Epitaxial Strain Enhanced Ferroelectric Polarization toward a Giant Tunneling Electroresistance
Xiaoqi Li, Jiaqi Liu, Jianqi Huang, Biaohong Huang, Lingli Li, Yizhuo Li, Wentao Hu, Wentao Hu, Changji Li, Sajjad Ali, Teng Yang, Fei Xue, Zheng Han, Yun‐Long Tang, Weijin Hu, Weijin Hu, Zhidong Zhang
Abstract
A substantial ferroelectric polarization is the key for designing high-performance ferroelectric nonvolatile memories. As a promising candidate system, the BaTiO 3 /La 0.67 Sr 0.33 MnO 3 (BTO/LSMO) ferroelectric/ferromagnetic heterostructure has attracted a lot of attention thanks to the merits of high Curie temperature, large spin polarization, and low ferroelectric coercivity. Nevertheless, the BTO/LSMO heterostructure suffers from a moderate FE polarization, primarily due to the quick film-thickness-driven strain relaxation. In response to this challenge, we propose an approach for enhancing the FE properties of BTO films by using a Sr 3 Al 2 O 6 (SAO) buffering layer to mitigate the interfacial strain relaxation. The continuously tunable strain allows us to illustrate the linear dependence of polarization on epitaxial strain with a large strain-sensitive coefficient of ∼27 μC/cm 2 per percent strain. This results in a giant polarization of ∼80 μC/cm 2 on the BTO/LSMO interface. Leveraging this large polarization, we achieved a giant tunneling electroresistance (TER) of ∼10 5 in SAO-buffered Pt/BTO/LSMO ferroelectric tunnel junctions (FTJs). Our research uncovers the fundamental interplay between strain, polarization magnitude, and device performance, such as on/off ratio, thereby advancing the potential of FTJs for next-generation information storage applications.