Effect of Substrate Temperature on Structural, Morphological, Magnetic, and Electrical Properties of Fe₂CoSi Heusler Alloy Thin Films for Spin-Based Device Applications

Fe₂CoSi based Heusler alloy thin films are deposited on single crystal Si (111) substrate at different substrate temperatures varying from room temperature to 600 °C using ultrahigh vacuum DC magnetron sputtering. Structural analysis of the prepared thin films is carried out using GI-XRD measurement and it conform ordered L2₁ crystal structure of the films deposited at 450 °C and above. The atomic force microscopic (AFM) images of Fe₂CoSi thin films exhibiting 3D-like growth on Si (111) substrate at varying temperatures. The magnetic property of the thin films is studied using vibrating sample magnetometer (VSM). At 450 °C of substrate temperature, the prepared thin film exhibits high saturation magnetization (M_s = 948 emu/cc) and low coercivity (H_c = 8 Oe). The self-energy magnetization of the film and its own field is very high, when the temperature of the substrate was maintained at 450 °C and switching field ratio for this film was obtained as ~ 0.9 due to its high crystallinity and atomic ordering. The electrical property of Fe₂CoSi thin film is investigated using four-probe technique and a positive magnetoresistive behavior was observed for thin film deposited at a substrate temperature of 450 °C which indicates the possible half-metallic nature at room temperature. The enhanced magnetic and electrical properties obtained for the thin film prepared at 450 °C substrate temperature is highly suitable for spin based device applications.