Collective Spin-Wave Dynamics in Gyroid Ferromagnetic Nanostructures.

Expanding upon the burgeoning discipline of magnonics, this research elucidates the intricate dynamics of spin waves (SWs) within three-dimensional nanoenvironments. It marks a shift from traditionally used planar systems to exploration of magnetization configurations and the resulting dynamics within 3D nanostructures. This study deploys micromagnetic simulations alongside ferromagnetic resonance measurements to scrutinize magnetic gyroids, periodic chiral configurations composed of chiral triple junctions with a period in nanoscale. Our findings uncover distinctive attributes intrinsic to the gyroid network, most notably the localization of collective SW excitations and the sensitivity of the gyroid's ferromagnetic response to the orientation of the static magnetic field, a correlation closely tied to the crystallographic alignment of the structure. Furthermore, we show that for the ferromagnetic resonance, multidomain gyroid films can be treated as a magnonic material with effective magnetization scaled by its filling factor. The implications of our research carry the potential for practical uses such as an effective, metamaterial-like substitute for ferromagnetic parts and lay the groundwork for radio frequency filters. The growing areas of 3D magnonics and spintronics present exciting opportunities to investigate and utilize gyroid nanostructures for signal processing purposes.

CMOS plus stochastic nanomagnets enabling heterogeneous computers for probabilistic inference and learning.

Extending Moore's law by augmenting complementary-metal-oxide semiconductor (CMOS) transistors with emerging nanotechnologies (X) has become increasingly important. One important class of problems involve sampling-based Monte Carlo algorithms used in probabilistic machine learning, optimization, and quantum simulation. Here, we combine stochastic magnetic tunnel junction (sMTJ)-based probabilistic bits (p-bits) with Field Programmable Gate Arrays (FPGA) to create an energy-efficient CMOS + X (X = sMTJ) prototype. This setup shows how asynchronously driven CMOS circuits controlled by sMTJs can perform probabilistic inference and learning by leveraging the algorithmic update-order-invariance of Gibbs sampling. We show how the stochasticity of sMTJs can augment low-quality random number generators (RNG). Detailed transistor-level comparisons reveal that sMTJ-based p-bits can replace up to 10,000 CMOS transistors while dissipating two orders of magnitude less energy. Integrated versions of our approach can advance probabilistic computing involving deep Boltzmann machines and other energy-based learning algorithms with extremely high throughput and energy efficiency.

Handedness anomaly in a non-collinear antiferromagnet under spin-orbit torque.

Non-collinear antiferromagnets are an emerging family of spintronic materials because they not only possess the general advantages of antiferromagnets but also enable more advanced functionalities. Recently, in an intriguing non-collinear antiferromagnet Mn3Sn, where the octupole moment is defined as the collective magnetic order parameter, spin-orbit torque (SOT) switching has been achieved in seemingly the same protocol as in ferromagnets. Nevertheless, it is fundamentally important to explore the unknown octupole moment dynamics and contrast it with the magnetization vector of ferromagnets. Here we report a handedness anomaly in the SOT-driven dynamics of Mn3Sn: when spin current is injected, the octupole moment rotates in the opposite direction to the individual moments, leading to a SOT switching polarity distinct from ferromagnets. By using second-harmonic and d.c. magnetometry, we track the SOT effect onto the octupole moment during its rotation and reveal that the handedness anomaly stems from the interactions between the injected spin and the unique chiral-spin structure of Mn3Sn. We further establish the torque balancing equation of the magnetic octupole moment and quantify the SOT efficiency. Our finding provides a guideline for understanding and implementing the electrical manipulation of non-collinear antiferromagnets, which in nature differs from the well-established collinear magnets.

Coherent antiferromagnetic spintronics.

Antiferromagnets have attracted extensive interest as a material platform in spintronics. So far, antiferromagnet-enabled spin-orbitronics, spin-transfer electronics and spin caloritronics have formed the bases of antiferromagnetic spintronics. Spin transport and manipulation based on coherent antiferromagnetic dynamics have recently emerged, pushing the developing field of antiferromagnetic spintronics towards a new stage distinguished by the features of spin coherence. In this Review, we categorize and analyse the critical effects that harness the coherence of antiferromagnets for spintronic applications, including spin pumping from monochromatic antiferromagnetic magnons, spin transmission via phase-correlated antiferromagnetic magnons, electrically induced spin rotation and ultrafast spin-orbit effects in antiferromagnets. We also discuss future opportunities in research and applications stimulated by the principles, materials and phenomena of coherent antiferromagnetic spintronics.

