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Large induced magnetization is observed in rhombohedral-like BiFeO3 (RBFO) when grown on a ferromagnetic La2/3Sr1/3MnO3 layer. This magnetization survives up to room temperature and is strongly influenced by the deposition conditions and crystallographic phase of BiFeO3. The magnetization in RBFO is induced by the Fe–O–Mn ferromagnetic (FM) superexchange (SE) interaction, after a strong hybridization between Fe and Mn orbitals mediate through oxygen orbitals, which enhances the spin canting in a BFO layer near the interface. The reduction in the magnetization of BFO due to change in its growth conditions is caused by the altered oxygen content in the interfacial region, which has a direct impact on the FM SE Fe–O–Mn coupling at the interface. In marked contrast, the induced magnetization in the super-tetragonal phase (TBFO) of BFO, in which the canting of Fe spins is forbidden by the symmetry, shows a comparatively very small moment, which vanishes below the room temperature (∼200 K). We propose that the ferromagnetic ordering induced in TBFO is limited to the adjoined section only, whereas it extended to a certain degree of bulk in RBFO. A spin-glass like state is also observed in BiFeO3/La2/3Sr1/3MnO3 heterostructure with irreversible temperature ∼100 K. [ABSTRACT FROM AUTHOR]

The effects of various thicknesses of FePt insert layer on the microstructure and magnetic properties of FePt-ZrO2-C thin films have been investigated. It is found that with inserting 0.4 nm FePt films between the TiON intermediate layer and FePt-ZrO2-C layer, the perpendicular anisotropy indicated by Hc⊥/Hc//ratio would increase from 4 to 13.1, suggesting the perpendicular anisotropy could be improved a lot with using FePt insert layer. Simultaneously, the FePt grains of FePt-ZrO2-C thin films maintained columnar structure and the grain isolation could also be improved in a certain degree. With further increase of the FePt insert layer thickness, although the perpendicular anisotropy was still larger than that without FePt insert layer, the grain size of the FePt-ZrO2-C films would increase and the isolation would be deteriorated. [ABSTRACT FROM AUTHOR]

Heteroepitaxial film growth is crucial for magnetic and electronic devices. In this work, we reported the effects of the large lattice mismatch and film thickness on the epitaxial growth and magnetic properties of FePt films on Zr x Ti 1−x N (0 0 1) intermediate layer. FePt films with different thickness were deposited on ZrTiN intermediate layers with various doping concentration of TiN in ZrN. The increase in doping concentration of TiN caused a decrease in the lattice parameters of ZrTiN intermediate layer. It was found that (0 0 1) epitaxy of FePt 10 nm films was only achieved on ZrTiN intermediate layer when the TiN composition was ≥25 vol%, while (0 0 1) texture of 5 nm films was achieved on ZrTiN intermediate layer with a minimum of 50 vol% TiN composition. The in-plane lattice constants of FePt and Zr 0.70 Ti 0.30 N (25 vol% TiN) were 3.870 Å and 4.476 Å, respectively, which resulted in a lattice mismatch as large as 15.7%. These large lattice mismatch heterostructures adopted 7/6 domain matching epitaxy. The magneto-crystalline anisotropy of FePt films was improved with the increase in lattice mismatch. Intrinsic magnetic properties were extrapolated for FePt (30 nm)/Zr 0.70 Ti 0.30 N (30 nm)/TaN (30 nm)/MgO, and the M s (0 K) and K 1 (0 K) were 1042 emu/cc and 5.10 × 10 7 erg/cc, respectively, which is comparable to that of bulk L1 0 FePt. [ABSTRACT FROM AUTHOR]

