One-port magnetic surface acoustic wave (MSAW) resonators are fabricated by stacking multilayered (FeCoSiB/SiO2) n films directly on top of interdigital electrodes. It is shown that the magneto-acoustic response of the MSAW resonators critically depends the hysteresis of ΔE effect. For the magnetic multilayer without induced magnetic anisotropy, the resonance frequency (f R) exhibits a butterfly-like dependence on the external field, therefore, enabling bipolar detection of magnetic field smaller than its coercive field. However, for the magnetic multilayers with induced magnetic anisotropy, butterfly-like or loop-like f R–H curves are measured along the interdigtial electrode fingers or the SAW propagation direction, which can be attributed to the competition between the magnetic field-induced anisotropy and the stress-induced or shape anisotropy.

A low Gilbert damping factor is crucial for emerging magneto-acoustic devices. In current work, angle-dependent and temperature-dependent Gilbert damping of magnetostrictive FeCoSiB thin films have been investigated using electron spin resonance (ESR) and vector network analyzer ferromagnetic resonance (VNA-FMR) techniques, respectively. A very low Gilbert damping factor ∼0.0038 was measured with in-plane magnetic fields at room temperature. Temperature-dependent VNA-FMR results between 10 K and 300 K exhibit a conductivity-like damping feature, which can be attributed to the spin-orbital coupling dominantly controlled by the intraband scattering. Our results clearly indicate that highly magnetostrictive or piezomagnetic film does not necessarily have a high intrinsic damping factor.

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.

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