Pub Date : 2024-10-19DOI: 10.1016/j.jmmm.2024.172602
Mingming Liu, Wei Quan, Yingzhengsheng Huang, Qiang Zheng, Juan Du
In this paper, MM-Fe-B ribbons with different MM contents were prepared by melt spun technique at a fixed copper roll speed of 25 m/s. The maximum magnetic energy product of the MM15Fe78B7 ribbon is 9.22 MGOe and the coercivity is 6005 Oe. With the increase of MM contents, the coercivity of the magnet was increased, and the highest coercivity reached 9352 Oe in MM18Fe75B7. In addition, the microstructure and magnetic properties of Cu-doped MM15Fe78-xB7Cux (x = 0, 0.4, 0.6, 1 at.%) ribbons were systematically investigated. The results show that the introduction of Cu can suppress the formation of α-Fe soft magnetic phase in the melt spun ribbons. When the Cu content is 0.4 at.%, the grain size decreased from 61 nm to 44 nm, and the coercivity was improved from 6005 Oe to 8527 Oe, which is an increment of about 42 %, whereas the remanence and the magnetic energy product can remain basically unchanged. The addition of Cu element can not only refine the grain size, but also facilitate the enhancement of the homogeneity of the microstructure of the ribbons.
{"title":"Effect of Cu-doping on the microstructure and magnetic properties of low-cost MM-Fe-B melt spun ribbons","authors":"Mingming Liu, Wei Quan, Yingzhengsheng Huang, Qiang Zheng, Juan Du","doi":"10.1016/j.jmmm.2024.172602","DOIUrl":"10.1016/j.jmmm.2024.172602","url":null,"abstract":"<div><div>In this paper, MM-Fe-B ribbons with different MM contents were prepared by melt spun technique at a fixed copper roll speed of 25 m/s. The maximum magnetic energy product of the MM<sub>15</sub>Fe<sub>78</sub>B<sub>7</sub> ribbon is 9.22 MGOe and the coercivity is 6005 Oe. With the increase of MM contents, the coercivity of the magnet was increased, and the highest coercivity reached 9352 Oe in MM<sub>18</sub>Fe<sub>75</sub>B<sub>7</sub>. In addition, the microstructure and magnetic properties of Cu-doped MM<sub>15</sub>Fe<sub>78-x</sub>B<sub>7</sub>Cu<sub>x</sub> (x = 0, 0.4, 0.6, 1 at.%) ribbons were systematically investigated. The results show that the introduction of Cu can suppress the formation of α-Fe soft magnetic phase in the melt spun ribbons. When the Cu content is 0.4 at.%, the grain size decreased from 61 nm to 44 nm, and the coercivity was improved from 6005 Oe to 8527 Oe, which is an increment of about 42 %, whereas the remanence and the magnetic energy product can remain basically unchanged. The addition of Cu element can not only refine the grain size, but also facilitate the enhancement of the homogeneity of the microstructure of the ribbons.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172602"},"PeriodicalIF":2.5,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537482","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wastewater from the electroless industry represents a potential danger to the environment and health, mainly due to its heavy metal content. In this study, nickel nanoparticles were synthesized through chemical reduction precipitation by using an electroless nickel plating waste and hydrazine sulfate as reducing agent. The aim of the present work is twofold. First we want to extract the metal from the aqueous medium, minimizing its content to levels allowed by environmental regulations. Second, we aim to valorize the residue by recovering the precipitated nickel to be applied as a solid phase in a magnetic fluid (MF). It is found that the present synthesis method using N2H4 as reducing agent, allowed us to minimize the Ni concentration in the aqueous waste in 97.49 %. The properties of the recovered Ni precipitate is compared with the Ni nanoparticles (NPs) obtained from a solution prepared with analytical grade nickel sulfate. The synthesized materials from both the waste (Ni-R) and analytical reagent (Ni-A) were characterized by comparing their chemical, physical, and morphological properties. In both cases, the Ni-R and Ni-A precipitates, spherical Ni NPs of 8–10 nm crystallite sizes are obtained, agglomerated in a bimodal size distribution centered at 174.6 and 383.4 nm, and a monomodal size distribution centered at 63.6 nm, respectively. Both Ni precipitated samples are ferromagnetic, but the Ni-R sample has a higher magnetic saturation of 40 emu/g compared to 8 emu/g of the Ni-A sample. The difference in the rheological behavior of both precipitates could be attributed to the presence of surface oxidation having a relatively less contribution in the case of the Ni-R particles due to the higher average size of the particles. The Fe content, probably coming from the nickel-plated parts in spent baths, is slightly higher in the Ni-R sample. Thus, the present work shows that it is possible to valorize an industrial Ni-based residue, by obtaining Ni precipitates that in magnetic fluids give even better results than those expected under more rigorous experimental conditions, i.e., in cases where the quality of the chemical precursors is usually a determining factor.
