Magnetic properties of nitrogen-doped ZrO2: Theoretical evidence of absence of room temperature ferromagnetism

Abstract

N-dopants in bulk monoclinic ZrO2 and their magnetic interactions have been investigated by DFT calculations, using the B3LYP hybrid functional. The electronic and magnetic properties of the paramagnetic N species, substitutionals and interstitials, are discussed. Their thermodynamic stability has been estimated as a function of the oxygen partial pressure. At 300 K, N prefers interstitial sites at any range of oxygen pressure, while at higher temperatures (700–1000 K), oxygen poor-conditions facilitate substitutional dopants. We have considered the interaction of two N defects in various positions in order to investigate the possible occurrence of ferromagnetic ordering. A very small magnetic coupling constant has been calculated for several 2N-ZrO2 configurations, thus demonstrating that magnetic ordering can be achieved only at very low temperatures, well below liquid nitrogen. Furthermore, when N atoms replace O at different sites, resulting in slightly different positions of the corresponding N 2p levels, a direct charge transfer can occur between the two dopants with consequent quenching of the magnetic moment. Another mechanism that contributes to the quenching of the N magnetic moments is the interplay with oxygen vacancies. These effects contribute to reduce the concentration of magnetic impurities, thus limiting the possibility to establish magnetic ordering.

Theory of Ferromagnetism in Reduced ZrO2–x Nanoparticles

“…10,11 Oxides doped by light 2p elements (e.g., C- and N-ZnO, 12,13 C- and N-TiO 2 , 14,15 N-ZrO 2 , 16 and N-BaTiO 3 17 ) have been also considered and predicted as ferromagnets at room temperature (RT), but the origin of the magnetic behavior is a matter of debate. 18−20 In other cases, staying with the material of interest for this study, tetragonal zirconia, no ferromagnetism has been observed by doping the oxide with Mn. 21…”

Tuning the electronic band gap of Cu2O via transition metal doping for improved photovoltaic applications

“…Despite the significant effort invested into exploring the conventional properties of doped Cu 2 O, relatively less effort has been devoted to study the impact of extrinsic dopants on the photovoltaic properties of Cu 2 O. Moreover, theoretical investigations performed at the general gradient approximation level often lack completeness in the description of oxide electronic properties [35]. In this study, the effect of first row transition metal (FRTM) dopants on the overall photovoltaic absorption potential of Cu 2 O is explored, using a systematic hybrid-DFT approach.…”

Magnetic properties of cobalt doped ZrO2 nanoparticles: Evidence of Co segregation

“…Also, an experimental study on K doped TiO 2 [33] show, however, that weak paramagnetism is observed but no long-range ferromagnetic order. Another interesting aspect, is the analysis of the magnetic behavior in N-doped ZrO 2 , as in very recent theoretical studies, ferromagnetism is suggested to appear in certain conditions [34], while its absence at room temperature is also claimed [35]. Besides, as small Co or Co oxide precipitates form part of this system, the dynamic behavior can be also a subject that deserves to be studied.…”