Permanent Magnet Applications Research Articles

Influences of magnetic flux on growth and direction of Chiang Rai Phulae Pineapple roots

Currently, chemicals are widely used in plant cultivation in many countries, allowing plants to have more roots, grow faster, and increase productivity. This research aimed to study application of permanent magnets (Neodymium Magnets (NM)) to accelerate the growth of plant roots instead of using chemicals for cultivation. Pineapples were planted in liquid media under permanent magnetic flux density (B) of 1-90 mT intensity. Magnetic flux directions were arranged in two forms, either toward or ejected from the plant roots. The result showed that the number of roots of pineapples planted under the magnetic flux was 2 times greater than the control and the length of roots was also 4.5 times greater in length than those without magnetic flux. The roots exposed toward the magnetic flux had about 2 times greater number and length of roots compared to when the magnetic flux direction was ejected from the plant roots. The direction of the magnetic flux influenced the direction of plant root growth significantly.

Microstructure, magnetic and optical properties of Nb3+ and Y3+ ions co-substituted Sr hexaferrites

Series of SrNbxYxFe12-2xO19 (0.00 ≤ x ≤ 0.05) hexaferrites (HFs) were fabricated via citrate sol-gel approach. Structural and magneto-optical properties of ensembles were investigated in detail. The structural and morphological analyses revealed the formation of M-type Sr hexaferrite nanoparticles. Diffuse reflectance data were registered to estimate the direct optical energy band gaps (Eg) in a range of 1.77 eV-1.87 eV. Room temperature (RT, 300 K) and low temperature (10 K) magnetic hysteresis curves were recorded by enforcing applied dc magnetic field up to ±70 kOe. Magnetic parameters were significantly tuned due to coordination of Nb3+ and Y3+ rare earth ions. Specified magnetic data reveal the strong ferromagnetic characteristics of pristine SrFe12O19 and co-doped HFs with Nb3+ and Y3+ ions at both temperatures. RT squareness ratio (SQR) has an exception only for pristine sample as 0.506, which is in the margin of theoretical limit assigning the single-domain nature with uniaxial anisotropy. However, all co-doped samples have SQR = 0.288–0.485 values that are smaller than theoretical limit of 0.50, implying multi-domain nature at RT and at 10 K. Co-doped ions cause lowering in super-exchange interactions between different sites and resulting the decrements of intrinsic magneto-crystalline anisotropy and coercivity fields. The specified magnetic characteristics make our fabricated SrNbxYxFe12-2xO19 (0.00 ≤ x ≤ 0.05) HFs good candidates as permanent magnets applications and high-density recording media.

Chemical Synthesis of Magnetic Nanoparticles for Permanent Magnet Applications.

Permanent magnets are a class of critical materials for information storage, energy storage, and other magneto-electronic applications. Compared with conventional bulk magnets, magnetic nanoparticles (MNPs) show unique size-dependent magnetic properties, which make it possible to control and optimize their magnetic performance for specific applications. The synthesis of MNPs has been intensively explored in recent years. Among different methods developed thus far, chemical synthesis based on solution-phase reactions has attracted much attention owing to its potential to achieve the desired size, morphology, structure, and magnetic controls. This Minireview focuses on the recent chemical syntheses of strongly ferromagnetic MNPs (Hc >10 kOe) of rare-earth metals and FePt intermetallic alloys. It further discusses the potential of enhancing the magnetic performance of MNP composites by assembly of hard and soft MNPs into exchange-coupled nanocomposites. High-performance nanocomposites are key to fabricating super-strong permanent magnets for magnetic, electronic, and energy applications.

Prediction of improved magnetization and stability in Fe16N2 through alloying

We study the structural, energetic, electronic, and magnetic properties of Fe16 − xMxN2 alloys, where M represents 3d transition metals Ti, V, Cr, Mn, Co, and Ni, using special quasirandom structures and density functional theory calculations. We describe stabilization of Fe16N2 resulting from the enhanced occupation of bonding states relative to the corresponding antibonding states as observed from crystal orbital Hamiltonian population analysis. The hybrid HSE06 functional is employed to calculate a magnetic moment of 2.844 μB/Fe, agreeing with recent experimental work and suggesting the importance of electronic exchange effects. Upon alloying, magnetization is found to decrease with all transition metals excluding Mn, for which exceptionally strong ferromagnetic coupling is achieved via nitrogen-mediated exchange interactions. We identify a 1.41% magnetization increase at low Mn concentrations coupled with a decrease in formation energy, making Fe16 − xMnxN2 a suitable candidate for permanent magnet applications. Novel end-member systems of the form M16N2 are also investigated, with results implying stability and potential synthesizability of all compounds except Ti16N2 owing to weak metallic bonding among Ti atoms.

