Depairing currents in the superconductor/ferromagnet proximity system Nb/Fe

Geers, J.M.E.; Hesselberth, M.B.S.; Aarts, J.; Golubov, Alexandre Avraamovitch

doi:10.1103/physrevb.64.094506

Cited by 56 publications

(65 citation statements)

References 25 publications

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“…This is not unexpected. In earlier work on the system Nb/ Fe, 16 we found that, in the Ginzburg-Landau ͑GL͒ regime close to T c , 27 J dp can be described as function of reduced temperature t = T / T c by the well-known expression J dp GL ͑t͒ = J dp GL ͑0͒͑1 − t͒ 3/2 , ͑1͒ also in the case that the order parameter is not constant over the thickness of the superconducting film. As a first step in the analysis, following Eq.…”

Section: Depairing Currentsmentioning

confidence: 90%

“…21 The first issue requires samples with a bridge width w comparable with the penetration depth and the coherence length of the superconductor, respectively. Recent results 16,22 on Nb and MoGe single films and Fe/ Nb/ Fe trilayers, however, give us reason to expect uniform current distributions for w Ϸ 1.5 m. A classical pseudo-4-point geometry ͑meaning two contacts, each used for a current and a voltage lead͒ was defined using e-beam lithography. The structuring process, consisting of two main stages ͑e-beam writing and argon-ion etching͒, provided sharp-edged bridges.…”

Section: Methodsmentioning

confidence: 99%

“…A simple advantage of J dp over T c is that, where T c probes the maximum value of the superconducting order parameter in the sample, J dp comes from an average over the layer thickness, which also involves lower values of ⌿. 16 The aims of this work are to probe the inhomogeneous character of the superconducting order parameter in bilayers of Nb and Pd 81 Ni 19 and to directly compare the information from T c and J dp upon varying the PdNi layer thickness d PdNi . The paper is organized as follows.…”

Section: Introductionmentioning

confidence: 99%

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Depairing current behavior in superconductingNb∕Pd81Ni19bilayers

et al. 2007

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We have investigated superconductor/ferromagnetic bilayers consisting of Nb/ Pd 81 Ni 19 with varying thickness of the ferromagnet ͑F͒ layer d F in order to compare the behavior of the superconducting transition temperature T c with that of the depairing current density J dp . For T c ͑d F ͒, we find the usual behavior, with a minimum around d F = 3 nm, which signifies the transition to an oscillatory order parameter in the F layer. For J dp , which was measured down to T / T c Ϸ 0.5 using a pulsed-current technique, we find that the behavior can be well described by the Kupriyanov-Lukichev ͑KL͒ theory ͑Fiz. Nizk. Temp. 6, 445 ͑1980͒ ͓Sov. J. Low Temp. Phys. 6, 210 ͑1980͔͒͒, and therefore also by J dp ϰ ͑1−T / T c ͒ 3/2 in the Ginzburg-Landau ͑GL͒ regime close to T c . Extrapolating the GL regime to T = 0 yields J dp GL ͑0͒, which, as a function of d F , behaves similarly to T c ͑d F ͒ with a shallow minimum around d F =3-4 nm. At some temperature below T c , most samples break away from the KL curve to higher values of J dp , indicating a current-induced breakdown of the inhomogeneous state. Moreover, we find a significantly increased width of the transition to the normal state in the regime of the oscillatory order parameter.

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Section: Depairing Currentsmentioning

confidence: 90%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Depairing current behavior in superconductingNb∕Pd81Ni19bilayers

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“…Indeed, the J dp is comparable with the J GL dp only at temperatures nearby the T c , but not at low-T, e.g. J dp (0)/J GL dp (0) ≈ 0.385 [21]. Thus, we get to the value J dp (0) ≈363.6 MA/cm 2 that is still a bit higher than the estimated one (≈ 200 MA/cm 2 [11]) but of the same order or magnitude.…”

Section: Fig 2 (Color Online)mentioning

confidence: 98%

Direct observation of the depairing current density in single-crystalline Ba0.5K0.5Fe2As2 microbridge with nanoscale thickness

