In:
Beilstein Journal of Nanotechnology, Beilstein Institut, Vol. 7 ( 2016-07-04), p. 957-969
Abstract:
Background: In nanoscale layered S/F 1 /N/F 2 /AF heterostructures, the generation of a long-range, odd-in-frequency spin-projection one triplet component of superconductivity, arising at non-collinear alignment of the magnetizations of F 1 and F 2 , exhausts the singlet state. This yields the possibility of a global minimum of the superconducting transition temperature T c , i.e., a superconducting triplet spin-valve effect, around mutually perpendicular alignment. Results: The superconducting triplet spin valve is realized with S = Nb a singlet superconductor, F 1 = Cu 41 Ni 59 and F 2 = Co ferromagnetic metals, AF = CoO x an antiferromagnetic oxide, and N = nc-Nb a normal conducting (nc) non-magnetic metal, which serves to decouple F 1 and F 2 . The non-collinear alignment of the magnetizations is obtained by applying an external magnetic field parallel to the layers of the heterostructure and exploiting the intrinsic perpendicular easy-axis of the magnetization of the Cu 41 Ni 59 thin film in conjunction with the exchange bias between CoO x and Co. The magnetic configurations are confirmed by superconducting quantum interference device (SQUID) magnetic moment measurements. The triplet spin-valve effect has been investigated for different layer thicknesses, d F1 , of F 1 and was found to decay with increasing d F1 . The data is described by an empirical model and, moreover, by calculations using the microscopic theory. Conclusion: The long-range triplet component of superconducting pairing is generated from the singlet component mainly at the N/F 2 interface, where the amplitude of the singlet component is suppressed exponentially with increasing distance d F1 . The decay length of the empirical model is found to be comparable to twice the electron mean free path of F 1 and, thus, to the decay length of the singlet component in F 1 . Moreover, the obtained data is in qualitative agreement with the microscopic theory, which, however, predicts a (not investigated) breakdown of the triplet spin-valve effect for d F1 smaller than 0.3 to 0.4 times the magnetic coherence length, ξ F1 .
Type of Medium:
Online Resource
ISSN:
2190-4286
Language:
English
Publisher:
Beilstein Institut
Publication Date:
2016
detail.hit.zdb_id:
2583584-1
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