Point-defect production in the h.c.p. heavy-rare-earth metals Gd, Tb, Dy, Ho, Er, Tm and Lu during electron irradiation at low temperatures

Abstract

Defect production in the h.c.p. heavy lanthanides Gd, Tb, Dy, Ho, Er, Tm and Lu has been investigated by electron irradiation in the energy range 0.7–1.7 MeV, at liquid-helium temperatures. Fitting with displacement cross-sections yielded minimum threshold energies for displacement, T _d1 = 14.0 to 17.3 eV, which exhibit the same dependence on the atomic number Z as the reduced reciprocal interatomic distance (c/a)l1.633r ₁. A correlation with the sizes of the interatomic ‘lenses’ via the replacement-collision mechanism is suggested. The electrical resistivity increase due to a Frenkel pair is shown to depend both on the phonon resistivity and on the magnetic resistivity of the metal, in the form ρ _F ∼ 270ρ _ph + 100ρ_mag at room temperature, implying the introduction of additional spin disorder around a defect.