Synergistic optimization mechanism of microstructure and magnetic properties in M-type strontium ferrite via Ce/La co-doping and pre-sintering temperature regulation
Driven by the urgent demand for green and low-carbon technologies, the development of high-performance and cost-effective rare-earth free permanent magnets has emerged as a key research focus for sustainable energy and advanced electronic applications. Among various candidates, M-type strontium ferrites have attracted considerable attention due to their excellent thermal stability, high magnetocrystalline anisotropy, and abundant raw material availability. In this study, Sr0.41La0.36Ca0.23Fe11.8Co0.2O19 was selected as the base system, and a series of samples were synthesized via a solid-state reaction combined with high-energy ball milling. The synergistic effects of varying CeO2/La2O3 mass ratios (0:10 to 10:0) and pre-sintering temperatures (1150-1200°C) on the microstructure and magnetic properties were systematically investigated. Microstructural analyses revealed that moderate Ce substitution effectively induced controlled lattice distortion and promoted densification, which inhibited abnormal grain growth and refined the microstructure. Such structural modulation not only enhanced domain wall pinning but also improved magnetocrystalline anisotropy, leading to a remarkable increase in coercivity. Magnetic measurements confirmed that the composition with a CeO2/La2O3 mass ratio of 2:8 and pre-sintered at 1180°C achieved the most balanced magnetic performance, exhibiting enhanced coercivity, sufficient remanence, and stable saturation magnetization. This work provides new insights into the cooperative effects between rare-earth doping ratios and thermal processing parameters, clarifying how lattice defects, grain boundary characteristics, and microstructural evolution collectively govern the magnetic properties of M-type ferrites. The findings establish a practical strategy for tailoring the microstructure-property relationship in rare-earth free permanent magnets, opening an optimized processing window for scalable fabrication of environmentally friendly, high-performance ferrite materials.