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Synchronization of large spin Hall nano-oscillator (SHNO) arrays is an appealing approach toward ultrafast non-conventional computing. However, interfacing to the array, tuning its individual oscillators and providing built-in memory units remain substantial challenges. Here, we address these challenges using memristive gating of W/CoFeB/MgO/AlO x -based SHNOs. In its high resistance state, the memristor modulates the perpendicular magnetic anisotropy at the CoFeB/MgO interface by the applied electric field. In its low resistance state the memristor adds or subtracts current to the SHNO drive. Both electric field and current control affect the SHNO auto-oscillation mode and frequency, allowing us to reversibly turn on/off mutual synchronization in chains of four SHNOs. We also demonstrate that two individually controlled memristors can be used to tune a four-SHNO chain into differently synchronized states. Memristor gating is therefore an efficient approach to input, tune and store the state of SHNO arrays for non-conventional computing models. This allows versatile non-volatile tuning of the mutual synchronization of chains of up to four oscillators and provides a path toward individual oscillator control in large oscillatory arrays.

The electron spin degree of freedom can provide the functionality of “nonvolatility” in electronic devices. For example, magnetoresistive random access memory (MRAM) is expected as an ideal nonvolatile working memory, with high speed response, high write endurance, and good compatibility with complementary metal-oxide-semiconductor (CMOS) technologies. However, a challenging technical issue is to reduce the operating power. With the present technology, an electrical current is required to control the direction and dynamics of the spin. This consumes high energy when compared with electric-field controlled devices, such as those that are used in the semiconductor industry. A novel approach to overcome this problem is to use the voltage-controlled magnetic anisotropy (VCMA) effect, which draws attention to the development of a new type of MRAM that is controlled by voltage (voltage-torque MRAM). This paper reviews recent progress in experimental demonstrations of the VCMA effect. First, we present an overview of the early experimental observations of the VCMA effect in all-solid state devices, and follow this with an introduction of the concept of the voltage-induced dynamic switching technique. Subsequently, we describe recent progress in understanding of physical origin of the VCMA effect. Finally, new materials research to realize a highly-efficient VCMA effect and the verification of reliable voltage-induced dynamic switching with a low write error rate are introduced, followed by a discussion of the technical challenges that will be encountered in the future development of voltage-torque MRAM.

The combination of electron spin resonance with scanning tunneling microscopy has resulted in a unique surface probe with sub-nm spatial and neV energy resolution. The preparation of a stable magnetic microtip is of central importance, yet, at the same time remains one of the hardest tasks. In this work, we rationalize why creating such microtips by picking up a few iron atoms often results in magnetically stable probes with two distinct magnetic states. By using density functional theory, we show that randomly formed clusters of five iron atoms can exhibit this behavior with magnetic anisotropy barriers of up to 73 meV. We explore the dependence of the magnetic behavior of such clusters on the geometrical arrangement and find a strong correlation between magnetic and geometric anisotropy—the less regular the cluster the higher its magnetic anisotropy barrier. Finally, our work rationalizes the experimental strategy of obtaining stable magnetic microtips.

In pursuing energy-efficient and high-performance nonvolatile magnetic memory devices, this study explores voltage-induced techniques, specifically voltage-controlled magnetic anisotropy (VCMA), as an alternative to current-induced methods, which suffer from Ohmic loss. The perpendicular magnetic anisotropy (PMA) nanomagnet, known for its superior stability and scalability compared to in-plane variants, VCMA switching in PMA system requires an in-plane symmetry breaking field, which limits its practicality for on-chip applications. We investigate field-free VCMA switching utilizing strain from a piezoelectric layer and an exchange bias from an antiferromagnetic material. Using macro-spin simulations based on the Landau-Lifshitz-Gilbert equation, we systematically analyze how the VCMA effect, strain-induced magnetoelastic effect, exchange bias, oxide and free layer thicknesses, and damping constant affect the switching performance of the device. The write error rate (WER) drops drastically from 0.2 (without stress) to 10 - 6 (100 MPa stress), showcasing the effectiveness of our approach. We also find that the damping constant, especially in the 0.01–0.05 range, plays a crucial role in further optimizing the switching performance of the device. This study offers new insights for enhancing magnetic memory technology.

Interlayer exchange-coupled synthetic antiferromagnets (SAFs) have the combined advantages of both high frequency of antiferromagnets and easy detection of ferromagnets. Here, magnetic excitations are investigated by theoretical analysis and micromagnetic simulations in SAFs that consist of two identical ferromagnetic layers with perpendicular magnetic anisotropy. Different from the common in-phase acoustic mode and out-of-phase optic mode, linearly or circularly polarized spin wave modes can be excited at zero bias field by using different types of microwave magnetic fields. Once a bias magnetic field is applied along the easy-axis, left-handed (LH) and right-handed (RH) polarization modes are observed, and the resonance frequency of RH (LH) mode of the SAFs increases (decreases) linearly with the increase of bias magnetic fields until a critical spin-flop field is reached, which is in accordance with collinear antiferromagnets with easy-axis anisotropy. These simulation results agree with the theoretical derivation and provide fundamental insight into the nature of dynamic properties of the perpendicularly magnetized SAFs, which may provide new prospects for spintronic applications.

