Negative magnetoresistance in (InSb)1−xYx at low temperature

We report the low temperature negative magnetoresistance and magnetization of molecular beam epitaxy grown (InSb)1−xYx for a range of yttrium concentrations (0.03%⩽x⩽4.0%). Our experimental results from x-ray diffraction, Hall effect, and magnetization measurements suggest that the yttrium atoms are located as interstitials in the InSb lattice and hence do not hybridize their outer shell d electrons with the InSb band leading to localized moments. Although the magnetization versus magnetic field (B) data do not fit brilliouin function for all the temperatures studied, we clearly observe a correlation between the measured negative magnetoresistance and the magnetic moment. We believe that the s–d exchange interaction between the localized electrons of Y atoms and the conduction electrons gives rise to the large negative magnetoresistance observed. A theoretical model is used to explain the scattering mechanism. According to this model, when the conduction electrons in the lower subband of InSb have energy E smaller than the Zeeman splitting AM, where A is the s–d exchange integral and M is the magnetic moment, the lower subband conduction electrons are scattered from the d spins without changing their spin projections. On the other hand, as E becomes greater than AM, the spin-flip process can be thermally activated. For the conduction electrons in the upper subband, both spin-flip and spin-non-flip coexist. Therefore the model uses two distinctive relaxation times rather than just one. A numerical calculation is performed to fit the relation between the magnetoresistance and the magnetic moment of the yttrium atoms.