Isochronal recovery behaviour of complex permeability components and electrical resistivity in yttrium iron garnet (YIG) synthesized via mechanical alloying

Abstract

The causes of electromagnetic energy loss in very low loss yttrium iron garnet (YIG) are not fully understood. Thus, we have studied and now report on new findings concerning this problem at MHz and low GHz frequencies. We chose to observe if there would be new revealing data if a polycrystalline YIG sample was subjected to an isochronal recovery behaviour process, a procedure normally employed to study electrical resistivity and shear stress in metals by metallurgist. Thus, isochronal recovery behaviour of YIG samples’ complex permeability components, $${\upmu}^{{\prime }}$$ and $${\upmu}^{{\prime \prime }}$$ as well as their electrical resistivity (ρ), was studied in this work. The YIG samples were prepared via mechanical alloying of pure Y2O3 and Fe2O3 powders followed by appropriate sintering, measurement of properties, quenching, re-measurement of properties, isochronal annealing and a final repeat of property measurement. Results obtained from the experiments showed that isochronal recovery behaviour could be clearly exhibited by both the complex permeability components and the electrical resistivity. The measured property values gave their isochronal recovery behaviour in which the values, though suppressed after the quenching were recovered even higher after undergoing the annealing. We believe the mechanisms which produced the changes should involve atomic scale and submicron defects in the form of vacancies, interstitials, microcracks, dislocations etc. created in the quenched samples. It seems plausible that changes in the atomic and submicron defects concentration gave rise to changes in the values of the complex permeability components and electrical resistivity. Generally, the connection between such defects and isochronal recovery behaviour of material properties has been indicated in the literature.