Enhancement Of Magnetic Properties Research Articles

The enhancement of optic and magnetic properties induced by intrinsic strain in Bi(Mn0,5Ti0,5)O3 modified BiFeO3 bismuth ferrite

The enhancement of optic and magnetic properties induced by intrinsic strain in Bi(Mn0,5Ti0,5)O3 modified BiFeO3 bismuth ferrite

Enhancement of ilmenite magnetic properties by oxidation roasting and magnetic separation

Oxidation roasting was proposed to treat the problem of the weak magnetic properties of ilmenite. The effects of roasting temperature, roasting time and cooling method on the results of ilmenite magnetic separation were studied. At the same time, the mechanism of the oxidation roasting process was analyzed by XRD, VSM, SEM-EDS. Determine ilmenite suitable oxidation roasting conditions for roasting temperature 750 °C, roasting time of 20 min, and cooling method of air cooling; at this time, the yield of 96.79% can be achieved in the magnetic field intensity of 238.74 kA/m. The XRD results showed that phase changes in the roasting process occur in the order of ilmenite to hematite and rutile to pseudobrookite. The results of VSM showed that the maximum specific magnetization coefficient of ilmenite increased from 3.25×10<sup>-5</sup> m<sup>3</sup>/kg to 5.58×10<sup>-5</sup> m<sup>3</sup>/kg after roasting, and the magnetic property was enhanced. The results of SEM-EDS showed that the phase transition of ilmenite during the roasting process occurs in a spatial order from the edge of the particles to the interior.

Simultaneous enhancement of magnetic properties and flexural strength in 2:17 type SmCo magnets induced by spherical WO3 particles doping

The influence of spherical WO3 particles doping on the flexural strength and magnetic properties of Sm(CobalFe0.23Cu0.07Zr0.02)7.8 magnets was investigated. As the doping amount increased from 0 wt% to 2.0 wt%, the magnetic properties initially exhibited an increase followed by a decrease, with coercivity increasing from 32.77 kOe to 36.01 kOe and remanence increasing from 11.16 kGs to 11.28 kGs at a doping amount of 0.5 wt%. Moreover, the flexural strength consistently rose from approximately 80 MPa to 127 MPa, representing a significant increase of about 59 %. The presence of WO3 particles optimizes the magnet’s orientation and Cu distribution in the cell boundary phase, thereby enhancing both remanence and coercivity. Additionally, a significant decrease in grain size from 72.04 μm to 33.41 μm was observed, accompanied by a noticeable increase in the content of Sm2O3 phase, which positively contributes to the enhancement of flexural strength. Our research presents a novel technical approach for simultaneously enhancing the magnetic and mechanical properties of 2:17 type SmCo magnets.

Synergistic influence mechanism of B-Ga content on microstructures and magnetic properties of Nd-Fe-B ribbons

To understand the influence mechanism of B and Ga content on magnetic properties of NdFeB ribbons, Nd29.89FebalGayCo5.93Bx (wt%, x = 0.80–0.98, y = 0.24–1.04) alloys were prepared and magnetic properties, phase composition, coercivity mechanism, and microstructure of these alloys were investigated systematically. The melt-spun ribbons exhibited 2:14:1 phase grains with varying grain sizes and amorphous grain boundary phases at a wheel speed of 25 m/s. By reducing the B content within a specific range, grain refinement was achieved, resulting in narrower triangular grain boundaries, more uniform and continuous thin grain boundaries. Meanwhile, further increasing the Ga content, the grain shape changes from elongated to equiaxed, and the grain size is greatly refined. However, for x = 0.89, y = 0.84 strip, the coercivity is still reduced due to the large number of directly contacted grains. Consequently, an alloy composition of Nd29.89FebalGa0.64Co5.93B0.89 yielded excellent comprehensive magnetic properties, including a remanence of 8.5 kGs and a coercivity of 18.01 kOe. The corresponding magnetic properties enhancement mechanism is further discussed.

