Studies On The Magnetic Properties Of Nano Strontium Ferrite And Its Nanocomposite Magnets Material

M-type Sr-ferrite is a kind of ferrimagnetism oxide, and its resistivity is much higher than the metal magnetic materials. It can be used in microwave absorbing, high-density information magnetic recording media, communication and high frequency equipment, and it promotes the development of science and technology of the microwave electronics, information storage and processing technology and radio electronics rapidly. It becomes an important permanent magnetic material in mordern society. But because it belongs to ferrimagnetism oxide, its saturation magnetization isn’t high enough, and its magnetic properties isn’t superior enough. It is not adapt to mordern devices miniaturization requirements. So developping a series of experimental research to improve its magnetic properties has very important applications.In this paper, we have systematically studied the M-type Sr-ferrite and composite material. We use X-ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscope (SEM), vibration sample magnetometer (VSM) and Quantum Design superconducting quantum interference device (SQUID) to study its structure, morphology and magnetic properties. Our results will be helpful for the investigation and application to improve the M-type Sr-ferrite magnetic properties.The paper is divided into six chapters, and the main content of every chapter is summarized as follows:The first chapter introduces the basic knowledge of magnetism. The nature and classification of the magnetic material and nanocomposite magnets are also introduced briefly. We also introduces the study of the main contents and meaning of this paper.In the second chapter, the author mainly introduces the synthesis and characterization of the M-type Sr-ferrite and nanocomposite magnets.In chapter three, nanocrystalline strontium hexagonal ferrites were synthesized by co-precipitation method. We have systematically studied the effect of the Fe3+/Sr2+mole ratios and annealing temperature on magnetic properties. The experimental results show that the Fe3+/Sr2+mole ratios and annealing temperature influence the phase composition, morphology and magnetic properties of the strontium ferrite powders significantly.In chapter four, we study the magnetic properties of SrFe12O19/γ-Fe2O3nanocomposite magnets. The experimental results show that the hard magnetic phase SrFe12O19and soft magnetic phase y-Fe2O3will appear in samples at annealing temperatures of800℃and900℃.δm(H) show that there are exchange-coupling between SrFe12O19and y-Fe2O3, and this exchange-coupling can improve the magnetic properties of samples. The magneio static interactions become dominant in grains when annealing temperature reaches1000℃In chapter five, we use different three methods to synthesize SrFe12O19/Coo.8Fe2.204nanocomposite magnets, and analyse the effect of different methods on SrFe12O19/Coo.8Fe2.204magnetic properties.In chapter six, the author makes a summary and an outlook.