It is known in the prior art that certain materials have significant change in Young's modulus of elasticity with applied magnetic field, known as the .DELTA.E-effect. However, practical use of the .DELTA.E-effect has not heretofore been introduced for electromechanical vibrating systems.
The frequency of vibration of a vibrating reed is known to be ##EQU1## where F.sub.N = FREQUENCY OF THE N-TH TONE
K.sub.n = constant dependent on n PA1 d = thickness of the reed PA1 l = length of the reed PA1 E = Young's modulus of elasticity PA1 .rho. = density of the material, and PA1 f.sub.1 :f.sub. 2 :f.sub.f.sub.3 :f.sub.f.sub.4 = (1.2).sup.2 :3.sup.2 :5.sup.2 7.sup.2, i.e., 1:6.26:17.5:34.4. PA1 (a) a large overall frequency range; PA1 (b) a high sensitivity in terms of the fractional frequency change produced by unit applied field; PA1 (c) a small hysteresis effect, so that a unique variation exists between frequency and applied field; PA1 (d) a high mechanical Q (or low damping), so as to obtain a sharply peaked resonance giving a well-defined operating frequency, and also so as to minimize the power needed to sustain the vibration of the system; PA1 (e) a small temperature coefficient of Young's modulus, so that the frequency of the system is not subject to drift resulting from a change in the ambient temperature. PA1 (a) various crystalline materials with large magnetostriction and small magnetocrystalline anisotropy energy, such as nickel and certain iron-cobalt alloys. PA1 (b) the amorphous ferromagnetic material Fe.sub.75 P.sub.15 C.sub.10. PA1 (a) by annealing in a magnetic field in the transverse direction, the .DELTA.E-effect is enhanced; PA1 (b) by annealing in the longitudinal direction, the .DELTA.E-effect is diminished. These statements are illustrated by the drawing of FIG. 11.