PERMANENT MAGNETS FROM ELONGATED SINGLE-DOMAIN PARTICLES

This paper reports the microalloying effect of Cu and Nb on the microstructure and magnetic properties of a Fe/sub 3/B/Nd/sub 2/Fe/sub 14/B nanocomposite permanent magnet. Optimum magnetic properties with B/sub r/=1.25 T, H/sub cJ/=273 kA/m and (BH)/sub max/=125 kJ/m/sup 3/ were obtained by annealing a melt-spun Nd/sub 4.5/Fe/sub 75.8/B/sub 18.5/Cu/sub 0.2/Nb/sub 1/ amorphous ribbon at 660/spl deg/C for 6 min. Compared with a ternary Nd/sub 4.5/Fe/sub 77/B/sub 18.5/ alloy, the grain size is much finer in the optimum microstructure of the Cu and Nb containing alloys, and the temperature range of the heat-treatment for obtaining optimum hard magnetic properties was significantly extended. The soft magnetic Fe/sub 23/B/sub 6/ phase coexists with Fe/sub 3/B and Nd/sub 2/Fe/sub 14/B phases in the optimum microstructure. Three-dimensional atom probe (3DAP) analysis results have revealed that the finer microstructure is due to the formation of a high number density of Cu clusters, which promote the nucleation of the Fe/sub 3/B phase. The Nb atoms appear to induce the formation of the Fe/sub 23/B/sub 6/ phase and stabilize it by partitioning into this phase.

Study on magnetic properties of (Nd0.8Ce0.2)2−xFe12Co2B (x = 0–0.6) alloys

This experiment was carried out to investigate the effect of ZnO substitution on the magnetic and physical properties of Co-Ni ferrite fine particle prepared by the chemical coprecipitation method without post-annealing process. The chemical coprecipitation compositions were chosen according to the formula (CoO)0.5(NiO)0.5-x(ZnO)x⋅n/2(Fe2O3), where x was varied between 0 and 0.5, and n between 2.0 and 3.0. The saturation magnetization σs, has a tendency to increase up to x=0.3, however decrease when x is above 0.3. On the other hand, the coercivity HcJ decreases as x increases. Optimum magnetic properties were achieved with materials of composition (CoO)0.05(NiO)0.45(ZnO)0.05⋅1.25(Fe2O3). The typical magnetic and physical properties are saturation magnetization σs=61.9×10-6 Wb⋅m/kg (49.3 emu/g), coercivity HcJ=372.5kA/m (4.68 kOe), the lattice constant a= 0.8379 run, and the average particle size = 38 nm. The rotational hysteresis integral Rh, which is related to the magnetization mechanism of these fine particles, is 1.80, and it is found that the magnetization mechanism is an incoherent rotation mode. Crystalline magnetic anisotropy constants are K11=+6.7×104 J/m3 (+6.7×105 erg /cm3) and K2=-16.8×104J/m3 (-16.8×105 erg/cm3).

Evolution of phase, texture, microstructure and magnetic properties of Fe–Cr–Co–Mo–Ti permanent magnets

Influence of Ba content on magnetic properties of the Sr0.4-xBaxLa0.4Ca0.2Fe10.8Co0.2O19 hexaferrite from recycled rare-earth tailings

Single phase Sr-La M-type ferrite fine particles were prepared by the chemical coprecipitation and subsequent heat treatment methods. Optimum magnetic properties were achieved with materials of composition Sr/sub 0.794//sup 2+/La/sub 0.172//sup 3+/Fe/sub 0.335//sup 2+/Fe/sub 11 /./sub 74//sup 3+/O/sub 19/, and heat treatment of 950/spl deg/C/spl times/2 h in air, The magnetic and physical properties are /spl sigma//sub s/=90.5/spl times/10/sup -6/ Wb/spl middot/m/kg (72,0 emu/g), H/sub cJ/=505.3 kA/m (6.35 kOe), T/sub c/=454.4/spl deg/C, the lattice constants a=0.5882 nm, c=2.303 nm, the activation energy=230.9 kJ/mol (55.2 kcal/mol), and the average particle size=0.3 /spl mu/m.

