Origin of the Inverse Spin Switch Effect in Superconducting Spin Valves

J. Zhu; X. Cheng; C. Boone; I. N. Krivorotov

paper

Origin of the Inverse Spin Switch Effect in Superconducting Spin Valves

arXiv:0903.0044

Abstract

The resistance of a ferromagnet/superconductor/ferromagnet (F/S/F) spin valve near its superconducting transition temperature, $T_{c}$ , depends on the state of magnetization of the F layers. This phenomenon, known as spin switch effect (SSE), manifests itself as a resistance difference between parallel ( $R_{P}$ ) and antiparallel ( $R_{A P}$ ) configurations of the F layers. Both standard ( $R_{P} > R_{A P}$ ) and inverse ( $R_{P} < R_{A P}$ ) SSE have been observed in different superconducting spin valve systems, but the origin of the inverse SSE was not understood. Here we report observation of a coexistence of the standard and inverse SSE in Ni $_{81}$ Fe $_{19}$ /Nb/Ni $_{81}$ Fe $_{19}$ /Ir $_{25}$ Mn $_{75}$ spin valves. Our measurements reveal that the inverse SSE arises from a dissipative flow of vortices induced by stray magnetic fields from magnetostatically coupled Néel domain wall pairs in the F layers.

5 pages, 4 figures