Recoil Curves Research Articles

Projectile Load Design Development and Construction comparing OCW, Ladder, Chronograph, and barrel acceleration FFT Methods for Numerical Models

The research and development of new materials and technologies orient the design, development, and construction of new sport optics products across the globe. With each improvement, whether in a riflescope or accessories, the final product must function without fail in the customer's hand and under the required specification conditions. Therefore, before the product is placed on the market it must be subject to a series of procedures, which involve both performing numerical analysis and physical tests to increase confidence and reliability. Numerical analyses require input data, and that must be consistent with real actions that influence the product to react. In the development of shooting equipment, the rifle recoil is considered the primary reaction for riflescopes, rifles, and accessories alike and is the most significant factor that could cause failure. For this reason, it is essential to use a load development process to have consistent energies, velocities, recoil curves, and reactions. This paper will present, discuss, and analyze the efficacy of the Optimum Charge Weight (OCW), ladder, chronograph, and barrel acceleration Fast Fourier Transform (FFT) load development methods and the results of each in load development.

A Review of Permanent Magnet Models Used for Designing Electrical Machines

This article serves as an overview of existing models of permanent magnets (PMs) for electrical machines. The review study starts with the linear recoil model, which is commonly used to describe the reversible part of the demagnetizing curve. It is a simple model, especially useful for representing materials with high anisotropy, such as ferrite, NdFeB, and SmCo. The model is harder to apply for nonlinear materials, such as Alnico, but still possible since their recoil curves are linear. The study shows how the linear recoil model could be extended to include irreversible demagnetization, temperature dependence, and angular dependence. All such models have their advantages and disadvantages, which will be discussed further. Both the magnetization and the risk of demagnetization are temperature-dependent. It could be noted that NdFeB has an increased risk of demagnetization at high temperatures, while ferrite has it at very low temperatures. The temperature dependence is described and compared for several materials, also including simplifying models. There are different methods to include the inclination angle of an applied magnetic field when studying the demagnetization of PMs. Several models describe different phenomena associated with the underlying dynamics of magnetism. Such models could then consider coercivity mechanisms and coherent rotation of magnetization, both with the Stoner–Wohlfarth model and models of domain wall motions.

Reverse Magnetization Behavior Investigation of Mn-Al-C-(α-Fe) Nanocomposite Alloys with Different α-Fe Content Using First-Order Reversal Curves Analysis.

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 Ms = 75 emu/g, Mr = 46 emu/g, Hc = 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.

Magnetization reversal processes in sintered permanent magnets Sm(Co, Fe, Zr, Cu)Z

The magnetic hysteresis properties of commercially available samples of sintered permanent magnets with the composition of Sm(Co0.796–xFe0.177CuxZr0.027)6.63 (x = 0.117 – 0.131) were investigated. To analyze the processes of magnetization and magnetization reversal, the magnetization curves from the thermally demagnetized state, major hysteresis loops, recoil curves, the dependence of the reversible magnetic susceptibility vs. magnetic fields strength, Kelly plots and angular dependences of the coercivity were used. These results indicate that magnetization reversal processes are more complicated than pinning. A model of magnetization reversal processes is proposed to explain why in some experiments the magnets exhibit a pinning mechanism of magnetization reversal and in some experiments a nucleation mechanism.

Observation of recoil magnetization curves outside the major loop in Co, Fe, and Ni films

We report a peculiar magnetization reversal observed in magnetron-sputtered Co, Fe, and Ni films. We found that some recoil (minor) magnetization curves lie entirely and way outside the major loop, a phenomenon referred to here as a recoil-curve overshoot. The greatly enhanced recoil curve's remanence and coercivity result in an up to 2.5-fold increase of loop's area. The model of pairs of exchange-coupled grains with misaligned anisotropy axes reproduces, in a very good agreement with the experiment, all key features of the recoil-curve overshoot as well as the kink that some major loops present before saturation. The disclosed features of the ferromagnetic hysteresis provide further insights into this important classical phenomenon.

