Search Results (23)

The conventional static imprint effect in Hf_xZr_1−xO₂ (HZO) ferroelectric (FE) devices, which degrades data retention, is generally characterized by a shift in the hysteresis loop along the electric field axis. Unlike the static imprint effect, the dynamic imprint effect emerges under dynamic electric fields or actual operating conditions, making the FE film exceptionally sensitive to switching pulse parameters and domain history. In HZO anti-ferroelectric (AFE) devices, this dynamic imprint effect alters the coercive field distribution associated with domain switching and poses a significant challenge to long-term stable device operation. This study systematically investigates the dynamic imprint effect and its recovery process using a comprehensive integration of first-order reversal curve (FORC) analysis, transient current-voltage (I-V), and polarization-voltage (P-V) characterization. By analyzing localized imprint behavior under sub-cycling conditions, mechanisms and recovery pathways of imprint in AFE devices are proposed. Finally, possible physics-based mechanisms describing imprint behaviors and recovery behaviors are discussed, providing insights for optimizing AFE memory technology performance and reliability. Full article

Wiegand sensors are essential components in self-powered Internet of Things (IoT) nodes, as they can output pulse voltages without an external power supply. Previous research has established that the attachment of ferrite beads to Wiegand wire terminals substantially enhances the sensor’s pulse voltage output. However, the fundamental mechanism responsible for this enhancement remains unclear at the microscopic magnetic level. This investigation systematically examines how ferrite bead attachments alter magnetization reversal processes, Barkhausen jump characteristics, and the energy output in Wiegand wires. Experimental results reveal that ferrite beads enhance irreversible magnetization, modify interaction distributions, and transform the magnetic structure of Wiegand wires. These modifications collectively result in a 1.5–2.0 times higher pulse voltage amplitude and 30–40% greater output energy, establishing a theoretical framework for Wiegand sensor optimization. The research methodology combines vibrating sample magnetometer (VSM) measurements with first-order reversal curve (FORC) analysis to elucidate the underlying micromagnetic mechanisms. Full article

We present an alternative to the classical SQUID magnetometric measurements for the First-Order Reversal Curve (FORC) diagram approach by employing differential scanning calorimetry (DSC) experiments. After discussing the main results, the advantages and limitations of the magnetometric FORCs, we introduce the calorimetric method. We argue that, while the results are comparable to those obtained via magnetometry, the calorimetric method not only significantly simplifies the required mathematical computations but also detects subtle or overlapping phase transitions that might be hard to distinguish magnetically. The methodology is illustrated through both experimental data and mean-field simulations. Full article

Transformers, reactors and other electrical equipment often work under harmonics and DC-bias working conditions. It is necessary to quickly and accurately simulate the hysteresis characteristics of soft magnetic materials under various excitation conditions in order to achieve accurate calculations of core loss and the optimal design of electrical equipment. Based on Preisach hysteresis model, a parameter identification method for asymmetric hysteresis loop simulation is designed and applied to the simulation of hysteresis characteristics under bias conditions of oriented silicon steel sheets. In this paper, the limiting hysteresis loops of oriented silicon steel sheets are obtained through experiments under different working conditions. The first-order reversal curves(FORCs) with asymmetric characteristics is generated numerically, and then the Everett function is established under different DC bias conditions. The hysteresis characteristics of the oriented silicon steel sheets under harmonics and DC bias are simulated by improving FORCs identification method of the Preisach model. By comparing the results of simulation and experiment, the effectiveness of the proposed method is verified, so as to provide an important reference for material production and application. Full article

Amorphous microwires have attracted substantial attention in the past decade because of their useful technological applications. Their bistable magnetic response is determined by positive or negative magnetostriction, respectively. First-order reversal curves (FORC) are a powerful tool for analyzing the magnetization reversal processes of many-body ferromagnetic systems that are essential for a deeper understanding of those applications. After theoretical considerations about magnetostatic interactions among microwires, this work introduces a systematic experimental study and analysis of the FORC diagrams for magnetostrictive microwires exhibiting an individually bistable hysteresis loop, from a single microwire to sets of an increasing number of coupled microwires, the latter considered as an intermediate case to the standard many-body problem. We performed the study for sets of quasi-identical and different hysteretic microwires where we obtained the coercivity $H_c$ and interaction $H_u$ fields. In the cases with relevant magnetostatic interactions, FORC analysis supplies deeper information than standard hysteresis loops since the intrinsic fluctuations of the switching field generate a complex response. For sets of microwires with very different coercivity, the coercivity distributions of the individual microwires characterize the FORC diagram. Full article

