Dynamic vortex instabilities in Ta/Ge-based multilayers and thin films with various pinning strengths

Ruck, B. J.; Trodahl, H. J.; Abele, J. C.; Geselbracht, Margret J.

doi:10.1103/physrevb.62.12468

Cited by 17 publications

(24 citation statements)

References 14 publications

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“…When the bias current is further increased, the linear flux-flow regime is present until a certain value I * , where a sudden jump of the voltage V * takes place in agreement with the Larkin-Ovchinnikov theory [9]. Such instabilities were previously observed in a number of different superconducting systems [1,6,7,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. V * is related to the so-called critical velocity v * by the relation [9] At high fields the jump is replaced by a more continuous transition towards the normal state, as is clearly seen looking at the curves corresponding to the fields of 0.4 and 0.5 T in the inset of Fig.…”

Section: Resultssupporting

confidence: 52%

Influence of the magnetic configuration on the vortex-lattice instability in Nb/permalloy bilayers

et al. 2017

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We studied the dynamic instability of the vortex lattice in Nb/permalloy (permalloy = Ni 0.8 Fe 0.2 ) bilayers with different Py thickness d Py . When d Py is larger than some critical value, d ESD cr , which in our samples has been evaluated to be 125 nm, an inhomogeneous magnetic configuration is induced in the samples as a precursor to a fully developed stripe domain state. We found that this inhomogeneous magnetic configuration of the Py layer promotes larger values of the critical velocity for the vortex lattice instability, v * , with respect to the homogeneous case.

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Section: Resultssupporting

confidence: 52%

Influence of the magnetic configuration on the vortex-lattice instability in Nb/permalloy bilayers

et al. 2017

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“…14͒ in accordance with the enhanced gap values in high-T c materials. In Ta/ Ge multilayers, again ⌬͑0͒ = 1.76k B T c was found when the Ta layers were uncoupled, while a coupled anisotropic multilayer yielded ⌬͑0͒ = 3.5k B T c , 18 indicating that the anisotropy leads to an effective value for ⌬͑0͒ without changing the exponential dependence.…”

Section: Vortex Lattice Instabilitiesmentioning

confidence: 92%

“…Such instabilities have been observed in a number of systems including low-temperature [9][10][11][12] and high-temperature superconducting thin films [13][14][15][16] and multilayers. [17][18][19] What essentially emerges from these studies is that the voltage jumps are indeed due to intrinsic properties of the moving vortex lattice but that two more ingredients may play a role, ͑i͒ the temperature dependence of E , in particular, when electron-electron interactions dominate the relaxation, and ͑ii͒ vortex pinning, ignored in the original LO theory. 20 The LO theory has been also extended to explicitly consider the contributions due to the heating effect.…”

Section: Introductionmentioning

confidence: 99%

High-velocity instabilities in the vortex lattice of Nb/permalloy bilayers

et al. 2007

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We have studied the critical current density J c for onset of vortex motion and the dynamic instability of the moving vortex lattice at high driving currents in superconducting ͑S͒/ferromagnetic ͑F͒ Nb/ Ni 0.80 Fe 0.20 bilayers and in a single Nb film with the same thickness. The samples are all characterized by relatively high values of the pinning strength. The measured current-voltage characteristics are successfully described in the framework of the Larkin-Ovchinnikov model, modified in order to take into account the effect of the pinning close to the instability. We find that J c is smaller in the S/F bilayers than in the single film and argue that this is due to the strongly inhomogeneous order parameter in the bilayers. Also, the critical velocity v * for the occurrence of the instability is found to be significantly larger in the S/F bilayers than in the single S layer. By extracting the quasiparticle energy relaxation rate from v * , we show that this effect is due to the same inhomogeneous order parameter and the resulting lower average value of the superconducting gap.

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“…Thus one can determine τ by measuring the instability velocity of the flux-flow state. The LO instability of the flux-flow state has been observed both in conventional [48][49][50][51][52][53] and high-T c cuprate superconductors. 54,55 Typical IV curves at several magnetic fields are depicted in Fig.…”

Section: A Larkin-ovchinnikov Instabilitymentioning

confidence: 99%

Characterization of the thin-film NbN superconductor for single-photon detection by transport measurements

et al. 2013

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The fabrication of high-quality thin superconducting films is essential for single-photon detectors. Their device performance is crucially affected by their material parameters, thus requiring reliable and nondestructive characterization methods after the fabrication and patterning processes. Important material parameters to know are the resistivity, superconducting transition temperature, relaxation time of quasiparticles, and uniformity of patterned wires. In this work, we characterize micro-patterned thin NbN films by using transport measurements in magnetic fields. We show that from the instability of vortex motion at high currents in the flux-flow state of the IV characteristic, the inelastic life time of quasiparticles can be determined to be about 2 ns. Additionally, from the depinning transition of vortices at low currents, as a function of magnetic field, the size distribution of grains can be extracted. This size distribution is found to be in agreement with the film morphology obtained from scanning electron microscopy and high-resolution transmission electron microscopy images.

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Dynamic vortex instabilities in Ta/Ge-based multilayers and thin films with various pinning strengths

Cited by 17 publications

References 14 publications

Influence of the magnetic configuration on the vortex-lattice instability in Nb/permalloy bilayers

Influence of the magnetic configuration on the vortex-lattice instability in Nb/permalloy bilayers

High-velocity instabilities in the vortex lattice of Nb/permalloy bilayers

Characterization of the thin-film NbN superconductor for single-photon detection by transport measurements

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