{"title":"Comparative study of Ni nanoparticles synthetized using electroless Ni plating waste and an analytical Ni reagent. Characterization and possible application in magnetic fluids","authors":"Susana Martinez Stagnaro , César Mesquida , Roberto Zysler , Franco Stábile , Roxana Alvian Yañez , Analía Soldati , Susana Ramos","doi":"10.1016/j.jmmm.2024.172594","DOIUrl":"10.1016/j.jmmm.2024.172594","url":null,"abstract":"<div><div>Wastewater from the electroless industry represents a potential danger to the environment and health, mainly due to its heavy metal content. In this study, nickel nanoparticles were synthesized through chemical reduction precipitation by using an electroless nickel plating waste and hydrazine sulfate as reducing agent. The aim of the present work is twofold. First we want to extract the metal from the aqueous medium, minimizing its content to levels allowed by environmental regulations. Second, we aim to valorize the residue by recovering the precipitated nickel to be applied as a solid phase in a magnetic fluid (MF). It is found that the present synthesis method using N<sub>2</sub>H<sub>4</sub> as reducing agent, allowed us to minimize the Ni concentration in the aqueous waste in 97.49 %. The properties of the recovered Ni precipitate is compared with the Ni nanoparticles (NPs) obtained from a solution prepared with analytical grade nickel sulfate. The synthesized materials from both the waste (Ni-R) and analytical reagent (Ni-A) were characterized by comparing their chemical, physical, and morphological properties. In both cases, the Ni-R and Ni-A precipitates, spherical Ni NPs of 8–10 nm crystallite sizes are obtained, agglomerated in a bimodal size distribution centered at 174.6 and 383.4 nm, and a monomodal size distribution centered at 63.6 nm, respectively. Both Ni precipitated samples are ferromagnetic, but the Ni-R sample has a higher magnetic saturation of 40 emu/g compared to 8 emu/g of the Ni-A sample. The difference in the rheological behavior of both precipitates could be attributed to the presence of surface oxidation having a relatively less contribution in the case of the Ni-R particles due to the higher average size of the particles. The Fe content, probably coming from the nickel-plated parts in spent baths, is slightly higher in the Ni-R sample. Thus, the present work shows that it is possible to valorize an industrial Ni-based residue, by obtaining Ni precipitates that in magnetic fluids give even better results than those expected under more rigorous experimental conditions, i.e., in cases where the quality of the chemical precursors is usually a determining factor.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172594"},"PeriodicalIF":2.5,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-18DOI: 10.1016/j.jmmm.2024.172600
Huifang Wu , Ruifeng Yan , Yankai Chen, Yukai An
In this work, the Janus 2H-CeXY monolayers are predicted as 2D intrinsic ferrovalley materials with bipolar ferromagnetic (FM) semiconductor characters, high Tc of 511–540 K, robust in-plane/perpendicular magnetic anisotropy (IMA/PMA) and spontaneous valley polarization through first-principles calculations. The d-p-d indirect exchange interaction between the Ce atom and X(Y) atoms is responsible for the observed FM ordering. Applying the biaxial strain ε from −6 % to 6 %, the Janus 2H-CeXY monolayers keep energy bandgap and large magnetic anisotropy. While a transition from PMA to IMA character is observed for the 2H-CeBrCl monolayer, which is due to the competition between Ce-p/d and Br/Cl-p orbitals. The intrinsic magnetic interaction and strong SOC effect induce a large spontaneous valley polarization of 29.1–78.7 meV for the Janus 2H-CeXY monolayers, which is also robust under various ε. Besides, the anomalous valley Hall effect (AVHE) can be observed due to the nonzero Ωz(k) induced by the broken space/time-reversal symmetry. Overall, the Janus 2H-CeXY monolayers provides a new candidate for the spintronic and valleytronic devices.
