Reliable polarization switching of BiFeO 3

Abstract

As a room temperature multi-ferroic with coexisting anti-ferromagnetic, ferroelectric and ferroelastic orders, BiFeO 3 has been extensively studied to realize magnetoelectric devices that enable manipulation of magnetic ordering by an electric field. Moreover, BiFeO 3 is a promising candidate for ferroelectric memory devices because it has the largest remanent polarization ( P r >100 μC cm −2 ) of all ferroelectric materials. For these applications, controlling polarization switching by an electric field plays a crucial role. However, BiFeO 3 has a complex switching behaviour owing to the rhombohedral symmetry: ferroelastic (71 ° , 109 ° ) and ferroelectric (180 ° ) switching. Furthermore, the polarization is switched through a multi-step process: 180 ° switching occurs through three sequential 71 ° switching steps. By using monodomain BiFeO 3 thin-film heterostructures, we correlated such multi-step switching to the macroscopically observed reliability issues of potential devices such as retention and fatigue. We overcame the retention problem (i.e. elastic back-switching of the 71 ° switched area) using monodomain BiFeO 3 islands. Furthermore, we suppressed the fatigue problem of 180 ° switching, i.e. loss of switchable polarization with switching cycles, using a single 71 ° switching path. Our results provide a framework for exploring a route to reliably control multiple-order parameters coupled to ferroelastic order in other rhombohedral and lower-symmetry materials.