Fe-based amorphous and nanocrystalline alloys, such as FINEMET and its improved variants, are highly valued as green energy-saving materials due to their unique magnetic properties, including high permeability, low coercivity, and near-zero saturation magnetostriction. These characteristics have enabled their extensive use in power electronics and information technology. However, the full potential of these alloys remains unfulfilled due to insufficient understanding of their stress sensitivity. This study focuses on the development history, heat treatment, annealing processes, chemical composition, and underlying mechanisms of Fe-based amorphous and nanocrystalline alloys, aiming to provide insights into stress-induced magnetic anisotropy and guide the development of greener and more efficient soft magnetic materials.

The precise manipulation of magnetic solitons remains a challenge and is considered a crucial process in magnetic storage. In this paper, we investigate the control of velocity and spatial manipulation of magnetic solitons using the voltage-controlled magnetic anisotropy effect. A long-wave model, known as the generalized derivative nonlinear Schrödinger (GDNLS) equation, is developed to describe the dynamics of magnetic solitons in an anisotropic ferromagnetic nanowire. By constructing the Lax pair for the GDNLS equation, we obtain the exact solutions including magnetic dark solitons, anti-dark solitons, and periodic solutions. Moreover, we propose two approaches to manipulate magnetic solitons: direct voltage application and inhomogeneous insulation layer design. Numerically results show the direct modulation of soliton velocity by a constant voltage, while time-varying voltage induces periodic oscillations. Investigation of Gaussian-type defects reveals soliton being trapped beyond a critical defect depth. These results provide a theoretical basis for future applications in magnetic soliton-based memory devices.

Perpendicular exchange bias (PEB) is highly desirable for the development of advanced nanoscale spintronics devices. The attainment of conventional PEB typically involves a field-cooling process through the Néel temperature of antiferromagnetic materials. In this study, we demonstrated the realization of spontaneous PEB (SPEB) in IrMn/[Co/Pt] 3 multilayers utilizing isothermal crystallization of IrMn at room temperature (RT). And the SPEB generated isothermally at IrMn/Co interface does not destroy the perpendicular magnetic anisotropy of the multilayers. The magnetic domains of the multilayers captured by Kerr microscopy after different magnetization time also indicate the generation of SPEB. The magnitude of SPEB can be controllable by varying the isothermal magnetization time and the annealing temperature of IrMn. The relationship between magnetization waiting time and SPEB reveals that even slight isothermal crystallization can generate substantial SPEB. Our results provide an alternative approach to isothermally generate PEB in IrMn/[Co/Pt] 3 multilayers at RT.

As the conventional von Neumann architecture meets critical limitations of data transfer bandwidth and energy consumption, perpendicular magnetic anisotropy magnetic tunnel junction based processing-in-memory paradigm attracts extensive attention as a promising substitute thanks to its non-volatility, low-power switching, fast access and infinite endurance. In this work, we propose and experimentally demonstrate a new spintronic implication logic gate that consists of two parallel perpendicular magnetic anisotropy magnetic tunnel junctions with different diameters. Material implication and furthermore NAND logic functions are implemented by all electrically-controlled operations. The reliability of this structure is verified, especially in sub-20 nm node, which shows great potential for large-density processing-in-memory applications.

We demonstrate sputtering power dependent magnetic compensation temperatures, perpendicular magnetic anisotropy, and magnetocaloric properties of ferrimagnetic Tb 30 (Fe 7 Co 63 ) amorphous thin films. The magnetic compensation temperature rises from 224 K to 407 K when sputtering power increases from 50 W to 100 W. Magnetization, and Hall effect measurements confirm the presence of perpendicular magnetic anisotropy in these films. The out-of-plane magneto-optic kerr effect (MOKE) measurements reveal that the films deposited with 50 W, 70 W, and 80 W exhibit good perpendicular magnetic anisotropy with a squareness ratio of around 1. The effective anisotropy constant (K u ) increases with increase with sputtering power and reaches a maximum value of 1.29 × 10 6 erg/cm 3 at 100 W. Magnetocaloric investigations across a wide temperature range using a ± 15kOe magnetic field show a substantial increment in magnetic entropy change. The magnetic entropy change is noticed around 0.25 J/kgK for films deposited with 100 W. These findings emphasize the significance of sputtering power in controlling the magnetic properties of amorphous ferrimagnetic thin films for spintronic and magnetocaloric applications.