Effect of Co substitution on the structural and magnetic properties of Zn–W hexaferrite

The polycrystalline samples of the composition Zn_2−XCo_XBaFe₁₆O₂₇ were prepared by the usual ceramic technique with X=0.4, 0.6, 0.8, 1, 1.2, 1.4 and 1.6. The samples were sintered at 1300 °C for 8 h. The X-ray diffraction patterns confirm the presence of single W-hexagonal phase. The lattice parameters c and a was found to increase by increasing Co content whereas the X-ray density decreases and porosity increases by increasing Co content. The value of saturation magnetization (σ) decreases by increasing Co content due to the decrease of super-exchange interaction. The magnetic moment of the sample were calculated and it showed that in Zn_2−XCo_XBaFe₁₆O₂₇ nearly all Co²⁺ ions are distributed among the octahedral sites of spinel S block. The M–H hysteresis loop for all the samples are clearly showing low coercivity, indicating that all the samples belongs to the family of soft ferrite. The values of coercivity increases by increasing Co content. The far infrared absorption spectrum showed the presence of three absorption bands corresponding to tetrahedral, octahedral and hexahedral sites.