Microstructure and dielectric relaxor properties for Ba0.5Sr0.5TiO3/La0.67Sr0.33MnO3 heterostructure

Ferroelectric and magnetoresistance heterostructure (Ba,Sr)TiO3/(La,Sr)MnO3 (BST/LSMO) heterostructure is deposited epitaxially on SrTiO3 (001) substrate by pulse laser deposition. The phase structures of the BST/LSMO heterostructure are characterized by x-ray diffraction. Cross-sectional transmission electron microscope shows a substantial interdiffusision between BST and LSMO layers. The dielectric properties and conductivity of BST/LSMO heterostructure is measured as a function of temperature, frequency, and electric field. The dielectric constant dependence on electric field, ε vs E, exhibits a strong nonlinear behavior in the temperature from 20 to 300 K, while ε(E=0) vs T relation shows a dielectric relaxor characteristic. Furthermore, the dielectric constant (E=0 kV/cm) and the dielectric tunability (E=200 kV/cm) are found to be similar temperature dependencies. Last, in the temperature regime where a semiconduction-type conduction became dominate, the activation thermal energy of BST/LSMO heterostructure is estimated to be 0.67 and 0.73 eV at 1 kHz and 1 MHz, respectively.