Bending characteristics of anisotropic magnetoresistance effect in NiFeCu thin films on ultra-smooth polyimide substrates

We investigate the surface morphology and magnetic/electrical properties of NiFeCu thin films on ultra-smooth Xenomax (a type of polyimide) substrates with a particular focus on the bending dependence of the anisotropic magnetoresistance (AMR) effect. The surface roughness of the NiFeCu/Xenomax is as low as 0.24 nm, enabling the observation of a large AMR ratio of up to 0.86% without microfabrication, which represents a clear incremental advance over previous studies using flexible substrates. The behaviour of the AMR curves under bending is consistent with the magnetization curves obtained from the magneto-optical Kerr effect measurements, which can be attributed to the inverse magnetostrictive effect. The bending experiments focusing on the composition reveal that the strain dependence of AMR varies depending on the sign of the magnetostriction constant and its magnitude relative to a threshold value. Bending-induced magnetic tuning is a powerful tool for the development of high-performance flexible magnetic sensors. • NiFeCu thin films on Xenomax with small surface roughness are successfully fabricated. • Large anisotropic magenetoresistance (AMR) ratio is observed in NiFeCu/Xenomax. • Bending-induced AMR behaviour can be categorized by magnetostriction constant of NiFeCu. • Bending-induced AMR effect can be explained by the inverse magnetostrictive effect. • Magnetic thin films on Xenomax can be a powerful tool for potential applications in magnetic sensors.