Magnetic microstructure analysis of sputter deposited permalloy thin films on a spin-on polyimide substrate

We have performed magneto-optical measurements of sputter deposited permalloy (NiFe 81/19) thin films on a polyimide based spin-on substrate and a silicon oxide substrate. Experiments were performed by means of the magneto-optic Kerr effect in order to complement the findings concerning soft magnetic behaviour on the macroscopic scale presented previously (Rittinger et al., Impact of different polyimide-based substrates on the soft magnetic properties of NiFe thin films, SPIE Microtechnologies. International Society for Optics and Photonics, Bellingham, pp 95171R, 2015) with new insights into the magnetic domain structures of such samples. First, magnetization curves (R---H-, B---H-curves) are compared with corresponding magneto-optical hystereses. Second, by taking into consideration the results of the magnetic microstructure analysis, further aspects of the interactions between the substrate and the functional thin film are revealed in form of analogies between observations on the microscopic scale and variations of macroscopic magnetization curves of analysed samples. Furthermore, the shape and detailed spatial arrangement of domains and their boundaries are determined for the investigated samples, supplying further information on the properties and state of stress of the thin films. Doing so, we aim to provide precise and reliable anisotropic magnetoresistive (AMR) sensors on flexible polymer substrates in the future.