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Demirdiş, Sultan; Fasano, Yanina; Kasahara, S.; Terashima, Taichi; Shibauchi, T.; Matsuda, Yuji; Kończykowski, M.; Pastoriza, H.; Beek, C.J. van der

doi:10.1103/physrevb.87.094506

Cited by 30 publications

(53 citation statements)

References 51 publications

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“…So far, some groups reported the existence of the SMP effect [67,68] whereas other groups reported the its absence [28,47]. In the latter cases, the MHLs were measured only in fields up to µ0H = 2 T. According to the present results it is difficult to observe the SMP effect below 2 T, which may be the reason for the apparent discrepancy.…”

Section: P-ba122contrasting

confidence: 76%

“…(6) As for the doping dependence of Jc, existing results are controversial. For example, (i) the doping dependence of Jc follows the doping dependence of superconducting transition temperature (Tc) (for Co-Ba122 [30]), (ii) Jc does not follow Tc and becomes highest at the under-doped region (for Co-Ba122 [40] and K-Ba122 [46]), and (iii) Jc is determined by some extrinsic factors rather than by the doping concentration (for P-Ba122 [47]). At this moment consensus has not been settled yet.…”

Section: Introductionmentioning

confidence: 99%

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Doping-dependent critical current properties in K, Co, and P-doped BaFe2As2 single crystals

et al. 2017

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* Both authors contributed equally to this work.In order to establish the doping dependence of the critical current properties in the iron-based superconductors, the in-plane critical current density (Jc) of BaFe2As2-based superconductors, Ba1-xKxFe2As2 (K-Ba122), Ba(Fe1-xCox)2As2 (Co-Ba122), and BaFe2(As1-xPx)2 (P-Ba122) in a wide range of doping concentration (x) was investigated by means of magnetization hysteresis loop (MHL) measurements on single crystal samples. Depending on the dopant elements and their concentration, Jc exhibits a variety of magneticfield (H)-and temperature (T)-dependences. (1) In the case of K-Ba122, the MHL of the under-doped samples (x ≤ 0.33) exhibits the second magnetization peak (SMP), which sustains high Jc at high H and high T, exceeding 10 5 A/cm 2 at T = 25 K and µ0H = 6 T for x = 0.30. On the other hand, the SMP is missing in the optimally-(x ~ 0.36-0.40) and over-doped (x ~ 0.50) samples, and consequently Jc rapidly decreases by more than one order of magnitude, although the change in Tc is within a few K. (2) For Co-Ba122, the SMP is always present over the entire superconducting (SC) dome from the under-(x ~ 0.05) to the over-doped (x ~ 0.12) region. However, the magnitude of Jc significantly changes with x, exhibiting a sharp maximum at x ~ 0.057, which is a slightly under-doped composition among Co-Ba122. (3) For P-Ba122, the highest Jc is attained at x = 0.30 corresponding to the highest Tc composition. For the over-doped samples, the MHL is characterized by a SMP located close to the irreversibility field Hirr. Common to the three doping variations, Jc becomes highest at the under-doping side of the SC dome near the phase boundary between the SC phase and the antiferromagnetic/orthorhombic (AFO) phase. Also, the peak appears in a narrow range of doping, distinct from the Tc dome with broad maximum. These similarities in the three cases indicate that the observed doping dependence of Jc is intrinsic to the BaFe2As2-based superconductors. The scaling analysis of the normalized pinning force density fp as a function of the reduced magnetic field h = H/Hirr (Hirr: irreversibility field) shows that the peak in the pinning force position (hmax) depends on x, indicating a change in pinning with x. On the other hand, high-Jc samples always attain similar hmax values of 0.40-0.45 for all the dopants, which may suggest that a common pinning source causes the highest Jc. A quantitative analysis of the Tdependent Jc indicates that the two pinning mechanisms, namely, the spatial variations in Tc (referred to as Tc pinning) and the fluctuations in the mean free path (l pinning), are enhanced for the under-doped samples, which results in the enhancement of Jc. Possible origins for the different pinning mechanism are discussed in connection with the x-dependence of Tc, the residual resistivity, AFO domain boundaries, and a possible quantum critical point.

