paper

Nematic versus ferromagnetic spin filtering of triplet Cooper pairs in superconducting spintronics

arXiv:1508.06665 · doi:10.1103/PhysRevB.92.180506

Abstract

We consider two types of magnetic Josephson junctions~(JJ). They are formed by two singlet superconductors~S and magnetic layers between them so that the JJ is a heterostructure of the S/n/S type, where~S includes two magnetic layers with non-collinear magnetization vectors. One layer is represented by a weak ferromagnet and another one---the spin filter---is either conducting strong ferromagnet (nematic or N\nobreakdash-type JJ) or magnetic tunnel barrier with spin-dependent transparency (magnetic or M\nobreakdash-type JJ). Due to spin filtering only fully polarized triplet component penetrates the normal n~wire and provides the Josephson coupling between the superconductors~S. Although both filters let to pass triplet Cooper pairs with total spin~ parallel to the filter axes, the behavior of nematic and magnetic JJs is completely different. Whereas in the nematic case the charge and spin currents,~ and~, do not depend on mutual orientation of the filter axes, both currents vanish in magnetic~JJ in case of antiparallel filter axes, and change sign under reversing the filter direction. The obtained expressions for~ and~ show clearly a duality between the superconducting phase~ and the angle~ between the exchange fields in the weak magnetic layers.

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