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This study investigates the effects of multi-transition metals on the soft magnetic properties of Fe73.5−xB9Si14Cu1Nb2.5Mx (M = Nb, Mo, and W) nanocrystalline soft magnetic alloys. Nanocrystalline soft magnetic materials are utilized in electronic components on the basis of their permeability and low core loss. In conventional alloys such as FINEMET, Nb inhibits nanocrystal growth and promotes amorphous formation. In this research, Mo and W were used as additional transition metals to control the size of nanocrystals and explore the potential for enhancing soft magnetic properties. We confirmed that the addition of Mo and W reduced the nanocrystal size, and the activation energy for nanocrystal formation and growth showed significant benefits for nanocrystalline alloys. Consequently, the soft magnetic properties of the alloys containing Mo and W exhibited higher permeability and lower coercivity. These results suggest that multi-transition metals are effective in improving soft magnetic properties by inhibiting nanocrystal formation and growth. [ABSTRACT FROM AUTHOR]

Soft magnetic films play a crucial role in numerous technological applications, such as magnetoelectronics, telecommunications, and magnetic recording, and the tuning of properties to obtain high-efficiency demands searching new materials and controlling thickness and compositions. In this regard, we report a systematic investigation of structural, morphological, electrical resistivity, and temperature-dependent magnetic properties of single-layer amorphous Fe70Co15Zr7B5Cu3 HITPERM (t = 5–100 nm) films deposited on a low-cost thermally oxidized Si substrate. Structural studies (XRD and TEM) reveal an amorphous nature in all as-deposited films. Surface morphology shows that the average roughness increases with increasing t up to 50 nm and then decreases at higher thicknesses. The electrical resistivity decreases rapidly as t increases from 5 to 10 nm and then is invariant for films with t ≥ 30 nm. Interestingly, the variation of resistivity follows the Boltzmann fitting. These films exhibit tunable magnetic properties between soft (t < 20 nm) and semi-hard (20 nm < t < 70 nm) properties with rectangular-type magnetic hysteresis loops having ~ 100% remanence ratios (Mr/Ms), low coercivity (Hc < 2.5 kA/m), and low saturation magnetic field (Hs < 3 kA/m) for t ≤ 70 nm. Transcritical hysteresis loop with a large Hc > 6.7 kA/m, high Hs > 26.5 kA/m, and reduced Mr/Ms ~ 55% is observed for t = 100 nm film. High-temperature thermomagnetization curves display two magnetic phase transitions (TC) corresponding ferromagnetic state to a paramagnetic state of the amorphous phase (at 820 K during warming) and nanocrystalline phase (at 1003 K during cooling). The observed results of HITPERM films with large TC naturally make it a potential choice for applications not only in magnetoelectronics at room temperature but also for aircraft power devices at higher temperatures. [ABSTRACT FROM AUTHOR]

Excellent soft magnetic properties of the amorphous and nanocrystalline alloys are attributed to their unique microstructure. In this work, Fe73.5Si13.5-xNb3Cu1B9Px (x = 0, 3.5, 7, 10 at. %) amorphous ribbons have been fabricated using the melt spinning technique. The effect of annealing temperature (475 ~ 600 ℃) on the microstructure and soft magnetic properties have been studied. According to the results, the thermal stability of FeSiNbCuBP amorphous alloys was improved by the partial substitution of Si by P. Moreover, it was found that the grain growth of α-Fe (Si) phase can be restrained by the appropriate amount of P addition and result to a grain refinement of the alloys during annealing. Base on refinement grain size (9 nm) and optimal crystallization volume fraction (47%), Fe73.5Si10Nb3Cu1B9P3.5 nanocrystalline alloy with low coercivity of 0.02 A/m and high effective permeability of 3.22 × 104 was developed after annealed at 525 ℃. Besides, we propose that the migration of free electrons from P to Fe could diminish the saturation magnetization of these alloys. [ABSTRACT FROM AUTHOR]

This study investigates the effects of multi-transition metals on the soft magnetic properties of Fe73.5−xB9Si14Cu1Nb2.5Mx (M = Nb, Mo, and W) nanocrystalline soft magnetic alloys. Nanocrystalline soft magnetic materials are utilized in electronic components on the basis of their permeability and low core loss. In conventional alloys such as FINEMET, Nb inhibits nanocrystal growth and promotes amorphous formation. In this research, Mo and W were used as additional transition metals to control the size of nanocrystals and explore the potential for enhancing soft magnetic properties. We confirmed that the addition of Mo and W reduced the nanocrystal size, and the activation energy for nanocrystal formation and growth showed significant benefits for nanocrystalline alloys. Consequently, the soft magnetic properties of the alloys containing Mo and W exhibited higher permeability and lower coercivity. These results suggest that multi-transition metals are effective in improving soft magnetic properties by inhibiting nanocrystal formation and growth.

This study demonstrates the possibility of bringing novel Full Heusler high-entropy intermetallic compounds (FH-HEICs) to nanoscale regime. To this end, Co2(FeNiMnMgZn)Al, Co2(TiZrTaNbCr)Al and Cr2(TiZrTaNbV)(AlSi) FH-HEICs are prepared by mechanical alloying for 20 h. All FH-HEICs crystallize in a mixture of partially ordered B2-type and disordered A2-type crystal structures, which exhibit higher degree of disordering compared to the ideal L21 structure. Scanning electron microscope micrographs and Energy dispersive spectroscopy mapping confirm the homogenous distribution of elements within the nanocrystalline particles. Co2(FeNiMnMgZn)Al and Co2(TiZrTaNbCr)Al exhibited semi hard magnetic behavior with magnetic saturation of 50.93 emu/g and 18.73 emu/g at 300 K, respectively. Cr2(TiZrTaNbV)(AlSi) exhibited hard magnetic behavior with giant coercivity of 3.5 kOe and low magnetic saturation of about 0.2 emu/g. Finally, we introduce FH-HEICs as a novel group of functional materials with potentially intricate magnetic and catalytic properties, in which the order-disorder transition and wide chemical composition range provide unprecedented opportunity to tune their structural and functional properties. [ABSTRACT FROM AUTHOR]

