The Spectrum of the Magnetic Aftereffect in Neutron-Irradiated Ni Single Crystals

Abstract

The magnetic aftereffect of Ni single crystals following an irradiation of 10¹⁹ neutrons/cm² was investigated in the temperature interval between 90° and 400°K. In addition to small peaks, major relaxation peaks were observed at −125°C, −98°C, −79°C, and −28°C. Above 0°C some broad peaks are observed. An analysis of the disaccommodation shows that the relaxation peaks are due to single relaxation processes, the relaxation times of which depend on temperature through an Arrhenius equation. The relaxation peaks are attributed to the reorientation of point‐defect clusters. A detailed analysis shows that the relaxation peak at −28°C is due to the reorientation of divacancies (orthorhombic symmetry). The relaxation above 0°C is the result of a diffusion of the divacancies within the domain walls. The low‐temperature peaks are tentatively ascribed to the reorientation of trivacancies (trigonal symmetry) and other point‐defect clusters, some of them possibly involving impurities.