Effects of irradiation-particle energy on critical current density in Co-doped BaFe2As2

Enhancement of Critical Current Densities in (Ba,K)Fe2As2by 320 MeV Au Irradiation in Single Crystals and by High-Pressure Sintering in Powder-in-Tube Wires

“…The reason why low-energy irradiation (320 MeV) of Au-ion is more effective than high-energy irradiation (1.4 GeV) of Pb-ion for increasing J c , is not clear yet. Similar particle energy dependence of J c has been observed in Au-irradiated Ba(Fe,Co) 2 As 2 [35]. One of the possibilities is that defects are not parallel to each other but become splayed at lower ion energies by the sample stopping power, which was observed in Bi 2 Sr 2 CaCu 2 O 8+y [36].…”

“…A similar particle energy dependence of J c has been observed in Au-irradiated Ba(Fe,Co) 2 As 2 . 33) One of the possibilities is that defects are splayed at lower ion energies by the sample stopping power, which was observed in Bi 2 Sr 2 CaCu 2 O 8þy . 34) Splayed structure is more effective to suppress the motion of vortices than only parallel structure since magnetic relaxation via half-loop excitation becomes slower by forced entanglement of vortices, resulting in enhancement of J c .…”

Evidence of anisotropic vortex pinning by intrinsic and irradiation-induced defects in Ba(Fe,Co)2As2studied by quantitative magneto-optical imaging

“…The magnetic field dependence of J c in the as-grown sample is also accompanied by a puzzling behavior found in relaxation measurements [24,25]. We attribute these phenomena to the anisotropic pinning by as-grown planar defects, relating to the former behavior, and to the presence of defects correlated along the c-axis for the 'dip' feature, as also seen in magnetization experiments with high fluence HEHI irradiation [26].…”

Effects of heavy-ion irradiations in K-doped BaFe2As2

“…It is known that J c in superconductors can be further enhanced by introducing defects using swift particle irradiations [2]. In our previous studies, remarkable effects have been demonstrated in IBS using heavy-ions [3][4][5][6][7][8] and protons [9] into Co-doped Ba-122 single crystals. In these reports, we irradiated heavy-ions such as 200 MeV Au, 800 MeV Xe, and 2.6 GeV U to create columnar defects, which have excellent geometrical matching with vortices, and are expected to be ideal pinning centers.…”