Pub Date : 2025-03-14DOI: 10.1109/LMAG.2025.3551243
Gabriel M. Vieira;Marcelo A. Rosa;Paulo A. P. Wendhausen;Maximiliano D. Martins
Fused deposition modeling (FDM) is an additive manufacturing technique that has become widely used in many fields of engineering and has recently proven to be suitable for producing complex, net-shaped bonded Nd–Fe–B magnets. At the same time, recycling end-of-life magnets has been an emerging concern due to their increasing presence in current technologies and the intrinsic scarcity of rare-Earth elements, such as neodymium and praseodymium. Here, we investigated the feasibility of using recycled nanocrystalline Nd–Fe–B powders, obtained from a hydrogenation–disproportionation–desorption–recombination (HDDR) process in the preparation of FDM feedstock and subsequent printing of magnetic parts. Recycled magnetic powder was mixed with polylactic acid and extruded into filaments containing increasing volume fractions of magnetic powder. It was possible to obtain filaments containing from 6.7% to 23.6% in volume (30.4 to 65.2 wt.%) of the magnetic powder, from which parts could be printed, reaching maximum coercivity (Hcj) of 707.7 ± 3.5 kA/m, maximum remanence (Br) of 84.5 ± 0.4 mT, maximum energy product (BHmax) of 1.3 kJ/m3, and average part porosity of 42 ± 8%. Coercivity loss of about 8.6% was observed in the printed parts compared to the recycled powder (750±75 kA/m). Aging experiments showed that such loss may be a combined effect of thermal and oxidation effects of the magnetic particles during the additive manufacturing processing. The present work has demonstrated the achievement of ready-to-use, high-coercivity FDM filaments, and 3-D-printed parts using recycled Nd–Fe–B HDDR powders.
{"title":"Ready-to-Use Composite Fused Deposition Modeling Filaments Produced With Polylactic Acid and Recycled Nd–Fe–B Nanocrystalline Powder for Additive Manufacturing of Bonded Magnets","authors":"Gabriel M. Vieira;Marcelo A. Rosa;Paulo A. P. Wendhausen;Maximiliano D. Martins","doi":"10.1109/LMAG.2025.3551243","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3551243","url":null,"abstract":"Fused deposition modeling (FDM) is an additive manufacturing technique that has become widely used in many fields of engineering and has recently proven to be suitable for producing complex, net-shaped bonded Nd–Fe–B magnets. At the same time, recycling end-of-life magnets has been an emerging concern due to their increasing presence in current technologies and the intrinsic scarcity of rare-Earth elements, such as neodymium and praseodymium. Here, we investigated the feasibility of using recycled nanocrystalline Nd–Fe–B powders, obtained from a hydrogenation–disproportionation–desorption–recombination (HDDR) process in the preparation of FDM feedstock and subsequent printing of magnetic parts. Recycled magnetic powder was mixed with polylactic acid and extruded into filaments containing increasing volume fractions of magnetic powder. It was possible to obtain filaments containing from 6.7% to 23.6% in volume (30.4 to 65.2 wt.%) of the magnetic powder, from which parts could be printed, reaching maximum coercivity (<italic>H</i><sub>cj</sub>) of 707.7 ± 3.5 kA/m, maximum remanence (<italic>B</i><sub>r</sub>) of 84.5 ± 0.4 mT, maximum energy product (<italic>BH</i><sub>max</sub>) of 1.3 kJ/m<sup>3</sup>, and average part porosity of 42 ± 8%. Coercivity loss of about 8.6% was observed in the printed parts compared to the recycled powder (750±75 kA/m). Aging experiments showed that such loss may be a combined effect of thermal and oxidation effects of the magnetic particles during the additive manufacturing processing. The present work has demonstrated the achievement of ready-to-use, high-coercivity FDM filaments, and 3-D-printed parts using recycled Nd–Fe–B HDDR powders.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143856196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-14DOI: 10.1109/LMAG.2025.3551266
Aakansha Aakansha;Seenipandian Ravi
This letter covers the structural and magnetic properties of lanthanum-substituted gadolinium iron garnet (GIG) (Gd3-xLaxFe5O12), where the La ion was substituted at the Gd site. X-ray diffraction analysis suggested that the synthesized samples possess cubic crystal structure with an increase in lattice constant with La substitution. The crystallite size was estimated through the Williamson–Hall plot analysis and found to increase from 50.577 for ${x}$ = 0 to 67.343 nm for ${x}$ = 0.4. The room temperature magnetization value was increasing from 0.162 to 2.536 emu/g from pure to La-substituted GIG. These materials display a ferrimagnetic to paramagnetic phase transition as high temperature rose from 565 to 573 K, which is attributed to the high superexchange interaction between Fe3+ ions. In addition to transition, temperature magnetic compensation was also observed below room temperature. The coercivity of the samples was estimated from the room temperature hysteresis curve, which shows soft ferrimagnetic behavior. The stable crystal structure, low magnetic compensation, low coercive field, and high transition temperature make these materials suitable for communication devices.
