Magnetic Properties Of Nd Research Articles

Effect of Ce on phase formation and magnetic properties of (Nd–Pr)2.28Fe13.58B1.14 melt-spun ribbons

The phase formation of the (Nd0.70Pr0.30−xCex)2.28Fe13.58B1.14 (x = 0.10, 0.15, and 0.20; hereafter defined as Pr20Ce10, Pr15Ce15 and Pr10Ce20, respectively) and (Nd0.60Pr0.40−yCey)2.28Fe13.58B1.14 (y = 0.10, 0.20, and 0.30; hereafter defined as Pr30Ce10, Pr20Ce20 and Pr10Ce30, respectively) alloys that were prepared via the arc-melting method was investigated experimentally. The x-ray diffraction results revealed that all alloys annealed at 1173 K for 360 h consisted of a (NdPrCe)2Fe14B main phase with a tetragonal Nd2Fe14B-typed structure (space group P42/mnm) and an α-Fe minor phase, except for the Pr10Ce30 alloy, which contained an additional CeFe2 phase. The magnetic properties of the (Nd0.70Pr0.30−xCex)2.28Fe13.58B1.14 and (Nd0.60Pr0.40−yCey)2.28Fe13.58B1.14 ribbons that were prepared by melt spinning were examined. The remanence (Br) and maximum magnetic energy product ((BH)max) of the (Nd0.70Pr0.30−xCex)2.28Fe13.58B1.14 ribbons increased first and then decreased, whereas the coercivity (Hcj) of the ribbons increased with an increase in Ce content. The Br and (BH)max of the (Nd0.60Pr0.60−yCey)2.28Fe13.58B1.14 ribbons increased, whereas the Hcj of the ribbons decreased gradually with an increase in Ce content. This changed behavior of magnetic properties is attributed to the variation of volume fraction of the α-Fe phase and different phase formations in the melt-spun ribbons. The Curie temperatures (Tc) of all ribbons decreased slightly with Ce substitution, which results from the lower Curie temperatures of Pr2Fe14B and Ce2Fe14B. The Pr10Ce30 ribbon with a higher Ce content exhibited optimal magnetic properties (Br = 9.71 kGs, Hcj = 13.09 kOe, (BH)max = 18.78 MGOe), which indicates that suitable magnetic properties of the Nd–Pr–Ce–Fe–B melt-spun ribbons can be achieved by alloy-composition and phase-formation design.

Influence on the Magnetic Properties of Nd Doped in Fe3O4 Nanoparticles

Spherical magnetic Fe3O4 nanoparticles with different Nd doping amounts were successfully prepared using a simple hydrothermal method. The products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic laser scattering particle size (DLS), and vibrating sample magnetometer (VSM) analysis. Results showed that the spherical nanoparticles of pure Fe3O4, pure Nd2O3, and Nd-Fe3O4 were confirmed by XRD and TEM. The size of the prepared nanoparticles decreased first and then increased with increasing Nd doping amount by dynamic laser scattering. In addition, magnetic parameters, including saturation magnetization, remanent magnetization, and coercivity of Fe3O4 nanoparticles with different doping ratios of Nd, were analyzed by VSM.

Magnetic Properties of Nd–Fe–B Sintered Magnets Produced by Reduction-Grain Boundary Diffusion Process with Heavy Rare-Earths Compounds and Ca Metal Vapor

Magnetic Properties of Nd–Fe–B Sintered Magnets Produced by Reduction-Grain Boundary Diffusion Process with Heavy Rare-Earths Compounds and Ca Metal Vapor

Structural, electrical transport and magnetic properties of Nd3+ substituted Mn–Cu nanoferrites

