High-speed Data Storage Research Articles

Electrically controlled nonvolatile switching of single-atom magnetism in a Dy@C84 single-molecule transistor

Single-atom magnetism switching is a key technique towards the ultimate data storage density of computer hard disks and has been conceptually realized by leveraging the spin bistability of a magnetic atom under a scanning tunnelling microscope. However, it has rarely been applied to solid-state transistors, an advancement that would be highly desirable for enabling various applications. Here, we demonstrate realization of the electrically controlled Zeeman effect in Dy@C84 single-molecule transistors, thus revealing a transition in the magnetic moment from 3.8 μB\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mu }_{{{{{{\\rm{B}}}}}}}$$\\end{document} to 5.1 μB\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mu }_{{{{{{\\rm{B}}}}}}}$$\\end{document} for the ground-state GN at an electric field strength of 3−\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-$$\\end{document}10 MV/cm. The consequent magnetoresistance significantly increases from 600% to 1100% at the resonant tunneling point. Density functional theory calculations further corroborate our realization of nonvolatile switching of single-atom magnetism, and the switching stability emanates from an energy barrier of 92 meV for atomic relaxation. These results highlight the potential of using endohedral metallofullerenes for high-temperature, high-stability, high-speed, and compact single-atom magnetic data storage.

Study of the spin-polarized electronic, exchange constant, and thermoelectric characteristics of spinels LiFe2(O/S)4 for spintronic and energy-harvesting applications

Spintronics is a rapidly developing field in advanced technology. It focuses on manipulating the spin of electrons to achieve high-speed data transfer, handling, and storage in order to enhance its capabilities. We conducted a systematic investigation of the ferromagnetism, electronic, and thermoelectric characteristics of spinel compounds LiFe2(O/S)4. Our analysis for optimization demonstrates that ferromagnetic states exhibit great energy release compared to the antiferromagnetic states, indicating the presence of ferromagnetic behavior in the studied compounds. To evaluate the presence of ferromagnetism above room temperature, we employ the Heisenberg model to calculate the Curie temperature and spin polarization to evaluate the presence of ferromagnetism above room temperature. Additionally, a concise overview of the nature of ferromagnetism, including band structures, density of states, exchange energies and constants, hybridization double exchange model, and crystal-field energy, is provided in this research. The absorption of a shift in magnetic moment from Fe to the Li and O/S sites suggests that the ferromagnetic behavior is primarily due to the spin of electrons. Furthermore, we explore the impact of the thermal parameters on the electro-spin as well as the thermoelectric characteristics for both spin-down and spin-up states, providing insights into the energy-harvesting potential.

StarFront: Cooperatively Constructing Pervasive and Low-Latency CDNs Upon Emerging LEO Satellites and Clouds

Internet content providers (ICPs) typically exploit content distribution networks (CDNs) to provide wide-area data access with high availability and low latency. However, our analysis on a large-scale trace collected from seven major CDN operators has revealed that: from a global perspective, there are still a large portion of users suffering from high user-perceived latency due to the insufficient deployment of terrestrial cloud infrastructures, especially in remote or rural areas where even the closest available cache server is too far away. This paper presents, a cost-effective content distribution framework to optimize global CDNs and enable low content access latency anywhere. collaboratively builds CDNs upon emerging low earth orbit (LEO) constellations and existing cloud platforms to satisfy the low latency requirements while minimizing the operational cost. Specifically, exploits a key insight that emerging mega-constellations will consist of thousands of LEO satellites which can be equipped with high-speed data links and storage, and thus can potentially work as “cache in space” to enable pervasive and low-latency data access. judiciously places replicas on either LEO satellite caches or terrestrial cloud caches, and dynamically assigns user requests to proper cache servers based on different constellation parameters, cloud/user distributions and pricing policies. We have implemented a prototype in our testbed, and extensive trace-driven evaluations covering multiple geo-distributed vantage points have demonstrated that can effectively reduce the global content access latency with acceptable operational cost under representative CDN traffic.

Subnanosecond Reconfiguration of Ferroelectric Domains in Bismuth Ferrite.

