Synthesis and magnetotransport studies of CrO2–Al2O3 composite films

Abstract CrO 2 –Al 2 O 3 composite films were deposited on Si(100) substrates by the atmospheric pressure chemical vapor deposition method using CrO 3 and AlBr 3 as precursors. The CrO 2 –Al 2 O 3 composite films consist of large CrO 2 grains and Al 2 O 3 nanoparticles. The composition of the films was controlled by adjusting the temperature of CrO 3 during deposition. The CrO 2 –Al 2 O 3 composite film with Al 2 O 3 content of 0.38 (molar fraction) shows insulator–metal transition. Below 120 K, it is insulator and the temperature dependence of its resistance can be well explained by the fluctuation-induced tunneling model; above 175 K, it is metallic. It shows large intergrain tunneling magnetoresistance at low temperature, which reaches −15.2% at 5 K and 50 kOe. While at high temperature the intergrain tunneling magnetoresistance in the film nearly disappears, and the film shows a small linear magnetoresistance, which should be due to the double-exchange mechanism in CrO 2 .