Investigation of magnetic properties of HTS ceramics RBa2Cu3O7–<i>δ</i> (R = Y,Gd,Dy,Yb,Eu) in constant and varying fields

The magnetic properties (magnetization, magnetic hysteresis, magnetic susceptibility χ1′,χ2′,χ3′ of HTS ceramic RBa2Cu3O7–δ (R = Y, Gd, Dy, Yb, Eu) are studied in constant (0 ⩽ H ⩽5 · 104 Oe) and varying (0.184 ⩽ h0 ⩽ 36.8 Oe) fields, as well as under the combined action of the fields H and h0 in the temperature interval 4.2 K ⩽ T ⩽ Tc. Principal attention is paid to investigations of weak bond processes. It is found that the upper critical field Hc2J for weak bonds is an analog of the field Hg∗ corresponding to complete penetration of the superconducting granules. The temperature-field dependences of susceptibility display a number of singularities that point toward a hierarchy of weak bonds, i.e., toward the existence of distribution functions of critical fields Hc1J and Hc2J for one latter.

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