The evolution of coil-less inductive behaviour in La-doped Sr 2 MnO 4

The powder and ceramics of La-substituted layered oxides La x Sr 2− x Mn 1− x O 4 ( x = 0.3, 0.5, 0.7) were synthesised using the solid-state reaction technique. All synthesised compositions have tetragonal structures with space groups I4/mm that are identical to Sr 2 MnO 4 , as shown by the Rietveld refinement. XPS spectroscopy demonstrated that Mn exists in the mixed-valence forms Mn 3+ & Mn 4+ . Studies of the relationship between AC conductivity and permittivity in response to temperature (30–300°C) and frequency (1 kHz–2 MHz) have demonstrated the existence of negative permittivity over the whole test range. The observed negative permittivity is a result of free carriers oscillating plasmonically between 1 kHz and 2 MHz as a consequence of thermal excitation processes. The modelling of impedance data using various combinations of resistors and inductors exhibited the coil-less inductive characteristics of the samples. The inductive nature of samples indicates the possibility of designing synthesised compositions as coil-less inductors.