Electrical control of oxygen off-stoichiometry of transition-metal oxides at room temperature is a desired strategy to simultaneously switch the electrical conductance and magnetism of the device. Although the use of the electrochemical redox reaction of transition-metal oxides is the most reasonable way to achieve the aforementioned switch, such a device has not been realized because of the lack of a leakage-free liquid electrolyte. Here, we demonstrate an electromagnetic device that can reversibly switch a transition-metal oxide from an insulator/non-magnet to a metal/magnet (Tc=275 K) using a newly developed 'leakage-free electrolyte', incorporated in an amorphous NaTaO3 nanopillar array film. Reversible switching occurs electrically, obeying Faraday's laws of electrolysis, under a DC voltage of +(-)3 V within 2-3 s at RT. The present electromagnetic device does not have the drawback of liquid leakage, and the leakage-free electrolyte provides a novel design concept for practical electromagnetic devices using transition-metal oxides.

This is the pre-peer reviewed version of the following article: T. Katase, Y. Suzuki, and H. Ohta, Advanced Electronic Materials 2, 1600044 (2016)., which has been published in final form at http://onlinelibrary.wiley.com/wol1/doi/10.1002/aelm.201600044/abstract