An effort is made to find the solution to the new challenges of modification advancements in ferrite technologies. The hypothetical variation in the structural, magnetic, and electrical properties of cubic spinel magnesium aluminum ferrites introduced by the substitution of doping elements has been rationalized and proven. The outcome of aluminum substitution on the magnesium ferrites has been examined and investigated. Spinel ferrites having compositions of MgAlxFe2-xO4 (x = 0.1, 0.2, 0.3, 0.4) were prepared by the sol-gel auto-combustion method. The prepared sample’s characterization, such as scanning electron microscopy (SEM), DC electrical resistivity, AC electrical resistivity, and dielectric properties measurements, were tested using the respective instruments. The grain size and crystal size of all samples were measured from the micrographs of SEM and XRD Data. It is found that the average grain size is within the range of 300 nm - 550 nm for all different series that are formed, keeping the samples at 1100 °C sintering temperatures. A two-probe method experiment with a temperature range of 30 °C to 500 °C gives data on DC electrical resistivity. The Curie temperature depends on the sintering temperature, and it increases with increasing doping concentration. Also, doping influences grain size, which decreases with increasing concentration. Analyzing the SEM micrographs, it is found that the average grain size must decrease in tendency with increasing Al content. DC electrical resistivity exhibits excellent semiconducting behavior. Frequency dependence, dielectric constant, and dielectric loss factors were measured, keeping the frequency range of 75 Hz to 130 MHz at room temperature. The result shows that the dielectric constant (e) and dielectric loss tangent (tan™) decrease with the increase in frequency, while the AC resistivity and Q-factor increase. Comparing the electrical properties of four compositions, it can be suggested that the mixed ferrite, sample-4 (x = 0.3), shows the highest Q-factor of all at 1100 °C.

Spinel type nano ferrite compound MgFe2O4 was synthesized through sol gel technique using metal nitrates as precursors. The phase composition, morphology and elemental analysis of magnesium ferrite (MgFe2O4) were performed by X-ray diffraction, fourier transform infrared, atomic force microscopy, energy dispersive x-ray and scanning electron microscopy, analyses. The sample's X-ray diffraction pattern verifies the existence of single phase material, with the size of its crystallites estimated to be 39.9 nm. Fourier transform infrared examination supported metal-oxygen vibrations corresponding to tetrahedral and octahedral sites, respectively. From scanning electron microscopy image, grain size obtained about 97.7 nm. Raman spectra of the sample shows five Raman active modes (A1g + Eg + 3F2g), which is compatible with the spinel structure. Magnetic measurement study at room temperature shows a hysteresis loop behaviour with a low saturation magnetization value, 27.192 emu g-1 and a small coercivity value. The optical band gap determined using UV-visible transmittance spectra. Additionally, X-ray photoelectron spectroscopy are used to confirm oxidation states and explore the chemical composition of the sample.

Investigation the structural and magnetic properties of nanocrystalline Co78Zr17B2Si1W2 alloy during melt spinning and annealing processes were the main goal of this study. In this regard, samples were prepared using vacuum induction melting, melt spinning and subsequent annealing. The specimens were evaluated using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM). Based on results, nanocrystalline Co5Zr single phase with hard magnetic properties (Ms=29.5 emu/g and Hc=2.7 kOe) successfully formed during melt spinning process (at wheel speed of 40 m.s-1). The coercivity value of rapid solidified sample increased to about 3.2 kOe during annealing process up to 400°C. However, more increasing in annealing temperature lead to the transformation of non-equilibrium magnetic Co5Zr phase to stable Zr2Co11 phase, which has distractive effects on final magnetic properties.

The investigation of the structural and magnetic properties of nanocrystalline Co78Zr17B2Si1W2 alloy during melt spinning and annealing processes were the main goals of this study. In this regard, samples were prepared using vacuum induction melting, melt spinning and subsequent annealing. The specimens were evaluated using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM). Based upon the results obtained, nano-crystalline Co5Zr single phase with hard magnetic properties (Ms= 29.5 emu/g and Hc= 2.7 kOe) was formed during melt spinning process (at wheel speed of 40 m.s-1). The coercivity value of rapidly solidified sample increased to about 3.2 kOe during annealing process up to 400°C. However, higher annealing temperature led to the transformation of non-equilibrium magnetic Co5Zr phase to a more stable Zr2Co11 phase, which has negative effects on final magnetic properties. [ABSTRACT FROM AUTHOR]

In this research, CoFeNi thick films were prepared through the electrodeposition process from a natural pH bath containing the complex agent of sodium citrate. By increasing applied current density, there is a transition from BCC (Fe) phase to BCC (Fe) + FCC (Co) phases and then to FCC (Co) phase. The XRD pattern showed a nanocrystalline structure for the CoFeNi thick films which was further confirmed by the TEM images. The magnetic properties of the synthesized magnetic films exhibit a noticeable decrease in the coercivity by decreasing the crystallite size which is consistent with the “D6” law. The resistivity of the CoFeNi thick films increased by decreasing the grain size which is due to the scattering of the charge carriers. The increase in the applied current density results in the gradual substitution of the iron atoms in CoFeNi films by nickel atoms leading to a reduction in saturation magnetization.

• longitudinal magnetic field annealing (FA) and co synergistically affect the microstructure, magnetic domain behavior, and soft magnetic properties of Fe-based amorphous/nanocrystalline alloy. • FA promotes fine nanocrystalline nucleation and suppresses grain growth from amorphous matrix. • FA improves the soft magnetic properties of Fe-based amorphous/nanocrystalline alloy. • Co 16 achieves the best comprehensive soft magnetic properties with b s of 1.85 T, low h c of 1.8 A/m, and exceptional μ e of 26,505 at 1 kHz. This study investigated the enhancement of soft magnetic properties in Fe 83.2-x Co x Si 2.5 B 9.5 P 4 Cu 0.8 (x = 0, 4, 8, 12 and 16 at %) amorphous/nanocrystalline alloys through longitudinal magnetic field annealing (FA). The FA-treated alloys demonstrate superior magnetic performance, achieving a superior saturation flux density (B s) of 1.85 T, ultra-low coercivity (H c) of 1.8 A/m, high effective permeability (μ e) of 26,505 at 1 kHz, and low core loss (0.13 W/kg) at 1.0 T/50 Hz. Microstructural analysis reveals that the FA and Co substitution promotes nanocrystalline nucleation, forming high-density nanocrystals while suppressing grain growth through competitive dynamics and inhibiting element diffusion within the amorphous matrix. Domain observation further confirms that FA facilitates the transition from disordered, non-uniform magnetic to uniform, broad, plate-like domains. These findings elucidate the critical influence of longitudinal magnetic field annealing on microstructure evolution and magnetic domain alignment, which synergistically enhance soft magnetic properties. [ABSTRACT FROM AUTHOR]

