Hysteresis of Microwave Absorption and Magnetic Moments of High Temperature Superconductors: a Vortex Model

A quantitative description is given of magnetic hysteresis for the series of superconductors with structure MBa2Cu3O7, where M = Y, Er, Dy, Ho, Lu, Tm, and Gd. A model for understanding the origin of ESR baseline changes when hysteresis occurs is developed. A comparison is made between the microwave absorption detected by an ESR spectrometer using the modulation technique and that measured directly through the variation of the quality factor of a microwave cavity when the external field is changed. A physical model based on the hypothesis of vortices with a broad loop distribution is suggested in order to reveal the connection between the various hysteresis effects and the spin-glass properties. The vortex and recently proposed pinning force models are briefly compared. (C.D.)