Magnetic characterization of a hydrogen phase trapped inside deep dislocation cores in a hydrogen-cycled PdHx (x approximate to 4.5X10(-4)) single crystal

摘要

The magnetic characterization of Pd single crystals deformed by cycling in a hydrogen atmosphere has been performed. Based on evidence obtained from thermal desorption analysis, it is shown that the condensed hydrogen phase formed inside deep dislocation cores in PdHx (x = H/Pd approximate to 4.5 x 10(-4)) is tightly bound with a Pd matrix. The activation energy of hydrogen desorption from these cores was found to be as high as e = 1.6 eV/H-atom, suggesting the occurrence of a strong band overlapping between Pd and H atoms. SQUID measurements carried out in a weak magnetic field (H < 5.0 Oe) showed an anomalous diamagnetic contribution to the DC and AC magnetic susceptibilities of the PdHx sample at T < 30 K resulting in the presence of the hydrogen phase. It is suggested that the anomalous diamagnetic response in PdHx is caused by the presence of a hydrogen dominant phase, tightly bound with a Pd matrix inside the dislocation cores (nanotubes).