Iron-based soft magnetic composites with Mn–Zn ferrite nanoparticles coating obtained by sol–gel method

• Published in: Journal of magnetism and magnetic materials Vol. 324; no. 22; pp. 3899 - 3905
• Main Authors: Wu, Shen, Sun, Aizhi, Xu, Wenhuan, Zhang, Qian, Zhai, Fuqiang, Logan, Philip, Volinsky, Alex A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.11.2012; Elsevier
• Subjects: Annealing; Annealing treatment; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Domain effects, magnetization curves, and hysteresis; Exact sciences and technology; Ferrite; Iron; Magnetic permeability; Magnetic properties and materials; Magnetization curves, magnetization reversal, hysteresis, barkhausen and related effects; Manganese; Mn–Zn ferrite; Particulate composites; Permeability; Physics; Soft magnetic composite; Sol gel process; Soft magnetic composite; Permeability; Annealing treatment; Mn–Zn ferrite; Scanning electron microscopy; Crystalline phase; Annealing; Electrical conductivity; Epoxy resin; Magnetic hysteresis; Iron Manganese Zinc Oxides Mixed; Soft magnetic materials; Dispersive spectrometry; Heat treatments; Ferrites; Composite materials; Iron loss; Magnetic permeability; Mn-Zn ferrite; Sol-gel process; Nanocrystal
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2012.06.042

This paper focuses on iron-based soft magnetic composites which were synthesized by utilizing Mn–Zn ferrite nanoparticles to coat iron powder. The nanocrystalline iron powders, with an average particle diameter of 20nm, were obtained via the sol–gel method. Scanning electron microscopy, energy dispersive X-ray spectroscopy and distribution maps show that the iron particle surface is covered with a thin layer of Mn–Zn ferrites. Mn–Zn ferrite uniformly coated the surface of the powder particles, resulting in a reduced imaginary permeability, increased electrical resistivity and a higher operating frequency of the synthesized magnets. Mn–Zn ferrite coated samples have higher permeability and lower magnetic loss when compared with the non-magnetic epoxy resin coated compacts. The real part of permeability increases by 33.5% when compared with the epoxy resin coated samples at 10kHz. The effects of heat treatment temperature on crystalline phase formation and on the magnetic properties of the Mn–Zn ferrite were investigated via X-ray diffraction and a vibrating sample magnetometer. Ferrites decomposed to FeO and MnO after annealing above 400°C in nitrogen; thus it is the optimum annealing temperature to attain the desired permeability. ► Uniformly coated Mn–Zn ferrite powder increased the operating frequency of SMCs. ► Compared with epoxy coated, the permeability of SMCs increased by 33.5% at 10kHz. ► 400°C is the optimum annealing temperature to attain the desired permeability.