Surface termination dependent atomic relaxation of RT5 ultra-thin slabs (R = Y, Ce, Sm and T = Fe, Co, Ni) and their electronic and magnetic properties

Abstract

Investigations on two different surface terminated (0001) slabs of RT5 (R=Y, Ce, Sm and T=Fe, Co, Ni) compounds are performed by first principles calculations, in order to compare their structural stability, magnetic, and electronic properties. In bulk RT5 compounds, atomic sub-layers – RT2 (R-rich) and T3 (T-rich) – are alternatively stacked along z-axis. Therefore, two different RT5 (0001) slabs are constructed with terminating R-rich and T-rich sub-layers at both top and bottom of surfaces. Our calculations show that T-rich slabs are having higher structural stability owing to charge smoothing and inward relaxations of atoms at the surface, whereas R-atoms presented in the surface of slabs, particularly 4f elements experience outward relaxation as a consequence of corrugated surface charge density. The reason for inward and outward relaxations of respective atoms is quantitatively understood by the Bader charge analysis. Our results suggest that as the Co and Fe-rich surface slabs possess high structural stability and enhanced spin moment when compared to respective R-rich slabs, they can be potentially used for fabricating the multilayered exchange spring magnet.