N. M. R. STUDIES OF Ni CONCENTRATED ALLOYS NEAR THE MAGNETIC CRITICAL CONCENTRATION

P. Panissod

In this paper we present new N. M. R. measurements in NicCu (Ccr ~ 46 %) and NicV (Ccr ~ 87.5 %) which show the importance of the environment effects in concentrated alloys near the paramagnetic-ferromagnetic transition. We show that in these two types of alloys the V and Cu properties are quite different from the different values of the critical concentration (Ccr) : namely, the V atoms (most probably isolated or paired in the Ccr range) are much more sensitive to the interactions with magnetic atoms than Cu atoms which have statistically about 5, 6 or 7 Cu nearest neighbours in the Ccr range. Particularly, the temperature dependences of the V51 Knight shift and line width are Curie Weiss like with a characteristic temperature close to the Curie temperature of the alloys ; on the contrary the characteristic temperature of the Curie Weiss temperature variations of the Cu properties is negative and is not related to the ordering temperature. We analyse such local environment effects in the NiV alloys by separating the contributions to the V51 N. M. R. line of the isolated V atom, of the isolated V pairs and of the V atoms embedded in larger V groups : the local susceptibility of a V atom is shown to decrease strongly when the number of V nearest neighbours increases.

Domaines: Articles anciens

P. Panissod. N. M. R. STUDIES OF Ni CONCENTRATED ALLOYS NEAR THE MAGNETIC CRITICAL CONCENTRATION. Journal de Physique Colloques, 1974, 35 (C4), pp.C4-173-C4-179. ⟨10.1051/jphyscol:1974430⟩. ⟨jpa-00215621⟩