ABSTRACT Upconversion nanoparticle (UCNP)‐based hybrid heterostructures are emerging as a versatile platform for next‐generation optoelectronic devices and intelligent technologies, owing to their capability to convert low‐energy near‐infrared (NIR) photons into higher‐energy visible or ultraviolet (UV) emission. This review provides a critical overview of recent advances in UCNP design, interface engineering, and hybrid integration with organic, inorganic, and low‐dimensional materials, and clarifies how structural and compositional tailoring governs optical coupling and device performance. The diverse optoelectronic applications of UCNP hybrid systems, including photodetectors, solar cells, light‐emitting diodes (LEDs), and optical memories, are systematically discussed with particular emphasis on energy transfer and charge transport processes that underpin efficiency enhancement. Persistent challenges such as spectral mismatch, interfacial losses, and scalable fabrication are analyzed from both materials and device perspectives. Finally, future opportunities for UCNP hybrid heterostructures in intelligent sensing, neuromorphic information processing, biomedical applications, and space‐related optoelectronics are outlined, highlighting their potential to bridge photon conversion, information processing, and intelligent optoelectronic functionalities within unified material platforms.

Threshold-switching memristors (TSMs) exhibit volatile turn-on at a threshold voltage and self-reset when the device voltage drops below the hold voltage, naturally providing the trigger-and-reset functions required for spiking neurons. This letter presents a compact SPICE-compatible phenomenological macro-model that emulates the threshold-switching window defined by Vth and Vhold and is directly compatible with CMOS co-simulation. Using this model, a minimal TSM-based leaky integrate-and-fire (LIF) neuron is demonstrated, showing monotonic tuning of firing frequency with input voltage and control resistance. A low-overhead adaptive module that converts spike activity into a slowly varying control voltage is further introduced to realize an adaptive LIF (ALIF) neuron with spike-frequency adaptation and recovery. Energy-per-spike scaling with membrane capacitance is investigated for C1 ranging from 0.25 to 8 nF under Vin=3.25, 3.50, and 3.75 V. Robustness against key parameter variations is further evaluated using Monte Carlo simulations to quantify the efficiency and sensitivity of the proposed circuit.

Magnetic droplet solitons-self-localised, strongly nonlinear spin-wave states-offer compact microwave sources in nanocontact (NC) spin-torque oscillators, yet their frequency agility and coherence remain sensitive to device geometry. Here we introduce a wedge-shaped (thickness-graded) free layer to engineer the internal demagnetising field and thereby control droplet nucleation, frequency and linewidth within a single device. Using micromagnetic simulations (MuMax3) of spin-valve with strong perpendicular anisotropy Co/Ni free layer, we place NC at systematically varied positions along the gradient and extract the formation of droplet as well as nucleation time and current and steady-state spectra. We find that thicker regions require higher current and exhibit wider hysteresis-like loops, while the nucleation frequency increases monotonically towards the thin side, accompanied by improved phase coherence. In dual-contact geometries, we map a thickness-gradient-dependent critical merging distance and its current scaling. These results establish thickness gradients as a practical, fabrication-compatible knob for tuning droplet dynamics and suggest gradient-engineered free layers for fast, coherent droplet-based microwave oscillators.

Drop casting method is a widely used technique in various fields of science and technology due to its ultra-fast, cost-effective, and straightforward nature. However, its application for coating materials containing magnetic elements is limited because of the agglomeration of materials during the coating process. In this study, we achieve uniform layers by applying heat and a magnetic field during the coating procedure, conditions that would otherwise be unattainable. The heat and magnetic fields are generated by passing electrical current through the substrate. We apply our developed technique to coat the graphene-magnetic nanoparticle composite on the surface of a magnetic field sensor, which is highly sensitive to surface roughness. As a result, we observe an enhanced Giant Magnetoimpedance (GMI) ratio, increasing from 280 to 361

