ESR and Nonresonant Microwave Absorption in a High-TcSuperconductor of the Tl-Ba-Ca-Cu-O System

Abstract
Electron spin resonance (ESR) in a high-Tcsuperconductor of the Tl-Ba-Ca-Cu-O system is observed. Two components of ESR exist. Above 140 K, the intensity of the ESR signal increases as the temperature decreases. Below 140 K, the signal intensity decreases as the temperature decreases and disappears atTc(124 K), clearly indicating the relation to the superconductivity. Nonresonant absorption is greatly enhanced atTc. BelowTc, an abrupt change in the derivative curve of the nonresonant microwave absorption occurs at the magnetic field corresponding to the lower critical field.