Reversible suppression of the so-called fishtail effect in ultra pure single crystals of YBa2Cu3O7?? achieved by proper oxygenation

Erb, A.; Genoud, Jean-Yves; Marti, F.; Däumling, M.; Wałker, E.; Flükiger, R.

doi:10.1007/bf00768517

Cited by 104 publications

(50 citation statements)

References 10 publications

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“…18. It was shown in this paper that the flux-line pinning in pure YBa 2 Cu 3 O 7−δ crystals is mainly due to a nonuniform distribution of oxygen vacancies over the sample.…”

Section: A Numerical Resultsmentioning

confidence: 79%

“…But in the single vortex pinning regime the influence of the disorder is essential, and one has 27 u 2 T ∝ L c . To account for this result, we introduce an additional factor L c /ǫa in the formula (16) and thus obtain (18) in the single vortex pinning region at h < h sv . Inserting expression (16) into formula (15) and using definition (10) for ǫξ/L 0 c , we obtain the following equation for h sv = H sv /H c2 :…”

Section: The Order-disorder Line With Account Of Thermal Fluctuatmentioning

confidence: 99%

“…11,16 It is also important to note that at a fixed oxygen concentration the fishtail effect can disappear in pure YBaCuO crystals if the distribution of the oxygen vacancies over the sample becomes uniform. 18 At present the origin of the peak effect in low-T c and high-T c superconductors is commonly associated with the proliferation of dislocations in the flux-line lattice. [1][2][3][4][5][10][11][12][13][14][15][16] At this first order phase transition 3,[19][20][21][22] induced by quenched disorder in the vortex system, a transformation of a quasiordered Bragg glass 23 into a disordered amorphous vortex phase occurs.…”

Section: Introductionmentioning

confidence: 99%

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Peak effect, vortex-lattice melting line, and order-disorder transition in conventional and high-Tcsuperconductors

2001

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We investigate the order-disorder transition line from a Bragg glass to an amorphous vortex glass in the H − T phase diagram of three-dimensional type-II superconductors taking into account both pinning-caused and thermal fluctuations of the vortex lattice. Our approach is based on the Lindemann criterion and on results of the collective pinning theory and generalizes previous work of other authors. It is shown that the shapes of the order-disorder transition line and the vortex lattice melting curve are determined only by the Ginzburg number, which characterizes thermal fluctuations, and by a parameter which describes the strength of the quenched disorder in the fluxline lattice. In the framework of this unified approach we obtain the H − T phase diagrams for both conventional and high-Tc superconductors. Several well-known experimental results concerning the fishtail effect and the phase diagram of high-Tc superconductors are naturally explained by assuming that a peak effect in the critical current density versus H signalizes the order-disorder transition line in superconductors with point defects.

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“…18. It was shown in this paper that the flux-line pinning in pure YBa 2 Cu 3 O 7−δ crystals is mainly due to a nonuniform distribution of oxygen vacancies over the sample.…”

Section: A Numerical Resultsmentioning

confidence: 79%

Section: The Order-disorder Line With Account Of Thermal Fluctuatmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Peak effect, vortex-lattice melting line, and order-disorder transition in conventional and high-Tcsuperconductors

2001

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“…Magnetic measurements showed that in optimally doped YBa 2 Cu 3 O 7−δ crystals no fishtail behavior is observed both in detwinned [9] and twinned [10] samples, while decrease of the oxygen content always induced non monotonous J m (H)-curves. Two distinctive peculiarities in the magnetization curves of oxygen deficient [10] and electron irradiated [11] crystals were observed: (1) the peaks H on and H p shift toward lower magnetic fields with increasing defect concentration, and (2) in magnetic fields H < H p the current J m increases, while in magnetic fields H > H p the current J m decreases with increasing defect concentration.…”

