Abstract

SrFe12O19/FeCo hard–soft magnetic nanocomposites with different hard-to-soft magnetic phase ratios were successfully synthesized using a combination of sol–gel autocombustion and wet-chemical methods, followed by physical mixing. X-ray diffraction analysis confirmed the formation and coexistence of the hexagonal SrFe12O19 hard magnetic phase and body-centred cubic FeCo soft magnetic phase, with no detectable crystalline impurity phases. The structural parameters showed a composition-dependent variation in crystallite size and lattice strain, indicating changes in crystallinity and structural distortion with FeCo incorporation. The magnetic properties exhibited a strong dependence on the hard–soft phase ratio. With increasing FeCo content, the coercivity decreased from 1795 to 866 Oe, which can be attributed to the increasing contribution of the magnetically soft FeCo phase and its easier magnetization reversal. The differential magnetization (dM/dH) curves displayed a dominant central switching peak accompanied by symmetric secondary features, suggesting the coexistence of different magnetization-reversal processes and supporting the presence of partial exchange coupling between the hard and soft magnetic phases. Furthermore, the effective magnetic anisotropy decreased with increasing FeCo content due to the reduced relative contribution of the high-anisotropy SrFe12O19 phase. Despite the decrease in coercivity, the maximum energy product increased from 0.09 to 0.18 MGOe, demonstrating that appropriate adjustment of the hard-to-soft phase ratio can improve the overall magnetic performance. These findings demonstrate that FeCo incorporation provides an effective approach for balancing saturation magnetization and coercivity, highlighting the potential of SrFe12O19/FeCo nanocomposites as rare-earth-free materials for permanent magnet applications.

Keywords

Permanent Magnets, Partial Exchanged-Coupled, Sol-Gel Autocombustion, Physical Mixing, Maximum Energy Product,

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