Observation of Enhanced Dynamic {\Delta}G effect near Ferromagnetic Resonance Frequency

Abstract

The field-dependence elastic modulus of magnetostrictive films, also called {\Delta}E or {\Delta}G effect, is crucial for ultrasensitive magnetic field sensors based on surface acoustic waves (SAWs). In spite of a lot of successful demonstrations, rare attention was paid to the frequency-dependence of {\Delta}E or {\Delta}G effect. In current work, shear horizontal-type SAW delay lines coated with a thin FeCoSiB layer have been studied at various frequencies upon applying magnetic fields. The change of shear modulus of FeCoSiB has been extracted by measuring the field-dependent phase shift of SAWs. It is found that the {\Delta}G effect is significantly enhanced at high-order harmonic frequencies close to the ferromagnetic resonance frequency, increasing by ~82% compared to that at the first SAW mode (128 MHz). In addition, the smaller the effective damping factor of magnetostrictive layer, the more pronounced {\Delta}G effect can be obtained, which is explained by our proposed dynamic magnetoelastic coupling model.