A Review of the Magnetic Relaxation and Its Application to the Study of Atomic Defects in α-Iron and Its Diluted Alloys

This review presents a comprehensive survey on intensive studies performed during the last decades on point defect reactions on α‐iron (α‐Fe) and its diluted alloys. Our intention is to give an actual account of the knowledge accumulated on this subject, as it has been obtained predominantly by means of the magnetic after‐effect (MAE) spectroscopy. After a concise introduction into the theoretical and experimental fundamentals of this technique, the main concern is focused on the presentation and detailed discussion of the MAE spectra arising — after low‐temperature electron (e–)‐ or neutron(n)‐irradiation and subsequent annealing — in: (i) high‐purity α‐Fe and α‐Fe doped with (ii) substitutional solutes (like Ni, V, Al, Cu, Ti, Be, Si, Mn, …) or (iii) interstitial solutes (like O, H, C, N). During the course of systematic annealing treatments, these respective spectra undergo dramatic variations at specific temperatures thereby revealing in great detail the underlying intrinsic reactions of the radiation‐induced defects, i.e., reorientation, migration, clustering, dissolution and finally annihilation. In alloyed Fe systems the corresponding reaction sequences are even multiplied due to additional interactions between defects and solute atoms. Most valuable information concerning formation‐, dissociation‐ and binding enthalpies of small, mixed clusters (of the type CiVk, NiVk; i, k ≥ 1) has been obtained in high‐purity α‐Fe base material which, after charging with C or N, had been e–‐irradiated. Concerning the basic recovery mechanisms in α‐Fe, two complementary results are obtained from the analysis of the various systems: (i) in high‐purity and substitutionally alloyed α‐Fe the recovery in Stage‐III (200 K) is governed by a three‐dimensionally migrating (HMI = 0.56 eV) stable interstitial (dumb‐bell); (ii) following the formation and dissociation kinetics of small clusters (C1Vk, N1Vk) in interstitially alloyed α‐Fe the migration enthalpy of the monovacancy must hold the following relation HMN (0.76 eV) < HMC (0.84 eV) < HMV1. These results are in clear agreement with the so‐called two‐interstitial model (2IM) in α‐Fe – a conclusion being further substantiated by a systematic comparison with the results obtained from nonrelaxational techniques, like i.e. positron annihilation (PA), which by their authors are preferentially interpreted in terms of the one‐interstitial model (1IM). Die vorliegende Arbeit gibt einen umfassenden Überlick über die während der