第118回先端計測オープンセミナー

2017年12月12日 (火) 10:00~11:00

国立研究開発法人 物質・材料研究機構
千現地区 研究本館8階 中セミナー室
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Dr. Andrew Pratt (Department of Physics, University of York, York YO10 5DD, U.K.)

Tunnelling Magnetoresistance Modulated by Molecular Orientation of Organic Barrier

Combining non-magnetic organic semiconductors (OSCs) with ferromagnetic (FM) inorganic electrodes has been at the heart of developments in the field of organic spintronics over the past decade or so[1]. Going beyond conventional architectures in which the spin transport layer solely consists of an OSC, hybrid device structures offer a means of coupling high efficiency inorganic spin emitters with an organic layer in which spin diffusion lengths are longer than inorganic alternatives[1]. However, demonstrating spin-polarised transport of charge carriers via intrinsic hopping between localised OSC states has proven problematic due to issues related to FM/OSC interface formation, principally the formation of metallic filaments during deposition of the top electrode[2], and the occurrence of hybrid interface states[3]. Inert oxide tunnel barriers can mitigate the latter effect in hybrid devices whilst metallic filaments can be reduced through morphological control of the OSC layer, either through low temperature amorphous growth[4] or the use of high symmetry, isotropic molecules such as C60[5]. Here, we demonstrate how an alternative low temperature growth mode, in which CuPc films quasi-epitaxially form on MgO(001), also leads to enhanced spin transport in a hybrid MTJ.

[1] V. A. Dediu et al., Nat. Mater. 8, 707 (2009); Z. H. Xiong et al., Nature 427, 821 (2004); C. Barraud et al., Nat. Phys. 6, 615 (2010).
[2] H. Vinzelberg et al., J. Appl. Phys. 103, 093720 (2008).
[3] T.-N. Lam et al., Phys. Rev. B 91, 041204(R) (2015).
[4] X. Sun et al., Adv. Mater. 28, 2609 (2016).
[5] X. Zhang et al., Nature Comms. 4, 1392 (2013).