Quenching of Spin Polarization Switching in Organic Multiferroic Tunnel Junctions by Ferroelectric "Ailing-Channel" in Organic Barrier

Shiheng Liang; Zhongwei Yu; Xavier Devaux; Anthony Ferri; Weichuan Huang; Huaiwen Yang; Rachel Desfeux; Xiaoguang Li; Sylvie Migot; Debapriya Chaudhuri; Hongxin Yang; Mairbek Chshiev; Changping Yang; Bin Zhou; Jinghuai Fang; Stéphane Mangin; Yuan Lu

doi:10.1021/acsami.8b11437

Quenching of Spin Polarization Switching in Organic Multiferroic Tunnel Junctions by Ferroelectric "Ailing-Channel" in Organic Barrier

ACS Appl Mater Interfaces. 2018 Sep 12;10(36):30614-30622. doi: 10.1021/acsami.8b11437. Epub 2018 Aug 31.

Authors

Shiheng Liang^{1

2}, Zhongwei Yu^{1

3}, Xavier Devaux¹, Anthony Ferri⁴, Weichuan Huang⁵, Huaiwen Yang¹, Rachel Desfeux⁴, Xiaoguang Li⁵, Sylvie Migot¹, Debapriya Chaudhuri⁶, Hongxin Yang⁷, Mairbek Chshiev⁶, Changping Yang², Bin Zhou², Jinghuai Fang³, Stéphane Mangin¹, Yuan Lu¹

Affiliations

¹ Institut Jean Lamour, UMR 7198 , CNRS-Université de Lorraine, Campus ARTEM , 2 Allée André Guinier, BP 50840 , 54011 Nancy , France.
² Department of Physics , Hubei University , Wuhan 430062 , P. R. China.
³ School of Science , Nantong University , 9 Seyuan Road , Nantong 226019 , P. R. China.
⁴ Univ. Artois, CNRS, Centrale Lille, ENSCL, Univ. Lille, UMR 8181, Unité de Catalyse et Chimie du Solide (UCCS) , F-62300 Lens , France.
⁵ Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics , University of Science and Technology of China , Hefei 230026 , P. R. China.
⁶ Univ. Grenoble Alpes, CEA, CNRS , Grenoble INP, INAC-Spintec, 38000 Grenoble , France.
⁷ Key Laboratory of Magnetic Materials and Devices , Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences , Ningbo 315201 , China.

PMID: 30125490
DOI: 10.1021/acsami.8b11437

Abstract

The ferroelectric control of spin-polarization at ferromagnet (FM)/ferroelectric organic (FE-Org) interface by electrically switching the ferroelectric polarization of the FE-Org has been recently realized in the organic multiferroic tunnel junctions (OMFTJs) and gained intensive interests for future multifunctional organic spintronic applications. Here, we report the evidence of ferroelectric "ailing-channel" in the organic barrier, which can effectively pin the ferroelectric domain, resulting in nonswitchable spin polarization at the FM/FE-Org interface. In particular, OMFTJs based on La_0.6Sr_0.4MnO₃/P(VDF-TrFE) ( t)/Co/Au structures with different P(VDF-TrFE) thickness ( t) were fabricated. The combined advanced electron microscopy and spectroscopy studies clearly reveal that very limited Co diffusion exists in the P(VDF-TrFE) organic barrier when the Au/Co electrode is deposited around 80K. Pot-hole structures at the boundary between the P(VDF-TrFE) needle-like grains are evidenced to induce "ailing-channels" that hinder efficient ferroelectric polarization of the organic barrier and result in the quenching of the spin polarization switching at Co/P(VDF-TrFE) interface. Furthermore, the spin diffusion length in the negatively polarized P(VDF-TrFE) is measured to be about 7.2 nm at 20K. The evidence of the mechanism of ferroelectric "ailing-channels" is of essential importance to improve the performance of OMFTJ and master the key condition for an efficient ferroelectric control of the spin polarization of "spinterface".

Keywords: organic multiferroic tunnel junctions; spin polarization; spinterface; tunneling magneto-resistance.