Physicists pin down spin of surface atoms

A topographic map of a 4.8 Kelvin (-451ºF) copper surface with cobalt islands interspersed. The colors represent height above the copper in nanometers – billionths of a meter. Green specks on the islands are iron "adatoms," while iron adatoms on the copper surface appear blue. The map was obtained with a scanning tunneling microscope with a spin-polarized tip, an instrument that at the same time measured the spin of each iron atom. (Michael Crommie/UC Berkeley)