Half-metallic Fe3O4 films for high-sensitivity magnetoresistive devices

By RF sputtering on a MgO [100] substrate, we have made Fe₃O₄ [111] metal and Fe₃O₄ [001]/TiN [001] films that have Verwey temperature (T_V) near 120 K. The saturation magnetizations and resistivities of those Fe₃O₄ films were comparable to those of bulk Fe₃O₄, and the magnetoresistive (MR) ratio and MR ratio area product AΔR measured for various materials structures of current perpendicular to plane (CPP) samples using Fe₃O₄ [111] increased sharply at 120 K. This increase around T_V seemed to be related to the change in the Fe₃O₄ crystal. The AΔR and MR of CPP-GMR samples using Fe₃O₄ [001], on the other hand, such as Ni₈₀Fe₂₀/TiN/Fe₃O₄ [001]/TiN [001], Co₇₅Fe₂₅/TiN/Fe₃O₄ [001]/TiN [001], and Fe₃O₄/TiN/Fe₃O₄ [001]/TiN [001], were 2-4 times larger than those of CPP-GMR samples using Fe₃O₄ [111] were. And for Fe₃O₄ [001] the increase of MR at T_V was smaller than it was for Fe₃O₄ [111].