We investigate the effect of strain on the magnetic resonance characteristics of in-plane magnetized synthetic antiferromagnets (SAFs) through micromagnetic simulations and theoretical modeling. By applying strain via a piezoelectric substrate, we modulate the in-plane uniaxial anisotropy of the ferromagnetic layers and analyze its impact on the ferromagnetic resonance spectra. The results show that strain significantly alters the spin-wave dispersion and resonance modes, leading to changes in magnetic ordering. A critical transition from a spin-flop to a spin-flip state is observed as strain-induced anisotropy increases. Additionally, our study quantifies the correlation between strain variations and the effective anisotropic field, demonstrating the tunability of magnetic properties via strain. We observe good agreement between the simulations and analytical predictions by including a magnetoelastic anisotropy field in our theoretical framework. These findings provide valuable insights into the magnetoelastic response of nanoscale SAFs and highlight the potential of strain-mediated control of magnetization dynamics for spintronic applications and microwave communication technologies.

The trajectory fitting algorithm in the wafer pre-aligner plays a crucial role in the semiconductor manufacturing field, and the accuracy of wafer alignment determines the quality and yield of the process. However, existing methods still face significant challenges in terms of accuracy, computational efficiency, and robustness in complex environments. In this study, we propose an iteratively reweighted least squares (IRLS) based on a five-layer perceptron (IRLS-FLP). This method guides the training process of the FLP through fitting loss, distance consistency loss, slope consistency loss, and residual loss, significantly reducing the model's dependence on data volume and data distribution. Meanwhile, the trained model can directly predict the weight of each sample point, avoiding the repeated iteration process in IRLS and improving computational efficiency. In addition, we constructed a geometric model containing dual-path loss based on the mechanical structure of 8-inch physical vapor deposition (PVD) equipment. With polar coordinates as input, the approximate transformation error is within 0.00053 mm, and the accuracy is higher than that of the single-path loss model. Simulation experiments show that in scenarios with noise and outliers, the average radius error of IRLS-FLP is 96.64% lower than that of the least squares method (LSM) and 79.91% lower than that of IRLS, and the average running time is 14.26 ms, second only to LSM. When verified on 8-inch PVD equipment, the average radius error of IRLS-FLP is as low as 0.0587 mm, which is a reduction of 76.33%-97.30% compared with existing methods. It provides a high-precision, high-efficiency, and robust solution for semiconductor precision positioning and has important engineering application value.

We present here a magnetic imaging setup for magnetic thin films, allowing two methods of probing: Magneto-Optical Kerr Effect and Nitrogen-vacancy probing. The first mode allows a quick viewing of the magnetic domains, with a resolution limited by optical diffraction, but does not provide quantitative measurement of the magnetization. This information is obtained by adding the complementary NV imaging mode, which consists of the widefield imaging of an NV-doped diamond plate on top of the magnetic film. We can then image the magnetic domains with high resolution and simultaneously measure the total magnetic moment of the order of 10-15 A m2 from the influence of the stray magnetic field on the NV optically detected magnetic resonance spectrum.

Collinear antiferromagnetic (AFM) materials have the unique promise of no stray fields, displaying ultrafast dynamics, and being robust against perturbation fields which motivate the extensive research of antiferromagnetic spintronics. However, the detection of antiferromagnetic order poses formidable challenges. Here, we report the electrical detection of colinear antiferromagnetism in all-epitaxial RuO2/MgO/RuO2 tunnel junctions (TJ) using spin-flop tunneling anisotropic magnetoresistance (TAMR). We measured a TAMR ratio of around 60% at room temperature, which arises from the switching between the parallel and perpendicular configurations of the adjacent collinear AFM state. Furthermore, we carried out angular-dependent measurements using this antiferromagnetic tunnel junction (AFM-TJ) and showed that the magnitude of anisotropic longitudinal magnetoresistance in the AFM-TJ can be controlled by the direction of an external magnetic field. First principles electronic structure calculations corroborate that the collinear antiferromagnetic TJ may produce a substantially large TAMR ratio. The emergence of resonant interfacial states, combined with the tunneling transmission through the MgO barrier and the substantial spin-orbit coupling (SOC) strength of Ru, especially when augmented by oxygen doping, leads to the significant enhancement observed in the tunneling anisotropic magnetoresistance (TAMR). Our work not only propels antiferromagnetic materials to the forefront of spintronic device innovation but also unveils a novel paradigm for electrically controlled antiferromagnetic spintronics, auguring transformative advancements in high-speed, low-energy information devices.

