Strong shift of the irreversibility line in high-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>T</mml:mi></mml:mrow><mml:mrow><mml:mi>c</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>superconductors upon vortex shaking with an oscillating magnetic field

Willemin, M.; Rossel, C.; Hofer, J.; Keller, H.; Erb, A.; Wałker, E.

doi:10.1103/physrevb.58.r5940

Cited by 98 publications

(85 citation statements)

References 28 publications

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“…To do this, it is assumed that the flux pinning in decreasing magnetic field is the same as in increasing magnetic field and an equilibrium magnetization is defined as the average of the average of the increasing field magnetization and the decreasing field magnetization by M eq = (M inc + M dec )/2. Willemin and co-workers 6 have shown the validity of this procedure. A plot of M eq vs. T in Fig.6 shows behavior close to that predicted by Abrikosov.…”

Section: Resultsmentioning

confidence: 99%

Thermodynamic and Transport Properties of SuperconductingMg10B2

et al. 2001

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Transport and thermodynamic properties of a sintered pellet of the newly discovered M gB2 superconductor have been measured to determine the characteristic critical magnetic fields and critical current densities. Both resistive transition and magnetization data give similar values of the upper critical field, Hc2, with magnetization data giving dHc2/dT = 0.44 T /K at the transition temperature of Tc = 40.2 K. Close to the transition temperature, magnetization curves are thermodynamically reversible, but at low temperatures the trapped flux can be on the order of one Tesla. The value of dHc/dT at Tc is estimated to be about 12 mT /K, a value similar to classical superconductors like Sn. Hence, the Ginsburg-Landau parameter κ ∼ 26. Estimates of the critical supercurrent density, Jc, using hysteresis loops and the Bean model give critical current densities on the order of 10 5 A/cm 2 . Hence the supercurrent coupling through the grain boundaries is comparable to intermetallics like N b3Sn.74.25. Bt, 74.25.Fy, 74.25.Ha, 74.60.Ge, 74.60.Jg

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Section: Resultsmentioning

confidence: 99%

Thermodynamic and Transport Properties of SuperconductingMg10B2

et al. 2001

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“…(1) yields an overestimation of the anisotropy [24], which is the case also in MgB 2 [23]. To obtain the true reversible torque, we employed a vortex-shaking process, which speeds up the relaxation of the vortex lattice [24]. As can be seen in Fig.…”

Section: Torque Magnetometry Investigationsmentioning

confidence: 99%

“…When the reversible torque is estimated by simple averaging of the torque values obtained from angle increasing and decreasing scans, usually an analysis with Eq. (1) yields an overestimation of the anisotropy [24], which is the case also in MgB 2 [23]. To obtain the true reversible torque, we employed a vortex-shaking process, which speeds up the relaxation of the vortex lattice [24].…”

Section: Torque Magnetometry Investigationsmentioning

confidence: 99%

MgB₂single crystals: high pressure growth and physical properties

Karpiński

Angst

Jun

et al. 2003

Supercond. Sci. Technol.

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Single crystals of MgB 2 with a size up to 1.5x0.9x0.2 mm 3 have been grown with a high pressure cubic anvil technique. The crystal growth process is very peculiar and involves an intermediate nitride, namely MgNB 9 . Single crystals of BN and MgB 2 grow simultaneously by idth of ~0.5 K. The high quality of the crystals allowed the accurate determination of magnetic, transport (electric and heat) and optical properties as well as scanning tunnelling spectroscopy (STS) and decoration studies. Investigations of crystals with torque magnetometry show that H c2 //c for high quality crystals is very low (24 kOe at 15 K) and saturates with decreasing temperature, while H c2 //ab increases up to 140 kOe at 15 K. The upper critical field anisotropy = H c2 //ab / H c2 //c was found to be temperature dependent (decreasing from ≅ 6 at 15 K to 2.8 at 35 K). The effective anisotropy γ eff , as calculated from reversible torque data near T c , is field dea peritectic decomposition of MgNB 9 . Magnetic measurements with SQUID magnetometry in fields of 1-5 Oe show sharp transitions to the superconducting state at 37-38.6 K with wpendent (increasing roughly linearly from eff ≅ 2 in zero field to 3.7 in 10 kOe). The temperature and field dependence of the anisotropy can be related to the double gap structure of MgB 2 with a large two-dimensional gap and small three-dimensional gap, the latter of which is rapidly suppressed in a magnetic field. Torque magnetometry investigations also show a pronounced peak effect, which indicates an order-disorder phase transition of vortex matter. Decoration experiments and STS visualise a hexagonal vortex lattice. STS spectra in zero field evidence two gaps 3 meV and 6 meV with a weight depending on the tunnelling direction. Magneto-optic investigations in the far infrared region with H//c show a clear signature of the smaller of the two superconducting gaps, completely disappearing only in fields higher than H c2 //c .

