Nb-Zn Co-doping cooperative modulating Fe3+ magnetic moment arrangement to enhance the saturation magnetization of strontium ferrite

M-type strontium ferrite (SrFe 12 O 19 ) is widely used in various fields due to its low cost and excellent stability. However, its relatively low saturation magnetization ( M s ) significantly restricts its broader applications. Enhancing M s through non-rare-earth doping via the solid-state reaction method is of significant practical importance. The primary challenge lies in simultaneously maintaining lattice stability and regulating Fe 3+ spin alignment through doping. In this study, a series of non-rare-earth Nb–Zn co-doped SrFe 12- x (Nb a Zn b ) x O 19 ( a : b  = 1:1, a : b  = 4:5, x  = 0.1–0.5) were synthesized using the solid-state reaction method. XRD phase analysis indicated that a single M-type strontium ferrite phase was obtained at the stoichiometric doped ( a:b  = 1:1). In contrast, for the non-stoichiometric doped ( a:b  = 4:5), a trace amount of the secondary phase SrNb 0.5 Fe 0.5 O 3 was detected in Nb–Zn doped samples with x  ≥ 0.2. M s of both stoichiometric and non-stoichiometric doped samples increased within the range of 0≤ x  ≤ 0.3 but gradually decreased when x exceeded 0.3. Notably, for the composition with a : b  = 4:5, M s reached a maximum value of 79.33 emu/g at x  = 0.3, accompanied by a synchronous enhancement of 18.5 % in coercivity ( H c ). Raman spectroscopy analysis revealed the enhancement mechanism of M s : the synergistic occupation of Nb 5+ and Zn 2+ ions. Specifically, Zn 2+ preferentially occupies the 4f 1 tetrahedral sites, while Nb 5+ incorporates into the 4f 2 sites. This co-substitution effectively replaces the spin-down Fe 3+ ions, leading to a significant increase in M s . The presence of a trace amount of the secondary phase SrNb 0.5 Fe 0.5 O 3 in the non-stoichiometrically doped samples, effectively inhibited grain growth, thereby contributing to the enhancement of H c . This study successfully synthesized non-rare-earth-doped strontium ferrite materials via a solid-state reaction method, achieving a significant enhancement in M s . Furthermore, the underlying mechanism for the improvement in M s through Nb–Zn co-doping was elucidated for the first time. Our findings are of significance for the development of high-performance, cost-effective ferrite materials.