MAGNETIC CHARACTERIZATION OF A HYDROGEN PHASE TRAPPED INSIDE DEEP DISLOCATION CORES IN A HYDROGEN-CYCLED PdH_x (x\approx 4.5\cdot 10^-4) SINGLE CRYSTAL
Lipson A.G., Heuser B.J., Castano C.H., Lyakhov B.F., Tsivadze A.Yu.

Received: March 23, 2006

PACS: 74.78.Fk, 74.10.+v, 61.72.-y

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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 PdH_x () 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 PdH_x sample at T<30 K resulting in the presence of the hydrogen phase. It is suggested that the anomalous diamagnetic response in PdH_x is caused by the presence of a hydrogen dominant phase, tightly bound with a Pd matrix inside the dislocation cores (``nanotubes'').