Effect of Zn²⁺ on structure, magnetic properties and thermomagnetic effect of MnZn ferrites

MnZn ferrite nanoparticles were prepared by using sol-gel auto-combustion method. The effect of Zn²⁺ on structure, magnetic properties and thermomagnetic effect were investigated with transmission electron microscope (TEM), X-ray diffractometer (XRD) and vibration sample magnetism analysis system (VSM), etc. The results show that Zn²⁺ has great influence on structure and property of MnZn ferrite. Among the samples prepared, Mn_0.8Zn_0.2Fe₂O₄ possessed the maximal saturation magnetization Ms and thermomagnetic effect. 10 mg these samples led the 1 mL deionized water increase 32°C in 20min under a 60kHz alternating magnetic field, showing the sufficient heating ability. Furthermore, the thermomagnetic effect of MnZn ferrite was adjustable by adjusting Zn²⁺ content. When the Zn²⁺ content increases, the coercive force H_c and remnant magnetization B_r reduce, but the saturation magnetization M_s increases first and reduces subsequently, the maximal M_s to be obtained while the Zn²⁺ content is 0.2, the utmost value is up to 44.6 (A · m²)/kg.