The Synthesis Of Ferrimagnetic/Ferromagnetic Core-Shell Nanoparticles And The Investigation Of Their Magnetic Properties

As is known to us, the size distribution, shape and phase purity of nanoparticles as core and shell have an effect on the magnetic properties of core-shell nanocomposite particles. In addition, the magnetic interaction between nanoparticles is also very important. So it is worthwhile to study the magnetic interaction between nanoparticles. In this paper, based on the synthesis of CoFe₂O₄ and NiFe₂O₄ nanoparticles, we study nanocomposite particles with ferrimagnetic/ferromagnetic structure and adjust the magnetic interaction between nanoparticles by controling experimental parameters.Firstly, CoFe₂O₄ and NiFe₂O₄ nanoparticles are synthesized by the coprecipitation method and then CoFe₂O₄/FeCo and NiFe₂O₄/TeNi nanocomposite particles with different core-shell structure are obtained by annealing in hydrogen atmosphere. Then the structure and morphology of the samples are characterized by XRD and TEM, respectively. The results indicate that the samples do not contain impurity phase and the reduction degree of the as-quenched samples increase with the rising of the annealing temperature and time. As a result, the proportion of the reduction phase increase and the core-shell structure become more and more obvious. In addition, the thickness of the shell increase with increasing the annealing time.The basic magnetic properties are performed by VSM. The results indicate that the magnetic hysteresis loops of CoFe₂O₄/FeCo at room temperature show ferromagnetic features.The saturation magnetization increase with the rising of the annealing time and the coercivity reach the maximum at the annealing time of 4h. The magnetic hysteresis loops of NiFe₂O₄/FeNi at room temperature also show ferromagnetic features and the saturation magnetization and coercivity increase with rising the annealing time.The research of the magnetic interactions in samples is carried out by the measurement of isothermal remanent magnetization curve ?IRM? and demagnetization remanent magnetization curve ?DCD?. The results indicate that of the interaction between CoFe₂O₄/FeCo and NiFe₂O₄/FeNi nanocomposite particles, the magnetic dipole interaction is given priority to. Besides, with the increase of annealing time, the magnetic dipole interaction weakened gradually.