Evidence of Ferromagnetic Signal Enhancement in Fe and Co Codoped ZnO Nanoparticles by Increasing Superficial Co3+ Content

Authors

J. J. Beltrán, Universidad de Antioquia
C. A. Barrero, Universidad de Antioquia
A. Punnoose, Boise State UniversityFollow

Document Type

Article

Publication Date

5-20-2014

Abstract

In spite of the various theoretical and experimental efforts performed to understand the origin of ferromagnetism in Fe and Co codoped ZnO, there are still serious controversies in the reported data. While theoretical studies predicted the relative spin alignment and location of Co²⁺ and Fe²⁺ as the main source of magnetism, experimental studies have reported Co²⁺and superficial Fe³⁺. In this work, we performed a careful experimental study on Zn_1–2xFe_xCo_xO (x = 0, 0.01, 0.03, and 0.05) nanoparticles prepared by a sol–gel method and have found new interesting results. We detected only Fe³⁺ ions located in tetrahedral-core and pseudo-octahedral-surface sites. The Co ions displayed 2+ and 3+ oxidation states, with Co²⁺ ions in high spin state located mostly in the tetrahedral-core sites, while Co³⁺ in low spin states located presumably in pseudo-octahedral-surface sites. We detected isolated Fe³⁺ ions and weakly ferromagnetic coupled Co²⁺ ions. The most important finding is that the saturation magnetization (Ms) did not depend on the magnetic interactions involving the high spin Co²⁺or Fe³⁺; but M_s and Co³⁺ concentration increased systematically with x, indicating that multivalent ionic states may be playing a crucial role in the observed ferromagnetism.

Publication Information

Beltrán, J. J.; Barrero, C. A.; and Punnoose, A.. (2014). "Evidence of Ferromagnetic Signal Enhancement in Fe and Co Codoped ZnO Nanoparticles by Increasing Superficial Co3+ Content". The Journal of Physical Chemistry C, . http://dx.doi.org/10.1021/jp501933k