AMORPHIZATION OF RARE EARTH-COBALT INTERMETALLIC ALLOYS BY SWIFT HEAVY-ION IRRADIATION

RCo(2) (R = Y, Ce and Tm) and RCo(3) (R = Y and Ce) intermetallic comp ounds have been irradiated for the first time by swift heavy-ion beams (U, Pb) of energy 1-5 GeV at GANIL (Caen, France). The compounds YCo2 , CeCo3 and YCo3 are found to be partially amorphized after irradiatio n. The amorphized volume fraction has been determined as a function of the ion beam fluence by x-ray diffraction and magnetic measurements. Results are found to be in agreement. By means of a phenomenological m odel, associating the phenomena of amorphization and recrystallization , the diameters of the latent trades are estimated to lie in the range 2-3 nm. In contrast, no amorphization is observed in CeCo2 and TmCo2. The different behaviours observed are well understood, in the framewo rk of the thermal spike model, in terms of the different values of the electron-phonon coupling constant of the irradiated compounds.