EN
Electromagnetic properties of YBa_{2}Cu_{3}O_{y} samples melt-grown in air and doped with small amounts of light rare earth (LRE) ions Gd and Sm were studied. The LRE doping creates a point-like disorder contributing to the second peak on the magnetization curve. In the field range of the second peak the average magnetic moment, M_{av}, deduced from the magnetization curves exhibited strong fluctuations. M_{av} is commonly regarded as an equilibrium moment close to the thermodynamic reversible one, obeying in intermediate fields a logarithmic field dependence. However, in our experiments M_{av}(B) curves failed to follow such a dependence below irreversibility line. M_{av}(B) curves deduced from rather static measurements, done by SQUID magnetometer still showed the disturbance but significantly weaker. It indicates that this feature reflects the vortex dynamics in the second peak region. Its scaling with temperature was found to coincide with that of the pinning force.