{"title":"Tuning Magnetic Behavior of Lanthanum-Substituted Gd3Fe5O12: An Experimental Study","authors":"Aakansha Aakansha;Seenipandian Ravi","doi":"10.1109/LMAG.2025.3551266","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3551266","url":null,"abstract":"This letter covers the structural and magnetic properties of lanthanum-substituted gadolinium iron garnet (GIG) (Gd<sub>3-</sub><italic><sub>x</sub></i>La<italic><sub>x</sub></i>Fe<sub>5</sub>O<sub>12</sub>), where the La ion was substituted at the Gd site. X-ray diffraction analysis suggested that the synthesized samples possess cubic crystal structure with an increase in lattice constant with La substitution. The crystallite size was estimated through the Williamson–Hall plot analysis and found to increase from 50.577 for <inline-formula><tex-math>${x}$</tex-math></inline-formula> = 0 to 67.343 nm for <inline-formula><tex-math>${x}$</tex-math></inline-formula> = 0.4. The room temperature magnetization value was increasing from 0.162 to 2.536 emu/g from pure to La-substituted GIG. These materials display a ferrimagnetic to paramagnetic phase transition as high temperature rose from 565 to 573 K, which is attributed to the high superexchange interaction between Fe<sup>3+</sup> ions. In addition to transition, temperature magnetic compensation was also observed below room temperature. The coercivity of the samples was estimated from the room temperature hysteresis curve, which shows soft ferrimagnetic behavior. The stable crystal structure, low magnetic compensation, low coercive field, and high transition temperature make these materials suitable for communication devices.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143830542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-18DOI: 10.1109/LMAG.2025.3541915
Yixiao Ding;Xuan Wang;Mark G. Allen
Quasi-static magnetic fields can be used to modulate the magnetic and electrical properties of many magnetic materials, thereby enabling the operation of various magnetic devices, such as multiferroic magnetic field sensors and ferro/ferrimagnetic magneto-static wave filters. We present a magnetic circuit designed to produce a tunable dc magnetic bias field and detail its operating principle. The magnitude of the bias field can be electrically tuned to achieve a desired magnetic field; when not being switched, the achieved field is maintained with zero static power consumption. The magnetic circuit comprises two distinct types of permanent magnets: an NdFeB magnet with relatively high coercivity and an AlNiCo V magnet with relatively low coercivity combined with a tuning coil for adjusting its magnetization. Soft magnetic yoke pieces link the permanent magnets and also define an air gap. Pulses of current through the coil will adjust the remanence of the AlNiCo magnet, thereby changing the flux and field in the air gap. A magnetic bias circuit with a compact volume of 0.27 cm3 has been constructed, providing an adjustable dc magnetic field with a tuning range of 3.7 to 288.5 mT within a 1 mm air gap.
