Bias voltage-dependent low field spin transport properties of Fe3O4–PEG with different particle sizes

Abstract

Spin-dependent transport properties of Fe3O4 spheres with diameters from 200 nm to 900 nm have been investigated and polyethylene glycol (PEG) exists on the surface of Fe3O4 particles. The nonlinear I–V curve became obvious with the increase of Fe3O4 diameter, which indicated the tunneling barrier height decreases with the increasing diameter. The magnetoresistance (MR) can reach −13% with an applied low field of 0.2 T at room temperature. With the diameter increase, the MR decreases and the required applied field increases. Moreover, the decrease of MR with the bias voltage increase can be attributed to the spin-dependent tunneling effect through the insulating surface layer of Fe3O4 and PEG.