Itinerant electron magnetism NMR and magnetization studies in Y(Co1-xAlx)3

The YCo3 system is characterized by a band structure which results in a magnetic instability of the itinerant subsystem. In such a case, the Co magnetism presents metamagnetic transitions upon application of an external magnetic field in the megagauss range. In the present paper we investigate the effect of substituting Co by Al in YCo3. Polycrystalline samples of Y(Co1-xAlx)3 (x=0.00, 0.03, 0.05, 0.07 and 0.10), in the Co-rich site were investigated by means of magnetization M(H), AC susceptibility χAC(T) and nuclear magnetic resonance (NMR). The spontaneous magnetization as a function of Al concentration presents an anomalous behavior, which is closely related to N(EF,x), passing through a maximum at x=0.05, followed by a sharp decrease up to x=0.10. We show that the system becomes a very weak itinerant ferromagnet (VWIF) at x=0.10. NMR results show change in the 59Co hyperfine field value upon Al alloying, which is related to changes in the conduction electrons density. An increase in the number of lines, with respect to YCo3, attributed to the 27Al nucleus, was also verified