Characterization of individual nanomagnets by the local Hall effect

We describe a straightforward approach to the characterization of individual thin-film NiFe ferromagnets, useful from cryogenic to room temperature. The technique is based upon the local Hall effect (LHE), in which strong fringe fields present near the edge of a ferromagnet induce a Hall voltage in a nanoscale semiconducting cross-junction. Hysteresis loops are obtained for individual nanomagnets of widths ranging from 1 mu m to less than 100 nm. The LHE is an intrinsically non-perturbative technique, ideal for application to soft ferromagnetic systems. We anticipate that the theoretical sensitivity of this arrangement can rival that of thin-film SQUID susceptometers, with the added benefit that it is simpler and does not require low temperatures. (C) 1999 Published by Elsevier Science B.V. All rights reserved.