Jump quantum phase transitions in a vortex sistem and the dinamiccomplex magnetic permeability of high-temperature binaryYBa-=SUB=-2-=/SUB=-Cu-=SUB=-3-=/SUB=-O-=SUB=-7-x-=/SUB=- superconductors

Abstract

A nonlocal high-frequency method for measuring the dynamic complex magneticpermeability with enhanced spatial resolution is developed to simultaneouslydetermine the bulk and local character of stepwise penetration of a magneticflux through twin boundaries (TBs) into a YBa2Cu3O7-x HTSC sample during itsstepwise decomposition into twins. By the values of fields corresponding tothe regions of steps, the thermodynamic first critical magnetic fields aredetermined: the penetration of a flux into a sample --- a Josephson medium;the development of a critical state in the Josephson medium; the penetrationof a flux into twins; and the values of the critical fields of phasetransitions in the vortex system of the HTSC sample, such as the meltingfields of a vortex crystal, the formation of a superconducting glass statein the sample, and the transition to the vortex glass and Bragg glassstates. Keywords: high-frequency inductance, bulk and local dynamic complexmagnetic permeability, magnetic flux trapping, effective demagnetizationfactor, twins (monodomains, crystallites, sub- and nanocrystallites), twinboundaries.\