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Enhanced finite size and interface mixing effects in iridium manganese ultra thin films
摘要： The finite size and temperature dependent properties of antiferromagnets are of critical importance to a wide range of spintronic and neuromorphic computing devices. Here we present atomistic simulations of IrMn, one of the most technologically important antiferromagnets, in both the ordered (L12) and disordered (γ) phases. We have found that antiferromagnetic IrMn3 films show a stronger finite size dependence of the Néel temperature than an equivalent ferromagnet due to the existence of spin frustration. We also find that the disordered γ-IrMn3 phase shows a dramatic reduction in the Néel temperature to less than room temperature for films less than 1 nm thick. Interfacial intermixing of the IrMn3 with a non-magnetic Cu capping layer further reduces the Néel temperature for a given film thickness, with a stronger influence on the disordered γ-IrMn3 phase compared to the ordered L12-IrMn3 phase. Our results suggest a larger antiferromagnetic film thickness is required for devices operating at or above room temperature compared to an equivalent ferromagnet, particularly for sputtered films with a high degree of interfacial intermixing.
关键词： Néel temperature,antiferromagnets,neuromorphic computing,IrMn,spintronic devices,finite size effects
更新于2025-09-23 15:21:21
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Epitaxial Mn <sub/>5</sub> Ge <sub/>3</sub> (100) layer on Ge (100) substrates obtained by flash lamp annealing
摘要： Mn5Ge3 thin films have been demonstrated as promising spin-injector materials for germanium-based spintronic devices. So far, Mn5Ge3 has been grown epitaxially only on Ge (111) substrates. In this letter, we present the growth of epitaxial Mn5Ge3 films on Ge (100) substrates. The Mn5Ge3 film is synthetized via sub-second solid-state reaction between Mn and Ge upon flash lamp annealing for 20 ms at the ambient pressure. The single crystalline Mn5Ge3 is ferromagnetic with a Curie temperature of 283 K. Both the c-axis of hexagonal Mn5Ge3 and the magnetic easy axis are parallel to the Ge (100) surface. The millisecond-range flash epitaxy provides a new avenue for the fabrication of Ge-based spin-injectors fully compatible with CMOS technology.
关键词： epitaxial growth,spintronic devices,Ge (100) substrates,flash lamp annealing,Mn5Ge3
更新于2025-09-23 15:21:21
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Ultrafast dynamics in van der Waals heterostructures
摘要： Van der Waals heterostructures are synthetic quantum materials composed of stacks of atomically thin two-dimensional (2D) layers. Because the electrons in the atomically thin 2D layers are exposed to layer-to-layer coupling, the properties of van der Waals heterostructures are defined not only by the constituent monolayers, but also by the interactions between the layers. Many fascinating electrical, optical and magnetic properties have recently been reported in different types of van der Waals heterostructures. In this Review, we focus on unique excited-state dynamics in transition metal dichalcogenide (TMDC) heterostructures. TMDC monolayers are the most widely studied 2D semiconductors, featuring prominent exciton states and accessibility to the valley degree of freedom. Many TMDC heterostructures are characterized by a staggered band alignment. This band alignment has profound effects on the evolution of the excited states in heterostructures, including ultrafast charge transfer between the layers, the formation of interlayer excitons, and the existence of long-lived spin and valley polarization in resident carriers. Here we review recent experimental and theoretical efforts to elucidate electron dynamics in TMDC heterostructures, extending from timescales of femtoseconds to microseconds, and comment on the relevance of these effects for potential applications in optoelectronic, valleytronic and spintronic devices.
关键词： spin and valley polarization,charge transfer,valleytronic,transition metal dichalcogenide,Van der Waals heterostructures,excited-state dynamics,spintronic devices,interlayer excitons,optoelectronic
更新于2025-09-23 15:21:01
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Rashba splitting in bilayer transition metal dichalcogenides controlled by electronic ferroelectricity
摘要： Based on ?rst-principles calculations and k · p model analyses, we uncover the coexistence and coupling of Rashba spin splitting with electronic ferroelectricity in bilayer transition metal dichalcogenides MX2 (M = Mo,W; X = S,Se,Te) with certain stacking con?gurations. The reversible spontaneous ferroelectric polarization, along the out-of-plane direction (the preferred direction for applications), totally arises from the interlayer charge transfer, rather than being governed by the ionic displacement as found in conventional ferroelectrics. The spin texture related to the Rashba spin splitting can be reversed upon inversion of the ferroelectric polarization. In particular, by applying a small in-plane compressive strain, the magnitude of Rashba band splitting can be tuned to be as large as 100 meV. These results would open up possibilities for exploring two-dimensional multiferroic physics and developing electrically controlled nanoscale spintronic devices.
关键词： Rashba splitting,bilayer transition metal dichalcogenides,spintronic devices,electronic ferroelectricity
更新于2025-09-11 14:15:04
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High-performance spin rectification in gallium nitride-based molecular junctions with asymmetric edge passivation
摘要： The spin transport properties of molecular devices constructed from zigzag gallium nitride nanoribbons (ZGaNNRs) are investigated by applying the non-equilibrium Green’s function formalism in combination with density functional theory. The computational results indicate that ZGaNNR systems show spin rectification with a high efficiency, approaching nearly 109, giant magnetoresistance with a ratio up to 108, perfect spin-filtering, and negative differential resistance effects. Importantly, our results reveal that intrinsic rectification can be observed regardless of their width. The microscopic origins of the rectification are revealed and discussed in terms of a spin-resolved transmission spectrum, the band structures of the ZGaNNRs, and the molecular projected self-consistent Hamiltonian. Our findings could be useful for designing GaN-based spintronic nanodevices.
关键词： spin transport,molecular junctions,asymmetric edge passivation,gallium nitride,spintronic devices
更新于2025-09-09 09:28:46
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Current‐Enhanced Broadband THz Emission from Spintronic Devices
摘要： An ultra-broadband terahertz (THz) emitter covering a wide range of frequencies from 0.1 to 10 THz is highly desired for spectroscopy applications. So far, spintronic THz emitters have been proven as one class of efficient THz sources with a broadband spectrum while the performance in the lower THz frequency range (0.1–0.5 THz) limits its applications. In this work, a novel concept of a current-enhanced broad spectrum from spintronic THz emitters combined with semiconductor materials is demonstrated. A 2–3 order enhancement of the THz signals in a lower THz frequency range (0.1–0.5 THz) is observed, in addition to a comparable performance at higher frequencies from this hybrid emitter. With a bias current, there is a photoconduction contribution from semiconductor materials, which can be constructively interfered with the THz signals generated from the magnetic heterostructures driven by the inverse spin Hall effect (ISHE). These findings push forward the utilization of metallic heterostructure-based THz emitters on the ultra-broadband THz emission spectroscopy.
关键词： spintronic devices,broadband spectrum,photoconduction,terahertz emitters
更新于2025-09-04 15:30:14