Wide operating window spin-torque majority gate towards large-scale integration of logic circuits

Spin Torque Majority Gate (STMG) is a logic concept that inherits the non-volatility and the compact size of MRAM devices. In the original STMG design, the operating range was restricted to very small size and anisotropy, due to the exchange-driven character of domain expansion. Here, we propose an improved STMG concept where the domain wall is driven with current. Thus, input switching and domain wall propagation are decoupled, leading to higher energy efficiency and allowing greater technological optimization. To ensure majority operation, pinning sites are introduced. We observe through micromagnetic simulations that the new structure works for all input combinations, regardless of the initial state. Contrary to the original concept, the working condition is only given by threshold and depinning currents. Moreover, cascading is now possible over long distances and fan-out is demonstrated. Therefore, this improved STMG concept is ready to build complete Boolean circuits in absence of external magnetic fields

A flexible InGaAs nanomembrane PhotoFET with tunable responsivities in near- and short-wave IR region for lightweight imaging applications

An ultra-thin (15 nm) InGaAs nanomembrane field-effect phototransistor is transferred entirely from a rigid InP substrate onto a flexible SU-8 on a polydimethylsiloxane substrate. The transferred InGaAs device exhibits wide-band spectral response tunability up to 1.8 µm, from the visible to near-infrared light. Using an epitaxial lift-off process of InGaAs-on-InP MOSHEMT, the transferred device is inverted with a fully exposed channel for photosensitivity enhancement, while retaining three terminals for photocurrent amplification and modulation. The photocurrent can be tuned ∼5 orders over a gate bias range of 6 V. On-state photo-responsivities of 350 A/W to 15 A/W for 0.6 µm and 1.8 µm of light, respectively, is measured, ∼2 × higher than existing silicon and III-V photodetectors. Furthermore, the device shows no electrical performance degradation when flexed down to 10-cm radius, demonstrating suitability for conformal surface sensor applications

Instant-On Spin Torque in Noncollinear Magnetic Tunnel Junctions

© 2018 American Physical Society. Through recent advances, the relevance of magnetic tunnel junctions (MTJs) to the microelectronics industry continues to rise. However, their reversal speed still suffers from incubation delay, a consequence of the collinear magnetization equilibrium states in perpendicularly magnetized MTJs (p-MTJs). We propose to tune the free layer in a Co-Fe-B/MgO/Co-Fe-B stack close to the reorientation transition, aiming to inducing a noncollinearity between the free layer and the reference layer to improve the magnetization reversal speed. Upon varying the layer thickness, the introduction of an in-plane magnetic component is observed in the free layer. Through time-resolved step-response measurements of the conductance, the dynamics are observed to consist of a stochastic delay followed by a repeatable magnetization-reversal pathway. We explore the separation of the measured response into these components and find the power requirements and switching speed to improve over the p-MTJ reference. This is a direct demonstration of the noncollinear improvement pathway, which is appealing for applications where the switching speed and a low energy cost of operation prevail over long-term stability.status: publishe

Instant-On Spin Torque in Noncollinear Magnetic Tunnel Junctions

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