MAGNETIC RESISTIVITY IN Bi₂Sr₂Ca(Cu_1-xCo_x)₂O_d EPITAXIAL THIN FILMS

Abstract

The scaling behavior of the effective activation energy of high-quality epitaxial c-oriented Bi 2 Sr 2 Ca ( Cu 1-x Co x ) 2 O d thin films with 0≤x ≤0.025 has been studied as a function of temperature and magnetic field. For all samples, the effective activation energy scales as U(T, μ o H)=Uo(1-T/T c ) m H n with exponent m=1.25±0.03, n=-1/2 and the field scaling 1/μ o H and -Uμ o H for thick films and ultra thin films, respectively. The results are discussed taking into account of the influence of the Co substitution with a model in which U(T, H) arises from plastic deformations of the viscous flux liquid above the vortex-glass transition temperature.