A memory cell is provided with a pair of electrodes, and an active layer sandwiched between the electrodes and including a molecular system and ionic complexes distributed in the molecular system. The active layer having a high-impedance state and a low-impedance state switches from the high-impedance state to the low-impedance state when an amplitude of a writing signal exceeds a writing threshold level, to enable writing information into the memory cell. The active layer switches from the low-impedance state to the high-impedance state when an amplitude of an erasing signal having opposite polarity with respect to the writing signal exceeds an erasing threshold level, to enable erasing information from the memory cell.