In this study, nanocrystalline Fe–Ni–Co ternary alloy powders with the composition of Fe50Ni50-xCox (x = 0–50) were prepared using a high-energy ball milling process after 30 h of milling time. Structure, microstructure, and magnetic properties were investigated in detail as a function of Co concentration using X-ray diffraction technique, scanning electron microscopy, vibrating sample magnetometer, and inductance/capacitance/resistance meter. The results indicate that BCC α-(Fe, Co) and FCC γ-(Fe, Ni) single-phase solid solutions with average crystallite sizes of 15 and 10 nm were formed successfully in Fe50Co50 and Fe50Ni50 alloys, respectively. In addition, there is a mixture of two solid solutions of FCC and BCC phases in the range of Fe–Ni–Co ternary alloy composition (i.e., 5 < × < 45). When Co concentration increases from x = 0 to x = 50, the saturation magnetization and relative permeability improve towards the Fe50Co50 alloy value, while the coercivity worsens from 12.6 to 63.4 Oe. [ABSTRACT FROM AUTHOR]

Recently, there has been an increasing demand for Co-based alloys in modern industrial applications because of their excellent magnetic properties. Therefore, given the importance of obtaining high-quality Co-based alloy, such as Co60Fe18Ti18Si4 (at%), was synthesized using the mechanical alloying (MA) process. The research concerned the microstructural, morphological, and magnetic properties evolution of Co60Fe18Ti18Si4 (at%) alloy powders synthesized by MA in a high-energy planetary ball mill under argon (Ar) atmosphere, at a speed of 300 rpm. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy, and vibrating sample magnetometer analysis were employed to characterize different alloy powdered samples as a function of MA time (10 min–50 h). The XRD result indicates that the synthesized Co-based alloy powder has a widened peak of bcc-(Co, Fe, Ti, Si) solid solution appeared after 50 h of milling time. The crystallite and the lattice strain were achieved to about 8 nm and 1.235%, respectively, after 50 h of milling time. The average particle size was obtained to about 2.727 µm after 50 h of milling time, as observed from SEM analysis. From the VSM analysis, it was observed that the synthesized alloy powders show soft ferromagnetic behaviour. After 50 h of milling time, the magnetic saturation and the coercivity were attained to about 89.68 emu/g and 155.08 Oe, respectively. [ABSTRACT FROM AUTHOR]

NANOMET-type soft magnetic alloys of Fe82Si4B10P3Cu1 and Fe78Si8B10P3Cu1 were studied. Nanocrystalline alloys were prepared by annealing the amorphous precursors at a temperature of 420 °C for 20 and 60 min in vacuum and in Ar atmosphere. The effect of the annealing atmosphere and time of annealing on the alloy structural and magnetic properties were investigated by X-ray diffraction (XRD), Mössbauer spectroscopy (MS), magnetic measurements and atomic force microscopy (AFM). XRD unveiled partial crystallization of the Fe82Si4B10P3Cu1 alloy and confirmed amorphous structure of the Fe78Si8B10P3Cu1 alloy. The technique also indicated larger grain size after annealing in vacuum as compared to that in argon. MS disclosed the effect of the silicon content on the annealed alloys microstructure, namely the lower relative volumetric fraction of the A8 crystalline phase component for the alloy with 8 at. % Si as compared to the alloy with 4 at. % Si. Variations of the parameters reflecting the magnetic microstructure were also observed and are discussed with relation to different annealing times and atmospheres. Magnetic measurements showed better soft magnetic properties for sample with 8 at. % Si whose coercivity was lower as well as the determined magnetization work. They also indicated lower coercivity for argon annealed samples and showed that longer annealing times are reflected in the increased resultant coercivity. For both studied compositions, the AFM measurements inspecting the morphology of the sample surfaces manifested the presence of lower protrusions on the surfaces of the vacuum annealed samples as compared to the argon annealed ones, where also larger agglomerates were disclosed. [ABSTRACT FROM AUTHOR]

Post-annealing effects on microstructure and magnetic properties of Nd-Fe-B die-upset magnets were investigated using the commercial melt-spun flakes with a composition of Nd13.6Fe73.6Ga0.6Co6.6B5.6. The die-upset magnets from the melt-spun flakes were subjected to post-annealing at temperatures ranging from 400 °C to 800 °C for 1 h in vacuum and then again annealed at a constant temperature, 600 °C. The coercivity was largely enhanced about 2.4 kOe after the first post-annealing treatment at 600 °C. However, the coercivity decreased at temperatures except for 600 °C and 700 °C. In the case of high temperature, 800 °C, annealing caused the grain growth, resulting coercivity degradation. After the second post-annealing treatment at 600 °C, the coercivity of the magnets post-annealed at low temperatures below 500 °C increased, whereas the coercivity of the magnets post-annealed at above 700 °C decreased. The $\alpha $ and ${N} _{\mathrm {eff}}$ values obtained from the result of temperature dependence of coercivity increased after post-annealing at 600 °C. These results indicate that post-annealing at 600 °C was effective in improving the grain surface structure, but could induce the local stray field in the magnet. [ABSTRACT FROM AUTHOR]

In general, an air gap plays an important function in the magnetic core. It will enhance the stability of the inductance value of a reactor, increase the power density of the inductor, and optimize the properties of a high-frequency transformer. Hence, it is of great significance to study the influence of the air gap on the properties of magnetic cores. Based on a novel designed tester, the dynamic magnetic properties of the C-type amorphous (AMCC025) core and nanocrystalline (F3CC0125) core with different lengths of the air gaps are measured and analyzed when the cores are excited at different frequencies. In addition, the modified Steinmetz empirical formula which takes the fringing magnetic flux near the air gap into account is proposed. The calculated magnetic properties obtained from the modified formula show great agreement with the measured results. The average prediction error of the modified model is confined in 10%. Both the calculated and experimental results indicate that the influence of the fringing magnetic flux could be ignored when the length of the air gap is less than 5% length of the equivalent magnetic circuit. In particular, the frequency-dependent losses decrease to a minimum value and then increase with the increase in flux density accordingly. The modified loss model and results would be beneficial to the design of high-frequency inductors and transformer cores. [ABSTRACT FROM AUTHOR]

