CoFe2O4和MnFe2O4纳米复合介质的制备及其磁性研究

Synthesis and magnetic properties of CoFe_2O_4 and MnFe_2O_4 nano composites

采用热分解法制备了分散程度高且平均晶粒尺寸为20 nm的CoFe_2O_4和MnFe_2O_4复合介质.低温磁化曲线测量显示,制备的复合介质具有软-硬磁交换弹性耦合效应,且合成温度以及软磁和硬磁相的成分比例对磁交换弹性耦合的强度有很大的影响.变温磁测量显示,温度为20K时,复合纳米介质的表面自旋冻结效应导致饱和磁化强度显著增加.Henkel测量显示,对分散的CoFe_2O_4和MnFe_2O_4复合介质,磁偶极相互作用占主导作用.

Highly dispersed granular nano-composite material of CoFe2O4 and MnFe2O4 with an average size of 20 nm is synthesized through thermal decomposition. The soft-hard magnet exchange-spring effect is observed in magnetization measurements at low temperatures, and is found to be strongly affected by the temperature of the reaction and the composition ratio between soft and hard magnetic phases. Magnetization measurements at different temperatures show that at 20 K, the saturation magnetization increases significantly, which is attributed to the freezing of the spin-glass like state at the surface of the nano-composite material. A Henkel Plot measurement on our sample shows that for the dispersed composite material of CoFe2O4 and MnFe2O4, the dipole interaction is dominant among magnetic interactions.