In this study, the appearance of magnetic moments and ferromagnetism in nanostructures of non-magnetic materials based on silicon and transition metals (such as iron) was considered experimentally and theoretically. An analysis of the related literature shows that for a monolayer iron coating on a vicinal silicon surface with (111) orientation after solid-phase annealing at 450–550 °C, self-ordered two-dimensional islands of α-FeSi₂ displaying superparamagnetic properties are formed. We studied the transition to ferromagnetic properties in a system of α-FeSi₂ nanorods (NRs) in the temperature range of 2–300 K with an increase in the iron coverage to 5.22 monolayers. The structure of the NRs was verified along with distortions in their lattice parameters due to heteroepitaxial growth. The formation of single-domain grains in α-FeSi₂ NRs with a cross-section of 6.6 × 30 nm² was confirmed by low-temperature and field studies and FORC (first-order magnetization reversal curves) diagrams. A mechanism for maintaining ferromagnetic properties is proposed. Ab initio calculations in freestanding α-FeSi₂ nanowires revealed the formation of magnetic moments for some surface Fe atoms only at specific facets. The difference in the averaged magnetic moments between theory and experiments can confirm the presence of possible contributions from defects on the surface of the NRs and in the bulk of the α-FeSi₂ NR crystal lattice. The formed α-FeSi₂ NRs with ferromagnetic properties up to 300 K are crucial for spintronic device development within planar silicon technology. Full article

Various coercive force field components in Wiegand wire exhibit a significant magnetization reversal under an applied magnetic field. A fast magnetization reversal is accompanied by a large Barkhausen jump, which induces a pulse voltage in a pickup coil wound around the Wiegand wire which serves as a power source for the devices or sensors. This study aims to elucidate the magnetization reversal in the Wiegand wire by using a first-order reversal curve (FORC) diagram method. The magnetic structure of the Wiegand wire typically comprises three layers: a soft layer, middle layer, and hard layer. In this study, we analyze the coercive and interactive force fields between the adjacent layers. The results demonstrate a high coercivity of the center core and a lower coercivity of the outer layer of the wire. Full article

The reverse magnetization behavior for bulk composite alloys containing Mn-Al-C and α-Fe nanoparticles (NPs) has been investigated by hysteresis loops, recoil, and first-order reversal curves (FORC) analysis. The effect of adding different percentages of α-Fe (5, 10, 15, and 20 wt. %) on the magnetic properties and demagnetization behavior of Mn-Al-C nanostructured bulk magnets was investigated. The fabricated nanocomposites were characterized by XRD and VSM for structural analysis and magnetic behavior investigations, respectively. The demagnetization curve of the sample Mn-Al-C-5wt. % α-Fe showed a single hard magnetic behavior and showed the highest increase in remanence magnetization compared to the sample without α-Fe, and therefore this combination was selected as the optimal composition for FORC analysis. Magnetic properties for Mn-Al-C-5 wt. % α-Fe nanocomposite were obtained as M_s = 75 emu/g, M_r = 46 emu/g, H_c = 3.3 kOe, and (BH)_max = 1.6 MGOe, indicating a much higher (BH)_max than the sample with no α-Fe. FORC analysis was performed to identify exchange coupling for the Mn-Al-C-0.05α-Fe nanocomposite sample. The results of this analysis showed the presence of two soft and hard ferromagnetic components. Further, it showed that the reverse magnetization process in the composite sample containing 5 wt. % α-Fe is the domain rotation model. Full article

Wiegand wires exhibit a unique fast magnetization reversal feature in the soft layer that is accompanied by a large Barkhausen jump, which is also known as the Wiegand effect. However, the magnetic structure and interaction in Wiegand wires cannot be evaluated by conventional magnetization hysteresis curves. We analyzed the magnetic properties of Wiegand wires at various lengths by measuring the first-order reversal curves (FORCs) and by evaluating the FORC diagram from a series of FORCs. In particular, we used a FeCoV Wiegand wire with a magnetic soft outer layer, an intermediate layer, and a hard core. The magnetization of the various layers in the wire could be identified from the FORC diagrams. Furthermore, based on the interaction between multiple layers, the positive and negative polarity of the FORC distribution was clarified. Full article

We present initial rock magnetic results for both lava flows and lapilli produced by the 2021 eruption of the Cumbre Vieja, La Palma (Canary Islands). Samples were taken during the eruption to minimize early alteration and weathering of the rocks and tephra. Standard procedures included progressive alternating field and thermal demagnetization, hysteresis curves, thermomagnetic experiments, progressive acquisition of isothermal remanent magnetization (IRM), and First-Order Reversal Curves (FORCs). Overall, our observations, including low to medium unblocking temperatures, isothermal remanent magnetization to 1 Tesla, and the abundance of wasp-waist hysteresis loops, strongly suggest the presence of Ti-rich titanomagnetites as the main remanence carriers in both lava flows and lapilli, in addition to some hematite as well. Whereas the former has been directly seen (SEM), hematite is elusive with nonmagnetic-based methods. Rock magnetic data, on a Day plot, also reveal that the magnetic grain size tends to be larger in the lava flows than in the lapilli. Full article