{"title":"A Tunable Magnetic Bias Circuit With Zero Static Power Consumption","authors":"Yixiao Ding;Xuan Wang;Mark G. Allen","doi":"10.1109/LMAG.2025.3541915","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3541915","url":null,"abstract":"Quasi-static magnetic fields can be used to modulate the magnetic and electrical properties of many magnetic materials, thereby enabling the operation of various magnetic devices, such as multiferroic magnetic field sensors and ferro/ferrimagnetic magneto-static wave filters. We present a magnetic circuit designed to produce a tunable dc magnetic bias field and detail its operating principle. The magnitude of the bias field can be electrically tuned to achieve a desired magnetic field; when not being switched, the achieved field is maintained with zero static power consumption. The magnetic circuit comprises two distinct types of permanent magnets: an NdFeB magnet with relatively high coercivity and an AlNiCo V magnet with relatively low coercivity combined with a tuning coil for adjusting its magnetization. Soft magnetic yoke pieces link the permanent magnets and also define an air gap. Pulses of current through the coil will adjust the remanence of the AlNiCo magnet, thereby changing the flux and field in the air gap. A magnetic bias circuit with a compact volume of 0.27 cm<sup>3</sup> has been constructed, providing an adjustable dc magnetic field with a tuning range of 3.7 to 288.5 mT within a 1 mm air gap.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143637904","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-30DOI: 10.1109/LMAG.2025.3536936
Nicholas Homrocky;Cody Trevillian;Vasyl Tyberkevych
Nonreciprocal propagation of surface acoustic waves (SAWs) may be achieved through magneto-elastic coupling with surface spin waves (SSWs). Here, we studied theoretically SAW–SSW coupling in yttrium–iron garnet (YIG)/ gadolinium–gallium garnet (GGG) bilayers magnetized in-plane at an oblique angle to the direction of wave propagation. An expression for the coupling rate that considers actual thickness profiles of both waves has been derived. The effects of the SAW–SSW coupling are most pronounced at the crossing point of the SAW and SSW spectra, which, for typical experimental parameters, occurs at a frequency of about 2 GHz and wavelength 2 µm. Under these conditions, the coupling rate for SSWs localized near the free surface of the YIG layer weakly depends on system parameters and exceeds 25 MHz. In contrast, for the opposite direction of wave propagation, when the SSW is localized near the YIG/GGG interface, the coupling rate rapidly decreases with the increase of YIG thickness, and strong nonreciprocity of the coupling is observed for thicknesses over 0.5 µm. With the increase of YIG thickness above 2.5 µm, coupling of SAW to higher order standing spin waves becomes important, which pollutes the spectrum of hybrid magneto-elastic waves, making observation and practical use of nonreciprocal SAW–SSW coupling more difficult.
{"title":"Magneto-Elastic Coupling of Surface Spin and Surface Acoustic Waves","authors":"Nicholas Homrocky;Cody Trevillian;Vasyl Tyberkevych","doi":"10.1109/LMAG.2025.3536936","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3536936","url":null,"abstract":"Nonreciprocal propagation of surface acoustic waves (SAWs) may be achieved through magneto-elastic coupling with surface spin waves (SSWs). Here, we studied theoretically SAW–SSW coupling in yttrium–iron garnet (YIG)/ gadolinium–gallium garnet (GGG) bilayers magnetized in-plane at an oblique angle to the direction of wave propagation. An expression for the coupling rate that considers actual thickness profiles of both waves has been derived. The effects of the SAW–SSW coupling are most pronounced at the crossing point of the SAW and SSW spectra, which, for typical experimental parameters, occurs at a frequency of about 2 GHz and wavelength 2 µm. Under these conditions, the coupling rate for SSWs localized near the free surface of the YIG layer weakly depends on system parameters and exceeds 25 MHz. In contrast, for the opposite direction of wave propagation, when the SSW is localized near the YIG/GGG interface, the coupling rate rapidly decreases with the increase of YIG thickness, and strong nonreciprocity of the coupling is observed for thicknesses over 0.5 µm. With the increase of YIG thickness above 2.5 µm, coupling of SAW to higher order standing spin waves becomes important, which pollutes the spectrum of hybrid magneto-elastic waves, making observation and practical use of nonreciprocal SAW–SSW coupling more difficult.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143553310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-27DOI: 10.1109/LMAG.2025.3535310
Meng Zhao;Xianfeng Liang;Yuxi Wang;Tao Wu;Jingen Wu;Jinghong Guo;Zhongqiang Hu;Ming Liu
Thin-film magneto-electric composites based on aluminum nitride (AIN) and Sc-doped AlN exhibit great potential for applications in magneto-electric devices. In this letter, we report soft magnetism and microwave properties in FeCoSiB ferromagnetic alloys grown on AlN and AlScN thin films. According to the hysteresis loop, the coercive fields for FeCoSiB/AlN/Mo/Si and FeCoSiB/AlScN/Mo/Si are 43 and 107 Oe, respectively. The influence of interfacial state on magnetic damping is investigated by measuring the magnetic dynamic properties. Scanning electron microscope images show that AlScN film has a larger grain size and rougher surface than that of AlN. The effective magnetization and damping factors are obtained from the ferromagnetic resonance spectroscopy. The damping factor of the magneto-electric heterojunction on AlN/Mo/Si is an order of magnitude higher than that on Si, indicating the interfacial conditions of thin film stacks affect the magnetic dynamic properties. Our findings indicate that the growth quality of piezoelectric materials has a significant impact on magneto-electric films with low-loss tangents at radio-frequency (RF)/microwave frequencies. This work is of practical importance for developing future RF/microwave magneto-electric devices.
