Competition between the superconducting spin-valve effect and quasiparticle spin-decay in superconducting spin-valves

Abstract

<jats:title>Abstract</jats:title><jats:p>In a ferromagnet/normal metal/ferromagnet spin-valve, spin dependent scattering causes a difference in resistance between antiparallel (AP) and parallel (P) magnetization states. The resistance difference, Δ<jats:italic>R</jats:italic> = <jats:italic>R</jats:italic>(<jats:italic>A</jats:italic><jats:italic>P</jats:italic>) − <jats:italic>R</jats:italic>(<jats:italic>P</jats:italic>) is positive due to increased scattering of majority and minority spin-electrons in the AP-state. If the normal metal is substituted for a superconductor, the superconducting spin-valve effect occurs: in the AP-state the net magnetic exchange field acting on the superconductor is lowered and the superconductivity is reinforced meaning <jats:italic>R</jats:italic>(<jats:italic>A</jats:italic><jats:italic>P</jats:italic>) decreases. For current-perpendicular-to-plane spin-valves, existing experimental studies show that the normal state effect dominates (Δ<jats:italic>R</jats:italic> &gt; 0) over the superconducting spin valve effect (Δ<jats:italic>R</jats:italic> &lt; 0). Here however, we report a crossover from giant magnetoresistance (Δ<jats:italic>R</jats:italic> &gt; 0) to the superconducting spin-valve effect (Δ<jats:italic>R</jats:italic> &lt; 0) in current-perpendicular-to-plane ferromagnet/superconductor/ferromagnet spin-valves as the superconductor thickness decreases below a critical value.</jats:p>