Static and Dynamic Behavior of Thin Permalloy Films

Thin magnetic films (∼1000 A) evaporated onto a heated glass substrate in the presence of a dc magnetic field develop a uniaxial magnetic anisotropy energy of the form $E_k\mathrm{=K}{\sin }^2\phi$ , with φ measured from the deposition field. Such films promise to outperform ferrite cores in digital‐computer memory‐systems by several orders of magnitude. A detailed static and dynamic theory based on the above anisotropy energy and the Landau‐Lifshitz dynamical equation is presented. The static theory contains the unique feature of the coercive force parallel to the easy axis being dependent on a field in the plane of the film and perpendicular to the easy axis. Experimental verification of the theory is given. The dynamic theory considers both steady‐state and pulse response. The steady‐state solution is well known; the pulse solution must take very careful account of all the important torques acting in a switching experiment, and numerical results are obtained by the use of a digital computer. Experimentally, steady‐state resonance is measured from 100 to 10 000 Mc and pulse switching down to 3 mμsec. Both types of experiment are in good agreement with each other and with the theory.