Abstract
We report the measurement of form and magnetic birefringence in Permalloy (Ni80Fe20) films grown on rippled Poly(Ethylene Terephthalate), PET, substrates. Prior to Permalloy deposition, Laser Induced Periodic Surface Structures (LIPSS) were generated on the polymeric substrate by a nanosecond laser beam, developing an ordered rippled nanostructure. Due to their high transparency factor, we could investigate the behavior of linear polarized light transmitting at normal incidence on Permalloy/PET sample. The results show the existence of an optical axis parallel to the ripples direction, which yields an strong form birefringence effect arising from the laser patterning. Concerning the Permalloy thin film, the study of its in-plane magnetization was carried out measuring the Voigt magnetooptical effect. The obtained data in our samples reveal the appearance of two different mechanisms to reverse the magnetization, as the external magnetic field is parallel or perpendicular to the ripples direction. Accordingly, the transmitted light shows a magnetic birefringence depending on the relative orientation between the ripple direction, i.e. the optical axis of the LIPSS, and the in-plane magnetization of the Permalloy film.
Highlights
In recent years, the use of pulsed lasers to irradiate different substrates has shown to be a powerful tool to obtain high resolution bidimensional nanostructures
The results show the existence of an optical axis parallel to the ripples direction, which yields an strong form birefringence effect arising from the laser patterning
To investigate the occurrence of form birefringence in Laser Induced Periodic Surface Structures (LIPSS) patterned onto a PET substrate, we first measured the dependence of transmitted light on the relative orientation between the ripple direction and the polarization plane of incoming beam, angle θ
Summary
The use of pulsed lasers to irradiate different substrates has shown to be a powerful tool to obtain high resolution bidimensional nanostructures. In the case of polymeric substrates, laser irradiation yields corrugated surfaces consisting in a periodic array of ripples, aligning parallel with the incident laser polarization direction [9, 10] This ripple direction breaks the initial shape symmetry of the substrate, being responsible for an expected form birefringence in these polymeric systems which has not been reported before. We have investigated the capability of that uniaxial LIPSS to provide a source of anisotropy in the surface magnetization of a capping layer In this sense, we have measured the Voigt magnetooptical effect of rippled PET substrates coated with different Permalloy thin films
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