Oxygen Vacancy Induced Room Temperature Ferromagnetism in Pr-Doped CeO₂ Thin Films on Silicon

Abstract

Integration of functional oxides on Si substrates could open a pathway to integrate diverse devices on Si-based technology. Oxygen vacancies (Vo(··)) can strongly affect solid state properties of oxides, including the room temperature ferromagnetism (RTFM) in diluted magnetic oxides. Here, we report a systematical study on the RTFM of oxygen vacancy engineered (by Pr(3+) doping) CeO2 epitaxial thin films on Si substrates. High quality, mixed single crystalline Ce1-xPrxO2-δ (x = 0-1) solid solution films were obtained. The Ce ions in CeO2 with a fluorite structure show a Ce(4+)-dominant valence state in all films. The local crystal structures of the films were analyzed in detail. Pr doping creates both Vo(··) and PrO8-complex defects in CeO2 and their relative concentrations vary with the Pr-doping level. The RTFM properties of the films reveal a strong dependence on the relative Vo(··) concentration. The RTFM in the films initially increases with higher Pr-doping levels due to the increase of the F(+) center (Vo(··) with one occupied electron) concentration and completely disappears when x > 0.2, where the magnetic polaron concentration is considered to decline below the percolation threshold, thus long-range FM order can no longer be established. We thus demonstrate the possibility to directly grow RTFM Pr-doped CeO2 films on Si substrates, which can be an interesting candidate for potential magneto-optic or spintronic device applications.

On the local electronic and atomic structure of Ce1−xPrxO2−δ epitaxial films on Si

“…24 We have previously deposited and studied in detail single crystalline, mixed Ce 1Àx Pr x O 2Àd (x ¼ 0-1) solid solution films on Si (111) substrate. [25][26][27] The study of such thin films is expected to shed light on structureproperty correlation of oxides, thus enabling to improve their performance in different applications. It is found that with a)…”

“…26) but also inducing room temperature ferromagnetism in CeO 2 films. 27 Because the valence state of cations is a key issue in understanding the related properties of oxides, X-ray photoemission spectroscopy (XPS) has been employed for its investigation. 25,26 However, a drawback of XPS is its high surface sensitivity; use of a more bulk sensitive probe of the Ce valence, such as X-ray absorption fine structure (XAFS), is thus highly desirable.…”

Electronic Structure and Room Temperature Ferromagnetism in Gd‐doped Cerium Oxide Nanoparticles for Hydrogen Generation via Photocatalytic Water Splitting

“…The ferromagnetism in pure CeO 2 NPs may be arise from the nearest‐neighbor interaction, i.e., either double exchange (Ce 3+ – V O –Ce 4+ ) or superexchange (Ce 3+ – V O –Ce 3+ ), which is mediated by oxygen ions . The double exchange interaction forms an F + center because the two electrons left by V O are trapped on Ce 4+ ion and V O (hydrogenic orbital), while superexchange interaction forms an F 2+ center due to the both electrons are trapped on Ce 4+ ions . When Gd ion is incorporated into CeO 2 , it has suppressed the ferromagnetism of CeO 2 NPs (as shown in Figure b).…”

Optimizing the preparation of Ni‐Ce‐Pr catalysts for efficient hydrogen production by n ‐dodecane steam reforming

“…Moreover, metal‐doped ceria has received great attention . For example, praseodymium (Pr) was doped into ceria to increase the oxygen storage capacity (OSC) ability of the catalyst . Moreover, other metal‐doped ceria catalysts were developed, which exhibited high performance for steam reforming .…”

“…3,30,33,35,38 For example, praseodymium (Pr) was doped into ceria to increase the oxygen storage capacity (OSC) ability of the catalyst. 36,[38][39][40][41][42][43] Moreover, other metal-doped ceria catalysts were developed, which exhibited high performance for steam reforming. 9,30,[44][45][46] Hoang et al show that Zr doping could highly enhance catalytic performance for meta-Cresol steam reforming due to its high oxygen mobility brings its excellent anti-coking properties.…”