Coercivity modulation of FeCoCrMoTi films by artificial magnetic phase defects engineering based on multilayer structure

Abstract

FeCoCr-based films have been considered as promising candidates for next-generation magnetic code disk materials used in high-accuracy magnetic rotary encoders. However, realizing high coercivity with sufficient remanent magnetization in FeCoCr-based films with in-plane anisotropy to ensure suitable disturbance-rejection performance and detectability of magnetic pole pairs is a critical issue, which hinders their practical applications. In this study, we demonstrated an in-plane anisotropic [Ta(20 nm)/FeCoCrMoTi(100 nm)]2/Ta(10 nm) multilayer film (M20 sample) with a high coercivity of 945 Oe and a sufficient remanent magnetization of 2890 Oe, which is 92.1% and 63.1% higher than FeCoCrMoTi(200 nm)/Ta(10 nm) film (SL sample), respectively. Detailed microstructure characterization using atomic resolution scanning transmission electron microscopy (STEM) indicates that the high coercivity originates from the domain-wall pinning effect induced by three factors including grain refinement and heterogeneous phases generation and composition fluctuation of modulated phases. X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS) analyses reveal that the high remanent magnetization is ascribed to the higher relative content of Fe2Ta phases with strong ferromagnetism than that of Co2Ta phases with weak ferromagnetism.