Multiple Magnetoionic Regimes in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:msub><mml:mi>Ta/Co</mml:mi><mml:mn>20</mml:mn></mml:msub><mml:msub><mml:mi>Fe</mml:mi><mml:mn>60</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">B</mml:mi><mml:mn>20</mml:mn></mml:msub><mml:mo>/</mml:mo><mml:msub><mml:mrow><mml:mi>Hf</mml:mi><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:math>

In ${\mathrm{Ta/(Co,Fe)B/HfO}}_{2}$ stacks, a gate voltage drives, in nonvolatile way, the system from an underoxidized state exhibiting in-plane anisotropy (IPA) to optimum oxidation level resulting perpendicular (PMA) and further into overoxidized with IPA. The $\mathrm{IPA}\phantom{\rule{0.1em}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{0.1em}{0ex}}\mathrm{PMA}$ regime is found be significantly faster than $\mathrm{PMA}\phantom{\rule{0.1em}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{0.1em}{0ex}}\mathrm{IPA}$ regime, whereas only latter shows full reversibility under same voltages. effective damping parameter also marked dependence going 0.029 0.012, modest increase 0.014 regime. existence of two magnetoionic regimes has been linked difference chemical environment anchoring points oxygen species added or layers. Our results show that multiple can exist single device their characterization great importance for design high-performance spintronics devices.