In the present work, the effect of Ni, Mn, Nb, Cr, and Ti elements on microstructural and magnetic properties of nanocrystalline Fe-B-Si alloys was investigated. According to the results, all studied alloys exhibited ferromagnetic behavior with the saturation of magnetization (Ms) in the range of 16–35 emu/g. The coercivity (Hc) values of nanocrystalline Fe60B15Si15X10 (Mn, Ni, Nb, Ti, and Cr) alloys were in the range of 110–390 Oe, which can be classified as semi-hard magnetic property. The nanocrystalline Fe70Si15B15, Fe60B15Si15Mn10, and Fe60B15Si15Ni10 alloys showed low magnetic characteristics as a result of the formation of non-magnetic Fe-Si-B intermetallic phases. In contrast, Nb, Ti, and Cr elements prevent from the formation of non-requested ternary phases and Fe60B15Si15Nb10, Fe60B15Si15Ti10 and Fe60B15Si15Cr10 showed better magnetic behaviors. Among all compositions, the nanocrystalline Fe60B15Si15Nb10 alloy exhibited the highest values of saturation of magnetization and coercivity of about 51 emu/g and 381 Oe, respectively. [ABSTRACT FROM AUTHOR]

The spinel ferrites Co0.3Cd0.7Zn1.5xFe2−xO4 were synthesized via microemulsion method. Thermogravimetric analysis (TGA) was employed to find annealing temperature. Crystallite size, lattice constant, cell volume, x-ray density, bulk density, dislocation density, micro strain, lattice strain and stacking faults were calculated by x-ray diffraction (XRD) data. XRD analyses confirmed the spinel structure. The observed frequency bands were analyzed through Fourier transformation infrared spectroscopy (FTIR) which confirmed that the substitution of zinc occupy the tetra and octahedral sites. Field emission scanning electron microscopy (FESEM) showed the spherical shape, spinel ferrites with high surface area to volume ratio. The shift in diamagnetic to ferromagnetic behavior was observed with increasing zinc concentration through vibrating sample magnetometer (VSM). The magnetic results indicate that the best application for the prepared spinel ferrites can be obtained at high concentration of zinc substitution with an iron deficiency which can be used as sensors and high storage magnetic devices. [ABSTRACT FROM AUTHOR]

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We report the structural, magnetic, and magnetocaloric properties of the nanocrystalline BaCo1-yMnyO3-δ (0 ≤ y ≤ 0.3) samples synthesized by sol-gel method. The samples crystallized into different hexagonal polytypes as a function of composition and annealing temperature. The crystal structure of parent BaCoO3 (y = 0) changed from 2H- to mixed 2H+10H (y = 0.3) through 2H+12H (y = 0.2) hexagonal phase for 900 °C annealed samples. The increase in annealing temperature reduces the fraction of face sharing octahedra, and the crystal structure of 1100 °C samples exhibited 2H+12H, 12H, 12H+10H, and 2H+10H- hexagonal phases. The relationship between structural and magnetic properties is explained by the structural spin model projection. The 2H- and 10H-hexagonal phases exhibited antiferromagnetic ordering, whereas 12H- phase attributed to ferrimagnetic ordering. The critical exponent analysis indicates that the 12H- hexagonal phase exhibits mean-field approach and the other mixed hexagonal polytypes do not follow any universal model. [ABSTRACT FROM AUTHOR]

Machine learning was utilized to efficiently boost the development of soft magnetic materials. The design process includes building a database composed of published experimental results, applying machine learning methods on the database, identifying the trends of magnetic properties in soft magnetic materials, and accelerating the design of next-generation soft magnetic nanocrystalline materials through the use of numerical optimization. Machine learning regression models were trained to predict magnetic saturation (B S), coercivity (H C) and magnetostriction (λ), with a stochastic optimization framework being used to further optimize the corresponding magnetic properties. To verify the feasibility of the machine learning model, several optimized soft magnetic materials – specified in terms of compositions and thermomechanical treatments – have been predicted and then prepared and tested, showing good agreement between predictions and experiments, proving the reliability of the designed model. Two rounds of optimization-testing iterations were conducted to search for better properties. [ABSTRACT FROM AUTHOR]

• Finemet flake amorphous powder was used as raw material for magnetic powder cores and its annealing process was investigated, and an industrial insulation coating process was used: the phosphate passivation process. • The effect of silicone resin type on the compactibility and soft magnetic properties of magnetic powder cores was investigated. • The magnetic properties of magnetic powder cores were improved using warm compaction and the mechanism of the improvement was analyzed. In this paper, Finemet flake amorphous powder with poor flowability is used as raw material to investigate the effect of the type of silicone resin and compaction method on the density and soft magnetic properties of the magnetic powder cores. The results show that due to the different thermal stability of the three silicone resins 600, S2 and JH, the permeability of the three magnetic powder cores has significant differences. Since the lubricant is in a viscous flow state during the warm compaction and reduces the friction between the particles, the density of the magnetic powder cores is increased, which further improves the soft magnetic properties of the magnetic powder cores. Among them, the density of Finemet magnetic powder cores prepared by warm compaction with the S2 silicone resin as binder is 5.62 g∙cm−3, the permeability is 43.86, the DC bias capability is 66.77 % at 100 Oe, and the total loss is 113.94 mW∙cm−3 (100 kHz, 50 mT), which has excellent comprehensive soft magnetic properties and is a very significant improvement compared with cold compaction. This shows that the warm compaction process is an effective method to further improve the soft magnetic properties of magnetic powder cores. [ABSTRACT FROM AUTHOR]

Nowadays, increasing energy efficiency in the automotive industry is promoted by employing compact electrical systems. This reduction in the mass and volume of electrical systems exposes magnetic components to high temperatures for extended periods. The present paper investigates the magnetic behavior of FeCuSiNbB nanocrystalline materials across various temperature ranges. Subsequently, the temperature dependency is reevaluated after exposing the magnetic cores to aging at 200 °C. The entire study is founded on monitoring the evolution of macroscopic magnetic properties and analyzing anisotropic energies. [ABSTRACT FROM AUTHOR]

