%0 Journal Article %J JOURNAL OF PHYSICS D-APPLIED PHYSICS %D 2006 %T Scanning tunnelling microscopy of surfaces of half-metals: an ab-initio study on NiMnSb(001) %A Lezaic, M. %A P. Mavropoulos %A Bihlmayer, G. %A Blugel, S %X We present a first-principles Study of the unreconstructed (001) surfaces of the half-metallic ferromagnet NiMnSb. Both terminations (MnSb and Ni) are considered. We find that half-metallicity is lost at the surfaces. After a discussion of the geometric relaxations and the spin-polarized surface band structure, we focus on topography images which are expected to be found with spin-polarized scanning tunnelling microscopy. For the MnSb-terrninated surface we find that only the Sb atoms are visible, reflecting a geometric buckling caused by relaxations. For the Ni-terminated surface we find a strong contrast between the images of forward and reverse tip-sample-bias of 0.5 eV, as well as a stripe-like image for reverse bias. We interpret these findings in terms of highly directional Surface states which are formed in the spin-down gap region. %B JOURNAL OF PHYSICS D-APPLIED PHYSICS %V 39 %P 797-802 %8 MAR 7 %G eng %R 10.1088/0022-3727/39/5/S05