Observation of standard spin-switch effects in F/S/F trilayers with a strong ferromagnet

TL;DR

This study investigates the superconducting transition temperature in F/S/F trilayers with a strong ferromagnet, revealing spin-switch effects consistent with some prior results but opposite to recent findings.

Contribution

It demonstrates the observation of standard spin-switch effects in F/S/F trilayers using Permalloy, highlighting the influence of ferromagnet strength on superconductivity suppression.

Findings

Superconducting transition temperature varies with magnetization alignment.

Stronger suppression of T_c in parallel alignment compared to anti-parallel.

Results align with earlier studies on similar ferromagnetic materials.

Abstract

We have measured the superconducting transition temperature T_c of F/S/F trilayers using Permalloy (Py=Ni_84 Fe_16) as a strongly polarized ferromagnetic material. For a parallel (P) or anti-parallel (AP) alignment of the magnetization directions of the outer ferromagnets, we observe a T_c difference as large as 20 mK, with a stronger suppression of superconductivity in the P state than in the AP state. This behavior is opposite to the recent observations of Rusanov et al., Phys. Rev. B 73, 060505 (2006) in Py/Nb/Py trilayers, but is consistent with earlier results on trilayers with Ni or CuNi alloy as the ferromagnetic material.