Ferroelectric Self‐Poling, Switching, and Monoclinic Domain Configuration in BiFeO₃ Thin Films

Abstract

Self‐poling of ferroelectric films, i.e., a preferred, uniform direction of the ferroelectric polarization in as‐grown samples is often observed yet poorly understood despite its importance for device applications. The multiferroic perovskite BiFeO3, which crystallizes in two distinct structural polymorphs depending on applied epitaxial strain, is well known to exhibit self‐poling. This study investigates the effect of self‐poling on the monoclinic domain configuration and the switching properties of the two polymorphs of BiFeO3 (R′ and T′) in thin films grown on LaAlO3 substrates with slightly different La0.3Sr0.7MnO3 buffer layers. This study shows that the polarization state formed during the growth acts as “imprint” on the polarization and that switching the polarization away from this self‐poled direction can only be done at the expense of the sample's monoclinic domain configuration. The observed reduction of the monoclinic domain size is largely reversible; hence, the domain size is restored when the polarization is switched back to its original orientation. This is a direct consequence of the growth taking place in the polar phase (below Tc). Switching the polarization away from the preferred configuration, in which defects and domain patterns synergistically minimize the system's energy, leads to a domain state with smaller (and more highly strained and distorted) monoclinic domains.

Photoassisted Electric Field Modulation of Multiple Nonvolatile Resistance States in Highly Strained Epitaxial BiFeO3 Heterostructures

“…Thus, a Schottky barrier can be formed at the Pt/BFO interface, while the BFO/LSMO interface is nearly flat band . On the other hand, naturally formed oxygen vacancies usually accumulate at the Pt/BFO interface, which is consistent with the downward self‐poling in highly strained BFO . As donors, the oxygen vacancy (V O + ) can release electrons to the conduction band ( E C ) and becomes positively charged V O + , which are stable under relatively small electric fields and can be treated as the fixed electron traps .…”

“…[35] Thus, a Schottky barrier can be formed at the Pt/BFO interface, while the BFO/LSMO interface is nearly flat band. [37] As donors, the oxygen vacancy (V O + ) can release electrons to the conduction band (E C ) and becomes positively charged V O + , which are stable under relatively small electric fields and can be treated as the fixed electron traps. [37] As donors, the oxygen vacancy (V O + ) can release electrons to the conduction band (E C ) and becomes positively charged V O + , which are stable under relatively small electric fields and can be treated as the fixed electron traps.…”

Renovation of Interest in the Magnetoelectric Effect in Nanoferroics

“…Bulk BiFeO 3 is antiferrodistortive at temperatures below 1200 K. This is a ferroelectric with a high spontaneous polarization below 1100 K and an antiferromagnet below the Neél temperature N ≈ 650 K [90,91]. Well-pronounced multiferroic properties were observed in BiFeO 3 thin films and heterostructures [30,[92][93][94][95]. There are a lot of experimental and theoretical studies concerning the physical properties of bulk BiFeO 3 and BiFeO 3 thin films [68,[77][78][79][96][97][98][99][100][101][102].…”

Size effects of ferroelectric and magnetoelectric properties of semi-ellipsoidal bismuth ferrite nanoparticles

“…Bulk BiFeO 3 exhibits antiferrodistortive (AFD) order at temperatures below 1200K; it is ferroelectric (FE) with a large spontaneous polarization below 1100 K and is antiferromagnetic (AFM) below Neel temperature T N ≈ 650 K [23,24]. The pronounced multiferroic properties maintain in BiFeO 3 thin films and heterostructures [25,26,27,28,29]. Despite extensive experimental and theoretical studies of the physical properties of bulk BiFeO 3 and its thin films [21 -23, 30, 31, 32, 33, 34, 35, 36, 37], many important issues concerning the emergence and theoretical background of multiferroic polar, magnetic and various electrophysical properties of BiFeO 3 nanoparticles remain almost unexplored [38,39].…”