Optimization of nanostructured permalloy electrodes for a lateral hybrid spin-valve structure

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Ferromagnetic electrodes of a lateral semiconductor-based spin-valve structure are designed to provide a maximum of spin-polarized injection current. A single-domain state in remanence is a prerequisite obtained by nanostructuring Permalloy thin film electrodes. Three regimes of aspect ratios m are identified by room temperature magnetic force microscopy: (i) high-aspect ratios of m ≥ 20 provide the favored remanent single-domain magnetization states, (ii) medium-aspect ratios m 3 to m 20 yield highly remanent states with closure domains and (iii) low-aspect ratios of m ≤ 3 lead to multi-domain structures. Lateral kinks, introduced to bridge the gap between micro- and macroscale, disturb the uniform magnetization of electrodes with high- and medium-aspect ratios. However, vertical flanks help to maintain a uniformly magnetized state at the ferromagnet-semiconcuctor contact by domain wall pinning.