Substrate temperature dependence of microstructure and magnetoresistance field sensitivity of Co–ZnO non-uniform nanocomposite film

Co–ZnO metal-semiconductor nanocomposite films have drawn a growing number of attention due to their significant room temperature (RT) magnetoresistance (MR) effect. In this paper, Co–ZnO non-uniform nanocomposite films with high crystallinity of ZnO matrix have been prepared by controlling substrate temperature. With the increase of substrate temperature, the Co particles grow and gradually aggregated into ferromagnetic clusters, which leads to an increase in saturation magnetization (Ms) from 5.8 to 6.7 kGs. Moreover, the growth of ferromagnetic clusters results in the formation of cluster-particle current paths and isolated magnetic particles, which have less contribution to the MR, causing the separation between MR curve and -(M/Ms)2 curve. This phenomenon induces a broadening of the MR curve, which modulates the shift of the MR field sensitivity (FS) peak toward higher fields. When the substrate temperature is 250 °C, high ZnO matrix crystallinity, -MR value (2.6%) and effective modulation of MR FS in Co–ZnO non-uniform nanocomposite films can be achieved simultaneously. It provides a reference for the application and modification of Co–ZnO MR devices.