Magnetic Field‐Induced Ferroelectric Switching in Multiferroic Aurivillius Phase Thin Films at Room Temperature

Abstract

Single-phase multiferroic materials are of considerable interest for future memory and sensing applications. Thin films of Aurivillius phase Bi7Ti3Fe3O21 and Bi6Ti2.8Fe1.52Mn0.68O18 (possessing six and five perovskite units per half-cell, respectively) have been prepared by chemical solution deposition on c-plane sapphire. Superconducting quantum interference device magnetometry reveal Bi7Ti3Fe3O21 to be antiferromagnetic (TN = 190 K) and weakly ferromagnetic below 35 K, however, Bi6Ti2.8Fe1.52Mn0.68O18 gives a distinct room-temperature in-plane ferromagnetic signature (Ms = 0.74 emu/g, μ0Hc =7 mT). Microstructural analysis, coupled with the use of a statistical analysis of the data, allows us to conclude that ferromagnetism does not originate from second phase inclusions, with a confidence level of 99.5%. Piezoresponse force microscopy (PFM) demonstrates room-temperature ferroelectricity in both films, whereas PFM observations on Bi6Ti2.8Fe1.52Mn0.68O18 show Aurivillius grains undergo ferroelectric domain polarization switching induced by an applied magnetic field. Here, we show for the first time that Bi6Ti2.8Fe1.52Mn0.68O18 thin films are both ferroelectric and ferromagnetic and, demonstrate magnetic field-induced switching of ferroelectric polarization in individual Aurivillius phase grains at room temperature

A study of the temperature dependence of the local ferroelectric properties of c-axis oriented Bi6Ti3Fe2O18 Aurivillius phase thin films: Illustrating the potential of a novel lead-free perovskite material for high density memory applications

“…3,14 To date, an extensively studied and scientifically interesting family of bismuth-based piezoelectrics is the bismuth layer-structured ferroelectric (BLSF) family in the Aurivillius phase. [15][16][17][18] Aurivillius phase materials are naturally 2-D nanostructured, consisting of (Bi 2 O 2 ) 2+ blocks interleaved with alternating nABO 3 perovskite units (where n ranges from 2-9), described by the general formula Bi 2 O 2 (A n−1 B n O 3n+1 ), where A represents differing cations with valence states ranging from +1 to +3 such as monovalent Na + , K + , divalent Ca 2+ , Mg 2+ , Sr 2+ , Pb 2+ , Ba 2+ and trivalent Zr 3+ , Yt 3+ etc. B represents cations with valence states ranging from +3 to +5 such as Fe, Mn, Ti, Nb etc.…”

“…In the perovskite unit cell A-site cations are coordinated to 12 oxygen ions and lie at the corner of the cell whereas B-site cations are located at the centre of the cell and coordinate to 6 oxygen ions. 15,17 The diversity of intrinsic structural tuning, variation in the number of perovskite blocks (n) and the flexibility to accommodate wide varieties of A and B-site cations within the perovskite units (in consideration of the structural tolerance factor (T f )) allow for tailoring of properties, such as the multiferrioc properties, 17 the reduction of leakage currents and polarization switching fatigue. 17,18 For instance, SrBi 2 Ta 2 O 9 (n = 2) and Bi 3.25 La 0.75 Ti 3 O 12 (n = 3) have been commercially developed for use in Fe-RAMS due to their reduced switching fatigue and high temperature stabilities as compared to lead ziroconate titanate (PZT) based materials.…”

“…15,17 The diversity of intrinsic structural tuning, variation in the number of perovskite blocks (n) and the flexibility to accommodate wide varieties of A and B-site cations within the perovskite units (in consideration of the structural tolerance factor (T f )) allow for tailoring of properties, such as the multiferrioc properties, 17 the reduction of leakage currents and polarization switching fatigue. 17,18 For instance, SrBi 2 Ta 2 O 9 (n = 2) and Bi 3.25 La 0.75 Ti 3 O 12 (n = 3) have been commercially developed for use in Fe-RAMS due to their reduced switching fatigue and high temperature stabilities as compared to lead ziroconate titanate (PZT) based materials. [19][20][21] It is well-know that bismuth layer structured Arivilius phase thin films (BLSF) with oddnumbers of perovskite units show spontaneous polarization (P s ) along the in-plane a-axis and minor polarization along the out-of-plane c-axis, while even n-numbered films demonstrate response along the out-of-plane a-axis only.…”

Understanding the Effect of Doping and Epitaxial Strain on the Ferroelectric Polarization of Layered Perovskite Thin Films

“…First-principles calculations based on density functional theory have become of high relevance in exploring and predicting novel multiferroic materials. Likewise, the experimental validation of the magnetoelectric phenomena both at the atomic and macroscopic scales is crucial to improve our insight into the microscopic mechanisms underlying the predicted phenomena.Here, in this context, we study the effect of doping and epitaxial strain on the structure and the ferroelectric properties of the promising Aurivillius-phase compounds [1]. In particular, we investigate the potential multiferroic behavior of Bi 5 FeTi 3 O 15 as predicted by ab-initio calculations [2,3].…”

“…Here, in this context, we study the effect of doping and epitaxial strain on the structure and the ferroelectric properties of the promising Aurivillius-phase compounds [1]. In particular, we investigate the potential multiferroic behavior of Bi 5 FeTi 3 O 15 as predicted by ab-initio calculations [2,3].…”