Room-temperature ferromagnetism induced by Na co-doping and K co-doping in the rare earth Er doped ZnO nanocrystallites

• Published in: Journal of alloys and compounds 2014-12, Vol.615, p.4-11
• Main Authors: Sivasankari, J., Sankar, S., Selvakumar, S., Sivaji, K.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Magnetic measurements; Magnetic properties and materials; Magnetic properties of nanostructures; Magnetic semiconductors; Optical properties; Physics; SEM; Semiconductors; Studies of specific magnetic materials; TEM; X-ray diffraction
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2014.06.146

•Na, K ions co-doped ZnO:Er nanopowders were synthesized by solution-combustion method.•Crystal structure and size were characterized by XRD.•Electron microscope (SEM and TEM) were used to determine the morphology and size of the particles.•Room temperature ferromagnetism was exhibited for Er+Na and Er+K co-doped ZnO nanocrystallites. We report the ferromagnetic behavior induced by co-doping Er-doped ZnO nanocrystallites with Na and K ions. All the samples, viz., ZnO:Er, Er+Na co-doped ZnO, and Er+K co-doped ZnO nanocrystallites have been synthesized by using the solution combustion technique. The XRD studies confirm the hexagonal wurtzite structure for all the samples. Average size of nano-crystallites has been observed to increase due to doping with Er, and then co-doping with alkali metals Na and K. Studies of SEM, TEM and EDAX were used to determine the morphology, size and presence of elements in the ZnO nanocrystallites. The FT-Raman studies show that there is no peak shift due to the co-doping of these elements; the peak at 437cm−1 corresponds to the standard Raman active E2 (high) mode. The VSM studies have shown that the co-doped samples exhibit ferromagnetism at room temperature itself, which is very unusual since the co-dopants are non-magnetic alkali metals. The ferromagnetic ordering of Na or K co-doped ZnO:Er is mainly attributed to oxygen vacancies and also to the minor impurity phase in ZnO lattice.