Theory of Ferromagnetism in Reduced ZrO_2–x Nanoparticles

Abstract

Bulk ZrO 2 is both nonreducible and nonmagnetic. Recent experimental results show that dopant-free, oxygen-deficient ZrO 2– x nanostructures exhibit a ferromagnetic behavior at room temperature (RT). Here, we provide a comprehensive theoretical foundation for the observed RT ferromagnetism of zirconia nanostructures. ZrO 2 nanoparticles containing up to 700 atoms (3 nm) have been studied with the help of density functional theory. Oxygen vacancies in ZrO 2 nanoparticles form more easily than in bulk zirconia and result in electrons trapped in 4d levels of low-coordinated Zr ions. Provided the number of these sites exceeds that of excess electrons, the resulting ground state is high spin and the ordering is ferromagnetic. The work provides a general basis to explain magnetism in intrinsically nonmagnetic oxides without the help of dopants.

Spin-polarized electronic states and atomic reconstructions at antiperovskite Sr3SnO(001) polar surfaces

“…The case of oxygendeficient ZrO 2 is particularly interesting, as it has been shown that the ferromagnetic ordering was more likely to form in thin films or nanoparticles. Albanese, et al [55] demonstrated that in nanoparticles the magnetic state only forms if the number of low-coordinated Zr atoms is sufficient in regard to the number of excess and available charges. They also found that the ferromagnetic ordering is favored by the hybridization between the gap states and the bands at the bottom of the conduction bands.…”

Characterization of Acid and Basic Sites on Zirconia Surfaces and Nanoparticles by Adsorbed Probe Molecules: A Theoretical Study

“…Now we consider two zirconia stoichiometric clusters to model the properties of zirconia nanostructures. Details on how these have been obtained and on their electronic structure can be found in refs [34][35][36][37]. We have studied the adsorption of CO on different surface Zr atoms of Zr 16 O 32 ( Fig.…”

“…In this work we will discuss the acidity and basicity of regular t-ZrO 2 (101) and m-ZrO 2 ( 1 11 ) and stepped t-ZrO 2 (134) and m-ZrO 2 ( 2 12 ) surfaces, as well as of zirconia nanoparticles of size ranging between 1.5 and 2 nm, (ZrO 2±x ) n with n = 13-85 [34][35][36][37][38].…”

A DFT investigation of the role of oxygen vacancies on the structural, electronic and magnetic properties of ATiO3 (A = Mn, Fe, Ni) multiferroic materials

“…[20][21][22][23][24][25][26] For instance, Pacchioni et al described ferromagnetism in reduced ZrO 2-x nanoparticles and indicated that neutral oxygen vacancies can induce local ferromagnetism in non-magnetic 4d cations through a ferromagnetic arrangement between reduced Zr 3+ centers. 27,28 The same authors also predicted local magnetism in other materials such as WO , TiO 2 , and NiO by using both bulk and surface models. 29,30 However, it is important to point out that the existence of reduced centers does not guarantees the existence of ferromagnetism, because the spins located at the reduced centers could be antiparallel ordered, as reported for TiO 2 .…”