Effects of Tl content and magnetic field on phase formation of TlmBa2Can-1CunO2n+2+δ (m=1 and 2, n=4) superconductors

Abstract

The effect of Tl content in TlmBa2Can-1CunO2n+2+δ (TBCCO) superconductor was studied with m=1 and 2, n = 1-4. Samples were prepared using the standard solid-state reaction one-step technique in a sealed quartz tube under normal pressure. The superconductivity was examined using electrical resistance measurements ranging from 300 K to 10 K. The effect of an applied magnetic field (up to 12 T) on the transition behavior has been studied. The transition width, ∆T, was increased sharply with a slight increase in the magnetic field, and then increased smoothly when the magnetic field increased significantly. The vorticity activation energy U(B) was studied as a function of magnetic field B. The value of U(B) was determined from the slope of the relationship ln (RB/R0) = - U(B)/kB T. Transport measurements indicated that the values of superconducting transition temperature of the samples depend on the Tl content. The values of the transition temperature, Tc, and activation energy U(B) of the samples decreased with increasing Tl content. The possible causes of the observed behavior in the superconducting and magnetic properties of Tl-1234 & Tl-2234 due to the Tl content are discussed.