Estudo do efeito da substituição quimica nas propriedades de compostos intermetalicos de Yb e U

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

In the present work we studied the effect of the chemical substitution on the properties of Yb and U systems through the series Yl-xYbxCuAl, YbNi1-xCuxAl, YbInNi4-xCux, Y1-xYbxInNi4, U(Gel-xSnx)2, U(Gel-xNix)2 e Yl-xUxGe2. The results of resistivity, speci:fic heat and magnetization showed that the chemical substitution leads to modi:fication on the ground state of the system due to changes of the exchange parameter J. Using the results for the series Yl-xYbxCuAl and Yl-xYbxInNi4 we showed that the Kondo temperature decreases for the magnetic systems when the dilution process induces expansion of the volume, but increases for the case of non magnetic systems. Furthermore, substitutions of the transition metal showed a possible influence of changes in band structure on the behavior of Tk. The study of the series YbInNi4-xCux e Yl-xYbxInNi4 revealed a doublet-doublet-quartet crystal field level scheme for the YbInNi4, and hopefully this result will contribute to clarity the existing controversy about this matter. The chemical substitution effect of Ge in the ferromagnetic compound UGe2 has been studied with the series U(Ge1-xSnx)2 and U(Ge1-xNix)2, showing changes of the magnetic properties with dilution. Evidences for a Spin Glass (SG) state was found for the Ni alloying, and from this we concluded that the competition between ferromagnetic and antiferromagnetic ordering is a necessary but not sufficiently condition for the SG. Also others effects, as changes on the hybridization and crystallization of different phases with Ni dilution should be taken into account. The substitution of (U) by Y in the series Y1-xUxGe2 leads to a different magnetic state with non Fermi liquid characteristics near to the QCP

ASSUNTO(S)

kondo vidros de spin efeito

ACESSO AO ARTIGO

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