{"title":"Predictions of spin-valley properties in ferromagnetic Janus 2H-CeXY (X, Y = Cl, Br, I, X ≠ Y) monolayers: Merger of valleytronics with spintronics","authors":"Huifang Wu , Ruifeng Yan , Yankai Chen, Yukai An","doi":"10.1016/j.jmmm.2024.172600","DOIUrl":"10.1016/j.jmmm.2024.172600","url":null,"abstract":"<div><div>In this work, the Janus 2H-CeXY monolayers are predicted as 2D intrinsic ferrovalley materials with bipolar ferromagnetic (FM) semiconductor characters, high T<sub>c</sub> of 511–540 K, robust in-plane/perpendicular magnetic anisotropy (IMA/PMA) and spontaneous valley polarization through first-principles calculations. The <em>d</em>-<em>p</em>-<em>d</em> indirect exchange interaction between the Ce atom and X(Y) atoms is responsible for the observed FM ordering. Applying the biaxial strain <em>ε</em> from −6 % to 6 %, the Janus 2H-CeXY monolayers keep energy bandgap and large magnetic anisotropy. While a transition from PMA to IMA character is observed for the 2H-CeBrCl monolayer, which is due to the competition between Ce-<em>p</em>/<em>d</em> and Br/Cl-p orbitals. The intrinsic magnetic interaction and strong SOC effect induce a large spontaneous valley polarization of 29.1–78.7 meV for the Janus 2H-CeXY monolayers, which is also robust under various <em>ε</em>. Besides, the anomalous valley Hall effect (AVHE) can be observed due to the nonzero <em>Ω<sub>z</sub></em>(<em>k</em>) induced by the broken space/time-reversal symmetry. Overall, the Janus 2H-CeXY monolayers provides a new candidate for the spintronic and valleytronic devices.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172600"},"PeriodicalIF":2.5,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535057","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-18DOI: 10.1016/j.jmmm.2024.172586
Fei Wan , Li-Hua Lu , Can Xie , You-Quan Li
We propose a novel method for sensing the gradient direction of a weak magnetic field overwhelmed by a noisy background through studying the correlated random walk of Brown particles that carry with magnetic moment. Using numerical simulation, we find that the snapshot of the distribution of Brown particles that touched the top surface of a cubic container provides useful information, i.e., the center of the distribution pattern will deflect towards the direction of magnetic gradient. We also find that the impact of magnetic noise can be effectively suppressed by the presence of correlation when the concentration of Brown particles is in the region of . Our findings may motivate novel scheme to identify the direction of magnetic gradient in the presence of strong noise, which is undoubtedly important for practical applications.