Domain switching is crucial for achieving desired functions in ferroic materials that are used in various applications. Fast control of domains at subnanosecond timescales remains a challenge despite its potential for high-speed operation in random-access memories, photonic, and nanoelectronic devices. In this work, ultrafast laser excitation is shown to transiently melt and reconfigure ferroelectric stripe domains in multiferroic bismuth ferrite on a timescale faster than 100ps. This dynamic behavior is visualized by picosecond- and nanometer-resolved X-ray diffraction measurements as well as time-resolved X-ray diffuse scattering. The disordering of stripe domains is attributed to the screening of depolarization fields by photogenerated carriers resulting in the formation of charged domain walls, as supported by phase field simulations. Furthermore, the recovery of disordered domains exhibits subdiffusive growth on nanosecond timescales, with a nonequilibrium domain velocity reaching up to 10 m/s. These findings present a new approach to image and manipulate ferroelectric domains on subnanosecond timescales, which can be further extended into other photoferroic systems to modulate their electronic, optical, and magnetic properties beyond GHz frequencies. This approach could pave the way for high-speed ferroelectric data storage, computing and photonic applications in a range of photoferroics, and, more broadly, defines new approaches for visualizing the non-equilibrium dynamics of heterogeneous and disordered materials. This article is protected by copyright. All rights reserved.

Optical Bullets and Domain Walls with Cross Spatio-Dispersion and Having Kudryashov’s form of Self-Phase Modulation

In this paper, we investigate the retrieval of optical bullets and domain walls in a novel context, considering the interplay of cross spatio-dispersive effects and employing Kudryashov' s proposed form of self-phase modulation. The integration of these two key elements represents a significant advancement in the field of nonlinear optics, enabling the recovery of optical structures with enhanced precision and control. We propose an enhanced Kudryashov’s approach, which overcomes the limitations of conventional methods and facilitates the retrieval of optical bullets and domain walls even in the presence of cross spatio-dispersive effects. Kudryashov' s self-phase modulation mechanism has proven to be a powerful tool in controlling the nonlinear dynamics of optical systems, offering unique opportunities to manipulate light waves through phase variations induced by the medium' s response to intense optical fields. The results presented herein offer new insights into the intricate interplay between self-phase modulation and spatio-dispersive effects in nonlinear optical systems. Moreover, our findings provide a promising avenue for developing novel applications in ultrafast all-optical signal processing, such as the manipulation of light bullets for high-speed data transmission and storage. The enhanced retrieval and control of optical bullets and domain walls are expected to have a profound impact on the advancement of nonlinear optics and its practical implications.

Single-shot switching in Tb/Co-multilayer based nanoscale magnetic tunnel junctions

Magnetic tunnel junctions (MTJs) are elementary units of magnetic memory devices. For high-speed and low-power data storage and processing applications, fast reversal of the magnetization by an ultrashort laser pulse is extremely important. We demonstrate single-shot switching of Tb/Co-multilayer based nanoscale MTJs by combining the optical writing and the electrical read-out methods. A 90-fs-long laser pulse switches the magnetization of the storage layer (SL). The change in the tunneling magnetoresistance (TMR) between the SL and a reference layer (RL) is probed electrically across the oxide barrier. Single-shot switching is demonstrated by varying the cell diameter from 300 nm to 20 nm. The anisotropy, magnetostatic coupling, and switching probability exhibit cell-size dependence. By suitable association of laser fluence and magnetic field, successive commutation between high-resistance and low-resistance states is achieved. The nature of the magnetization reversal of both SL and RL in a continuous film is probed with a depth-resolved magneto-optical Kerr effect (MOKE) magnetometry. The ultrafast dynamics in the continuous full-MTJ stack is investigated with the time-resolved pump–probe technique. Our experimental findings provide strong support for the growing interest in ultrafast spintronic devices.

Readout Electronics for Spatial Distribution Measurement of Neutron Beam Flux in BNCT

Boron neutron capture therapy (BNCT) is a promising cancer treatment that selectively destroys tumor cells using a neutron beam. However, accurately and fast measuring the spatial distribution of neutron flux is critical to ensuring effective treatment. To address this challenge, Micromegas detectors are applied for the first time to measure the spatial distribution of neutron beam flux in BNCT. Due to the high flux, large area, and multiple components of the BNCT beam, the design of readout electronics that can handle high counting rate, large channel numbers, high integration, and discrimination of multiple beam components is challenging. This paper proposes a targeted readout electronics system to overcome this challenge. A modular readout structure based on the PCI Express (PXIe) platform is designed for 384-channel readout. A fully parallel readout structure is developed and fast shaper parameters are optimized to achieve high counting rate for each readout channel. A multi-channel high-speed, large-capacity caching technique is developed to address the high-speed data storage problem. Digital shapers are implemented in field-programmable gate array (FPGA) to achieve high integration. Tests demonstrate that each readout channel can support a counting rate of 800 kHz and achieve an excellent position resolution of 1.4 mm. Furthermore, final tests on the BNCT beam confirm that our system can successfully measure the flux spatial distribution of different neutron components.

