Observation of enhanced dynamic ΔG effect near ferromagnetic resonance frequency

Abstract

The field-dependence elastic modulus of magnetostrictive films, also called ΔE or ΔG effect, is crucial for ultrasensitive magnetic field sensors based on surface acoustic waves (SAWs). In spite of a lot of demonstrations, rare attention was paid to the frequency-dependence of ΔE or ΔG effect. In this 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 ΔG 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 a magnetostrictive layer, the more pronounced ΔG effect can be obtained, which is explained by our proposed dynamic magnetoelastic coupling model.

Highly sensitive surface acoustic wave magnetic field sensor based on the loss mechanism

“…Hu et al found through theoretical simulations that the ∆G effect was related to the device operating frequency and the magnetic field. The shear modulus increased from 45 GPa to 57 GPa at magnetic field saturation [18]. To improve the detection sensitivity and reduce the hysteresis error, Wang et al designed and fabricated SAW devices with different thin-film patterns (dot, grating, and membrane), and found that the dot-like thin film structure can increase the magnetostrictive effect by fully releasing the internal coericivity of the magnetistrictive [10], and a large current sensitivity (37.9 k A −1 ) can be achieved [19]; as an available way allowing enhancement of adhesion, a Cr thin film was employed as the transition-layer to weaken the mechanical fatigue [20].…”