Spin-valve behavior in porous alumina-embedded carbon nanotube array with cobalt nanoparticle spin injectors

We report the operation of spin-valve structures formed from arrays of aligned carbon nanotubes grown and embedded in porous anodized aluminum oxide. The devices incorporate cobalt nanoparticles acting as both a ferromagnetic layer and carbon nanotube array-growing catalysts, requiring only one deposited ferromagnetic layer as the other magnetic electrode. A peak in the resistance occurs clearly as a result of the reversal of the magnetization of the electrodes. Device magnetoresistance ratios reach 1.5% at 40 K, yielding an estimate of the maximum spin scattering length of 2 μm at temperatures up to 40 K. This device architecture presents not only an opportunity for massively parallel patterned circuits with devices the size of an individual nanotube diameter, but also the potential for multi-state switching devices with the selective incorporation of various ferromagnetic catalyst nanoparticles of different coercive fields within the same porous anodized aluminum oxide array.