A Mössbauer study of the substituted hexagonal ferrites BaSrxCa1−xFe4O8 (0 ⩽ x ⩽ 1)

Ferrites of the formula BaCa_1?xSr_xFe₄O₈ (0 ? x ? 1) gave rise to magnetically split Mössbauer spectra indicative of antiferromagnetic ordering at room temperature. These spectra were analysed to yield the isomer-shift, quadrupole splitting, internal magnetic field and its orientation. The unit cell dimensions were obtained from X-ray powder patterns and were used in obtaining estimates of the electric field gradient (e.f.g.). The calculated and observed e.f.g. values indicate increasing symmetry as x → 1. A temperature dependence study of BaCaFe₄O₈ gave a Neel temperature T_N = 670 K and H_eff(O) = 485 kOe.