[en] Full text: The present work is focused on the study of the magnetic properties of M-type hexaferrites with differing iron content, both directly and via hyperfine interactions using ⁵⁷Fe Mössbauer spectroscopy. M-type hexaferrites are versatile materials that are utilised in data recording, microwave devices and as permanent magnets. The non-stoichiometric strontium M-type hexaferrites SrFe_12-xO_19-δ with x = -0.50, -0.25, 0.25, 0.50, 0.75 and 1.00 have been prepared using the solid state reaction method with double step-sintering at 1200°C. X-ray diffraction patterns show generally good phase purity as quantified by Rietveld refinement. Residual α- Fe₂O₃ of 1.2 wt. % and 4.2 wt. % was noted for x = -0.25 and -0.50. Hysteresis curves were obtained at room temperature using a Physical Properties Measurement System (PPMS-ACMS) and the values of the saturation magnetisation were derived using the ‘approach to saturation’ law. The hyperfine parameters, obtained from ⁵⁷Fe Mössbauer spectroscopy, are discussed in terms of the distribution of Fe³⁺ sites in light of the differing iron contents. (author)