Hall and bend-resistance magnetometry on two-micromagnet systems

The stray field of permalloy (Py) micromagnets has been measured by means of a micrometer-sized Hall magnetometer incorporating a ballistic two-dimensional electron system. In particular, ferromagnetic specimens have been investigated where two micromagnets were separated by a sub-mum gap. The two 20 nm thick Py micromagnets had lateral sizes of 1 x 1 mum(2) and 1 x 2 mum(2). The separation gaps were 200, 300, and 500 rim. The measured Hall curve, which gives the averaged value of the stray field in the cross junction, is hysteretic and reflects the micromagnetic behavior. Systematic changes, most likely indicating magnetostatic interaction, are observed as a function of the separation gap. We show that bend-resistance measurements performed on the same magnetometer give a higher spatial resolution and, thereby, resolve the reversal processes in greater detail than the Hall measurements.