Spin Polarization of Field-Emitted Electrons and Magnetism at the (100) Surface of Ni

The electron spin polarization of field-emitted electrons from atomically clean, field-evaporated in ultrahigh vacuum, single-crystal Ni tips has been measured with the probe hole selecting emission from the high-work-function (100) plane. We find P=(-3.0±1)% (magnetic moment antiparallel to the magnetization of the crystal). From an analysis of these and recent photoemission data we conclude that the magnetic (and electronic) properties of the surface and bulk Ni must be very similar.