Synthesis and properties of cobalt substituted strontium cadmium W-type hexaferrites nanoparticles

• Nanosized W-type Strontium-hexaferrite, SrCd2−xCoxFe16O27 (0 ≤ x ≤ 2) have prepared by tartarate route.
• Effect of SrCd2Fe16O27 formation and role of Co2+on structural, electrical, magnetic properties are studied.
• Conductivity increases while activation energy decreases as Co2+ increases in SrCd2−xCoxFe16O27 system.
• The increased magneto-crystalline anisotropy causes an enhancement in coercivity from x ≥ 0.4 in SrCd2−xCoxFe16O27 system.
• A non-collinear spin arrangement observed in SrCd2−xCoxFe16O27 (0 ≤ x ≤ 2) system.

Nanoparticles of cobalt substituted strontium cadmium W-type hexagonal ferrites with the composition SrCd2−xCoxFe16O27 system with x = 0.0, 0.4, 0.8, 1.2, 1.6 and 2.0 were synthesized by the tartarate precursor method. The effect of strontium cadmium W-type hexaferrite formation and the role of cobalt content on structural, electrical and magnetic properties are studied by X-ray powder diffraction, infrared spectroscopy, transmittance electron microscopy, electrical conductivity, thermoelectric power and magnetic hysteresis measurements. The X-ray diffraction patterns of these systems show a hexagonal W-type structure. The lattice parameter ‘ao’ and ‘co’ was found to decrease with increase in substituting ions. The contraction of the unit cell volume can be explained by a different substitution of Cd2+ and Co2+ ions. The data of the temperature variation of the direct current electrical conductivity showed a definite break at a certain temperature, TC except the sample with x = 0; which corresponds to the extrinsic to intrinsic semiconductor transitions. The electrical conductivity increases, while activation energy decreases as cobalt substitution increases in SrCd2−xCoxFe16O27 compounds. Magnetic properties of all samples showed definite hysteresis loops. The saturation magnetization increases as cobalt content increases, which corresponds to strengthening the network of superexchange interactions. The coercive force slowly increases from x = 0.4 as cobalt concentration increases. This is due to magneto-crystalline anisotropy. The enhancement of coercivity as well as remanance ratio (MR/MS) above x ≥ 0.4, multidomain is inferred nucleation as one of the possible mechanisms for SrCd2−xCoxFe16O27 samples.