Magnetotransport of magnetite nanoparticle arrays

We combine a material self-assembly with conventional lithographic processes in order to fabricate magnetoelectronic devices composed of ordered three-dimensional arrays of magnetite $({\mathrm{Fe}}_{3}{\mathrm{O}}_{4})$ nanoparticles. The device magnetoresistance reaches 35% at 60 K, corresponding to an electron spin polarization of 73%. Magnetoresistance of 12% remains at room temperature. Magnetoresistance decreases with both increasing temperature and bias voltage, however, the magnetoresistance of nanoparticle-based structures is only weakly dependent on the voltage---a favorable attribute for application to electronics.