Magnetic state controllable critical temperature in epitaxial Ho/Nb bilayers

Gu, Yuanzhou; Robinson, Jason W. A.; Bianchetti, Marco; Stelmashenko, Nadia; Astill, D. M.; Grosche, F. M.; MacManus‐Driscoll, Judith L.; Blamire, M. G.

doi:10.1063/1.4870141

Cited by 23 publications

(24 citation statements)

References 32 publications

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“…in T c . This does not agree with the experimental observation in this work.Given the size of this T c effect is generally larger than that reported for spin-valves (and the number of reported cases showing an effect opposite to the spin-valve effect, where the disordered magnetic state results in a higher measured T c[22,[40][41][42]), we urge caution for the interpretation of T c measurements alone as evidence for the presence of the LRTC in S-F systems.With the modelling we have shown that the reported change in T c can be described within the conventional S-F proximity theory by considering the increasing remanence of the Er as a shift in the effective exchange field. This increase in exchange field modifies the proximity effect, suppressing the T c of the bilayer.…”

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confidence: 73%

“…Previous work on holmium and dysprosium demonstrate the important role rare-earth ferromagnets will play in the implementation of superconducting spintronics in Josephson type devices [20,21] and devices based on the control of T c [22,23]. 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].…”

Section: Introductionmentioning

confidence: 99%

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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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confidence: 73%

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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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.…”

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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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“…The antiferromagnetic spiral has a zero net magnetic moment but applying magnetic fields parallel to the basal planes 42,43 induces an irreversible transition to a ferromagnetic state. In epitaxial thin-films, similar properties are reproduced although the antiferromagnetic spiral can remain stable over a wide field range 44 . In textured or polycrystalline thin films the antiferromagnetic spiral can even remain fully reversible even after applying magnetically saturating fields 45 .…”

Section: Introductionmentioning

confidence: 78%

Fraunhofer patterns in magnetic Josephson junctions with non-uniform magnetic susceptibility

Börcsök

Komori

Buzdin

et al. 2019

Sci Rep

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The development of superconducting memory and logic based on magnetic Josephson junctions relies on an understanding of junction properties and, in particular, the dependence of critical current on external magnetic flux (i.e. Fraunhofer patterns). With the rapid development of Josephson junctions with various forms of inhomogeneous barrier magnetism, Fraunhofer patterns are increasingly complex. In this paper we model Fraunhofer patterns for magnetic Josephson junctions in which the barrier magnetic susceptibility is position- and external-magnetic-field dependent. The model predicts anomalous Fraunhofer patterns in which local minima in the Josephson critical current can be nonzero and non-periodic with external magnetic flux due to an interference effect between magnetised and demagnetised regions.

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Magnetic state controllable critical temperature in epitaxial Ho/Nb bilayers

Cited by 23 publications

References 32 publications

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

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

Fraunhofer patterns in magnetic Josephson junctions with non-uniform magnetic susceptibility

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