Paramagnetic Meissner effect in electrochemically doped Indium-Tin Oxide films

Transparent conductive indium tin oxide (ITO) thin films, electrochemically intercalated with alkali (Li$^{+}$, Na$^{+}$, K$^{+}$, Rb$^{+}$, Cs$^{+})$, alkali earth (Mg$^{+2}$, Ca$^{+2})$, or complex NH$_{4}^{+}$ ions show tunable superconducting transition with dome shape behavior of $T_{c}$ versus electron density around the maximum at 5 K. The zero resistance transition in superconducting state is accompanied with paramagnetic Meissner response to the applied external magnetic field, i.e. the increase of magnetization in field cooling regime. We provide extensive evidences of flax trapping using dc SQUID, ac susceptibility and transport measurements. In particular, we present evidence that the paramagnetic response results from the lower $T_{c}$ on the center of disk samples than on the edges leading to the trapping of magnetic flax in the center, and that change of $T_{c}$ profile to opposite removes the paramagnetic response. The flux trapped state is metastable. An alteration of external magnetic field destroys the giant vortex..