A novel reentrant susceptibility due to vortex and magnetic dipole interaction in a La1.85Sr0.15CuO4 and Gd2O3 composite system

A reentrant behavior of temperature dependent magnetic ac-susceptibility (or excess susceptibility(ES)) at lower temperature is observed in a composite made of superconductor $L{a}_{1.85}S{r}_{0.15}Cu{O}_4$ (LCu) and an insulating paramagnetic salt $G{d}_2{O}_3$ (GdO). The ES exhibits an exponential characteristic that varies with temperature ($\exp ,[\frac{T_0}{T}]$), T0 is characteristics temperature. The characteristics temperature,T${}_0$, decreases as the effective interface diminishes and the amplitude of the dc magnetic field increases. The creation of ferromagnetic dimers between Gd${}^{+3}$ ions in GdO is observed as a result of vortex-dipole interaction, which causes the observation of this unusual ES at temperatures much lower than the superconducting onset temperature T${}_S^{onset}$. This type of ferromagnetic dimer formation much below superconducting transition temperature is found comparable with the formation of Yu-Shiba-Rusinov (YSR) state and interaction between these YSR state.