A study on the coercivity and the magnetic anisotropy of the lithium ferrite nanocrystallite

Lithium ferrite (LiFe₅O₈) nanocrystallites ranging from several nanometres to several hundreds of nanometres in size have been prepared by the polyethylene glycol gel method. These nanocrystallites were identified as pure lithium ferrite by x-ray diffraction analysis. Their magnetization and de-magnetization were measured by using a vibrating sample magnetometer at different temperatures. The specific saturation magnetization and the coercivities change with the diameter of these nanocrystallites and with temperature. The effective magnetic anisotropy constants K_E of these samples were deduced by using the law of approach to saturation. It is found that the K_E value of a lithium ferrite nanocrystallite of diameter 9.1 nm is about ten times greater than the magnetocrystalline anisotropy constant K₁ of bulk lithium ferrite. The coercivities of these nanocrystallites at different temperatures were calculated by using the mixed coercivity model. The calculated coercivity results are consistent with the experimental ones.