Abstract

ALVAREZ, G. et al. Mediciones del perfil de absorción de potencia a microondas en materiales ferroeléctricos y magnetoferroeléctricos. Superf. vacío [online]. 2005, vol.18, n.1, pp.11-15. ISSN 1665-3521.

In this work, we report the profile of non-resonant power absorption of microwaves as a function of temperature; Experimentally named MAMMAS (Magnetically Modulated Microwave Absorption Spectroscopy). The working frequencies is 8.8-9.8 GHz (X-band) on powder samples of ferroelectric BaTiO3 (BT) and PbTiO3 (PT), and magnetoferroelectric YMnO3 (YM) and Pb(Fe1/2Nb1/2)O3 (PFN).

MAMMAS profile on ceramic samples BT and PT is due to processes of microwaves absorption associated with electric dipoles. MAMMAS profile for magnetoferroelectrics YM and PFN detect the para-antiferromagnetic transition, and only for the PFN we detect the ferro-paraelectric transition. In the MAMMAS profile it is possible to distinguish processes of absorption associated to electric dipoles or magnetic dipoles. Each one of them is predominant at different regions of temperature. At low temperatures and/or near the magnetic transition, the absorption of paramagnetic dipoles is dominant. At high temperatures the electric dipoles, with considerable thermal excitation, dominates the microwaves absorption.

Keywords : Ceramics; Electron paramagnetic resonance; Ferroelectrics; Magnetoferroelectrics; Phase Transitions.