13:30 〜 15:30
▲ [18p-PB1-81] Spin-Polarized Coherent Tunneling in Fully Epitaxial Magnetic Tunnel Junctions with SrO Tunnel Barrier
キーワード：oxide tunnel barrier, tunneling magnetoresistance, coherent spin-dependent tunneling
An efficient way to induce a large spin polarization in Si is to take advantage of the spin filtering effect in epitaxial ferromagnet/crystalline oxide tunnel barriers. With this method, we recently demonstrated the creation of a giant spin accumulation in Si using epitaxial Fe/MgO tunnel contacts [1,2] and found that the tunnel spin polarization (P) of Fe/MgO on Si can reach up to ~ 90% at 10 K [2]. However, for MgO thicknesses below 1 nm, we observed a rapid drop of the P to values below 25 % [2]. A low P for thin tunnel barrier thicknesses would be a major obstacle for achieving large magnetoresistance (MR) in a two-terminal Si-based device. From a crystal growth viewpoint, rock-salt type SrO is better lattice-matched to Si than MgO. Here, we fabricate magnetic tunnel junctions (MTJs) with an epitaxial SrO tunnel barrier and examine its ability for spin-dependent tunneling by measuring MR effect.
The structure of the MTJ consists of Au (10 nm) / Co (20 nm) / SrO (1.5 nm) / MgO (1.0 nm) / Fe (30 nm) on a MgO(001) substrate. From the scanning transmission electron microscopy (STEM) image of the MTJ (Fig. 1), we observe a fully epitaxial structure without significant diffusion or intermixing. We observe high MR ratios up to 90% at room temperature, indicating that spin-polarized coherent tunneling occurs through the SrO barrier. Besides, for equivalent barrier thicknesses, the resistance-area products of the MTJs with SrO are comparable to that of epitaxial Fe/MgO/Fe MTJs. Therefore, SrO presents valuable properties as a novel tunnel barrier for high MR ratio in Si-based lateral devices.
This work was supported by JSPS KAKENHI (Grant No. 18K13807, A.S.).
Reference :
[1] A. Spiesser et al., Phys. Rev. Appl. 8, 064023 (2017).
[2] A. Spiesser et al., to be published in Phys. Rev. B (2019).
The structure of the MTJ consists of Au (10 nm) / Co (20 nm) / SrO (1.5 nm) / MgO (1.0 nm) / Fe (30 nm) on a MgO(001) substrate. From the scanning transmission electron microscopy (STEM) image of the MTJ (Fig. 1), we observe a fully epitaxial structure without significant diffusion or intermixing. We observe high MR ratios up to 90% at room temperature, indicating that spin-polarized coherent tunneling occurs through the SrO barrier. Besides, for equivalent barrier thicknesses, the resistance-area products of the MTJs with SrO are comparable to that of epitaxial Fe/MgO/Fe MTJs. Therefore, SrO presents valuable properties as a novel tunnel barrier for high MR ratio in Si-based lateral devices.
This work was supported by JSPS KAKENHI (Grant No. 18K13807, A.S.).
Reference :
[1] A. Spiesser et al., Phys. Rev. Appl. 8, 064023 (2017).
[2] A. Spiesser et al., to be published in Phys. Rev. B (2019).