Surface morphology and exchange bias of wrinkled NiFe/IrMn bilayers grown on polydimethylsiloxane

We reported an investigation on the surface morphology and magnetic properties of flexible NiFe/IrMn exchange biased bilayers fabricated on pre-strained polydimethylsiloxane (PDMS) substrates. Due to the large difference in elastic moduli between the magnetic films and the elastomeric PDMS membranes, the flexible NiFe/IrMn films reveal a one-dimensional wrinkled topography with the wavelength decreasing and the amplitude increasing with the growth pre-strain. Two kinds of magnetic anisotropy configurations with the unidirectional exchange-bias anisotropy parallel or perpendicular to the uniaxial magnetic anisotropy are obtained by controlling the relative orientation between the pinning direction and the wrinkle, which gives rise to the distinct angular dependence of exchange-biased field and coercivity. The magnetic behaviors of the wrinkled NiFe/IrMn bilayers can be well interpreted by numerical calculations based on the Stoner-Wohlfarth model with considering the anisotropy configurations.