Abstract In present study, a series of spinel ferrite nanoparticles (NPs) with general formula Mn1-xCuxNd0.15Fe1.85O4 (x = 0.0, 0.1, 0.3 and 0.5) have been prepared by sol-gel route. The powder X-ray diffraction (XRD) and Raman spectroscopy revealed the formation of single phase of cubic spinel structure in doped samples. However, a formation of NdFeO3 secondary ortho-ferrite phase has been observed for higher content of x = 0.5. The average crystallite size calculated from Scherrer’s formula has been found in the range 6.5–16.5 nm. The lattice constant (a) estimated using XRD data has been found to increase from 8.4265 A to 8.4501 A on incorporation of Cu2+ ions. FTIR spectra of prepared NPs exhibit two prominent absorption peaks near 600 cm−1 and 400 cm−1 associated to 596 cm−1 and 496 cm−1 band. The dc resistivity measurements with a rise in temperature divulge the typical semiconducting behavior of the as-synthesized samples. The activation energies of the samples have been calculated from Arrhenius plot and found to be in between 0.29 eV and 0.59 eV. Furthermore, the frequency dependent dielectric permittivity, loss tangent and ac conductivity revealed the usual dielectric dispersion. The behavior of dielectric properties highlighted the Debye relaxation peak which is interpreted in the view of Koop’s theory in the light of the Maxwell-Wagner model. Real ( Z ’ ) and imaginary ( Z ’ ’ ) part of impedance confirm the relaxation mechanism associated to the grains and grain boundaries effect. Electron paramagnetic resonance (EPR) pattern shows a broad sharp resonance signal with Lange g-factor varies from 2.04 to 2.18, which is due to dominant spin-exchange interaction between Fe3+, Mn2+, and Cu2+ ions. P-E hysteresis loops found the ferroelectric nature of the ferrite samples. Typical soft ferrimagnetic behavior of Nd3+ substituted Mn–Cu ferrites have been observed at room temperature. The low losses, giant dielectric constant and high resistivity of prepared ferrite NPs can offer several applications like power transformers and microwave devices.

From a conventional ferromagnetism to a frustrated magnetism: An unexpected role of Fe in Nd(Al1-xFex)2 (x ≤ 0.2)

The structure and magnetic properties of Nd(Al1-xFex)2 alloys with x = 0, 0.05, 0.1 and 0.2, which adopt cubic MgCu2-type structure with space group Fd3¯m, are studied using x-ray powder diffraction, static and dynamic magnetization, and calorimetric measurements. The lattice constant decreases linearly with increasing Fe content from 8.0106(4) Å to 7.9044(4) Å. Large thermal irreversibilities between zero-field-cooled and field-cooled conditions are observed for all substituted samples. The magnetic transition temperatures exhibit a minimum for x = 0.1, and coercive fields at 2 K increase from 70 Oe for x = 0 to 6.3 kOe for x = 0.2. The absence of λ-type peak in the heat capacity data, frequency dependence of ac magnetic susceptibility, and memory effects indicate formation of a cluster-glass magnetic state when x ≥ 0.1.

Nature of correlated polaron hopping mechanism in A-site cation disorder Nd0.7−xLaxSr0.3MnO3 (x = 0.0, 0.1, 0.2 and 0.3) manganites

The structural, transport and magnetic properties of Nd0.7−xLaxSr0.3MnO3 (for x = 0.0, 0.1, 0.2, 0.3) manganite prepared by solid-state route were investigated. All the samples are exhibiting distorted orthorhombic perovskite structure. Lattice parameters and bond angles are increasing with an increase in La concentration. The electrical resistivity ρ(T → 0) and ρ(Tc), both are decreasing with substitution of La (x = 0.0, 0.1, 0.2, 0.3) and the presence of an external magnetic field giving rise to the colossal magnetoresistance (CMR) effect. The temperature-dependent transport nature has been explored with a correlated polaron hopping mechanism based on the Holstein Hamiltonian model. This model is very well concurring with our experimental results and it is further addressing the widely known transition from the low-temperature metallic to the localized polaron hopping conductivity at high temperature. Furthermore, the spin-order temperature (Tc) and the atomic-order temperature (Tca) both are increasing with La substitution. The present analysis shows that the correlated polaron hopping model describes the transport properties of La-substituted Nd0.7−xLaxSr0.3MnO3 samples.

