22 - Role of defects and doping on magnetism in cerium oxide

Abstract

CeO2 has piqued the interest of researchers among the various rare-earth (RE) metal oxides studied due to its potential technological and environmental applications. It has been used in a broad range of applications, including spintronics, three-way catalysis, solid oxide fuel cells (SOFC), photocatalysis, catalytic converters, hydrogen production, crude oil refining, and so on. Exceptionally, high oxygen storage capacity of CeO2 is responsible for its broad range of applications. It has the ability to absorb oxygen from an oxygen-rich environment and release it in an oxygen-deficient environment without altering its fluorite structure. A lot of scientists have conducted research on nanoscale semiconductors of metal oxides like TiO2, MgO, Fe2O3, CeO2, ZnO, SnO2, HfO2, etc. to study the origin of room temperature ferromagnetism (RTFM). It has been noted that the ferromagnetic character in these systems enhanced when transition metals such as Fe, Ni, Mn, Co, Cr, or Cu and RE metals such as Sm, Y, Er, La, or Gd were doped. However, understanding the origin of RTFM is difficult because most researchers reported oxygen vacancies as the main contributing factor for FM enhancement, whereas others suggested hole-mediated FM. F-center exchange mechanism (FCE), Bound Magnetic Polaron (BMP), and Zener models are some of the accepted models for explaining FM ordering. Coey et al. used the FCE mechanism and claimed that ferromagnetic coupling is caused by electrons trapped in oxygen vacancies.