Surface stability and H adsorption on the magnetic properties of SrCoO_2.5

Strontium cobalt oxide attracts great research attention because of its potential applications in electronic, magnetic, and energy devices. However, the surface reconstructions, electronic and spintronic properties are largely unknown because of its complexed crystal and spintronic structure that contains oxygen vacancy channels. Whether the electron counting model is applicable is also unknown. In this work, we compute the phase diagram and analyze surface reconstructions by a passivation scheme using a new approach to count the electrons based on each layer, which is verified by DFT calculations. Based on the most stable reconstructions, we discovered a coupling mechanism between the surface states and the thin film magnetic states. The surface magnetic properties can be tuned and both FM and AFM order can be obtained with different concentrations of H adsorption on the top surface. Our finding sheds light to the understanding of interplay between surface states and bulk magnetism in transition metal oxides.