In this paper a general model is presented to describe torque curves for a thin magnetic film with two anisotropy axes. One axis is assumed to lie in the plane of the film, having first-order anisotropy only, whereas the other one, having first- and second-order anisotropy, makes an arbitrary angle with the normal to the film. Given the parameters of the model, explicit expressions can be derived for both in-plane as well as perpendicular torque measurements with an infinite magnetic field. With some restrictions analytical expressions are derived to obtain the model parameters from the Fourier coefficients of experimentally obtained torque curves. Furthermore several methods are discussed to obtain finite-field corrections, including a power series expansion in the inverse magnetic field of the Fourier coefficients. An analytical expression was also derived to determine the direction of the easy axis. The applicability of the model is tested on a metal evaporated tape and we found it gave a consistent and quite accurate description of the torque curves of such a film. With this three-dimensional model the accuracy of the determination of the material parameters increases considerably, especially for the relatively weak transverse anisotropy of the film.
- SMI-TST: From 2006 in EWI-TST
- TSTNE-Magnet-TMM: Torque Magnetometer
- SMI-EXP: EXPERIMENTAL TECHNIQUES