CoFe_2与CoFe_2O_4质量比及MgO稀释对CoFe_2@CoFe_2O_4磁性的影响

Effects of mass ratio of CoFe_2 to CoFe_2O_4 and the dilution by MgO on the magnetic properties of CoFe_2@CoFe_2O_4

采用金属有机盐热分解方法制备了MgO包覆的CoFe_2O_4纳米粒子(CoFe_2O_4@MgO),然后将CoFe_2O_4@MgO在H_2中还原,接着在空气中氧化制备了一组CoFe_2@CoFe_2O_4@MgO样品;用盐酸溶液溶解CoFe_2@CoFe_2O_4@MgO中的MgO获得另一组样品(CoFe_2@CoF_2O_4)。测量并绘制了CoFe_2@CoFe_2O_4@MgO和CoFe_2@CoF_2O_4的磁化强度随外磁场及温度变化的关系曲线。随着氧化温度升高,CoFe_2@CoFe_2O_4@MgO和CoFe_2@CoF_2O_4的矫顽力Hc、饱和磁化强度Ms、剩磁比Mr/Ms及磁有序状态发生显著变化,这些变化强烈依赖于磁性粒子的各向异性及粒子间的偶极相互作用。

MgO coated CoFe2O4 nanoparticles（CoFe2O4@MgO）were synthesized by the thermal decomposition of a metal-organic salt.CoFe2O4@ MgO was reduced in H2 and then oxidized in air to prepare a group of CoFe2 @CoFe2O4@ MgO samples.Then MgO was dissolved by the HCl solution to obtain the other group of samples（CoFe2@CoFe2O4）.The magnetic field and temperature dependent magnetization curves were measured on CoFe2@CoFe2O4 and CoFe2@CoFe2O4@MgO samples.The significant changes of coercivity Hc,saturation magnetization Msand remanence ratio Mr/Msas well as the magnetic ordering states with the oxidation temperature are observed for CoFe2@CoFe2O4 and CoFe2@CoFe2O4@MgO samples,which strongly depend on the anisotropy of the magnetic particles and interparticle dipolar interaction.