PINNING PHENOMENA AND CRITICAL-CURRENT IN PROTON-IRRADIATED SINTERED YBA2CU3O7-DELTA

In this contribution we deal with proton-irradiation effects on YBa2Cu 3O7-delta sintered samples. We irradiated slab-shaped samples with 3.5 and 6.5 MeV proton beams and with fluences ranging from 1.8x10(16) p/ cm(2) to 8.6x10(16) p/cm(2). We analyzed either intragranular or inter granular properties before and after irradiation by means of magnetic and electric transport measurements. We found that it is possible to e nhance both intragranular and intergranular critical current densities with proton irradiation. The optimal ranges of fluences for enhancing intragranular and intergranular J(c) are different. By focusing our a ttention on the possibility of enhancing the transport J(c) of bulk ma terials we show that suitable proton induced defects significantly con tribute to the pinning of vortices in intergrain networks, as it is de monstrated by means of different experimental techniques and on differ ent sets of samples. We observed that the enhancement presents nonmono tonic behavior. On the contrary, modulations as a function of field an d temperature emerge. Moreover, low temperature magnetization measurem ents either show modulations of the intergrain critical current densit y as a function of field or the appearance of plateaulike features. Th ese results are discussed in the framework of static properties of dis ordered long Josephson junctions networks.