Frozen disorder and edge contamination in magnetization measurements of the Bragg glass phase

Küpfer, H.; Ravikumar, G.; Wolf, Th.; Zhukov, A. A.; Meier‐Hirmer, R.

doi:10.1103/physrevb.70.144509

Cited by 18 publications

(27 citation statements)

References 33 publications

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“…An experimental confirmation of this result has been obtained on V 3 Si single crystals. Indeed by Peak Effect measurements, the BrG/Disordered phase transition was previously observed in the samples analysed here, at fields up to 7 T, [16,17]. By measurements of 3 rd harmonics, we succeeded here to measure the BrG/Disordered phase transition at higher fields, where other methods failed.…”

supporting

confidence: 61%

Transition between the Bragg glass and the disordered phase inNb3Sndetected by third harmonics of the ac magnetic susceptibility

et al. 2006

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We report additional experimental evidences about the presence of an universal behavior in the Field-Temperature Phase Diagram of Type II Superconductors. This behavior is characterized by a phase transition in the vortex matter between the disordered and the Bragg Glass phase. The experimental detection of a Peak Effect phenomenon has been proved to be strictly connected to the existence of this phase transition. In this paper, we show the first observation of a Peak Effect in the compound Nb 3 Sn, by using 1 st harmonics of the AC magnetic susceptibility. Peak Effect has been detected at fields between 3T and 13T, whereas it is not observable at higher fields. This seems to be in contrast with the theoretical predictions of such a phase transition at all fields and, therefore, with the predicted universality in the magnetic behavior of the Type II superconductors. Nevertheless, by measuring the 3 rd harmonics of the AC susceptibility, this phase transition has been detected up to our highest available field (19 T), thus demonstrating the necessity of the higher harmonics analysis in studying these topics and moreover proving the validity of the theoretical predictions. Magnetic flux penetrates a type II superconductor in form of vortices, which distribute in a regular lattice in absence of defects [1,2]. Defects affect the lattice ordering, but prevent the dissipations associated to the vortex movement [2]. An universal field-temperature phase diagram has been supposed for all the type II superconductors with point defects. In this phase diagram a transition in the vortex lattice has been predicted, between a disordered phase and the Bragg Glass Phase [3,4]. This latter is characterized by a quasi long range order and a perfect topological order, in which the vortex lattice stills survives despite the presence of the pinning [3], as it has also been experimentally evidenced [5]. The disordered phase has been supposed to be again a glass phase ("multidomain glass"), but with a topological disorder at the largest length scales [4]. The critical current density, J c [6], generally decreasing with increasing temperature and/or magnetic field [2], shows a local maximum, known as Peak Effect [7], when the Disordered/Bragg Phase transition occurs. For this reason, the observation of the Peak Effect has been widely used to detect this phase transition [3]. The Peak Effect has been evidenced in various classes of type II superconductors, e.g. low-T c [8][9][10][11][12], high-T c [13][14][15], boro-carbides [16] and MgB 2 [17]; however, it has not been observed in Nb 3 Sn up to the present day, to the best of our knowledge. Nb 3 Sn crystallizes in the A15 type structure and is actually the most used material in the manufacturing of superconducting magnets at very high fields [18]. In the present work, measurements have been performed on a high quality Nb 3 Sn single crystal, furnished by M. Toyota [19] (Dimensions ≈ 3 x 1.32 x 0.43 mm 3 ). The sample was characterized by T c = 18.2 K, ΔT c = 0.1 K, T m = 38.84 K. A valu...

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confidence: 61%

Transition between the Bragg glass and the disordered phase inNb3Sndetected by third harmonics of the ac magnetic susceptibility

et al. 2006

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“…Taking a cue from this observation, we show in fig. 1(b) the plots of ∆M normalized to its value at the peak field H p , vs. the reduced field, h (= µ 0 H/µ 0 H c2 ) for H c and H ⊥ c. It is satisfying to note that both the curves merge for H > H p (similar to those in the V 3 Si case [26]), thereby elucidating the insensitivity of the disordered vortex matter to the field direction, for H > H p , in YNBC as well. Considering that the superconducting parameters (coherence length ξ c /ξ ab , penetration depth λ c /λ ab , etc.)…”

