Study of magnetic properties of HTSC ceramics R Ba2 Cu3 O7-δ (R=Y, Gd, Dy, Yb, Eu) in constant and variable fields

The magnetic properties (magnetization, magnetic hysteresis, magnetic susceptibility (χ'1, χ'1', χ'3) of HTSC ceramics R Ba2 Cu3 O7-δ (R=Y,Gd,Dy,Yb,Eu) are studied in temperature range 4,2 K≤T≤Tc at constant (0≤H≤5·104 Oe) and variable (0,184≤h0≤36.8 Oe) fields as well as with their combined action. Most attention is concentrated on the processes in weak links. It is found that the second critical field of weak links Hc2j is analogous to the field of full penetration for superconducting granules, H*g.The temperature-field dependences of susceptibility display a number of peculiar features indicative of the existence of the hierarchy of weak links, i.e. the existence of distribution function of Hc1j and Hc2j for these links