{"title":"The detection of magnetic gradient aided by correlated random walk","authors":"Fei Wan , Li-Hua Lu , Can Xie , You-Quan Li","doi":"10.1016/j.jmmm.2024.172586","DOIUrl":"10.1016/j.jmmm.2024.172586","url":null,"abstract":"<div><div>We propose a novel method for sensing the gradient direction of a weak magnetic field overwhelmed by a noisy background through studying the correlated random walk of Brown particles that carry with magnetic moment. Using numerical simulation, we find that the snapshot of the distribution of Brown particles that touched the top surface of a cubic container provides useful information, i.e., the center of the distribution pattern will deflect towards the direction of magnetic gradient. We also find that the impact of magnetic noise can be effectively suppressed by the presence of correlation when the concentration of Brown particles is in the region of <span><math><mrow><mn>0</mn><mo>.</mo><mn>2</mn><msub><mrow><mi>ρ</mi></mrow><mrow><mn>0</mn></mrow></msub><mo><</mo><mi>ρ</mi><mo><</mo><mn>0</mn><mo>.</mo><mn>7</mn><msub><mrow><mi>ρ</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></math></span>. Our findings may motivate novel scheme to identify the direction of magnetic gradient in the presence of strong noise, which is undoubtedly important for practical applications.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172586"},"PeriodicalIF":2.5,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-18DOI: 10.1016/j.jmmm.2024.172597
Anar Westerberg , Sai Ram Boggavarapu , Sandra Eriksson
Rare earth elements are associated with many challenges, and therefore, rare earth free options are being investigated as an alternative. The further improvement of the electrical machines with rare earth free permanent magnets requires an accurate and efficient finite element method (FEM) model to predict and overcome the issues related to a low magnetic flux density or partial demagnetization of permanent magnets. The main challenges of the permanent magnet model development are related to the nonlinearity of the hysteresis loop in the operating region and permanent magnet anisotropy. The model presented in this paper is a dynamic model of anisotropic nonlinear permanent magnet (PM) developed in COMSOL Multiphysics 6.2 software. The model can be used for modelling magnetic materials with a hysteresis loop. Measurement results of Alnico 8 LNGT40 nonlinear permanent magnet were used in this model. The model includes all four quadrants of hysteresis loops, recoil lines, and knee points of preferred or easy (EA) and transverse or hard (HA) magnetization directions. It allows correct modelling of not only generators but also motors and memory machines. The flowcharts of the permanent magnet modelling logic were presented for both directions. Partial demagnetization in the preferred (EA) direction and partial magnetization in the transverse (HA) direction can be observed in the simulation results after the short circuit. Partial remagnetization of the magnet in the preferred (EA) direction and partial demagnetization in the transverse (HA) can be observed after applying a current with the same amplitude but in the opposite direction. The top part of the magnet was mostly affected by the magnetic field of the stator. Simulation results differ from the previous version of the magnet model. The new version of the model has a higher accuracy and shows higher demagnetization in the preferred (EA) direction than the previous version.
{"title":"Anisotropic model of nonlinear permanent magnets in finite element method software","authors":"Anar Westerberg , Sai Ram Boggavarapu , Sandra Eriksson","doi":"10.1016/j.jmmm.2024.172597","DOIUrl":"10.1016/j.jmmm.2024.172597","url":null,"abstract":"<div><div>Rare earth elements are associated with many challenges, and therefore, rare earth free options are being investigated as an alternative. The further improvement of the electrical machines with rare earth free permanent magnets requires an accurate and efficient finite element method (FEM) model to predict and overcome the issues related to a low magnetic flux density or partial demagnetization of permanent magnets. The main challenges of the permanent magnet model development are related to the nonlinearity of the hysteresis loop in the operating region and permanent magnet anisotropy. The model presented in this paper is a dynamic model of anisotropic nonlinear permanent magnet (PM) developed in COMSOL Multiphysics 6.2 software. The model can be used for modelling magnetic materials with a hysteresis loop. Measurement results of Alnico 8 LNGT40 nonlinear permanent magnet were used in this model. The model includes all four quadrants of hysteresis loops, recoil lines, and knee points of preferred or easy (EA) and transverse or hard (HA) magnetization directions. It allows correct modelling of not only generators but also motors and memory machines. The flowcharts of the permanent magnet modelling logic were presented for both directions. Partial demagnetization in the preferred (EA) direction and partial magnetization in the transverse (HA) direction can be observed in the simulation results after the short circuit. Partial remagnetization of the magnet in the preferred (EA) direction and partial demagnetization in the transverse (HA) can be observed after applying a current with the same amplitude but in the opposite direction. The top part of the magnet was mostly affected by the magnetic field of the stator. Simulation results differ from the previous version of the magnet model. The new version of the model has a higher accuracy and shows higher demagnetization in the preferred (EA) direction than the previous version.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172597"},"PeriodicalIF":2.5,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-18DOI: 10.1016/j.jmmm.2024.172588
Zhuang Deng , Yu Wang , Shuo Zhang , Jingyi Wu , Shuning Wei , Zhen Jiao
Iron-based magnetic nanoparticles have gained significant attention in biomedicine. However, the magnetic properties of iron-based nanoparticles prepared through coprecipitation methods often do not meet application requirements. This study aims to enhance the performance of iron-based magnetic nanoparticles by synthesizing them via the coprecipitation method and doping them with Mn2+, Zn2+, and Co2+ ions in various ratios. Among these, Zn-doped nanoparticles with a 0.6 ratio (ZION-6) exhibits the highest saturation magnetization intensity of 98 emu/g sample and the highest r2 values of 165.2 mM−1·s−1, making them an effective T2 MRI contrast agent. Our investigation into the coprecipitation process revealed a formation mechanism for ion-doped magnetic iron-based nanoparticles. This mechanism involves the formation of an intermediate phase, α-FeOOH, followed by phase transformation, ion doping, and the aggregation of small particles to yield the final magnetic nanoparticles. This research could pave the way for developing magnetic nanoparticles with improved properties for biomedical applications.
