Magnetic and dielectric properties of Co doped nano crystalline Li ferrites by auto combustion method

•[Li0.5Fe0.5]1−xCoxFe2O4 (0.0≤x≤1.0) have size in the range of 36–43 nm.•These materials are used for the fabrication of hard magnets.•Doping of Co in the Li ferrites changed the magnetic behavior from soft to hard.•Materials show normal dielectric behavior.

The ultra fine particles of the cobalt substituted lithium ferrites with the formula [Li0.5Fe0.5]1−xCoxFe2O4 (0.0≤x≤1.0) were synthesized by low temperature citrate-gel auto combustion method. Structural characterization of the samples was carried out using XRD studies and FESEM (Field Emission Scanning Electron Microscopy) analysis. XRD studies confirms the formation of single phased spinel structure with crystallite size in the range of 36–43 nm. The M–H loops have been traced using Vibrating Sample Magnetometer (VSM) for all the compositions at room temperature and hysteresis parameters were evaluated. The hysteresis loops of the prepared samples show clear saturation at an applied field of ±20 k Oe and the loops were highly symmetric in nature. The dielectric parameters such as dielectric constant (ε'), dielectric loss tangent (tan δ) of the samples were studied as a function of frequency in the range of 20 Hz to 2 MHz at room temperature using LCR Meter. The dielectric constant and loss tangent of the samples show a normal dielectric behavior with frequency which reveals that the dispersion is due to the Maxwell-Wagner type interfacial polarization and hopping of electrons between the Fe2+ and Fe3+ ions.