A Flame-Reaction Method for the Large-Scale Synthesis of High-Performance Smx Coy Nanomagnets.

We report a flame-reaction method to synthesize high-performance Smx Coy (x=1, y=5; x=2, y=17) particles on a multigram scale. This flame reaction allows the controlled decomposition of Sm(NO3 )3 and Co(NO3 )2 to 320 nm SmCo-O (SmCoO3 + Co3 O4 ) particles. A 5.8 g sample of SmCo3.8 -O particles was coated with CaO and then reduced at 900 °C by Ca to give 4.2 g of 260 nm SmCo5 particles. The SmCo5 particles are strongly ferromagnetic and the aligned particles in epoxy resin exhibit a large room-temperature coercivity (Hc ) of 41.8 kOe and giant (BH)max (maximum magnetic energy product) of 19.6 MGOe, the highest value ever reported for SmCo5 made by chemical methods. This synthesis can be extended to synthesize Sm2 Co17 particles, providing a general approach to scaling up the synthesis of high-performance Smx Coy nanomagnets for permanent magnet applications.

Experimental investigation of effects of magnetic field on performance, combustion, and emission characteristics of a spark ignition engine

AbstractThis article presents a comprehensive experimental work for the application of permanent magnets with the intensity of 9,000 G to a four‐stroke four cylinders gasoline engine on fuel lines at a location near to the combustion chamber. By using the permanent magnet, the liquid fuel disintegrates into small diameter, and de‐clustering of the fuel molecules of hydrocarbon has been proved to provide better atomization of the fuel, which makes sure that the fuel strenuously combines with oxygen and results in complete and more efficient burning process inside the combustion chamber. The experimental analysis revealed that magnetic treatment has improved performance and emission characteristics. Analysis over the engine test results with magnetic fuel conditioning showed that the reduction of 4–12% in fuel consumption and reduction in 11, 10, 18, and 10% for CO, CO2, HC, and NOx emissions, respectively, compared to gasoline fuel without magnetic condition. Further, we experimentally investigated the performance of petrol engine parameters such as in‐cylinder temperature and pressure, cylinder, and head cylinder temperature, the temperature of different parts of the piston. As a whole, magnetic fuel treatment has improved combustion and reduced the harmful pollutants of the compression ignition engine.

Effects of synthesis route on the structural and magnetic properties of Sr1-xRExFe12O19 nanocrystalline hexaferrites

The present study is concerned with the synthesis and characterization of rare-earth-doped SrM (Sr1-xRExFe12O19) hexaferrites (RE = La, Ce and Tb; x = 0, and 0.1). The hexaferrite precursor powders were prepared by high-energy ball-milling and sol–gel auto-combustion methods, and the powders were sintered at temperatures ≥ 900 °C. The effects of RE substitution and synthesis route on the structural and magnetic properties of SrM hexaferrites were investigated by X-ray diffraction, scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). Single SrM phase was obtained in the sample with x = 0, and the sample with La substitution was prepared by ball-milling method. The rest of the samples, however, contained small amounts of minor phases of rare-earth oxides and α-Fe2O3 in addition to the major SrM phase. SEM imaging revealed significant decrease in particle size with RE substitution. Also, VSM measurements revealed small decrease in the saturation magnetization, and a significant increase in the coercivity with RE substitution. Comparable saturation magnetization was observed for the samples prepared by sol–gel method, whereas the coercivity increased significantly. The coercivity of samples prepared by sol–gel method exhibited a large increase with the decrease in sintering temperature, reaching ~ 6.2 kOe for the samples with Ce- and Tb-substituted samples sintered at 900 °C. The relatively high remnant magnetization (~ 30–35 emu/g) and high coercivity make these materials important candidates for permanent magnet applications.

