Ferrimagnets are considered an excellent spintronic material candidate which combines ultrafast magnetic dynamics and straightforward electrical detectability. However, efficient routes toward magneto-ionic control of ferrimagnetic order remain elusive. In this study, a solid-state oxygen gating device was designed to control the magnetic properties of the ferrimagnetic CoTb alloy. Experimental results show that applying a small voltage can irreversibly tune a Tb-dominant device to a stable Co-dominant state and decrease the magnetization compensation temperature by 130 K. In addition, a reversible voltage control of the magnetization axis between out-of-plane and in-plane states is observed, which indicates that the migrated oxygen ions can bond to both Tb and Co sublattices. First-principles calculations indicate that voltage can dynamically control the flow-in and flow-out of oxygen ions that bond to the Co sublattice. Our work provides an effective means to manipulate ferrimagnetic order and contributes to the development of ultra-low-power spintronic devices.
Keywords: ferrimagnetic order; oxygen ion migration; rare-earth-transition-metal alloy; solid-state gate.