140 MeV Si-ION IRRADIATION INDUCED T_c ENHANCEMENT IN YBCO THIN FILMS

Abstract

On-line resistance measurement in a temperature range of 78 K to 124 K was performed on epitaxial thin films of YBCO irradiated with 140 MeV Si ions. The superconducting transition temperature (Tc), resistivity at 100 K (ρ 100 k ) and transition width (∆Tc) all show peak at a fluence of 1.5 × 10 13 ions/cm 2 . A crystallochemical analysis based on metastability induced charge and spin fluctuation due to irradiation induced oxygen disorder in the CuO chains explains the Tc enhancement in the low fluence regime. 79 Mod. Phys. Lett. B 1999.13:79-87. Downloaded from www.worldscientific.com by MONASH UNIVERSITY on 02/05/15. For personal use only.

Effect of ?-Irradiation on Superconductivity in Polycrystalline YBa2Cu3O7-?

“…This means that some concurrent mechanism, which cause an increase in T c , come into play. [32] was not, however, connected with the granular structure of the sample. 3).…”

“…Explanations of the effect in Ref. [32] was not however connected with granular structure of sample. In Ref.…”

“…3), and this is fairly surprising. For example, an increase in T c after low-dose irradiation with Si ions was observed in polycrystalline YBCO [32]. This mechanism shows itself only in a limited range of doses, since T c decreases again in the range above F > 120 MR (Fig.…”

“…There are known some cases of superconductivity enhancement in polycrystalline HTSCs under irradiation. For example, an increase in T c after low-dose irradiation with Si ions was observed in polycrystalline YBCO [32].…”

Selective disorder in the CuO basal planes of YBa2Cu3O7−y by swift heavy ion induced secondary electrons

“…The superconducting transition, which shifts to lower temperatures after irradiation at 79 K, tends to recover to the pre-irradiation value on annealing the film at 297 K. In the low-fluence regime (Fig. 3a), the T c and T c0 obtained after irradiation at the fluence of 1 Â 10 10 ions cm À2 , increased even beyond that of the pristine sample on annealing at 297 K. This unusual behaviour has also been seen in a few high temperature superconducting systems under ion irradiation [21,22] and electron irradiation [23,24]. In the high-fluence regime, the T c1 and T c2 also tend to approach their pre-irradiation values on annealing the irradiated film at 297 K (Fig.…”