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Crystals
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New Trends in Materials for Permanent Magnets
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New Trends in Materials for Permanent Magnets

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".

Deadline for manuscript submissions: closed (20 July 2025) | Viewed by 3556

Special Issue Editors

Dr. Marian Grigoras

E-Mail Website
Guest Editor
National Institute of Research and Development for Technical Physics, Mangeron Av 47, 6600 Iaşi, Romania
Interests: magnetic materials; magnetic properties; permanent magnets; nanocomposite materials; physics of surfaces and interfaces; magnetic thin films
Special Issues, Collections and Topics in MDPI journals
Dr. Mihaela Lostun

E-Mail Website
Guest Editor
National Institute of Research and Development for Technical Physics, Mangeron Av 47, 6600 Iaşi, Romania
Interests: nanostructured materials; advanced materials; nanoparticle synthesis; surface characterization; magnetic materials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Permanent magnets are one of the most important materials in modern technology, being widely used in industrial and military systems and everyday life. The fields of application of permanent magnets, such as the energy/electrical, information/communication technology, automotive/robotics, and biomedical engineering industries, are fully expanding, leading to an accelerated demand for high-performance permanent magnets. This, together with growing concerns about environmental degradation due to the exploitation of rare earths, rising costs, and availability problems of rare earths, has led to intense efforts worldwide to search for alternative materials with the potential to prepare new types of permanent magnets.

In this Special Issue, we would like to gather contributions that address the latest developments in the field of permanent magnets, such as improving magnetic properties, reasonable and balanced use of rare earth resources, recycling, and alternatives to rare-earth-based modeling.

Dr. Marian Grigoras
Dr. Mihaela Lostun
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2100 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • permanent magnet
  • magnetic materials
  • magnetic properties
  • maximum energy product
  • rare earth
  • nanocomposite
  • powders
  • melt-spun ribbons
  • recycling

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Published Papers (4 papers)

