Study Of Super-paramagnetic Property Of Nano-rare Earth Ferrite Magnetic Particles

Nano-Fe3O4 magnetic particles are an important functional nano-material, with the mesoscopic characteristic of nano-material in physic, chemistry. Meanwhile, the particles have their special magnetic properties-mesoscopic magnetism in the external magnetic field. Nano-Fe3O4 magnetic particles have been usually used in magnetic recording material, catalytic material, absorbing material, magnetic fluid and bio-medical for their special physical and magnetic properties. Recently, nano magnetic particles have a great deal of attention on the modification, as the requirement of physical and magnetic properties increasing.The paper explained that the Dy, Y-ferrite were prepared by wet chemical methods with FeSO4·7H2O, Fe2(SO4)3·xH2O, and Dy(NO3)3·xH2O, NaOH as raw materials and the results were studyed. To prevent it agglomeration in dry,the magnetic particles were modified by lauric acid. The magnetic properties and the superparamagnetism of the Dy-ferrite magnetic nanoparticles were studied at different temperature, and the magnetic properties of the particles were compared in similar size at room temperature. The morphology and size of the magnetic particles were observed by transmission electron microscope(TEM) after surface modification; The crystalline structure of magnetic nanoparticles were analysis by X-ray diffraction(XRD); The phase and surface chemical environment of the magnetic nanoparticles were measured by Fourier transform infrared spectrometer(FT-IR); The magnetic properties of Dy-ferrite were measured by Superconducting magnetic measuring instrument(SQUID) after surface modification. The TEM photos show that the Dy Y-ferrite particles are mainly for spherical, the average size of Dy-ferrite is about 20.78nm and 17.8nm, the average size of Y-ferrite is about 20.4nm. The XRD pictures show that Dy, Y-ferrite magnetic nanoparticles are the main phase of Fe3O4, FCC spinel-type structure, and high crystallinity. The FT-IR picture shows that the particles have changed the surface chemistry environment, and these have a strong chemical effect between the particles and the surfactant. The magnetic hysteresis loop shows that with the temperature increasing, the magnetization, residual magnetization and the coercivity of Dy-ferrite magnetic nanoparticles decrease, the magnetic particles are superparamagnetism; The Dy-ferrite magnetic particles are better than Y-ferrite by the magnetic properties in room temperature.