Study of the effect of photoluminescence, structural and magnetic properties of Nd doped NdxNi1−xO (x = 0.01, 0.02 and 0.03) hexagonal particles

At ambient temperature, nickel oxide (undoped), as well as a variety of Nd-doped NiO, NdxNi1−xO (x = 0.01, 0.02 and 0.03) hexagonal-like particles, have been synthesized by employing a microwave synthesis approach. The synthesized samples properties were known by various instrumental techniques, for instance, XRD (X-ray diffraction), TEM and SEM (transmission and scanning electron microscopy), optical absorption, and photoluminescence (PL) methods. Nd doping increases the crystallite size. X-ray diffraction information of NiO indicates that substitution of Nd increases the lattice parameter and crystallite size. The surface morphology results showed that the distribution of homogeneous particles alongside aggregation that is caused by interactions of dipole-dipole. The as-synthesized samples' soft magnetic characters were examined.

Effects of Dy diffusion time on magnetic properties of Nd–Fe–B sintered magnets

In recent years, significant research efforts were undertaken to enhance coercivity (Hcj) of Nd-Fe-B sintered magnets. One of the methods is Dy diffusion, which is very effective in improving Hcj while maintaining the same level of remanence (Br). Experiments reported in this work revealed that Dy diffusion differently affected Hcj of Nd-Fe-B sintered magnets at three diffusion stages: (1) from 0 to 4 h of Dy diffusion, Hcj increased rapidly from 32.3 to 36.5 kOe as Dy content increased rapidly from 0 to 0.27 wt%; (2) from 4 to 24 h, when Dy content changed from 0.27 to 0.56wt%, Hcj increased from 36.5 to 38.7 kOe; (3) from 24 to 30 h, Hcj and Dy content barely changed. Thus, extending Dy diffusion time beyond 24 h period would not yield any improvements. From 0 to 30 h, Br slightly decreased from 12.40 to 12.22 kGs. During Dy diffusion, intergranular grain boundaries became continuous and homogeneous, and some micro-defects were repaired. As a result, from 0 to 24 h, Hcj enhanced significantly while Br barely changed. Thus, the Nd-Fe-B sintered magnets with high properties (Br = 12.22 kGs, Hcj = 38.9 kOe and (BH)max = 36.87 MGOe) were obtained.

Effect of W/Co co-substitution on structural, microstructural, magnetic and electrical properties of Bi4NdFeTi3O15 aurivillius compound

Here, in this paper, we have reported the structural, microstructural, optical, ferroelectric and magnetic properties of Nd and W/Co co-substituted Bi4NdTi3−2x(W/Co2)xFeO15 (0.00 ≤ x ≤ 0.15) 4-layered Aurivillius multiferroic ceramics. These ceramics were prepared by conventional high-temperature solid-state reaction method. The room temperature (RT) X-ray diffraction (XRD) and Raman studies revealed that, these ceramics exhibits a pure orthorhombic structure with A21am space group. The surface morphology of these ceramic studies confirmed the formation of randomly oriented grains as non-uniform in size. Further, W/Co2 substitution in BNFT revealed the presence of asymmetrical shaped internal nano-size domains. The band gap of the ceramics was calculated and found to be decreased upon with increasing the concentration of W/Co2. All compounds exhibited improved P–E loops with unsaturated polarization upon substitution with enhance polarization and reduced coercive field. It was found that with higher substitution levels x ≥ 0.10 adversely affected the ferroelectric characteristics. The magnetic measurement revealed that Nd and W/Co co-substitution induced a strong ferromagnetic interaction via Fe3+–O–Co2+/3+ coupling. The high-temperature magnetization studies revealed the Curie temperature (TC) enhances as the W/Co2 concentration increase. Henceforth, the observed outcomes are emphasized for designing new single-phase room temperature multiferroics in future magnetoelectric applications.