Ultrathin spintronic THz emitters (STEs) have shown exceptional advantages across various applications, offering a compelling combination of cost-effectiveness and high performance. However, the functional spin THz devices are still lacking. Here, we propose a tri-band and one-foci sparse-aperture achromatic spintronic terahertz Fresnel-Zone-Plate emitter, and three arbitrarily generated THz band waves are achieved with achromatic performance. More than 20 times enhancement of the focused field intensity is gotten. Furthermore, the structure of the AST-FE is optimized by using a bidirectional Deep Neural Network. The efficiency and amplitude of the generated THz, along with its focusing characteristics, are both enhanced. By integrating this flat-spin THz device with other reported achromatic methods, we can obtain multi-frequency achromatic THz waves easily. This research will promote the study and use of spin THz devices, and make great influence of the THz system.

In spintronics, characterizing the temperature dependence of spin Hall angle (SHA) has been a common method to explore the underlying mechanisms of spin Hall effect (SHE). However, the experimental reports of orbital Hall effect (OHE) under varying temperatures remain limited. Here, we systematically investigate the effective charge-to-spin conversion efficiencyθHin Ta/Ni and Ta/CoFeB bilayers across the temperature ranging from 10 K to 300 K, where theθHrepresents the combined contribution of the SHA and the orbital Hall angle (OHA). TheθHof Ta/Ni remains positive across the investigated temperature range, indicating that the OHE dominates over the SHE. The Ta/CoFeB sample serves as a reference with negligible OHE, exhibiting negative values ofθHthat are consistent with the SHA of Ta. As temperature decreases, theθHof both Ta/Ni and Ta/CoFeB increase with similar trends. Due to the significantly smaller difference of SHAs in Ta/Ni and Ta/CoFeB compared to those of OHAs, we suggest that the similar trends ofθHdemonstrate the weak temperature dependence of OHA in Ta/Ni. This finding advances the comprehensive understanding of OHE and may pave the way for the application of orbitronics.

The advancement of magnetic random access memory (MRAM) benefits from academic research on magnetic tunnel junctions (MTJs). However, deposition systems for academic research are often limited by atomic-scale control, process automation, and post-deposition processing, resulting in suboptimal tunneling magnetoresistance (TMR) ratios. We developed a deposition system optimized for perpendicular MTJ (p-MTJ) deposition, addressing key limitations in atomic-scale deposition, automation, and process control. Optimizations in critical components such as the cathode, sample manipulator, and automated deposition software were implemented. A dedicated process control chamber for post-annealing was introduced to enhance perpendicular magnetic anisotropy (PMA) and TMR. Experimental characterization confirmed that the deposited films exhibited low interfacial roughness (the average roughness (R-a) of MgO <0.35 nm, other materials' R-a < 0.25 nm). The CoFeB/MgO multilayers achieved wide-range PMA through CoFeB thicknesses from 0.7 to 1.1 nm in 0.1-nm steps, confirming atomic-scale deposition resolution and superior interface quality. Through fine-tuning, the full-stack p-MTJ achieved a TMR of 135%, validating the precise control capability of our system over TMR modulation. This system offers a more efficient platform for MRAM research and further innovation.