Calcination temperature effect on formability and magnetic properties enhancement of anisotropic Ca-La-Co substituted M-Type Sr-hexaferrites permanent magnets

In this study, Ca-La-Co substituted M-type Sr-Hexaferrites (Ca0.35La0.47Sr0.18Fe10.87Co0.22O19-δ) were prepared via conventional solid-state reaction, with the calcination temperature ranging from 1240℃ to 1290℃. The grain size of the calcined powder increased with the elevation of calcination temperature, and XRD characterization confirmed the formation of Sr-hexaferrite structure at higher temperatures. SEM analysis revealed hexagonal grain morphologies in the calcined samples. Additionally, the microstructure of the fine-milled magnetic powder transitioned from ultrafine particles to larger plate-like granules as the calcination temperature increased. Remarkably, the remanence (Br) showed an upward trend with increasing calcination temperature, peaking at 4571 Gauss, while the intrinsic coercivity (iHc) reached an optimized value of 5306 Oe at 1280℃. Notably, the formability of M-type Sr-hexaferrites was influenced by the calcination temperature, with the sintering radial shrinkage rate (Sh-D) being <12 % and the required molding pressure of magnetic powder being <500 kg/cm2, both contributing to improved yield and cost-effectiveness in ferrite permanent magnet production. These findings effectively address previous challenges associated with achieving high characteristics and formability, leading to comprehensive enhancements in magnetic properties, operability, and production efficiency. The anisotropic Ca-La-Co substituted M-Type Sr-hexaferrites permanent magnets produced in this study emerge as promising candidates for high-performance rare-earth-free permanent magnets, particularly showcasing the optimal effects achieved at the calcination temperature of 1280℃.

Strong magnetodielectric effect in Bi(La)Fe(Cr)O3 multiferroic nanomaterials

The Bi1-xLaxFe1-yCryO3 (x = 0.00, 0.06; y = 0.00, 0.03, 0.06, 0.09, 0.12) nanomaterials have been synthesized using the simple solvo-thermal technique. The Rietveld refinement of XRD analysis using FullProf Software confirms that all synthesized materials follow rhombohedral perovskite crystal structure of R3C space group. The dielectric and ac conductivity data are analyzed to understand the role of grain and grain boundary contributions. The enhancement of magnetic properties has been observed from SQUID measurement for the co-doped samples at room temperature. Also, a significant improvement in polarization has been observed for the doped nanocompounds from the ferroelectric hysteresis loop. The magneto-dielectric study reveals a large improvement in our co-doped BFO nanomaterials and the value is nearly three times of those reported earlier. The calculated energy storage efficiency for the co-doped samples are found to have as high as 51 %. The sample with x = 0.06 and y = 0.09 with a magneto dielectric coefficient of around 30 % and energy storage efficiency of 35 % is the most suitable for both spintronic and energy storage devices.

Improved properties of CoFe2O4@rGO/PVDF composites prepared through a solution-mixing approach

In this work, a hybrid material based on CoFe2O4 nanoparticles immobilized on reduced graphene oxide (CoFe2O4@rGO) was successfully synthesized through a one-step green solvothermal method. Subsequently, the resultant CoFe2O4@rGO was further modified by aminopropyltriethoxysilane to form the A-CoFe2O4@rGO hybrid, serving as the filler of poly(vinylidene fluoride) (PVDF). The facile preparation of A-CoFe2O4@rGO was confirmed through various microstructural characterization techniques. PVDF-based composites with varying contents of A-CoFe2O4@rGO (1 wt%, 3 wt%, 5 wt%, 7 wt%, and 10 wt%) were prepared using a solution-mixing approach. SEM results revealed uniform distribution of the A-CoFe2O4@rGO filler within the PVDF matrix. The XPS results indicated an obvious interfacial interaction between the A-CoFe2O4@rGO filler and PVDF matrix. Consequently, the crystallization degree and β crystalline content of PVDF matrix in the A-CoFe2O4@rGO(7 wt%)/PVDF composite were enhanced to 52.3 % and 32.1 %, respectively, compared to 42.2 % and 26.0 %, respectively, in pure PVDF. The A-CoFe2O4@rGO(10 wt%)/PVDF composite enhanced electrical conductivity and dielectric constant at 100 Hz, with values of 1.33 × 10−7 S/m and 22.1, respectively, compared to 1.86 × 10−9 S/m and 8.6, respectively, in pure PVDF. In addition, despite the non-magnetic nature of pure PVDF, the A-CoFe2O4@rGO(10 wt%)/PVDF composite possessed a magnetization value of 1.64 emu/g at 60,000 Oe. The comprehensive enhancement in crystallization behavior, electrical, dielectric, and magnetic properties demonstrates the potential of the A-CoFe2O4@rGO/PVDF composite for various applications.

