Co/Al2O3/Co magnetic tunnel junctions with an interfacial Cu layer have been investigated with in situ growth characterization and ex situ magnetotransport measurements. Cu interlayers grown on Co give an approximately exponential decay of the tunneling magnetoresistance with xi approximately 0.26 nm while those grown on Al2O3 have a decay length of 0.70 nm. The difference in decay lengths can be explained by different growth morphologies, and in this way clarifies a present disagreement in the literature. For monolayer coverage of Cu, we show that the tunneling spin polarization is suppressed by at least a factor of 2 compared to Co and beyond approximately 5 ML it becomes vanishingly small.
We propose a novel experimental technique for investigating the giant magnetoresistance effect measured with the current perpendicular to the layer plane (the so-called CPP geometry). Using holographic laser interference nanofabrication techniques and anisotropic etching the surface of semi-insulating InP substrates is patterned into V-shaped grooves of 0.2 μm width. Subsequently, a magnetic multilayer can be evaporated under an angle with the substrate normal, naturally resulting in a CPP-like magnetoresistance configuration. The technique is illustrated for Co/Cu multilayers, for which we present magnetization and magnetoresistance experiments.
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