A strain-relief structure by combining the strain-engineered periodic wrinkles and the parallel ribbons was employed to fabricate flexible dual spin valves onto PDMS substrates in a direct sputtering method. The strain-relief structure can accommodate the biaxial strain accompanying with stretching operation (the uniaxial applied tensile strain and the induced transverse compressive strain due to the Poisson effect), thus significantly reducing the influence of the residual strain on the giant magnetoresistance (GMR) performance. The fabricated GMR dual spin-valve sensor exhibits the nearly unchanged MR ratio of 9.9%, magnetic field sensitivity up to 0.69%/Oe, and zero-field resistance in a wide range of stretching strain, making it promising for applications on a conformal shape or a movement part.
Flexible magnetic devices are one of the indispensable flexible devices. However, the deformation of the magnetic devices will change the magnetic anisotropy of magnetic materials due to magnetoelastic anisotropy, which will decrease the performance of the devices. Therefore, it is essential to determine the stress-coefficient of magnetoelastic anisotropy in magnetic materials. Here, the magnetic anisotropy constants of an amorphous CoFeB film on a flexible polyvinylidene fluoride (PVDF) substrate in different stress states were quantitatively investigated by anisotropic magnetoresistance (AMR). The enhanced magnetic anisotropy of the CoFeB film at reduced temperature is due to magnetoelastic anisotropy induced by anisotropic thermal expansion of the PVDF substrate. Through fitting the AMR curves under variant fields in different stress states, the stress-coefficient of magnetoelastic anisotropy in the amorphous CoFeB film is obtained to be 170.7 × 103 erg cm−3 GPa−1.
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