Enhanced structural, magnetodielectric, and multiferroic response in Fe and Co Co-doped Barium strontium titanate ceramics

In this paper, the ambient temperature multiferroic effect resulting from the incorporation of transition metal ions (Fe3+ and Co2+) in lead-free BST [ Ba0.7Sr0.3(Fex/2Cox/2)Ti1−xO3;x=0,0.01,0.03,0.05,0.07 ] ceramics synthesized via the solid-state reaction (SSR) procedure has been thoroughly analyzed. The investigation consistently scrutinized the effects of augmenting transition metal co-doping on the structural, ferroelectric, dielectric, magnetic, and magnetodielectric characteristics. The x-ray diffraction (XRD) patterns for all ceramic compositions demonstrated the formation of a monophasic (P4mm) crystalline structure. The Raman analysis evidenced the presence of various modes, which are associated with the occurrence of the single-phase and provide strong corroboration for the x-ray diffraction observations. Scanning electron micrographs reveals that the inclusion of transition metal ions results in the diminution of grain size. The frequency-dependent dielectric characteristics were represented over the frequency range of 1 kHz to 1 MHz. The P-E hysteresis curves demonstrate a consistent reduction in the values of Ps and Pr, whereas, the M-H curve reveals the enhancement in magnetic properties with increased doping. The magnetodielectric analysis confirmed the interplay between the ferroelectric and ferromagnetic ordering. The BST-1CF sample exhibited the highest MC % value of 5.30% along with the magnetoelectric coupling coefficient ‘γ’ of −6.01×10−1(memu/g)−2, making it a favorable entrant for the advancement of innovative non-volatile multiferroic memory gadgets.

Static and dynamic magnetic behavior of YBCO/Co/IrMn heterostructures

The effect of the YBCO superconducting (SC) state on the magnetic properties of as-grown YBCO/Co/IrMn heterostructures has been systematically studied using magnetometry and ferromagnetic resonance. The obtained data showed that the superconductivity of the YBCO substrate strongly affects the ferromagnetic properties of the deposited Co layer deeper (up to 50 nm) than the coherence length of the YBCO (≃4nm) by an exchange interaction between the Co magnetic moments and the superconducting pairs at the YBCO/Co interface. The interfacial exchange interaction, switched on while the YBCO enters the SC state, pins Co spins and yields an enhancement of the Co magnetic properties.

Influence of annealing on enhancing soft magnetic properties in laser powder bed fusion processed Hiperco (Fe-49Co-2V)

Annealing of laser powder bed fusion (LPBF) processed Fe-49Co-2 V (Hiperco) samples at 865 °C for 4 h leads to a substantial improvement in its soft magnetic properties. While the as built LPBF samples exhibited relatively higher coercivities (Hc) ranging from 25.8 – 26.5 Oe, the annealed LPBF samples showed significantly lower coercivities (Hc) of 6.9 – 10.8 Oe. These lower Hc values can not only be attributed to the 15–20 times larger grain sizes, but also the higher degree of B2 ordering in the annealed condition. The enhanced degree of B2 ordering also increases the saturation magnetization (Ms), from 213 to 228 emu/g, in samples processed with a laser fluence (energy/density) of 3.4 J/mm2. These results reveal the underlying mechanisms leading to an enhancement of soft magnetic properties in LPBF processed Hiperco via annealing-induced microstructural control.

Surface magnetic flux density optimization considering effect of aligned magnetic field molding conditions of ring-shaped multi-pole anisotropic ferrite permanent magnet for DC motors

