Sharp peak of the critical current density in 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>BaFe</mml:mi><mml:mrow><mml:mn>2</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>Ni</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi>As</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>
 at optimal composition

Gennep, Derrick Van; Hassan, Abdelwahab; Luo, Huiqian; Abdel-Hafiez, M.

doi:10.1103/physrevb.101.235163

Cited by 14 publications

(10 citation statements)

References 52 publications

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“…On the other hand, the lower values of jc(0)/jd 10 -3 -10 -2 are characteristic for high-temperature superconductors, e.g. the cuprate family, in which the Ginzburg-Landau parameter is large ( 100) and pinning originated from point defects, e.g., oxygen vacancies 52 , is relatively weak. To improve the infield critical current performance in cuprates, different types of artificial pinning centers are introduced in the sample structure.…”

Section: Resultsmentioning

confidence: 99%

Magnetic field screening in hydrogen-rich high-temperature superconductors

et al. 2022

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In the last few years, the superconducting transition temperature, Tc, of hydrogen-rich compounds has increased dramatically, and is now approaching room temperature. However, the pressures at which these materials are stable exceed one million atmospheres and limit the number of available experimental studies. Superconductivity in hydrides has been primarily explored by electrical transport measurements, whereas magnetic properties, one of the most important characteristic of a superconductor, have not been satisfactory defined. Here, we develop SQUID magnetometry under extreme high-pressure conditions and report characteristic superconducting parameters for Im-3m-H3S and Fm-3m-LaH10—the representative members of two families of high-temperature superconducting hydrides. We determine a lower critical field Hc1 of ∼0.82 T and ∼0.55 T, and a London penetration depth λL of ∼20 nm and ∼30 nm in H3S and LaH10, respectively. The small values of λL indicate a high superfluid density in both hydrides. These compounds have the values of the Ginzburg-Landau parameter κ ∼12–20 and belong to the group of “moderate” type II superconductors, rather than being hard superconductors as would be intuitively expected from their high Tcs.

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Section: Resultsmentioning

confidence: 99%

Magnetic field screening in hydrogen-rich high-temperature superconductors

et al. 2022

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“…Figure 5.10 shows the final product, and the central result of this chapter; a sharp peak in the critical current density of Ni-Ba122 occurring at the optimal doping value of x = 0.050. This result was published in Superconducting Science and Technology [141], and has since also been observed by other groups also measuring J c as a function of nickel doping [118].…”

Section: J C Versus Dopingsupporting

confidence: 73%

“…It is interesting to note that this peak is less prominent in the parallel field orientation, also coinciding with much smaller values of J c , with a peak value just over 0.1 MA/cm 2 . A number of studies in doped BaFe 2 As 2 single crystals have found that there is a coexistence of δl and δT c pinning [112,118,119] thus, this difference could be interpreted as each orientation having a dominant contribution from different pinning mechanisms, and the quantum critical behaviour is favouring improvement in one of the two.…”

Section: J C Versus Dopingmentioning

confidence: 99%

The Interplay of Pressure and Doping Effects on BaFe2As2 Superconductors

Bioletti¹

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The study of iron-based superconductors exists at the intersection of some of the most fascinating disciplines in physical sciences, with avenues to reach illuminating conclusions in the study of magnetism, quantum physics, materials science, and applications at the forefront of technical engineering. The youth of the field is apparent, having only been discovered in 2008, with many open questions as to how the many facets of their normal-state and superconducting properties intermingle, and behave under the extreme conditions made imperative by their significant promise of applicability in magnet technologies. This thesis hones in on the study of BaFe2As2 and the way in which isovalent doping with phosphorous, charge doping with nickel, and the application of intermediate amounts of hydrostatic pressure (1.2 GPa) affect it’s superconducting critical current density (Jc) and superconducting critical temperature (Tc). This avenue of study already provides a multitude of interesting results. We uncover a significantly orientation dependent sharp peak in the Ni- doping dependent phase diagram, coincident with a large increase in the susceptibility of Jc to applied pressure. Pressure applied at the optimal doping of Ba(Fe0.95Ni0.05)2As2 result in increases of 300 %, drastically up from 50 % Ba(Fe0.95Ni0.048)2As2, exemplifying a behaviour correlated with the posited quantum critical point (QCP) at this doping. The fact that this striking behaviour only manifests in a field oriented perpendicular to the materials ab-plane at ambient pressure, reinforced by the application of Dew-Hughes and strong pinning models, makes a strong case for it being a phenomena dependent on the coexistence of both δTc and δl forms of pinning. The behaviour of the phosphorous doped material is immediately contrast- ing, with changes in Jc completely correlated with changes in Tc. The behaviour of Tc under applied pressures illuminates a non-linear response at low pressures due to the difference in compressibility of orthogonal lattice parameters along the c and a axes. This effect results in huge suppression of Tc with the optimally doped sample displaying a shift from Tc = 29 to 15.5 K at a rate of 35 K/GPa. Further analysis shows that this may be re- lated to a softening in the structural lattice induced by the P-doping. This work exemplifies the complex nature of the interacting material and superconducting properties of BaFe2As2, and will prove useful to any future research attempting to optimise BaFe2As2 for future application as well as filling out the body of work necessary to understand the nature of superconductivity in iron-based superconductors.

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“…Similar results have been observed in other iron pnictide superconductors as reported in Refs. [18,60,61,62]. Moreover, according to Dew-Hughes model [57], h max < 0.5 indicates a δl pinning, while h max > 0.5 suggests δT c pinning, therefore, h max = 0.27 in present case is suggestive of δl pinning.…”

Section: Resultsmentioning

confidence: 51%

Vortex dynamics and second magnetization peak in the iron-pnictide superconductor Ca$_{0.82}$La$_{0.18}$Fe$_{0.96}$Ni$_{0.04}$As$_2$

Llovo,

Sóñora,

Mosqueira

et al. 2021

Preprint

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We report the studies of detailed magnetic relaxation and isothermal magnetization measurements in the vortex state of the 112-type iron-pnictide Ca 0.82 La 0.18 Fe 0.96 Ni 0.04 As 2 superconductor with T c ∼ 22 K. In the isothermal M (H), a well defined second magnetization peak (SMP) feature is observed in the entire temperature range below T c for measurements with H c-axis. However, for H ab-planes, the SMP feature is suppressed at low temperatures, which might be due to 2D Josephson vortices forming at low temperatures and high magnetic fields in such an anisotropic system. A rigorous analysis considering the magnetic relaxation data for H c-axis suggests an elastic to plastic pinning crossover across H p , which also seems accompanied with a possible phase transition in vortex lattice near H p . Moreover, point disorder and surface defects are likely to be the dominant sources of pinning, which contribute to the δl-type of pinning in the sample. A high J c , in access of 10 5 A/cm 2 observed could potentially make this material technologically important.

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Sharp peak of the critical current density in BaFe2−xNixAs2 at optimal composition

Cited by 14 publications

References 52 publications

Magnetic field screening in hydrogen-rich high-temperature superconductors

Magnetic field screening in hydrogen-rich high-temperature superconductors

The Interplay of Pressure and Doping Effects on BaFe2As2 Superconductors

Vortex dynamics and second magnetization peak in the iron-pnictide superconductor Ca$_{0.82}$La$_{0.18}$Fe$_{0.96}$Ni$_{0.04}$As$_2$

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