Optical and magnetic properties of laser-deposited Co-doped ZnO thin films

Abstract

We report the optical and magnetic properties of laser-deposited Zn1-xCoxO (x = 0.06-0.3) thin films with no intentional electrical carrier doping. The analysis of the high-temperature magnetization data provides an unambiguous evidence that antiferromagnetic superexchange interaction is the dominant mechanism of the exchange coupling between Co ions in Zn1-xCoxO alloy, yielding the value of the effective exchange integral J(1)/k(B) to be about - 27 K. The low-temperature magnetization data reveals a spin glass transition in Zn1-xCoxO alloy for the Co content x > 0.15, giving the value of the spin freezing temperature T-f to be similar to 8 and similar to 12 K for x = 0.2 and 0.25, respectively. Optical spectra analysis shows a linear increase of the band gap E-g with the increase of the Co content following E-g = 3.231 + 1.144x eV. (C) 2004 Elsevier Ltd. All rights reserved.