Crystal-field effects in Er3+- and Yb3+-doped hexagonal NaYF4 nanoparticles

COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPSince the up-conversion phenomenon in rare-earths (REs) doped NaYF4 is strongly affected by the crystal electric field (CF), determining the CF parameters, wave functions, and scheme of the energy levels of the RE J multiplets could be crucial to improve and tune the up-conversion efficiency. In this work, the temperature and magnetic field dependent magnetization of NaY1-x[Er(Yb)](x)F-4 hexagonal nanoparticles (NPs) is reported. The data were best fit using the appropriated CF Hamiltonian for the J = 15/2 (J = 7/2) ground state multiplet of Er3+ (Yb3+) ions. The B-2(0), B-4(0), B-6(0), and B-6(6) CF parameters were considered in the Hamiltonian for RE ions located at the hexagonal C-3h point symmetry site of the NaYF4 host lattice. These results allowed us to predict an overall CF splitting of similar to 214 (similar to 356 K) for Er3+ (Yb3+) and the wave functions and their energy levels for the J = 15/2 (J = 7/2) ground state multiplet which are in good agreement with the low temperature electron spin resonance experiments. Besides, our measurements allowed us to calculate all the excited CF J multiplets that yield to a good estimation of the up-conversion light emission linewidth. The nonlinear optical light emission of the studied NaY1-x[Er(Yb)](x)F-4 hexagonal NPs was also compared with the most efficient up-conversion codoped NaY1-x-yErxYbyF4 hexagonal NPs.961617COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPSem informaçãoSem informação2011/19924-22012/04870-72012/05903-62015/23882-4This work was supported and performed under the auspices of the Brazilian agencies CAPES, CNPq, and FAPESP through Grants No. 2011/19924-2, No. 2012/04870-7, No. 2012/05903-6, and No. 2015/23882-4. The SEM data were acquired in the LNNano at the Centro Nacional de Pesquisa em Energia e Materiais (CNPEM) in Campinas-SP, Brazil. D.J.G. acknowledges support from FONCyT (PICT 2012-1069)