Reversible magnetoelectric switching in multiferroic three-dimensional nanocup heterostructure films

Hyunji An,Bongjae Kim,Sang Yun Jeong,Sanghan Lee,Hyo Jin Hong,Ho Gyu Yoon ,Sang Woo Kim ,Jaejung Song ,Bong‐Joong Kim ,Byoung Hun Lee,Ho Jin Choi ,Tuson Park,Jongmin Lee,Kyung-Tae Ko,Sangmo Kim,Chung Wung Bark,Soon‐Gil Jung ,Soyoung Kim ,Yong‐Ryun Jo ,Tae‐Yeong Koo

doi:10.1038/s41427-019-0172-4

Abstract

Self-assembled nanocomposite films containing ferroelectric and ferromagnetic phases have attracted enormous research interest because they are the most promising candidates for practical multiferroic applications. However, obtaining a genuine magnetoelectric (ME) coupling effect is still challenging in this research area. To substantially improve the ME effect, new heterostructure designs with efficient strain control between two phases are urgently needed. Herein, a novel three-dimensional (3D) nanocup architecture of a heterostructure film is developed. To establish the unique architecture, a heavily Co, Fe-doped ferroelectric Bi3.25La0.75Ti3O12 (BLT) target was used during the growth of BLT thin films via pulsed laser deposition. Consequently, 3D nanocup-structured CoFe2O4 (CFO) particles formed inside the BLT via spontaneous nucleation and agglomeration. The 3D nanocup BLT-CFO film exhibited magnetically controlled reversible dielectric switching, which is direct evidence of strong ME coupling caused by the efficient interfacial strain coupling and low leakage of the novel nanocup architecture. The obtained results strongly suggest that the 3D nanocup heterostructure film significantly improves the ME coupling effect. In addition, we propose a new paradigm in the architecture design of self-assembled nanocomposite films for diverse multifunctional devices.

Highlights

IntroductionThe ability to synthesize selfassembled nanocomposite films of complex oxides has paved the way for creating new physical phenomena[1,2,3,4,5]
These self-assembled nanocomposite films have demonstrated a variety of fascinating physical phenomena, including enhanced flux pinning in high-temperature superconductors[6,7], strain-enhanced ferroelectricity and multiferroics[8,9], enhanced ferromagnetism[10], Correspondence: Bong-Joong Kim or Chung Wung Bark or Sanghan Lee 1School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea 2Center for Quantum Materials and Superconductivity (CQMS), Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea Full list of author information is available at the end of the article
Previous attempts to fabricate a self-assembled BiT-CFO nanocomposite film resulted in a Bi5Ti3FeO15 (BTFO) phase despite the use of a conventional BiT-CFO mixed target[24]; such a phase was obtained because of the tunable characteristics of the layered perovskite structure of BiT

Summary

Introduction

The ability to synthesize selfassembled nanocomposite films of complex oxides has paved the way for creating new physical phenomena[1,2,3,4,5]. Until now, these self-assembled nanocomposite films have demonstrated a variety of fascinating physical phenomena, including enhanced flux pinning in high-temperature superconductors[6,7], strain-enhanced ferroelectricity and multiferroics[8,9], enhanced ferromagnetism[10], magnetoresistance[11], novel electronic/ionic transport[12], and coupling of dielectric and optical effects[13]. Many researchers have attempted to overcome this problem with a variety of approaches, which include substituting magnetic impurities or cations and making

Methods

Results

Conclusion