Suppression of inherent ferromagnetism in Pr-doped CeO2 nanocrystals

Abstract

Ce(1-x)Pr(x)O(2-δ) (0 ≤ x ≤ 0.4) nanocrystals were synthesized by self-propagating method and thoroughly characterized using X-ray diffraction, Raman and X-ray photoelectron spectroscopy and magnetic measurements. Undoped CeO₂ nanocrystals exhibited intrinsic ferromagnetism at room temperature. Despite the increased concentration of oxygen vacancies in doped samples, our results showed that ferromagnetic ordering rapidly degrades with Pr doping. The suppression of ferromagnetism can be explained in terms of the different dopant valence state, the different nature of the vacancies formed in Pr-doped samples and their ability/disability to establish the ferromagnetic ordering.

Modification of Ce valence states by Sm/Sr co-doping of CeO 2 nanoparticles for improved magneto-electrochemical properties

“…6(b) and (d) for x = 0, y = 0 and x = 0.05, y = 0.05 respectively had similar peak positions corresponding to crystal lattice oxygen (O L ) (528.8 and 529.2 eV) and hydroxyl oxygen (O H ) (531.7-532.8 eV). The oxygen vacancies in our samples contributed peaks at similar positions (533.9-535.1 eV) to those previously reported [18,19,43]. The EDX spectra of Fig.…”

“…The sample with x = 0.05 and y = 0.05 showed the highest M S value of 0.013 emu/g and the largest H C of 1400 Oe, indicating that optimal Sm 3+ and Sr 2+ doping is with low contents in the vicinity of x = 0.05 and y = 0.05. Doping of a CeO 2 host with Zn and Co [35], the highest M S value of 8.55 × 10 −4 emu/g was reported when x = 0.1, and similarly in RE doped CeO 2 samples, i.e., 0.012 emu/g, 0.004 emu/g and 0.001 emu/g in Sm 3+ (15 at.% Sm) [19], Gd 3+ (10 at.% Gd) [38] and Pr 3+ (15 at.% Pr) [18] doped CeO 2 nanoparticles, respectively. These results show that ferromagnetism can be improved by co-doping CeO 2 with small amounts of specific metal ions.…”

“…6(a) and (c) show the Ce 3d peaks for x = 0, y = 0 and x = 0.05, y = 0.05 respectively. The Ce 3d 5/2 (881.7 and 882.3) and Ce 3d 3/2 (897.6 to 898.1 and 900.2 to 900.6 eV) peaks were assigned to the Ce 4+ ion and the Ce 3d 5/2 (883.3 to 883.8 and 884.9 to 885.2 eV) and Ce 3d 3/2 (901.8 to 903.8 eV) peaks were assigned to the Ce 3+ ion [18,19,38]. The Sm 3d 5/2 (1076.6 to1082.0 eV) and Sm 3d 3/2 (1103.6 to 1109.3 eV) peaks for the x = 0.05, y = 0.05 sample in Fig.…”

“…CeO 2 doped with TMs such as Fe, Co, Ni, Mn and Cu or REs such as Sm, Nd, Pr and Gd have been found to exhibit RT-FM which has been explained by a V O mediated F-center exchange (FCE) mechanism [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. In addition to their advantageous magnetic properties, improved electrical, optical and catalytic properties have been found in alkaline earth (AE) and REdoped CeO 2 materials.…”

Structure and Magnetic Properties of Monodisperse Fe3+-doped CeO2 Nanospheres

“…However, the source of the magnetism is not only from the magnetically ordered spin of 3D dopants but also from the defects at surface. Ferromagnetic behaviors with large moments were also observed even in undoped CeO 2 [17] and CeO 2 doped with rare earth such as Nd, Sm [18] or Pr [19]. The authors suggested that defects play an important role in the magnetism, and that only a small fraction of the volume, possibly associated with the surface is active [17][18][19][20].…”