Relapse-Free Course in Nearly Half of Crohn's Disease Patients With Infliximab and Plant-Based Diet as First-Line Therapy: A Single-Group Trial.

Introduction Incorporation of a plant-based diet was effective in both induction and short-term relapse prevention in Crohn's disease. Ten-year long-term relapse-free rates in Crohn's disease are around 10% to 23%. Objective We investigated whether infliximab and plant-based diet as first-line therapy enhance the long-term relapse-free rate in patients with Crohn's disease. Methods This single-group, prospective study was performed in tertiary hospitals in Japan. Remission was induced in 24 consecutive newly diagnosed adult patients with Crohn's disease during hospitalization via 3 standard infliximab infusions together with a plant-based diet. Patients were instructed to continue the diet after discharge. Scheduled maintenance infliximab infusion was not used. The primary endpoint was relapse, which was defined as the appearance of symptoms resulting in the alteration of therapeutic modality. The secondary endpoints were C-reactive protein level, plant-based diet score, and surgery. Results The median follow-up period was 8.6 years. Thirteen cases were relapse-free. The relapse-free rate evaluated by Kaplan-Meier survival analysis at 1, 2, 3, and 4 years was 79%, 66%, 57%, and 52%, respectively. There was no further reduction afterward up to 10 years. The relapse-free rate with normal C-reactive protein levels at 1 to 2 and 3 to 10 years was 57% and 52%, respectively. The plant-based diet score at 20 months and 5 years was significantly higher relative to baseline (p < 0.0001). Surgical rates at 5 and 10 years were 12% and 19%, respectively. Conclusions Infliximab and plant-based diet as first-line therapy created an unprecedented relapse-free course in nearly half of patients with Crohn's disease.

Local bifurcation with spin-transfer torque in superparamagnetic tunnel junctions.

Modulation of the energy landscape by external perturbations governs various thermally-activated phenomena, described by the Arrhenius law. Thermal fluctuation of nanoscale magnetic tunnel junctions with spin-transfer torque (STT) shows promise for unconventional computing, whereas its rigorous representation, based on the Néel-Arrhenius law, has been controversial. In particular, the exponents for thermally-activated switching rate therein, have been inaccessible with conventional thermally-stable nanomagnets with decade-long retention time. Here we approach the Néel-Arrhenius law with STT utilising superparamagnetic tunnel junctions that have high sensitivity to external perturbations and determine the exponents through several independent measurements including homodyne-detected ferromagnetic resonance, nanosecond STT switching, and random telegraph noise. Furthermore, we show that the results are comprehensively described by a concept of local bifurcation observed in various physical systems. The findings demonstrate the capability of superparamagnetic tunnel junction as a useful tester for statistical physics as well as sophisticated engineering of probabilistic computing hardware with a rigorous mathematical foundation.

Generalized scaling of spin qubit coherence in over 12,000 host materials.

SignificanceAtomic defects in solid-state materials are promising candidates as quantum bits, or qubits. New materials are actively being investigated as hosts for new defect qubits; however, there are no unifying guidelines that can quantitatively predict qubit performance in a new material. One of the most critical property of qubits is their quantum coherence. While cluster correlation expansion (CCE) techniques are useful to simulate the coherence of electron spins in defects, they are computationally expensive to investigate broad classes of stable materials. Using CCE simulations, we reveal a general scaling relation between the electron spin coherence time and the properties of qubit host materials that enables rapid and quantitative exploration of new materials hosting spin defects.

Memristive control of mutual spin Hall nano-oscillator synchronization for neuromorphic computing.

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/AlOx-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.

Unconventional Hall effect and its variation with Co-doping in van der Waals Fe3GeTe2.

Two-dimensional (2D) van der Waals (vdW) magnetic materials have attracted a lot of attention owing to the stabilization of long range magnetic order down to atomic dimensions, and the prospect of novel spintronic devices with unique functionalities. The clarification of the magnetoresistive properties and its correlation to the underlying magnetic configurations is essential for 2D vdW-based spintronic devices. Here, the effect of Co-doping on the magnetic and magnetotransport properties of Fe3GeTe2 have been investigated. Magnetotransport measurements reveal an unusual Hall effect behavior whose strength was considerably modified by Co-doping and attributed to arise from the underlying complicated spin textures. The present results provide a clue to tailoring of the underlying interactions necessary for the realization of a variety of unconventional spin textures for 2D vdW FM-based spintronics.

Chiral-spin rotation of non-collinear antiferromagnet by spin-orbit torque.

