Large Superconducting Spin Valve Effect and Ultrasmall Exchange Splitting in Epitaxial Rare-Earth-Niobium Trilayers

Gu, Yuanzhou; Halász, Gábor B.; Robinson, Jason W. A.; Blamire, M. G.

doi:10.1103/physrevlett.115.067201

Cited by 57 publications

(34 citation statements)

References 47 publications

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“…However, when there are two or more F layers with non-collinear exchange fields, as can happen for example in F 1 /F 2 /S structures, S z cannot commute with the Hamiltonian and the m z = ±1 triplet states can also be induced. This is also the case with a single F layer having a non-uniform magnetization texture [18][19][20] . In contrast to the short-range proximityinduced singlet pair amplitudes, these odd m z = ±1 triplet states are usually long ranged [21][22][23][24][25][26][27] in the F layers.…”

Section: Introductionmentioning

confidence: 87%

Transport in ferromagnet/superconductor spin valves

Moen

Valls

2017

Phys. Rev. B

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We consider charge transport properties in realistic, fabricable, Ferromagnet/Superconductor spin valves having a layered structure F 1 /N/F 2 /S , where F 1 and F 2 denote the ferromagnets, S the superconductor, and N the normal metal spacer usually inserted in actual devices. Our calculation is fully self-consistent, as required to ensure that conservation laws are satisfied. We include the effects of scattering at all the interfaces. We obtain results for the device conductance G, as a function of bias voltage, for all values of the angle φ between the magnetizations of the F 1 and F 2 layers and a range of realistic values for the material and geometrical parameters in the sample. We discuss, in the context of our results for G, the relative influence of all parameters on the spin valve properties. We study also the spin current and the corresponding spin transfer torque in F 1 /F 2 /S structures.

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Section: Introductionmentioning

confidence: 87%

Transport in ferromagnet/superconductor spin valves

Moen

Valls

2017

Phys. Rev. B

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“…For example, Gu et al demonstrated that an antiferromagnetic to ferromagnetic transition in Ho resulted in modification of the T c of an adjacent Nb layer of over 100 mK, however the exact mechanism involved in the T c shift was not established [22]. This work was later expanded by producing trilayer samples of Ho/Nb/Ho and Dy/Nb/Dy in which a spin valve like effect of 400 mK was discovered [23]. These works established the ability to control T c with the ferromagnetic texture in rare-earth ferromagnets, however lacked the theoretical description and the additional modification to the shape of the R(T) transition reported in this manuscript.…”

Section: Introductionmentioning

confidence: 99%

Control of Superconductivity with a Single Ferromagnetic Layer in Niobium/Erbium Bilayers

et al. 2017

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Superconducting spintronics in hybrid superconductor-ferromagnet (S-F) heterostructures provides an exciting potential new class of device. The prototypical super-spintronic device is the superconducting spin-valve, where the critical temperature, T c , of the S-layer can be controlled by the relative orientation of two (or more) F-layers. Here, we show that such control is also possible in a simple S/F bilayer. Using field history to set the remanent magnetic state of a thinEr layer, we demonstrate for a Nb/Er bilayer a high level of control of both T c and the shape of the resistive transition, R(T), to zero resistance. We are able to model the origin of the remanent magnetization, treating it as an increase in the effective exchange field of the ferromagnet and link this, using conventional S-F theory, to the suppression of T c . We observe stepped features in the R(T) which we argue is due to a fundamental interaction of superconductivity with inhomogeneous ferromagnetism, a phenomena currently lacking theoretical description. * g.burnell@leeds.ac.uk

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“…It was shown that the optimal operational field for this device is of the order of 20 kOe. Gu et al [10,11] reported ∆T c ∼ 400 mK for Ho/Nb/Ho trilayers. Also in this case the parallel configuration of magnetizations was reached at a field of ∼ 10 kOe.…”

mentioning

confidence: 99%

Isolation of proximity-induced triplet pairing channel in a superconductor/ferromagnet spin valve

et al. 2016

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We have studied the proximity-induced superconducting triplet pairing in CoOx/Py1/Cu/Py2/Cu/Pb spin-valve structure (where Py = Ni0.81Fe0.19).By optimizing the parameters of this structure we found a triplet-channel assisted full switching between the normal and superconducting states. To observe an "isolated" triplet spin-valve effect we exploited the oscillatory feature of the magnitude of the ordinary spin-valve effect ∆Tc in the dependence of the Py2-layer thickness dP y2. We determined the value of dP y2 at which ∆Tc caused by the ordinary spin-valve effect (the difference in the superconducting transition temperature Tc between the antiparallel and parallel mutual orientation of magnetizations of the Py1 and Py2 layers) is suppressed. For such a sample a "pure" triplet spin-valve effect which causes the minimum in Tc at the orthogonal configuration of magnetizations has been observed.The superconducting spin-valve effect consists of different degree of suppression of superconductivity in the F1/F2/S or F1/S/F2 thin film multilayer constructions at parallel (P) and antiparallel (AP) mutual orientation of magnetizations of the F1 and F2 ferromagnetic layers. The superconducting spin valves based on the superconductor/ferromagnet (S/F) proximity effect offer a playground to explore fundamental aspects of interplay between superconductivity and magnetism and also promise applications as passive devices of the superconducting spintronics. The latter construction should be operational upon application of a small external magnetic field. Many experimental works were performed to confirm this effect for the S/F systems with a good contact between metallic F and S layers made of ordinary metals and standard ferromagnets (see, e.g., recent reviews [6]), the full switching between the superconducting and normal states has been realized only in a few cases [7,8] because ∆T c was usually smaller than the width of the superconducting transition δT c .Very recently, Singh et al. reported [9] the observation of a colossal triplet spin-valve effect for the S/F1/N/F2 structure made of amorphous MoGe, Ni, Cu, and CrO 2 as the S, F1, N, and F2 layers, respectively. This structure demonstrated variation of T c by ∼ 1 K when changing the relative alignment of the two F layers. It was shown that the optimal operational field for this device is of the order of 20 kOe. Gu et al. [10,11] reported ∆T c ∼ 400 mK for Ho/Nb/Ho trilayers. Also in this case the parallel configuration of magnetizations was reached at a field of ∼ 10 kOe. The high operational fields of these spin valves are disadvantageous for the superconducting spintronics. Besides, the physical reasons for large values of ∆T c for spin valve based on half-metals are not yet theoretically explained. This calls for elaboration of classical spinvalve structures which use standard ferromagnets (Fe, Co, Ni) and their alloys with good electrical contacts between all layers and for which theoretical understanding of the operational principle is available.Oh et al. [12] propos...

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Large Superconducting Spin Valve Effect and Ultrasmall Exchange Splitting in Epitaxial Rare-Earth-Niobium Trilayers

Cited by 57 publications

References 47 publications

Transport in ferromagnet/superconductor spin valves

Transport in ferromagnet/superconductor spin valves

Control of Superconductivity with a Single Ferromagnetic Layer in Niobium/Erbium Bilayers

Isolation of proximity-induced triplet pairing channel in a superconductor/ferromagnet spin valve

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