Effect of Diamagnetic Ion Substitution on Structural and Magnetic Properties of Nd3+ Modified Solid Solutions

Solid solutions of Bi0.9Nd0.1Fe1−xTixO3 have been prepared using conventional solid state reaction route. The Rietveld refinements of XRD patterns of all samples confirm the rhombohedral structure at room temperature. With increase in Ti substitution, there is reduction in leakage current and improvement in ferroelectric properties in the studied Bi0.9Nd0.1Fe1−xTixO3 solid solutions. The ac conductivity follows the universal Jonscher’s power law for all the samples. Antiferromagnetic orders are observed to be suppressed on Ti substitution, in the studied BNFO solid solutions, thereby, giving rise to non-zero magnetic moment. The remnant magnetization has been observed to increase with increase in Ti content.

Permanent magnetic properties of Nd–Fe–B melt-spun ribbons with Y substitution

Phase constituents, microstructures and magnetic properties of melt-spun Nd12−xYxFe81B6Nb ribbons were investigated systematically. The influence of Y substitution for Nd on the phase stability, grain size and magnetic exchange coupling was analyzed. It is found that all the ribbons crystallize in the tetragonal 2:14:1 structure, i.e., with single hard magnetic phase at the roll speed of 25 m·s−1. With the increase in Y doping, Curie temperature (TC) increases, while the coercivity decreases monoclinically. However, remanence magnetization (Br) and maximum energy product ((BH)max) fluctuate and the maximum value is obtained at certain amount of Y. The optimum magnetic properties of intrinsic coercivity of intrinsic coercivity (Hcj) = 908.2 kA·m−1 and (BH)max = 118.52 kJ·m−3 are achieved when x = 1.0. It can be attributed to the strengthened exchange coupling between the neighboring nanograins in Nd–Y–Fe–B melt-spun powder based on the Henkel curves. Furthermore, Y substitution also significantly improves the temperature stability of magnetic performance. The coercivity temperature coefficient of β = − 0.157%·°C−1 and remanence temperature coefficient of α = − 0.32%·°C−1 are gained, which are greatly reduced compared with those of the undoped Nd–Fe–B compounds.

Calculating temperature-dependent properties of Nd2Fe14B permanent magnets by atomistic spin model simulations

Temperature-dependent magnetic properties of Nd$_2$Fe$_{14}$B permanent magnets, i.e., saturation magnetization $M_\text{s}(T)$, effective magnetic anisotropy constants $K_i^\text{eff}(T)$ ($i=1,2,3$), domain wall width $\delta_w(T)$, and exchange stiffness constant $A_\text{e}(T)$, are calculated by using \textit{ab-initio} informed atomistic spin model simulations. We construct the atomistic spin model Hamiltonian for Nd$_2$Fe$_{14}$B by using the Heisenberg exchange of Fe$-$Fe and Fe$-$Nd atomic pairs, the uniaxial single-ion anisotropy of Fe atoms, and the crystal-field energy of Nd ions which is approximately expanded into an energy formula featured by second, fourth, and sixth-order phenomenological anisotropy constants. After applying a temperature rescaling strategy, we show that the calculated Curie temperature, spin-reorientation phenomenon, $M_\text{s}(T)$, $\delta_w(T)$, and $K_i^\text{eff}(T)$ agree well with the experimental results. $A_\text{e}(T)$ is estimated through a general continuum description of the domain wall profile by mapping atomistic magnetic moments to the macroscopic magnetization. $A_\text{e}$ is found to decrease more slowly than $K_1^\text{eff}$ with increasing temperature, and approximately scale with normalized magnetization as $A_\text{e}(T) \sim m^{1.2}$. This work provokes a scale bridge between \textit{ab-initio} calculations and temperature-dependent micromagnetic simulations of Nd-Fe-B permanent magnets.

Effect of cobalt substitution on structure and magnetic properties of Nd0.4Zr0.6Fe10–xCoxSi2 (x = 0–3) alloys and their ribbons

This study reports the stabilization of the RFe12-type based compounds where part of R and Fe are substituted with Zr and Co and Si, respectively, in order to examine whether these rare-earth-lean materials are suitable for applications as permanent magnets. Structural and magnetic characterization of the family of alloys with the general formula Nd0.4Zr0.6Fe10–xCoxSi2 (x = 0–3) and their melt-spun ribbons were carried out using X-ray diffraction and Mössbauer spectroscopy. The ThMn12-type structure is obtained for all samples as the majority phase with a minority α-Fe(CoSi) phase (less than 5 wt%) as it was estimated by XRD for x = 1 and 2. The Curie temperature increases linearly with Co substitution from 561 K for x = 0 to 712 K for x = 3. The saturation magnetization decreases slightly from 130.5 (x = 1) to 129.1 A·m2/kg (x = 3), while the anisotropy field is following the same trend.

