EPR, ENDOR And Optical Study of Radiation Defects in Complex Oxides

Dr. Galina.Malovichko
Dr. Valintyn.Grachev
Physics Department
Montana State University

Solar, cosmic and nuclear reactor radiations lead to the appearance of defects in complex oxides. Most of radiation defects are paramagnetic (or can be recharged to a paramagnetic state). Therefore, magnetic resonance methods, Electron Paramagnetic Resonance (EPR) and Electron Nuclear Double Resonance (ENDOR) are one of the most suitable methods for the study of such defects.

The present work reports the EPR/ENDOR and simultaneous EPR/optical study of defects in single crystals irradiated by visible, UV and gamma photons, electrons and neutrons. Different oxide materials were investigated. Among them are lithium and barium borates, potassium titanyl phosphate, barium titanate, barium-calcium titanate and so on. Isochronal annealing in air and additional light illumination has been used for the determination of the stability of radiation defects.
We found that the dominated types of defects formed under visible, UV and gamma photon irradiation are centers created by lattice defects trapped electron or hole, recharged impurity ions and recharged regular lattice ions near intrinsic or extrinsic lattice defects. The dominated types of defects formed under neutron irradiation are stable Frenkel pairs (interstitial ions and vacancies) created by the impact mechanism.

Spectroscopic characteristics and models were determined for more than dozen paramagnetic centers. The obtained characteristics of different interactions and derived models of radiation defects can be used as cornerstones for theoretical calculations.