Caracterización dieléctrica de la perovskita laminar La1.5Sr0.5CoO4

In this work, the behaviour of the real and imaginary components of the dielectric permittivity of layered perovskite La 1 5 Sr 0 . 5 CoO 4 have been studied, in the frequency range 20 Hz-1 MHz and in the temperature range 115-350 K. Polycrystalline samples were prepared by the ceramic method. The powder diffraction results showed the pattern of the desired phase together with a small quantities of La 2 O 3 impurities. A comparative study of the electrical and magnetic properties of this charge-ordered compound (T C O ∼750 K) has revealed a basically semiconductor behaviour with a complex bidimensional antiferromagnetism which can be explained on the basis of a thermally activated evolution of the spin state of the Co 3 + ions. A detailed investigation of the dielectric properties of this system has allowed us to identify two superimposed relaxation processes: the first one in the low frequency range (f<10 2 Hz), which has been associated with electronic hopping conduction and the second one in the high frequency range due to dipolar processes, which we have associated with the charge order of this system. Both of them, including the conductivity as a function of the frequency, were analyzed in terms of the "universal dielectric response". We have found good fittings to this power law with different exponents for both relaxation processes.