Structural, physical, magnetic and electrical properties of La-substituted W-type hexagonal ferrites

Lanthanum doped W-type hexaferrites BaZn₂La_xFe_16−xO₂₇ (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) were synthesized by co-precipitation and sintered at 1320 °C. The X-ray diffraction reveals W-type hexagonal structure with few traces of secondary phase. The decrease in grain size as a function of La-concentration is attributed to the fact that La acts as a grain inhibitor. The saturation magnetization and remanance decrease due to spin canting on B-sites. The increase in coercivity follows 1/r behavior where r is the radius of grain. The DC resistivity was observed to increase from 0.59 × 10⁷ to 8.42 × 10⁷ Ω cm with increasing La-contents due to the unavailability of Fe³⁺ ions. This enhancement in resistivity makes these materials promising candidates for use at high frequencies in order to reduce eddy current losses.