DEFECT ANNEALING IN THE HEXAGONAL CLOSE PACKED HEAVY RARE-EARTH METALS GD, TB, DY, HO, ER, TM AND LU AFTER ELECTRON-IRRADIATION AT LOW-TEMPERATURES

The recovery spectra of the heavy rare earths Gd, Tb, Dy, Ho, Er and Tm were determined after irradiation with electrons at low temperatures. In the cases of Er and Tm, strong thermal cycling phenomena were observed and attributed to hydrogen atoms changing configurations and interacting with the magnetic structure of the metal. After elimination of these effects in Er and Tm, all the spectra - together with those of the earlier treated Lu - had rather similar form: several close-pair peaks followed by a broad complex substage resembling the stage I//D in f. c. c. metals and attributed to long-range interstitial migration. A correlation is found between the temperature of the maximum of this substage (normalized to the melting temperature) and the c/a-ratio of the metals.