Comparative study of sonochemically and hydrothermally synthesized Mn0.5Zn0.5SmxEuxFe2−2xO4 nanoparticles: Structural, optical and magnetic properties

Abstract Facile hydrothermal and sonochemistry approaches were employed to synthesize the spinel ferrite NPs Mn 0.5 Zn 0.5 Eu x Sm x Fe 2−2x O4 ( x = 0 .0–0.5), viz. hydrothermal (H-MZESF NPs) and ultrasonic (U-MZESF NPs), respectively. The products were analyzed and compared based on structure, morphology, magnetic and optical properties. The single phase and mixed spinel structures were evidenced by XRD analysis. The crystallite size of the H-MZESF and U-MZESF NPs are within the ranges 8.0–12.5 and 4.5–11.5 nm, respectively. HR-TEM, TEM and SEM analyses proved the cubic morphologies of all the products. DR% measurements indicated that an estimation of the direct energy band gap ( E g ) of all the samples was possible from Tauc plots. The E g values of the H-MZESF and U-MZESF NPs were 1.64 and 1.1 eV, respectively. Co-doping causes significant changes, particularly in the band gap of U-MZESF NPs. Magnetic field and temperature dependent VSM magnetization investigations revealed the superparamagnetic nature at RT and ferrimagnetic nature with a multi domain structure at low temperatures. The magnetization data obtained at 10 K and calculated magneton numbers are (2–2.4) times larger with respect to the data obtained at 300 K. Measured coercivities ( H C ) are in the ranges 210–690 and 318–1182 Oe for the H-MZESF and U-MZESF NPs, respectively. The calculated effective magnetocrystalline constants ( K eff ) are of the order of 104 Erg/g for both types of samples.