The ring-shaped anisotropic ferrite magnet with multiple poles boasts significant benefits for brushless DC motors (BDCMs). However, the prevalent production method involves dry magnetic field molding, making it challenging to enhance the magnetic properties. Herein, ferrite powder made from iron oxide, a by-product of the steel industry, is used as the starting material of magnets, and the differences between dry and wet molding approaches on the surface magnetic flux density of a ring-shaped multi-pole anisotropic ferrite magnet are first investigated. ANSYS MAXWELL conducted an initial simulation to achieve the design specifications of the wet molding mold. Following this, the mold was prepared for the fabrication of ring magnets. Compared to magnets prepared via dry molding, those produced through wet molding exhibit a peak surface magnetic flux density of approximately 15.9% higher, demonstrating significant potential for industrial applications and substantial enhancement of the key magnetic properties of wet molded ferrite ring magnets. To achieve increased surface flux density of ring magnets, it is common practice to utilize magnetic powders with greater magnetic properties when molding the magnets. However, this requires a costly mold redesign. In this study, higher surface magnetic flux densities can be achieved for ring magnets by simply adjusting the shape, size and magnetization direction of NdFeB permanent magnets that provide a constant aligned magnetic field in the mold without requiring any alterations to the existing mold's dimensions. The findings of this study could improve the effectiveness of existing motor designs. The usage of ring-shaped multi-pole anisotropic ferrite magnets is anticipated to witness a surge in the coming years, driven by the growth of energy-efficient motors in diverse sectors.

Sulfate-functionalized ternary metal oxide/Polypyrrole nanocomposites: Synergistic enhancement in Photocatalytic, Corrosion inhibition, Magnetic, and Electrical properties

The effect of functionalization of conducting polymer/metal nanocomposites with sulfate functional groups on their physical, chemical, mechanical, optical, and electrical properties was investigated. Vanadium, Manganese, and Zinc oxide nanoparticles were prepared by the modified Sol-gel method. Conducting polymer, Polypyrrole was synthesized by the chemical oxidation method. Polypyrrole + ternary metal oxide nanocomposites were synthesized by in situ technique. The characterization of functionalized nanocomposites was carried by Raman spectroscopy, FTIR, UV–visible, magnetic, SEM, and XRD techniques. The photocatalytic, anticorrosive, magnetic, optical, and electrical properties of functionalized nanocomposites were investigated. The functionalized nanocomposites show 85 % corrosion inhibition efficiency. The functionalized nanocomposites degrade 87 % of the methyl blue dye in 120 min under UV light. The magnetic study shows the paramagnetic character of functionalized nanocomposites. The optical band gap of functionalized nanocomposites decreases to 0.5 eV, showing a high order of conductivity. The sulfate-functionalized ternary metal oxide/polypyrrole nanocomposites show synergistic enhancement in their photocatalytic, electrical, magnetic, and anticorrosive properties.

Effect of surfactant-assisted low-temperature annealing on the refinement of particle size and enhancement of magnetic properties of SrFe12O19 ferrite

The fabrication of SrFe12O19 ferrite powders with good magnetic properties is a key process in the industrial production of permanent magnets. Remanence and coercivity of the powders was seriously decreased due to the generation of surface lattice defects produced during the crushing of pre-sintered ferrite powders. And the traditionally applied high-temperature annealing above 800 °C can only partially restore the magnetic properties. In this work, the effects of types, adding mode and contents of surfactant (hexadecyl trimethyl ammonium bromide, triethanolamine) on the magnetic properties of crushed powders of the pre-sintered SrFe12O19 ferrite under a low-temperature annealing of 400 °C process were systematically explored. The results showed that surfactants are beneficial to restore or even enhance the magnetic properties of the crushed powders compared with the pre-sintered ferrite due to the refinement of the particles and repairing the surface defects. The surfactant-assisted low-temperature annealing process proposed in this work will promote the commercial production of high performance ferrite powders and ferrite magnets, which can also effectively reduce the production energy consumption.

Controlling grain growth to achieve improved magnetic properties of NdCeFeB magnets via grain boundary diffusion

The abnormal growth of grains near the surface of NdCeFeB magnets reduces the number of grain boundaries, and meanwhile, the formation of REFe2 phase also hinders the diffusion of rare earth elements, both of which limit the enhancement of magnetic properties. This poses a certain challenge for the preparation of high Ce content NdCeFeB magnets. In this work, it is found that the TbPrNdAl diffusion source can suppress the mutual diffusion between Ce in the main phase and rare earth elements in the diffusion source, thereby restraining the abnormal growth of grains and inhibiting the formation of REFe2 phase. Eventually, a more uniform core-shell structure and thin and continuous RE-rich phase are formed. The coercivity of 1389 kA/m and magnetic energy product of 289 kJ/m3 can be obtained without reducing the remanence, which are 612 kA/m and 30 kJ/m3 higher than those of the initial magnet, respectively. This diffusion source can greatly promote the development of NdCeFeB magnets with high Ce content.

