Metallic Ferromagnet of La_0.5Sr_0.5MnO₃ with Negative Permittivity and Permeability

Since the electromagnetic metamaterials are artificial materials with subwavelength-scale periodic architectures, they can manipulate electromagnetic waves by exhibiting unusual properties of characteristic negative permittivity ε and permeability μ. However, their fabrication toward reducing the anisotropy for the realization of practical metamaterials is still a challenge. A homogeneous La_0.5Sr_0.5MnO₃ with negative properties synthesized by a facile method consisting of the sol–gel method and pressure-less sintering is proposed in this paper. By appropriately tuning e_g electrons concentration, lattice symmetry, and magnetic resonance, the La_0.5Sr_0.5MnO₃ can simultaneously achieve negative ε and μ at the frequency range of 575–650 MHz. Experimental results and theoretical simulation suggest that negative ε is attributed to the plasma oscillation of e_g electrons and high lattice symmetry, whereas the magnetic resonance causes the negative μ. The enhancement is due to the reduction of the eddy current and the effective magnetic anisotropy. An important step toward the development of natural compound metamaterials is represented in this paper.