Magnetoresistance Measurements of Single-Crystal LnBa₂Cu₃O_<i>y</i>(Ln=Ho, Dy, Eu and Y) under Pulsed High Magnetic Field

Abstract

The high-field magnetoresistance of well-characterized LnBa 2 Cu 3 O y (Ln=Ho, Dy, Eu and Y) single crystals has been measured from 4.2 K to 300 K under a pulsed magnetic field up to 60 T. The upper critical field H c2 is well sketched by the usual anisotropic BCS model and the normal resistivity down to liquid helium temperature shows that the system can be regarded as normal metal with positive magnetoresistance. The residual resistivity is between 10 and 50 µΩ cm, reflecting a highly qualified sample preparation. The relations among upper critical field, coherence length and normal resistivity are discussed. It is concluded that the magnetic rare-earth ions Ho and Dy enhance H c2 without affecting T c .