Iron Oxide Nanoparticle-Assisted Delamination of Ti3C2Tx MXenes: A New Approach to Produce Magnetic MXene-Based Composites.

Ti3C2Tx MXene is one of the most comprehensively studied 2D materials in terms of its adsorptive, transport, and catalytic properties, cytotoxic performance, etc. Still, conventional MXene synthesis approaches provide low single-flake MXene yield and frequently uncontrollable properties, demanding further post-processing. The MXene family also lacks magnetism, which is helpful for producing effective nanoadsorbents as their magnetic decantation is the cheapest and most convenient way to remove the spent adsorbent from water. Composite materials consisting of magnetic nanoparticles grown on top of MXene flakes are commonly used to provide magnetic properties to the resulting nanocomposite. In this paper, we study the possibility to delaminate multilayer Ti3C2Tx MXene sheets directly by growing iron oxide magnetic nanoparticles inside their interlayer spacing. We find out that, with a mass fraction of particles comparable or exceeding that of MXenes, their growth is accompanied by an effective enhancement of single-layer MXene yield and suitable magnetic properties of the resulting composite. The developed approach can be further used for simplifying synthesis protocols to obtain magnetic MXene-based nanoadsorbents with tunable properties.

Utilizing ultrapure magnetite concentrate for environmentally friendly and low-cost synthesis of high-performance strontium ferrite

The presence of Al and Si impurities from ultrapure magnetite concentrate (UMC) entering the lattice during the preparation of M-type strontium ferrite (SrM) has been a significant issue limiting the enhancement of magnetic properties in UMC- prepared SrM. In this article, the impact of CaCO3 on the phase formation mechanism of synthesizing SrM using UMC is investigated. It is found that the formation of intermediate SrFeO3−x phase and SrFe12O19 phase shifts to the lower temperatures upon CaCO3 addition. Lower calcination temperatures can inhibit excessive grain growth, thereby improving coercivity. At a calcination temperature of 1050 °C with the addition of 0.6 wt% CaCO3, the highest coercivity of 4672.29 Oe was achieved. Lattice parameters, magnetic properties, and micro-area composition analysis demonstrate that the addition of CaCO3 reacts with Al impurities, preventing the incorporation of Al ions into the SrM lattice and promoting an increase in saturation magnetization. The highest saturation magnetization of 71.45 emu/g was obtained at the calcination temperature of 1200 °C. It has reached the level of magnetic properties of SrM prepared from Fe2O3. CaCO3, being low-cost and environmentally friendly, can serves as an effective additive for improving the magnetic properties of UMC-prepared SrM without compromising its cost-effective and eco-friendly advantages.

Magnetic properties enhancement of multi-element-doped SmCo7 nanocrystalline alloys

TbCu7-type SmCo7-based permanent magnets possess great potential for applications in high-temperature service because of their large magnetocrystalline anisotropy and low temperature coefficient of coercivity. However, the application of SmCo7-based alloys is seriously limited by the trade-off between the TbCu7-type phase stability and the intrinsic magnetic properties, as well as the balance between the saturation magnetization and the coercivity. In this study, a series of SmCo7-based nanocrystalline alloys doped by Mn, Cu, and Fe elements were prepared. The TbCu7-type phase was well stabilized by nanostructuring and appropriate doping. Tailoring the element doping enhanced the coercivity by 50 % and achieved a balance between the saturation magnetization and the coercivity of the SmCo7-based nanocrystalline alloys. The mechanisms of the magnetic properties enhancement were disclosed based on the characterization of microstructures and magnetic structures. It is proposed that a high proportion of the TbCu7-type SmCo7 main phase is critical to achieve excellent magnetic properties. This study provides both the method and rules for the development of multi-component Sm-Co-based alloys with high integrated magnetic properties.

