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 temperature, has been discovered in MnSb granular films. Granular films consisting of nanoscale MnSb dots were fabricated on a sulfur-passivated GaAs (0 0 1) substrate by molecular-beam epitaxy, then covered with an Sb thin layer. The MnSb granular films exhibit a strong in-plane anisotropy of the magnetic-field-sensitive current-voltage characteristics. When a constant voltage, above 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 magnetoresistive switch (MRS), is driven by the huge magnetoresistance effect under a relatively 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 the [11̄0] direction of the GaAs surface. The origin of the anisotropy is discussed in terms of the microscopic structural anisotropy at the heterointerface.