A Novel Approach for Establishing Connectivity in Partitioned Mobile Sensor Networks using Beamforming Techniques

Network connectivity is one of the major design issues in the context of mobile sensor networks. Due to diverse communication patterns, some nodes lying in high-traffic zones may consume more energy and eventually die out resulting in network partitioning. This phenomenon may deprive a large number of alive nodes of sending their important time critical data to the sink. The application of data caching in mobile sensor networks is exponentially increasing as a high-speed data storage layer. This paper presents a deep learning-based beamforming approach to find the optimal transmission strategies for cache-enabled backhaul networks. In the proposed scheme, the sensor nodes in isolated partitions work together to form a directional beam which significantly increases their overall communication range to reach out a distant relay node connected to the main part of the network. The proposed methodology of cooperative beamforming-based partition connectivity works efficiently if an isolated cluster gets partitioned with a favorably large number of nodes. We also present a new cross-layer method for link cost that makes a balance between the energy used by the relay. By directly adding the accessible auxiliary nodes to the set of routing links, the algorithm chooses paths which provide maximum dynamic beamforming usage for the intermediate nodes. The proposed approach is then evaluated through simulation results. The simulation results show that the proposed mechanism achieves up to 30% energy consumption reduction through beamforming as partition healing in addition to guarantee user throughput.

Sneak Path Interference-Aware Adaptive Detection and Decoding for Resistive Memory Arrays

Resistive random-access memory (ReRAM) is an emerging non-volatile memory technology for high-density and high-speed data storage. However, the sneak path interference (SPI) occurred in the ReRAM crossbar array seriously affects its data recovery performance. In this letter, we first propose a quantized channel model of ReRAM, based on which we design both the one-bit and multi-bit channel quantizers by maximizing the mutual information of the channel. A key channel parameter that affects the quantizer design is the sneak path occurrence probability (SPOP) of the memory cell. We first use the average SPOP calculated statistically to design the quantizer, which leads to the same channel detector for different memory arrays. We then adopt the SPOP estimated separately for each memory array for the quantizer design, which is generated by an effective channel estimator and through an iterative detection and decoding scheme for the ReRAM channel. This results in an array-level SPI-aware adaptive detection and decoding approach. Moreover, since there is a strong correlation of the SPI that affects memory cells in the same rows/columns than that affecting cells in different rows/columns, we further derive a column-level scheme which outperforms the array-level scheme. We also propose a channel decomposition method that enables effective ways for theoretically analyzing the ReRAM channel. Simulation results show that the proposed SPI-aware adaptive detection and decoding schemes can approach the ideal performance with three quantization bits, with only one decoding iteration.

Simulation of Multisensor Energy Data Fusion Transformer Acquisition System Based on FPGA

In order to solve the problems of small signal acquisition range and poor acquisition accuracy of the existing multichannel acquisition system, a multisensor energy data fusion transformer acquisition system simulation method based on FPGA is proposed, and key hardware functions are designed and implemented. The system uses FPGA to control the core logic, synchronously collects and controls the energy data of the CCD camera and the laser rangefinder, organizes and uses an external large-capacity SDRAM group for buffering, and uses a dedicated PCI interface chip PLX9656 to achieve high-speed data transmission. Two pieces of sensor energy data and PCI bus energy data are stored in real time using a large-capacity disk array composed of multiple SATA hard disks. The function and performance of the energy data acquisition and storage system were tested. After the actual system test, the experimental results show that the transmission speed of the system through the PCI bus exceeds 200 MB/s, the writing speed of the continuous disk array is 240 MB/s, and the real-time acquisition and recording speed is 100 MB/ss. Conclusion. The system effectively solves the problems of high-speed data acquisition and storage and large capacity data transmission of key sensor nodes.

An In-Network Cooperative Storage Schema Based on Neighbor Offloading in a Programmable Data Plane

In scientific domains such as high-energy particle physics and genomics, the quantity of high-speed data traffic generated may far exceed the storage throughput and be unable to be in time stored in the current node. Cooperating and utilizing multiple storage nodes on the forwarding path provides an opportunity for high-speed data storage. This paper proposes the use of flow entries to dynamically split traffic among selected neighbor nodes to sequentially amortize excess traffic. We propose a neighbor selection mechanism based on the Local Name Mapping and Resolution System, in which the node weights are computed by combing the link bandwidth and node storage capability, and determining whether to split traffic by comparing normalized weight values with thresholds. To dynamically offload traffic among multiple targets, the cooperative storage strategy implemented in a programmable data plane is presented using the relative weights and ID suffix matching. Evaluation shows that our proposed schema is more efficient compared with end-to-end transmission and ECMP in terms of bandwidth usage and transfer time, and is beneficial in big science.