Nanostructured cobalt ferrite powders were prepared using the sol–gel process to obtain the optimal crystallite size and magnetic properties. The effect of sol–gel parameters, including the pH value, the mole ratio of ethylenediaminetetraacetic acid (EDTA) to metal ions, the mole ratio of ethylene glycol (EG) to metal ions and the heat-treatment temperature on the crystallite size and the magnetic properties of the samples, was investigated by Taguchi statistical experiments. By using three different levels for each process parameter, nine unique experiments were defined based on an L9 orthogonal array. From the analysis of the powder X-ray diffraction patterns, the crystallite size was calculated by the most intense peak (311) using the Scherrer formula. The results showed that the crystallite size is in the range of 16–39 nm, depending on the different levels of each parameter. The magnetic properties of the samples were carried out using the vibrating sample magnetometer (VSM) and magnetic parameters, such as the saturation magnetization (MS) and coercivity (HC) obtained from the VSM data. The analysis of variance showed that the optimum values of the parameters to obtain the optimal crystallite size and magnetic properties have occurred at the heat-treatment temperature of 1023 K, EDTA-to-metal ions molar ratio equal to 1.67, EG-to-metal ions molar ratio of 3.33 and pH = 6.

Effect of Gallium Addition on Magnetic Properties of Nd 2Fe 14B-Based/α-Fe Nanocomposite Magnets

Effect of Cu doping and annealing treatment on the microstructure and magnetic properties of nanocrystalline single-phase Nd-Fe-B alloys

ABSTRACTThis study investigates the influence of rolling passes and annealing methods on the microstructure and texture of ultrathin grain‐oriented silicon steel, aiming to improve its magnetic properties by optimising processing parameters. The results show that under identical total rolling reductions and annealing conditions, more rolling passes weaken η‐fibre recrystallisation texture, thus reducing magnetic induction (B8). Meanwhile, more rolling passes lead to coarser microstructure after short annealing, whereas non‐η‐fibre oriented grains exhibit more pronounced growth advantage with prolonged annealing. Consequently, the sheets rolled by 4–5 passes show an initially decreasing and then increasing trend in iron loss. When the rolling method is same, higher annealing temperatures accelerate non‐η‐fibre oriented grain growth. This not only drives grain sizes into a critical range that raises iron loss but also exacerbates the weakening of η‐fibre texture, collectively deteriorating magnetic properties. To sum up, the magnetic properties of ultrathin grain‐oriented silicon steel are predominantly determined by the extent to which η‐fibre oriented grains are consumed by other growing grains during annealing. In this study, optimal magnetic properties, specifically B8 > 1.8 T and P1.5/400 < 12 W/kg, can be achieved through four‐pass rolling combined with annealing at 820°C or 850°C by adjusting the annealing time.

Nickel substituted CoxZn0.8-x Fe2O4 (x=0.2,0.5 and 0.6) ferrite were synthesized by Sol-gel auto combustion method. The powders were sintering at 400 o c and 700 o c for 2hrs to densify properly. The samples were characterized by XRD, SEM and FTIR and Magnetic properties. The XRD used to analyze phase structure and lattice parameters. The FTIR spectra confirmed that synthesis material is ferrite. Morphology of ferrite powders were investigated by using SEM. Porosity of synthesis ferrite is measured. The saturation magnetization increases with increasing Co-Zn concentration. Resistivity of ferrite material is may be decreases due to vary concentration of Co and Zn. this paper we present a study of the magnetic and structural properties of Ni0.2CO0.2Zn0.6Fe2O4, Ni0.2CO0.5Zn0.3Fe2O4 and Ni0.2CO0.6Zn0.2Fe2O4 nanocomposites of different composition. The composition, crystal structure, morphology, and size distribution of Ni-Co-Zn ferrite nanocrystals can be controlled by adjusting the synthesis route and molar ratio of materials in the initial mixtures. The synthesized nano crystals have been characterized by XRD, SEM, FTIR, and Magnetic Properties presented below are the details of investigation. II. Experimental: The Ni0.2CO0.2Zn0.6Fe2O4, Ni0.2CO0.5Zn0.3Fe2O4 and Ni0.2CO0.6Zn0.2Fe2O4 ferrite powders were prepared by co-precipitation and hydro thermal technique using iron nitrate, zinc nitrate, cobalt nitrate, and nickel nitrate as reaction agent. To obtain Ni0.2CO0.2Zn0.6Fe2O4, Ni0.2CO0.5Zn0.3Fe2O4 and Ni0.2CO0.6Zn0.2Fe2O4 ferrite powders we have mixed AR grade iron nitrate, zinc nitrate, cobalt nitrate, and nickel nitrate with double distilled water. Citric acid was used as a chelating agent because it plays an important role in homogeneous mixture formation of metal cations. Reaction procedure was carried out in air atmosphere at room temperature. The composition was well shake and pH of solution is maintained as 7 by adding ammonia. The prepared solution was stirred on magnetic stirrer at low temperature 80 0 C to form a gel. The prepared ferrite samples were annealed for 400 0 C and 700 0

