Magnetization Of Nd Research Articles

Electrochemical routes for environmentally friendly recycling of rare-earth-based (Sm–Co) permanent magnets

The consumption of critical raw materials, especially those in permanent magnets of Nd–Fe–B and Sm–Co-type, has significantly grown in the past decade. With predictions on further electrification growing exponentially the demand for these materials will even increase. This implies that efforts in assuring sustainability must involve recycling from secondary resources. In recent years the electrochemical approaches in recycling have been extensively investigated and applied owing to their advantages of high efficiency and selectivity, easy operation, low energy consumption, and environmental friendliness. In this paper, we investigate the Sm2(Co,Fe,Cu,Zr)17 permanent magnet leaching process using the anodic oxidation to be paired with the metal deposition on the cathode. Linear sweep voltammetry was performed from − 0.15 to 1 V versus Pt quasi reference electrode that indicated current peaks that would correspond to some preferential leaching of the crystal phases contained in the magnet. The latter was confirmed using the SEM/EDXS analysis. The continuous leaching of the Sm2(Co,Fe,Cu,Zr)17 magnet was performed at a direct current density of 2, 4 and 8 mA cm−2 at the time period of 0–240, 240–480 and 480–720 min, respectively. The ICP-MS results confirmed the leaching of all the metals from the original Sm2(Co,Fe,Cu,Zr)17 permanent magnet. The concentration of Sm3+, Cu2+, Fe2+ and Zr2+ increases linearly along with the leaching time. Reversely the concentration of Co2+ decreases linearly due to its consumption by electrodeposition of Co, Fe and Cu on the cathode. The presented paired electrochemical process could serve as a starting point for the recycling and recovery of critical raw materials without any acid usage and waste generation.Graphical abstract

Effects of Nd concentration on structural and magnetic properties of ZnFe2O4 nanoparticles

Zinc ferrite nanomaterials have been received significant attention in recent years on account of their potential applications in the fields of electronics, optoelectronics and magnetics. To enhance the magnetic properties of zinc ferrites, Nd-doped zinc ferrites (ZnFe2−xNdxO4, x = 0, 0.01, 0.02, 0.03) nanoparticles (NPs) have been prepared by the sol–gel method. The effects of Nd doping concentration on the structural and magnetic properties of zinc ferrites were studied. The results of X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy indicated that the Nd ions were incorporated into the crystal lattice of ZnFe2O4 and substituted for the Fe3+ sites. Unlike pure zinc ferrites with paramagnetism, Nd doped ZnFe2O4 NPs were superparamagnetic at room temperature. Vibrating sample magnetometry results showed, with the increase of Nd content, the saturation magnetization of Nd doped ZnFe2O4 NPs increased.

Connection of Thermopower, Magneto Thermopower with Resistivity and Magnetoresistivity in Nd<sub>(1-x)</sub>Sr<sub>x</sub>MnO<sub>3</sub> and Sm<sub>(1-x)</sub>Sr<sub>x</sub>MnO<sub>3</sub> Manganites

An experimental study of thermopower, magneto thermopower, magnetoresistivity and magnetization of Nd(1-x)SrxMnO3 and Sm(1-x)SrxMnO3 with 0 ≤ х ≤ 0.3 was conducted. A steep rise of thermopower as well as giant values of magneto thermopower and magnetoresistivity were observed near Curie temperature ТС in compounds with 0.15 ≤ х ≤ 0.3. On the other hand, no special features were found in case of х = 0. It has been known that compounds with 0.1 ≤ х ≤ 0.3 consist of ferromagnetic clusters of ferron (magnetic polaron) type located in A-type antiferromagnetic matrix. An increase of thermopower near ТС is caused by ferrons as with the application of magnetic field or temperatures higher than ТС thermopower falls sharply due to the destruction of ferrons. So, the value of thermopower is directly connected to the number of magnetic polarons in sample. Therefore, thermopower in doped magnetic semiconductors is determined by level of doping and volume of the sample.