• Binary synapse based on the deterministic switching of the magnetization states by encoding high and low resistance states. • Sigmoid neuron based on the stochastic switching probability of the magnetization in the free layer. • All-spin BWN based on the multi-functional nanoscale SOT devices achieves ∼81.73 % recognition accuracy on the CIFAR-10 dataset. Spintronic devices driven by spin–orbit torque (SOT) have a lot of potential for future neuromorphic computing hardware platforms. Nevertheless, problems such as multistate loss, weight time-dependent variability, and output discontinuity ensue when the device size is reduced to the nanoscale, which are contradictory to the requirements of traditional high-precision neural networks. In this study, we propose a high-precision all-spin neural network based on magnetization switching of a simple nanoscale multi-functional SOT device. The all-spin neural network is implemented by the Binary Weight Network, in which the binary synapse is encoded by the two states formed by the device's deterministic switching and the practical neuron is realized by its stochastic switching probability. Furthermore, we use a difference derivation training algorithm for the general-purpose network in a novel way to be more compatible with the discontinuous neuron output. Using this strategy, our network can reach ∼81.73 % recognition accuracy on the universal CIFAR-10 dataset, paving the way for future practical hardware implementation of nanoscale SOT devices in high-precision compact neuromorphic computing. [ABSTRACT FROM AUTHOR]

The recent discovery of inherently stable two-dimensional (2D) transition-metal dichalcogenides (TMDs) provides a unique platform for spintronic devices. However, its efficacy for electric detection by spin Hall magnetoresistance (SMR) has not been established yet. In this work, we report on SMR in 2D TMDs/ferromagnet heterostructures, i.e., PtSe 2 /NiFe (Py), whose magnitude reaches the maximum with bilayer PtSe 2. Notably, the SMR value in bilayer PtSe 2 /Py heterostructures undergoes a sign change with increasing Py thickness. For thinner Py samples, the SMR rapidly decreases with increasing Py thickness, eventually changing from positive to negative. In the case of intermediate Py thicknesses, the SMR consistently exhibits negative behavior. However, for thicker Py samples, the negative SMR values gradually decrease. This complex behavior is attributed to the dominant and competing mechanisms that contribute to SMR, including the spin Hall effect (or Rashba-induced effect) and its inverse effect, the orbital Hall effect and its inverse effect, as well as interfacial spin–orbit-coupling-induced spin-current-to-charge-current conversion. These findings would expand the arsenal for advanced spintronic applications based on 2D TMDs. [ABSTRACT FROM AUTHOR]

Objective To observe changes of erythropoietin (EPO) and rheology in moderate and severe obstructive sleep apnea hypopnea syndrome (OSAHS) patients after the noninvasive positive pressure ventilation (NPPV) treatment. Methods Healthy adults were selected as control group (n=40) while moderate to severe OSAHS patients were selected as OSAHS group. OSAHS group was underwent NPPV treatment then, Levels of sleep apnea hypopnea index (AHI), sleep mean minimum oxygen saturation (LSaO2) and serum erythropoietin (EPO) were assessed, routine blood test and hemodynamic indexes were also checked before treatment and 1 and 3 months after treatment in both groups. Results In both groups serum EPO, blood, blood rheology indexes, AHI, LSaO2 were analysised at each time point by ANOVA repeated measures, all of which show significant different between groups and between each time points within the same group. Indexes in OSAHS group improved with prolonged treatment, but they are in the normal range in the control. Conclusion OSAHS patients with NPPV therapy can significantly relieve hypoxia, reduce serum EPO level and blood viscosity. So NPPV has important clinical significance in prevention and treatment of OSAHS. [ABSTRACT FROM AUTHOR]

The microstructures and magnetic properties of FePt(-SiO{x}-C) thin films grown on TiON and TiON/TiN intermediate layers were studied. TiON possessed smaller surface energy and smaller lattice constant than TiN. With increasing TiO{x} doping concentration, FePt grain shape changed from semi-spherical to square and grain size was significantly reduced. Meanwhile, good perpendicular magnetic anisotropy was retained, indicating that TiON intermediate layer could achieve a good balance between island growth and epitaxial growth. Furthermore, using TiON/TiN combined intermediate layer, FePt grain size was further reduced and the opening-up of in-plane M–H loop diminished. With 45 vol.% SiO{x}-25 vol.% C doping, well-isolated FePt grains with an average size as small as 5.7 nm and the grain size distribution of 0.9 nm were achieved. It also exhibited good perpendicular magnetic anisotropy with an out-of-plane coercivity of 18 kOe. [ABSTRACT FROM PUBLISHER]

