Magnetic-decoration imaging of structural transitions induced in vortex matter

Fasano, Yanina; Menghini, Mariela

doi:10.1088/0953-2048/21/02/023001

Cited by 42 publications

(34 citation statements)

References 175 publications

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“…The solid phase presents irreversible magnetic behavior ascribed to bulk pinning and surface barriers, each of them dominating at different temperature and measuring-time ranges [7][8][9] . Direct imaging of vortices in pristine Bi 2 Sr 2 CaCu 2 O 8 reveals the vortex solid has quasi long-range positional order 10,11 . Josephsonplasma-resonance measurements indicate the T FOT transition line corresponds to a single-vortex decoupling process between pancake vortices from adjacent layers within the same stack 12 .…”

Section: Introductionmentioning

confidence: 99%

Latent heat and nonlinear vortex liquid in the vicinity of the first-order phase transition in layeredhigh-Tcsuperconductors

et al. 2014

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In this work we revisit the vortex matter phase diagram in layered superconductors solving still open questions by means of AC and DC local magnetic measurements in the paradigmatic Bi2Sr2CaCu2O8 compound. We show that measuring with AC magnetic techniques is mandatory in order to probe the bulk response of vortex matter, particularly at high-temperatures where surface barriers for vortex entrance dominate. From the TFOT-evolution of the enthalpy and latent-heat at the transition we find that, contrary to previous reports, the nature of the dominant interlayer coupling is electromagnetic in the whole temperature range. By studying the dynamic properties of the phase located at T > ∼ TFOT, we reveal the spanning in a considerable fraction of the phase diagram of a non-linear vortex phase suggesting bulk pinning might play a role even in the liquid vortex phase.

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Section: Introductionmentioning

confidence: 99%

Latent heat and nonlinear vortex liquid in the vicinity of the first-order phase transition in layeredhigh-Tcsuperconductors

et al. 2014

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“…This is a relevant question for several techniques where field-cooling processes are typically used such as Bitter decoration or scanning Hall-probe microscopy. 10,30 In order to address this issue, we investigated the vortex mobility via SSM in the 9 m sample, at H = 1.3 G using h ac = 1 G while decreasing temperature in steps of 0. tices follow the ac excitation. This situation changes at T = 6.9 K where one of the vortices is able to oscillate inside the pinning potential whereas the other remains nearly still.…”

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confidence: 99%

Direct visualization of the Campbell regime in superconducting stripes

et al. 2010

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A combination of scanning Hall microscopy and scanning ac-susceptibility measurements in superconducting stripes ͑ribbons͒ of width w Ͻ 10 m was used to observe the dimensional phase transitions of the vortex lattice and its stability under alternating fields. At low dc magnetic fields applied perpendicularly to the plane of the stripes, vortices form a one-dimensional chain at the center of the stripes. Above a certain field H ‫ء‬ ͑w͒, the vortex chain splits in two parallel rows displaced laterally in such a way that a zigzag vortex pattern is observed. By shaking the vortices with an external magnetic ac field and detecting their in-phase motion locally, we can identify the degree of mobility of each individual vortex. This technique allows us ͑i͒ to directly visualize the transition from intravalley ͑Campbell regime͒ to intervalley vortex motion as the amplitude of the ac modulation is increased and ͑ii͒ to accurately determine the temperature at which the vortex lattice freezes in a field-cooling experiment. The hallmark of type II superconductivity is the presence of quantized magnetic flux encircled by a rotating condensate of paired electrons when a sufficiently strong magnetic field is applied. The free motion of these fluxons leads to dissipation thus destroying the perfect conductivity of the system. The ever growing electricity demand has motivated for several decades a fierce strive for understanding, improving, and optimizing the mechanisms to prevent the fluxon's motion by introducing a rich diversity of pinning centers. 1Among the most powerful experimental methods used to determine the efficiency of pinning sites is the ac-susceptibility technique which consist of shaking the flux-line lattice with a small alternating magnetic field while recording its in-phase magnetic response.2 Pioneering theoretical works by Campbell and co-workers substantially contributed to comprehend and interpret the ac response of a superconducting system. 3,4 In the most simple version, two different regimes with distinctive ac responses can be identified. For a gentle ac shacking, flux lines oscillate inside the pinning potential following a reversible and low dissipative motion ͑Campbell regime͒. By increasing the strength of the ac excitation, the intravalley vortex motion first senses the anharmonicities of the potential well and eventually switches to an intervalley motion where vortices can hop from one pinning site to another. 5So far, all the experimental and theoretical reports are focused on global ac-susceptibility investigations where the recorded signal represents an average over millions of flux lines each of which trapped in a different pinning potential and subjected to a different environment. [6][7][8] In this paper, we introduce a local vortex imaging technique with singlevortex resolution which allows us to directly visualize the oscillatory motion of individual vortices submitted to harmonic ac excitations. The system to investigate consists of superconducting ribbons which, due to the proximity o...

