Thickness dependent functional properties of PbZr0.52Ti0.48O3/La0.67Sr0.33MnO3 heterostructures

Abstract

The ultra thin ferroelectric PbZr0.52Ti0.48O3 (PZT) films with various thicknesses ranging from 100 (P100) to 10 (P10) nm were grown on La0.67Sr0.33MnO3/(LaAlO3)0.3(Sr2AlTaO6)0.7 (LSMO/LSAT) (001) substrates deposited by pulsed laser deposition technique. The x-ray diffraction patterns of the heterostructures show only (00l) (l = 1 and/or 2) reflections corresponding to the LSAT substrate, PZT, and LSMO layers. The atomic force microscopy studies show that the root mean square surface roughnesses of P100 and P10 films are 2.39 and 0.99 nm, respectively. An increase of both real (ε′) and imaginary (ε″) permittivities was observed when thickness of PZT increases from 10 nm to 100 nm. Temperature dependent ε′ presents an anomaly, related to ferromagnetic-metal to paramagnetic-insulator transition of the LSMO, in the range of 350–500 K. The dielectric anomalies and magnetic phase transition temperature shifted to the lower temperature values with decrease in the PZT films thicknesses. The values of the remanent polarization (Pr) and coercive field (Ec) of the heterostructures were in the range of 24–42 μC/cm2–170–1300 kV/cm. An appreciable increase of saturated magnetization (Ms) was observed with increase of PZT layer thickness. The average Ms values of PZT/LSMO heterostructure were 170, 150, 100, and 45 emu/cm3 for 100, 50, 25, and 10 nm at 300 K, respectively. Enhancement in magnetization with increase in PZT thickness may be due to the interface effect between PZT/LSMO layers.