Abstract
Two-dimensional (2D) layered materials and their heterostructures have opened a new avenue for next-generation spintronic applications, benefited by their unique electronic properties and high crystallinity with an atomically flat surface. Here, we report magnetoresistance of vertical magnetic spin-valve devices with multi-layer (ML) MoSe2 and its heterostructures with few-layer graphene (FLG). We employed a micro-fabrication procedure to form ultraclean ferromagnetic–non-magnetic–ferromagnetic interfaces to elucidate the intrinsic spin-transferring mechanism through both an individual material and combinations of 2D layered materials. However, it is revealed that the polarity of tunneling magnetoresistance (TMR) is independent of non-magnetic spacers whether the spin valve is composed of a single material or a hybrid structure, but it strongly depends on the interfaces between ferromagnetics (FMs) and 2D materials. We observed positive spin polarizations in ML-MoSe2 and FLG/ML-MoSe2/FLG tunnel junctions, whereas spin-valve devices comprised of FLG/ML-MoSe2 showed a reversed spin polarization and demonstrated a negative TMR. Importantly, in Co/FLG/ML-MoSe2/FLG/NiFe devices, the polarization of spin carriers in the FM/FLG interface remained conserved during tunneling through MoSe2 flakes in spin-transferring events, which is understandable by Julliere’s model. In addition, large TMR values are investigated at low temperatures, whereas at high temperatures, the TMR ratios are deteriorated. Furthermore, the large values of driving ac-current also quenched the amplitude of TMR signals. Therefore, our observations suggest that the microscopic spin-transferring mechanism between ferromagnetic metals and 2D materials played a momentous role in spin-transferring phenomena in vertical magnetic spin-valve junctions.
Highlights
Tunneling magnetoresistance (TMR) is one of the most important features in spin-based electronic applications, such as magnetic random-access memories, magnetic sensors, logic circuits, and spin field effect switches.1–4 Fruitions of such far-and-wide accomplishments in tunneling magnetoresistance (TMR) have strongly relied on a detailed understanding of spin-manipulating mechanisms, through the non-magnetic (NM) spacers, encapsulated between two ferromagnetic (FM) electrodes, and at the interfaces between NM spacers and FM electrodes
It is revealed that the polarity of tunneling magnetoresistance (TMR) is independent of non-magnetic spacers whether the spin valve is composed of a single material or a hybrid structure, but it strongly depends on the interfaces between ferromagnetics (FMs) and 2D materials
We found that the TMR ratios in both symmetric junctions (ML-MoSe2 and few-layer graphene (FLG)/MoSe2/FLG) are positive, with a magnitude as high as 2.3% at T = 5 K for the former and close to 3.4% at T = 5 K for the latter
Summary
Tunneling magnetoresistance (TMR) is one of the most important features in spin-based electronic applications, such as magnetic random-access memories, magnetic sensors, logic circuits, and spin field effect switches. Fruitions of such far-and-wide accomplishments in TMR have strongly relied on a detailed understanding of spin-manipulating mechanisms, through the non-magnetic (NM) spacers, encapsulated between two ferromagnetic (FM) electrodes, and at the interfaces between NM spacers and FM electrodes. Tunneling magnetoresistance (TMR) is one of the most important features in spin-based electronic applications, such as magnetic random-access memories, magnetic sensors, logic circuits, and spin field effect switches.. Tunneling magnetoresistance (TMR) is one of the most important features in spin-based electronic applications, such as magnetic random-access memories, magnetic sensors, logic circuits, and spin field effect switches.1–4 Fruitions of such far-and-wide accomplishments in TMR have strongly relied on a detailed understanding of spin-manipulating mechanisms, through the non-magnetic (NM) spacers, encapsulated between two ferromagnetic (FM) electrodes, and at the interfaces between NM spacers and FM electrodes. Orbit coupling in transition-metal-based semiconducting films gives rise to a unique spin and valley polarization, which has been drawing wide interest for manipulating the spin polarization of vertical magnetic tunnel junctions. Monolayer MoSe2, with its long valley exciton lifetime, is a superior contender to provide an intriguing platform for 2D heterostructures in spintronic and valleytronic applications.
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