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▲ [18a-E216-9] Pronounced Scaling of the tunnel Spin Polarization of Fe/MgO/silicon Contacts with MgO Thickness
Keywords:tunnel spin polarization, spin transport, coherent spin-dependent tunneling
The discovery of giant tunnel magnetoresistance in crystalline Fe/MgO/Fe magnetic tunnel junctions greatly accelerated the development of practical spintronic applications. Inspired by this success, crystalline MgO has also widely been used in semiconductor spintronic devices. Indeed, it has been shown that a charge current across a FM/MgO/semiconductor tunnel junction results in spin injection into the semiconductor. With this approach, we recently demonstrated the creation of a giant spin accumulation in Si using Fe/MgO tunnel contacts1. However, some important questions remain, such as how the tunnel spin polarization (TSP) varies as a function of the MgO thickness and what is the role of symmetry-based spin filtering due to coherent tunneling in Fe/MgO tunnel contacts on Si. Here we report on these two aspects2.
The Fe/MgO contacts were deposited on a Si substrate having a Si(001) channel and a MgO thickness (tMgO) varying from 0.75 nm to 2.3 nm. The spin current produced by a charge current across the Fe/MgO/Si tunnel junction was measured using the standard 4-terminal nonlocal geometry. The TSP was extracted from the magnitude of the nonlocal spin-valve and Hanle signals. The TSP depends sensitively on tMgO, increasing from values below 1 % at small thickness, to values in the 90 to 95 % range for tMgO above 2 nm. Such a near-perfect spin polarization of the tunnel current indicates that symmetry-based spin filtering due to coherent tunneling occurs in Fe/MgO tunnel contacts on Si, despite the significant lattice mismatch. The pronounced scaling of the TSP with MgO thickness has important implications for achieving large magnetoresistance in Si-based devices.
References:
1. A. Spiesser H. Saito, Y. Fujita, et al., Phys. Rev. Appl. 8, 064023 (2017).
2. A. Spiesser H. Saito, S. Yuasa et al., to be published in Phys. Rev. B, (2019).
The Fe/MgO contacts were deposited on a Si substrate having a Si(001) channel and a MgO thickness (tMgO) varying from 0.75 nm to 2.3 nm. The spin current produced by a charge current across the Fe/MgO/Si tunnel junction was measured using the standard 4-terminal nonlocal geometry. The TSP was extracted from the magnitude of the nonlocal spin-valve and Hanle signals. The TSP depends sensitively on tMgO, increasing from values below 1 % at small thickness, to values in the 90 to 95 % range for tMgO above 2 nm. Such a near-perfect spin polarization of the tunnel current indicates that symmetry-based spin filtering due to coherent tunneling occurs in Fe/MgO tunnel contacts on Si, despite the significant lattice mismatch. The pronounced scaling of the TSP with MgO thickness has important implications for achieving large magnetoresistance in Si-based devices.
References:
1. A. Spiesser H. Saito, Y. Fujita, et al., Phys. Rev. Appl. 8, 064023 (2017).
2. A. Spiesser H. Saito, S. Yuasa et al., to be published in Phys. Rev. B, (2019).