{"title":"Soft Magnetism and Microwave Properties of FeCoSiB Ferromagnetic Alloys Grown on AlN and AlScN Thin Films","authors":"Meng Zhao;Xianfeng Liang;Yuxi Wang;Tao Wu;Jingen Wu;Jinghong Guo;Zhongqiang Hu;Ming Liu","doi":"10.1109/LMAG.2025.3535310","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3535310","url":null,"abstract":"Thin-film magneto-electric composites based on aluminum nitride (AIN) and Sc-doped AlN exhibit great potential for applications in magneto-electric devices. In this letter, we report soft magnetism and microwave properties in FeCoSiB ferromagnetic alloys grown on AlN and AlScN thin films. According to the hysteresis loop, the coercive fields for FeCoSiB/AlN/Mo/Si and FeCoSiB/AlScN/Mo/Si are 43 and 107 Oe, respectively. The influence of interfacial state on magnetic damping is investigated by measuring the magnetic dynamic properties. Scanning electron microscope images show that AlScN film has a larger grain size and rougher surface than that of AlN. The effective magnetization and damping factors are obtained from the ferromagnetic resonance spectroscopy. The damping factor of the magneto-electric heterojunction on AlN/Mo/Si is an order of magnitude higher than that on Si, indicating the interfacial conditions of thin film stacks affect the magnetic dynamic properties. Our findings indicate that the growth quality of piezoelectric materials has a significant impact on magneto-electric films with low-loss tangents at radio-frequency (RF)/microwave frequencies. This work is of practical importance for developing future RF/microwave magneto-electric devices.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143489113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-20DOI: 10.1109/LMAG.2025.3531777
Frederik L. Durhuus;Theis H. van Bijlevelt Rix;Maciej A. Głód;Marco Beleggia;Cathrine Frandsen
Understanding thermal relaxation effects in magnetic nanoparticle (MNP) systems is key to several imaging techniques and clinical applications. Here, we consider the Néel relaxation of compact MNP clusters, using Langevin dynamics simulations to compute the relaxation time as a function of magnetostatic coupling strength. By also analyzing individual thermal reversals, we establish connections between the magnetic structure of a cluster and its Néel relaxation time. In particular, faster relaxation and more exotic behavior are observed for 3-D clusters with several nearly degenerate states, as the magnetization intermittently jumps to metastable states, which can facilitate reversal. Conversely, aggregates with many moments in a single flux-closed loop exhibit fewer metastable states and are efficiently blocked by strong dipole coupling.
{"title":"Néel Relaxation of Magnetic Nanoparticle Clusters","authors":"Frederik L. Durhuus;Theis H. van Bijlevelt Rix;Maciej A. Głód;Marco Beleggia;Cathrine Frandsen","doi":"10.1109/LMAG.2025.3531777","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3531777","url":null,"abstract":"Understanding thermal relaxation effects in magnetic nanoparticle (MNP) systems is key to several imaging techniques and clinical applications. Here, we consider the Néel relaxation of compact MNP clusters, using Langevin dynamics simulations to compute the relaxation time as a function of magnetostatic coupling strength. By also analyzing individual thermal reversals, we establish connections between the magnetic structure of a cluster and its Néel relaxation time. In particular, faster relaxation and more exotic behavior are observed for 3-D clusters with several nearly degenerate states, as the magnetization intermittently jumps to metastable states, which can facilitate reversal. Conversely, aggregates with many moments in a single flux-closed loop exhibit fewer metastable states and are efficiently blocked by strong dipole coupling.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143512878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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