Synthesis and room-temperature ferromagnetism of CeO2 nanocrystals with nonmagnetic Ca2+ doping.
This work initiates an investigation on the creation of room-temperature ferromagnetism in diamagnetic solid via a nonmagnetic doping. CeO(2) is taken as a prototype compound. A series of Ce(1-x)Ca(x)O(2-delta) solid solutions with x = 0-0.25 were prepared by a solution combustion method using L-glutamic acid as the fuel. Sample characterization indicates that all as-prepared samples crystallized in a pure face-centered cubic fluorite structure with crystallite sizes smaller than 10 nm. On increasing the dopant content, the crystallite size decreased from about 8 to 4 nm, while the lattice parameter increased systematically. At room temperature, all samples are ferromagnetic admixed with an apparent diamagnetic component, as composed to a mixture of paramagnetic and antiferromagnetic behaviors or the absence of the ferromagnetism reported in the literature (Bouaine et al 2007 J. Phys. Chem. C 111 2924-8; Ney et al 2008 Phys. Rev. Lett. 100 157201) for magnetically doped semiconductors such as Sn(1-x)Co(x)O(2) and Zn(1-x)Co(x)O. The coercivity and saturation magnetization for x = 0 are 110 Oe and 2.01 x 10(-4) emu g(-1), respectively, which slightly increased to 148 Oe and 2.26 x 10(-4) emu g(-1) on increasing the dopant content to x = 0.10. Upon annealing the as-prepared samples at 800 degrees C for 2 h, these magnetic parameters were weakened. This observation was interpreted in terms of the mixed valence state of Ce(3+)/Ce(4+) and the doping effects. Finally, the nature of the room-temperature ferromagnetism is discussed by taking into account the oxygen vacancies and defects at the surface/interfaces that act as the electron and hole traps.
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Fuzhou 350002, People's Republic of China.
Xiaobo
X
Chen
Guangshe
G
Li
Yiguo
Y
Su
Xiaoqing
X
Qiu
Liping
L
Li
Zhigang
Z
Zou