Nanoimprinting of magnetic FeCo-based metallic glass thin films

The ability to create submicron/nanoscale patterns with magnetic alloys at low cost is difficult. Here, we demonstrate a method to create such patterns using Fe40Co35P10C10B5 metallic glass thin films. The viscous workability of a metallic glass thin film was used to make patterns with dimensions up to ~100 nm using the nanoimprinting technique, and the effects of the patterning on the magnetic properties of the metallic glass thin films were investigated. An increase in the out-of-plane coercivity (~380 Oe) and remanent magnetization (Mr = ~12% of the saturation magnetization, Ms) were observed for amorphous thin films patterned with a high density of nano-dots. This effect was observed because of changes to the magnetic shape anisotropy induced by the nano-imprinting. Two events of magnetization reversal were confirmed in the crystalline films of the same alloy. The reversal of magnetization under the low magnetic field of ~100 Oe corresponds to soft magnetic phases, whereas that at 2400 Oe corresponds to the hard magnetic phase. Recoil curve measurements suggest that the average magnetization-switching field of hard magnetic grains in the film was between 2800 and 3600 Oe. Based on our experimental results and analysis, we suspect the presence of tetragonal Fe–Co hard/semihard magnetic phase in crystalline thin films. We believe that the low-cost and large-area micro- to nanoscale patterning ability of the present magnetic thin films are promising for the development of various magnetic MEMS and memory devices.

Anisotropic Sm-Co nanopowder prepared by induction thermal plasma

A hard magnetic Sm-Co alloy nanopowder is successfully prepared by the recently-developed low oxygen-induction thermal plasma (LO-ITP) process. Spherical particles with an average diameter of 61 nm are achieved. According to the X-ray diffraction (XRD) profile, hard magnetic compounds of SmCo5 and SmCo7 are obtained. Transmission electron microscopic (TEM) observation confirms that the Sm-Co particles have a uniaxial anisotropic structure. This work also leads to the discovery of a previously-unknown core/shell particle with a Co-core/Sm-Co-shell structure, which has an ideal interface for exchange coupling, as the particle is formed with no oxide phase in the interface between the Co-core and Sm-Co-shell. Magnetic measurements show that coercivity is 5.6 kOe at room temperature and magnetization is 80 emu/g at 9 T, and the recoil curve shows spring-back behavior, suggesting exchange-coupling between the Co-core and the Sm-Co-shell. A numerical analysis demonstrates the formation mechanism of the Sm-Co alloy particles and the core/shell particles, and also suggests a strategy for improving the magnetic properties of the Sm-Co alloy nanopowder.

Reversal asymmetry and anomalous magnetic viscosity in exchange-bias systems

Employing vector magnetometry, interaction plots and model simulations, we probe the magnetization reversal in Co/Cu/IrMn exchange-biased trilayers. In the films with thin or no Cu spacer, the magnetization reversal is governed by domain-wall motion along one branch of the easy-axis hysteresis loop and by coherent rotation along the other. For thicker Cu spacers, both magnetization paths are dominated by coherent rotation. The latter also appears to be responsible for the reversal when the magnetic field is applied away from the exchange-bias direction for all films. We reveal a delayed domain-wall reversal along the descending-field path as compared to that predicted for coherent rotation. By exploiting in-field interaction plots, we evidenced a correlation between the asymmetric reversal and the exchange-bias coupling. Anomalous viscosity along recoil curves is detected and attributed to strong ferromagnetic coupling into the ferromagnet. The anomaly tends to fade away with the increase in the bias.

High performance RE–Fe–B sintered magnets with high-content misch metal by double main phase process**Project supported by the National Natural Foundation of China (Grant Nos. 51590880, 11564030, and 51571126), the National Key Research Program of China (Grant No. 2016YFB0700903), Fujian Institute of Innovation, Chinese Academy of Sciences (Grant No. FJCXY18040302), the Key Program of the Chinese Academy of Sciences (Grant No.

