Magnetic and Structural Investigation of Electrochemically Lithiated Magnetite Nanoparticles

Magnetite Fe₃O₄, a spinel structure (Fd3m), has interesting properties such as room-temperature ferrimagnetism, high Curie temperature, and spin polarization. The reasonable electrical conductivity of magnetite opens the possibility of modifying the saturation magnetization by inserting Li⁺ ions into the structure, in a process similar to that used in conventional lithium batteries. In this study, we have measured the effects of electrochemical lithiation on the structure and magnetic properties of magnetite nanoparticles. A decrease in M_s of up to 75% was observed upon addition of 2 moles of Li per formula unit, along with changes in remanence and coercivity. The insertion of Li⁺ changes the moment by altering both the valence states and the locations of the Fe ions within the structure, and a model is proposed to explain the observations