Surface morphology and magnetic anisotropy of zigzag wrinkled NiFe films grown on polydimethylsiloxane

We reported an investigation on the surface topography and the magnetic anisotropy of wrinkled Ni₈₁Fe₁₉ (NiFe) thin films grown on both uniaxially and biaxially pre-strained polydimethylsiloxane (PDMS) membranes. Because of the large difference in elastic moduli between the magnetic film layer and the elastomeric PDMS substrate, NiFe films grown on a uniaxially pre-strained PDMS show a one-dimensional (1D) wrinkled structure and a uniaxial magnetic anisotropy (UMA) along the wrinkles. In contrast, NiFe films grown on a biaxially pre-strained PDMS show a two-dimensional (2D) zigzag wrinkled surface morphology and an UMA which direction is determined by the sequence of releasing the biaxial pre-stresses. The inter-peak distance and the amplitude of the wavy morphology for both the 1D and 2D wrinkled NiFe thin films decreases and increases with improving the pre-strain, respectively. The UMA of the wrinkled NiFe films originates from a surface effect of magnetic charges created on the wavy topography when a magnetic field is applied.