Controlling of Saturation of Magnetization of Nd–Fe–B Nanoparticles Fabricated by Chemical Method

Nd–Fe–B oxide powders with various size distributions and structures were prepared using nitrite-based metal salts including Nd2O3, Fe(NO3)3⋅9H2O, HNO3, H3BO3, citric acid (CA), and ethylene glycol (EG) by a Pechini-type sol–gel method. Mixed oxide powders were obtained by calcination and annealing the gels. These oxides by using a reduction–diffusion process under vacuum and employing CaH2 as a reducing agent at 800 ∘C were heated to prepare Nd2Fe14B nanoparticles. The role of different EG/metal salt molar ratios on phase, morphologies, microstructure, and magnetic properties of the powders were investigated by employing XRD, FE-SEM, TEM, and VSM techniques, respectively. The results show that with an increase in EG/metal salt molar ratio, the average particle size of Nd–Fe–B oxide powders increased while the coercivity of Nd–Fe–B oxide powders decreased. The presence of excess EG/CA/metal salt molar ratio, from 2:2:1 to 50:2:1, played a role of a space-filling template or capping agent and helped initial oxide particles embedded in the gel matrix to grow as sheet-like particles. Nd2Fe14B nanoparticles can successfully be synthesized by increasing the EG/CA/metal salt molar ratio from 2:2:1 to 50:2:1. The reduced samples made of nitrite-based metal salts with a EG/CA/metal salt molar ratio of 50:2:1 had a saturation magnetization of 123 emu/g and a coercivity of 315 Oe. By controlling the ratio of precursors, the hard-phase Nd2Fe14B could be successfully synthesized.

Magnetism of Nd–Fe films as a model of grain boundary phase in Nd–Fe–B permanent magnets

To clarify the magnetism of an amorphous grain boundary (GB) phase in Nd–Fe–B sintered magnets, the magnetic properties of Nd100−xFex films with various compositions have been investigated both experimentally and theoretically. The model films exhibit ferromagnetism at room temperature when the Nd content is lower than 70 at. %. First-principles calculations indicate ferromagnetism in fcc Nd–Fe alloys for x < 70, which supports recent experimental works on the intergrain exchange coupling of Nd–Fe–B sintered magnets.

ВЛИЯНИЕ СОДЕРЖАНИЯ МЕДИ НА ФАЗОВЫЙ СОСТАВ И МАГНИТНЫЕ СВОЙСТВА ТЕРМОСТАБИЛЬНЫХ СПЕЧЕННЫХ МАГНИТОВ СИСТЕМ Nd–Dy–Fe–Co–B И Pr–Dy–Fe–Co–B

ВЛИЯНИЕ СОДЕРЖАНИЯ МЕДИ НА ФАЗОВЫЙ СОСТАВ И МАГНИТНЫЕ СВОЙСТВА ТЕРМОСТАБИЛЬНЫХ СПЕЧЕННЫХ МАГНИТОВ СИСТЕМ Nd–Dy–Fe–Co–B И Pr–Dy–Fe–Co–B

Design of a vibration isolation system using eddy current damper

This article aims at modeling, analysis and design of a passive vibration isolation system using a magnetic damper with high efficiency and compactness. The experimental set-up was developed for a single degree-of-freedom vibration isolation system, where the damper consists of two elements: an outer stationary conducting tube made up of copper and a moving core made up of an array of three ring-shaped neodymium magnets of Nd–Fe–B alloy separated by four block cylinders made of mild steel that are fixed to a steel rod. The generation of eddy currents in the conductor and its resistance causes the mechanical vibration to dissipate heat energy. The vibration response of the system is obtained starting from a low-frequency range. The proposed magnetic damper achieves a maximum transmissibility value less than two for a natural frequency that is less than 10 Hz and the excitations at higher frequencies are successfully isolated. Numerical and experimental studies were carried out for a range of system parameters which show that isolators based on magnetic damping could be very effective for passive vibration isolation. Further, a theoretical model for an active isolation system is proposed in order to reduce the transmissibility at resonance. It is envisaged that the combined active–passive eddy current damper could be effectively used for vibration isolation.