Magnetic skyrmion, a nano-sized spin texture with topological property, have the potential to develop high-density, low-power, and multifunctional spintronic devices. To realize the reconfiguration of a single logic device and the implementation of the complete logic functions, a new reconfigurable and reusable skyrmion logic is proposed and verified by micromagnetic simulation. Logic functions including AND, OR, NOT, NAND and NOR are realized in ferromagnetic (FM) nanotrack by skyrmion-edge repulsions and the voltage control of magnetic anisotropy (VCMA) effect. The working state of the potential well can be controlled by the link of the input signals, thus changing the function type. In addition, through reusing skyrmion in circular track, the energy required for creation and deletion is reduced. This work can provide guidance for the design and optimization of reconfigurable and reusable logic devices with circular track based on skyrmion. [ABSTRACT FROM AUTHOR]

We use a periodic microring resonator array (MRRA) to realize photonic topological insulator. By tuning the coupling of resonators, two topological edge states can be observed in different bands in the dispersive band, normalized transmission spectrum and light field distribution. From the dispersion band structure, we calculate the group velocity, group velocity dispersion, normalized delay bandwidth product and other delay properties. It is demonstrated that optical delay lines (ODLs) in topological MRRA not only can obtain a comparable delay times, but also show a flatter transmission spectrum and more stable delay time, compared with the traditional coupled resonator optical waveguide. Our work may provide a theoretical reference for the topological ODLs with robust transmission. [ABSTRACT FROM AUTHOR]

For real-world applications, it is desirable to realize field-free spin–orbit torque (SOT) switching in thin films with high perpendicular magnetic anisotropy (PMA). In this paper, we report that field-free SOT switching in a L10-FePt single layer with a large switching ratio of 26% is obtained by using a MgO ⟨100⟩⋀8°/⟨100⟩ miscut substrate. It is found that field-free switching depends on the direction of the imposed pulse current. Only when the electric current is along the y (010)-direction but not along the x (100)-direction does field-free switching happen, which can be attributed to the tilted PMA induced symmetry breaking in the x–z plane. Furthermore, under the field-free condition, our FePt single layer system exhibits stable multi-state magnetic switching behavior and nonlinear synaptic characteristics. This work paves the way to realize field-free SOT switching in the L10-FePt single layer, which will have significant impact on spin memory devices and synaptic electronics. [ABSTRACT FROM AUTHOR]

A hexagonal honeycomb magnetic tunneling junction array with 72 nm pitch and 30 nm MgO critical dimension was successfully fabricated on a 1× nm dynamic random access memory platform by using a mature dynamic random access memory patterning solution and ion beam etch. To our knowledge, both pitch size and critical dimension size are the world's smallest ones for industrial magnetic tunneling junction arrays. To obtain such a high density and small sized magnetic tunneling junction array, a cross self-aligned double patterning technique, a triple layer hard mask scheme, and an optimized ion beam etch condition were adopted. During the optimization of the ion beam etch process, the dependence of a magnetic tunneling junction pillar profile on ion beam etch parameters for a high density hexagonal magnetic tunneling junction array has also been systematically studied. The depth of oxide recess and the magnetic tunneling junction sidewall angle increased with the ion beam etch amount, while magnetic tunneling junction critical dimension and hard mask remainder thickness decreased with increasing ion beam etch amount. [ABSTRACT FROM AUTHOR]

Magnetic skyrmions have the potential for a wide range of applications in the next generation of spintronics since they are topologically protected spin configurations in the nanometer length scale. In order to be used in the logic gate, it is necessary to consider how to manipulate magnetic skyrmions. At present, the current drive is the mainstream drive, but this method could consume enormous energy for large Joule heating. In this work, the potential well is introduced to drive skyrmion to reduce energy consumption. The potential well is generated by voltage-controlled magnetic anisotropy (VCMA). We study the possibility of the potential well-induced skyrmion movement within a certain distance, the relevant factors that affect the distance of skyrmion induction, and propose a switched-voltage driving structure within the well-established framework of micromagnetics. Its processes have been theoretically investigated and demonstrated, in which the switched-voltage driving structure can be used to drive skyrmions. Our results provide guidance for the design of low energy consumption voltage-driven skyrmion driving method and a new concept for track memory. [ABSTRACT FROM AUTHOR]

