Interstitial Nitrogen Tuning of Magnetocrystalline Anisotropy and High-Frequency Electromagnetic Properties in Nd-Based 3:29-Type Intermetallics

The proliferation of 5G/6G communication and millimeter-wave devices has intensified electromagnetic interference, driving demand for thin, broadband microwave absorbers. We report the structure, intrinsic magnetism, and high-frequency electromagnetic response of easy-plane Nd 2.7 Zr 0.3 Fe 28 Ti and its interstitial nitride. Nitrogenation significantly elevates T c and M s via the magneto-volume effect (MVE), while the chemical bonding effect (CBE) modulates the crystal field around Nd and markedly enhances the in-plane anisotropy field. The concurrent increase in both anisotropy fields modestly lowers initial permeability, yet the elevated M s and the concurrent enhancement of both anisotropy fields dominate this trade-off, ultimately raising the natural resonance frequency and extending the operating frequency. Notably, nitrogenation lowers the permittivity through polarized Fe–N and Nd–N bonding, a change intrinsically favorable for impedance matching, offering a route to enhance absorption capability through compositional optimization. This work establishes how the interstitial N effect governs the magnetocrystalline anisotropy and high-frequency electromagnetic response of rare-earth iron intermetallics containing localized 4 f electrons, providing a mechanism-driven guideline for designing next-generation soft magnetic absorbers.