PURPOSE: To improve the output of a high order harmonic wave and its sharpness and to easily identify many kinds of waves by constituting a magnetic layer so that magnetic powder having saturated magnetic flux density more than a specific value are dispersed into a binder in the magnetic layer.

CONSTITUTION: A base material C consists of a sheet 6' notched so as to hold space in which a ductile stripe 2 consisting of a ferro-magnetic magnetic distortion material can be mechanically resonated and a sheet 6 having no notch and is allowed to store the stripe 2 by sticking the material C to a non-magnetic backing B forming a magnetic layer 4 on its surface. Since the layer 4 is formed so as to control the intensity of a magnetic field in the thickness distance of the backing B, the saturated magnetic flux density of magnetic powder in the layer 4 is preferably set up to >100emu/g, an especially preferable value is >120emu/g. Thereby the resonance frequency of the ductile stripe 2 can be controlled by the use of a digital magnetic recording system and the volume of recording information can be increased by using plural stripes 2.