Influence of the magnetomechanical pole-effect on the behavior of thin vibrating reeds

It is demonstrated that the vibration frequencies of a magnetized reed can be sensibly affected by a magnetic field, due to the restoring force exerted on the moving pole. A simplified theory of this effect is developed which gives reasonable agreement with experimental observations. The relative importance of the pole-effect depends on the geometry of the reed and increases with the ratio of length to thickness. The effect decreases rapidly for higher overtones. Unlike the magnetization, the pole-effect does not saturate but rather increases steadily in post-saturation fields, where it is conveniently separated from the ΔE-effect on which it is generally superimposed. For the geometries typically employed in the investigation of liquid-quenched amorphous alloys, the pole-effect can be large for the fundamental mode and may be used to determine the temperature dependence of the magnetization. If unrecognized, on the other hand, the pole-effect can cause anomalies in the magnitude of the apparent elastic constant, and especially in the temperature dependence exhibited in the vicinity of the Curie point.