Superconductivity and spin-glass like behavior in system with Pd sheet sandwiched between graphene sheets

Abstract

Pd-metal graphite (Pd-MG) has a layered structure, where each Pd sheet is sandwiched between adjacent graphene sheets. DC magnetization and AC magnetic susceptibility of Pd-MG have been measured using a SQUID magnetometer. Pd-MG undergoes a superconducting transition at $T_{c}$ ($= 3.63 \pm 0.04$ K). The superconductivity occurs in Pd sheets. The relaxation of $M_{ZFC}$ (aging), which is common to spin glass systems, is also observed below $T_{c}$. The relaxation rate $S(t)$ shows a peak at a characteristic time $t_{cr}$, which is longer than a wait time $t_{w}$. The irreversibility between $\chi_{ZFC}$ and $\chi_{FC}$ occurs well above $T_{c}$. The susceptibility $\chi_{FC}$ obeys a Curie-Weiss behavior with a negative Curie-Weiss temperature ($-13.1 \leq \Theta \leq -5.4$ K). The growth of antiferromagnetic order is limited by the disordered nature of nanographites, forming spin glass-like behavior at low temperatures in graphene sheets.