1. Spin valve effects in superconductor/ferromagnetic devices M.Yu.Kupriyanov, Institute of Nuclear Physics Moscow State University, Moscow, Russia R. G. Deminov Physics Faculty, Kazan State University, 420008 Kazan, Russia Ya. V. Fominov L. D. Landau Institute for Theoretical Physics RAS, 117940 Moscow, Russia A. A. Golubov, Faculty of Science and Technology and MESAInstitute of Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands T. Yu. Karminskaya, Institute of Nuclear Physics Moscow State University, 119992, Moscow, Russia L. R. Tagirov Physics Faculty, Kazan State University, 420008 Kazan, Russia

2. 1. Present experimental status and the main difficulties in practical realization of superconductor spintronic devices. 2. S-(NF)-S and S-(FNF)-S Josephson junctions as the solution of the problems. 3. S-(FNF)-S structures as a novel building block of Josephson spintronics. 4. Conclusion. Outline

3. Peculiarities of proximity effect at SF interfaces. (Long range proximity effect). even in momentum and odd in frequency

4. Spin valve devices 1. Control of Tc due to oscillatory character of singlet and short range triplet correlation. 2. Control of Tc by switching on or off long range triplet correlation. 3. Control of Jc of Josephson junctions due to oscillatory character of singlet and short range triplet correlation. 4. Control of Jc of Josephson junctions by switching on or off long range triplet correlation.

5. Control of Tc due to oscillatory character of singlet and short range triplet correlation. L.R.T., Physica C (1998) M.G. Khusainov, Yu.N. Proshin, PRB (1997) Re-entrant superconductivity in superconductor-ferromagnet bilayers (theory) Experimental observation of the re-entrant superconductivity and double suppression of superconductivity in the Nb/Cu 41 Ni 59 bilayers V.I. Zdravkov, A.S. Sidorenko et al., PRL 97, 057004, 2006. A. S. Sidorenko, et al., Pis’ma ZhETP, 90, 149, 2009. V.I. Zdravkov, J. Kehrle et al., PRB 2009 – accepted for publication

6. SPSP S AP N L. R. T., PRL 83, 2058 (1999); A. I. Buzdin et al., EPL 48, 686 (1999). Ya. V. Fominov, N. M. Chtchelkatchev, and A. A. Golubov, PRB 66, 014507 (2002). A.F. Volkov, F.S. Bergeret and K.B. Efetov, PRL 90, 117006 (2003); Ya.V. Fominov, A. A. Golubov, and M. Yu. Kupriyanov, JETPL 77, 510 (2003) Superconducting short range spin valve (SSRSV)

7. Superconducting long range spin valve (SLRSV) G. Nowak, H. Zabel et al, Phys. Rev. B 78, 134520 2008 T.Yu. Karminskaya, Ya.V. Fominov, A.A. Golubov, M.Yu. Kupriyanov, R.G. Deminov, L.R. Tagirov (unpublished)

8. Idea: S. Oh, D. Youm and M.R. Beasley, APL 71, 2376 (1997). Implementation: I.A. Garifullin, P.V. Leksin et al. (unpublished) Superconducting long range spin valve (SLRSV)

9. Josephson spin valves (theoretical suggestions)

10. The main difficulties in practical realization of superconductor spintronic devices. 1. The decay length and period of Ic oscillations are in nanometer scale. 2. These lengths are comparable with the dead layer thickness at SF interfaces. 3. There are difficulties in changing of orientation of F layers magnetization vectors in SFIFS devices. 4. Contradictoriness of the demands to S layer thickness in FSF control units.

11. The proposed solutions To govern the induced superconductivity rather than self-superconductivity. To increase of   and   by shifting from Н to Н eff T. Yu. Karminskaya and M. Yu. Kupriyanov, Pis’ma Zh. Eksp.Teor. Fiz. 85, 343 (2007) [JETP Lett. 85, 286 (2007)]. T. Yu. Karminskaya and M. Yu. Kupriyanov, Pis’ma Zh. Eksp.Teor. Fiz. 86, 65 (2007) [JETP Lett. 86, 61 (2007_)]. T. Yu. Karminskaya M. Yu. Kupriyanov and A.A.Golubov, Pis’ma Zh. Eksp.Teor. Fiz. 87, 657 (2008) [JETP Lett. 87, 570 (2008)].

