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On the defect induced ferromagnetic ordering above room-temperature in undoped and Mn doped ZnO thin films

Published online by Cambridge University Press:  31 January 2011

Mukes Kapilashrami ,
Jun Xu ,
Valter Ström ,
K V Rao  and
Lyubov Belova
Mukes Kapilashrami
Affiliation:
Department of Materials Science, Royal Institute of Technology, Stockholm, Sweden
Jun Xu
Affiliation:
Department of Materials Science, Royal Institute of Technology, Stockholm, Sweden
Valter Ström
Affiliation:
Department of Materials Science, Royal Institute of Technology, Stockholm, Sweden
K V Rao
Affiliation:
rao@kth.se, KTH, Dept. of Materials Science-Tmfy-MSE, The Royal Institute of Technology, Stockholm, Stockholm, S-100 44, Sweden, 46 (0) 8 790 7771
Lyubov Belova
Affiliation:
Department of Materials Science, Royal Institute of Technology, Stockholm, Sweden
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Abstract

Evidence for long range ferromagnetic order above room-temperature, RTFM, in pristine ZnO, In2O3, TiO2 nanoparticles and thin films, containing no nominal magnetic elements have been reported recently. This could question the origin of RTFM in doped dilute alloys if for example the ZnO matrix itself develops a defect induced magnetic order with a significant moment per unit cell. In this presentation we report a systematic study of the film thickness dependence of RTFM in pure ZnO deposited by DC Magnetron Sputtering. We observe a maximum in the saturation magnetization, MS, value of 0.62 emu/g (0,018 μB/unit cell), for a ˜480 nm film deposited in an oxygen ambience of appropriate pressure. Above a thickness of around 1 μm the films are diamagnetic as expected. We thus see a sequential transition from ferromagnetism to para- and eventual diamagnetism as a function of film thickness in ZnO. We also find that in such a ZnO matrix with a maximum intrinsic defect induced moment, on doping with Mn the maximum enhanced MS value of 0.78 emu/g is obtained for 1at.% Mn doping. With this approach of appropriate doping in a defect tailored matrix, we routinely obtain RTFM in both undoped and Mn- doped ZnO thin films.

Keywords

defectsferromagneticspintronic
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1183: Symposium FF – Novel Materials and Devices for Spintronics , 2009 , 1183-FF01-07
Copyright
Copyright © Materials Research Society 2009

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