Diffusing magnetic Tb impurities and magnetotransport in strongly spin-polarized Bi films

Abstract

As a contribution to electronic transport within strongly spin-polarized surface states and its modification by adsorption of magnetic impurities we studied the adsorption of Tb (atomic magnetic moment 10 μB) on epitaxial Bi(111) films by means of surface sensitive (magneto)conductance and low-energy electron diffraction. Surface diffusion turned out to be non-negligible even at substrate temperatures of 10 K. The Tb adatoms finally nucleate at intrinsic defects of the Bi(111) surface, where the Tb impurities act as dopants but not as scatterers. Nevertheless, time-dependent measurements allowed to determine also single-particle Tb scattering properties, as also supported by simulations of adsorption kinetics and time-dependent conductance. The magnetoconductance properties are characterized by small charge transfer (0.05 e/atom) and strong spin-orbit scattering, which in this case results only in strong reduction of the weak antilocalization effect but not a reversal to weak localization as for Fe and Co [see Lükermann, Sologub, Pfnür, Klein, Horn-von Hoegen, and Tegenkamp, Phys. Rev. B 86, 195432 (2012)]. Although Tb has a magnetic moment, which is by far higher than for adsorbed Fe and Co, it turns out that the f electrons of Tb play essentially no role in scattering of the conduction electrons, yielding an even smaller scattering cross section than that for Fe and Co. The adatom coordination (interstitial or on the surface) may also play an important role. © 2013 American Physical Society.