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confidence: 95%

Effect of electron irradiation on vortex dynamics inYBa2Cu3O7<

et al. 2001

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We report on drastic change of vortex dynamics with increase of quenched disorder: for rather weak disorder we found a single vortex creep regime, which we attribute to a Bragg-glass phase, while for enhanced disorder we found an increase of both the depinning current and activation energy with magnetic field, which we attribute to entangled vortex phase. We also found that introduction of additional defects always increases the depinning current, but it increases activation energy only for elastic vortex creep, while it decreases activation energy for plastic vortex creep.PACS numbers: 74.60. Jg, 74.60.Ge, 74.60.Ec, 74.72.Bk The effect of random pinning on crystalline order and on dynamics of the flux-line-lattice (FLL) was a subject of numerous experimental and theoretical investigations. . The field H on was interpreted as a phase boundary between low field ordered and high field disordered vortex phases. These experimental results are supported by theoretical studies. It was shown that in presence of rather weak disorder the FLL retains a quasilong-range order resulting in the so-called Bragg glass phase [4]. However, with the increase of random pinning or magnetic field a transition to strongly disordered entangled vortex phase (glass phase) is predicted [5,6]. A sharp increase in magnetization below the fish-tail peak position H p was observed in N d 1.85 Ce 0.15 CuO 4−d [7] and non twinned YBa 2 Cu 3 O 7−δ [8] single crystals.Magnetic measurements showed that in optimally doped YBa 2 Cu 3 O 7−δ crystals no fishtail behavior is observed both in detwinned [9] and twinned [10] samples, while decrease of the oxygen content always induced non monotonous J m (H)-curves. Two distinctive peculiarities in the magnetization curves of oxygen deficient [10] and electron irradiated [11] crystals were observed: (1) the peaks H on and H p shift toward lower magnetic fields with increasing defect concentration, and (2) in magnetic fields H < H p the current J m increases, while in magnetic fields H > H p the current J m decreases with increasing defect concentration. It is believed [12,13] that the peak H p separates elastic vortex creep in low and plastic vortex creep, mediated by motion of the FLL dislocations, in high magnetic fields. Thus the introduction of additional defects leads to an increase of vortex pinning in the region of elastic creep and such behavior is expected. On the other hand, decrease of pinning force with increasing disorder observed in the region of plastic creep is non trivial, and reasons of such behavior are not known. The aim of this paper is to show the effect of point-like defects concentration on vortex dynamics and pinning parameters in YBa 2 Cu 3 O 7−δ single crystals.The investigated sample was YBa 2 Cu 3 O 7−δ single crystal with T c ≈ 93.5 K and ∆T c < 0.5 K. Twin planes (TP's) inside the measured part of the sample were aligned in one direction. The transport current was applied along the ab-plane and at an angle α = 45 • with respect to TP's. Measurements were performed in magnet...

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“…At temperatures as high as 700 o C the oxygen deficient regions are more likely to be randomly distributed, while at lower temperatures oxygen deficient unit cells tend to cluster due to the smaller contribution of the entropy term to the free energy [2,4,6, and references therein]. Thus, when we re-anneal the crystals clusters form.…”

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confidence: 99%

Experimental evidence for fast cluster formation of chain oxygen vacancies in YBa2Cu3O7−δ as the origin of the fishtail anomaly

Erb

Manuel

Dhallé

et al. 1999

Solid State Communications

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We report on three different and complementary measurements, namely magnetisation measurements positron annihilation spectroscopy and NMR measurements, which give evidence that the formation of oxygen vacancy clusters is on the origin of the fishtail anomaly in YBa 2 Cu 3 O 7−δ . While in the case of YBa 2 Cu 3 O 7.0 the anomaly is intrinsically absent, it can be suppressed in the optimally doped state where vacancies are present. We therefore conclude that the single vacancies or point defects can not be responsible for this anomaly but that clusters of oxygen vacancies are on its origin.

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Reversible suppression of the so-called fishtail effect in ultra pure single crystals of YBa2Cu3O7?? achieved by proper oxygenation

Cited by 104 publications

References 10 publications

Peak effect, vortex-lattice melting line, and order-disorder transition in conventional and high-Tcsuperconductors

Peak effect, vortex-lattice melting line, and order-disorder transition in conventional and high-Tcsuperconductors

Effect of electron irradiation on vortex dynamics inYBa2Cu3O7<

Experimental evidence for fast cluster formation of chain oxygen vacancies in YBa2Cu3O7−δ as the origin of the fishtail anomaly

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