Preparation and magnetic properties of Nd(FeMo) and its nitrides

Abstract In this study, a Nd(FeMo)12 alloy was prepared using a magnetic levitation melting furnace and subsequent heat treatment. The nitrides of this alloy, which exhibit uniaxial anisotropy, were then synthesized by gas-solid reaction. The melting process of the Nd(FeMo)12 alloy, as well as the microstructure and magnetic properties of the nitrides, was investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and magnetometer measurements. A homogeneous Nd(FeMo)12 phase was obtained by magnetic levitation melting using a MoFe alloy as a raw material, followed by heat treatment for 72 h. The nitrogenation of the Nd(FeMo)12 alloy was investigated. The magnetic properties of Nd(FeMo)12N1.52 powders obtained at a nitriding temperature of 550 °C were enhanced after grinding. No phase decomposition occurred during grinding. The nitriding powders exhibited a fine polycrystalline structure after grinding, as determined by transmission electron microscopy. The coercivity of the powders increased with a decrease in particle size, and Nd(FeMo)12N1.52 nano-powders with a coercivity of 3800 Oe was prepared by 70 h of surfactant-assisted high energy ball milling. Nd(FeMo)12N1.52 powders obtained exhibit an HA of 11 T and TC of 598 K.

Microstructure and magnetic properties of Nd–Fe–B sintered magnets with P addition

In this paper, the effects of P doping on magnetic properties and microstructure were studied in Nd–Fe–B sintered magnets. With P doping, the grain size gets refined and the distribution of the main phase is optimized due to the reduction of the liquidus temperature. The liquidus temperature for the 0.05 wt% P-doped magnets is 1022 K, while that for the P-free magnets is 1038 K. As P content increases, the liquidus temperature significantly decreases. Clear and continuous grain boundary phases are formed in the P-containing magnets with smaller grain size. The optimized microstructure with average grain size of 8.43 μm is obtained in the 0.05 wt% P-doped magnets, which is approximately 0.69 μm smaller than that of P-free sintered magnets (9.12 μm). Though P is usually thought to be an impurity element, it might be beneficial in Nd–Fe–B sintered magnets with proper addition. The coercivity of the 0.05 wt% P-doped magnets could be increased to 1283 kA·m−1, with slight changes of the remanence and the maximum magnetic energy product. NdPO4 phases in the grain boundary are of hexagonal structure, while those at the triple junctions have monoclinic structure. Activated sintering is achieved by doping proper P element in the Nd–Fe–B sintered magnets.

Increase in Nucleation Field of Nanocrystalline Nd(Fe,Co)B Magnets Due to Strengthening of Exchange Interaction—Computer Simulation

The effect of the strength of exchange interaction on the nucleation field $H_{N}$ was studied by computer simulation with varying temperature as well as the size of the non-magnetic phase for Nd(Fe,Co)B magnets composed of fine grains. It was clarified that the spatial distribution of demagnetizing field $H_{d}$ is widened by an increase in the size of the non-magnetic phase and that the ratio of the spatial size of $H_{d}$ to the exchange length $L_{\mathrm {ex}}$ is an important factor of determining $H_{N}$ . Resultantly, the increase in the exchange strength increased $H_{N}$ . Based on this calculation result, magnetic properties of Nd(Fe,Co)B magnets were simulated and it was found that a small amount of substitution of Co for Fe increases $L_{\mathrm {ex}}$ and resultantly improves $H_{N}$ at high temperatures.

