Conduction-Band Tunneling and Electron-Spin Polarization in Field Emission from Magnetically Ordered Europium Sulfide on Tungsten

Abstract

We measured the temperature dependence of the current and spin polarization, and determined the work functions from Fowler-Nordheim plots. The current increases exponentially with decreasing temperature. Work-function data can be related directly to the height of the internal W-EuS barrier. This barrier is lowered by magnetic splitting of the EuS conduction band for one electron-spin state which should lead to a spin polarization of unity. The measured spin polarization, however, is equal to the polarization of the $4{f}^{7}$ electrons of europium.