Nature of charge transport and p-electron ferromagnetism in nitrogen-doped ZrO2: An ab initio perspective

Abstract

Zirconium dioxide provides an exceptional prototype material for studying the redistribution of the polaron holes and its magnetic coupling with their nearby anions owning to the difference oxygen binding behavior in the monoclinic phase. Here, we perform a comprehensive study of the p-electron magnetism in the nitrogen doped 2 × 2 × 2 monoclinic ZrO2 based on spin-polarized density functional theory. Nitrogen substitutions make the system display half-metallic properties, and the origin of room temperature ferromagnetism ascribes to the p-p coupling interaction between N 2p and the host 2p states. The charge density difference and Mülliken population analyses provide evidences of charge redistributions. Our results reveal that the polaron transfer may alter the magnetic properties and it is greatly facilitated ferromagnetic coupling if the polaron holes are localized around a single anion dopant.

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

“…Once this is done, the magnetic coupling falls to 0.7 meV, thus strongly decreasing T c that becomes 22 K. Therefore, we can exclude room temperature ferromagnetism for this system, differently from what has been suggested in ref. 34 . This is a direct consequence of the strong localization of the unpaired electron in the N 2p states.…”

“…The fact that the nitrogen dopant introduces magnetic states in the material has previously led to the suggestion that N-ZrO 2 can behave as a diluted magnetic semiconductor exhibiting ferromagnetic ordering at room temperature 34 . Some calculations, performed with standard GGA DFT functional, which however suffers from self-interaction problems, were proposed to prove it.…”

“…Furthermore, a recent theoretical work of H. Zhu et al . 34 . predicted p-ferromagnetism behavior for N-ZrO 2 .…”

Role of Nanostructuring on the Properties of Oxide Materials: The Case of Zirconia Nanoparticles

“…It is also possible in principle to dope oxides with 2p elements such as nitrogen. For instance, N‐ZrO 2 has been predicted to behave as a ferromagnet at room temperature (r.t.), but the origin of the magnetic behavior is still unclear and matter of debate …”

Regulation of the magnetic behavior by adjusting oxygen stoichiometry in ZrOx film

“…On the contrary, it is proposed that anion defects can also induce FM in material systems such as ZnO [4] and SnO 2 [5] . In recent years, FM was also observed in oxides doped with "nonmagnetic" elements [6] as well as undoped oxides [7] , which opened an extensive controversy about whether FM is intrinsic or due to extrinsic origins such as metallic clusters and inadvertent contamination.…”