Effective Demagnetizing Factors of Diamagnetic Samples of Various Shapes

Prozorov, Ruslan; Kogan, V. G.

doi:10.1103/physrevapplied.10.014030

Cited by 170 publications

(139 citation statements)

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“…A sharp transition and constant susceptibility value after the transition are evident to a high volume of the superconducting phase. The apparent shielding volume fraction of our samples was found to reach up to 85% at 4.2 K after demagnetisation correction [30]. We determined the critical temperature values for near-optimum doped BFNA and BKFA compositions to be 18.5 K and 35 K, respectively, which are slightly below the optimally doped values [23,31], and coincide with the elemental analysis investigations of the MA materials by EDS.…”

Section: Superconducting Propertiessupporting

confidence: 77%

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Synthesis of electron- and hole-doped bulk BaFe2As2 superconductors by mechanical alloying

Pervakov

Власенко

2020

Ceramics International

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Here, we report the successful synthesis of electron-(Ni) and hole-(K) doped bulk BaFe 2 As 2 compounds by means of mechanical alloying (MA) process. The MA technique allows one to obtain amorphous phase BaFe 2 As 2 with a homogeneous distribution of doping atoms at room temperature without continuous heating. We found the optimum time for high-energy milling is in the range between 1-1.5 hours. Using pre-synthesised FeAs and NiAs precursors, we successfully obtained BaFe 2−x Ni x As 2 and Ba 1−x K x Fe 2 As 2 superconducting bulk samples after shortrange heat treatment. This method can be easily scaled according to industrial needs to provide high-quality bulk superconducting material for wires, trappedfield magnets and other applications.

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Section: Superconducting Propertiessupporting

confidence: 77%

“…Temperature dependence of the real part (χ ) AC susceptibility of BKFA and BFNA at zero DC magnetic field. The demagnetization effect has been taken into consideration[30].…”

mentioning

confidence: 99%

Synthesis of electron- and hole-doped bulk BaFe2As2 superconductors by mechanical alloying

Pervakov

Власенко

2020

Ceramics International

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“…The setup consists of a thin diamond plate with one surface activated with NV centers in contact with a cuboid-shaped superconducting sample. The effective demagnetization factor depends on the geometry of the sample [55], therefore it is important to use samples with well defined shapes as determined from screening through a scanning electron microscope (SEM) Fig. 1(b).…”

Section: Resultsmentioning

confidence: 99%

Quantum phase transition inside the superconducting dome of Ba(Fe_1−xCo_x)₂As₂ from diamond-based optical magnetometry

et al. 2020

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Unconventional superconductivity often emerges in close proximity to a magnetic instability. Upon suppressing the magnetic transition down to zero temperature by tuning the carrier concentration, pressure, or disorder, the superconducting transition temperature Tc acquires its maximum value. A major challenge is the elucidation of the relationship between the superconducting phase and the strong quantum fluctuations expected near a quantum phase transition (QPT) that is either second order (i.e. a quantum critical point) or weakly first order. While unusual normal state properties, such as non-Fermi liquid behavior of the resistivity, are commonly associated with strong quantum fluctuations, evidence for its presence inside the superconducting dome are much scarcer. In this paper, we use sensitive and minimally invasive optical magnetometry based on NV-centers in diamond to probe the doping evolution of the T = 0 penetration depth in the electron-doped iron-based superconductor Ba(Fe1−xCox)2As2. A non-monotonic evolution with a pronounced peak in the vicinity of the putative magnetic QPT is found. This behavior is reminiscent to that previously seen in isovalently-substituted BaFe2(As1−xPx)2 compounds, despite the notable differences between these two systems. Whereas the latter is a very clean system that displays nodal superconductivity and a single simultaneous first-order nematic-magnetic transition, the former is a charge-doped and significantly dirtier system with fully gapped superconductivity and split second-order nematic and magnetic transitions. Thus, our observation of a sharp peak in λ(x) near optimal doping, combined with the theoretical result that a QPT alone does not mandate the appearance of such peak, unveils a puzzling and seemingly universal manifestation of magnetic quantum fluctuations in iron-based superconductors and unusually robust quantum phase transition under the dome of superconductivity.

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“…Interestingly, the peak effect, a feature of anomalous vortex pinning phenomenon, is observed in the high quality clean Cu x Bi 2 Se 3 crystals [15,16]. To estimate the volume shielding fraction, we take the demagnetization factor N into account, which can be calculated by [19]…”

Section: Crystal Structure and Compositionmentioning

confidence: 99%

Unconventional superconductivity in Cu_xBi₂Se₃ from magnetic susceptibility and electrical transport

Fang

You

2020

New J. Phys.

