Diffusion studies of H of different charge states and their interplay with Co spin states in SrCoO_2.5

The tunable magnetism and reversible phase transformation have attracted vast research interest in liquid ion gated SrCoO_2.5 (SCO). Hydrogen atoms at different charge states may play important roles in the energy and spintronic devices, yet no systematic studies are available. How the hydrogen atoms at different diffusion pathways interplay with the spin states of Co atoms is also unknown. To answer the above questions, we used the climbing-image nudged elastic band method based on spin-polarized DFT to study various diffusion pathways of H at different charge states. The diffusion of proton is slightly faster than atomic H because no significant electron transfers occurs for proton. The fastest pathways of both charge states are near Sr-O layer because the ion of Sr is relatively inert. Due to the different symmetries of different sites along the pathway near the Co-O layers, the electron of the atomic H transfers to different Co sites and lead to magnetic fluctuations.