We analyze the coupling between an adjacent field ring and a coupling ring of the 2-D optical resonator array to obtain a topological edge state. Using the finite-difference time-domain method, the energy band structure, light field distribution, and transmission spectrum are simulated to investigate the optimized coupling parameters under the topological boundary state. When the coupling coefficient is approximately 0.775, the system can form a topological state in the wavelength of 1.55– $1.56~\mu \text{m}$ , while output can maintain a flat spectral response with normalized power above 0.9. The research in this article provides a basis for the potential application of topological edge states of 2-D coupled resonant optical waveguide in the field of photonic communication. [ABSTRACT FROM AUTHOR]

• The Ta/GdFeCo/Ta heterostructures are utilized to achieve a spin–orbit torque-driven multistate magnetization switching. • The switching ratio is up to 47.7% and the β DL and β FL are estimated as 85.64 Oe/(107 A/cm−2) and 35.05 Oe/(107 A/cm−2), respectively. • The findings establish that a stable four-resistor state exists, proofing multilevel memory behaviors and synaptic plasticity under current drive. • Neuromorphic computing built from this SOT device can perform unsupervised handwritten digit recognition with an accuracy of 92.25%. Neuromorphic computation of ferrimagnetic materials as artificial synapses is essential for the development of ultra-low power spintronic devices. Here, Ta/GdFeCo/Ta heterostructures are utilized to achieve a spin–orbit torque-driven multistate magnetization switching, complying with the requirements of neuromorphic computation. For Ta/GdFeCo/Ta device, the switching ratio is up to 47.7 % when the critical current density value is 1.26 × 107 A/cm2. Moreover, the β DL and β FL are estimated as 85.64 Oe/(107 A/cm−2) and 35.05 Oe/(107 A/cm−2), respectively. Subsequently, the findings establish that a stable four-resistor state exists, proofing multilevel memory behaviors and synaptic plasticity under current drive. It is further demonstrated that neuromorphic computing built from this SOT device can perform unsupervised handwritten digit recognition with an accuracy of 92.25 %. This research highlights the potential of SOT-driven multi-energy stabilized residual states for neuromorphic computing and multi-energy storage in the future. [ABSTRACT FROM AUTHOR]

• The crystal structure, optical, magnetic and dielectric properties of the GdCr 1- x Ga x O 3 (0 ≤ x ≤ 0.3) polycrystalline samples were investigated in detail. • The UV–vis measurement shows that the band gap raises from 2.76 eV to 2.99 eV of × = 0.2 sample due to the decrease of vacancy defect concentration, and then the decrease of band gap is related to the increase of particle size. • The magnetic properties show that negative magnetization and spin-reorientation is restrained and vanished when x ≥ 0.2, because the change of Gd3+-Cr3+ interaction. • The positive and decreasing MD coefficient indicates that the sample is in the antiferromagnetic state, and the antiferromagnetic interaction is gradually weakened. The structural, optical, magnetic, and dielectric properties of GdCr 1- x Ga x O 3 (0 ≤ x ≤ 0.3) polycrystalline samples were explored in this research. The lattice parameters, bond length, and bond angle are altered by Ga3+ doping. An evident transition point exists at x = 0.2. The UV–vis measurement shows that the band gap raises from 2.76 eV to 2.99 eV of × = 0.2 sample due to the decrease of vacancy defect concentration, and then the decrease of the band gap is related to the increase of particle size. The dilution of Ga3+ leads to a decrease in the antiferromagnetic transition temperature. Temperature dependent magnetization manifests that the negative magnetization and spin reorientation are inhibited and vanished when x ≥ 0.2. Importantly, the dielectric permittivity is consistent with the variation of the magnetic properties, proving the existence of magnetoelectric coupling in Ga-doped samples. Simultaneously, the weakened antiferromagnetic interaction also lessens the positive MD coefficient, which correspondingly correlates with the variation in magnetic properties. This study can serve as a guide for comprehending the evolution of microstructure, magnetic and dielectric properties of RCrO 3 materials. [ABSTRACT FROM AUTHOR]