The rapid advancement of future information technologies necessitates the development of high-efficiency and cost-effective solutions for terahertz emitters, which hold significant practical value in next-generation communication, terahertz sensing, and quantum computing applications. Distinguished from trivial materials, three-dimensional topological insulators exhibit spin-momentum locking in helical Dirac surface states, making them highly efficient spin-to-charge converters that have the potential to revolutionize electronics. However, the efficiency of utilizing topological insulators for spin terahertz emission has not yet matched that of spin manipulation in other spintronic devices. Here, we investigate the spin terahertz emission properties of high crystalline quality (Bi1-xSbx)2Te3/Fe heterostructures through band structure engineering. Notably, contrary to expectations, the strongest terahertz radiation is not achieved at the charge neutrality point. Through an analysis of influencing factors and a temperature-independent investigation, we identify interface transparency as the primary factor affecting emission efficiency. To optimize interfaces and enhance spin-to-charge conversion efficiency, a Rashba-mediated Dirac surface state is constructed by attaching a Bi layer. Furthermore, with doping concentrations of 0, 0.5, and 1, respectively, we observe enhancements in intensity by 35.1, 50.3, and 44.3%. These results provide a detailed assessment of interfacial and doping effects in topological-insulator-based terahertz emitters and contribute to the understanding of spin-to-charge dynamics in topological materials.

The interfacial Dzyaloshinskii–Moriya interaction (DMI) plays a pivotal role in stabilising and controlling the motion of chiral spin textures, such as Néel-type bubble domains, in ultrathin magnetic films—an essential feature for next-generation spintronic devices. In this work, we investigate domain wall (DW) dynamics in magnetron-sputtered Ta(3 nm)/Pt(3 nm)/Co(1 nm)/RuO2(1 nm) [Ru(1 nm)]/Pt(3 nm) multilayers, benchmarking their behaviour against control stacks. Vibrating sample magnetometry (VSM) was employed to determine saturation magnetisation and perpendicular magnetic anisotropy (PMA), while polar magneto-optical Kerr effect (P-MOKE) measurements provided coercivity data. Kerr microscopy visualised the expansion of bubble-shaped domains under combined perpendicular and in-plane magnetic fields, enabling the extraction of effective DMI fields. Brillouin light scattering (BLS) spectroscopy quantified the asymmetric propagation of spin waves, and micromagnetic simulations corroborated the experimental findings. The Pt/Co/RuO2 system exhibits a Dzyaloshinskii–Moriya interaction (DMI) constant of ≈1.08 mJ/m2, slightly higher than the Pt/Co/Ru system (≈1.03 mJ/m2) and much higher than the Pt/Co control (≈0.23 mJ/m2). Correspondingly, domain walls in the RuO2-capped films show pronounced velocity asymmetry under in-plane fields, whereas the symmetric Pt/Co/Pt shows negligible asymmetry. Despite lower depinning fields in the Ru-capped sample, its domain walls move faster than those in the RuO2-capped sample, indicating reduced pinning. Our results demonstrate that integrating RuO2 significantly alters interfacial spin–orbit interactions.

Ferromagnetic multilayer thin films with oxide capping layer have potential applications in voltage-controlled magnetic devices. Here, we present the optimization of the magnetic and dielectric properties of CoFeB/MgO thin films with different capping layers (Ta, Al2O3, and HfO2). We find that the samples with oxide capping layers show a higher perpendicular magnetic anisotropy (PMA) than those with a Ta capping layer. Meanwhile, a high dielectric constant of 58 is obtained in samples capped with 30 nm of HfO2. This high dielectric constant is attributed to the formation of an oxygen vacancy-related capacitive double layer in the HfO2 film according to X-ray diffraction analyses and current-voltage measurements. Finally, we find that the optimal annealing temperature, which allows for both high PMA and dielectric constant, is between 250 degrees C and 290 degrees C. Our results could contribute to designing high-performance materials for controlling interfacial magnetic properties in novel spintronic devices.

