MAGNETIC-FIELD-INDUCED LOCALIZATION IN THE NORMAL-STATE OF SUPERCONDUCTING LA2-XSRXCUO4

Magnetoresistance measurements of highly underdoped superconducting La 2-xSrxCuO4 films with x = 0.051 and x = 0.048, performed in dc magneti c fields up to 20 T and at temperatures down to 40 mK, reveal a magnet ic-field-induced transition from weak to strong localization in the no rmal state. The normal-state conductances per CuO2 plane, measured at different fields in a single specimen, are found to collapse to one cu rve with the use of a single scaling parameter that is inversely propo rtional to the localization length. The scaling parameter extrapolates to zero near zero field and possibly at a finite field, suggesting th at in the zero-field limit the electronic states may be extended.