Microstructure, magnetic and electrical properties of the composite magnets of Nd–Fe–B powders coated with silica layer

A novel type of composite magnet was fabricated by hot pressing and hot deformation of Nd–Fe–B powders coated with a continuous silica layer. Nd–Fe–B powders were coated with a silica insulating layer of various thicknesses by chemical synthesis. The influence of the thickness of the insulating layer on the microstructure, magnetic and electrical properties was investigated. The coated silica layer was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The synthesized layer with a thickness of 18–101nm uniformly coated the Nd–Fe–B powders. There is no significant decrease for the maximum energy product (BH)max when the average thicknesses of the insulating layers were 24 and 45nm and the electrical resistivity increased from 230μΩcm without silica coating to 260 and 280μΩcm, respectively. The (BH)max of the composite magnet decreased to 30.7MGOe when the average thickness of the insulating layer was approximately 64nm, while the electrical resistivity increased to 280μΩcm. Thus, the thickness of SiO2 layer is an important factor for the magnetic and electrical properties of the composite magnets. The SiO2 layers deteriorated the magnetic properties in different levels. The reason may be that atom diffusion happened during the hot-deformation process.

4fhybridization effect on the magnetism of Nd2PdSi3

Among the members of the series R2PdSi3 (R= Rare-earths), the magnetic behavior of the Nd compound is interesting in some respects. This compound is considered to order ferromagnetically (below 16 K), unlike other members of this series which order antiferromagnetically. In addition, magnetic ordering temperature (To) is significantly enhanced with respect to de Gennes scaled value. In order to understand the magnetism of this compound better, we have investigated the magnetic behavior in detail (under external pressure as well) and also of its solid solutions based on substitutions at Nd and at Si sites, viz., on the series, Nd(2-x)(Y,La)(x)PdSi(3-y)Ge(y) (x, y= 0.2, 0.4, 0.8, and 1.2) by bulk measurements. The results overall establish that Nd2PdSi3 orders ferromagnetically below 16 K, but antiferromagnetic component seems to set in at very low temperatures. Notably, there is a significant suppression of To for Y and Ge substitutions, compared to La substitution, for a given magnitude of unit-cell volume change, however qualitatively correlating with the separation between the layers of Nd and Pd-Si(Ge). On the basis of this observation, we conclude that 4f(Nd) hybridization plays a major role on the magnetism of the former solid solutions. To our knowledge, this work serves as a rare demonstration of 4f-hybridization effects on the magnetism of a Nd-based intermetallic compound.

Structure and magnetization studies of Nd 0.5− xPr xSr 0.5MnO 3 system

The structural and magnetic properties of Nd 0.5− x Pr x Sr 0.5MnO 3 ( x=0, 0.1, 0.2, 0.3, 0.4 and 0.5) system have been investigated. With the substitution of Pr in Nd 0.5Sr 0.5MnO 3, it shows a gradual structure transformation from the Imma orthorhombic symmetry to the tetragonal I4/mcm phase, and the crystallographic transition remains incomplete, even in Pr 0.5Sr 0.5MnO 3. A large bifurcation between zero-field-cooled (ZFC) and field-cooled (FC) susceptibility has been observed below Curie temperature ( T C), which is characteristic of coexistence of ferromagnetism (FM) and antiferromagnetism (AFM) at low temperature region. The magnetization of Pr 0.5Sr 0.5MnO 3 is larger than that of Nd 0.5Sr 0.5MnO 3, while Nd 0.5Sr 0.5MnO 3 with more CE-type AFM shows larger magnetization than Nd 0.3Pr 0.2Sr 0.5MnO 3, which mixed with CE-type (majority) and A-type (minority) AFM at low temperature, indicating that the magnetization of Nd 0.5− x Pr x Sr 0.5MnO 3 system is affected by A-site disorder combined with orbital ordering of A-type AFM and CE-type AFM.

Effect of magnetic field on Nd 0.7Pb 0.3MnO 3 single crystal

Magnetization and specific heat of Nd 0.7Pb 0.3MnO 3 single crystal are studied at applied magnetic field. Magnetization measurement at 0.3 T shows ferromagnetic phase below 150 K ( T C ) and below 20 K displays an antiferromagnetic component. The latter appears to be destroyed at 4.8 T. This anomalous increase below 50 K is probably due to reorientation of Nd moments at high magnetic field. Heat capacity has been measured at 0–10 T at low temperature. The data have been fitted to contributions from free electrons ( γ), ferromagnetic spin excitations ( β 3/2), lattice and a Schottky-like anomaly related to the rare-earth magnetism of the Nd ions. Fitting yields that β 3/2 term is very small at 6 and 10 T because of introducing paramagnetic component in ferromagnetic phase at applied magnetic field. Peak due to Schottky anomaly is observed to be broadened with application of magnetic field and the magnitude of Schottky gap( Δ Sch ) also increases accordingly.