Orbitronic devices operate by manipulating orbitally polarized currents. Recent studies have shown that these orbital currents can be excited by femtosecond laser pulses in a ferromagnet such as Ni and converted into ultrafast charge currents via orbital-to-charge conversion. However, the terahertz emission from orbitronic terahertz emitters based on Ni is still much weaker than that of the typical spintronic terahertz emitter. Here, this work reports a more efficient light-induced generation of orbital current from a CoPt alloy, and the terahertz emission from CoPt/Cu/MgO is comparable to that of benchmark spintronic terahertz emitters. By varying the composition of the CoPt alloy, the thickness of Cu, and the capping layer, this work confirms that THz emission primarily originates from the orbital accumulation generated within CoPt, propagating through Cu, followed by subsequent orbital-to-charge conversion due to the inverse orbital Rashba-Edelstein effect at the Cu/MgO interface. This study provides strong evidence for the efficient orbital current generation in CoPt alloy, paving the way for efficient orbital terahertz emitters.

Spin-orbit torque (SOT) has great potential application for developing next-generation magnetic random-access memory (MRAM). For efficient utilization of the SOT MRAM, most efforts have been focused on reducing power consumption by improving the SOT efficiency. Here, we report that inserting an ultrathin IrxMn1-x (or PtxMn1-x) layer at the heavy-metal-ferromagnet interface is an effective strategy to increase the SOT efficiency. By performing spin-torque ferromagnetic magnetic resonance and second-harmonic Hall measurements, we found that the absolute values of the charge-to-spin conversion efficiency increase from 0.09 for annealed W-Co20Fe60B20 (CFB) sample to 0.15 for annealed W-IrxMn1-x-CFB sample. The enhancement of the SOT efficiency can be attributed to the reduction of interfacial spin-memory loss at the annealed W-IrxMn1-x (or PtxMn1-x)-CFB samples. Moreover, currentdriven magnetization switching with a reduced critical current density has been achieved in the annealed W-IrxMn1-x-CFB samples. This study highlights the significant roles of the IrxMn1-x (or PtxMn1-x) insertion layer on improving the SOT efficiency and provides a strategy to improve the SOT efficiency through nanoengineering of the IrxMn1-x (or PtxMn1-x) insertion layer for energy-efficient SOT devices.

Spin-orbit torque (SOT) has great potential application for developing next-generation magnetic random-access memory (MRAM). For efficient utilization of the SOT MRAM, most efforts have been focused on reducing power consumption by improving the SOT efficiency. Here, we report that inserting an ultrathin ${\mathrm{Ir}}_{x}{\mathrm{Mn}}_{1\text{\ensuremath{-}}x}$ (or ${\mathrm{Pt}}_{x}{\mathrm{Mn}}_{1\text{\ensuremath{-}}x}$) layer at the heavy-metal--ferromagnet interface is an effective strategy to increase the SOT efficiency. By performing spin-torque ferromagnetic magnetic resonance and second-harmonic Hall measurements, we found that the absolute values of the charge-to-spin conversion efficiency increase from 0.09 for annealed W-${\mathrm{Co}}_{20}{\mathrm{Fe}}_{60}{\mathrm{B}}_{20}$ (CFB) sample to 0.15 for annealed $\mathrm{W}\text{\ensuremath{-}}{\mathrm{Ir}}_{x}{\mathrm{Mn}}_{1\text{\ensuremath{-}}x}$-CFB sample. The enhancement of the SOT efficiency can be attributed to the reduction of interfacial spin-memory loss at the annealed $\mathrm{W}\text{\ensuremath{-}}{\mathrm{Ir}}_{x}{\mathrm{Mn}}_{1\text{\ensuremath{-}}x}$ (or ${\mathrm{Pt}}_{x}{\mathrm{Mn}}_{1\text{\ensuremath{-}}x})\text{\ensuremath{-}}\mathrm{CFB}$ samples. Moreover, current-driven magnetization switching with a reduced critical current density has been achieved in the annealed $\mathrm{W}\text{\ensuremath{-}}{\mathrm{Ir}}_{x}{\mathrm{Mn}}_{1\text{\ensuremath{-}}x}\text{\ensuremath{-}}\mathrm{CFB}$ samples. This study highlights the significant roles of the ${\mathrm{Ir}}_{x}{\mathrm{Mn}}_{1\text{\ensuremath{-}}x}$ (or ${\mathrm{Pt}}_{x}{\mathrm{Mn}}_{1\text{\ensuremath{-}}x}$) insertion layer on improving the SOT efficiency and provides a strategy to improve the SOT efficiency through nanoengineering of the ${\mathrm{Ir}}_{x}{\mathrm{Mn}}_{1\text{\ensuremath{-}}x}$ (or ${\mathrm{Pt}}_{x}{\mathrm{Mn}}_{1\text{\ensuremath{-}}x}$) insertion layer for energy-efficient SOT devices.

