A composite material composed of 79% LaSr(CoFe) \(_{1/2}\) O \(_4\) Ruddlesden-Popper phase and 21% (LaSr) \(_{1/2}\) (CoFe) \(_{1/2}\) O \(_3\) perovskite was studied to explore its magnetic properties. In a low magnetic field of \(100 \, \text {Oe}\) , the material exhibits superparamagnetic behavior with a blocking temperature of \(T_B = 133 \, \text {K}\) . In contrast, at a high field of 10 000 Oe, the susceptibility deviates from paramagnetic behavior below 250 K, showing a gradual increase dominated by the perovskite phase. Below 50 K, the magnetization could be described as a combination of paramagnetic, superparamagnetic, and ferromagnetic contributions, with the saturation magnetization decreasing as the temperature dropped, driven by the perovskite phase. Mössbauer spectroscopy identified three groups of iron species: Fe \(^{4+}\) in the perovskite phase, suggesting a Fe \(^{4+}\) /Co \(^{3+}\) mixture rather than a 50:50 mixture of Co \(^{3+}\) /Fe \(^{3+}\) and Co \(^{4+}\) /Fe \(^{4+}\) . The other two groups, Fe \(^{3+\delta _1}\) and Fe \(^{3-\delta _2}\) , were associated with the Ruddlesden-Popper phase, where Fe \(^{3+\delta _1}\) plays a crucial role in stabilizing the crystal structure by compensating for the differences in ionic radii between Fe \(^{3+}\) and Co \(^{3+}\) .
