Effect of tilted magnetic fields on bistable nanomagnets in hybrid semiconductor/ferromagnet devices

Using the anisotropic Hall effect in a sub-micron lithographically well-def ined two-dimensional electron system we measure the stray field of individu al ferromagnetic nanoparticles in tilted magnetic fields. Our model calcula tions and experimental data show that one can map out the particle's hyster esis loop in great detail even if the field H-app is tilted away from the s pecimen's easy-axis by an angle phi(app) around 90 degrees. The investigate d Ni nanomagnets exhibit a well-defined remanent 'up'- and 'down'-state. Fo r the angular-dependent switching we find two different regimes: below a cr itical angle phi(c), the hysteresis loop is irreversible and squared, for p hi(c) < phi(app) less than or equal to 90 degrees it becomes partly reversi ble, but discontinuous jumps are still resolved. This characteristic switch ing behavior is found to depend on the nanomagnet's diameter. (C) 2000 Else vier Science B.V. All rights reserved.