First-Principles Prediction of Possible Rare-Earth Free Permanent Magnet of Tetragonal FeCo with Enhanced Magnetic Anisotropy and Energy Product through Interstitial Nitrogen

Permanent-magnet applications such as electric motors demand a high energy product (simultaneously high saturation magnetization and uniaxial magnetic anisotropy) and Curie temperature, preferably in $3d$ metals without any rare-earth elements. The authors' first-principles calculations highlight a promising pathway to achieving these properties in $B2$-ordered FeCo alloy, by interstitial doping with $2p$-electron nonmetal elements, such as N. This prediction could have real impact on the manufacturing of practical, rare-earth-free, high-performance permanent magnets.

Structure and magnetic properties of W-type hexaferrites.

W-type hexaferrites (WHFs) (SrMe 2Fe16O27, Me = Mg, Co, Ni and Zn) are hard magnetic materials with high potential for permanent magnet applications owing to their large crystalline anisotropy and high cation tunability. However, little is known with regards to their complex structural and magnetic characteristics. Here, the substitution of metals (Me = Mg, Co, Ni and Zn) in WHFs is described and their crystal and magnetic structures investigated. From joined refinements of X-ray and neutron powder diffraction data, the atomic positions of the Me atoms were extracted along with the magnetic dipolar moment of the individual sites. The four types of WHFs exhibit ferrimagnetic ordering. For Mg, Ni and Zn the magnetic moments are found to be ordered colinearly and with the magnetic easy axis along the crystallographic c axis. In SrCo2Fe16O27, however, the spontaneous magnetization changes from uniaxial to planar, with the moments aligning in the crystallographic ab plane. Macromagnetic properties were measured using a vibration sample magnetometer. The measured saturation magnetization (M s) between the different samples follows the same trend as the calculated M s extracted from the refined magnetic moments of the neutron powder diffraction data. Given the correlation between the calculated M s and the refined substitution degree of the different Me in specific crystallographic sites, the agreement between the measured and calculated M s values consolidates the robustness of the structural and magnetic Rietveld model.

Initial Irreversible Losses and Enhanced High‐Temperature Performance of Rare‐Earth Permanent Magnets

AbstractThere is an increasing demand for permanent magnets with high‐temperature stability. Normally, the magnets are heat treated above the operating temperature range to saturate the irreversible losses, thereby producing magnets that are stable, but with significantly degraded performance. In addition, uncertainty about the losses in differently shaped magnets causes difficulties for efficient magnetic circuit design. The variation of the initial irreversible losses with magnet shape, hysteresis loop, and operating temperature is presented here. Losses are not associated with thermal demagnetization of the whole magnet, but the damage is concentrated in an outer surface “skin” at the pole surfaces, where the demagnetizing field is nonuniform. The initial irreversible remanence loss at room temperature can be predicted as the product of the slope of the high‐temperature magnetization curvek(T) and the effective demagnetizing factor . Heat treatment with the vulnerable surfaces in contact with soft iron slabs moves the skin out of the permanent magnet and reduces the irreversible remanence loss by 30% or more, potentially improving the performance of permanent‐magnet motors, generators, bearings, and thrusters. The results deepen the understanding of the magnetism of irreversible losses and will guide the applications of permanent magnets at higher temperatures.

Fabrication of MnBi alloys with high ferromagnetic phase content: effects of heat treatment regimes and dopants

The low-cost and rare-earth-free MnBi alloys were focused for investigation during last 5 years as a promising alternative for high-cost rare-earth-containing Nd–Fe–B in high-temperature permanent magnet applications. Because of the peritectic nature of solidification, MnBi alloys containing high ferromagnetic phase content could not be easily prepared for massive scale. In this paper, the roles of heat treatment regimes including the zone-travelling under temperature gradient, multi-time annealing (MTA) and the doping soft ferromagnetic Fe65Co35 phase in preparing MnBi alloys with high ferromagnetic phase content were investigated. The results showed that, for the case of applying the temperature gradient assisted zone-travelling technique, the ferromagnetic phase content in prepared alloys reached 85 wt%. By using the MTA technique, the ferromagnetic phase content is raised up 96 wt% when MnBi alloys were annealed three times at 300 °C for 20 h. The doping of Fe65Co35 as a soft ferromagnetic phase stabilized the ferromagnetic phase in the obtained MnBi1−x(Fe65Co35)x alloys (x = 0.1, 0.2, 0.3) with the magnetization measured at 13.5 kOe of 63.1, 70.8 and 80.5 emu/g, respectively.