Double main phase process is applied to fabricate [(Pr, Nd)1 – xMMx]13.8FebalM1.5B5.9 (x = 0.5 and 0.7; M = Cu, Al, Co, and Nb) sintered magnets with high misch metal (MM) content. In comparison to the magnets by single main phase process, the enhanced magnetic properties have been achieved. For magnets of x = 0.7, Hcj increases to 371.9 kA/m by 60.5%, and (BH)max is significantly enhanced to 253.3 kJ/m3 by 56.9%, compared with those of the single main phase magnets of the same nominal composition. In combination with minor loops and magnetic recoil curves, the property improvement of magnets with double main phase method is well explained. As a result, it is demonstrated that double main phase technology is an effective approach to improve the permanent magnetic properties of MM based sintered magnets.

Feasibility Analysis of Magnetorheological Absorber in Recoil Systems: Fixed and Field Artillery

Magnetorheological (MR) absorbers in the artillery recoil systems are usually used to dissipate the impact energy as much as possible and reduce the recoil force transmitted to the artillery carriage, while the firing stability of artillery during buffer process is rarely considered. In this paper, we analyzed the firing stability characteristics of the fixed artillery and the field artillery systems and established corresponding mechanical models. Then, we proposed the ideal recoil F-v curves of these two kinds of artillery respectively. The “platform effect” of recoil curve was taken as the recoil force control target of the fixed artillery, while based on the firing stability, the linear segmented recoil curve was drawn up as the ideal recoil buffer control target of the field artillery. To verify the feasibility and controllability of the designed multi-stage MR absorber in two kinds of recoil buffer system, the impact tests were conducted under different current loadings. The test results show that the designed MR absorber can realize different buffer control effects by changing the input current, but the ideal “platform effect” recoil curve of the fixed artillery cannot be completely realized due to small controllable damping force output. In the field artillery recoil system, the MR absorber can realize ideal recoil buffer control in the range of 0 to 25 degree firing angles.

Calculation of Recoil Curves in Isotropic and Anisotropic Stoner–Wohlfarth Materials

With regard to hard magnetic materials, the recoil curves of hysteresis are applicable for motor designers. It is discussed how to calculate recoil curves of isotropic and anisotropic Stoner-Wohlfarth hysteresis, with different distributions as Gaussian and cos <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sup> (alpha). The Gaussian distribution is the most commonly used for representing texture in hard magnetic materials as NdFeB or ferrites. The Gaussian and cos <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sup> (alpha) distributions are compared and analytical functions are given. The analytical functions can reduce the time of calculation and also increase the accuracy of the results.

Investigations on low energy product of MnAl magnets through recoil curves

Ferromagnetic τ-MnAl is being investigated as a potential candidate for the development of rare-earth-free permanent magnets. Maximum energy product (BH)max is reported to be much lower than the expectations based on saturation magnetization (Ms), and magnetocrystalline anisotropy (K). We have reinvestigated the MnAl alloy to shed light on low (BH)max. We made ribbons of Mn54Al46 alloy and annealed them at different temperatures. As-quenched ribbons (ASQ) are mainly made from non-magnetic ε-MnAl and a weakly magnetic phase. Low-temperature annealing (Ta = 300 °C) causes rapid improvement in magnetic properties without significant changes in ε-phase, suggesting that the weakly magnetic phase is metastable. Magnetic properties remain similar until transformation of ε- to τ-phase starts in Ta range of 350 °C–450 °C. Ribbons annealed at Ta = 450 °C are made up of a homogeneous Mn-rich τ-phase. Ribbons exhibiting high Ms (maximum ~125 emu g−1) show low coercivity (Hc, maximum ~2.04 kOe), or vice versa. Highest (BH)max obtained in the present study is 1.42 MGOe. It is considerably low due to a poor squareness (Mr/Ms, Mr is the remanence) of hysteresis curve in second quadrant. Based on detailed structural and magnetic characterization, we show that the metastability of ferromagnetic MnAl phase along with the presence of Mn–Mn antiferromagnetic coupling is responsible for low (BH)max. Recoil measurements suggest that the ribbons are made from grains with a large distribution of K. This is due to the formation of τ-phase in a wide composition range (Mn ~ 50 to 60 at.%) with the highest thermal stability ~Mn55Al45. The wide distribution of K results in a low hysteresis squareness. Improvements in (BH)max require minimization of Mn–Mn antiferromagnetic interactions, narrowing of anisotropy distribution, and breakdown in intergranular exchange. The improvements in (BH)max seems difficult unless the addition of a third element is considered.