Product fault diagnosis has always been the focus of quality and reliability research. However, a failure–rate curve of some products is a symmetrical function, the fault analysis result is not true because the failure period of the products cannot be judged accurately. In order to solve the problem of fault diagnosis, this paper proposes a new Takagi-Sugeno (T-S) dynamic fault tree analysis method based on a Bayesian network accompanying the Wiener process. Firstly, the top event, middle event, and bottom event of the product failure mode are determined, and the T-S dynamic fault tree is constructed. Secondly, in order to form the Bayesian network diagram of the T-S dynamic fault tree, the events in the fault tree are transformed into nodes, and the T-S dynamic gate is also transformed into directed edges. Then, the Wiener process is used to model the performance degradation process of the stationary independent increment of the symmetric function distribution, and the maximum likelihood estimation method is applied to estimate the unknown parameters of the degradation model. Next, the product residual life prediction model is established based on the concept of first arrival time, and a symmetric function of failure–rate curve is obtained by using the product failure probability density function. According to the fault density function derived from the Wiener process, the reverse reasoning algorithm of the Bayesian network is established. Combined with the prior probability of the bottom event, the posterior probability of the root node is calculated and sorted as well. Finally, taking the insufficient braking force of electromagnetic brakes as an example, the practicability and objectivity of the new method are proved. Full article

Geometrically modulated magnetic nanowires are a simple yet efficient strategy to modify the magnetic domain wall propagation since a simple diameter modulation can achieve its pinning during the nanowire magnetization reversal. However, in dense systems of parallel nanowires, the stray fields arising at the diameter interface can interfere with the domain wall propagation in the neighboring nanowires. Therefore, the magnetic behavior of diameter-modulated nanowire arrays can be quite complex and depending on both short and long-range interaction fields, as well as the nanowire geometric dimensions. We applied the first-order reversal curve (FORC) method to bi-segmented Ni nanowire arrays varying the wide segment (45–65 nm diameter, 2.5–10.0 μm length). The FORC results indicate a magnetic behavior modification depending on its length/diameter aspect ratio. The distributions either exhibit a strong extension along the coercivity axis or a main distribution finishing by a fork feature, whereas the extension greatly reduces in amplitude. With the help of micromagnetic simulations, we propose that a low aspect ratio stabilizes pinned domain walls at the diameter modulation during the magnetization reversal. In this case, long-range axial interaction fields nucleate a domain wall at the nanowire extremities, while short-range ones could induce a nucleation at the diameter interface. However, regardless of the wide segment aspect ratio, the magnetization reversal is governed by the local radial stray fields of the modulation near null magnetization. Our findings demonstrate the capacity of distinguishing between complex magnetic behaviors involving convoluted interaction fields. Full article

The fabrication approach of a magnonic crystal with a step-like hysteresis behavior based on a uniform non-monotonous iron layer made by shadow deposition on a preconfigured substrate is reported. The origin of the step-like hysteresis loop behavior is studied with local and integral magnetometry methods, including First-Order Reversal Curves (FORC) diagram analysis, accompanied with magnetic microstructure dynamics measurements. The results are validated with macroscopic magnetic properties and micromagnetic simulations using the intrinsic switching field distribution model. The proposed fabrication method can be used to produce magnonic structures with the controllable hysteresis plateau region’s field position and width that can be used to control the magnonic crystal’s band structure by changing of an external magnetic field. Full article

The safety of unmanned ship berthing is of paramount importance. In order to explore the influence of wind and wave coupling, a berthing computational fluid dynamics (CFD) model was established, and the characteristics of speed field, pressure field, and vortex have been obtained under different speed, wind direction, and the quay wall distances. The results show that the total resistance of the hull against the current can be about 1.60 times higher compared to the downstream resistance, water flow resistance is the dominant factor, accounting for more than 80% of the total resistance. When changing the distance between ship and shore at fixed speed, the results found that the torque is small, but the growth rate is very large when driving below 2 m/s, and the torque growth rate is stable above 2 m/s. Based on the established coupling model, a multi-factor berthing safety study is carried out on an actual unmanned ship. The results show that when the speed increases from 4 m/s to 12 m/s, the curve slope is small, the resistance increases from 3666 N to 18,056 N, and the rear slope increases. The pressure increases with the speed, and when the speed is 24 m/s, the maximum pressure is up to 238,869 Pa. When the wind speed is fixed, the vertical force of the unmanned ship increases first and then decreases to zero and then reverses the same law change, and the maximum resistance is about 425 N at the wind angle of about 45 degrees; At 90 degrees, the maximum lateral force on an unmanned boat is about 638 N. The above results can provide control strategy for unmanned ship berthing safety, and provide theoretical basis for unmanned ship route planning and obstacle avoidance, safety design, etc. Full article

The magnetic structure of Wiegand wires cannot be evaluated using conventional magnetization hysteresis curves. We analyzed the magnetization reversal of a Wiegand wire by measuring the first-order reversal curves (FORCs). A FeCoV Wiegand wire with a magnetically soft outer layer and a hard magnetic core was used in this study. The magnetization reversal of the soft and hard regions in the wire was identified in the FORC diagrams. The magnetization reversal of the dominantly irreversible process of the soft layer and the magnetic intermediate region between the soft and hard regions was clarified. Full article