Thermal and magnetic properties of Fe 85- x Si 2 B 8 P 4 Cu 1 Nb x (0 ≤ x ≤ 4) alloy ribbons of different microstructures were systematically investigated. Increase in Nb content raised the first crystallization onset temperature from 646 to 701 K suggesting improved thermal stability. XRD results on the as-spun ribbons also suggested the role of Nb increasing the thermal stability and glass-forming ability by showing fully amorphous patterns for all alloys with Nb addition. However, Nb addition turned out to decrease the saturation magnetic flux density from 1.74 to 1.17 T. To further optimize the properties, annealing treatment was carried out to find the optimized condition as Fe 84 Si 2 B 8 P 4 Cu 1 Nb 1 processed at 793 K for 10 min resulting in nanocrystalline microstructure with a high saturation magnetic flux density of 2.03 T. Transmission electron microscopy confirmed the formation of nanocrystalline α-Fe phase in the annealed ribbons. • Glass-forming ability and thermal stability are improved as Nb increases at (0 ≤ x ≤ 4). • Nb (x = 1) alloy is annealed at 793 K for the best magnetic properties up to 2.03 T. • High-quality nanocrystals were created, benefiting the development of soft magnets. [ABSTRACT FROM AUTHOR]

Room temperature soft ferromagnetism has been detected in nanocrystalline ZnO while doping with Bi as a heavy non-magnetic atom. The Zn1−xBixO (x = 0.0, 0.01, 0.03, and 0.05) system was synthesized by chemical co-precipitation. To investigate the origin of this enhanced ferromagnetism, characterization of crystal structure, lattice dynamics, and magnetic properties has been achieved. The presence of only one wurtizite single phase of nanocrystalline ZnO was confirmed through Rietveld analysis. The gradual increase of the c parameter also reflected complete solubility of Bi in the wurtizite lattice up to x = 0.05. Bi was detected to occupy the position 2b (1/3, 2/3, 0) of Zn. A drastic decrease of the crystallite size to less than its half value was also detected. Well-defined intercrystallite boundaries were imaged by HR-TEM. ESR studies revealed a moderate increase of the free spin density while the g values gave evidence of the formation of defects like VO+, VZn, and (BiZn–VZn) complex. Considerable increase of magnetic moment was found as Bi content increased to 0.05. We believe that the enhancement of ferromagnetism in Bi-doped ZnO can be attributed to an ensemble of key factors: free spins, vacancy defects, and the formation of nanocrystallites with intergranular layers within a threshold limit. [ABSTRACT FROM AUTHOR]

In this current study, nanocrystalline Dy powders were prepared by melt-spinning and subsequent high-energy ball-milling. The effect of ball-milling time on the structure and magnetic properties of the powders was studied. The crystal structure and microstructure of the melt-spun ribbons and ball-milled powders were observed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Magnetic measurement of all samples was performed with vibrating sample magnetometer (VSM). XRD results indicate that the average crystal grain size of the powders decreases from 90.09 nm of the ribbons to 10.42 nm of the 4-h ball-milled powders. Further TEM observation shows that the grains are fine and uniform. The Neel temperature (TN) decreases from 182 K of the ribbons to 172 K of the powders, while the Curie temperature (TC) increases from 100 to 130 K, demonstrating that the grain size has substantial influence on the magnetic transition process. Moreover, at 60 K, as the ball-milling time increases, the coercivity of the powders increases first, peaking at 0.48 T for 2-h milling, then drops again, while the remanence of the powders decreases monotonically. As a result, the powders milled for 2 h exhibit an optimal maximum energy product of 64.0 kJ·m−3, demonstrating the good potential of these powders as a permanent magnet at low temperatures. [ABSTRACT FROM AUTHOR]

• Effect of Co addition on ultra-rapidly annealed HiB-Nanoperm investigated. • Nanocrystalline (Fe 0.8 Co 0.2) 87 B 13 displays a J s of 2.02 T and a H c of 9.3 A/m. • Addition of 1 at.% Cu improves magnetic softness for Co-containing HiB-Nanoperm. • (Fe 0.8 Co 0.2) 86 B 13 Cu 1 displays a J s of 2.00 T and a H c of 7.0 A/m. • Ultra-rapid annealing required for magnetic softness in Co-containing HiB-Nanoperm. The effect of Co on the magnetic properties of ultra-rapidly annealed (heating rate > 104 K/s, annealing time < 1 s) nanocrystalline (Fe 1−x Co x) 87 B 13 with x = 0–0.5 has been investigated. A saturation magnetic polarization of 2.02 T is observed for x = 0.2 while maintaining a coercivity of 9.3 A/m. This represents a 0.1 T increase over existing Co-free HiB-Nanoperm alloys with a B content of 13 at.% and is directly comparable to conventional crystalline Fe-3 wt%Si. Ultra-rapid annealing is shown to be a requirement for producing magnetically soft materials in this alloy system. The effect of Cu on ultra-rapidly annealed nanocrystalline (Fe 0.8 Co 0.2) 87−y B 13 Cu y where y = 0–1.5 is also investigated. It is found that Cu is effective at improving the magnetic softness of Co-containing HiB-Nanoperm, with y = 1 displaying a H c of 7 A/m and a saturation magnetic polarization of 2.0 T. [ABSTRACT FROM AUTHOR]

Nanocrystalline of ZnAl 2 O 4 spinel was synthesized by employing the microwave combustion method. Different new spinel compositions of formula Zn 1- x Fe x Al 2 O 4 , (0.0 ≤ x ≤ 1.0) were prepared by substitution of Zn ions with Fe ions. The as-synthesized resultant material ZnAl 2 O 4 with spinel structure as well as Zn 1- x Fe x Al 2 O 4 compositions were characterized by Energy Dispersive X-ray and X-ray diffraction. Morphology and particle size evaluation of the nanoparticles were characterized by transmission electron microscopy images. The optical absorption spectra and the magnetization were measured at room temperature for each Fe ratio. The substitution effect of Fe ions on the optical and magnetic properties of the original spinel was studied. The optical absorbance showed that the optical band gap decreased with increasing Fe ratio. • New nanocrystalline spinels of Zn 1- x Fe x Al 2 O 4 were synthesized by combustion. • XRD and FTIR spectra confirm the spinel structure for each Zn 1- x Fe x Al 2 O 4 sample. • The energy band gap decreases with increasing the ratio of Fe ions. • The magnetization increases with increasing Fe ions content. [ABSTRACT FROM AUTHOR]