We propose and analyse a novel optical pressure sensor based on series-coupled double microring resonators (SDMRRs) on a simple beam. The pressure applied on the sensor is measured through the change of the optical transmission spectrum at the output port. The optical transmission performances of the SDMRRs have been analysed and compared with the single and paralleled-coupled structures by the method of finite element analysis and numerical simulation. The simulation results showed that the stress sensitivity is 0.0225 kPa-1 and linear measurement range of the sensor is 30 kPa. Furthermore, the influence of the amplitude transmission coefficient, half round phase shift and microring radius on the sensitivity have been investigated to optimize the sensor performance. This proposed sensor can be used for the smaller pressure detection in automotive, aerospace, oil/logging equipment and other harsh environmental application. [ABSTRACT FROM AUTHOR]

All-optical switching (AOS) is an emerging recording technology by using femtosecond laser to manipulate the ultrafast magnetization reversal for future super high density magnetic storage. TbCo films possess a ferrimagnetic structure and large perpendicular anisotropy and, thus, become a potential material for AOS. In this paper, we simulate the ultrafast magnetization reversal domain of Co-sublattice in TbCo films under 100 fs pulse laser with a general theoretical framework, and our simulation results show that TbCo films irradiated with a higher power fluence laser have a larger reversal domain of Co-sublattice due to the higher peak temperature and the further critical isotherm of electrons. Moreover, high Co content can help Co-sublattice form a large reversal domain, but is unable to obtain the highly uniform reversal domain perhaps attributed to the insufficient anti-ferromagnetic interaction between Tb atoms and Co atoms. [ABSTRACT FROM AUTHOR]

Recently miniaturization, integration and high sensitivity are becoming the mainstream of the development of pressure sensing technology. This paper proposes a pressure sensor realized with the microring resonator on a cantilever beam. The performance of the pressure sensor is theoretical analyzed and then simulated using finite element modeling. It shows that the cantilever beam substrate can greatly improve the sensitivity compared with a simple supported beam. The fabricated microring resonator pressure sensor has 3 dB bandwidth of about 0.1488 nm and a Q-factor of 10511. The experimental results demonstrate that the resonant wavelength shift of the microring pressure sensor has an almost linear relationship with the displacement of pressure testing device. [ABSTRACT FROM AUTHOR]

A seismic data acquisition system based on wireless network transmission is designed to improve the low-frequency response and low sensitivity of the existing acquisition system. The system comprises of a piezoelectric transducer, a high-resolution data acquisition system, and a wireless communication module. A seismic piezoelectric transducer based on a piezoelectric simply supported beam using PMN-PT is proposed. High sensitivity is obtained by using a new piezoelectric material PMN-PT, and a simply supported beam matching with the PMN-PT wafer is designed, which can provide a good low-frequency response. The data acquisition system includes an electronic circuit for charge conversion, filtering, and amplification, an FPGA, and a 24-bit analog-to-digital converter (ADC). The wireless communication was based on the ZigBee modules and the WiFi modules. The experimental results show that the application of the piezoelectric simply supported beam based on PMN-PT can effectively improve the sensitivity of the piezoelectric accelerometer by more than 190%, compared with the traditional PZT material. At low frequencies, the fidelity of the PMN-PT piezoelectric simply supported beam is better than that of a traditional central compressed model, which is an effective expansion of the bandwidth to the low-frequency region. The charge conversion, filtering, amplification, and digitization of the output signal of the piezoelectric transducer are processed and, finally, are wirelessly transmitted to the monitoring centre, achieving the design of a seismic data acquisition system based on wireless transmission. [ABSTRACT FROM AUTHOR]

The detection resolution of a giant magneto-impedance (GMI) sensor is mainly limited by its equivalent input magnetic noise. The noise characteristics of a GMI sensor are evaluated by noise modeling and simulation, which can further optimize the circuit design. This paper first analyzes the noise source of the GMI sensor. It discusses the noise model of the circuit, the output sensitivity model and the modeling process of equivalent input magnetic noise. The noise characteristics of three modules that have the greatest impact on the output noise are then simulated. Finally, the simulation results are verified by experiments. By comparing the simulated noise spectrum curve and the experimental noise spectrum curve, it is demonstrated that the preamplifier and the multiplier contribute the most to the output white noise, and the low-pass filter plays a major role in the output 1/f noise. These modules should be given priority in the optimization of the noise of the conditioning circuit. The above results provide technical support for the practical application of low-noise GMI magnetometers. [ABSTRACT FROM AUTHOR]