Superconducting and magnetic properties of Nb/Pd Fe /Nb triple layers

Schöck, Maya; Sürgers, Christoph; Löhneysen, H. v.

doi:10.1007/s100510050100

Cited by 38 publications

(22 citation statements)

References 24 publications

(43 reference statements)

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“…In addition, for both the samples H c2 (T) shows a linear behavior at T << T c and a nonlinear behavior at T < T c . We identify this result with a 2D-3D crossover, occurring at a characteristic temperature T CR , which has been frequently observed in S and S-F heterostructures [15][16][17] . At lower temperatures, when the coherence length perpendicular to the plane of the film (T) < d s (S-layer thickness) the film behaves like a 3D system.…”

supporting

confidence: 66%

Giant coercivity enhancement and dimensional crossover of superconductivity in Co₂FeSi-NbN nanoscale bilayers

et al. 2013

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Proximity coupling and magnetic switching dynamics are shown to be correlated in bilayers (B) of fully spin polarized ferromagnet (F) Co 2 FeSi and superconductor (S) NbN. The upper critical field derived from resistivity measurements shows a dimensional crossover with a reduced effective thickness of the S layer. At temperatures (T) << superconducting T c , the measured M-H loops show two step switching; one at T-independent value 7 Oe and other at strongly T-dependent value becoming very large 1 kOe at 2 K. These results reveal induced ferromagnetism in S-layer at the S/F interface with vortex pinning influenced dynamics.PACS numbers: 74.45.+c, 74.78.-w, 74.25.Op 2The research field of superconducting (S) and ferromagnetic (F) bilayers (FSB), trilayers and multilayers has gained tremendous importance 1 due to their potential for magnetoeletronics related applications 2 ranging from spin valve to Josephson junctions based devices. The two macroscopic quantum states in S and F layers influence each other via the penetration of superconducting (proximity effect) 2 and ferromagnetic (inverse proximity effect) 3-5 order through their common interface. In presence of strong enough magnetic fields, the vortices in the S-layer can couple with the magnetic domains of the F-layer leading to interesting effects of domain wall pinning of the vortices and vice-a-versa, and domain wall superconductivity [6][7][8][9][10] . Most of such studies have been carried out with ferromagnetic component consisting of 3d transition metals like Fe, Co and Ni, and their alloys. Bilayers of strongly type II superconductors with fully spin polarized ferromagnetic (FSPF) Heusler alloys, which ideally have only one spin state and can potentially show fascinating electronic properties, have not been studied yet. Recently, our group has explored the use of the Co-based Heusler compound (Co 2 MnSi) electrodes for efficient injection of pure spin currents into superconducting NbN 11 . NbN is a type II superconductor of short coherence length ( (0) 5 nm) and long penetration depth ( (0) 200 nm) while Co 2 FeSi (CFS) is a ferromagnet of the Heusler family with high magnetic ordering temperature 1150 K and saturation magnetization 6 µ B per formula unit 12 . In the present work we investigate the nature of proximity coupling and its influence on magnetic switching dynamics in the hitherto unexplored NbN/Co 2 FeSi bilayers grown on (100) MgO.Thin film bilayers of superconducting NbN and CFS were deposited by pulsed laser ablation (PLD). The 35 nm thick NbN film first deposited on MgO at 200 0 C in nitrogen environment by ablating 99.99 % Nb target and then CFS layer of 35 nm thick was grown at the same temperature from a stoichiometric CFS target. To establish the magnetic ordering in CFS film, the FSB sample was annealed at 500 0 C for 1 hour. For comparison, a pure NbN film was also grown during the same PLD run. The other growth parameters for NbN and Co 2 FeSi layers can be found in our previous reports 13,14 . The crystalline quality and interf...

