Room-Temperature Spin-Valve Effect in Fe3_3GaTe2_2/MoS2_2/Fe3_3GaTe2_2 2D van der Waals Heterojunction Devices

Spin-valve effect has been the focus of spintronics over the last decades due to its potential in many spintronic devices. Two-dimensional (2D) van der Waals (vdW) materials are highly expected to build the spin-valve heterojunction. However, the Curie temperatures (TC) of the vdW ferromagnetic 2D crystals are mostly below room temperature (~30-220 K). It is very challenging to develop room temperature, ferromagnetic (FM) 2D crystals based spin-valve devices which are still not available to date. We report the first room temperature, FM 2D crystal based all-2D vdW Fe3GaTe2/MoS2/Fe3GaTe2 spin valve devices. The Magnetoresistance (MR) of the all- devices is up to 15.89% at 2.3 K and 11.97% at 10 K, 4-30 times of MR from the spin valves of Fe$_3$GaTe$_2$/MoS$_2$/Fe$_3$GaTe$_2$ and conventional NiFe/MoS$_2$/NiFe. Typical spin valve effect shows strong dependence on MoS2 spacer thickness in the vdW heterojunction. Importantly, the spin valve effect (0.31%) still robustly exists at 300 K with low working currents down to 10 nA (0.13 A/cm$^2$). The results provide a general vdW platform to room temperature, 2D FM crystals based 2D spin valve devices

Room-temperature and tunable tunneling magnetoresistance in Fe3GaTe2-based all-2D van der Waals heterojunctions with high spin polarization

Magnetic tunnel junctions (MTJs) based on all-two dimensional (2D) van der Waals heterostructures with sharp and clean interfaces in atomic scale are essential for the application of next-generation spintronics. However, the lack of room-temperature intrinsic ferromagnetic crystals with perpendicular magnetic anisotropy has greatly hindered the development of vertical MTJs. The discovery of room-temperature intrinsic ferromagnetic 2D crystal Fe3GaTe2 has solved the problem and greatly facilitated the realization of practical spintronic devices. Here, we demonstrate a room-temperature MTJ based on Fe3GaTe2/WS2/Fe3GaTe2 heterostructure. The tunnelling magnetoresistance (TMR) ratio is up to 213% with high spin polarization of 72% at 10 K, the highest ever reported in Fe3GaTe2-based MTJs up to now. The tunnelling spin-valve signal robustly exists at room temperature (300 K) with bias current down to 10 nA. Moreover, the spin polarization can be modulated by bias current and the TMR shows a sign reversal at large bias current. Our work sheds light on the potential application for low-energy consumption all-2D vdW spintronics and offers alternative routes for the electronic control of spintronic devices

Experimental 5G New Radio integration with VLC

International audienceIn this paper, integration of 5G New Radio (5G NR) with a Visible Light Communication (VLC) downlink architecture is proposed. This scheme combines two complementary wireless technologies: upcoming 5G NR and VLC to offer indoor enhanced wireless hybrid access able to provide each User Equipment (UE) with very high data rate and positioning support. The data transmission of the 5G NR frame over VLC has been implemented. This represents a novel approach to transmitting 5G NR over VLC by hardware experimentation based on Universal Software Radio Peripheral (USRP). The experiment results show that the proposed scheme with Quadrature Phase Shift Keying (QPSK) mapping achieves a data rate of 14.4 M bits/s and an Error Vector Magnitude (EVM) of 4.78% for a 55 cm free space transmission span

High Flow Nasal Catheter (HFNC) for Sepsis Induced Respiratory Failure After Extubation Meta Analysis of Clinical Control Studies on Reintubation Rate and Mortality

Objective: To analyze the reintubation rate and mortality of patients with sepsis complicated (or induced) respiratory failure after extubation, and to seek evidence-based basis for the efficacy of HFNC in the re intubation rate and mortality of sepsis induced respiratory failure after extubation. Methods: The databases of PubMed, EMBASE, Ovid, CNKI, CBM, VIP and Wanfang were searched to find the clinical studies of patients with sepsis and respiratory failure, and meta-analysis was carried out by Stata software. Results: Meta analysis showed that there was no significant difference between HFNC and noninvasive positive pressure ventilation (NPPV) in 72 hour reintubation rate, mortality during ICU and 28-day in hospital. Conclusion: The reintubation rate and mortality of HFNC after extubation in sepsis induced respiratory failure are equivalent to that of NPPV

Rate-Splitting and Sum-DoF for the KK-User MISO Broadcast Channel with Mixed CSIT and Order-(K−1)(K-1) Messages