Enhancement of electronic and magnetic properties in Cr2O3 monolayer honeycomb-kagome by hydrogenation and oxygenation

This study investigates the structural, electronic, and magnetic properties of pristine, hydrogenated, and oxygenated Cr2O3 monolayer honeycomb-kagome (HK) surface using first-principles calculations based on density functional theory (DFT). Molecular dynamics and phonon dispersion calculations demonstrate the thermal and dynamic stability of these systems, implying their feasibility for laboratory synthesis. The results revealed that the adsorption of hydrogen and oxygen atoms on the Cr2O3 monolayer surface exhibited negative adsorption energies, indicating that these structures are energetically favorable. Specifically, the adsorption of oxygen atoms transforms the initial half-metallic nature of the monolayer into semiconducting behavior. Moreover, the introduction of hydrogen and oxygen atoms considerably enhances the Curie temperature of the surface. These findings offer a practical approach for enhancing the electronic and magnetic properties of Cr2O3 monolayer HK surface, thereby facilitating their prospective application in spintronics.

Co-precipitation method followed by ultrafast sonochemical synthesis of aluminium doped M type BaFe11.4-xAlxCo0.6O19 hexaferrites for various applications

The co-precipitation method followed by Sonochemical process was used to synthesize M-type BaFe11.4-xAlxCo0.6O19 hexaferrites (x = 0.0, 0.4, 0.8, 1.2, and 1.6) with Al3+ substitutions. XRD, FTIR, UV–vis spectroscopy, VSM, SEM and LCR meter are used for the characterizations of the synthesized materials. The optical properties, magnetic properties, structural, morphological, and dielectric properties had been systematically investigated. XRD data and cell refinement study confirmed the hexagonal crystal structure of the synthesized materials that belong to space-group of P63/MMC-(No 194). The values of lattice parameters ‘a’ and ‘c’ have been reduced from their original value 5.9145 Åto 5.8446 Åand 23.239 Åto 23.1684 Åcorrespondingly with doping content. The values of ratio c/a are found within 3.9292 to 3.9641 range, which can be regarded as optimal values for M-type hexaferrites structure as mentioned in previous studies. The crystallite size-(D) and volume-(V) decreases with doping concentration. The band gap of the synthesized materials had shown decreasing trend with doping content. The values of dissipation factor, dielectric loss ε'', and dielectric constant ε', are higher at lower frequency but get smaller as frequency increases. The dissipation factor, dielectric loss ε'', and dielectric constant ε', reduced as the concentration of aluminium is increased. From the analysis of M−H loops it has been concluded that saturation magnetization and remnant magnetization is decreasing with aluminium content, while coercivity is increasing. The anisotropy parameter (B) and anisotropy field (Ha) had shown increasing trend with aluminium concentration. FTIR analysis showed the development of barium hexaferrites in two main absorption-bands, the enormous frequency-band and the low frequency-band. The position of these bands were moved towards a lower frequency range with increasing Al substitution level. The reduction in band gap as well as the enhancement in magnetic and dielectric properties of barium M type hexa-ferrites as a result of aluminium doping making them suitable for various applications, including magnetic storage media, magnetic sensors, microwave devices, electromagnetic wave absorbers and permanent magnets etc.

Domain structure ordering and magnetic property enhancement of containerlessly processed quaternary Fe-Mo-Ni-Cr alloy

Quaternary Fe-20 %Mo-12 %Ni-6 %Cr alloy with various composite magnetic structures was fabricated through electromagnetic levitation (EML) coupled with multi-mode quenching techniques. The magnetic domain distributions were characterized and related to the macro/micro-magnetic properties of this containerlessly processed alloy. Under EML condition, nano-scale lamellar (αFe) + Fe2Mo eutectoid structures with completely disordered magnetic domains were formed at small undercoolings. But the eutectoid morphology became anomalous and a ferromagnetic (αFe) single-phase zone with clear stripe domains appeared as undercooling increased, resulting in the obvious improvement of saturation magnetization, coercivity and residual magnetization. The (αFe) + Fe2Mo eutectoid structures were entirely suppressed by multiple quenching processes to secure (αFe) single-phase microstructures with ordered domain distributions including the stripe domains with grain boundary contrast, the maze domains with developed branches and their coexistent mixtures. These magnetic structures displayed much higher saturation magnetization, much lower coercivity and almost unchanged residual magnetization as compared with the highly undercooled alloy at EML state, indicating that the soft magnetic property of this alloy was significantly enhanced after rapid quenching. Moreover, the spin distributions and atomic magnetic moments of two constituent phases were analyzed by first-principle calculations, which were in good accordance with the experimental results.