Spin-Dependent Cooper Pair Phase and Pure Spin Supercurrents in Strongly Polarized Ferromagnets

We study heterostructures of singlet superconductors and strongly spin-polarized ferromagnets and show that a relative phase arises between the superconducting proximity amplitudes in the two ferromagnetic spin bands. We find a tunable pure spin supercurrent in a spin-polarized ferromagnet contacted with only one superconductor electrode. We show that Josephson junctions are most effective for a spin polarization P approximately 0.3, and that critical currents for positive and negative bias differ for a high transmission Josephson junction, due to a relative phase between single and double pair transmission.