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Abstract The conventional computing paradigm struggles to fulfill the rapidly growing demands from emerging applications, especially those for machine intelligence because much of the power and energy is consumed by constant data transfers between logic and memory modules. A new paradigm, called “computational random-access memory (CRAM),” has emerged to address this fundamental limitation. CRAM performs logic operations directly using the memory cells themselves, without having the data ever leave the memory. The energy and performance benefits of CRAM for both conventional and emerging applications have been well established by prior numerical studies. However, there is a lack of experimental demonstration and study of CRAM to evaluate its computational accuracy, which is a realistic and application-critical metric for its technological feasibility and competitiveness. In this work, a CRAM array based on magnetic tunnel junctions (MTJs) is experimentally demonstrated. First, basic memory operations, as well as 2-, 3-, and 5-input logic operations, are studied. Then, a 1-bit full adder with two different designs is demonstrated. Based on the experimental results, a suite of models has been developed to characterize the accuracy of CRAM computation. Scalar addition, multiplication, and matrix multiplication, which are essential building blocks for many conventional and machine intelligence applications, are evaluated and show promising accuracy performance. With the confirmation of MTJ-based CRAM’s accuracy, there is a strong case that this technology will have a significant impact on power- and energy-demanding applications of machine intelligence. 

Spin Torque Oscillators (STOs) are promising solutions in a wide variety of next generation technologies from read-head sensors in high-density magnetic recording technology to neural oscillator units for neuromorphic computing. There are several metrics that can be used to quantify the performance of an STO such as power, quality factor, frequency tunability, etc., most of which are dependent on the design of the STO device itself. Furthermore, determining the most important metric will be contingent on its desired application, meaning that it is crucial to understand how the STOs design parameters influence all aspects of its performance so that its design can be optimized to perform the desired function. In this work, we analyzed spin torque oscillations generated from 20 magnetic tunnel junctions with in-plane anisotropy and patterned into elliptical nano-pillars with a wide range of sizes and aspect ratios. For each device, we acquired 20 to 50 data sets at various bias fields and currents and used power spectral density plots to measure output power, frequency, linewidth, quality factor, and power-to-linewidth ratio for each set. We also analyzed each STOs performance in terms of the bias fields and bias currents required to maximize output power and signal quality as well as the frequency tunability with both field and current. By comparing all of these performance metrics between the 20 STOs tested, we studied the influence of device size and shape on all aspects of STO performance and used correlation coefficients to quantify relative magnitude of these effects. 

Abstract As a promising alternative to the mainstream CoFeB/MgO system with interfacial perpendicular magnetic anisotropy (PMA),L1₀‐FePd and its synthetic antiferromagnet (SAF) structure with large crystalline PMA can support spintronic devices with sufficient thermal stability at sub‐5 nm sizes. However, the compatibility requirement of preparingL1₀‐FePd thin films on Si/SiO₂wafers is still unmet. In this paper, high‐qualityL1₀‐FePd and its SAF on Si/SiO₂wafers are prepared by coating the amorphous SiO₂surface with an MgO(001) seed layer. The preparedL1₀‐FePd single layer and SAF stack are highly (001)‐textured, showing strong PMA, low damping, and sizeable interlayer exchange coupling, respectively. Systematic characterizations, including advanced X‐ray diffraction measurement and atomic resolution‐scanning transmission electron microscopy, are conducted to explain the outstanding performance ofL1₀‐FePd layers. A fully‐epitaxial growth that starts from MgO seed layer, induces the (001) texture ofL1₀‐FePd, and extends through the SAF spacer is observed. This study makes the vision of scalable spintronics more practical.