SPIN-DISORDER SCATTERING IN EUROPIUM-DOPED INDIUM-ANTIMONIDE THIN-FILMS

We have studied the low temperature magnetoresistance of In1-xEuxSb for a range of europium concentrations. We find that the addition of the rare earth element reduces the carrier mobility substantially and alters dramatically the character of the magnetoresistance. In particular, we observe negative magnetoresistance for 0.012 < x < 0.05. We attribute this to a predominance of scattering of the conduction electrons by the magnetic spins of the europium atoms, a scattering process which becomes less effective as the spins align with the magnetic field. For the most lightly doped sample, the magnetoresistance becomes positive at high fields, indicating complete saturation of the spin alignment and appearance of normal (classical) magnetoresistance. In addition, for samples not too heavily doped with europium, the magnetoresistance for very low fields (less than 0.5 T) is small and positive before reaching a maximum and evolving into a negative magnetoresistance. This behavior, similar to that seen in EuSe, is thought to be due to a redistribution of the conduction electrons in the spin-split electronic energy levels.