This dataset contains the information on our recent body of work on transition-metal oxide-based magneto-ionics and all the relevant data files. In this work, we propose a nanoscale-engineered magneto-ionic architecture (comprising a thin solid electrolyte in contact with a liquid electrolyte), that drastically enhances cyclability while preserving sufficiently high electric fields to trigger ion motion. Specifically, we show that the insertion of a highly nanostructured (amorphous-like) Ta layer (with suitable thickness and electric resistivity) between a magneto-ionic target material (i.e., Co3O4) and the liquid electrolyte, increases magneto-ionic cyclability from < 30 cycles (when no Ta is inserted) to more than 800 cycles. The Ta layer is effective in trapping oxygen and hindering O2– ions from moving into the liquid electrolyte, thus keeping O2– motion mainly restricted between Co3O4 and Ta when voltage of alternating polarity is applied. We demonstrate that this approach provides a suitable strategy to boost magneto-ionics by combining the benefits of solid and liquid electrolytes in a synergetic manner.

1. Description of methods used for collection-generation of data:
   Various experimental tools were employed in this line of work, such as magnetron sputter for the materials growth, magnetometry for magneto-electric study, X-ray diffraction and transmission electron microscopy for structural and microstructural inspections, and Variable energy positron annihilation lifetime spectroscopy (VEPALS)for defect analysis [Regulating oxygen ion transport at the nanoscale to enable highly cyclable magneto-ionic control of magnetism, ACS Nano, 2023, DOI: 10.1021/acsnano.3c01105].

2. Methods for processing the data:
   The data files can be processed using Origin software, PowerPoint, and DigitalMicrograph.

3. Instrument- or software- specific information needed to interpret the data: For the magnetometry data, any antiferromagnetic signals were subtracted using the VSM software in our lab. The format of this dataset was converted into an open format that can be processed using Origin software.

4. Instruments, calibration and standards information: The VSM magnetometer was calibrated using a standard nickel pallet provided by the company (Micro Sense, LOT, Quantum Design).

5. Environmental or experimental conditions: The measurements were conducted at ambient conditions.

6. Quality-assurance procedures performed on the data: The results were carefully analyzed and interpreted. Peer review process of the corresponding scientific article by experts in this field has been done, and its imminent publication in ACS Nano is expected.