Critical behavior studies in ferromagnetic (Nd, K)–Mn–O compounds

The critical scaling behavior of K-doped Nd–Mn–O based double-exchange ferromagnetic compounds was studied by measuring isothermal magnetization of Nd 0.84K 0.16MnO 3 and Nd 0.77K 0.23MnO 3 samples. The critical exponents β, γ and δ corresponding to the spontaneous magnetization, initial susceptibility and isothermal magnetization, respectively, were determined by analyzing the magnetization data in terms of the modified Arrott plot method. The critical exponent values of both samples are found to be comparable to values predicted by a mean field model. The role of ferromagnetic clusters on the scaling behavior is discussed. The critical exponent values are found to be consistent with the Widom scaling relation and the universal scaling hypothesis.

Crystal structure and magnetic properties of Nd(Mn1–xFex)2Si2 compounds

X-ray powder diffraction, resistivity and magnetization studies have been performed on polycrystalline Nd(FexMn1–x)2Si2 (0 ≤ x ≤ 1) compounds which crystallize in a ThCr2Si2-type structure with the space group I4/mmm. The field-cooled temperature dependence of the magnetization curves shows that, at low temperatures, NdFe2Si2 is antiferromagnetic, while the other compounds show ferromagnetic behaviour. The substitution of Fe for Mn leads to a decrease in lattice parameters a, c and unit-cell volume V. The Curie temperature of the compounds first increases, reaches a maximum around x = 0.7, then decreases with Fe content. However, the saturation magnetization decreases monotonically with increasing Fe content. This Fe concentration dependent magnetization of Nd(FexMn1–x)2Si2 compounds can be well explained by taking into account the complex effect on magnetic properties due to the substitution of Mn by Fe. The temperature's square dependence on electrical resistivity indicates that the curve of Nd(Fe0.6Mn0.4)2Si2 has a quasi-linear character above its Curie temperature, which is typical of simple metals.

Fine pole-pitch magnetizing method for Nd–Fe–B isotropic magnet with high coercivity

Fine pole-pitch magnetization of Nd–Fe–B magnets is an important technology that contributes to miniaturization of electromagnetic devices and smaller fractional movement. However, as Nd–Fe–B magnets have a high coercivity, large amounts of energy are required for magnetization. Miniaturization of devices is associated with insufficient magnetization characteristics due to the limitations of current density. We developed a magnetization method using heating system. This method involves cooling in the magnetizing field by permanent magnets after rapid heating to temperatures above the Curie point of the Nd–Fe–B magnet. This method, which we named “ultra high magnetizing (UHM) process,” achieved greater magnetization characteristics than conventional technology. Therefore, the UHM process is a useful technology to achieve further miniaturization of electromagnetic devices.

High magnetic-field study of the magnetization of layered manganite Nd 2−2 xSr 1+2 xMn 2O 7 single crystals

The magnetization of Nd 2−2 x Sr 1+2 x Mn 2O 7 layered manganite single crystals (with x=0.5, 0.4, 0.25) has been studied using high magnetic fields up to 30 T at 4.2 K. In these compounds, which are antiferromagnetic at low temperatures, induced metamagnetic transitions have been observed. These transitions become very sharp for doping level values in the range x=0.25–0.4, reaching saturation-like behavior and displaying a large hysteresis. Maximum field magnetization is much lower than expected for the full ferromagnetic configuration of the Nd and Mn moments, and a large high field susceptibility is observed beyond the transition. The observed magnetization at maximum field within the ab-plane is lower (up to a 17%) than along the c direction. However, the value of the critical magnetic field of the transition is in all the cases larger for the magnetization within ab than along c. These transitions have been ascribed to spin-flipping within the Mn moment sublattice.

