Effect of nickel doping on magnetic and dielectric properties of orthorhombic calcium ferrite nanoparticles
R. UmashankaraRaja, Y.S. Vidya, H.C. Manjunatha, M. Priyanka, R. Munirathnam, K.M. Rajashekara, S. Manjunatha, E. Krishnakanth
Abstract
Nickel (10-50 mol %) doped calcium ferrite nanoparticles (NPs) are synthesized by the solution combustion method using lemon juice extract as a reducing agent, followed by calcination at 500oC. The calcined samples are characterized with different techniques. The Bragg reflections of Nickel doping confirm the formation of a single orthorhombic calcium ferrite phase. The crystallite size is estimated using both Scherrer’s and the W-H plot method. The surface morphology consists of irregular size and shaped agglomerated NPs along with pores and voids. A blueshift and a broad absorption spectrum is observed with an increase in the direct energy band gap. The direct energy band gap estimated from Wood and Tauc’s relationship was found to be 2.91-2.97 eV with an increase in dopant concentration. The magnetic analysis provided values for saturation magnetization (Ms), remanence (Mr), and coercivity (Hc), while dielectric studies demonstrated a dielectric constant of 2.81, 2.14, and 1.67 with increasing dopant concentration. The variation of dielectric properties of the sample as a function of frequency in the range 0.1–20 MHz has been studied at room temperature. The dielectric properties of CaFe2O4: Ni (1-9 mol%) NPs clearly indicate that there is a more pronounced dispersion at lower frequencies, gradually reaching saturation as the frequency increases. The dielectric loss was found to decrease from 4.62, 3.22, and 2.32 with an increase in Ni2+ substitution (10, 30, and 50 mol %) respectively. These results indicate the suitability of these samples for applications in memory devices and high-frequency applications.