Fabrication and magnetoresistive effect of current perpendicular to plane devices using half-metallic Fe3O4 thin films on metallic films

The current-perpendicular-to-plane giant magnetoresistive (CPP-GMR) devices having half-metallic Fe3O4 for their magnetic layers were investigated along with the fabrication of Fe3O4 films on Au layers at low temperature (523 K). The 10–50-nm-thick Fe3O4 films that were grown on a 100 nm Au (111) layer were Fe3O4 (111) oriented. These films showed Verwey transition at ∼120 K. Using these films, the relation between the magnetoresistive (MR) effect of CPP-GMR and the Fe3O4 layer thickness was examined with 2×2 μm2 samples of Ni80Fe20/Au/Fe3O4 trilayers on Au bottom electrode films. At the Fe3O4 layer thickness of 20 nm, the MR ratio was 0.04% and the area magnetoresistance-change product (ΔRA) was 1.5 mΩ μm2. The MR ratio was increased with decrease in the Fe3O4 thickness. The CPP-GMR of Fe3O4/Au/Fe3O4 on the Au layer showed that the MR ratio was 0.04% and the ΔRA was 3.9 mΩ μm2. This MR ratio was four times larger than that of the NiFe-type CPP-GMR for the same Fe3O4 bottom layer thickness.