A criterion for determination of the upper critical fields H-=SUB=-c2-=/SUB=- in YBCO thin films with different ion irradiation doses

Magnetotransport measurements were carried out for YBa 2 Cu 3 O 7-x (YBCO) thin films in external perpendicular magnetic fields of H. The studies performed both the virgin samples and irradiated ones. Xenon ions used as an irradiation. Thus we studied features broadening superconducting transition YBCO (virgin irradiated). drop was analyzed depending on field H, well irradiation dose n D . When processing experimental data R(H,T), a criterion determination temperature dependence upper critical H c2 (T). defect concentration film corresponding to certain value It found that sample, should be determined by resistance level R=0.4R N inside transition, where R =R(T=100 K). With gradual increase , this decreases. At sufficiently high radiation doses >7·10 12 cm -2 (T) phase line R~0. Keywords: films, HTSC, xenon ion irradiation, magnetotransport studies, field, line, Tinkham's formula, Abrikosov vortices.