Magnetic multilayers in the form of [La0.7Ca0.3MnO3/Al2O3]n+La0.7Ca0.3MnO3 were sputtered to study their magnetotunneling effect. Structural analyses were performed by standard x-ray scattering, showing a well-defined superlattice. Both current perpendicular to plane (CPP) and current in plane (CIP) methods were applied for the magnetoresistance measurements. The CPP value gives the tunneling effect through the thin insulating layers and shows a large low-field effect of about 60% for the trilayer junction and 50% for the superlattice structure at 5 K, respectively. The CIP effect is about 30% (5 K) for all samples and is dominated here by the contribution of the intergrain tunneling effect within the La0.7Ca0.3MnO3 layers.

We have studied magnetic tunnel junctions using an amorphous CoFeNiSiB soft magnetic layer. At room temperature a tunnel-magnetoresistance ratio of 12% was achieved with a switching field of the amorphous layer of 12 Oe. The effect could be enhanced up to 22% by annealing. Investigations on single amorphous layers show a thermal stability up to 350 °C annealing temperature even for very thin layers. Due to the special preparation technique, an in-plane anisotropy is induced resulting from an oblique-incidence effect which presumably affects the short-range order of the amorphous phase.

Three kinds of Co-rich magnetic amorphous films of CoFeB, CoFeNiSiB, and CoFeHfO were prepared by magnetron sputtering and applied as soft ferromagnetic ͑FM͒ electrodes in tunneling magnetoresistance ͑TMR͒ 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 ͑ϳ3-5 Å͒. 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.

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