Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
1] Department of Applied Chemistry, School of Engineering, Tohoku University 6-6-07 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579, Japan [2] Materials and Structures Laboratory, Tokyo Institute of Technology, Midori-ku, 4259 Nagatsuta, Yokohama 226-8503, Japan.
Nat Commun. 2014 Sep 18;5:4971. doi: 10.1038/ncomms5971.
Ferroelectrics have been used as memory storage devices, with an upper bound on the total possible memory levels generally dictated by the number of degenerate states allowed by the symmetry of the ferroelectric phase. Here, we introduce a new concept for storage wherein the polarization can be rotated arbitrarily, effectively decoupling it from the crystallographic symmetry of the ferroelectric phase on the mesoscale. By using a Bi5Ti3FeO15-CoFe2O4 film and via Band-Excitation Piezoresponse Force Microscopy, we show the ability to arbitrarily rotate polarization, create a spectrum of switched states, and suggest the reason for polarization rotation is an abundance of sub-50 nm nanodomains. Transmission electron microscopy-based strain mapping confirms significant local strain undulations imparted on the matrix by the CoFe2O4 inclusions, which causes significant local disorder. These experiments point to controlled tuning of polarization rotation in a standard ferroelectric, and hence the potential to greatly extend the attainable densities for ferroelectric memories.
铁电体已被用作存储设备，其总存储容量的上限通常由铁电相的对称性允许的简并态数量决定。在这里，我们引入了一种新的存储概念，其中通过使用能带激发压电力显微镜，我们展示了任意旋转极化的能力，创建了一个切换状态的光谱，并提出了极化旋转的原因是存在大量的小于 50nm 的纳米畴。基于透射电子显微镜的应变映射证实了 CoFe2O4 夹杂在基体上施加的显著局部应变起伏，这导致了显著的局部无序。这些实验表明可以在标准铁电体中控制极化旋转的调节，从而有可能大大扩展铁电存储器的可达到密度。