Electrical manipulation of magnetic materials by current-induced spin torque constitutes the basis of spintronics. Here, we show an unconventional response to spin-orbit torque of a non-collinear antiferromagnet Mn3Sn, which has attracted attention owing to its large anomalous Hall effect despite a vanishingly small net magnetization. In epitaxial heavy-metal/Mn3Sn heterostructures, we observe a characteristic fluctuation of the Hall resistance under the application of electric current. This observation is explained by a rotation of the chiral-spin structure of Mn3Sn driven by spin-orbit torque. We find that the variation of the magnitude of anomalous Hall effect fluctuation with sample size correlates with the number of magnetic domains in the Mn3Sn layer. In addition, the dependence of the critical current on Mn3Sn layer thickness reveals that spin-orbit torque generated by small current densities, below 20 MA cm-2, effectively acts on the chiral-spin structure even in Mn3Sn layers that are thicker than 20 nm. The results provide additional pathways for electrical manipulation of magnetic materials.

Electrically connected spin-torque oscillators array for 2.4 GHz WiFi band transmission and energy harvesting.

The mutual synchronization of spin-torque oscillators (STOs) is critical for communication, energy harvesting and neuromorphic applications. Short range magnetic coupling-based synchronization has spatial restrictions (few µm), whereas the long-range electrical synchronization using vortex STOs has limited frequency responses in hundreds MHz (<500 MHz), restricting them for on-chip GHz-range applications. Here, we demonstrate electrical synchronization of four non-vortex uniformly-magnetized STOs using a single common current source in both parallel and series configurations at 2.4 GHz band, resolving the frequency-area quandary for designing STO based on-chip communication systems. Under injection locking, synchronized STOs demonstrate an excellent time-domain stability and substantially improved phase noise performance. By integrating the electrically connected eight STOs, we demonstrate the battery-free energy-harvesting system by utilizing the wireless radio-frequency energy to power electronic devices such as LEDs. Our results highlight the significance of electrical topology (series vs. parallel) while designing an on-chip STOs system.

Stepwise Treatment With Plant-Based Diet and Medication for Patient With Mild Ulcerative Colitis.

INTRODUCTION: We regard inflammatory bowel disease as a lifestyle disease mainly mediated by a westernized diet. We developed a plant-based diet (PBD) to counter the westernized diet. PBD can induce remission without medication in a subset of mild cases of ulcerative colitis. Medication is provided when induction of remission is not achieved solely with PBD. We describe such a case in this report. CASE PRESENTATION: A 34-year-old woman visited us in October 2016 with a complaint of loose stool for nearly 5 years. Laboratory examination revealed mild abnormalities including elevation of C-reactive protein (CRP). Ulcerative colitis was diagnosed due to diffuse colonic inflammation and pathological findings consistent with ulcerative colitis. She was admitted for educational hospitalization for 19 days in the middle of November, during which PBD was provided. A few days after admission, her stool became normal. CRP concentration decreased to within the normal range. However, colonoscopy on discharge showed minimum improvement. Thereafter, CRP was abnormal on three successive occasions, and her stool alternated between normal and loose. Sulfasalazine was initiated at the end of March 2017. Thereafter, her stool was normally formed, and CRP decreased to normal. Endoscopic remission was confirmed in August. Her PBD score, which evaluates adherence to PBD, was 8 before admission, and 37 and 16 at 7 and 21 months after discharge, respectively. CONCLUSION: Medication was administered when restoration of a healthy dietary lifestyle was insufficient to induce remission. Our stepwise treatment makes the shift from one-size-fits-all medication toward medication to the right patient. REGISTRATION: http://www.umin.ac.jp UMIN000019061.

Energy Efficient Control of Ultrafast Spin Current to Induce Single Femtosecond Pulse Switching of a Ferromagnet.

New methods to induce magnetization switching in a thin ferromagnetic material using femtosecond laser pulses without the assistance of an applied external magnetic field have recently attracted a lot of interest. It has been shown that by optically triggering the reversal of the magnetization in a GdFeCo layer, the magnetization of a nearby ferromagnetic thin film can also be reversed via spin currents originating in the GdFeCo layer. Here, using a similar structure, it is shown that the magnetization reversal of the GdFeCo is not required in order to reverse the magnetization of the ferromagnetic thin film. This switching is attributed to the ultrafast spin current and can be generated by the GdFeCo demagnetization. A larger energy efficiency of the ferromagnetic layer single pulse switching is obtained for a GdFeCo with a larger Gd concentration. Those ultrafast and energy efficient switchings observed in such spintronic devices open a new path toward ultrafast and energy efficient magnetic memories.

Engineering Single-Shot All-Optical Switching of Ferromagnetic Materials.