Across-Array Coding for Resistive Memories With Sneak-Path Interference and Lognormal Distributed Resistance Variations

Resistive random-access memory (ReRAM) is a promising non-volatile memory technology for achieving high-density and high-speed data storage. However, its crossbar array structure leads to a severe problem known as the sneak path interference (SPI), which is data dependent and correlated within a memory array. Meanwhile, variations of the memory fabrication process also cause deviation of memory cell resistances from their nominal values, which typically follows the lognormal distribution. In this letter, we first propose a cascaded channel model that incorporates these two key factors that affect the reliability of ReRAM. By analyzing the channel correlation of ReRAM caused by the SPI, we develop a novel scheme to estimate the probability of each memory cell to be affected by the SPI, based on which the log-likelihood ratio (LLR) of each channel bit can be generated. Moreover, we propose a novel two-step across-array bit allocation scheme, which distributes the low-density parity-check (LDPC) codewords to multiple memory arrays so as to minimize the correlation of the channel coded bits for decoding. Simulation results show that the proposed across-array bit allocation scheme with LDPC coding can achieve significantly better error rate performance than the prior art coding schemes, with similar implementation complexity and latency.

SCADA-Based Message Generator for Multi-Vendor Smart Grids: Distributed Integration and Verification of TASE.2.

Recent developments in massive machine-type communication (mMTC) scenarios have given rise to never-seen requirements, which triggered the Industry 4.0 revolution. The new scenarios bring even more pressure to comply with the reliability and communication security and enable flawless functionality of the critical infrastructure, e.g., smart grid infrastructure. We discuss typical network grid architecture, communication strategies, and methods for building scalable and high-speed data processing and storage platform. This paper focuses on the data transmissions using the sets of standards IEC 60870-6 (ICCP/TASE.2). The main goal is to introduce the TASE.2 traffic generator and the data collection back-end with the implemented load balancing functionality to understand the limits of current protocols used in the smart grids. To this end, the assessment framework enabling generating and collecting TASE.2 communication with long-term data storage providing high availability and load balancing capabilities was developed. The designed proof-of-concept supports complete cryptographic security and allows users to perform the complex testing and verification of the TASE.2 network nodes configuration. Implemented components were tested in a cloud-based Microsoft Azure environment in four geographically separated locations. The findings from the testing indicate the high performance and scalability of the proposed platform, allowing the proposed generator to be also used for high-speed load testing purposes. The load-balancing performance shows the CPU usage of the load-balancer below 15% while processing 5000 messages per second. This makes it possible to achieve up to a 7-fold improvement of performance resulting in processing up to 35,000 messages per second.

On Channel Quantization for Spin-Torque Transfer Magnetic Random Access Memory

As emerging memories such as spin-torque transfer magnetic random access memory (STT-MRAM) suffer from reliability issues caused by process variations and thermal fluctuations, the design of channel quantizer with the minimum number of quantization bits is critical to support effective error correction coding for ensuring high-density and high-speed memory data storage. In this paper, we first propose a quantized channel model for STT-MRAM. Based on the quantized channel model, we derive various information theoretic bounds, including the mutual information, cutoff rate, and the Polyanskiy-Poor-Verdu (PPV) finite-length performance bound. By using these bounds as design criteria, we optimize the quantizer design for the polar-coded STT-MRAM channel. Moreover, we also propose a polar-code-specific quantization design with the successive cancellation decoding algorithm, by using the block error probability bound obtained from density evolution (DE). Simulation results show that all our proposed quantizers generally outperform the prior art greedy merging quantizer. In addition, both the cutoff rate and PPV bound based quantizers outperform the most widely applied mutual information based quantizer for short-length polar codes with 2-bit quantization. Furthermore, the DE quantizer designed specifically for polar codes achieves the best performance among all the proposed quantizers.