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“…The critical conditions for optimal deposition are Brought to you by | CSIC -Unidad Coordinacion Bibliotecas Authenticated Download Date | 12/12/17 12:07 PM defined by the amount of ferromagnetic material evaporated, the source-to-specimen distance, the helium vapor pressure (which strongly defines the size of the ferromagnetic clusters), and the magnetic field modulation within the sample. In order to ensure large field modulations in the sample, the applied magnetic field must be rather small [35,36].…”

Section: Bitter Decorationmentioning

confidence: 99%

6. Vortex dynamics in nanofabricated chemical solution deposition high-temperature superconducting films

Palau¹,

Rouco²,

Luccas³

et al. 2017

Superconductors at the Nanoscale

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Artificial manipulation and control of vortex dynamics in YBa 2 Cu 3 O 7 (YBCO) films have always been a complex issue, especially since high thermal excitations but also strong vortex pinning capabilities coexist in this material. Thus, artificial nanofabrication strategies able to generate competing effects with intrinsic microstructural defects need to be achieved. Lithography tools are widely used to create model systems with controlled pinning potentials in superconductors. However, these techniques easily disturb the optimal oxygen film doping in YBCO films and consequently the overall performances degrades. We have optimized the use of two different high-resolution nanolithography approaches, Focused Ion Beam Milling and Electron Beam Lithography, to artificially and locally modify the pinning landscape of YBCO films grown by chemical solution deposition (CSD). Three different nanofabricated systems will be discussed, which resulted in ideal structures to manipulate vortex dynamics in CSD-YBCO thin films with strong intrinsic pinning centers. In particular, we observed artificial granularity effects, nanowall pinning, and positive and negative rectification effects. We will report on our understanding of all these effects and potential expectations. IntroductionYBa 2 Cu 3 O 7−d (YBCO) is⁴ the technologically most relevant high-temperature superconductor, highly explored for practical applications [1][2][3][4][5][6]. The achievement of artificial pinning centers (APC) in YBCO films is of major concern when pinning forces need to be optimized, in coated conductors (long-length epitaxial YBCO films on buffered flexible metallic substrates), or when they need to be exploited for electronic applications, requiring flux quanta manipulation. However, flux pinning in cuprate superconductors requires control of the defect structure on a nanometric scale and this is a cumbersome problem. The primary concern is to develop efficient techniques for

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Magnetic-decoration imaging of structural transitions induced in vortex matter

Cited by 42 publications

References 175 publications

Latent heat and nonlinear vortex liquid in the vicinity of the first-order phase transition in layeredhigh-Tcsuperconductors

Latent heat and nonlinear vortex liquid in the vicinity of the first-order phase transition in layeredhigh-Tcsuperconductors

Direct visualization of the Campbell regime in superconducting stripes

6. Vortex dynamics in nanofabricated chemical solution deposition high-temperature superconducting films

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