Magnetoresistive switch effect in MnSb granular films grown on sulfur-passivated GaAs: more-than 10 000% magnetoresistance effect at room-temperature

A huge positive magnetoresistance effect, more than 10 000% at room tempera ture, has been discovered in MnSb granular films. Granular films consisting of nanoscale MnSb dots were fabricated on a sulfur-passivated GaAs (001) s ubstrate by molecular-beam epitaxy, then covered with an Sb thin layer. The MnSb granular films exhibit a strong in-plane anisotropy of the magnetic-f ield-sensitive current-voltage characteristics. When a constant voltage, ab ove the threshold value, is applied in the [1 1 0] direction of the GaAs (0 0 1) surface, a steep change in the current, which we term magnetoresistiv e switch (MRS), is driven by the huge magnetoresistance effect under a rela tively low magnetic field (less than about 0.2 T). On the other hand, less than 1% magnetoresistance effect was observed when the voltage was applied in thr [1 10] direction of the GaAs surface. The origin of the anisotropy i s discussed in terms of the microscopic structural anisotropy at the hetero interface. (C) 2001 Elsevier Science B.V. All rights reserved.