{"title":"Ion-Doped Iron-Based nanoparticles with enhanced magnetic properties: Synthesis and formation mechanism via coprecipitation","authors":"Zhuang Deng , Yu Wang , Shuo Zhang , Jingyi Wu , Shuning Wei , Zhen Jiao","doi":"10.1016/j.jmmm.2024.172588","DOIUrl":"10.1016/j.jmmm.2024.172588","url":null,"abstract":"<div><div>Iron-based magnetic nanoparticles have gained significant attention in biomedicine. However, the magnetic properties of iron-based nanoparticles prepared through coprecipitation methods often do not meet application requirements. This study aims to enhance the performance of iron-based magnetic nanoparticles by synthesizing them via the coprecipitation method and doping them with Mn<sup>2+</sup>, Zn<sup>2+</sup>, and Co<sup>2+</sup> ions in various ratios. Among these, Zn-doped nanoparticles with a 0.6 ratio (ZION-6) exhibits the highest saturation magnetization intensity of 98 emu/g sample and the highest r<sub>2</sub> values of 165.2 mM<sup>−1</sup>·s<sup>−1</sup>, making them an effective T<sub>2</sub> MRI contrast agent. Our investigation into the coprecipitation process revealed a formation mechanism for ion-doped magnetic iron-based nanoparticles. This mechanism involves the formation of an intermediate phase, α-FeOOH, followed by phase transformation, ion doping, and the aggregation of small particles to yield the final magnetic nanoparticles. This research could pave the way for developing magnetic nanoparticles with improved properties for biomedical applications.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172588"},"PeriodicalIF":2.5,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The strain dependence of the pulse voltage induced in a pickup coil originating from the domain wall motion in an amorphous FeSiBNb thin film was investigated. No significant change in the peak pulse voltage was observed when tensile strain was applied to the thin film, whereas the peak pulse voltage changed steeply when compressive strain was applied. In addition, strain susceptibility could be controlled via appropriate annealing. Evaluation of the strain gauge comprising the amorphous FeSiBNb thin film, a pickup coil, an electrical circuit (which converts the pulse voltage into direct current voltage), and a Helmholtz coil revealed that strain gauge has a notably high gauge factor of approximately 37,500.
