Transport Properties of New High-T_c Superconductors Ln_2-x+yCe_xBa_2-yCu₃O_10-δ (Ln=Nd, Eu)

Abstract

Transport properties were investigated for the new high- T c superconductors Ln 2- x + y Ce x Ba 2- y Cu 3 O 10-δ (Ln=Nd, Eu) with T c in the 30 K range. Hall coefficients for these compounds are positive, indicating a hole conduction and are slightly temperature dependent with a broad maximum around 120 K. Average hole number per copper ion in the Cu-O planes estimated from the Hall coefficient just above T c is 0.09, which is considerably lower than that of 0.23 in YBa 2 Cu 3 O 7- y . This may be the reason why T c in Ln 2- x + y Ce x Ba 2- y Cu 3 O 10-δ is as low as 30 K. If we adopt midpoints of the resistive transition as T c in the magnetic field, the upper critical field at absolute zero for the europium compound is estimated as 22 Tesla.