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 mag netic instability of the itinerant subsystem. In such a case, the Co magnet ism presents metamagnetic transitions upon application of an external magne tic field in the megagauss range. In the present paper we investigate the e ffect of substituting Co by Al in YCo3. Polycrystalline samples Of Y(Co1-xA lx)(3) (x = 0.00, 0.03, 0.05, 0.07 and 0.10), in the Co-rich site were inve stigated by means of magnetization M(H), AC susceptibility chi (AC)(T) and nuclear magnetic resonance (NMR), The spontaneous magnetization as a functi on of Al concentration presents an anomalous behavior, which is closely rel ated to N(E-F,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 itiner ant ferromagnet (VWIF) at x = 0.10. NMR results show change in the Co-59 hy perfine field value upon Al alloying, which is related to changes in the co nduction electrons density. An increase in the number of lines, with respec t to YCo3, attributed to the Al-27 nucleus, was also verified. (C) 2001 Els evier Science B.V. All rights reserved.