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“…This might be caused by the sound waves distorting the crystallographic lattice and leading thereby to a rearrangement of the vortices into a regular lattice. In this context, one may refer to earlier vortex-shaking experiments, where the application of an additional oscillating magnetic field leads to a fast depinning of the vortex lattice [41][42][43][44]. Although sound waves do not directly shake vortices, they shake pinning centers which in return could rearrange the vortices.…”

Section: And References Therein)mentioning

confidence: 99%

Field-induced gapless electron pocket in the superconducting vortex phase ofYNi2B2Cas probed by magnetoacoustic quantum oscillations

et al. 2017

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By use of ultrasound studies we resolved magneto-acoustic quantum oscillation deep into the mixed state of the multiband nonmagnetic superconductor YNi2B2C. Below the upper critical field, only a very weak additional damping appears that can be well explained by the field inhomogeneity caused by the flux-line lattice in the mixed state. This is clear evidence for no or a vanishingly small gap for one of the bands, namely, the spheroidal α band. This contrasts de Haas-van Alphen data obtained by use of torque magnetometry for the same sample, with a rapidly vanishing oscillation signal in the mixed state. This points to a strongly distorted flux-line lattice in the latter case that, in general, can hamper a reliable extraction of gap parameters by use of such techniques. † This work is dedicated to the memory of Lev Petrovich Gor'kovThe observation of magnetic quantum oscillations is usually taken as evidence for the existence of a Fermi surface. The appearance of Landau levels in a magnetic field leads to an oscillating density of states at the Fermi level as a function of field. Experimentally, these oscillations can be detected in many thermodynamic and transport properties, with the most prominent being the de Haas-van Alphen (dHvA) effect in the magnetization. Consequently, the observation of dHvA oscillations in the mixed state of a superconductor first appeared as a surprise [1]. Below the upper critical field, B c2 , the opening of a superconducting gap and the corresponding disappearance of the entire Fermi surface seem to contradict the existence of such oscillations. Nevertheless, they were observed in many type-II superconductors ([2-4] and references therein).Motivated by the experimental evidence, however, it subsequently was shown by a number of theoretical studies that this phenomenon may be understood in principle in a rather general context. Thereby, different models are used to explain the occurrence of quantum oscillations below B c2 [5-9], but it still remains unclear which of them is the most appropriate. Usually, the validity of these theories is tested by comparing the predicted additional damping of the quantum oscillations below B c2 with experiment. Such analysis gives as the main fit parameter the superconducting gap at zero temperature, ∆ 0 , a value that largely depends on the used model.With the proper theory at hand dHvA data could, in principle, yield information on the field and angular evolution of the superconducting gap, ∆. However, considerable ambiguity in ∆ is introduced not only by the various theoretical predictions but even more from varying, sometimes contradictory, experimental data. In particular, for YNi 2 B 2 C and LuNi 2 B 2 C highly controversial results were reported [4,[10][11][12][13][14][15][16][17][18]. Thereby, for the so-called α band, an additional damping of the dHvA signal was found either in line with the opening of a weak-coupling gap [11][12][13]15], or yielding an unexpectedly small gap [4,10,14,17,18], or even an abrupt vanishing of the oscillatio...

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Strong shift of the irreversibility line in high-Tcsuperconductors upon vortex shaking with an oscillating magnetic field

Cited by 98 publications

References 28 publications

Thermodynamic and Transport Properties of SuperconductingMg10B2

Thermodynamic and Transport Properties of SuperconductingMg10B2

MgB₂single crystals: high pressure growth and physical properties

Field-induced gapless electron pocket in the superconducting vortex phase ofYNi2B2Cas probed by magnetoacoustic quantum oscillations

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Strong shift of the irreversibility line in high-Tcsuperconductors upon vortex shaking with an oscillating magnetic field

Cited by 98 publications

References 28 publications

Thermodynamic and Transport Properties of SuperconductingMg10B2

Thermodynamic and Transport Properties of SuperconductingMg10B2

MgB2single crystals: high pressure growth and physical properties

Field-induced gapless electron pocket in the superconducting vortex phase ofYNi2B2Cas probed by magnetoacoustic quantum oscillations

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Product

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MgB₂single crystals: high pressure growth and physical properties