In this paper, a 3-terminal spin-transfer torque nano-oscillator (STNO) is studied using the concurrent spin injection of a spin-polarized tunneling current and a spin Hall current exciting the free layer into dynamic regimes beyond what is achieved by each individual mechanism. The pure spin injection is capable of inducing oscillations in the absence of charge currents effectively reducing the critical tunneling current to zero. This reduction of the critical charge currents can improve the endurance of both STNOs and non-volatile magnetic memories (MRAM) devices.It is shown that the system response can be described in terms of an injected spin current density Js which results from the contribution of both spin injection mechanisms, with the tunneling current polarization p and the spin Hall angle θ acting as key parameters determining the efficiency of each injection mechanism. The experimental data exhibits an excellent agreement with this model which can be used to quantitatively predict the critical points (Js = -2.26±0.09 × 10 9 ħ/e A/m 2 ) and the oscillation amplitude as a function of the input currents. In addition, the fitting of the data also allows an independent confirmation of the values estimated for the spin Hall angle and tunneling current polarization as well as the extraction of the damping α = 0.01 and non-linear damping Q = 3.8±0.3 parameters. Index Terms-Spin Hall Effect, Spin Torque Nano-oscillator, Magnetic Tunnel Junctions.Recent reports demonstrate that the Spin Hall Effect (SHE) can be used to generate pure spin currents, capable of exerting a spin transfer torque (STT) that induces oscillations in a ferromagnetic layer 1,2 . This pure spin current is created by a charge current in a nonmagnetic material with strong spin-orbit coupling where up and down spins are scattered in opposite directions resulting in a spin current orthogonal to the electrical current 2-6 . A central challenge is to quantify the efficiency of the charge current to spin current conversion, which results from the difficulty of measuring spin currents. The spin-orbit material is characterized by a material property called the spin Hall angle, which quantifies the ratio between the generated spin current density ( Hall spin s J ) at an applied charge current density ( Hall spin c J ). The spin Hall angle is expressed as   Hall spin c Hall spin s J J e    with the charge of the electron e and the reduced Plank constant ħ ensuring dimensional consistency. Several techniques have been used to quantify θ of transition metals such as Au, Pd, Pt, Ta, and W. A particularly interesting material is Ta since it is a typical cap and seed layer in magnetic tunnel junction (MTJ) devices and in direct contact with the ferromagnetic free layer. The reported θ values of Ta are in a wide range of 1.4% < θ < 15%, primarily due to dependences on the crystalline phase 6-9 . e J J J J J  stripe of Hall spin c J = -73 × 10 9 A/m 2 injects an equivalent Js into the free layer. At this value the spin Hall effect should excite oscill...

Reported steady-state microwave emission in magnetic tunnel junction (MTJ)-based spin transfer torque nano-oscillators (STNOs) relies mostly on very thin insulating barriers [resulting in a resistance × area product (R × A) of ~1 Ωμm2] that can sustain large current densities and thus trigger large orbit magnetic dynamics. Apart from the low R × A requirement, the role of the tunnel barrier in the dynamics has so far been largely overlooked, in comparison to the magnetic configuration of STNOs. In this report, STNOs with an in-plane magnetized homogeneous free layer configuration are used to probe the role of the tunnel barrier in the dynamics. In this type of STNOs, the RF modes are in the GHz region with integrated matched output power (P out) in the range of 1–40 nW. Here, P out values up to 200 nW are reported using thicker insulating barriers for junctions with R × A values ranging from 7.5 to 12.5 Ωμm2, without compromising the ability to trigger self-sustained oscillations and without any noticeable degradation of the signal linewidth (Γ). Furthermore, a decrease of two orders of magnitude in the critical current density for spin transfer torque induced dynamics (J STT) was observed, without any further change in the magnetic configuration.

In this paper the perpendicular magnetic anisotropy (PMA) is tailored by changing the thickness of the free layer with the objective of producing MTJ nano-pillars with smooth linear resistance dependence with both in-plane magnetic field and DC bias. We furthermore demonstrate how this linear bias dependence can be used to create a zero-threshold broadband voltage rectifier, a feature which is important for rectification in wireless charging and energy harvesting applications. By carefully balancing the amount of PMA acting in the free layer the measured RF to DC voltage conversion efficiency can be made as large as 11%.

Dealing with big data, especially the videos and images, is the biggest challenge of existing Von-Neumann machines while the human brain, benefiting from its massive parallel structure, is capable of processing the images and videos in a fraction of second. The most promising solution, which has been recently researched widely, is brain-inspired computers, so-called neuromorphic computing systems (NCS). The NCS overcomes the limitation of the word-at-a-time thinking of conventional computers benefiting from massive parallelism for data processing, similar to the brain. Recently, spintronic-based NCSs have shown the potential of implementation of low-power highdensity NCSs, where neurons are implemented using magnetic tunnel junctions (MTJs) or spin torque nano-oscillators (STNOs) and memristors are used to mimic synaptic functionality. Although using STNOs as neuron requires lower energy in comparison to the MTJs, still there is a huge gap between the power consumption of spintronic-based NCSs and the brain due to high bias current needed for starting the oscillation with a detectable output power. In this manuscript, we propose a spintronic-based NCS (196 × 10) proof-of-concept where the power consumption of the NCS is reduced by assisting the STNO oscillation through a microwatt nanosecond laser pulse. The experimental results show the power consumption of the STNOs in the designed NCS is reduced by 55.3% by heating up the STNOs to 100 • C. Moreover, the average power consumption of spintronic layer (STNOs and memristor array) is decreased by 54.9% at 100 • C compared with room temperature. The total power consumption of the proposed laser assisted STNO-based NCS (LAO-NCS) at 100 • C is improved by 40% in comparison to a typical STNO-based NCS at room temperature. Finally, the energy consumption of the LAO-NCA at 100 • C is expected to reduce by 86% compared with a typical STNO-based NCS at the room temperature.