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confidence: 68%

“…During exploration of the PE phenomenon in spherical as well as an irregular shaped single crystals of a cubic superconductor V 3 Si, Küpfer et al [26] found that, prima facie, the disordered state of the VL had no angular dependence for H > H p , while the state of order before the onset of the PE crucially depends on the symmetry of the field direction with respect to the underlying CL. Taking a cue from this observation, we show in fig.…”

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confidence: 99%

Anisotropy in spatial order-disorder transformations and the vortex lattice symmetry transition in YNi ₂ B ₂ C and LuNi ₂ B ₂ C

Jaiswal‐Nagar¹,

Isshiki²,

Kimura³

et al. 2008

Europhys. Lett.

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Explorations of the order-disorder transformation in vortex matter in single crystals of tetragonal structured (c/a ∼ 3) borocarbide superconductors, YNi2B2C and LuNi2B2C, reveal that vortex arrays experience different effective pinning in different crystallographic directions. We surmise that correlation exists between the large anisotropy in effective pinning/disorder and the differences in the (local) symmetry transition from rhombohedral to (quasi)square vortex lattice (VL). For a field along high-symmetry directions, like, the c-axis and ab basal plane, the VL symmetry is close to square and the ordered state spans a large field interval. When the field is turned away from the c-axis towards the ab-plane, at intermediate angles, the region of the ordered state shrinks, in response to enhancement in effective pinning. At such intermediate angles the symmetry of the VL would be far from ideal triangular or square.

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“…The V 3 Si single crystalline sphere (mass m % 11.1 mg) used for this study has been previously characterized using magnetization measurements by Küpfer et al (sample ''SA" in [15]). The authors irradiated V 3 Si samples with fast neutrons, and the present sample was further annealed for 2 h at 630°C in order to decrease pinning effects.…”

Section: Sample Characterizationmentioning

confidence: 99%

Differential-thermal analysis around and below the critical temperature Tc of various low-Tc superconductors: A comparative study

Reibelt

Schilling

Canfield

et al. 2008

Physica C: Superconductivity

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a b s t r a c tWe present specific-heat data on the type-II superconductors V 3 Si, LuNi 2 B 2 C and NbSe 2 which were acquired with a low-temperature thermal analysis (DTA) technique. We compare our data with available literature data on these superconductors. In the first part we show that the DTA technique allows for fast measurements while providing a very high resolution on the temperature scale. Sharp features in the specific heat such as at the one at the transition to superconductivity are resolved virtually without instrumental broadening. In the second part we investigate the magnetic-field dependence of the specific heats of V 3 Si and LuNi 2 B 2 C at a fixed temperature T = 7.5 K to demonstrate that DTA techniques also allow for sufficiently precise measurements of absolute values of c p even in the absence of a sharp phase transition. The corresponding data for V 3 Si and LuNi 2 B 2 C are briefly discussed.

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Frozen disorder and edge contamination in magnetization measurements of the Bragg glass phase

Cited by 18 publications

References 33 publications

Transition between the Bragg glass and the disordered phase inNb3Sndetected by third harmonics of the ac magnetic susceptibility

Transition between the Bragg glass and the disordered phase inNb3Sndetected by third harmonics of the ac magnetic susceptibility

Anisotropy in spatial order-disorder transformations and the vortex lattice symmetry transition in YNi ₂ B ₂ C and LuNi ₂ B ₂ C

Differential-thermal analysis around and below the critical temperature Tc of various low-Tc superconductors: A comparative study

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Frozen disorder and edge contamination in magnetization measurements of the Bragg glass phase

Cited by 18 publications

References 33 publications

Transition between the Bragg glass and the disordered phase inNb3Sndetected by third harmonics of the ac magnetic susceptibility

Transition between the Bragg glass and the disordered phase inNb3Sndetected by third harmonics of the ac magnetic susceptibility

Anisotropy in spatial order-disorder transformations and the vortex lattice symmetry transition in YNi 2 B 2 C and LuNi 2 B 2 C

Differential-thermal analysis around and below the critical temperature Tc of various low-Tc superconductors: A comparative study

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Anisotropy in spatial order-disorder transformations and the vortex lattice symmetry transition in YNi ₂ B ₂ C and LuNi ₂ B ₂ C