Dielectric spectroscopy and magnetometry investigation of Gd-doped strontium titanate ceramics

Structural, dielectric and magnetic properties of dense Gd-doped strontium titanate ceramics prepared by the conventional mixed oxide method are studied. Lattice parameter is found to decrease linearly in the Sr1-1.5xGd xTiO3 system, confirming the incorporation of Gd onto the Sr site of the perovskite lattice of strontium titanate up to x = 0.05. Real and imaginary parts of the dielectric permittivity of Sr1-1.5xGd xTiO3 ceramics exhibit a relaxation between 100 Hz and 1 MHz in the temperature range of 17-26 K, slightly shifting to higher temperatures with increasing Gd content. Such dielectric behaviour is attributed to the relaxation of individual dipoles formed by off-centre displacement of Gd3+ ions on Sr sites in a highly polarizable lattice of strontium titanate. Other dielectric relaxations observed in Sr1-1.5xGd xTiO3 from 125 to 300 K are attributed to the oxygen vacancy related mechanisms. No magnetic anomaly but paramagnetic behaviour is observed for Sr1-1.5xGd xTiO3 ceramics, indicating an absence of the magnetic order and hence magnetoelectric coupling.