Influence of annealing on structural, morphology, magnetic and optical properties of PLD deposited CuFe2O4 thin films

Abstract

• Successfully produced of CuFe 2 O 4 nanoparticles and prepared thin films which is grown on a glass substrate by pulsed laser deposition (PLD) technique. • The detailed structural properties of films are studied using experimental (XRD, FE-SEM, VSM, and Optical properties). • The magnetization and remanence of prepared samples have decreased with increased annealing substrate temperatures. • As per report the thin films have direct band gap energy; it reduces with increasing annealing temperature, which is due to improve the crystallinity. In this work, copper-ferrite (CuFe 2 O 4 ) nano-crystallite was synthesized by the gel method and deposited on a microscope glass substrate using a pulse laser deposition (PLD) technique at room temperature. The obtained deposited thin films were annealed at four different temperatures (200 °C, 300 °C, 400 °C, and 500 °C) for 4 hours in an air atmosphere. The structural, morphological, thermal, magnetic, and optical properties of the thin film samples were characterized using an X-ray diffractometer (XRD), Field emission scan electron microscopy (FE-SEM), thermogravimetric and differential thermal analysis (TG-DTA), Vibrating sample magnetometer (VSM) and Ultraviolet-Visible spectrophotometer (UV-Vis). X-ray diffraction patterns of the unannealed and annealed films show the presence of the anti-ferromagnetic (α-Fe 2 O 4 ) phase along with the single-cubic spinel structure phase. The grain sizes were found to have low crystalline copper ferrite with a mixture magnetic and hematite crystalline phases. With the decrease of the grain size and increasing of annealing substrate temperatures, the ratio of hematite to magnetite phases increased, and reached to an impure magnetite phase for the 6.35 nm grain. The morphological images obtained by transmission electron microscopy technique showed that the particle size of copper ferrite nanoparticles gradually became smaller from 10 nm to 5 nm. Surface morphology of all fabricated samples investigated by field emission scan electron microscopy technique exhibiting different sizes, almost spherical grains and agglomerates, which may be depending upon preparation method and substrate temperature. The correlation between structure and thermal stability of prepared materials was studied by (TG-DTA). With increasing of annealing substrate temperature from room temperature to 500 °C, the saturation magnetization (M s ) value decreased from 8.79 emu/g to 2.12 emu/g while the coercivity (H c ) value increased from 52.22 Oe to 91.26 Oe. The lowest widening of optical band gap in the copper ferrite film was 1.57 eV. The magnetic and the optical parameters suggested that these films are potential candidates for gas sensor applications.