Magnetic Anisotropy Induced by Self‐Interstitials in Low Temperature Electron Irradiated Iron

Abstract

After irradiation, iron (l), nickel (2), o r cobalt (3) presents an important magnetic after-effect zone which anneals out at the end of the stage I of the resistivity recovery. It was attributed, either to the one-dimensional migration of the crowdion (4) which reduces the permeability by a Dietze mechanism (5), o r to the three-dimensional migration and reorientation of a split interstitial. In this case, the magnetic after effect results from a NBel mechanism (6).Magnetic torque measurements made under saturating magnetic field can answer this question. This paper gives the results for iron.Experiments The samples are discs of polycristalline high purity iron ( @ 7 mm; e = 0.2 mm). They were irradiated, at 20 K, by 3 MeV electrons (dose 10l8 electrons, cm ) and transferred, at 77 K, into a torque measurement apparatus, which operates under saturating magnetic field (3400 Oe). Magnetic anisotropy is studied by measuring the torque exerted on the disc by a magnetic field applied in the plane of the disc successively along 18 different directions making angles 0 with an arbitrary diameter used a s origin. Measurements are made at a reference temperature T = 92 K , at which no evolution of the measured torques is observed.In the first experiment, the sample undergoes an isothermal treatment at T = 103 K , the magnetic field being at 0 . At given times, the thermal treatment is stopped, the temperature i s lowered down to 92 K, and measurements a r e made a s described above. The results show that, during the thermal treatment, a uniaxial 0 magnetic anisotropy develops slowly. This anisotropy can be written

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

“…23 have been used been ignored in the past and thus delayed the correct interpretation of experimental results. From magnetic anisotropy measurements, using a torque magnetometer, Verdone et al [106] derived a reorientation enthalpy for the Stage I E defect of 0.32 AE 0.015 eV, which fits well with the more recent MAE results of Table 2.…”

On the analysis of stage I in the resistivity recovery of electron irradiated iron

“…The sub-stages I D1 and I D2 have been previously ascribed to close-pair and correlated recombination, respectively. Magnetic and mechanical relaxation measurements [16,17] conducted in the temperature range of both of these stages have indicated similar activation energies of ∼ 0.3 eV in close agreement with the results of [4]. Thus, in order to provide a most simple and unifying model description, we employ a single activation energy, equal to E m , to both of these stages.…”