The surface magnetization study of Cr$_{2}$O$_{3}$ by spin polarized low energy electron microscopy

The boundary magnetization at the surface of a Cr$_{2}$O$_{3}$ single crystal has been demonstrated by using spin-polarized low-energy electron microscopy (SPLEEM), indicating net surface spin polarization. This work shows that the placement of Cr$_{2}$O$_{3}$ single crystal in the single domain state, will result in net Cr$_{2}$O$_{3}$ spin polarization at the boundary, even in the presence of a gold overlayer. There are indications that the spin-polarized low-energy electron microscopy (SPLEEM) contrast for the two polarizations states is different. In addition, the boundary magnetization protected by the symmetry exists despite of the surface roughness/softness which was studied by the non-spin neutron reflectometry and low energy electron diffraction. Unoccupied surface oxygen sites and chromium sites are possible mechanism contributing to the surface ``softness,'' which will be discussed.