Effect of lanthanum substitution on dielectric relaxation, impedance response, conducting and magnetic properties of strontium hexaferrite

•The substitution of La affects the dielectric and magnetic properties of strontium hexaferrite.•The electric behaviour of the compound follows the Koop’s phenomenological theory.•The impedance study shows the role of grain boundaries to the electric properties of the compound.•The substitution of La to strontium hexaferrite reduces the resistive nature of grain boundaries. Lanthanum strontium hexaferrite Sr1−xLaxFe12O19 (x=0,0.08,0.13,0.18) has been successfully synthesized by using citrate-precursor method and characterized by different techniques. The X-ray diffraction results revealed that the sample is crystalline in nature and is of single phase with the space group P63/mmc. The dielectric, conducting and impedance related studies have been carried out as a function of frequency and concentration of lanthanum in the frequency ranges of 20Hz–3MHz. Impedance studies were performed in the frequency domain to distinguish between bulk and grain boundary contributions of the material to the overall dielectric response. The electric response of the material was also modeled by an equivalent circuit and different circuit parameters were calculated. Magnetic characterization of the material was also performed and the effect of lanthanum concentration was studied. The hysteresis loop obtained from the magnetometer showed that with the increase of lanthanum concentration, the saturation magnetisation decreases while as coercivity increases.