Superfluid density and field-induced magnetism inBa(Fe1−xCox)2

Abstract

Superfluid density and field-induced magnetism inWe report muon spin rotation ͑SR͒ measurements of single-crystal Ba͑Fe 1−x Co x ͒ 2 As 2 and Sr͑Fe 1−x Co x ͒ 2 As 2 . From measurements of the magnetic field penetration depth we find that for optimally and overdoped samples, 1 / ͑T → 0͒ 2 varies monotonically with the superconducting transition temperature T C . Within the superconducting state we observe a positive shift in the muon precession signal, likely indicating that the applied field induces an internal magnetic field. The size of the induced field decreases with increasing doping but is present for all Co concentrations studied.

Muon spin rotation study of magnetism and superconductivity in Ba(Fe1−xCox)2Bernhard1, Wang2, Nuccio3 et al. 2012Phys. Rev. B5422871View full textAdd to dashboardCite

“…46,48,67 This superconductivity-induced paramagnetic shift of the TF-μSR line shape, which has also been consistently observed in the present optimally and overdoped single crystals (not shown), is most likely related to the superconductivity-induced enhancement of the low-energy spin fluctuations.…”

“…It has previously been very successfully applied to study the coexistence of magnetism and superconductivity in a variety of unconventional superconductors such as the underdoped cuprates, [37][38][39][40] the ruthenate cuprates, 41 the triplet superconductor Sr 2 RuO 4 (Ref. 42), or more recently the iron arsenides 11,12,15,17,19,20,[43][44][45][46][47] and iron selenides. [48][49][50] The neutron diffraction experiments were performed at the thermal four-circle single-crystal diffractometer TRICS at the spallation neutron source SINQ at PSI.…”

Millimeter-wave surface impedance of optimally-doped Ba(Fe1−xCox)2Barannik1, Cherpak2, Tanatar3 et al. 2013Phys. Rev. BSelf Cite284320View full textAdd to dashboardCite

“…Equation (20) is true for arbitrary correlation of R s (T ) and X s (T ). When R s (T ) X s (T ), or ωτ 1, the relation (20) can be reduced to (15). The experimentally determined R s (T ) and X s (T ) are shown in Fig.…”

“…Since anomalous scattering in the normal state is directly linked to the superconducting pairing strength [20], extension of these measurements into a superconducting state is of notable interest. So far, only cavity perturbation technique has been used for microwave -range measurements [14][15][16][17] and here we report the measurements using high Q− factor quasi-optical resonator with high-T c superconducting end-plates. All these techniques consistently showed non -exponential power-law low -temperature behavior, ∆λ(T ) = AT n , with n ≈ 2 − 2.8 at the optimal doping in Ba(Fe 1−x Co x ) 2 As 2 ("BaCo122") [10-13, 15, 16].…”

“…In particular, optimally -doped Ba(Fe 1−x Co x ) 2 As 2 (x ≈0.07) has been studied by using several techniques that cover a wide range of frequencies. Single crystals were measured using essentially DC measurements by magnetic -force microscopy and scanning SQUID [9,10], radio -frequency tunnel -diode resonator [11][12][13] and muon spin rotation (µSR) in vortex state [14,15] and in Meissner state [16], as well as microwave -range measurements [14][15][16][17]. THz and optical refelectivity measurements were performed on thin films [18,19].…”