Abstract
AbstractIt is generally accepted that perpendicular magnetic anisotropy (PMA) magnets are preferred over in‐plane magnetic anisotropy (IMA) magnets in data storage applications owing to their large thermal stability even at ultra‐scaled dimensions. To efficiently and deterministically switch a PMA, out‐of‐plan spin current is required. However, conventional giant spin Hall effect (GSHE) materials only produce spin currents with in‐plane polarization. Our work, on the other hand, demonstrated for the first time that out‐of‐plane spin currents can indeed be generated by applying electric filed to monolayer WSe2 at room temperature and the spin information was detected by a graphene channel. Supported by theoretical calculations, we found that the interfacial polarization between graphene and WSe2 to be ~38% assuming the ferromagnetic detector's polarization efficiency to be ~4%. Moreover, the spin polarization is determined by the polarity of the applied electric field.image
Highlights
Several optical measurements such as pump-probe using circularly polarized light[19,20,21,22] and Kerr rotation microscopy[23] have shown ultra-long valley life time in transition metal dichalcogenides (TMDs) and their heterostructures and associate that to long spin life time based on the spin-locking theory[10,11]
spin orbit torque (SOT) switching of perpendicular magnetic anisotropy (PMA) magnets by conventional Giant spin Hall effect (GSHE) materials requires either a small external magnetic field[5,6], a local dipolar field[7], or introducing tilted anisotropy to break the symmetry with respect to the magnetization[8,9]
Opposite spins are locked to their respective sub-band in each K valley of the TMD valence band with substantially large energy splitting, which enables polarized spins to be accessible through electrical gating and spatially separated by electric field through the valley Hall effect (VHE)[13,14,15,16,17,18]
Summary
Figure S8. | Material and Device Characterizations. (a, b) Raman spectra of monolayer WSe2 and graphene, respectively. (c) Colored SEM image. (a, b) Raman spectra of monolayer WSe2 and graphene, respectively. Yellow electrodes are non-magnetic metal electrodes of Ti/Pd/Au (0.5nm/15nm/70nm), purple electrode is the ferromagnetic contact of Py (20nm), green is the monolayer WSe2, rectangle grey area is graphene, and the substrate is 90nm SiO2/Si. The scale bar is 1um. (d, e) Transfer characteristics of monolayer WSe2 and graphene, respectively. The channel length lch is 2.5, 1.2, and 1.2 um for (a, d), (b, e), and (c, f) respectively
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