Experimental realization of strain-induced room-temperature ferroelectricity in SrMnO3 films via selective oxygen annealing
Hyunji An, Younggyun Choi, Yong‐Ryun Jo, Hyo Jin Hong, Jeong‐Kyu Kim, Owoong Kwon, Sangmo Kim, Myungwoo Son, Jiwoong Yang, Jun-Cheol Park, Hojoong Choi, Jongmin Lee, Jaesun Song, Moon‐Ho Ham, Sangwoo Ryu, Yunseok Kim, Chung Wung Bark, Kyung‐Tae Ko, Bong‐Joong Kim, Sanghan Lee
Abstract
Abstract Antiferromagnetic-paraelectric SrMnO 3 (SMO) has aroused interest because of the theoretical strong coupling between the ferroelectric and ferromagnetic states with increasing epitaxial strain. In strained SMO films, the <110> polarized state and polar distortions have been observed, although high leakage currents and air degradation have limited their experimental verification. We herein provide a conclusive demonstration of room-temperature ferroelectricity and a high dielectric constant ( ε r = 138.1) in tensile-strained SMO by securing samples with insulating properties and clean surfaces using selective oxygen annealing. Furthermore, a paraelectricity and low dielectric constant ( ε r = 6.7) in the strain-relaxed SMO film have been identified as properties of the bulk SMO, which directly proves that the ferroelectricity of the tensile-strained SMO film is due to strain-induced polarization. We believe that these findings not only provide a cornerstone for exploring the physical properties of multiferroic SMO but also inspire new directions for single-phase multiferroics.