Charge localization in doped and undoped ceria: the non-standard model

GUSTAVO E. MURGIDA; ANA M. LLOIS; VERÓNICA VILDOSOLA; VALERIA FERRARI

Trieste

Workshop; Joint ICTP-IAEA Workshop on Non-adiabatic Dynamics and Radiation Damage in Nuclear Materials; 2011

ICTP-IAEA

The search and development of novel materials, ferromagnetic beyond room temperature, is currently a subject of intense work with the driving force of its potential technological applications. In thisregard, Cerium oxide with diluted magnetic impurities is a natural candidate for spintronics as it offers a good integrability with the current electronic devices. However, this material still poses severalquestions being the main one to find a consensed explanation for the observed room temperature ferromagnetism.There is experimental evidence supporting the idea that the free electrons left behind by oxygen vacancies localize themselves in specific Cobalt and Cerium atoms, changing their oxidation states(Co4+ -> Co2+ and Ce4+ -> Ce3+, respectively) and turning the Cerium atoms into magnetic ones.The study of this charge localization is crucial to aproach an understanding of the magnetic properties in these materials.Using the framework of the Density Functional Theory, we evaluate the relative stability for different configurations of vacancies in Co doped Ceria and we show that the vacancies tend to locate close tothe Co impurities. In addition, we address the issue of the charge localization that takes place due to desoxygenation processes, finding that the excess electrons reside at Ce atoms which are next nearestneighbours of the vacancy sites.