Since it was recently demonstrated in a spin-valve structure, magnetization reversal of a ferromagnetic layer using a single ultrashort optical pulse has attracted attention for future ultrafast and energy-efficient magnetic storage or memory devices. However, the mechanism and the role of the magnetic properties of the ferromagnet as well as the time scale of the magnetization switching are not understood. Here, we investigate single-shot all-optical magnetization switching in a GdFeCo/Cu/[CoxNi1-x/Pt] spin-valve structure. We demonstrate that the threshold fluence for switching both the GdFeCo and the ferromagnetic layer depends on the laser pulse duration and the thickness and the Curie temperature of the ferromagnetic layer. We are able to explain most of the experimental results using a phenomenological model. This work provides a way to engineer ferromagnetic materials for energy efficient single-shot all-optical magnetization switching.

Giant voltage-controlled modulation of spin Hall nano-oscillator damping.

Spin Hall nano-oscillators (SHNOs) are emerging spintronic devices for microwave signal generation and oscillator-based neuromorphic computing combining nano-scale footprint, fast and ultra-wide microwave frequency tunability, CMOS compatibility, and strong non-linear properties providing robust large-scale mutual synchronization in chains and two-dimensional arrays. While SHNOs can be tuned via magnetic fields and the drive current, neither approach is conducive to individual SHNO control in large arrays. Here, we demonstrate electrically gated W/CoFeB/MgO nano-constrictions in which the voltage-dependent perpendicular magnetic anisotropy tunes the frequency and, thanks to nano-constriction geometry, drastically modifies the spin-wave localization in the constriction region resulting in a giant 42% variation of the effective damping over four volts. As a consequence, the SHNO threshold current can be strongly tuned. Our demonstration adds key functionality to nano-constriction SHNOs and paves the way for energy-efficient control of individual oscillators in SHNO chains and arrays for neuromorphic computing.

Visualizing Magnetic Structure in 3D Nanoscale Ni-Fe Gyroid Networks.

Arrays of interacting 2D nanomagnets display unprecedented electromagnetic properties via collective effects, demonstrated in artificial spin ices and magnonic crystals. Progress toward 3D magnetic metamaterials is hampered by two challenges: fabricating 3D structures near intrinsic magnetic length scales (sub-100 nm) and visualizing their magnetic configurations. Here, we fabricate and measure nanoscale magnetic gyroids, periodic chiral networks comprising nanowire-like struts forming three-connected vertices. Via block copolymer templating, we produce Ni75Fe25 single-gyroid and double-gyroid (an inversion pair of single-gyroids) nanostructures with a 42 nm unit cell and 11 nm diameter struts, comparable to the exchange length in Ni-Fe. We visualize their magnetization distributions via off-axis electron holography with nanometer spatial resolution and interpret the patterns using finite-element micromagnetic simulations. Our results suggest an intricate, frustrated remanent state which is ferromagnetic but without a unique equilibrium configuration, opening new possibilities for collective phenomena in magnetism, including 3D magnonic crystals and unconventional computing.

High Remission Rate with Infliximab and Plant-Based Diet as First-Line (IPF) Therapy for Severe Ulcerative Colitis: Single-Group Trial.

INTRODUCTION: About one-third of patients with severe ulcerative colitis (UC) do not respond to corticosteroid therapy and receive rescue therapy with infliximab or cyclosporine. Up to 20% of such patients fail to respond to rescue therapy and undergo colectomy. OBJECTIVE: We investigated the outcomes of infliximab and a plant-based diet (PBD) as first-line therapy for severe UC. METHODS: Patients with severe UC defined by the Truelove and Witts criteria were admitted and given standard induction therapy with infliximab (5.0 mg/kg-7.5 mg/kg) at 0, 2, and 6 weeks. Additionally, they received a PBD. The primary endpoint was remission or colectomy in the induction phase and 1 year after discharge. Secondary endpoints were changes in inflammatory markers in the induction phase and the PBD score at baseline and follow-up. A higher PBD score indicates greater adherence to a PBD. RESULTS: Infliximab and PBD as first-line therapy was administered in 17 cases. The remission rate was 76% (13/17), and the colectomy rate was 6% (1/17) in the induction phase. C-reactive protein values and the erythrocyte sedimentation rate significantly decreased at week 6 from 9.42 mg/dL to 0.33 mg/dL and from 59 to 17 mm/h, respectively (p < 0.0001). At 1-year follow-up, the cumulative relapse rate was 25%, and there were no additional colectomy cases. Mean PBD scores of 27.7 at 1 year and 23.8 at 4 years were significantly higher than baseline scores of 8.3 and 9.9, respectively (p < 0.0001 and p = 0.0391). CONCLUSION: This new first-line therapy for severe UC demonstrated a higher remission rate and lower colectomy rate than with the current modality.

