Magnetotransport study of the magnetic superconductorsGdSr2Ru1 − xCu2 + xO8

Abstract

Magnetotransport studies were carried out for the ruthenocupratesGdSr2Ru1 − xCu2 + xO8 (x = 0 and 0.05) in the temperature range 2–300 K and in fields up to 9 T. Theelectrical resistivity measurements near the superconducting region indicate thatthese compounds exhibit granular superconductivity. The magnetic field hassignificant effects on the intragranular superconducting transition temperature (T1) as well as the inter-granular superconducting transition temperature(T2) which can be attributed to the microstructure as well as the large internal fields present inthese compounds. The analysis of the magnetic field induced broadening of the resistivitytransitions in these compounds suggests a two-dimensional nature for the vortexlattice. The magnetoresistance in the normal state is in general negative andits magnitude reaches a maximum around the magnetic transition temperature(TM). A positive magnetoresistance is observed at low fields for temperatures belowTM in the parent compound which is absent in the Cu dopedcompound. The difference in the magnetoresistance behavior belowTM is argued to be due to the weakening of the antiferromagnetic order upon Cu doping.