Enhancement of critical current density in helium ion irradiated Ba(Fe, Co)₂As₂ thin films

Abstract

The effect of 600 keV He + ion irradiation on the temperature and magnetic field dependence of the critical current density J C in high quality BaFe 1.84 Co 0.16 As 2 (Co-doped Ba122 type) thin films is investigated. The films are prepared by pulsed-laser-deposition (PLD) on CaF 2 (00 ) substrates. The irradiation dosages are varied in between 110 13 to 110 16 cm -2 . Upon irradiation, the superconducting transition temperature T C drops slightly from 23 K for the unirradiated sample to about 20 K for the sample with the highest irradiation level. The J C values of the thin film samples are calculated by using the Bean critical state model. The results showed that J C could be enhanced substantially. The maximum J C value at 4.5 K temperature is enhanced up to 2.4 MAcm -2 under 1 T field. The analysis of pinning force dependence on magnetic field shows that the pinning behavior is not changed in the irradiated samples, suggesting more pinning centers of similar nature to those of presented in the unirradiated samples are introduced by the irradiation process. The results indicate that the irradiation of light element ions He + with relatively low energy could increase the critical current density in iron based superconductors.

Effect of Silver Doping on the Superconducting and Structural Properties of YBCO Films Grown by PLD on Different Templates

“…Improving the superconducting and transport properties, in particular increasing the critical current density in a wide range of temperatures and magnetic fields, is one of the key issues in the field of applied superconductivity. In order to solve the issue, a large number of approaches and methods have been developed [ 4 , 5 , 6 , 7 , 8 ], among which the controlled creation of defects is still one of the most successful for achieving improved transport characteristics. Since the recent level of technology has reached, at least for the IBAD-based technical templates, an almost single crystalline quality, with an array of small-angle grain boundaries acting as natural defects, such defects are not dense enough to substantially increase the current transport capability for these superconductors in magnetic fields.…”