Change in the magnetic moment of a ferromagnetic nanoparticle under polarized current

The magnetization reversal of a ferromagnetic Fe 3 O 4 nanoparticle with a volume of the order of several thousands of cubic nanometers under the influence of spin-polarized current has been investigated on a high-vacuum scanning tunneling microscope, where one of the electrodes is a magnetized iron wire needle and the second electrode is a ferromagnetic nanoparticle on a graphite substrate. The measured threshold current of magnetization reversal, i.e., the lowest value of the current corresponding to the magnetization reversal, is found to be I thresh ≈ 9 nA. A change in the magnetization of a nanoparticle is revealed using the giant magnetoresistance effect, i.e., the dependence of the weak polarized current ( I < I thresh ) on the relative orientation of the magnetizations of the electrodes.