Ressonancia paramagnetica eletronica do ion Gd3+, em hidretos metalicos do tipo fase de laves AB2Hx

AUTOR(ES)
DATA DE PUBLICAÇÃO

1988

RESUMO

The ternary intermetallic hydrides LaRu2Hx, CeRu2Hx, YRh2Hx and YNi2Hx, doped with Gd3+ ions, were investigated in function of both the hydrogen concentration, x, and temperature. A single EPR line was observed for Gd in the uncharged LaRu2 compound (x = O) in the normal state. The EPR parameters were found in good agreement with the previously published data. Two well resolved Gd3+ EPR lines were found in the region of intermediate hydrogen concentration (0.5 £ x £ 3), while a single line with g-value (g = 2.087) was observed for high hydrogen concentration (x @ 4.5). Our results clearly indicate that LaRu2Hx is a double-phase hydride with a low hydrogen concentration phase, a-phase, and a high hydrogen concentration, b-phase. Both phases coexist for intermediate hydrogen concentration (0.5 £ x £ 4.5). CeRu2 is a superconducting compound with transition temperature Ts = 6.18 K. The hydrogen absorption leads to a suppression of de superconducting behavior and appearance of a magnetic ordering transition at T = 1.3 K. These effects were explained in terms of a change in cerium valence of Ce@4+ (4f0) in the CeRu2 for C3+ (4f1) in the CeRu2H5. Only moderate effects on the EPR properties of YRh2 and YNi2 were observed upon hydrogen absorption. The analysis and discussion of our results were performed in terms of the multiband model for EPR of rare earth impurities in metal and the rigid band (protonic and anionic) model for hydrogen absorption in metallic systems. Some aspect of the band structure theory were useful for the understanding of the changes introduced by hydrogen on the physical properties of intermetallic compounds investigated here

ASSUNTO(S)

ressonancia paramagnetica eletronica hidretos

ACESSO AO ARTIGO

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