Optimization of Pt composition with magnetic thin films for magnetic field sensor application

•AMR of Py/Pt multilayers with various Py thicknesses is determined.•Post-annealing (100–500 °C) treatment result in different composition.•Role of interfaces, crystallinity, grain and fine structure investigated in the AMR effect. Heavy metals like Pt play an important role in the field of spintronics due to their high spin-orbit coupling. Yet optimization condition for using it in proximity to magnetic materials is still challenging. In this letter, using post-annealing of permalloy (Py)/Pt multilayers, different composition structures of Pt with Py have been fabricated. Structural analysis showed that at temperatures higher than 200 °C the Pt diffuses into the crystal structure of Py while at lower temperatures Pt is in proximity to the Py layer. At annealing temperatures below 200 °C the magnetoresistance (MR) ratio and sensitivity increases and at higher annealing temperatures the MR ratio and sensitivity decreases. Magnetic hysteresis loop measurement showed that at lower annealing temperature, magnetic moment and therefore MR ratio increases. Results can be considered for optimization of heavy metal mixing with magnetic materials for magnetic field sensor enhancement.