Effective plasmon coupling in conical cavities generates a highly enhanced local electric field near metal surfaces for highly sensitive SERS substrates.
We demonstrated a convenient method
via applying uniaxial tensile
strains to continuously tune the high-frequency properties of flexible
magnetic films. CoFeB films were magnetron sputtered onto prestretched
polydimethylsiloxane (PDMS) membranes. They exhibit a self-assembled
periodic wrinkling surface structure because of the large mismatch
of Young’s moduli between the elastomeric PDMS substrates and
the metal layers. The wrinkling morphology and the residual tensile
stress caused by the Poisson effect can be continuously tuned by a
uniaxial stretching strain less than the growth prestrain, which consequently
results in changes in high-frequency performance. The initial permeability
and the ferromagnetic resonance frequency of flexible CoFeB thin films
can be monotonously tuned in wide ranges of about hundreds and 1 GHz,
respectively. A good repeatability over thousands of stretching-relaxing
cycles has been demonstrated without any obvious reduced high-frequency
properties. This flexible CoFeB films with excellent stretching-tunable
high-frequency performances are promising for application in flexible
and tunable microwave devices.
The giant magnetoimpedance effect of multilayered thin films under stress has great application prospects in magnetic sensing, but related studies are rarely reported. Therefore, the giant magnetoimpedance effects in multilayered thin film meanders under different stresses were thoroughly investigated. Firstly, multilayered FeNi/Cu/FeNi thin film meanders with the same thickness were manufactured on polyimide (PI) and polyester (PET) substrates by DC magnetron sputtering and MEMS technology. The characterization of meanders was analyzed by SEM, AFM, XRD, and VSM. The results show that multilayered thin film meanders on flexible substrates also have the advantages of good density, high crystallinity, and excellent soft magnetic properties. Then, we observed the giant magnetoimpedance effect under tensile and compressive stresses. The results show that the application of longitudinal compressive stress increases the transverse anisotropy and enhances the GMI effect of multilayered thin film meanders, while the application of longitudinal tensile stress yields the opposite result. The results provide novel solutions for the fabrication of more stable and flexible giant magnetoimpedance sensors, as well as for the development of stress sensors.
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