Studies of Exchange Coupling in FeCo/L10-FePt Bilayer Thin Films

FeCo/FePt bilayer thin films were synthesized by RF/dc sputtering on Si <100> substrate, and characterized for structural and magnetic properties. Synchrotron X-Ray diffraction revealed L1 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> phase of FePt and amorphous FeCo after annealing. An attempt was made to increase the strength of interfacial exchange coupling in FeCo/FePt bilayer thin films by varying the thickness of the soft layer. The in-depth analysis of reversal process at the interface was carried out using recoil curves. A giant energy product 47 MGOe was obtained for the FeCo(6 nm)/FePt(27 nm) bilayer thin film. The system was modeled by using micromagnetic simulations to visualize the magnetization reversal at the interface. Quantitative estimation of exchange energy was made and its variation with the reverse field was studied in order to understand the coupling between the hard and soft layers.

Interaction plots obtained from in-field magnetization instead of remanence measurements

The great majority of experimental studies on magnetic interactions employ a technique based on the Wohlfarth’s relation and require an initially demagnetized state. In the present work a relation analogous to that of Wohlfarth though between in-field magnetization curves instead of remanence curves is derived. This allowed to introduce interaction plots obtained via measurements of the major hysteresis loop and a recoil curve only. The method is effectively tested on three real magnetic systems which evidence different interaction effects. Although the plots introduced here seem to provide information about interactions alike the classical remanence plots, they present important advantages. These plots are acquired in an easier and faster manner and do not demand demagnetization, which significantly simplifies the measurement procedure and allows assessment of interaction effects in virtually impossible to demagnetize systems with rectangular major loops. Furthermore, this method can easily be adapted for estimation of effects leading to deviations from theoretical behavior of other hysteretic quantities.

Nanocomposite Nd-Fe-Ti-B magnets produced by melt spinning and flash annealing

We have attempted to fabricate a nanocomposite Nd-Fe-Ti-B magnet. Flash-lamp rapid annealing treatments were performed for melt-spun ribbons to obtain the α-Fe/Nd2Fe14B composite microstructure, and the evolution of magnetic properties by the annealing was studied by vibration sample magnetometer (VSM). It was found that the magnetic properties were improved by relatively short-time annealing at the temperatures near the crystallization temperature. Further higher-temperature and longer annealing treatments resulted in deterioration of the magnetic properties. For the selected samples, recoil curves were measured to analyze the spring-back behaviors. Transmission electron microscopy (TEM) was performed to investigate the microstructural factors for the deterioration of the magnetic properties. The relation between the variation of the magnetic properties (coercivity, saturation magnetization and recoil permeability) and the microstructural factors were discussed.

On the advantages of spring magnets compared to pure FePt: Strategy for rare-earth free permanent magnets following a bottom-up approach

Nanostructured magnets benefiting from efficient exchange-coupling between hard and soft grains represent an appealing approach for integrated miniaturized magnetic power sources. Using a bottom-up approach, nanostructured materials were prepared from binary assemblies of bcc FeCo and fcc FePt nanoparticles and compared with pure L10-FePt materials. The use of a bifunctional mercapto benzoic acid yields homogeneous assemblies of the two types of particles while reducing the organic matter amount. The 650°C thermal annealing, mandatory to allow the L10-FePt phase transition, led to an important interdiffusion and thus decreased drastically the amount of soft phase present in the final composites. The analysis of recoil curves however evidenced the presence of an efficient interphase exchange coupling, which allows obtaining better magnetic performances than pure L10 FePt materials, energy product above 100kJm−3 being estimated for a Pt content of only 33%. These results clearly evidenced the interest of chemically grown nanoparticles for the preparation of performant spring-magnets, opening promising perspective for integrated subcentimetric magnets with optimized properties.

