Co-rich magnetic amorphous films and their application in magnetoelectronics

Abstract

Three kinds of Co-rich magnetic amorphous films of CoFeB, CoFeNiSiB, and CoFeHfO were prepared by magnetron sputtering and applied as soft ferromagnetic (FM) electrodes in tunneling magnetoresistance (TMR) devices. Initial results exhibit a large room-temperature TMR effect of approximately 50%. The high effect can be attributed to interfacial coherence between the amorphous barrier-electrode layers and, accordingly, suggests a high local spin polarization possibly associated with strong nearest-neighbor spin correlations of the magnetic atoms. The magnetotransport behavior may be governed by details of the local spin environment in magnetic amorphous electrodes due to their short electron mean-free path $(\ensuremath{\sim}3--5\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}})$. The annealing effect on TMR was found to be more pronounced due to the atomic cooperative structural relaxation and more thermally stable compared with the polycrystalline electrode junctions. Additionally, the use of the magnetic oxide electrode CoFeHfO has shown that the relevant FM electrode-barrier interface becomes insensitive to the oxygen, which simplifies the oxidation process used for the oxide barrier fabrication.