Microscopic observation of the metamagnetic transition in intermetallic compounds Y1-xNdxCo3 and Y1-xGdxCo3: a Co-59 NMR study

We have performed Co-59 NMR measurements to study the metamagnetic transiti on at 4.2 K in intermetallic compounds Y1 - xNdxCo3 (0 less than or equal t o x less than or equal to 1) and Y1 - xGdxCo3 (0 less than or equal to x le ss than or equal to 0.32). We observed Co-59 NMR signals coming from the th ree nonequivalent Co sites and found from an analysis of the NMR spectra th at successive metamagnetic transitions were induced by the exchange field o f the Nd and Gd magnetic moments without an external magnetic field. The Co magnetic moments at the 3b and 6c (18h) sites undergo the metamagnetic tra nsition around x = 0.35 (0.85) in Y1 - xNdxCo3 at 4.2 K in zero external fi eld. On the other hand, metamagnetic transitions of Co magnetic moments at the three sites take place around x = 0.25 in Y1 - xGdxCo3. The exchange co nstants between the Co spins at the three Co sites and the R (R = Nd and Gd ) spins are estimated for both systems. (C) 1998 Elsevier Science B.V. All rights reserved.