EFFECT OF SINTERING ATMOSPHERE ON MAGNETIC AFTEREFFECT IN POLYCRYSTALLINE YTTRIUM-IRON-GARNET SAMPLES

Time effects associated with domain-wall stabilization processes are i nvestigated at temperatures ranging from 80 to 420 K, for yttrium iron garnet polycrystalline samples sintered in different atmospheres. A v ery different behavior for samples sintered in high and low oxygen par tial pressures is found. Above 0.1 atm the isochronal relaxation spect ra show a peak around 180 K that could be associated with an electron diffusion controlled domain-wall relaxation. The activation energy for the process is close to 0.4 eV. Below this pressure, the spectra show both positive and negative peaks as a result of the competition betwe en disaccommodation and accommodation processes. These peaks are close ly temperature spaced in the neighborhood of 130 K, and the relaxation mechanism responsible for this behavior is not yet clear.