Magnetization reversal in 300 nm Co squares has been investigated by semiconductor transport magnetometry using a Hall bar containing a two-dimensional electron gas. In this technique the local field from a regular array of magnetic elements patterned on top of the Hall bar changes the measured longitudinal magnetoresistance, enabling the magnetization of the elements to be deduced. Hysteresis loops obtained from the magnetoresistance curve showed a zero magnetization state at zero applied field, which was confirmed by transmission electron microscopy imaging and micromagnetic modelling to represent a vortex state. Repeatable fields were found for vortex expulsion and re-entry, with strong dependence on element size but rather weak dependence on film thickness.
- Transmisson electron microscopy
- Image transmission
- Magnetization mearsurement