Spin-polarized field emission from Cr thin film deposited on W⟨0 0 1⟩ tips

To generate high and stable spin-polarized electron beams by field-emission for applications to electron microscopy and spectroscopy, we demonstrated spin-polarized field-emitted electrons from a Cr thin film deposited on W < 0 0 1 > tips at room temperature without an external magnetic field. A spin polarization of the field-emitted electrons of 35-50% was achieved when the Cr thickness was higher than 20 nm. In addition, a maximum spin polarization of 50% was achieved, consistent with the value for a Cr(0 0 1) surface expected by first-principles calculations. The polarization direction was also stable for 3 h with no abrupt change. This study indicates that antiferromagnetic Cr is proper cathode material for a field emitter than other ferromagnetic materials with an instability limited by superparamagnetic state.