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confidence: 66%

Giant coercivity enhancement and dimensional crossover of superconductivity in Co₂FeSi-NbN nanoscale bilayers

et al. 2013

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“…2) [5]. The value for ξ P d of approximately 60Å that we find with this procedure is comparable with other values reported in literature for similar systems [16] while it is considerably lower than the values found for other normal metals, such as Cu [5,22], and greater than values found for the ferromagnetic ones [1,12,14]. In addition this value, in our temperature range, is in agreement with the one estimated from the measured ρ P d with the expression of ξ P d valid in the dirty limit:…”

Section: Resultssupporting

confidence: 92%

“…The value we obtained, d [5]. The ratio is lower than ours also for Nb/Cu 1−x Ni x , probably due to the little interface transparency of those systems [2,22] [10,16,28] are consistent with these considerations. In this sense a systematic study of the influence of the fabrication method on interface transparency, as already done on Nb/Cu systems [4], would be interesting.…”

Section: Resultssupporting

confidence: 90%

“…A finite transparency gives rise, for example, to a smaller d cr s . This may be due to interface imperfections, lattice mismatches, fabrication method [4,16], but also to intrinsic effects such as difference between Fermi velocities and band-structures of the two metals [13]. The interface transparency due to Fermi velocities mismatches in the free electron model, is given by [1,19]:…”

Section: Theoretical Backgroundmentioning

confidence: 99%

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Interface transparency of Nb/Pd layered systems

Cirillo

Prischepa

Salvato

et al. 2004

The European Physical Journal B - Condensed Matter

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We have investigated, in the framework of proximity effect theory, the interface transparency T of superconducting/normal metal layered systems which consist of Nb and high paramagnetic Pd deposited by dc magnetron sputtering. The obtained T value is relatively high, as expected by theoretical arguments. This leads to a large value of the ratio d cr s /ξ s although Pd does not exhibit any magnetic ordering.

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“…and it depends on both extrinsic (interface imperfections or fabrication methods) [8] and intrinsic factors (difference between Fermi velocities, band-structure and lattice structure of the two metals) [3]. However, when M is magnetic the problem is more complicated due to the role played by the splitting of the spin sub-bands and the spin-dependent impurity scattering [9].…”

Section: Introductionmentioning

confidence: 99%

Interface transparency and proximity effect in Nb/Cu triple layers realized by sputtering and molecular beam epitaxy

Tesauro¹,

Aurigemma²,

Cirillo³

et al. 2004

Supercond. Sci. Technol.

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We have investigated, in the framework of the proximity effect theory, the interface transparency T between Nb and Cu in the case of high quality Nb/Cu trilayers fabricated by molecular beam epitaxy (MBE) and sputtering deposition techniques. The obtained T values do not seem to be strongly influenced by the fabrication methods but more by the intrinsic properties of the two metals; a slightly higher value for T has even been deduced for the MBE prepared samples. The proximity effect in these samples has also been studied in the presence of an external magnetic field. In the parallel configuration a significant shift towards lower values of the 2D-3D crossover temperature has been observed for MBE samples, in good agreement with very recent theoretical predictions. In the perpendicular case a positive curvature of the temperature dependence of the upper critical field has been detected, which was less pronounced for sputtered samples. Both the effects have been observed only for trilayers with low Nb thickness (<600 Å) which confirms the crucial influence of the interface transparency on the values of the upper critical field in such samples.

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Superconducting and magnetic properties of Nb/Pd Fe /Nb triple layers

Cited by 38 publications

References 24 publications

Giant coercivity enhancement and dimensional crossover of superconductivity in Co₂FeSi-NbN nanoscale bilayers

Giant coercivity enhancement and dimensional crossover of superconductivity in Co₂FeSi-NbN nanoscale bilayers

Interface transparency of Nb/Pd layered systems

Interface transparency and proximity effect in Nb/Cu triple layers realized by sputtering and molecular beam epitaxy

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Superconducting and magnetic properties of Nb/Pd Fe /Nb triple layers

Cited by 38 publications

References 24 publications

Giant coercivity enhancement and dimensional crossover of superconductivity in Co2FeSi-NbN nanoscale bilayers

Giant coercivity enhancement and dimensional crossover of superconductivity in Co2FeSi-NbN nanoscale bilayers

Interface transparency of Nb/Pd layered systems

Interface transparency and proximity effect in Nb/Cu triple layers realized by sputtering and molecular beam epitaxy

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Giant coercivity enhancement and dimensional crossover of superconductivity in Co₂FeSi-NbN nanoscale bilayers

Giant coercivity enhancement and dimensional crossover of superconductivity in Co₂FeSi-NbN nanoscale bilayers