Hall-Effect Domain Detector

Abstract

Electrical readout of digital information transported by closed domains in magnetically uniaxial platelets requires sensing flux changes of 1–10 pWb emanating from an area 2–25 μm in diameter. Using an n-type epitaxial layer on a p-type silicon substrate we have developed a beam-leaded Hall-effect device suitable for sensing domains in orthoferrites. In these materials the minimal domain diameter is approximately 25 μm and the flux density is typically 0.01 T. Some properties of the Hall-effect detector are: active area ≈400 μm2, active thickness ≈1 μm, input and output resistance ≈1.5 kΩ, rated current Ir=8 mA, and risetime <50 nsec. Over the experimental range |B| ≤0.01 T and I≤Ir, the measured Hall voltage satisfied VH = (S0 - S2I2)IB, where S0≈16 V/A·T and S2≈ 3×104 V/A3·T. In detecting orthoferrite domains were have obtained 0.5 mV signals. We discuss the design and fabrication, the electrical and mechanical characteristics, and the limitations of the device. Improved detector performance is possible, and guidelines for its realization are given.