Communication-A Weakly Negative Permittivity of Carbonyl Iron and La-Doped Barium Ferrite Composites at Radio Frequency

Percolative composites with negative permittivity have attracted much attention. For carbonyl iron and La-doped barium ferrite composites, the conduction mechanism changed from hopping conduction to metal-like conduction when carbonyl iron content increased. When carbonyl iron content was 80 wt%, which exceeded but approached the percolation threshold, a weak value of negative permittivity between -200 and 0 was achieved. In addition, the analysis of reactance revealed that inductance characteristic resulted in the negative permittivity. This work provides a way to design the metal composites with a weakly negative permittivity to apply in different fields.