High density MnAl–C magnets with enhanced coercivity and remanent magnetization were prepared by high-pressure compaction of the τ -phase obtained by annealing the as-prepared gas-atomized powders, which are spherical in shape with size in the range of 1–7 μm. The as-prepared gas-atomized powders were composed of ε - as the major phase and γ2 - as the minor phase. The massive phase transformation of ε → τ in the gas-atomized powders occurs at 720 K and accomplishes at 806 K, both of which are lower than those of the water-quenched ε -MnAl–C alloys with the same composition. An optimized temperature of 760 K, at which the decomposition of metastable τ -phase was minimized, was selected to prepare the ferromagnetic τ - from the ε -phase. The spherical τ -phase powders were pressed at room temperature into two dimensional plates that stack along the direction of compaction, forming high density (98.6%) bulk magnets that exhibit larger coercivity and higher remanent magnetization than that of the τ -phase powders. The grain size of the compacted samples was observed to be in the range of 10–100 nm. The coercivity (0.34 T) of the dense samples is twice as large as that of the τ -phase powders, owing to the refined grain size and enlarged dislocation density resulting from high-pressure compaction. [ABSTRACT FROM AUTHOR]

In this work, we reported a detailed study on the synthesis, structural and magnetic properties of nanocrystalline La0.8Sr0.2MnO3. The synthesized nanoparticles were prepared using a sol–gel method and characterized using X-ray diffraction and high-resolution transmission electron microscope. The average particle size was found in the range from 40 to 45 nm. The magnetization versus temperature M(T) measurements as well as magnetization field dependence M(H) have been investigated using vibrating-sample magnetometer. The magnetization as a function of temperature M(T) indicated a broad second-order magnetic phase transition from ferromagnetic state to paramagnetic state in the Curie temperature region (320–340 K). The magnetocaloric effect of the sample has been estimated and presented a maximum magnetic entropy change |ΔSM|max = 0.86 J kg−1 K−1 with relative cooling power = 62.12 J kg−1 at magnetic field (H) = 2T. Based on the result of magnetocaloric properties, the investigated sample could be considered as a good refrigerant material for near room temperature magnetic refrigeration. [ABSTRACT FROM AUTHOR]

• Aging of nanocrystalline materials results from a modification in the induced anisotropy initially created during annealing. • Aging of nanocrystalline materials depends mainly on the magnetic state. • Applying DC magnetic field during aging creates a uniform anisotropy. • Uniform anisotropy can be induced at low temperatures than annealing temperatures, but with longer duration. • All grades transform to square loop if a DC magnetic field is applied in the ribbon's axis during aging. One of the main problems in reducing the volume of electrical systems is the exposure of components, such as magnetic cores, to high temperatures. These severe conditions degrade their properties not only instantly (reversible phenomena) but also over time (irreversible phenomena due to aging). The aging of nanocrystalline materials has been studied in a few works, either in their demagnetized state or their residual magnetization state. However, these conditions do not represent the real operating environment. This paper addresses this issue by studying the aging of nanocrystalline materials in the presence of a DC magnetic field. The study concerns three grades of nanocrystalline cores, characterized by their B-H loop shapes: round, flat, and square. The investigation focuses on the monitoring of macroscopic magnetic properties, followed by an analysis of anisotropic energies and their role in aging mechanisms. [ABSTRACT FROM AUTHOR]

We report on an experimental and theoretical investigation of the microstructural and magnetic properties in nanocrystalline Pr 2 Co 7-x Fe x compounds. The exchange interactions (J ij) and Curie temperature (T C) values were theoretically determined using mean field theory (MFT), and the results were found to be in excellent agreement with experimental data. The dependence of macroscopic and microscopic magnetic properties on the Fe content (x) was investigated, considering the model of random magnetic anisotropy. The saturation approach (SA) was utilized to analyze magnetization curves (M(H)), and various magnetic parameters, including random anisotropy fields (H a) and local random anisotropy constant (K 1), were studied. It was observed that these parameters increase with increasing Fe content up to x = 0.5 and then decreased for x > 0.5. Moreover, the coercivity (H C) was analyzed using the Herzer model by taking into account the grain size (D) and exchange correlation length (R f). The experimental H C values were consistent with those derived from the random anisotropy model. Electronic structure calculations based on density functional theory (DFT) were performed to further understand the impact of Fe substitution and the improvements in magnetic performance. The collective findings provide valuable insights into the magnetic properties and behavior of nanocrystalline Ce 2 Ni 7 -type Pr 2 Co 7-x Fex compounds, aiding in the understanding and design of advanced magnetic materials. [ABSTRACT FROM AUTHOR]

Rapid solidification process (RSP) has been widely used to fabricate Fe-based nanocrystalline alloys. To obtain amorphous structure after RSP, the number of Fe elements in the nanocrystalline alloys is limited by the amount of amorphous forming elements. Recently, strong demand for high energy efficiency electronic devices has pushed researchers to make Fe-based alloys with high magnetic flux density. However, this high Fe concentration for high magnetic flux density deteriorates the thermal stability of the amorphous structure. This means that an annealing process after RSP is critical to obtain excellent alloy magnetic properties. In this paper, to enhance the soft magnetic properties of amorphous Fe–B–Cu–C ribbons, changes in the microstructure during annealing have been investigated. [ABSTRACT FROM AUTHOR]

