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

Abstract

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 nanopatterning 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–m∼20 yield highly remanent states with closure domains, and (iii) low-aspect ratios of m⩽3 lead to multidomain structures. Lateral kinks, introduced to bridge the gap between microscale and macroscale, disturb the uniform magnetization of electrodes with high- and medium-aspect ratios. However, sloped regions (vertical flanks) help to maintain a uniformly magnetized state at the ferromagnet-semiconductor contact by domain wall pinning.