Yuan

et al. 2013

Applied Physics Letters

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We investigated the critical current density (Jc) of Ba0.5K0.5Fe2As2 single-crystalline microbridges with thicknesses ranging from 276 to 18 nm. The J c of the microbridge with thickness down to 91 nm is 10.8 MA/cm 2 at 35 K, and reaches 944.4 MA/cm 2 by extrapolating Jc(T ) to T = 0 K using a two-gap s-wave Ginzburg-Landau model, well in accordance with the depairing current limit. The temperature, magnetic field, and angular-dependence of Jc(T, H, θ) indicated weaker field dependence and weakly anisotropic factor of 1.15 (1 T) and 1.26 (5 T), which also yielded the validity of the anisotropic Ginzburg-Landau scaling.The newly discovered Fe-based superconductors caused increasing attention due to their potential for applications, owing to high superconducting (SC) transition temperature (T c ), high upper critical fields (H c2 ), and a low critical current (J c ) anisotropy [1]. Compared with the layered cuprate family, although Fe-based superconductors have lower T c , they demonstrate nearly isotropic transport behavior [1]. Investigation of anisotropic J c is essential, from the view point of basic physics parameters and potential applications [2][3][4]. Generally, there are two main methods to explore the J c . The first one is to study patterned thin film micro-devices. The thin films have been fabricated successfully for several systems, including Fe(Se,Te) [2], Ba(Fe,Co) 2 As 2 [3], and LaFeAsO 1−x F x [4]. However, one can hardly obtain an ideal single-crystalline film, due to the presence of twins and low-angle grain boundaries resulting from the island-like growth process [5]. Although the existence of grain boundaries can enhance the J c by increasing pinning, the critical current exhibits exponential decay in the weak-link regime which poses a serious obstacle for practical applications. Up to now, the J c of Fe-based thin films was reported at the level of a few MA/cm 2 at 4.3 K [3][4][5]. The other method is to measure the J c indirectly from magnetization hysteresis loop (MHL) of single crystals. By using the Bean's model the J c can be evaluated from the vortex penetration profile [6], which is determined by pining force owing to the defects, grain boundary, and geometry of the materials. The J c value estimated from MHL remains as well of the order of a few MA/cm 2 at 4.3 K [7]. * Author to whom correspondence should be addressed. Electronic mail: Jun.Li@fys.kuleuven.beWe emphasize that both methods for J c determination are limited by the vortex motion in presence of a finite pining force, but not the intrinsic transport capability of the material, for which an exploration of the GinzburgLandau (GL) depairing current density (J GL dp ) is of great importance for understanding the existing limits for increasing J c [8][9][10]. The J GL dp corresponds to the critical pair-breaking current, which was theoretically estimated to be as high as 200 MA/cm 2 at 0 K for (Ba,K)Fe 2 As 2 [11]. This value is two orders of magnitude larger than previously reported J c 's. Generally, it is rather difficult t...

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“…For a tunnel barrier, it is given by I = I C sin(φ) as first found by Josephson [9], where I C is the critical Josephson current. When the two SCs coupled by a thin ferromagnetic layer [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29], I C can change sign. Referring to the Josephson current-phase relationship, the change is corresponding to a π-phase shift of φ.…”

Section: Introductionmentioning

confidence: 99%

Josephson current in a ferromagnetic semiconductor/semiconductor/ferromagnetic semiconductor junction with superconducting contacts

Tao

2006

Journal of Applied Physics

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On the basis of a general expression for dc Josephson current, we study the Josephson current flowing through a ferromagnetic semiconductor (FS)/semiconductor (SM)/FS trilayer connected to two superconducting electrodes. It is demonstrated that the Josephson current in the junction strongly depends not only on the kinds of holes (the heavy or light) in the FS’s and scattering potential strengths at the interfaces but also on the relative orientations of the effective exchange field h of the two FS’s. We find that in the coherent regime, the oscillatory dependences of the critical Josephson current IC on the FS and SM layer thicknesses and of the Josephson current on the macroscopic phase difference ϕ for the heavy and light holes in different orientations of the effective exchange field h of the two FS’s are much different due to the different mismatches in the effective mass and Fermi velocity between the FS and superconductor, which is related to the transition from positive (0) to negative (π) coupling and can be exploited for the design of devices such as π superconducting quantum interference devices with improved accuracy and convenience.

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Depairing currents in the superconductor/ferromagnet proximity system Nb/Fe

Cited by 56 publications

References 25 publications

Depairing current behavior in superconductingNb∕Pd81Ni19bilayers

Depairing current behavior in superconductingNb∕Pd81Ni19bilayers

Direct observation of the depairing current density in single-crystalline Ba0.5K0.5Fe2As2 microbridge with nanoscale thickness

Josephson current in a ferromagnetic semiconductor/semiconductor/ferromagnetic semiconductor junction with superconducting contacts

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