Pseudobrookite (Fe2TiO5) is a semiconductor with numerous potential applications. Lowgrade ilmenite ore has been used as an inexpensive source of Fe and Ti for preparation of Pseudobrookite. Ilmenite was first leached with 20% hydrochloric acid for 3 h at 70°C. Co-precipitation of soluble Fe and Ti from the rich filtrate was carried out at pH ≥ 9.1 followed by calcination at different temperatures (900-1300oC) for 2 h. X-ray diffraction patterns (XRD) showed that a single-phase nanocrystalline pseudobrookite powder was produced. The pH was a critical parameter for the evolution of formation the different sizes, structural morphology, and the magnetic properties of the product. Scanning electron microscope (SEM) images showed that particles synthesized at pH 11.2 contained more agglomerations and were more porous than those synthesized at pH 9.1. As the calcination temperature increases, the Fe2TiO5 changes from a small rod-like structure to an elongated rod-like structure, and finally to interconnected aggregated crystals. The magnetization of the synthesized Fe2TiO5 was measured using a vibrating sample magnetometer (VSM) and was found steadily increase with increasing calcination temperature from 1000 (≈9 emu/g) to 1300°C (16 emu/g). Such a large saturation of magnetization might be due to the high phase purity and well-defined crystallinity of Fe2TiO5. [ABSTRACT FROM AUTHOR]

In the present study, the structural and magnetic characteristics of nanocrystalline Co82Zr18 alloy with different structure and crystallite sizes were investigated. In this regard, the nanocrystalline Co82Zr18 sample with different structure and crystallite sizes were prepared using a copper boat vacuum induction melting plus melt spinning and subsequent annealing processes. The prepared samples were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), and vibrating scanning magnetometer (VSM). According to achieved results, single-phase structure of Zr2Co11 can successfully form by means of melt spinning process at wheel speed of 40 m/s. The melt-spun ribbons exhibit hard magnetic properties with the coercivity and saturation of magnetization in the range of 2.3 kOe and 58 emu/g, respectively. The highest value of coercivity in Co82Zr18 alloy was estimated to be about 3 kOe in annealed sample at 500∘C for 1 h. [ABSTRACT FROM AUTHOR]

We report the structural, magnetic, and electrical transport response of nanocrystalline SrCo0.5Mn0.5O $_{3-\delta }$ compound synthesized by the sol–gel method. X-ray diffraction pattern shows that the sample crystallizes in the hexagonal crystal structure with cubic stacking at room temperature. The compound retains its structural symmetry down to 20 K. The transmission electron microscopy image confirms the surface morphology of the nanocrystalline sample, and the average particle size was found to be ~90 nm. Temperature dependence magnetization data show bifurcation in the zero field cooled (ZFC) and field cooled (FC) magnetization measured under the applied magnetic field of 500 Oe with onset irreversible temperature $T_{\mathrm {irr}} \sim 242$ K. At low temperature, the small peak has been observed in ZFC curve, suggesting the spin blocking below $T_{B}\sim 35$ K. The peak has disappeared on the application of higher magnetic field, and the magnitude of bifurcation has also been reduced. The electrical transport data reveal semiconducting such as behavior and follow Mott’s variable range hopping (VRH) conduction mechanism in the temperature range 260–300 K. The density of states in the vicinity of Fermi energy is found to be N $(E_{F}) \sim 5.702 \times 10^{18}$ eV $^{-1}\cdot \text {cm}^{-3}$ using the VRH fit. The density of state value is in good agreement with the other reported semiconducting oxides. It shows maximum positive magnetoresistance of ~7% at 200 K for the magnetic field change of 3 T. [ABSTRACT FROM AUTHOR]

In this paper, the Rare-earth Iron Boron (RE-Fe-B) magnets were fabricated successfully by using the double main phase method through mixing the Neodymium Iron Boron (Nd-Fe-B) powders and Misch-metal Iron Boron (MM-Fe-B) powders with different ratio. Aiming at the nanocrystalline RE 2 Fe 14 B magnets prepared by using spark plasma sintering technology, phase structure and magnetic properties were investigated. It is found that the Misch-metal (MM) alloys promote the domain nucleation during the the process of magnetization reversal and then damage the coercivity ( H cj ) of isotropic RE 2 Fe 14 B magnets, while the H cj could still remain more than 1114.08 kA/m when the mass proportion of MM (simplified as: “a”) is 30%. Curie temperature and phase structure were also researched. Two kinds of mixed-solid-solution (MSS) main phases with different Lanthanum (La) and Cerium (Ce) content were believed to be responsible for the two curie temperature of the RE 2 Fe 14 B magnets with “a” ≥20%. This is resulted from the inhomogeneous elemental distribution of RE 2 Fe 14 B phase. [ABSTRACT FROM AUTHOR]

(Fe 1−x Ga x) 92 Zr 8 amorphous and nanocrystalline alloys with x = 0.15 to x = 0.36 were investigated to improve the magnetic softness of Galfenol-type alloys and to evaluate their magnetostrictive properties. The samples were prepared by melt spinning of arc melted ingots. The rapidly solidified ribbons were annealed at 823 K for 1 h to produce a nanocrystalline structure. X-ray Diffraction data showed that after annealing, body-centered cubic (BCC) Fe-Ga phase crystallized for x = 0.15 to x = 0.26. When x exceeded 0.26, the ribbons crystallized into BCC and a ternary intermetallic phase (i.e., ZrFe 6 Ga 6) which has deteriorating effect on saturation magnetization, magnetic softness and magnetostriction coefficient. The annealed ribbons' saturation magnetization value decreases from 126 Am2/kg to 54 Am2/kg as the Ga content increased from x = 0.15 to x = 0.36. The alloy with x = 0.26 annealed at 823 K for 1 h shows a peak magnetostriction of 10 ppm with saturation magnetization of 110 Am2/kg and coercivity of 260 A/m. • Amorphous Fe-Ga-Zr ribbon was produced by rapid solidification (melt-spinning). • Synthesized Galfenol (Fe 1−x Ga x) nanocrystalline grains by annealing the amorphous Fe-Ga-Zr ribbons. • Soft-magnetic property of nanocrystalline Galfenol was analyzed using random anisotropy model. • The nanostructure-amorphous composite resulted small magnetostriction. [ABSTRACT FROM AUTHOR]

