EPR Study of the Local Magnetic Field Distribution over the Bi2Sr2Ca1−xYxCu2O8+y Crystal Surface above the Superconducting Transition Temperature

The magnetic field distribution on the surface of the high-T c superconductor crystals Bi 2 Sr 2 Ca 1− x Y x Cu 2 O 8+ y has been studied in a wide temperature range using electron paramagnetic resonance (EPR) of the surface probe. The changes of the EPR signal broadening and shift with temperature and the probe-sample distance have been investigated. The analysis of obtained data made it possible to conclude that in the large temperature range above the critical temperature, some of the studied crystals are magnetized inhomogeneously. In the samples underdoped with charge carriers, the range is 40 K. Such samples contain inclusions with diamagnetic and paramagnetic magnetization. They are probably formed due to the electron phase separation.