Superconducting exchange coupling between ferromagnets.

Recent discoveries from superconductor (S)/ferromagnet (FM) heterostructures include π-junctions, triplet pairing, critical temperature (Tc) control in FM/S/FM superconducting spin valves (SSVs) and critical current control in S/FM/N/FM/S spin valve Josephson junctions (N: normal metal). In all cases, the magnetic state of the device, generally set by the applied field, controls the superconducting response. We report here the observation of the converse effect, that is, direct superconducting control of the magnetic state in GdN/Nb/GdN SSVs. A model for an antiferromagnetic effective exchange interaction based on the coupling of the superconducting condensation energy to the magnetic state can explain the Nb thickness and temperature dependence of this effect. This superconducting exchange interaction is fundamentally different in origin from the various exchange coupling phenomena that underlie conventional spin electronics (spintronics), and provides a mechanism for the active control of the magnetic state in superconducting spintronics.

[1]  M. Blamire,et al.  Suppression of magnetic coupling in superconducting GdN-NbN-GdN trilayers , 2013 .

[2]  J. Pearson,et al.  Magnetization-orientation dependence of the superconducting transition temperature in the ferromagnet-superconductor-ferromagnet system: CuNi/Nb/CuNi. , 2002, Physical review letters.

[3]  M. Blamire,et al.  Magnetic exchange hardening in polycrystalline GdN thin films , 2010, Journal of physics. Condensed matter : an Institute of Physics journal.

[4]  J. Slonczewski.  Origin of biquadratic exchange in magnetic multilayers (invited) , 1993 .

[5]  J. Aarts,et al.  Coupling of Two Superconductors through a Ferromagnet , 2001 .

[6]  T. Khaire,et al.  Observation of spin-triplet superconductivity in Co-based Josephson junctions. , 2009, Physical review letters.

[7]  M. Blamire,et al.  Large Superconducting Spin Valve Effect and Ultrasmall Exchange Splitting in Epitaxial Rare-Earth-Niobium Trilayers. , 2015, Physical review letters.

[8]  Etienne,et al.  Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices. , 1988, Physical review letters.

[9]  C. S. D. Melo,et al.  MAGNETIC EXCHANGE COUPLING IN FERROMAGNET/SUPERCONDUCTOR/FERROMAGNET MULTILAYERS , 1997 .

[10]  Margaret Evans Best,et al.  Antiferromagnetically coupled magnetic media layers for thermally stable high-density recording , 2000 .

[11]  M. G. Blamire,et al.  Controllable Josephson current through a pseudospin-valve structure , 2004 .

[12]  P. Gennes.  Coupling between ferromagnets through a superconducting layer , 1966 .

[13]  M. Blamire,et al.  Pure second harmonic current-phase relation in spin-filter Josephson junctions. , 2014, Nature communications.

[14]  Schreiber,et al.  Layered magnetic structures: Evidence for antiferromagnetic coupling of Fe layers across Cr interlayers. , 1986, Physical review letters.

[15]  L. Tagirov.  LOW-FIELD SUPERCONDUCTING SPIN SWITCH BASED ON A SUPERCONDUCTOR/FERROMAGNET MULTILAYER , 1999 .

[16]  Kirk,et al.  Extreme critical-temperature enhancement of Al by tunneling in Nb/AlOx/Al/AlOx/Nb tunnel junctions. , 1990, Physical review letters.

[17]  Bethany M. Niedzielski,et al.  Controllable 0–π Josephson junctions containing a ferromagnetic spin valve , 2016 .

[18]  J. Moodera,et al.  Superconducting spin switch with infinite magnetoresistance induced by an internal exchange field. , 2013, Physical review letters.

[19]  M. G. Blamire,et al.  Controlled Injection of Spin-Triplet Supercurrents into a Strong Ferromagnet , 2010, Science.

[20]  M. Blamire,et al.  Spin-filter Josephson junctions. , 2011, Nature materials.

[21]  J. Witt,et al.  Irreversible magnetization switching at the onset of superconductivity in a superconductor ferromagnet hybrid , 2015 .

[22]  C. Chappert,et al.  Oscillatory coupling between ferromagnetic layers separated by a nonmagnetic metal spacer. , 1991, Physical review letters.

[23]  Jacob Linder,et al.  Superconducting spintronics , 2015, Nature Physics.

[24]  B. L. Gyorffy,et al.  Oscillatory magnetic coupling between metallic multilayers across superconducting spacers , 1995 .

[25]  Berger,et al.  Magnetoresistivity and oscillatory interlayer magnetic coupling of sputtered Fe/Nb superlattices. , 1992, Physical review letters.

[26]  Ralph,et al.  Current-driven magnetization reversal and spin-wave excitations in Co /Cu /Co pillars , 1999, Physical review letters.

[27]  T. Van Duzer,et al.  Principles of Superconductive Devices and Circuits , 1981 .

[28]  W. Meiklejohn,et al.  New Magnetic Anisotropy , 1956 .

[29]  Klein,et al.  Electronic properties of transition-metal nitrides: The group-V and group-VI nitrides VN, NbN, TaN, CrN, MoN, and WN. , 1985, Physical review. B, Condensed matter.

[30]  Burm Baek,et al.  Hybrid superconducting-magnetic memory device using competing order parameters. , 2013, Nature communications.