Semiconductor-metal hybrid structures as local magnetic-field probes: Magnetoresistance and spatial sensitivity profile

Tailored nonmagnetic semiconductor-metal hybrid structures exhibit a large magnetoresistance effect in a homogeneous magnetic field. This is the so-called extraordinary magnetoresistance effect. Here, we study numerically the magnetoresistance of such hybrid structures in the inhomogeneous field of a magnetic dot. Surprisingly, the four-point resistance R versus magnetic field B changes its symmetry if compared to the case of a homogeneous field and is strongly dependent on the position of the local magnetic field. Interestingly, the active device area is not defined by the voltage probe separation, but by the positioning of voltage probes and current leads. We find a magnetoresistance effect as large as 18% although only 1/60 of the device area is subject to a small magnetic field of +/- 50 mT. These results are promising for sensing magnetic-field distributions in the nanoscale regime such as the stray fields of magnetic recording media. (C) 2005 American Institute of Physics.