Giant Enhancements of Perpendicular Magnetic Anisotropy and Spin‐Orbit Torque by a MoS₂ Layer

Abstract

Abstract2D transition metal dichalcogenides have attracted much attention in the field of spintronics due to their rich spin‐dependent properties. The promise of highly compact and low‐energy‐consumption spin‐orbit torque (SOT) devices motivates the search for structures and materials that can satisfy the requirements of giant perpendicular magnetic anisotropy (PMA) and large SOT simultaneously in SOT‐based magnetic memory. Here, it is demonstrated that PMA and SOT in a heavy metal/transition metal ferromagnet structure, Pt/[Co/Ni]2, can be greatly enhanced by introducing a molybdenum disulfide (MoS2) underlayer. According to first‐principles calculation and X‐ray absorption spectroscopy (XAS), the enhancement of the PMA is ascribed to the modification of the orbital hybridization at the interface of Pt/Co due to MoS2. The enhancement of SOT by the role played by MoS2 is explained, which is strongly supported by the identical behavior of SOT and PMA as a function of Pt thickness. This work provides new possibilities to integrate 2D materials into promising spintronics devices.

Van der Waals magnets: Wonder building blocks for two‐dimensional spintronics?

“…Together with favorable magnetic softness, considerable magnetic moment preserved at the interface, and theoretically predicted interfacial band matching for spin filtering, this kind of FM/2D‐TMD interface provides attractive opportunities for 2D spintronic devices with atomic‐level control of their interface properties . A similar work of enhancing the PMA by introducing a TMD layer is reported for the multilayer of Pt/[Co/Ni] 2 /MoS 2 (Figure D) . By inserting a sputtering MoS 2 underlayer transferred onto the substrate, the PMA and spin‐orbit‐torque efficiency are seen to significantly enhance, originating from the effect of modified orbital hybridization at the Pt/Co interface.…”

“…C, XMCD measurement geometry and hysteresis of CoFeB/MoSe 2 interface grown on graphene/SiC substrate, evidencing PMA . D, Ni/Co multilayer grown on MoS 2 with a Pt buffer layer with enhanced uniaxial magnetic anisotropy constant perpendicular to the film plane…”

“…149 A similar work of enhancing the PMA by introducing a TMD layer is reported for the multilayer of Pt/[Co/Ni] 2 /MoS 2 ( Figure 7D). 150 By inserting a sputtering MoS 2 underlayer transferred onto the substrate, the PMA and spin-orbit-torque efficiency are seen to significantly enhance, originating from the effect of modified orbital hybridization at the Pt/Co interface. These works provide new possibilities to integrate 2D materials into promising spintronics devices.…”

MoS2/Polymer Heterostructures Enabling Stable Resistive Switching and Multistate Randomness

“…The difference in frequency between the A 1g and the E 1 2g peak for the sputter‐grown MoS 2 monolayer is about 19.8 cm −1 , which increases to 22.1 cm −1 and 24.2 cm −1 for bilayer (Figure 1d) and five layers, respectively, in line with previous reports. [ 11,12 ] The uniformity of the MoS 2 layers can be seen from the inserted Raman mapping in Figure 1d and Figure S2, Supporting Information, in which the variation of the A 1g peak position is not noticeable in the large mapping area. The atomic force microscopy (AFM) image in Figure 1e further confirms continuous and smooth MoS 2 layers with atomically flat surface, where the surface roughness (root‐mean‐square) is estimated to be ≈0.3 nm, comparable to that of the bare SiO 2 substrate.…”

Prospect of Spin-Orbitronic Devices and Their Applications

“…Particularly, in semiconductor/FM heterostructures such as GaAs/Fe and paramagnetic (Ga,Mn)As/Fe bilayers, SOTs that originated at the interfaces were elucidated in detail ( Chen et al., 2016 , 2018b ). Some layered van der Waals crystals also exhibit strong SOC and an appreciable range of broken crystal symmetries; most recently, the strong spin-orbit current and efficient SOTs were observed in transition metal chalcogenide (TMD)/FM heterostructures involving MoS 2 ( Xie et al., 2019 ), WSe 2 ( Shao et al., 2016 ), Dirac semimetal PtTe 2 ( Xu et al., 2020 ), or Weyl semimetal WTe 2 ( MacNeill et al., 2017 ; Shi et al., 2019 ; Li et al., 2018 ; Zhao et al., 2020 ) and MoTe 2 ( Song et al., 2020b ). Topological insulators (TIs) of Bi 1-x Sb x and their chalcogenides (X 2 Q 3 , X = Bi, Sb, Bi 1-x Sb x ; Q = Se, Te) with strong spin-momentum locking in the conductive surface are expected as promising source of SOTs ( Khang et al., 2018 ; Wang et al., 2017 ; Mahendra et al., 2018 ; Chen et al., 2020b ; Han et al., 2017 ).…”