Electronic Properties of Nanopore Edges of Ferromagnetic Graphene Nanomeshes at High Carrier Densities under Ionic-Liquid Gating

Taijyu Hashimoto, Syota Kamikawa, Yuko Yagi, Junji Haruyama

Faculty of Science and Engineering, Aoyama Gakuin University, Sagamihara, Japan.

DOI: 10.4236/msa.2014.51001                

Abstract

Graphene edges with a zigzag-type atomic structure can theoretically produce spontaneous spin polarization despite being a critical-metal-free material. We have demonstrated this in graphene nanomeshes (GNMs) with honeycomb-like arrays of low-defect hexagonal nanopores by observing room-temperature ferromagnetism and spin-based phenomena arising from the zigzag-pore edges. Here, we apply extremely high electric fields to the ferromagnetic (FM) GNMs using an ionic-liquid gate. A large on/off-ratio for hole current is observed for even small applied ionic-liquid gate voltages (V_ig). Observations of the magnetoresistance behavior reveal high carrier densities of ~10¹³ cm^-2 at large V_ig values. We find a maximum conductance peak in the high -V_ig region and its separation into two peaks upon applying a side-gate (in-plane external) voltage (V_ex). It is discussed that localized edge-π band with excess-density electrons induced by V_ig and its spin splitting for majority and minority of spins by V_ex (half-metallicity model) lead to these phenomena. The results must realize critical-element-free novel spintronic devices.

Keywords

Graphene; Nanomesh; Edge; Spin Polarization; Magnetism; Ionic-Liquid Gate; High Electric Fields; Rare-Metal-Free Spintronics

Conflicts of Interest

The authors declare no conflicts of interest.

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