Phase transformation, structure and magnetic properties of Nd–Fe–B–V alloys and their nitrides prepared by mechanical alloying

The structure and magnetic properties of mechanically alloyed (MA) Nd 10Fe 76B 8− x V 6+ x series and their nitrides have been studied. With increasing V content, the magnetic main phase of Nd 10Fe 76B 8− x V 6+ x series changes from the magnetic phase of Nd 2Fe 14B-type structure via a metastable Nd(Fe,V) 7 phase with TbCu 7 structure to Nd(Fe,V) 12 phase with ThMn 12 structure. The easy in-plane magnetization of Nd(Fe,V) 7 and Nd(Fe,V) 12 phases results in rather poor permanent magnetic properties. The V-containing Nd 2Fe 14B-type phase is partly decomposed upon nitrogenation. Because nitrogen enters into the interstitial sites of the TbCu 7-type and ThMn 12-type structures, their Curie temperatures are greatly enhanced. The easy magnetization of Nd(Fe,V) 7 with TbCu 7, like Nd(Fe,V) 12 with ThMn 12 structure, changes from easy in-plane to easy c-axis after nitrogenation.

Magnetization measurements on Nd 1−xBa 2+xCu 3O 7 thin films

We have measured the magnetization of Nd 1−xBa 2+xCu 3O 7 (x≈0.1) thin films by SQUID at different applied magnetic fields and temperatures. Both the field cooled and zero field cooled of the magnetization were measured. We found that rather than a diamagnetic response, a paramagnetic behavior which resembles those observed by other groups on BSCCO and YBCO single crystals was observed in the field cooled measurements. The origin of such a paramagnetic response is being discussed.

143Nd NMR study of 3d and 4f magnetism in Nd 2(Fe 1−xCo x) 14B and Nd 2(Fe 1−yNi y) 14B

A systematic NMR study of the effects of Co and Ni substitutions on the 143Nd hyperfine fields in Nd 2(Fe 1−xCo x) 14B and Nd 2(Fe 1−yNi y) 14B has been carried out by the spin-echo method in zero external magnetic field. The substitution of Co for Fe leads that the hyperfine field first decreases and then increases, while the substitution of Ni for Fe brings about a significant reduction of the hyperfine field. This decrease, however, is recovered by further substitution of Co for Fe in the Nd 2(Fe 1−yNi y) 14B. An analysis of the Nd hyperfine field based on the saturation magnetization of Nd 2(Fe 1−xCo x) 14B and Nd 2(Fe 1−yNi y) 14B compounds leads to a conclusion that the Nd magnetic moment averaged over the f and g sites in the latter is reduced to 2.9 μ B for y=0.1 from 3.0 μ B for y=0.

High field magnetization of Nd 2CuO 4

High field magnetization of Nd 2 Cu0 4 single crystal is investigated and the spin-flop and unidentified phase transitions are found. These transitions are attributed to those in the Nd spin system but the interaction between Cu and Nd spins is not negligible to the transitions. The ESR measurement supports the present model.

Magnetic and Mössbauer study on Nd&amp;lt;inf&amp;gt;2&amp;lt;/inf&amp;gt;(Fe&amp;lt;inf&amp;gt;1-x&amp;lt;/inf&amp;gt;Co&amp;lt;inf&amp;gt;x&amp;lt;/inf&amp;gt;)&amp;lt;inf&amp;gt;14&amp;lt;/inf&amp;gt;B compound

The saturation magnetization of Nd 2 (Fe 1-x Co x ) 14 B M s (x) measured up to 32T by the pulse field method shows a maximum around x=0. 1. The behavior is explained by the rigid band model. The temperature dependence of Mossbauer spectrum for Nd 2 Fe 14 B is analyzed by taking line width and intensity ratio of six subspectra as constant values and hyperfine parameters for Nd 2 Fe 14 B are obtained. Utilizing M s (x) and hyperflne parameters for Nd 2 Fe 14 B at R.T., the Mossbauer spectra for x=0.3 and 0.4 are analyzed by the random substitution model of Co for Fe in Nd 2 (Fe 1-x Co x ) 14 B. The analysis suggests that each k 1 , k 2 , j 1 and j 2 site has a maximum in the dependence of H hf (n) on the number of nearest neighbor Fe atoms n, while each c and e site has monotonical decrease of H hf (n).