HoFeO 3 with Thermo-Softened phonons for 3D-printed terahertz metamaterials

HoFeO 3 rare earth ferrite exhibits distinctive crystallographic properties; however, its regulatory mechanisms and methods within the terahertz band remain complex. This study employed variable-temperature Raman spectroscopy to explore atomic interactions within the crystal structures of HoFeO 3 across various modes, spanning temperatures from 20 to 300 K. The fabrication of HoFeO 3 metamaterials was achieved using 3D direct ink writing additive manufacturing technology, accompanied by the design of a three-coordinate spatial intelligent control structure to manipulate terahertz electromagnetic waves. Variable-temperature Raman spectroscopy revealed twelve active peaks, which included the stretching vibrations of Ho and O, the torsion of FeO 6 , and the stretching vibrations of Fe-O. Notably, these phonons exhibited softening phenomena with increasing temperature. A low transmittance (transmittance <0.1) of terahertz waves at 0.82 THz was attained through the use of 3D-printed double-layer 90° metamaterials. Furthermore, when the double-layer 45° metamaterials were rotated in the E-H plane around the propagation direction as the central axis, the terahertz waves demonstrated a rotational symmetry transmission law at 0.5 THz. This research offers effective materials and construction methods for metamaterials aimed at regulating terahertz electromagnetic waves.