The performance of magnetoresisitive vector magnetometers with optimised conductor and anisotropy axis angles

Magnetoresistive sensors are made by photo-etching narrow linear folded tracks in vacuum-deposited permalloy film with uniaxial anisotropy. A large demagnetising field appears across each narrow strip in the resistive pattern: this and the presence of exchange energy, bias fields and the effects of anisotropy, combine to make the choice of optimum anisotropy and current flow directions complex. In the work described here the angular variations of the magnetisation vector at a series of points across the strip have been calculated. The inclusion of an exchange energy term allows the total energy to be determined and the behaviour of the model may be predicted for any combination of conductor angle, anisotropy skew and applied fields. Comparisons made with experimental values show close similarity of form but some quantitative discrepency. A simpler model, in which the permalloy film is assumed to be magnetised as a single domain and the magnetisation vector is constant across the strip is also evaluated.