First-principles calculations of permalloy thin film on SrTiO₃ substrate

Abstract The soft-magnetic permalloy is an iron-nickel alloy with high magnetic permeability and low coercivity, widely used in both high-frequency and low-frequency magnetic devices. This study investigates the property of permalloy thin films on SrTiO 3 substrates using first-principles calculations, to simulate the heterojunction of permalloy and SrTiO 3 , and to compute the band structure and state density. The results show that on the permalloy–SrTiO 3 interface, Fe atoms exhibit slight displacements, leading to in-plane contraction and out-of-plane expansion of the film. Additionally, the lattice mismatch induced by substrate stress is 2.0%, which is within the acceptable range. Analysis of the band structure and state density reveals that substrate stress significantly affects the magnetic properties of the permalloy thin film. It increases the state density near the Fermi level, and notably changes the magnetic moment. Further analysis indicates that the 3d orbitals of iron and nickel atoms contribute most to the magnetic moments, while the peak values of 3d-state density for iron and nickel atoms remain largely unchanged before and after stress. However, the spin density undergoes significant changes. These simulation results provide theoretical data support and reference for the application of permalloy thin films in high-performance magnetic devices.