In this paper, we propose a rate-splitting design and characterize the sum-degrees-of-freedom (DoF) for the $K$-user multiple-input-single-output (MISO) broadcast channel with mixed channel state information at the transmitter (CSIT) and order-$(K-1)$ messages, where mixed CSIT refers to the delayed and imperfect-current CSIT, and order-$(K-1)$ message refers to the message desired by $K-1$ users simultaneously. In particular, for the sum-DoF lower bound, we propose a rate-splitting scheme embedding with retrospective interference alignment. In addition, we propose a matching sum-DoF upper bound via genie signalings and extremal inequality. Opposed to existing works for $K=2$, our results show that the sum-DoF is saturated with CSIT quality when CSIT quality thresholds are satisfied for $K>2$.Comment: This work has been accepted by VTC2023-Fal

On DoF of Active RIS-Assisted MIMO Interference Channel with Arbitrary Antenna Configurations: When Will RIS Help?

An active reconfigurable intelligent surface (RIS) has been shown to be able to enhance the sum-of-degrees-of-freedom (DoF) of a two-user multiple-input multiple-output (MIMO) interference channel (IC) with equal number of antennas at each transmitter and receiver. However, for any number of receive and transmit antennas, when and how an active RIS can help to improve the sum-DoF are still unclear. This paper studies the sum-DoF of an active RIS-assisted two-user MIMO IC with arbitrary antenna configurations. In particular, RIS beamforming, transmit zero-forcing, and interference decoding are integrated together to combat the interference problem. In order to maximize the achievable sum-DoF, an integer optimization problem is formulated to optimize the number of eliminating interference links by RIS beamforming. As a result, the derived achievable sum-DoF can be higher than the sum-DoF of two-user MIMO IC, leading to a RIS gain. Furthermore, a sufficient condition of the RIS gain is given as the relationship between the number of RIS elements and the antenna configuration.Comment: This paper has been accepted by IEEE Transactions on Vehicular Technology (TVT

Rate-Splitting with Hybrid Messages: DoF Analysis of the Two-User MIMO Broadcast Channel with Imperfect CSIT

Most of the existing research on degrees-of-freedom (DoF) with imperfect channel state information at the transmitter (CSIT) assume the messages are private, which may not reflect reality as the two receivers can request the same content. To overcome this limitation, we consider hybrid private and common messages. We characterize the optimal DoF region for the two-user multiple-input multiple-output (MIMO) broadcast channel with hybrid messages and imperfect CSIT. We establish a three-step procedure for the DoF converse to exploit the utmost possible relaxation. For the DoF achievability, since the DoF region has a specific three-dimensional structure w.r.t. antenna configurations and CSIT qualities, by dividing CSIT qualities into cases, we check the existence of corner point solutions, and then design a hybrid messages-aware rate-splitting scheme to achieve them. Besides, we show that to achieve the strictly positive corner points, it is unnecessary to split the private messages into unicast and multicast parts because the allocated power for the multicast part should be zero. This implies that adding a common message can mitigate the rate-splitting complexity of private messages.Comment: 32page

Giant 2D Skyrmion Topological Hall Effect with Ultrawide Temperature Window and Low-Current Manipulation in 2D Room-Temperature Ferromagnetic Crystals

The discovery and manipulation of topological Hall effect (THE), an abnormal magnetoelectric response mostly related to the Dzyaloshinskii-Moriya interaction (DMI), are promising for next-generation spintronic devices based on topological spin textures such as magnetic skyrmions. However, most skyrmions and THE are stabilized in a narrow temperature window either below or over room temperature with high critical current manipulation. It is still elusive and challenging to achieve large THE with both wide temperature window till room temperature and low critical current manipulation. Here, by using controllable, naturally-oxidized, sub-20 and sub-10 nm 2D van der Waals room-temperature ferromagnetic Fe3GaTe2-x crystals, robust 2D THE with ultrawide temperature window ranging in three orders of magnitude from 2 to 300 K is reported, combining with giant THE of ~5.4 micro-ohm cm at 10 K and ~0.15 micro-ohm cm at 300 K which is 1-3 orders of magnitude larger than that of all known room-temperature 2D skyrmion systems. Moreover, room-temperature current-controlled THE is also realized with a low critical current density of ~6.2*10^5 A cm^-2. First-principles calculations unveil natural oxidation-induced highly-enhanced 2D interfacial DMI reasonable for robust giant THE. This work paves the way to room-temperature, electrically-controlled 2D THE-based practical spintronic devices