纳米晶Co_(0.8)Fe_(2.2)O_4薄膜的室温和高温结构及磁性

Microstructure and Magnetic Properties of Co_(0.8)Fe_(2.2)O_4 Nanocrystalline Cobalt Ferrite Films at Room and High Temperature

采用溶胶-凝胶旋转包覆法在玻璃衬底上制备了CO0.8Fe2.2O4薄膜.用振动样品磁强计和X射线衍射仪对样品的磁性和结构进行了室温及高温原位测量;用X射线光电子能谱仪和原子力显微镜测量了样品的成分及表面形貌.室温测量结果表明,400%退火时,样品已生成单一的尖晶石相,随退火温度升高衍射峰增高.样品的晶粒尺寸较小（14.2～29.6 nm）,有利于降低磁记录材料的晶界噪音.630%退火样品的矫顽力达到1.56 × 10^5A·m^-1.高温原位测量发现,500%高温时线膨胀系数约为1.3 × 10^-5K^-1,显示样品结构的热稳定性非常好,适合于磁光记录过程.随温度升高,样品由亚铁磁性逐渐过渡到顺磁性.

Co0.8Fe2.2O4 cobalt ferrite films were synthesized on glass substrates by the sol-gel technique. The magnetic properties and microstructure were measured and analyzed by vibrating sample magnetometer and x-ray diffraction at room and high temperature. X-ray photoelectron spectroscopy and atomic force microscope were used to measure the compositions and surface image of the samples. The results at room temperature reveal that the sample annealed at 400℃ has a spinel single-phase, and the increasing annealing temperature yields an increased sharpness of the major peaks. The grain sizes of all samples are smaller （ 14.2 - 29.6nm）, which is propitious to lowering the noise of grain boundary. The coercivity of Co0.8Fe2.2O4 film annealed at 630℃ reaches 1.56×10^5 A·m^-1 . The situ measurements at high temperature show that the coefficient of linear expansion of Co0.8Fe2.2O4 film at 500℃ is about 1.3 ×10^-5 K^-1 , and the microstructures of cobalt ferrite films have good thermal stabilization. This feature is favorable to magneto-optical recording process. With increasing temperature, the samples undergo a transition from ferrimagnetism to paramagnetism.