Paramagnetic effect in YBa₂Cu₃O_7-x grain-boundary junctions

A detailed investigation of the magnetic response of YBa2Cu 3Ox grain-boundary Josephson junctions has been carried out using both radio-frequency measurements and scanning superconducting quantum interference device microscopy. In a nominally zero-field-cooled regime we observed a paramagnetic response at low external fields for 45° asymmetric grain boundaries. We argue that the observed phenomenology results from the d-wave order-parameter symmetry and depends on Andreev bound states.