{"title":"Strain detection based on magnetic domain wall motion in amorphous FeSiBNb thin film","authors":"Kouya Maeno , Yuji Fujiwara , Mutsuko Jimbo , Daiki Oshima , Takeshi Kato","doi":"10.1016/j.jmmm.2024.172604","DOIUrl":"10.1016/j.jmmm.2024.172604","url":null,"abstract":"<div><div>The strain dependence of the pulse voltage induced in a pickup coil originating from the domain wall motion in an amorphous FeSiBNb thin film was investigated. No significant change in the peak pulse voltage was observed when tensile strain was applied to the thin film, whereas the peak pulse voltage changed steeply when compressive strain was applied. In addition, strain susceptibility could be controlled via appropriate annealing. Evaluation of the strain gauge comprising the amorphous FeSiBNb thin film, a pickup coil, an electrical circuit (which converts the pulse voltage into direct current voltage), and a Helmholtz coil revealed that strain gauge has a notably high gauge factor of approximately 37,500.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172604"},"PeriodicalIF":2.5,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-16DOI: 10.1016/j.jmmm.2024.172577
Paul Okpozo , James Njuguna , Sheikh Islam , Kindness Uyanga , Ketan Pancholi
Magnetic self-assembly of nanoparticles is a well-known technique for creating thin-film array-patterned functional microstructures. However, an uncontrollable hierarchical assembly formation of magnetically stimulated particles has hindered the desired formation of free-standing two-dimensional (2D) array patterns in thin-film layers. In this study, we proposed a fluidic shearing effect from spin coating to reduce the magnetically stimulated particles’ disarrayed and complex chain formations. This would thus promote linear array formations, even as the film becomes thinner. A series of tests were conducted on a gold-pickering ferrofluid emulsion (GPFE) dispersed in 15.2 mPas aqueous polyvinyl alcohol (PVAh) under varying spin speeds and magnetic setups such as single (SI), compound (CC), and concentric (CR). These setups were chosen to observe the influence of magnetic field strength and distribution on the generated pattern profile from microscopic binary images of the resulting thin films. The aim was to quantify the formed chain thickness (ChT), chain gaps (ChG), and chain lengths (ChL) to capture the morphology and geometrical features of the formed patterns. Our results showed that the quantified values of these profiles and their dimensionless relationships were significantly influenced by the ratio between the applied magnetic packing energy and the centrifugally controlled fluidic energy, QPD. This investigation showed that ChT/ChG for a corresponding QPD value is 98.6% the same for all configurations, and CR was the best setup going forward, as it yielded the lowest array quality defectivity of 14%. Therefore, we assert that this fabrication method offers flexibility, cost-effectiveness, and expandability in generating linear array patterns that contain graduating variability in grating order dimensions within a single cast that can serve efficiently as a substrate for biomolecules under enhanced Raman and Infrared spectroscopies.
{"title":"Fabrication with magnetic-spin coating: Influence of magnetic-inertia energy ratio on gold-pickering ferrofluid droplet assembly morphology","authors":"Paul Okpozo , James Njuguna , Sheikh Islam , Kindness Uyanga , Ketan Pancholi","doi":"10.1016/j.jmmm.2024.172577","DOIUrl":"10.1016/j.jmmm.2024.172577","url":null,"abstract":"<div><div>Magnetic self-assembly of nanoparticles is a well-known technique for creating thin-film array-patterned functional microstructures. However, an uncontrollable hierarchical assembly formation of magnetically stimulated particles has hindered the desired formation of free-standing two-dimensional (2D) array patterns in thin-film layers. In this study, we proposed a fluidic shearing effect from spin coating to reduce the magnetically stimulated particles’ disarrayed and complex chain formations. This would thus promote linear array formations, even as the film becomes thinner. A series of tests were conducted on a gold-pickering ferrofluid emulsion (GPFE) dispersed in 15.2 mPas aqueous polyvinyl alcohol (PVAh) under varying spin speeds and magnetic setups such as single (SI), compound (CC), and concentric (CR). These setups were chosen to observe the influence of magnetic field strength and distribution on the generated pattern profile from microscopic binary images of the resulting thin films. The aim was to quantify the formed chain thickness (ChT), chain gaps (ChG), and chain lengths (ChL) to capture