Formation and current-induced motion of synthetic antiferromagnetic skyrmion bubbles.

Skyrmion, a topologically-protected soliton, is known to emerge via electron spin in various magnetic materials. The magnetic skyrmion can be driven by low current density and has a potential to be stabilized in nanoscale, offering new directions of spintronics. However, there remain some fundamental issues in widely-studied ferromagnetic systems, which include a difficulty to realize stable ultrasmall skyrmions at room temperature, presence of the skyrmion Hall effect, and limitation of velocity owing to the topological charge. Here we show skyrmion bubbles in a synthetic antiferromagnetic coupled multilayer that are free from the above issues. Additive Dzyaloshinskii-Moriya interaction and spin-orbit torque (SOT) of the tailored stack allow stable skyrmion bubbles at room temperature, significantly smaller threshold current density or higher speed for motion, and negligible skyrmion Hall effect, with a potential to be scaled down to nanometer dimensions. The results offer a promising pathway toward nanoscale and energy-efficient skyrmion-based devices.

Integer factorization using stochastic magnetic tunnel junctions.

Conventional computers operate deterministically using strings of zeros and ones called bits to represent information in binary code. Despite the evolution of conventional computers into sophisticated machines, there are many classes of problems that they cannot efficiently address, including inference, invertible logic, sampling and optimization, leading to considerable interest in alternative computing schemes. Quantum computing, which uses qubits to represent a superposition of 0 and 1, is expected to perform these tasks efficiently1-3. However, decoherence and the current requirement for cryogenic operation4, as well as the limited many-body interactions that can be implemented, pose considerable challenges. Probabilistic computing1,5-7 is another unconventional computation scheme that shares similar concepts with quantum computing but is not limited by the above challenges. The key role is played by a probabilistic bit (a p-bit)-a robust, classical entity fluctuating in time between 0 and 1, which interacts with other p-bits in the same system using principles inspired by neural networks8. Here we present a proof-of-concept experiment for probabilistic computing using spintronics technology, and demonstrate integer factorization, an illustrative example of the optimization class of problems addressed by adiabatic9 and gated2 quantum computing. Nanoscale magnetic tunnel junctions showing stochastic behaviour are developed by modifying market-ready magnetoresistive random-access memory technology10,11 and are used to implement three-terminal p-bits that operate at room temperature. The p-bits are electrically connected to form a functional asynchronous network, to which a modified adiabatic quantum computing algorithm that implements three- and four-body interactions is applied. Factorization of integers up to 945 is demonstrated with this rudimentary asynchronous probabilistic computer using eight correlated p-bits, and the results show good agreement with theoretical predictions, thus providing a potentially scalable hardware approach to the difficult problems of optimization and sampling.

Relapse Prevention by Plant-Based Diet Incorporated into Induction Therapy for Ulcerative Colitis: A Single-Group Trial.

CONTEXT: No known previous study has focused on plant-based diet (PBD) to prevent relapse of ulcerative colitis (UC) except our previous educational hospitalization study. OBJECTIVE: To describe the relapse rate in a large case series of UC after incorporation of PBD into induction therapy. DESIGN: All patients with UC between 2003 and 2017 were admitted for induction therapy. Patients receiving educational hospitalization or treated with infliximab were excluded. A lacto-ovo-semivegetarian diet (PBD) together with medication prescribed according to UC guidelines was provided during hospitalization. MAIN OUTCOME MEASURES: The primary endpoint was relapse during follow-up. The secondary endpoint was change over time in the plant-based diet score (PBDS), which evaluated adherence to the PBD. RESULTS: Ninety-two cases were studied, of which 51 were initial episodes and 41 were relapses. Cases varied in severity (31 mild, 48 moderate, 13 severe) and extent (15 proctitis, 22 left-sided colitis, 55 extensive colitis). More severe cases existed among the relapse cases than among the initial episode cases. Cumulative relapse rates at 1- and 5-year follow-up (Kaplan-Meier analysis) were 14% and 27%, respectively, for the initial episode cases, and 36% and 53%, respectively, for relapse cases. At long-term follow-up (6 years 4 months), PBDS was significantly higher than baseline PBDS (p < 0.0001). CONCLUSION: Relapse rates in UC after induction therapy with PBD were far lower than those previously reported with conventional therapy. Adherence to PBD was significantly higher than baseline even at 6-year follow-up. We conclude PBD is effective for preventing UC relapse.(Study identification no.: UMIN000019061: Registration: www.umin.ac.jp).