Microstructure and magnetic properties of NdFe/MgO(001) thin films elaborated by evaporation from Nd3Fe29 nanocrystalline powder

Rare earth (R) and transition metal (T) based films are potential magnetic materials for a variety of applications. However, their structural and magnetic behavior is sensitive to growth and processing parameters. This article presents a comprehensive investigation aiming to analyze the microstructure and magnetic properties of NdFe/MgO(001) films. These films were fabricated by evaporating nanocrystalline Nd3Fe29 powder at different thicknesses (t) and subjected to various heat treatments (Ta). The main objective of this research is to gain a detailed understanding of how the structural and magnetic behavior evolves based on these parameters, which had not been achieved previously. X-ray diffraction analysis was employed to determine the crystalline structure of NdFe/MgO(001) films and to track the grain size evolution with film thickness. Scanning electron microscopy (SEM) and magnetic force microscopy (MFM) images were used to directly visualize magnetic domains and the arrangement of magnetic grains at different thicknesses. Ferromagnetic resonance (FMR) measurements revealed significant variations in resonance fields and easy axes depending on film thickness and heat treatments. The study also examined how magnetic properties such as saturation magnetization (Ms) and coercivity (Hc) are closely related to grain size, magnetic domain organization, and heat treatments. Our research produced remarkable results, especially concerning a 250 nm thick NdFe/MgO(001) film annealed at 873 K, which exhibited outstanding properties. These properties include a robust coercivity of 5230 Oe, a substantial remanent magnetization of 211 emu/cm3, a magnetic anisotropy field of 10,325 Oe, a saturation magnetization (Ms) of 396 emu/cm3, and a Curie temperature of approximately 388 K. It’s noteworthy that this film possesses an easy magnetization axis parallel to the film plane (HFMR(∥) = 9125 Oe > HFMR(⊥) = 5897 Oe). Although the study provides valuable insights for the design and optimization of magnetic materials for various technological applications in the field of magnetism, its limitation should be acknowledged. The research did not deeply explore the correlations between the different studied properties, leaving a gap in our overall understanding of these characteristics. Therefore, future work will focus on conducting simulations and theoretical modeling to address this research gap.