Several recent examples are used to demonstrate that Raman and infrared spectroscopy can be successfully used as a novel experimental tool to study microscopic processes involving 4f electrons in rare earth (RE) cuprates. Raman-active crystal field (CF) excitations in <$E roman {Nd sub 2 CuO sub 4}> were measured under hydrostatic pressure up to ~ 7 GPa. The observed pressure-induced shifts of the CF levels were interpreted using density-functional-theory-based ab initio calculations and the superposition model. An infrared transmission study of the <$E nothing sup 4 I sub J>, J = 9/2, 11/2, 13/2 multiplets of <$E roman Nd sup 3+> in <$E roman {Nd sub 2 CuO sub 4}> reveals a splitting of the Kramers doublets of the order of a few <$E roman cm sup -1> due to the Nd-Cu exchange interaction. This study shows that these splittings can be described by an effective anisotropic exchange Hamiltonian for the <$E roman Nd sup 3+> ion expressed in terms of spherical tensor operators up to the sixth order. The isotropic term in the exchange Hamiltonian vanishes for symmetry reasons in this case. An analysis of the infrared transmission spectra in <$E {roman RE} sub {1~+~x} {roman Ba} sub {2~-~x} {roman Cu sub 3 O} sub {6~+~delta}> (RE = Nd, Sm) up to ~ 10 000 <$E roman cm sup -1> indicates that, besides the regular sites, the RE ions also occupy Ba sites, even in the samples with the cation stoichiometry 1-2-3.

Індекс рубрикатора НБУВ: В374.7

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Спектроскопія твердих тіл

Шифр НБУВ: Ж14063 Пошук видання у каталогах НБУВ 

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