Direct visualization of magnetic‐field‐induced magnetoelectric switching in multiferroic aurivillius phase thin films

Abstract

Multiferroic materials displaying coupled ferroelectric and ferromagnetic order parameters could provide a means for data storage whereby bits could be written electrically and read magnetically, or vice versa. Thin films of Aurivillius phase Bi6Ti2.8Fe1.52Mn0.68O18, previously prepared by a chemical solution deposition (CSD) technique, are multiferroics demonstrating magnetoelectric coupling at room temperature. Here we demonstrate the growth of a similar composition, Bi6Ti2.99Fe1.46Mn0.55O18, via the liquid injection chemical vapor deposition technique. High resolution magnetic measurements reveal a considerably higher in-plane ferromagnetic signature than CSD grown films (MS = 24.25 emu/g (215 emu/cm 3 ), MR = 9.916 emu/g (81.5 emu/cm 3 ), HC = 170 Oe). A statistical analysis of the results from a thorough microstructural examination of the samples, allows us to conclude that the ferromagnetic signature can be attributed to the Aurivillius phase, with a confidence level of 99.95 %. In addition, we report the direct piezoresponse force i E-mail: lynette.keeney@tyndall.ieJournal of the American Ceramic Society DOI: 10.1111DOI: 10. /jace.14597 (2016 2 microscopy (PFM) visualization of ferroelectric switching while going through a full in-plane magnetic field cycle, where increased volumes (8.6 to 14 % compared with 4 to 7 % for the CSDgrown films) of the film engage in magnetoelectric coupling and demonstrate both irreversible and reversible magnetoelectric domain switching. IntroductionMultiferroic materials which exhibit more than one mutually-coupled ferroic (e.g. ferroelectric (FE) / ferromagnetic (FM) / ferroelastic) order parameter (OP) in a single phase, provide additional degrees of OP freedom that can be exploited in novel multistate memory and sensing devices.Magnetoelectricity (the generation of a change in magnetization by an applied electric field or vice versa), on the other hand, is a related phenomenon that will arise in any material that is both electrically and magnetically polarizable and possesses an appropriate magnetic symmetry, regardless of whether it is multiferroic or not. For example, the magnetoelectric Cr2O3 is an antiferromagnetic dielectric and is neither FE nor FM 1 . The unique advantage of single phase magnetoelectric multiferroics is that not only could they find application in high storage density, lowpower memory devices that can be electrically written and magnetically read, but also memory technologies with 4-state logic might be achieved by constructing devices that exploit the presence of both ferroelectric and ferromagnetic states 2 -representing a clear improvement over current 2-state logic devices. However, there are relatively few 3-8 materials demonstrating ferroelectric and ferromagnetic properties in a single-phase at room temperature. Due to conflicting electronic structure requirements for ferroelectricity (empty d orbitals) and ferromagnetism (partially filled d orbitals), the two properties tend to be mutually exclusive 9 . Examples of multiferroic material...

Buried In-Plane Ferroelectric Domains in Fe-Doped Single-Crystalline Aurivillius Thin Films

“…Preliminary ab initio calculations 22,23 predicted that the epitaxial strain could play an important role in determining the distribution of magnetic dopants in the Aurivillius phase. Although in the last decade Aurivillius compounds exhibiting multiferroic properties have been reported -typically in the form of polycrystalline samples 9,17,20,[24][25][26][27][28][29][30] -the accurate description of the distribution of the magnetic ions at the base of the magnetic ordering has not yet been completely addressed in such an intricate system. Additionally, a detailed experimental investigation of the atomic-scale structural distortions responsible for the ferroelectric properties of the Aurivillius phase is still missing.…”

Bi3.25La0.75Ti2.5Nb0.25(Fe0.5Co0.5)0.25O12, a single phase room temperature multiferroic

“…18 Recently, Aurivillius compounds have attracted much attention with respect to multiferroic activity. [19][20][21][22] The structure of these compounds consists of bismuthate layers of general formula (Bi2O2)n 2n+ , separated by perovskite slabs of general formula (Am-1BmO3m+1) 2n-, where m is the number of octahedral layers in the perovskite slab. In Aurivillius compounds, the spontaneous polarization (Ps) originates from the off-centre movement of the octahedral cations in one direction within the basal (a-b) plane.…”

Magnetocrystalline anisotropy in the Co/Fe codoped Aurivillius oxide with different perovskite layer number

“…However, our former researches were mostly studied in the bulk ceramics prepared by the modified Pechini's method, which was totally with random oriented grains. Even though Keeney's group has done a fabulous job to directly visualize the coexisting and coupled magnetic electric order. It is hard to get high quality epitaxial single crystals thin films and characterize them somewhat .…”