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 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 microand 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 ferromagnetsemiconcuctor contact by domain wall pinning.

Toroidal Order in Magnetic Metamaterials

“…Thus, the energy contribution due to exchange interaction is kept relatively small due to the negligible spin-spin angle on a microscopic scale, whereas the avoidance of magnetisation gradients keeps the magnetostatic energy small. Especially disc-like planar specimens with smooth edges and an aspect ratio close to one allow for the emergence of a magnetic vortex state [197][198][199][200] , see Fig. 2.12.…”

Magnetization reversal of microsized Fe elliptic rings

“…Therefore, the shape and the size of magnetic structures have a strong influence on the switching characteristics [2,[4][5][6][7][8]. In addition, in an array of magnetic elements interaction and correlation effects between need to be considered.…”

Magnetization reversal of equilateral Fe triangles

“…[3][4][5] Furthermore, it is believed that in small magnetic structures the magnetization reversal is dominated by coherent rotation and that reversal by nucleation and domain wall motion is less relevant. 6,7 In addition, in an array of magnetic elements interaction and correlation effects between adjacent magnetic structures need to be considered. Particular attention has also been given to the magnetooptical Kerr effect ͑MOKE͒ properties of periodic arrays of micrometer and submicrometer elements, because the MOKE technique is more sensitive to a diminishing amount of magnetic material than a superconducting quantum interference device SQUID.…”