Hall Sensors

The experimental technique is based on the measurement of local magnetic field across a sample using arrays of microscopic Hall sensors. The active layer in these sensors is a 2DEG formed at the interface of GaAs/AlGaAs heterostructures. The sensors are defined photolithographically, as shown schematically above, with typical size of each sensor of 3 µm to 10 µm. The current is driven through all the sensors and the corresponding Hall voltage of each sensor is directly proportional to the perpendicular component of the local magnetic field within the active area of the sensor. The superconductor crystals are placed directly onto the surface of the GaAs wafer. Since the 2DEG resides only about 1000 Å below the surface, this technique allows a very sensitive mapping of the local magnetic field across the sample. The techniques has been used to study both ac and dc local field behavior as well as for the investigation of the self-induced magnetic field of a transport current.

For additional information, see:

• Transport Properties Governed by Surface Barriers in Bi₂Sr₂CaCu₂O₈
  D. T. Fuchs, E. Zeldov, M. Rappaport, T. Tamegai, S. Ooi, and H. Shtrikman
  Nature 391, pp. 373-376 (1998).
• Local Magnetization Measurements in High Temperature Superconductors
  D. Majer, E. Zeldov, H. Shtrikman, and M. Konczykowski
  "Coherence in High Temperature Superconductors", eds. G. Deutscher and A. Revcolevschi, World Scientific (Singapore, 1996) pp. 271-296.
• Separation of Irreversibility and Melting Lines in Bi₂Sr₂CaCu₂O₈
  D. Majer, E. Zeldov, and M. Konczykowski
  Phys. Rev. Lett. 75, pp. 1166-1169 (1995).
• Thermodynamic Observation of First-Order Vortex-Lattice Melting Transition in Bi₂Sr₂CaCu₂O₈
  E. Zeldov, D. Majer, M. Konczykowski, V. B. Geshkenbein, V. M. Vinokur, and H. Shtrikman
  Nature 375, pp. 373-376 (1995).