Tuning terahertz wave absorption in diamond/NdFeB composite films via magnetic interfacial engineering

This work endows diamond with effective terahertz absorption capability through interfacial polarization and defect engineering at diamond/NdFeB heterointerfaces, achieved via a combined CVD and magnetron sputtering process. By optimizing the interfacial architecture, specifically, the insertion of a Ta interlayer and the thickness of the magnetic layer, we significantly tuned the dielectric performance and the impedance matching. This modulation stems from the mechanism of interfacial polarization, dipole relaxation and magnetoelectric synergy. When a NdFeB layer of 200 nm thickness was deposited directly onto a diamond substrate, it induced interfacial defects and generated an sp2 carbon network, which served as additional dipolar centers. Interfacial band bending and charge redistribution generate a space-charge region, which in turn establishes an intrinsic interfacial dipole layer, and strengthens interfacial polarization. Consequently, the composite film exhibits a minimum absorptivity exceeding 47% over the 170-220 GHz band with a peak value of 70%, representing a nearly fivefold enhancement over pristine diamond. This work demonstrates a new material paradigm for terahertz absorption by transforming diamond into an effective absorber through interfacial engineering with NdFeB.