LiFe_5O_8纳米晶的矫顽力和磁各向异性

The Coercivity and Magnetic Anisotropy of Lithium Ferrite Nanocrystsllinte

用聚乙二醇（ＰＥＧ）和乙醇溶剂反沉淀法制备颗粒直径９．１～８６０ｎｍ的锂铁氧体纳米晶．Ｘ射线衍射分析表明这些纳米晶是纯ＬｉＦｅ５Ｏ８．用振动样品磁强计测量不同温度下的磁化和退化曲线，得出其比饱和磁化强度和矫顽力随纳米晶颗粒直径和温度的变化．利用趋近饱和定律求出不同温度下，样品的有效各向异性常数ＫＥ，发现颗粒直径为９．１ｎｍ的ＬｉＦｅ５Ｏ８纳米晶的ＫＥ比其大块材料的磁晶各向异性常数Ｋ１几乎增大１０倍．利用均匀转动反磁化和混合矫顽力模型计算纳米晶的不同温度下的矫顽力。

Lithium ferrite (LiFe 5O 8) nanocrystallinte ranging from 9.1￣860 nm in size were prepared using PEG gel method. The nanocrystallite was identified to be pure lithium ferrite by means of X ray diffraction analysis. Their magnetization and demagnetization curves at different temperatures were measured using a vibrating sample magnetometer; the specific saturation magnetization and the coercivity change with the diameter of the nanocrystallinte and temperature have been obtained; the effective magnetic anisotropy constants K E of these samples were deduced using the law of approach to saturation. It is found that the K E value of lithium ferrite nanocrystallintes in 9.1 nm diameter is about ten times greater than the magnetocrystallinte anisotropy constant K 1 of bult lithium ferrite. The coercivities of the nanocrystallinte at different temperatures were calculated using the uniform rotation coercivity theory and the mixed coercivity theory. The calculated coercivity results are consistent with the experimental ones.