the morphology and geometrical features of the formed patterns. Our results showed that the quantified values of these profiles and their dimensionless relationships were significantly influenced by the ratio between the applied magnetic packing energy and the centrifugally controlled fluidic energy, Q<sub>PD</sub>. This investigation showed that ChT/ChG for a corresponding Q<sub>PD</sub> value is 98.6% the same for all configurations, and CR was the best setup going forward, as it yielded the lowest array quality defectivity of 14%. Therefore, we assert that this fabrication method offers flexibility, cost-effectiveness, and expandability in generating linear array patterns that contain graduating variability in grating order dimensions within a single cast that can serve efficiently as a substrate for biomolecules under enhanced Raman and Infrared spectroscopies.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172577"},"PeriodicalIF":2.5,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-15DOI: 10.1016/j.jmmm.2024.172599
Wang Yao , Yanru Li , Meiyin Yang , Feiyan Hou , Tao Li , Tai Min
To minimize the screening effect of a metallic ferromagnetic film and improve the effectiveness of electric field modulation, high-quality ultrathin magnetic film is one of the critical prerequisites. Here ultrathin magnetic films and synthetic antiferromagnetics (SAFs) are deposited on SiO2 substrates at room temperature using the magnetron sputtering. Atomic force microscopy is used to characterize the roughness of MgO, Nb, Ru, W, and CoFeB films, revealing their atomic-level flatness, with root mean square roughness values below 0.3 nm, which are crucial in the subsequent preparation of ultrathin SAF to achieve high-quality interfaces. The results from the magneto-optical Kerr microscopy suggest that when MgO is 1.48 nm, ultrathin 0.6 nm CoFeB exhibits stable room-temperature perpendicular magnetic anisotropy (PMA) and there is a correlation between room-temperature ferromagnetism and MgO thickness. For SAFs, ultrathin 0.6 nm CoFeB-based SAF exhibits room-temperature antiferromagnetism via the Ruderman-Kittel-Kasuya-Yosida interaction mechanism. The exchange coupling field demonstrates that the transition between ferromagnetic coupling and antiferromagnetic coupling can be regulated by adjusting both the thickness of the non-magnetic spacer layer and the CoFeB layer. This work lays the ground for the potential applications of high-density storage and efficient electric field modulation of ferromagnetic multilayers for improving energy efficiency.
要最大限度地减少金属铁磁薄膜的屏蔽效应并提高电场调制的有效性，高质量的超薄磁性薄膜是关键的先决条件之一。本文利用磁控溅射技术，在室温下将超薄磁性薄膜和合成反铁磁体（SAF）沉积在二氧化硅基底上。原子力显微镜用于表征氧化镁、铌、钌、钨和 CoFeB 薄膜的粗糙度，揭示了它们原子级的平整度，均方根粗糙度值低于 0.3 nm，这对于后续制备超薄 SAF 以实现高质量界面至关重要。磁光克尔显微镜的结果表明，当氧化镁为 1.48 nm 时，0.6 nm 的超薄 CoFeB 表现出稳定的室温垂直磁各向异性（PMA），室温铁磁性与氧化镁厚度之间存在相关性。就 SAF 而言，基于 CoFeB 的超薄 0.6 纳米 SAF 通过 Ruderman-Kittel-Kasuya-Yosida 相互作用机制表现出室温反铁磁性。交换耦合场表明，铁磁耦合和反铁磁耦合之间的过渡可以通过调整非磁性间隔层和 CoFeB 层的厚度来调节。这项研究为铁磁多层膜的高密度存储和高效电场调制的潜在应用奠定了基础，从而提高了能源效率。
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Pub Date : 2024-10-15DOI: 10.1016/j.jmmm.2024.172595
Haihui Wu , Zhanjia Wang , Weiqiang Liu , Min Fan , Yuqing Li , Ming Ji , Ruihua Du , Dongtao Zhang , Guanzhi Xiang , Ming Yue , Xiaofei Yi , Youhao Liu , Shanshun Zha
Screen printing technology (SPT) was applied to conduct grain boundary diffusion sintered Nd-Fe-B magnets using TbH3 and TbF3 nanopowders as diffusion sources. TbH3 grain boundary diffusion (HGBD) coating had better adhesion to the magnet surface than TbF3 grain boundary diffusion (FGBD) coating. When the weight gain ratio was 1.0 wt%, the HGBD magnet achieved a coercivity increment of 11.07 kOe under non-pressurized heat treatment, while effectively controlling the magnet’s residual C and O elements. However, pressure heat treatment was necessary for the FGBD magnet to improve the coercivity due to the poor adhesion between the coating and the magnet surface, resulting in more residual C and O elements inside the magnet. Moreover, the coercivity of the FGBD magnet only increased by 7.96 kOe. Compared to the FGBD magnet, Tb diffused deeper into the HGBD magnet and formed more (Nd, Tb)2Fe14B-Nd2Fe14B core–shell structures. The formation of core–shell structures greatly enhanced the nucleation field of the reverse domain, thereby increasing the coercivity. Hence, the HGBD magnet had a higher coercivity increment. In addition, the HGBD magnet possessed better coercivity temperature stability than the original and FGBD magnets. Using TbH3 nanopowders as a diffusion source for SPT can achieve higher magnetic properties and simplified processes without pressure.