Structural, magnetic and magnetocaloric properties of the nanocrystalline La 0.7 Te 0.3 Mn 0.7 Co 0.3 O 3 perovskite manganite were investigated. X-ray diffraction pattern indicated that the nanocrystalline sample crystallized in orthorhombic crystal structure with Pbnm space group. The average particle size was calculated using scanning electron microscope and it was found to be ∼150 nm. Temperature dependence magnetization measurements revealed ferromagnetic–paramagnetic phase transition and the Curie temperature (T C ) was found to be ∼201 K. Field dependence magnetization showed the hysteresis at low temperature with a coercive field of ∼0.34 T and linear dependence at high temperature corresponds to paramagnetic region. Based on the magnetic field dependence magnetization data, the maximum entropy change and relative cooling power (RCP) were estimated and the values were 1.002 J kg −1 K −1 and 90 J kg −1 for a field change of 5 T respectively. Temperature dependent resistivity ρ(T) data exhibited semiconducting-like behavior at high temperature and the electrical transport was well explained by Mott’s variable-range hopping (VRH) conduction mechanism in the temperature range of 250 K–300 K. Using the VRH fit, the calculated hoping distance (R h ) at 300 K was 54.4 Å and density of states N(E F ) at room temperature was 7.04 × 10 18 eV −1 cm −3 . These values were comparable to other semiconducting oxides. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis of nanocrystalline La 1-x Ca x B 6 (0 ≤ x ≤ 1) hexaboride powders by solid-state reaction and their subsequent consolidation via spark plasma sintering. The structural, magnetic and thermionic emission properties of La 1-x Ca x B 6 hexaboride are investigated. All of the synthesized nanocrystalline hexaboride powders are single phase with the CsCl -type structure and no ferromagnetic impurity phases have been detected from X-ray diffraction. Magnetic measurements show that weak ferromagnetism at room temperature is found in nanocrystalline La 1-x Ca x B 6 hexaboride powders, and the magnetism was attributed to the presence of the intrinsic defects, based on the data of the HRTEM. Thermionic emission measurements indicate that the maximum emission intensity for bulk La 0.4 Ca 0.6 B 6 at 1873 K reached 20.02 A/cm 2 , which is more than three times higher as compared to bulk CaB 6 (∼6.04 A/cm 2 ). When the La doping was increased to 40 at%, the work function of CaB 6 decreased from 2.95 to 2.76 eV, indicating an improvement in the thermionic emission performance. Therefore, the quasibinary La 1-x Ca x B 6 hexaboride may have an application as a promising cathode. [ABSTRACT FROM AUTHOR]

Nanocrystalline Mg 0.6 Cd 0.4 Fe 2 O 4 ferrite powders were produced by the glycine-nitrate auto-combustion method for the first time. The influence of the different molar ratios of glycine-to-nitrate G.N −1 ) on the characteristics of the prepared powders was systematically investigated by X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FE-SEM) and vibrating sample magnetometry (VSM). Thermodynamic calculations revealed that the adiabatic flame temperature changes from 598.79 K to 1757.97 K by increasing the G.N −1 ratios from 0.30 to 0.85. The results confirmed that under fuel-lean combustion ( G.N −1 = 0.30), Mg 0.6 Cd 0.4 Fe 2 O 4 nanoparticles can be obtained at a significantly lower temperature and shorter synthesis time, compared to other preparation methods like standard ceramic and co-precipitation. The XRD and ICP results showed that the crystallite size of the powders changes in the range of 8–43 nm, and their Cd content notably decreases with increasing the G.N −1 values. The FE-SEM results proved that the porosity and size of the as-prepared ferrite nanoparticles drastically change with variations in the G.N −1 ratio. The evolution of phase, crystallite/particle size, and magnetic properties after annealing was discussed in detail. At the optimized annealing condition, the synthesized Mg 0.6 Cd 0.4 Fe 2 O 4 ferrite offered a high saturation magnetization of 41.70 Am 2 kg −1 and a coercivity of 1.92 kA m −1 , indicating noticeably better soft magnetic properties compared to the same ferrite produced by the other wet chemical methods. [ABSTRACT FROM AUTHOR]

The pure as well as nitrogen incorporated nickel ferrite (NFO and N-NFO) thin films were grown by radio frequency magnetron sputtering technique. The structural investigations of as-grown N-NFO films using GIXRD and Raman spectroscopy revealed nanocrystalline nature of the films. The microstructural and surface studies of the films using SEM and atomic force microscope micrographs showed increase in crystallite size and decrease in surface roughness with increase of sputtering power. The magnetization (M-H) measurements at 20 and 300 K revealed an increase in magnetization and decrease in coercivity values with increase of sputtering power. However, no saturation of magnetization ( Ms ) was visible for the thin film samples, indicating superparamagnetic behavior due to nanocrystallinity. The comparison of in-plane and out-of-plane magnetizations of the N-NFO film (both at 20 and 300 K) showed that the easy magnetization direction lied in the plane of the film. The optical transmission spectra revealed decrease of direct band gap with increase of sputtering power. [ABSTRACT FROM AUTHOR]

To reduce the cost of the Nd–Fe–B magnets, the Ce element was suggested to be used as a replacement of Nd element. In this paper, nanocrystalline (Ce1–xNdx)16Fe78B6 ( x = 0 –0.7) alloys were prepared by melt spinning. The X-ray diffraction (XRD) results indicate that the alloys are composed of (NdCe)2Fe14B (2:14:1) phase and (CeNd)Fe2 (1:2) phase for 0 < 0.6, and the 1:2 phase was replaced by (NdCe) _{1+\varepsilon } Fe4B4 (1:4:4) phase when x = 0.6 and 0.7. The hyperfine parameters characteristics of the 2:14:1 phases were estimated from 300 K 57Fe Mössbauer spectra, as well as their contents and those of other intergranular phases. In addition to the 2:14:1, 1:2, and 1:4:4 phases, a small content of the rare earth-rich phase was also detected in all the alloys, which was not able to be observed by the XRD characterization. Based upon the hyperfine field, the average magnetic moment of Fe in 2:14:1 phase could be determined as 1.56, 1.62, 1.67, 1.73, 1.78, 1.83, 1.85, and 1.91~\mu \text {B} for x = 0 , 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, and 0.7, respectively. The minor change between the x = 0.5 ( 1.83~\mu _{\text {B}}) and x = 0.6$ ( 1.85~\mu _{\text {B}}) is discussed. Both the present local and macroscopic magnetic parameters significantly contribute to understand the fundamental role of Ce in those nanocrystalline Nd–Ce–Fe–B permanent magnets. [ABSTRACT FROM AUTHOR]