Paramagnetism in Co doped ZnO films deposited by pulsed laser ablation

F. GOLMAR, A. M. MUDARRA NAVARRO C. ZAPATA, M. VILLAFUERTE, S.P. HELUANI AND C. RODRÍGUEZ TORRES

Buenos Aires

Workshop; At the Frontiers of Condensed Matter IV; 2008

Comisión Nacional de Energía Atómica, Departamento de Física de la Universidad de Buenos Aires y Universidad San Martin

In this work, we present a structural, magnetic and electrical transport characterization of Zn0.9OCo0.1 and Zn0.85OCo0.15 films deposited on Si/SiO2 substrates in N2 or O2 atmospheres by pulsed laser ablation. X-ray absorption spectroscopy results showed that Co ions are in 2+ state, substituting Zn in the ZnO structure. The magnetic results showed the lack of ferromagnetism. The M vs H loops taken at 5 K showed the characteristics of paramagnetic behaviour. These curves were well fitted with the Brillouin function using L = 1.3 and S=3/2 in agreement with the values expected for Co2+. The voltage vs. current curves showed a slight asymmetry that increase when temperature decrease and lost the linear behaviour at low temperatures. The samples present positive magnetoresistance. This behaviour was previously observed in ZnO films deposited on sapphire.