Small-Signal Mixing and Harmonic Generation in Thin Magnetic Films

Abstract

A method is developed for calculating the response of a thin magnetic film subjected to static magnetic fields and small time‐varying fields. An applied field is considered small if it produces rotations, φ₁ of M_s such that sin2φ₁≈2φ₁ and cos2φ₁≈1. The measured response is the time derivative of that component of flux which arises from M_s. A component of this flux change generates a voltage in a conductor held close to the film. It is shown that this sensed voltage contains not only the frequency of the applied field but also its harmonics. Independent variables are chosen to be the magnitude and direction of the static field and the direction of the small time‐varying fields. General expressions for the output voltage generated by the film at fundamental and second‐haramonic frequencies are developed. Theoretically predicted signal behavior is illustrated by fixing two of the independent variables and plotting the dependence of output voltage on the remaining variable.