<title>Abstract</title> Yttrium iron garnet (Y ₃ Fe ₅ O ₁₂ , YIG) ferrite is a key microwave electronic material, renowned for its excellent dielectric and magnetic properties, which make it widely applicable in communication devices and systems. In this study, a series of YIG ferrite with the composition Y _2.0−2x BiCa _2x Fe _5−2x (SnZr) _x O ₁₂ (x = 0.00-0.50 in steps of 0.10) were synthesized via the solid-state reaction method. The effects of co-substitution with Ca ²⁺ , Sn ⁴⁺ and Zr ⁴⁺ ions on the phase formation, microstructure, magnetic properties and dielectric performance were systematically investigated. The results indicate that this multi-ion substitution significantly alters the grain size and morphology. Optimum magnetic properties were achieved with a maximum specific saturation magnetization (σ _s ) of 28.12 emu/g and low coercivity ( <italic>H</italic> _c ) of 54.46 Oe. Electromagnetic characterization at 10 MHz revealed maximum values of magnetic permeability (µ') and dielectric permittivity (ε') of approximately 22 (at x = 0.5) and 18.6 (at x = 0.3), respectively. Notably, the sample with x = 0.2 exhibited a minimum ferromagnetic resonance (FMR) linewidth (Δ <italic>H</italic> ) of 409.30 Oe alongside a high saturation magnetization (4πMs) of 1847.9 Gs. These findings suggest that the developed materials are promising candidates for use as substrates, potentially enabling the miniaturization and performance enhancement of high frequency microwave devices.

Comprehensively improved magnetic performance of Nd-Fe-B magnets with high-efficiency grain boundary diffusion of heavy rare earth

Magnetic properties and Tb diffusion of sintered Nd–Fe–B magnets by suspension plasma spraying

&lt;p&gt;Permanent magnet Barium M-Hexaferrite, BaFe&lt;sub&gt;12-x &lt;/sub&gt;Cu&lt;sub&gt;x&lt;/sub&gt; O&lt;sub&gt;19 &lt;/sub&gt; was synthesized with a wide range of x (x = 0.1, 0.2, …, 3 and 4mole% respectively). The precursor was made by mixing BaCO&lt;sub&gt;3&lt;/sub&gt; powder and Fe&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; powder, whereas CuO powder was used as additive. The powders were mixed together by wet milling in distilled water medium for 20 hours. The powders had been dried at a temperature of 100&lt;sup&gt;0&lt;/sup&gt;C for 24 h before calcined at a temperature of 1100&lt;sup&gt;0&lt;/sup&gt;C for 2 hours. The powders were then grained to prepare 400 mesh (38 µm) in diameter. The samples density was determined by using Archimedes method, magnetic properties by using permagraph, crystal structure by XRD-pattern and microwave absorbing properties using VNA. The hysteresis curve showed that the value of magnetic field ranging from 43.36 G to 100.42 G , remanence magnetic induction (Br) 20G-320G, coercivity (HcJ) 1.07 kOe to 9.22 kOe and energy production (BH) max from 0.05kGOe to 0.92 kGOe with a density from 3.82 g/cm&lt;sup&gt;3&lt;/sup&gt; to 5.2 g/cm&lt;sup&gt;3&lt;/sup&gt;. The effect of Cu doping tent to increase the value of density with an optimum magnetic properties at x=0.3%mole.&lt;/p&gt;