Enhanced room-temperature ferromagnetism on Co-doped CeO2 nanoparticles: Mechanism and electronic and optical properties

Kugalur Shanmugam Ranjith, Padmanapan Saravanan, Shih Hsien Chen, Chung Li Dong, Chih Liang Chen, Shih Yun Chen, Kandasami Asokan, Ramasamy Thangavelu Rajendra Kumar

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Abstract

The present study reports the effect of Co doping on the structural, optical, magnetic, and electronic properties of CeO2 nanoparticles (NPs) synthesized by a simple low-temperature co-precipitation method. Co doping was introduced by adding CoCl3 with different mole percentages (0%, 2%, 4%, and 6%) to cerium nitrate, which resulted in room-temperature ferromagnetism (RTFM). TEM and XRD analysis showed that the Co-doped CeO2 NPs are monodispersed with face centered cubic structure. The 6% Co-doped CeO2 NPs showed a coercivity value of 155 Oe and saturation magnetization of 0.028 emu/g at room temperature. The electronic structures of the as-prepared CeO2 and Co-doped CeO2 NPs were investigated by X-ray absorption near-edge structure (XANES) spectroscopy. The XANES spectra at Ce M- and L-edges clearly indicated a decrease in the valency state of Ce ions from Ce4+ to Ce3+ upon Co doping. This causes redistribution of oxygen ions and Co-Co bonding. The XANES study revealed that Co doping plays a prominent role in improving the ferromagnetism, as Co replaces the Ce site in the CeO2 cubic lattice and the concentration of oxygen vacancies may not be high enough to form a delocalized impurity band for enhancing the magnetic percolation of Co-doped samples. The XANES spectra at Co L-edges indicate direct Co-Co bond formation in the CeO2 lattices and also a weak bond with O ions. This is in agreement with the magnetic measurements which indicate that Co atoms induce enhancement in magnetic behavior in CeO2 nanostructures. (Graph Presented).

Original languageEnglish
Pages (from-to)27039-27047
Number of pages9
JournalJournal of Physical Chemistry C
Volume118
Issue number46
DOIs
StatePublished - 20 Nov 2014

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