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Although the Cu doped Bi 2 Se 3 topological insulator was discovered and intensively studied for almost a decade, its electrical and magnetic properties in normal state, and the mechanism of 'high-T c ' superconductivity regarding the relatively low-carrier density are still not addressed yet. In this work, we report a systematic investigation of magnetic susceptibility, critical fields, and electrical transport on the nominal Cu 0.20 Bi 2 Se 3 single crystals with T onset c = 4.18 K, the highest so far. The composition analysis yields the Cu stoichiometry of x = 0.09(1). The magnetic susceptibility shows considerable anisotropy and an obvious kink at around 96 K was observed in the magnetic susceptibility for H c, which indicates a charge density anomaly. The electrical transport measurements indicate the two-dimensional (2D) Fermi liquid behavior at low temperatures with a high Kadowaki-Woods ratio, A/γ 2 = 30.3a 0 . The lower critical field at 0 K limit was extracted to be 6.0 Oe for H ab. In the clean limit, the ratio of energy gap to T c was determined to be Δ 0 /k B T c = 2.029 ± 0.124 exceeding the standard BCS value 1.764, suggesting Cu 0.09 Bi 2 Se 3 is a strong-coupling superconductor. The in-plane penetration depth at 0 K was calculated to be 1541.57 nm, resulting in an unprecedented high ratio of T c /λ −2 (0) ∼ = 9.86. Moreover, the ratio of T c to Fermi temperature is estimated to be T c /T 2D F = 0.034. Both ratios fall into the region of unconventional superconductivity according to Uemura's regime, supporting the unconventional superconducting mechanism in Cu x Bi 2 Se 3 . Finally, the enhanced T c value higher than 4 K is proposed to arise from the increased density of states at Fermi energy and strong electron-phonon interaction induced by the charge density instability. 1 K, such as SrTiO 3 (T c ∼ 0.05-0.29 K, n e = 0.65 to 42.4 × 10 20 cm −3 ) [3,4], GeTe (T c ∼ 0.07-0.3 K, n e = 8.6 to 15.2 × 10 20 cm −3 ) [5], and SnTe (T c ∼ 0.034-0.214 K, n p = 7.5 to 20.0 × 10 20 cm −3 ) [6]. To compare with these systems, the T c value of Cu x Bi 2 Se 3 is relatively 'high' given it is a highly doped narrow semiconductor with lower carrier density. However, the mechanism of such anomalous enhanced T c phenomenon remains unclear despite nearly a decade of extensive research. © 2020 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft New J. Phys. 22 (2020) 053026 Y Fang et alThe emergence and enhancement of superconductivity may occur in various cases by tailoring the ground states of quantum materials. For example, suppression of charge density wave (CDW) by chemical doping or pressure is observed in many systems [7-10], including low dimensional layered Cu x TiSe 2 and three dimensional (3D) alloys Lu(Pt 1−x Pd x ) 2 In and (Sr, Ca) 3 Ir 4 Sn 13 , 3D oxides Ba 1−x K x BiO 3 . Similarly, the magnetic ordering or spin density wave (SDW) have also been suppressed in strongly correlated heavy fermions materials, high-T c cuprates and i...

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Effective Demagnetizing Factors of Diamagnetic Samples of Various Shapes

Cited by 170 publications

References 13 publications

Synthesis of electron- and hole-doped bulk BaFe2As2 superconductors by mechanical alloying

Synthesis of electron- and hole-doped bulk BaFe2As2 superconductors by mechanical alloying

Quantum phase transition inside the superconducting dome of Ba(Fe_1−xCo_x)₂As₂ from diamond-based optical magnetometry

Unconventional superconductivity in Cu_xBi₂Se₃ from magnetic susceptibility and electrical transport

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Effective Demagnetizing Factors of Diamagnetic Samples of Various Shapes

Cited by 170 publications

References 13 publications

Synthesis of electron- and hole-doped bulk BaFe2As2 superconductors by mechanical alloying

Synthesis of electron- and hole-doped bulk BaFe2As2 superconductors by mechanical alloying

Quantum phase transition inside the superconducting dome of Ba(Fe1−xCox)2As2 from diamond-based optical magnetometry

Unconventional superconductivity in CuxBi2Se3 from magnetic susceptibility and electrical transport

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Quantum phase transition inside the superconducting dome of Ba(Fe_1−xCo_x)₂As₂ from diamond-based optical magnetometry

Unconventional superconductivity in Cu_xBi₂Se₃ from magnetic susceptibility and electrical transport