RESUMEN
Due to the magnetoelastic coupling, the magnetic properties of many flexible magnetic films (such as Fe, Co, and Ni) are sensitive to mechanical stress, which deteriorates the performance of flexible magnetoelectronic devices. We show that by stacking Co and Pt alternatively to form multilayers with strong perpendicular magnetic anisotropy (PMA), both magnetic hysteresis and magnetic domain measurements reveal robust PMA against external stress. As the PMA weakens at increased Co thickness, the magnetic anisotropy is vulnerable to external stress. These results were understood based on a micromagnetic model, which suggests that the strength of magnetoelastic anisotropy with respect to initial effective magnetic anisotropy affects the stress-stability of the film. Although the stress coefficient of magnetoelastic anisotropy is enhanced at reduced Co thickness, the concomitant increase of initial effective magnetic anisotropy guarantees a robust PMA against external stress. Our results provide a route to constructing flexible magnetoelectronic devices with enhanced stress stability.
RESUMEN
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.