STUDY OF MAGNETIC-PROPERTIES OF HTSC CERAMICS RBA2CU3O7-DELTA (R=Y, GD, DY, YB, EU) IN CONSTANT AND VARIABLE FIELDS

The magnetic properties (magnetization, magnetic hysteresis, magnetic susceptibility (chi1', chi1'', chi3') of HTSC ceramics RB12Cu3O7-delta (R = Y, Gd, Dy, Yb, Eu) are studied in temperature range 4,2 K less-than-or-equal-to T less-than-or-equal-to T(c) at constant (0 less-than-or-equal-to H less-than-or-equal-to 5.10(4) Oe) and variable (0.184 less-than-or-equal-to h0 less-than-or-equal-to 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 H(c2J) 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 H(c1J) and H(c2J) for these links.