Structural, magnetic and dielectric properties of lanthanum substituted Mn0.5Zn0.5Fe2O4

Abstract

Mn0.5Zn0.5LaxFe2-xO4 (x = 0.0, 0.025, 0.050, 0.075 and 0.10) ferrites have been synthesized using coprecipitation method. Effect of substitution of La3+ on structural, magnetic and dielectric properties of Mn0.5Zn0.5Fe2O4 was studied. Structural properties have been investigated using X-ray diffraction (XRD) and morphological by transmission electron microscopy (TEM). XRD analysis revealed the formation of cubic spinel structure. Different structural parameters like lattice parameter, crystallite size, interionic distances, average cationic radii, bond angles and bond lengths have been calculated and compared with various theoretically predicted parameters. TEM images confirmed that particle size decreases with La content. Magnetic behavior of synthesized samples was studied employing vibrating sample magnetometer (VSM). It was noted that as x increased from 0 to 0.1, maximum magnetization showed decreasing trend from 34.57 emu/gm to 15.34 emu/gm (noted at 15000 G) and Curie temperature from 193 °C to 147 °C at constant field of 500 G. Real (є ̍) and imaginary part (є ̎) of dielectric constant, dielectric loss (tan δ), ac conductivity (σac), real (Z ̍) and imaginary part (Z ̎) of impedance were studied with frequency (0.1 Hz–1 MHz) and composition. є̍, є ̎, tan δ and σac were observed to decrease with substitution of La3+ ions. This variation can be attributed to the hopping of electrons between Fe2+ ions and Fe3+ ions at octahedral sites. Cole-cole plot showed a single semicircular arc for Mn0.5Zn0.5LaxFe2-xO4 clearly indicating the dominant effect of grain boundary in conduction.