This study demonstrates broadband nonreciprocal thermal emissivity and absorptivity using gradient epsilon-near-zero (ENZ) InAs layers with subwavelength thicknesses (50 nm and 150 nm) under an external magnetic field. The spectral range (12.5–16 μm) overlaps with the infrared transparency window and is observed at moderate magnetic fields (1 T). The nonreciprocal effect is achieved by measuring the emissivity and absorptivity of the gradient ENZ structure, showing opposite tuning of emissivity and absorptivity for the same directional channels. The results show that the nonreciprocal emission and absorption strongly depend on the sample's subwavelength thickness and carrier concentration ordering. The ENZ resonance wavelengths are determined by the electron free carrier concentration of each layer. The structure consists of six layers with increasing carrier concentrations (1.5 to 4.5 × 10¹⁸ cm⁻³) from bottom to top. The individual resonances of the layers are spectrally closely spaced to create a broadband emissivity and absorptivity feature in the 12.5–17 μm region. The angle at which the emitted light couples out of the structure is determined by the thicknesses of the layers. The study shows that the nonreciprocal effect is broadband and occurs over a wide range of angles. The results demonstrate that the nonreciprocal emissivity and absorptivity can be tuned by the magnetic field, with the effect being strongest at angles around 60°. The study also shows that the nonreciprocal effect is dependent on the sample's thickness and carrier concentration ordering, with thicker samples showing stronger tuning. The results suggest that the nonreciprocal effect can be used for thermodynamic limits in photonic energy conversion and radiative cooling. The study also discusses the potential applications of the nonreciprocal effect in other materials and the need for further development of designs that rely on drift effects and spatiotemporal modulation for broadband nonreciprocal absorptivity and emissivity demonstrations at practical wavelengths.This study demonstrates broadband nonreciprocal thermal emissivity and absorptivity using gradient epsilon-near-zero (ENZ) InAs layers with subwavelength thicknesses (50 nm and 150 nm) under an external magnetic field. The spectral range (12.5–16 μm) overlaps with the infrared transparency window and is observed at moderate magnetic fields (1 T). The nonreciprocal effect is achieved by measuring the emissivity and absorptivity of the gradient ENZ structure, showing opposite tuning of emissivity and absorptivity for the same directional channels. The results show that the nonreciprocal emission and absorption strongly depend on the sample's subwavelength thickness and carrier concentration ordering. The ENZ resonance wavelengths are determined by the electron free carrier concentration of each layer. The structure consists of six layers with increasing carrier concentrations (1.5 to 4.5 × 10¹⁸ cm⁻³) from bottom to top. The individual resonances of the layers are spectrally closely spaced to create a broadband emissivity and absorptivity feature in the 12.5–17 μm region. The angle at which the emitted light couples out of the structure is determined by the thicknesses of the layers. The study shows that the nonreciprocal effect is broadband and occurs over a wide range of angles. The results demonstrate that the nonreciprocal emissivity and absorptivity can be tuned by the magnetic field, with the effect being strongest at angles around 60°. The study also shows that the nonreciprocal effect is dependent on the sample's thickness and carrier concentration ordering, with thicker samples showing stronger tuning. The results suggest that the nonreciprocal effect can be used for thermodynamic limits in photonic energy conversion and radiative cooling. The study also discusses the potential applications of the nonreciprocal effect in other materials and the need for further development of designs that rely on drift effects and spatiotemporal modulation for broadband nonreciprocal absorptivity and emissivity demonstrations at practical wavelengths.