12. Dependence of critical current components as a function of distance between superconducting electrodes

13. In S-(FNF)-S Josephson junctions it is possible not only to increase ξ F1 and ξ F2 up to the scale of ξ N, but also to control both the value and the sign of critical current by changing the direction of magnetization of a F layer. L/ ξ N = 0.1 (0 - 0) L/ ξ N = 1 (  - 0 )

14. Deviation of F film magnetization vector from antiferromagnetic configuration is the more effective way for the critical current control.

15. Fundamental wave vectors. There is generation of long range triplet component in the vicinity of angles around . It falls down slowly than the singlet one.

16. Dependence of critical current components as a function of distance between superconducting electrodes

17. Limitations All conclusions have been made under the following limitations 1. Thickness of F and N layers are small in the scale of  N and  F, respectively. 2. The transparency of SF interface must not be too small.

18. S-NF-S junctions with arbitrary values of N and F films thickness and transport properties of NF interface.

19. Expression for the critical current

20. Dependence of the wave vector on thickness of the F layer

21. Dependence of the wave vector on suppression parameter    at FN interface

22. Thickness dependence of the critical current

23. Dependence of the critical current on distance between S electrodes

24. Dependence of the critical current on thickness of F film

25. The I c (L,d F ) phase diagram

26. I c magnitude as a function of distance between S electrodes for different geometry of S-NF-S Josephson junctions

27. I c magnitude as a function of length of weak link region located under S electrodes for different geometry of S-NF-S Josephson junctions

28. I c magnitude as a function of length of weak link region located under S electrodes for different geometry of S-NF-S Josephson junctions junctions

29. Josephson junctions with controlled Tc of S electrode

30. Conclusion We believe that the suggested S-FNF-S Josephson devices opens the way for transformation of the problem of interaction of superconductivity and ferromagnetism from pure fundamental to more practically oriented. - there is no anymore serious limitations on the distance between superconducting electrodes; - the quality of SF interfaces, as well as the problem of dead layer is not important; - the magnitude and sign of the critical current are very robust against a deviation of F and N layers thickness and quality of SF interfaces. - the suggested FNF control unit may be also used for control of critical temperature of superconducting films, as well as Jc of Josephson structures.

31. Thank you for your attention.Thank you for your attention.

32. Математическая постановка задачи

33. Conclusion 1. We have suggested the novel class of S-FN-S and S-FNF-S Josephson devices and have proven theoretically that it is possible to enhance in them the decay length and period of critical current oscillations up to the values (of the order of 100 nm), which are on one or two orders of magnitude larger compare to scale of these lengths having been achieved in recent experimental studies. 2. We have shown that FNF control unit in current in plane geometry is more effectively control the magnitude and sign of Josephson junction critical current rather than FIS and FSF elements in current out of plane geometry. 4. We have shown that the physics of this control lays in generation of long range triplet superconducting correlation, which decays into the weak link even slowly than usual singlet superconductivity. 3. It has been shown that the effective control over the magnitude and sign of I C of the structure is achieved at a small deflection of the vectors M 1, 2 from the antiferromagnetic (M 1 antiparallel to M 2 ) configuration. This is in contrast to the all known spin valve devices, in which the main effect achieved as a result of switching from ferromagnetic to antiferromagnetic aliment of M 1 and M 2.

34. Present experimental status and the main difficulties in practical realization of superconductor spintronic devices. V. I. Zdravkov, A. S. Sidorenko, et al. PRL 97, 057004, 2006 S. L. Prischepa, et al, Pisma Zh. Eksp. Teor. Fiz. 88, 431 (2008) G. Nowak, H. Zabel et al, Phys. Rev. B 78, 134520 2008

35. What is the physics? We have H eff instead of H. An electron for a certain time can be present in the N part of the FN film of the structure. This is equivalent to the subjection of electrons to the effective exchange energy averaged over the thickness of the FN film. This energy is obviously lower than the exchange energy in the ferromagnetic part of the structure. F. S. Bergeret, A. F. Volkov, and K. B. Efetov, Phys. Rev. Lett. 86, 3140 (2001). Ya. V. Fominov, N. M. Chtchelkatchev, and A. A. Golubov, Phys. Rev. B 66, 014507 (2002).

36. Dependence of fundamental wave vectors upon ratio of coupling coefficients between N and F films

39. Characteristic lengths in ferromagnetic materials for SFS Josephson junctions.