采用丝网印刷技术（SPT），以 TbH3 和 TbF3 纳米粉体为扩散源，进行晶界扩散烧结 Nd-Fe-B 磁体。与 TbF3 晶界扩散（FGBD）涂层相比，TbH3 晶界扩散（HGBD）涂层与磁体表面的附着力更好。当增重比为 1.0 wt%时，HGBD 磁体在非加压热处理条件下实现了 11.07 kOe 的矫顽力增量，同时有效控制了磁体的残余 C 和 O 元素。然而，由于涂层与磁体表面之间的附着力较差，导致磁体内部残留更多的 C 和 O 元素，因此 FGBD 磁体必须经过加压热处理才能提高矫顽力。此外，FGBD 磁体的矫顽力仅提高了 7.96 kOe。与 FGBD 磁体相比，铽元素在 HGBD 磁体中扩散得更深，形成了更多的（钕、铽）2Fe14B-Nd2Fe14B 核壳结构。核壳结构的形成大大增强了反向畴的成核场，从而提高了矫顽力。因此，HGBD 磁体具有更高的矫顽力。此外，与原始磁体和 FGBD 磁体相比，HGBD 磁体具有更好的矫顽力温度稳定性。使用 TbH3 纳米粉体作为 SPT 的扩散源可以获得更高的磁性能，并简化了无压工艺。
{"title":"Strategy for co-enhancement of interface adhesion and coercivity of Nd-Fe-B grain boundary diffusion magnet: TbH3 nanopowders used in screen printing","authors":"Haihui Wu , Zhanjia Wang , Weiqiang Liu , Min Fan , Yuqing Li , Ming Ji , Ruihua Du , Dongtao Zhang , Guanzhi Xiang , Ming Yue , Xiaofei Yi , Youhao Liu , Shanshun Zha","doi":"10.1016/j.jmmm.2024.172595","DOIUrl":"10.1016/j.jmmm.2024.172595","url":null,"abstract":"<div><div>Screen printing technology (SPT) was applied to conduct grain boundary diffusion sintered Nd-Fe-B magnets using TbH<sub>3</sub> and TbF<sub>3</sub> nanopowders as diffusion sources. TbH<sub>3</sub> grain boundary diffusion (HGBD) coating had better adhesion to the magnet surface than TbF<sub>3</sub> grain boundary diffusion (FGBD) coating. When the weight gain ratio was 1.0 wt%, the HGBD magnet achieved a coercivity increment of 11.07 kOe under non-pressurized heat treatment, while effectively controlling the magnet’s residual C and O elements. However, pressure heat treatment was necessary for the FGBD magnet to improve the coercivity due to the poor adhesion between the coating and the magnet surface, resulting in more residual C and O elements inside the magnet. Moreover, the coercivity of the FGBD magnet only increased by 7.96 kOe. Compared to the FGBD magnet, Tb diffused deeper into the HGBD magnet and formed more (Nd, Tb)<sub>2</sub>Fe<sub>14</sub>B-Nd<sub>2</sub>Fe<sub>14</sub>B core–shell structures. The formation of core–shell structures greatly enhanced the nucleation field of the reverse domain, thereby increasing the coercivity. Hence, the HGBD magnet had a higher coercivity increment. In addition, the HGBD magnet possessed better coercivity temperature stability than the original and FGBD magnets. Using TbH<sub>3</sub> nanopowders as a diffusion source for SPT can achieve higher magnetic properties and simplified processes without pressure.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"610 ","pages":"Article 172595"},"PeriodicalIF":2.5,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441544","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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