Role of initial magnetic disorder: A time-dependent ab initio study of ultrafast demagnetization mechanisms

Despite more than 20 years of development, the underlying physics of the laser-induced demagnetization process is still debated. We present a fast, real-time time-dependent density functional theory (rt-TDDFT) algorithm together with the phenomenological atomic Landau-Lifshitz-Gilbert model to investigate this problem. Our Hamiltonian considers noncollinear magnetic moment, spin-orbit coupling (SOC), electron-electron, electron-phonon, and electron-light interactions. The algorithm for time evolution achieves hundreds of times of speedup enabling calculation of large systems. Our simulations yield a demagnetization rate similar to experiments. We found that (i) the angular momentum flow from light to the system is not essential and the spin Zeeman effect is negligible. (ii) The phonon can play a role but is not essential. (iii) The initial spin disorder and the self-consistent update of the electron-electron interaction play dominant roles and enhance the demagnetization to the experimentally observed rate. The spin disorder connects the electronic structure theory with the phenomenological three-temperature model.

Ring-shaped Racetrack memory based on spin orbit torque driven chiral domain wall motions.

Racetrack memory (RM) has sparked enormous interest thanks to its outstanding potential for low-power, high-density and high-speed data storage. However, since it requires bi-directional domain wall (DW) shifting process for outputting data, the mainstream stripe-shaped concept certainly suffers from the data overflow issue. This geometrical restriction leads to increasing complexity of peripheral circuits or programming as well as undesirable reliability issue. In this work, we propose and study ring-shaped RM, which is based on an alternative mechanism, spin orbit torque (SOT) driven chiral DW motions. Micromagnetic simulations have been carried out to validate its functionality and exhibit its performance advantages. The current flowing through the heavy metal instead of ferromagnetic layer realizes the “end to end” circulation of storage data, which remains all the data in the device even if they are shifted. It blazes a promising path for application of RM in practical memory and logic.

Study on an onboard data storage system for frequency-modulated continuous-wave synthetic aperture radar

The airborne frequency-modulated continuous-wave synthetic aperture radar presents an enormous technical challenge on the design of data storage system due to its characteristics of high-data rate, small size, light weight, and low-power consumption. There are two main problems for the high-speed storage under the miniature requirement. One is the unpredictable response time of the flash translation layer in the CompactFlash card. The other is the relatively long response time of the file system. This paper designs a data storage system in a real-time signal processor. Two techniques called configurable buffer structure and FPFQA (FAT pre- and FDT quasiallocation) are presented to overcome these two problems. The evaluated performance indicates that the size, power consumption, and weight meet the miniature requirement, while the function of the high-speed data storage with approximately 121 MB/s storage speed and real-time file management are realized.

Design of all-optical memory cell using EIT and lasing without inversion phenomena in optical micro ring resonators

The proposed design of the optical memory unit cell contains dual micro ring resonators in which the effect of lasing without inversion (LWI) in three-level nano particles doped over the optical resonators or integrators as the gain segment is used for loss compensation. Also, an on/off phase shifter based on electromagnetically induced transparency (EIT) in three-level quantum dots (QDs) has been used for data reading at requested time. Device minimizing for integrated purposes and high speed data storage are the main advantages of the optical integrator based memory.

High-Speed Transmission and Mass Data Storage Solutions for Large-Area and Arbitrarily Structured Fabrication through Maskless Lithography

This paper presents the implementation aspects and design of high-speed data transmission in laser direct-writing lithography. With a single field programmable gate array (FPGA) chip, mass data storage management, transmission, and synchronization of each part in real-time were implemented. To store a massive amount of data and transmit data with high bandwidth, a serial advanced technology attachment (SATA) intellectual property (IP) was developed on Xilinx Virtex-6 FPGA. In addition, control of laser beam power, collection of status read back data of the lithography laser through an analog-to-digital converter, and synchronization of the positioning signal were implemented on the same FPGA. A data structure for each unit with a unique exposure dose and other necessary information was established. Results showed that the maximum read bandwidth (240 MB/s) and maximum write bandwidth (200 MB/s) of a single solid-state drive conform to the data transmission requirement. The total amount of data meets the requirement of a large-area diffractive element approximately 102 cm2. The throughput has been greatly improved at meters per second or square centimeter per second. And test results showed that data transmission meets the requirement of the experiment.

Remote Data Recorder Design Based on Embedded Linux

Radar, aerospace and wireless communications have a lot of demand for high-speed data acquisition and storage, in these applications, there is a need to control data collection and storage remotely, so researching safe, reliable, real-time remote data recorder is very meaningful. Based on Compact PCI IPC, putting ADC and data acquisition front-end into the chassis, using a dedicated PCI bus interface chip, to transmit data via Compact PCI backplane and record data to high-speed disk array. The platform use embedded Linux operating system to control high-speed and data acquisition. Users can manage data remotely by developing the data acquisition card driver and application software.