X-Ray, Dielectric, and Ferroelectric Properties of La0.67Sr0.33MnO3/ Pb(Zr0.53Ti0.47)0.60(Fe0.5Ta0.5)0.40O3 Artificial Multilayers and Superlattices structures

Superlattice (SLs) is an artificial periodic structure consisting of alternate layers of two different material.  Multiferroic SLs exhibit superior properties like low loss, high dielectric constant, very good ferroelectric and magnetic properties which make them attractive candidates for thin film devices applications. Multilayers (MLs) and SLs of the colossal magnetoresistive La_0.67Sr_0.33MnO₃  (LSMO)  and low loss multiferroic Pb(Zr_0.53Ti_0.47)_0.60(Fe_0.5Ta_0.5)_0.40O₃ (PZTFT) materials have been grown by pulsed laser deposition on (100) (LaAlO₃)_0.3(Sr₂AlTaO₆)_0.7 (LSAT) substrate with  LSMO or LaNiO₃ as bottom electrode. Depositions were performed at 600 ^oC in 150 mTorr oxygen pressure with an energy density of ~3 J/cm², and a laser repetition rate of 5 Hz. X-ray diffraction revealed well oriented (00l) perovskite structure in all structures, in case of MLs two peaks correspond for LSMO and PZTFT were observed, while in SLs the so-called satellite peaks typical of modulated structures were present. The computed modulation period (Λ) by Bragg’s condition revealed that the SLs structure was observed below of Λ ~ 20 nm. The atomic Force Microscopy studies showed a systematic decrease in grain size with increase in number of layers in PZTFT/LSMO structures. All thin film structures were found to be densely packed, smooth and free of cracks.  Piezo force microscopy showed that most of the ferroelectric domains are switching under ± 9 V external bias field in both MLs and SLs films. PZTFT/LSMO bilayer strcuture showed a dielectric constant of ~835 at 1kHz, while the ferroelectric loop showed saturation and remanent polarization of ~ 34 μC/cm² and 6 μC/cm² respectively, with a coercive field of 60 kV/cm. The saturation magnetization of LSMO/PZTFT structure grown on LSMO/LSAT was found to be ~45 emu/cm³.  A systematic study of the effect of modulation period on dielectric, ferroelectric and magetic properties of the MLs and SLs structures will be discussed.