Anomalous behavior in the spin polarization of low-energy secondary electrons from Gd(0001).

Abstract

We have measured the spin-polarization spectrum of low-energy secondary electrons from the surface of thick single-crystalline Gd(0001) films grown on W(110). Below 1.5 eV an anomalous decrease in the polarization is observed and is attributed to the presence of the 4${\mathit{f}}^{8}$ states just above the vacuum level, which leads to increased emission of spin-down electrons. Between 1.5 and 7 eV the spin polarization remains nearly constant at about 33% (at 150 K), demonstrating that the phenomenon of polarization enhancement for low-energy secondary electrons is not universal. The observed large polarizations indicate that the completely polarized 4f electrons contribute significantly to the secondary-electron yield.