Magnetic and structural investigation of electrochemically lithiated magnetite nanoparticles

Magnetite Co[Fe.sub.3][O.sub.4], 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.sup.+] 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.sub.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.sup.+] 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. Index Terms--Ferrimagnetic, magnetite, nanoparticles, spinel.