Modified Lossy epsilon-negative CuCr2Se4 toward single-phase metamaterials with double negative parameters via Zn doping

Abstract

Single-phase metamaterials are a group of attractive alternatives to ordered double negative metamaterials (DNMs) that exhibit negative permittivity (ε < 0) and negative permeability (μ < 0) with periodic unit cells. However, achieving double negative electromagnetic properties in a single-phase material in the radio-frequency range is challenging. This study presents the synthesis of the single-phase metamaterial, selenospinel Cu_xZn_1−xCr₂Se₄, from metallic powders through a simple solid-state reaction process. The double negative values of ε and μ were observed in the frequency range of 484–1000 MHz for Cu_0.8Zn_0.2Cr₂Se₄ (x = 0.2) and 638–1000 MHz for Cu_0.6Zn_0.4Cr₂Se₄ (x = 0.4). The negative value of ε is attributed to the plasmonic state of delocalized carriers in the metallic ferromagnetic CuCr₂Se₄ and can be described using the Drude model. The suppression of magnetic resonance induced by the eddy current was alleviated through appropriate doping of the Zn element. Based on the skin effect, a theoretical model was constructed to elucidate the magnetic resonance-dependent negative permeability. In this study, metallic ferromagnetic chalcospinels are introduced into the field of single-phase DNMs, which significantly broadens the range of metamaterials. Furthermore, this study contributes to the theoretical understanding and tuning mechanism of double negative properties.