The magnetotransport properties of Co-doped ZnO films

Abstract

Co‐doped ZnO films with Co content above 7% have been grown by pulsed laser deposition on a‐sapphire substrates. Temperature and magnetic field dependent magnetotransport measurements have been performed on samples with electron concentration n around the critical electron concentration nc≈4.9×1019 cm−3, where the metal‐insulator transition (MIT) occurs. At 5 K we observed positive magnetoresistance (MR) in the insulating range (n nc). The MIT was determined from the MR and Hall effect at 5 K to occur at the electron concentration nc≈4×1019 cm−3. In the vicinity of the MIT (n∼nc) we observed negative MR at low field and positive MR at high field. Only for n<nc we observed clear anomalous Hall effect in the Co‐doped ZnO films being of relevance for use in future spintronic devices.