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

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journal contribution
posted on 2018-08-20, 00:00 authored by 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
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 La0.6Sr0.4MnO3/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”.