Half-Metallic Superconducting Triplet Spin MultiValves

Abstract

We study spin switching effects in finite-size superconducting multivalve structures. We examine ${\mathrm{F}}_1{\mathrm{F}}_2\mathrm{S}{\mathrm{F}}_3$ and ${\mathrm{F}}_1{\mathrm{F}}_2\mathrm{S}{\mathrm{F}}_3{\mathrm{F}}_4$ hybrids where a singlet superconductor ($\mathrm{S}$) layer is sandwiched among ferromagnet ($\mathrm{F}$) layers with differing thicknesses and magnetization orientations. Our results reveal a considerable number of experimentally viable spin valve configurations that lead to on-off switching of the superconducting state. For $\mathrm{S}$ widths on the order of the superconducting coherence length ${\xi }_0$, non-collinear magnetization orientations in adjacent $\mathrm{F}$ layers with multiple spin-axes leads to a rich variety of triplet spin-valve effects. Motivated by recent experiments, we focus on samples where magnetizations in the ${\mathrm{F}}_1$ and ${\mathrm{F}}_4$ layers exist in a fully spin-polarized half metallic phase, and calculate the superconducting transition temperature, spatially and energy resolved density of states, and the spin-singlet and spin-triplet superconducting correlations. Our findings demonstrate that superconductivity in these devices can be completely switched on or off over a wide range of magnetization misalignment angles due to the generation of equal-spin and opposite-spin triplet pairings.