Band Gap Reduction and Improved Ferromagnetic Ordering via Bound Magnetic Polarons in Zn(Al, Ce)O Nanoparticles

ABSTRACT

Polycrystalline nanoparticles of Al-doped and Ce-co-doped ZnO were processed through sol-gel co-precipitation. Crystallite sizes determined from XRD were in the range of 10.90 to 48.77 nm. FTIR spectra indicated a stretching mode of Zn-O bond. The insertion of Al and Ce at Zn-O site created Al-O and Ce-O bonds. UV-vis spectra favoured the formation of impurity levels by doping and co-doping. Their overlapping with the conduction band edge led to the reduction of band-gap. Blue-green emission which arises from radiative recombination of a photogenerated hole with an electron occupying oxygen vacancy was observed in photoluminescence spectra. FESEM suggested granular growth in undoped ZnO which changed to diverse structures such as nano-bar and cluster of elongated grains. Significant improvement in room temperature ferromagnetism (RTFM) was noticed by co-doping of Ce in Al-doped ZnO. Formation of bound magnetic polarons (Ce³⁺-V_o-Ce³⁺) was the primary mechanism responsible for the improvement in RTFM.

KEYWORDS:

• ZnO
• al doping
• ce co-doping
• band gap reduction
• RTFM
• BMPs

Acknowledgments

The authors acknowledge facilities of Manipal University Jaipur (MUJ), India, namely Central Analytical Facility (CAF) for UV–vis, FTIR and PL measurements and Sophisticated Analytical Instrumentation Facility (SAIF) for FE-SEM studies. The authors also acknowledge Mumbai Centre of UGC-DAE Consortium for Scientific Research, India for magnetic measurements.

Disclosure statement

No potential conflict of interest was reported by the author(s).