EPR search for vortex excitations in Bi2Sr2Ca1 − xYxCu2O8 + y crystals above the critical temperature
Excitations of the vortex type in the regions of temperatures both below and above critical temperature Tc are found by studying the local magnetic fields on the surface of Bi2Sr2Ca1 − xYxCu2O8 + y single crystals by means of EPR. The narrow EPR signal of the surface paramagnetic probe allows us to observe weak distortions of the magnetic field that arise when T > Tc. The behavior of the signal broadening agrees with the hypothesis about the existence of vortices in this temperature region.