Angular Dependence of the Superconducting Transition Temperature in Ferromagnet-Superconductor-Ferromagnet Trilayers

Zhu, Jianguo; Krivorotov, I. N.; Halterman, Klaus; Valls, Oriol T.

doi:10.1103/physrevlett.105.207002

Cited by 87 publications

(104 citation statements)

References 28 publications

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“…As we demonstrate in the analysis section of this paper, this minimum in T c arises from the enhanced long-range triplet pair amplitude in the maximally noncollinear configuration of the spin valve. We also note that our previous studies of the angular dependence of T c in NiFe/Nb/NiFe trilayers [32] found monotonic dependence of T c on α in the 0 to π range, which serves as indication of a much weaker triplet pair amplitude induced in the system with two ferromagnetic layer separated by a superconductor. This dependence is weak, which implies that (i) the pair amplitude decays slowly in the Cu spacer layer and (ii) the pair amplitude decays to nearly zero over the pinned layer thickness greater than 1.5 nm (the thinnest pinned layer employed in our studies).…”

Section: Angular Dependence Of T Csupporting

confidence: 54%

Angular dependence of superconductivity in superconductor/spin-valve heterostructures

et al. 2014

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We report measurements of the superconducting transition temperature, T c , in CoO/Co/Cu/Co/Nb multilayers as a function of the angle α between the magnetic moments of the Co layers. Our measurements reveal that T c (α) is a nonmonotonic function, with a minimum near α = π/2. Numerical self-consistent solutions of the Bogoliubov-de Gennes equations quantitatively and accurately describe the behavior of T c as a function of α and layer thicknesses in these superconductor / spin-valve heterostructures. We show that experimental data and theoretical evidence agree in relating T c (α) to enhanced penetration of the triplet component of the condensate into the Co/Cu/Co spin valve in the maximally noncollinear magnetic configuration.

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Section: Angular Dependence Of T Csupporting

confidence: 54%

Angular dependence of superconductivity in superconductor/spin-valve heterostructures

et al. 2014

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“…5,6 In this state, the real part of the order parameter penetrates the ferromagnet a distance on the order of the coherence length ξ F and oscillates due to dephasing by the exchange energy of the ferromagnet. This leads to the oscillations of the superconducting transition temperature (T c ) as a function of ferromagnet thickness [7][8][9][10][11] and π phase shift in S/F junctions. 12,13 Furthermore, recent measurements in S/F structures 11,[14][15][16] have provided evidence for triplet pairing in the ferromagnet induced by noncollinear magnetizations of the F layers.…”

Section: Introductionmentioning

confidence: 99%

Vortex flipping in superconductor/ferromagnet spin-valve structures

et al. 2013

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We report in-plane magnetization measurements on Ni/Nb/Ni/CoO and Co/Nb/Co/CoO spin valve structures with one of the ferromagnetic layers pinned by an antiferromagnetic layer. In samples with Ni below the superconducting transition T c , our results show strong evidence of vortex flipping driven by ferromagnet magnetization. This is a direct consequence of the proximity effect that leads to vortex supercurrent leakage into the ferromagnets. Here, the polarized electron spins are subject to the vortices' magnetic field, occasioning vortex flipping. Such a novel mechanism has been made possible by fabrication of the ferromagnet/superconductor/ferromagnet/antiferromagnet multilayered spin valves with an S layer thin enough to barely confine vortices inside as well as F layers thin enough to align and control magnetization within the plane. When Co is used, the vortex flipping effect is not observed. This is attributed to the shorter coherence length of Co. Interestingly, a reduction in the pinning field of about 400 Oe is observed instead when the Nb layer is in the superconducting state. This effect cannot be explained in terms of vortex fields. In view of these facts, any explanation must be directly related to the proximity effect and thus a remarkable phenomenon that deserves further investigation.

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“…T c reaches minimum if the relative magnetization is parallel and maximum for antiparallel magnetization. 27 A different behavior was observed for the FM/FM/SC nanostructures for which the critical temperature is minimized in case of perpendicular alignment of the magnetization.…”

Section: -21mentioning

confidence: 99%

Tunneling conductance through the half-metal/conical magnet/superconductor junctions in the adiabatic and non-adiabatic regimes: Self-consistent calculations

Wójcik

Zegrodnik

Rzeszotarski

et al. 2016

Physica E: Low-dimensional Systems and Nanostructures

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The tunneling conductance in the half-metal/conical magnet/superconductor (HM/CM/SC) is investigated by the use of the combined Blonder-Tinkham-Klapwijk (BTK) formalism and the Bogoliubov-de Gennes (BdG) equations. We show that the conductance calculated self-consistently differs significantly from the one calculated in the non-self-consistent framework. The use of the self-consistent procedure ensures that the charge conservation is satisfied. Due to the spin band separation in the HM, the conductance in the subgap region is mainly determined by the anomalous Andreev reflection the probability of which strongly depends on the spin transmission in the CM layer. We show that the spin of electron injected from the HM can be transmitted through the CM to the SC adiabatically or non-adiabatically depending on the period of the exchange field modulation. We find that the conductance in the subgap region oscillates as a function of the CM layer thickness wherein the oscillations transform from irregular, in the non-adiabatic regime, to regular in the adiabatic case. In the non-adiabatic regime the decrease of the exchange field amplitude in the CM leads to the emergence of the conductance peak for one particular CM thickness in agreement with experiment [J.W.A Robinson, J. D. S Witt and M. G. Blamire, Science 329, 5987]. For both transport regimes the conductance is analyzed over a broad range of parameters determining the spiral magnetization in the CM.

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Angular Dependence of the Superconducting Transition Temperature in Ferromagnet-Superconductor-Ferromagnet Trilayers

Cited by 87 publications

References 28 publications

Angular dependence of superconductivity in superconductor/spin-valve heterostructures

Angular dependence of superconductivity in superconductor/spin-valve heterostructures

Vortex flipping in superconductor/ferromagnet spin-valve structures

Tunneling conductance through the half-metal/conical magnet/superconductor junctions in the adiabatic and non-adiabatic regimes: Self-consistent calculations

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