Magnetoresistance of magnetically doped ZnO films

• Published in: Journal of physics. Condensed matter 2009-08, Vol.21 (34), p.346001-346001 (6)
• Main Authors: Behan, A J, Mokhtari, A, Blythe, H J, Ziese, M, Fox, A M, Gehring, G A
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport phenomena in thin films and low-dimensional structures; Exact sciences and technology; Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects); Physics
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/21/34/346001

Magnetoresistance measurements have been made at 5 K on doped ZnO thin films grown by pulsed laser deposition. ZnCoO, ZnCoAlO and ZnMnAlO samples have been investigated and compared to similar films containing no transition metal dopants. It is found that the Co-doped samples with a high carrier concentration have a small negative magnetoresistance, irrespective of their magnetic moment. On decreasing the carrier concentration, a positive contribution to the magnetoresistance appears and a further negative contribution. This second, negative contribution, which occurs at very low carrier densities, correlates with the onset of ferromagnetism due to bound magnetic polarons suggesting that the negative magnetoresistance results from the destruction of polarons by a magnetic field. An investigation of the anisotropic magnetoresistance showed that the orientation of the applied magnetic field, relative to the sample, had a large effect. The results for the ZnMnAlO samples showed less consistent trends.