Structural, electrical and magnetic properties of Nd \u2013 A \u2013 CoO3 (A\u2009=\u2009Sr, Ca) Perovskite Powders by Mechanical Alloying

In this work, NdCoO3 (NCO), Nd0.8Sr0.2CoO3 (NSCO) and Nd0.9Ca0.1CoO3 (NCCO) perovskite cobaltites were synthesised by mechanical alloying method. Structural evolutions, magnetic and electrical properties of these perovskite were systematically examined through X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray detection (SEM-EDX), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), vibration sample magnetometer (VSM) and impedance analyser (IA). The XRD and SEM results revealed that the microstructure of the perovskite materials changed during mechanical alloying. The average crystallite size of the perovskite materials was calculated by Debye Scherrer equation and was confirmed by TEM, and it was determined ~19 nm. From the VSM results, the all perovskites had soft ferromagnetic properties. IA measurements showed that relatively dielectric constants of the perovskites decreased with increasing frequency. Therefore, for the first time, nanostructured NCO, NSCO and NCCO perovskites exhibiting good properties were produced in only two steps which are milling and heating.

Magnetic properties of bismuth-substituted neodymium iron garnet films on Gd3Ga5O12(100) substrates determined by ferromagnetic resonance measurements

Magnetic properties of Nd3−xBixFe5O12 (0 ≤ x ≤ 3) films prepared by metal organic decomposition on Gd3Ga5O12(100) substrates have been investigated. The Faraday rotation angle θF increased with bismuth concentration. The uniaxial anisotropy constant Ku, cubic magnetocrystalline anisotropy constant K1, gyromagnetic ratio γ, g-factor, and FMR line width ΔH were determined by ferromagnetic resonance measurements. Ku was positive and K1 was negative for all samples. Ku decreased from 9.83 × 104 to 2.05 × 104 erg/cm3 as x increased from 0 to 3. K1 was almost constant irrespective of x, and it took a value between −3.28 × 104 and −2.08 × 104 erg/cm3. γ, g-factor, and ΔH also decreased with increasing bismuth concentration. From the results of the investigation of the in-plane tensile strain applied to the films, the effect of strain on Ku is considered to be small.

Role of typical elements in Nd2Fe14X ( X=B , C, N, O, F)

The magnetic properties and structural stability of Nd$_{2}$Fe$_{14}X$ ($X$ = B, C, N, O, F) are theoretically studied by first-principles calculations focusing on the role of $X$. We find that B reduces the magnetic moment (per formula unit) and magnetization (per volume) in Nd$_{2}$Fe$_{14}$B. The crystal-field parameter $A_2^0 \langle r^2 \rangle$ of Nd is not enhanced either, suggesting that B has minor roles in the uniaxial magnetocrystalline anisotropy of Nd. These findings are in contrast to the long-held belief that B works positively for the magnetic properties of Nd$_{2}$Fe$_{14}$B. As $X$ changes from B to C, N, O and F, both the magnetic properties and stability vary significantly. The formation energies of Nd$_{2}$Fe$_{14}X$ and $\alpha$-Fe relative to that of Nd$_{2}$Fe$_{17}X$ are negative for $X$ = B and C, whereas they are positive when $X$ = N, O and F. This indicates that B plays an important role in stabilizing the Nd$_{2}$Fe$_{14}$B phase.

Influence of Cooling Condition of Casted Strips on Magnetic Properties of Nd–Fe–B Sintered Magnets

We investigated the additional (secondary) cooling effect of casted strips on the magnetic properties of Nd–Fe–B sintered magnets. The Nd–Fe–B sintered magnets were fabricated with the casted strips prepared without and with additional cooling. Additional cooling was achieved by blowing Ar gas at various pressures (0.1, 0.3, and 0.6 MPa) on the free-side surface of the strips during the strip-casting process. The higher magnetic properties of Hc, Br, and (BH)max of the final Nd–Fe–B sintered magnets were obtained for 0.1 MPa rather than for 0.0 MPa. The best microstructure of the columnar grains in the casted strips was produced with the aid of a lower pressure of gas on the free-side surface. It was found that the microstructure of the strips affects the distribution of grains grown in the sintered magnets. This report demonstrates that the improved magnetic performance of Nd–Fe–B sintered magnets was achieved via additional gas cooling.