High-quality CoFe2O4 thin films with large coercivity grown via a wet chemical route

In permanent magnet applications, response often scales with volume or dimension in power-conversion and magnetostrictive applications, even in film form. In microelectromechanical devices it is necessary to explore versatile methods of dense film deposition with film thicknesses approaching one micron. In this study, we present a wet chemical route to hard magnetic cobalt ferrite (CoFe2O4) films to produce films with large coercivity, controllable thickness, saturation approaching that of the bulk, and smoother morphology than state-of-the art sputtered or pulsed-laser-deposited films. The development of etching and releasing processes demonstrates how these films are suitable for precise engineering in a variety of form factors and applications.

MnBi thin films for high temperature permanent magnet applications

Thin films of ferromagnetic LTP-MnBi (Low Temperature Phase of MnBi) have been grown by magnetron sputtering onto quartz substrates. Two particular issues related to LTP-MnBi have been investigated: the strong influence of the growth temperature and the degradation of magnetic properties in time. The temperature dependence on the magnetic, morphological and microstructural properties has been investigated, evidencing drastic changes on the properties of MnBi with small temperature variations. By inducing a gradient of temperature during the growth, two well differentiated regions with different morphology and crystal structure have been observed in a MnBi film sample. On the other hand, aging experiments performed in a different LTP-MnBi sample has led to a notable decrease of 54% in the saturation magnetization after 6 days and a complete loss of ferromagnetic response after 4 months.

Exchange Bias in Bulk Nanocomposites for Permanent Magnet Applications.

Here we report on the microstructural factors influencing the formation of the interfacial exchange bias effect in three-dimensional transition-metal-based nanocomposite systems, with relevance to permanent magnet applications. Bulk phase-separated nanocomposites consisting of the ferromagnetic -Fe and metastable antiferromagnetic phases exhibit a notable low-temperature exchange bias and substantial coercivity ( , ) as well as a near room-temperature blocking temperature. Structural investigation by synchrotron X-ray diffraction, neutron scattering, and transmission electron microscopy confirm that the ferromagnetic -Fe phase nucleates as small precipitates ( ) at the grain boundaries of the antiferromagnetic grains ( ) and grows anisotropically upon heat treatment, resulting in an elliptical geometry. These results indicate that optimization of the exchange bias effect in bulk nanocomposite systems may be achieved through maximizing the surface-to-volume ratio of ferromagnetic precipitates in an antiferromagnetic matrix, enhancing the magnetocrystalline anisotropy of the antiferromagnetic phase to facilitate interfacial pinning and ensuring a balanced distribution of the ferromagnetic and antiferromagnetic phases. This work further clarifies critical factors influencing the formation of an exchange bias in an inexpensive transition-metal-based bulk nanocomposite system with potential for scalable production.

Annealing effect on structural, microstructural and magnetic properties of nanocrystalline Er-Co-B alloys for permanent magnet applications

Abstract In this paper, we have examined the structural, microstructural, and magnetic properties of Er-Co-B compounds. High-energy ball milling has been used to homogeneous the stoichiometric mixture of Er, Co and B as starting materials to synthesis the Er17Co75B8 powders. The samples are crystallized in the hexagonal CaCu5 - structure type with P6/mmm space group. Their structural and magnetic properties were assumed systematically as a function of annealing temperature. The structural properties were studied by means of X-ray diffraction and the microstructural properties via Scanning Electron Microscopy. The magnetic phase with abbreviated formula ErCo4.5B0.5 and global formula Er16.67Co75B8.33 was a dominate phase. These compounds exhibit a high coercivity of 8 kOe at room temperature for ErCo4.5B0.5 annealed at 1073 K for 1/2 h. These magnets with high HC are appropriate to permanent magnet applications. We have also applied to the Approach of Saturation in to Magnetization (ASM). The results were understood in according to the model of random magnetic anisotropy.

Emergence of coercivity in Sm(Fe0.8Co0.2)12 thin films via eutectic alloy grain boundary infiltration

The anisotropy field of the ThMn12-type Sm(Fe0.8Co0.2)12 compound is high. However, there is an absence of reports on sufficiently high coercivity for anisotropic permanent magnet application. In this study, we employed the grain boundary diffusion process to anisotropic Sm(Fe0.8Co0.2)12 thin films. As-grown (001)-textured nanocrystalline film exhibit a coercivity of only 0.4 T. However, the grain boundary diffusion process via a Cu-Ga capping layer increases coercivity to 0.8 T. The coercivity exhibits relatively low temperature dependence when compared to that of Nd-Fe-B magnets.