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Section: P-ba122contrasting

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Doping-dependent critical current properties in K, Co, and P-doped BaFe2As2 single crystals

et al. 2017

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“…Conversely, if is known, hNV can be extracted. In our analysis, we set 200 nm based on previous measurements 40,41 , which yields hNV = 330 nm to most closely fit the data in Fig. 5a,b.…”

Section: Cryogenic Magnetic Imagingmentioning

confidence: 99%

Scanned probe imaging of nanoscale magnetism at cryogenic temperatures with a single-spin quantum sensor

et al. 2016

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High spatial resolution magnetic imaging has driven important developments in fields ranging from materials science to biology. However, to uncover finer details approaching the nanoscale with greater sensitivity requires the development of a radically new sensor technology. The nitrogenvacancy (NV) defect in diamond has emerged as a promising candidate for such a sensor based on its atomic size and quantum-limited sensing capabilities afforded by long spin coherence times. Although the NV center has been successfully implemented as a nanoscale scanning magnetic probe at room temperature, it has remained an outstanding challenge to extend this capability to cryogenic temperatures, where many solid-state systems exhibit non-trivial magnetic order. Here we present NV magnetic imaging down to 6 K with 6 nm spatial resolution and 3 μT/√Hz field sensitivity, first benchmarking the technique with a magnetic hard disk sample, then utilizing the technique to image vortices in the iron pnictide superconductor BaFe2(As0.7P0.3)2 with Tc = 30 K. The expansion of NVbased magnetic imaging to cryogenic temperatures represents an important advance in state-of-theart magnetometry, which will enable future studies of heretofore inaccessible nanoscale magnetism in condensed matter systems. and Lorentz transmission electron microscopy (TEM) 7 , and reciprocal space techniques including neutron scattering 8 have been successfully utilized to study magnetism in these systems. However, each of these techniques has limitations that must be considered. In MFM, a ferromagnetic tip must be placed in close proximity to a sample, which can perturb the magnetic order that is being probed.Scanning SQUIDs typically require a probe temperature of 10 K or lower, and generally offer micron-size spatial resolution, although recent studies have enhanced the resolution to submicron scales 9 . Lorentz TEM can provide images with high spatial resolution and magnetic contrast, but requires very thin samples, typically less than 100 nm thick. Neutron scattering requires the growth of large, high purity single-crystal samples, and is an ensemble-averaged measurement. There is therefore a significant opportunity to develop a real-space, non-invasive magnetic sensor capable of studying magnetic order at sub-10 nm spatial resolution and sub-T/Hz DC field sensitivities.The nitrogen vacancy (NV) defect center in diamond is an exceptionally versatile single spin system with unique quantum properties that have driven its application in diverse areas ranging from quantum information and photonics to quantum metrology [10][11][12][13][14][15][16][17][18][19] . Cryogenic scanning magnetometry stands out as potentially the most impactful application of NV centers, taking advantage of the exquisite magnetic field sensitivity and intrinsic atomic scale of the NV center for high resolution imaging 20 . The operation of an NV-based magnetic probe is dependent on a fundamentally different sensing principle than other imaging methods, namely the spin-dependent photolum...

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“…Namely, the Tc and ξ in BaFe2(As1-xPx)2 are exceptionally sensitive to the stoichiometry 16 , such that these variations demarcate phase-separated regions that are effective pinning sites. These regions are spaced roughly 100 nm apart 15 , therefore, outnumber the vortices in fields less than . This is analogous to pinning in Sm1+xBa2-xCu3Oy (Sm123) films, in which Sm-rich123 precipitates of lower Tc than the Sm123 matrix are effective pinning centers 17 .…”

Section: Th) and S(th)mentioning

confidence: 99%

Universal lower limit on vortex creep in superconductors

et al. 2017

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The search for a universal description of vortex matter -one that is applicable to a range of systems and regimes -is a formidable challenge, complicated by the complexity of the interactions between vortices and the environment. Vortex motion that can be induced by Magnus and Lorentz forces or thermal activation can also be counteracted by pinning forces. Because vortex cores are normal (i.e., superfluidity or superconductivity is destroyed inside them), creating a vortex costs energy, and pinning can occur when it is energetically more favorable for a vortex to appear in one location than in another. In type-II superconductors at high enough magnetic fields, vortices are formed by the penetration of magnetic flux, and material disorder that locally reduces the vortex core energy can produce pinning forces that almost completely preclude vortex motion. This results in nearly zero resistance, as long as the current density (J) does not exceed the critical current density (Jc). The caveat is that, for J

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Disorder, critical currents, and vortex pinning energies in isovalently substituted BaFe2(As1−xP

Cited by 30 publications

References 51 publications

Doping-dependent critical current properties in K, Co, and P-doped BaFe2As2 single crystals

Doping-dependent critical current properties in K, Co, and P-doped BaFe2As2 single crystals

Scanned probe imaging of nanoscale magnetism at cryogenic temperatures with a single-spin quantum sensor

Universal lower limit on vortex creep in superconductors

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