Tuning Ce distribution for high performanced Nd-Ce-Fe-B sintered magnets

A dual-alloy method was applied to tune the distribution of Ce for enhancing the performance of Nd-Ce-Fe-B sintered magnets with a nominal composition of (Nd0.75Ce0.25)30.5FebalAl0.1Cu0.1B. In comparison to the single alloy of (Nd0.75Ce0.25)30.5FebalAl0.1Cu0.1B, the coercivity was enhanced from 10.3kOe to 12.1kOe and the remanence was increased from 13.1kG to 13.3kG for the magnets with a dual-alloy method. In addition, the remanence temperature coefficient α and coercivity temperature coefficient β were also slightly improved for the magnet with the dual alloys. The results of microstructure characterizations show the uniform distribution of Ce for the magnet with a single alloy, and the coexistence of the Ce-rich and Ce-lean regions for the magnet with the dual alloys. In combinations with the nucleation of reversal domains and magnetic recoil curves, the property enhancement of magnets with a dual-alloy method was well explained.

Origin of open recoil curves in L10-A1 FePt exchange coupled nanocomposite thin film

Mixed phase FePt systems with intergranular coupling may be looked upon as natural exchange spring systems. The coupling strength between the soft and hard phase in these systems can be analyzed using recoil curves. However, the origin of open recoil curves depicting the breakdown of exchange coupling or anisotropy variation in hard phase is still an ambiguity and requires an in-depth analysis. In order to investigate this, an analysis of the recoil curves for L10–A1 FePt nanocomposite thin films of varying thickness have been performed. The switching field distribution reveals that the maximum of openness of recoil curve is directly proportional to the amount of uncoupled soft phase present in the system. The coupling between the hard and soft phase is also found to increase with the thickness of the film. Monte Carlo simulations on a model three dimensional array of interacting nanomagnetic grains provide further insight into the effect of inter granular exchange interactions between the soft and hard phases.

Magnetization Reversal Processes in Pr-Fe-B-type Nanocrystalline Magnets

The magnetization reversal processes in magnets derived from rapidly solidi ed Pr9Fe52Co13Zr1Nb4B21 alloy samples were studied by analysis of minor hysteresis loops and recoil curves. The studies were carried out on suction-cast 1 mm diameter rod, 1 mm thick plate, 3 mm outer diameter (o.d.) tube and melt-spun ribbon samples subjected to annealing at 983 K for 5 min. The X-ray di raction analysis has shown multiphase constitution of the samples. Structural and magnetic studies indicated that the initial state of microstructure and phase composition a ects the magnetization reversal processes in annealed samples due to a variation of microstructure in samples of various shapes. Magnetic studies allowed estimation of the mean values of nucleation and pinning elds that control the magnetization reversal processes.

Recoil curve properties and coercive force decrease ratio in NdFeB sintered magnets

It is examined that whether a reverse domain and magnetic domain wall exist in a lower demagnetization area than the coercive force and whether the observed demagnetization ratio curve can be explained using the alignment distribution function or not. From measurements of the recoil curve in the low demagnetization field, it was confirmed that minor demagnetization occurred in every demagnetization field and magnets of every grade of coercive force. The alignment distribution of Nd2Fe14B grains was also measured by electron back-scattering diffraction (EBSD). The alignments and the coercive force decrease ratios were calculated using these alignment distributions. These data were compared against the results obtained from magnetization measurements. From EBSD data, it was found that the alignment distributions of magnets used in this experiment were close to a Gaussian distribution. It was also found that there was no difference in the alignment distribution between magnets with Dy and without Dy, even though the coercive force decrease ratios were Dy dependent. The calculated alignments using the alignment distribution functions were close to the values of magnetization measurements. However, it was found that the calculated coercive force decrease ratios were different from the results obtained from magnetization measurement.