Experimental Verification of Force and Stiffness Between Two Ring Magnets Calculated by Monte Carlo Integration Technique

This paper presents the calculation and experimental verification of force and stiffness between two concentric ring-shaped rare earth magnets. This kind of magnet configuration is invariably used in magnetic bearing, micromass measurement system, turbomachineries and space applications. Estimation of magnetic force and stiffness is always important in any application of permanent magnet as it influences the stability and performance of the system. Some analytical methods are available which involve direct solution of elliptic integral, which made the calculation tedious, complex, time- and space consuming. In this work, a simple approach based on Monte Carlo integration technique is proposed to calculate the force and stiffness. Monte Carlo integration technique is preferred to calculate the multidimensional elliptic integrals due to simplicity of the method, less computational time and memory requirement. The result is compared with existing finite element method and verified with experimental result. The verification process indicates that there is a small deviation in result of the proposed method from experimentally obtained result, but taking into account simplicity, space and time requirement, this approach may be considered to be a useful alternative method to calculate force and stiffness of a magnetic system. The proposed method is one of the best examples of utilizing an old computational concept in modern complicated problem solution.

Nitrogenation and sintering of (Nd-Zr)Fe10Si2 tetragonal compounds for permanent magnets applications

Nd-xZrxFe10Si2 alloys have been prepared in the tetragonal ThMn12-type structure by arc-melting and melt spinning and then nitrogenated to improve their magnetic properties. For x = 0.4 and 0.6 the Curie temperature and magnetic anisotropy fields increases from 280 to 300 °C to about 390 °C and from 2.8 to 3 Tesla to 4.5–5 Tesla respectively. The saturation magnetization remains almost unchanged. The nitrogenated powders were processed by Spark Plasma Sintering (SPS) leading to compact pellets, which retain the full Nitrogen content and magnetic properties up to 600 °C, but segregated Fe-Si at elevated temperatures. Nitrogenation and SPS processing are, therefore, appropriate for sintering metastable materials such as (NdZr)Fe10Si2 into compact material without loosing functional properties. This opens a way towards a new family of permanent magnets, lean of critical raw materials.

Synthesis, processing and characterization of Mn-based nanoparticles for permanent magnet applications

Synthesis, processing and characterization of Mn-based nanoparticles for permanent magnet applications

Magnetocrystalline anisotropy of Fe5PB2 and its alloys with Co and 5d elements: A combined first-principles and experimental study

The Fe$_5$PB$_2$ compound offers tunable magnetic properties via the possibility of various combinations of substitutions on the Fe and P-sites. Here, we present a combined computational and experimental study of the magnetic properties of (Fe$_{1-x}$Co$_{x}$)$_5$PB$_2$. Computationally, we are able to explore the full concentration range, while the real samples were only obtained for 0 <= x <= 0.7. The calculated magnetic moments, Curie temperatures, and magnetocrystalline anisotropy energies (MAEs) are found to decrease with increasing Co concentration. Co substitution allows for tuning the Curie temperature in a wide range of values, from about six hundred to zero kelvins. As the MAE depends on the electronic structure in the vicinity of Fermi energy, the geometry of the Fermi surface of Fe$_5$PB$_2$ and the k-resolved contributions to the MAE are discussed. Low temperature measurements of an effective anisotropy constant for a series of (Fe$_{1-x}$Co$_{x}$)$_5$PB$_2$ samples determined the highest value of 0.94 MJ m$^{-3}$ for the terminal Fe$_5$PB$_2$ composition, which then decreases with increasing Co concentration, thus confirming the computational result that Co alloying of Fe$_5$PB$_2$ is not a good strategy to increase the MAE of the system. However, the relativistic version of the fixed spin moment method reveals that a reduction in the magnetic moment of Fe$_5$PB$_2$, by about 25%, produces a fourfold increase of the MAE. Furthermore, calculations for (Fe$_{0.95}$X$_{0.05}$)$_5$PB$_2$ (X = 5$d$ element) indicate that 5% doping of Fe$_5$PB$_2$ with W or Re should double the MAE. These are results of high interest for, e.g., permanent magnet applications, where a large MAE is crucial.