Magnetic penetration depth in K-doped Bi-2212 Bi 2Sr 2CaCu 2− xK xO 8+ δ: ESR study

Abstract

We report here on the electron spin resonance (ESR) study of paramagnetic probe adsorbed on the surface of K-doped polycrystalline Bi 2Sr 2CaCu 2− x K x O 8+ δ ( x=0.5–0.7) carried out in the temperature range 77–300 K. The T cs of the samples found to increase with Cu (K) subtraction (addition). From the Brandt's model for triangular vortex lattice, the widths of the observed ESR lines below T c are related to the penetration depth. From the analysis of temperature dependence of λ, penetration depth at zero temperature ( λ 0) is estimated. The results are explained using BCS clean limit and dirty limit models.