Department of Materials Science and Engineering, University of Wisconsin-Madison, 53706, USA.
Philos Trans A Math Phys Eng Sci. 2012 Oct 28;370(1977):4872-89. doi: 10.1098/rsta.2012.0197.
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.
作为一种具有反铁磁、铁电和铁弹序共存的室温多铁体，BiFeO(3) 被广泛研究用于实现磁电器件，通过电场来控制磁序。此外，BiFeO(3) 是铁电存储器件的有前途的候选材料，因为它具有所有铁电材料中最大的剩余极化强度 (P(r)>100 μC cm(-2))。对于这些应用，通过电场控制极化反转起着至关重要的作用。然而，BiFeO(3) 由于菱面体对称性而具有复杂的开关行为：铁弹（71°，109°）和铁电（180°）开关。此外，极化通过多步过程切换：180° 切换通过三个连续的 71° 切换步骤发生。通过使用单晶畴 BiFeO(3) 薄膜异质结构，我们将这种多步开关与潜在器件的宏观观察到的可靠性问题（例如保持和疲劳）相关联。我们使用单晶畴 BiFeO(3) 岛克服了保持问题（即 71° 切换区域的弹性反向切换）。此外，我们通过单个 71° 切换路径抑制了 180° 切换的疲劳问题，即随切换循环损失可切换极化。我们的结果为探索在其他菱面体和低对称性材料中与铁弹序耦合的多个有序参数的可靠控制提供了框架。
