ in three compounds: Er(OH)3, 1% Er3+:Y(OH)3, and 1% Er3+:Tb(OH)3 have been determined from optical absorption experiments on single crystals at 77 and 1.3°K and from far infrared absorption experiments at 1.3°K. For each material, the four crystal field parameters which specify the crystal field for f electrons at a site of C3h symmetry were found by a least squares analysis including intermediate coupling and the J-mixing effects of the crystal field. The results for Er(OH)3 are typical: the 37 measured levels were fitted with a mean deviation of 3.2 cm−1 with the best parameters being: B20=192 cm−1, B40=−64 cm−1, B60=−40 cm−1, and B66=521 cm−1. The parallel Zeeman effect of the Er3+ energy levels was also studied in fields up to 38 kilogauss for two of the compounds, Er3+:Y(OH)3 and Er3+:Tb(OH)3, and good agreement was found between the calculated and observed splitting factors and with the results for Er3+:Y(OH)3 from previous electron spin resonance experiments. The spontaneous splittings of the Er3+ doublet levels in ferromagnetically ordered Tb(OH)3 have also been determined, and analysis of these splittings has indicated the presence of nondipolar interactions between the Er3+ and Tb3+ ions.