Defect‐Enhanced Polarization Switching in the Improper Ferroelectric LuFeO₃

Abstract

Results of switching behavior of the improper ferroelectric LuFeO3 are presented. Using a model set of films prepared under controlled chemical and growth‐rate conditions, it is shown that defects can reduce the quasi‐static switching voltage by up to 40% in qualitative agreement with first‐principles calculations. Switching studies show that the coercive field has a stronger frequency dispersion for the improper ferroelectrics compared to a proper ferroelectric such as PbTiO3. It is concluded that the primary structural order parameter controls the switching dynamics of such improper ferroelectrics.

Analysis of the magnetic and magnetocaloric properties of ALaFeMnO6 (A = Sr, Ba, and Ca) double perovskites

“…On the other hand, the broad reflections unveiled for the doped LMFO indicate smaller size crystallites. Rietveld refinements of the XRD data (not shown here) reveal that LMFO, BLMFO and CLMFO adopt an orthorhombic (Pnma) structure while a rhombohedral structure (R-3c) is obtained for the SLMFO compound in partial accordance with previous reports 19,21 . Shaheen et al reported an orthorhombic perovskite structure, but with space group Pbnm for BLMFO and CLMFO, while a rhombohedral structure (space group R-3c) for SLMFO was observed 19 .…”

“…shows the zero-field cooled (ZFC) magnetization as a function of temperature measured under an applied magnetic field of 0.2 T for undoped and doped LMFO. The measured magnetization curve of LMFO is similar to that reported by Barrozo et al21 . A broad transition centered around 80 K is observed for LMFO, presumably from a ferromagnetic (FM) to a paramagnetic (PM) phase.…”

“…However, the maximum entropy changes for BLMFO in Figure 6(b) and SLMFO in Figure 6(c) are about 0.15 to 0.42 J/K kg and 0.15 to 0.48 J/K kg, respectively. The MCE in terms of the maximum magnetic entropy change for these materials is much lower than that presented by gadolinium (Gd) metal with 9.8 J/kg K 1 and oxides such as La2NiMnO6 (LNMO) and La2CoMnO6 (LCMO) single crystals with MCE value of 2 and 3.5 J/K kg, respectively, for magnetic field variation from 0 to 5 T 1,21 . However, the very large temperature range of significant ΔSM with almost flat temperature-independent values could be appealing if further increased.…”

Absence of critical thickness in improper ferroelectric hexagonal-YbFeO3 thin films

“…3(b) and fit with the two aforementioned models. The fitting with the power law gave the value of the exponent, β = 0.28, which is higher than that reported in h-ErMnO3 bulk single crystals (β ≈ 0.1) 9 but lower than the value reported in h-LuFeO3 thin films (β ≈ 0.66) 10 . On the other hand, from the Du-Chen model, a cutoff frequency of ~ 365 kHz was obtained which is lower than that in PZT thin films (1~2 MHz) 31 , but similar to that in barium strontium titanate (BST) thin films 32 .…”

“…However, although the electrostatic effects may not quench the primary structural distortion, their effects on the spontaneous polarization have not been properly addressed. In addition, an understanding of the polarization switching mechanism is of vital importance for any technological applications 9,10 . The difficulty in growth and electrical characterization of ultrathin films on structurally mismatched substrates, coupled with the intertwined interfacial and electrostatic effects, might have contributed to the lack of systematic studies in this regard.…”