Orbitronics devices operate by manipulating orbitally-polarized currents. Recent studies have shown that these orbital currents can be excited by femtosecond laser pulses in ferromagnet as Ni and converted into ultrafast charge current via orbital-to-charge conversion. However, the terahertz emission from orbitronic terahertz emitter based on Ni is still much weaker than the typical spintronic terahertz emitter. Here, we report more efficient light-induced generation of orbital current from CoPt alloy and the orbitronic terahertz emission by CoPt/Cu/MgO shows terahertz radiation comparable to that of efficient spintronic terahertz emitters. By varying the concentration of CoPt alloy, the thickness of Cu, and the capping layer, we confirm that THz emission primarily originates from the orbital accumulation generated within CoPt, propagating through Cu and followed by the subsequent orbital-to-charge conversion from the inverse orbital Rashba-Edelstein effect at the Cu/MgO interface. This study provides strong evidence for the very efficient orbital current generation in CoPt alloy, paving the way to efficient orbital terahertz emitters.

The magnetic properties in Pt/Co and Pt/Co/X/Pt multilayers (with X= different caping materials), such as perpendicular magnetic anisotropy (PMA), are of particular interest for spintronic devices. In particular, it is important to obtain a strong PMA on the flexible substrate in the field of wearable devices and structural health monitoring. However, the different stack structures and growth conditions influence the magnetic properties of the film. Here, we investigate the magnetic properties in Pt/Co/Pt and Pt/Co/X/Pt structures deposited by sputtering with different substrates (hard and flexible), layer thicknesses, different deposition temperatures of the buffer layer, different capping layers, insertion of a thin interlayer and irradiation by He+ ions. We exhibite conditions for better crystallinity, enhanced PMA, homogeneous domain wall motion and stronger DMI. The experimental results also show that the optimized film conditions can also yield strong PMA on the flexible substrate.

The study of interface spin effects in spintronic multilayer films requires distinguishing the effects generated by different interfaces. However, testing in atmospheric conditions requires a capping layer to protect the films, which introduces new interfaces and limits the study of interface spin-dependent effects. To address this challenge, we have developed an integrated ultra-high vacuum cluster system that includes magnetron sputtering equipment, ion irradiation equipment, and time-resolved magneto-optical Kerr effect (TR-MOKE) equipment. Our sputtering system integrates 12 cathodes in a single chamber, allowing the co-sputtering of four targets. The ultimate vacuum can reach 1 × 10-10 mbar, and the deposition resolution of 0.1 nm can be achieved. Ion irradiation equipment can ionize to produce He+, and by screening and accelerating the implantation of He+ into multilayer films, ion scanning is realized, and up to 30 keV energy can be applied to the films. The TR-MOKE equipment can detect ultra-fast magnetic dynamics processes in vacuum conditions, and its external magnetic field can be rotated 360°. Our vacuum cluster system connects the three subsystems, allowing in situ film deposition, regulation, and characterization. By accurately detecting the effects of different layers, the system can distinguish the interface effects of multilayers. Experimental results demonstrate that the three subsystems can work independently or coordinate to observe the interface effects of multilayers.