Comment on 'Spectra and energy levels of Er3+ (4f(11)) in NaBi(WO4)(2)' [J. Appl. Phys. 94, 7128 (2003)]

摘要

A recent article by Gruber [Gruber, J. Appl. Phys. 94, 7128 (2003)] reports the measurements of the optical absorption and photoluminescence spectra of Er3+ in NaBi(WO4)(2) (NBW) and the results of the interpretation and fitting of the observed crystal-field (CF) splitting of Er3+ multiplets with a quasicenter model. In the light of available, previously published information, we argued that these conclusions are not warranted. As a proof, the composition of the Er3+-NBW wave functions and the energy levels derived from the final obtained CF parameters have been checked through the simulation of the temperature-dependent paramagnetic susceptibility chi(m) according to the Van Vleck formalism and, unfortunately, experimental curves of chi(m) versus T, measured in parallel and perpendicular directions to the c axis of the NBW crystal, were not adequately reproduced. The same simulation was carried out with a set of free ions and CF parameters resulting from our previous polarized CF analysis of Er3+ in a NBW crystal, and the agreement with the measured chi(m) versus T curves is a clear indication of the validity and physical meaning of our earlier performed CF analysis. (C) 2004 American Institute of Physics.