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Research

14 pages, 2974 KB  
Article
Microstructural and Magnetic Evolution of α″-Fe16N2 Bulk Magnets Consolidated by Spark Plasma Sintering
by Marian Grigoras, Mihaela Lostun, Marieta Porcescu, George Stoian and Nicoleta Lupu
Crystals 2025, 15(11), 969; https://doi.org/10.3390/cryst15110969 - 11 Nov 2025
Viewed by 397
Abstract
The development of rare-earth-free permanent magnets represents a strategic direction in advanced magnetic materials research. Among the most promising candidates, the metastable α″-Fe16N2 phase stands out due to its exceptionally high saturation magnetization. In this work, α″-Fe16N2 [...] Read more.
The development of rare-earth-free permanent magnets represents a strategic direction in advanced magnetic materials research. Among the most promising candidates, the metastable α″-Fe16N2 phase stands out due to its exceptionally high saturation magnetization. In this work, α″-Fe16N2 powders produced by gas atomization followed by nitriding were consolidated via Spark Plasma Sintering (SPS). The effects of sintering temperature (498–598 K) and pressure (40–80 MPa) on phase evolution, densification, microstructure, and magnetic properties have been systematically investigated. Optimal processing conditions were identified at 548 K and 60 MPa, providing a balance between densification (~80% of the theoretical density), phase stability, and magnetic performance. X-ray diffraction revealed that the α″-Fe16N2 phase remains stable up to ~523 K, while its decomposition into α-Fe and γ′-Fe4N becomes significant at higher temperatures. The consolidated samples exhibited a saturation magnetization of ~230 Am2/kg, a maximum coercivity of ~86.5 kA/m, and a Mr/Ms ratio of 0.42. δM curve analysis indicated a transition from magnetostatic interactions (at low pressures) to exchange-dominated coupling (at intermediate and high pressures). These findings demonstrate the potential of SPS processing to preserve the α″-Fe16N2 phase and produce rare-earth-free magnetic compacts with competitive magnetic performance, providing a basis for further process optimization. Full article
(This article belongs to the Special Issue New Trends in Materials for Permanent Magnets)
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18 pages, 2720 KB  
Article
Influence of Nanocrystallite Size on Magnetic Properties of Iron Nitride γ’-Fe4N
by Kamila Klimza, Grzegorz Leniec, Karol Synoradzki, Rafał Pelka, Urszula Nowosielecka, Izabela Moszyńska, Aleksander Guskos, Grzegorz Żołnierkiewicz and Nikos Guskos
Crystals 2025, 15(11), 956; https://doi.org/10.3390/cryst15110956 - 5 Nov 2025
Viewed by 318
Abstract
In this paper, samples of nanocrystalline iron nitride γ’-Fe4N, doped with small amounts of hardly reducible promoter oxides (Al2O3, CaO, and K2O), were subjected to electron magnetic resonance (EMR) measurements. The samples differed in the [...] Read more.
In this paper, samples of nanocrystalline iron nitride γ’-Fe4N, doped with small amounts of hardly reducible promoter oxides (Al2O3, CaO, and K2O), were subjected to electron magnetic resonance (EMR) measurements. The samples differed in the average nanocrystallite size of iron nitride (23–54 nm). The EMR analysis was performed to probe the magnetic characteristics of the nanoparticles. The spectra, fitted with a Voigt function, were deconvoluted into contributions from the γ’-Fe4N phase in the nanoparticle core and from surface-associated iron ions. The resulting magnetic responses were quantitatively correlated with nanoparticle size, elucidating finite-size effects governing the system’s magnetic behavior. Full article
(This article belongs to the Special Issue New Trends in Materials for Permanent Magnets)
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14 pages, 7010 KB  
Article
Magnetic Properties of Fe-Nb-B-RE (RE = Tb, Tb/Y, Tb/Nd) Amorphous and Annealed Melt-Spun Ribbons
by Artur Chrobak, Grzegorz Ziółkowski, Ondrej Zivotsky, Piotr Pawlik and Joanna Klimontko
Crystals 2025, 15(11), 933; https://doi.org/10.3390/cryst15110933 - 30 Oct 2025
Viewed by 265
Abstract
This paper discusses the magnetic properties of Fe-Nb-B-RE (RE = Tb, Tb/Y, Tb/Nd) melt-spun ribbons. Samples were obtained using a typical melt-spinning technique. The dominant amorphous state was confirmed by XRD and thermomagnetic measurements. It was shown that the alloying additions of the [...] Read more.
This paper discusses the magnetic properties of Fe-Nb-B-RE (RE = Tb, Tb/Y, Tb/Nd) melt-spun ribbons. Samples were obtained using a typical melt-spinning technique. The dominant amorphous state was confirmed by XRD and thermomagnetic measurements. It was shown that the alloying additions of the RE elements used introduce magnetic anisotropy into amorphous Fe-based structures. This fact was confirmed by magnetic hysteresis loops as well as Kerr microscopy observations. Moreover, increasing Tb content leads to the appearance of a “two-step” reverse magnetization curve. The mean field theory analysis revealed that Tb addition reduces the exchange interaction between the Fe-Fe magnetic moments. The applied thermal treatment caused partial crystallization and the formation of hard magnetic phases with ultra-high coercivity. Full article
(This article belongs to the Special Issue New Trends in Materials for Permanent Magnets)
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13 pages, 1863 KB  
Article
Theoretical Study of the Magnetic Properties of the SmFe12−xMox (x = 1, 2) and SmFe10Mo2H Compounds
by Diana Benea, Eduard Barna, Viorel Pop and Olivier Isnard
Crystals 2024, 14(7), 598; https://doi.org/10.3390/cryst14070598 - 27 Jun 2024
Viewed by 1632
Abstract
We present theoretical investigations examining the electronic and magnetic properties of the SmFe12−xMox (x = 1, 2) and SmFe10Mo2H compounds, including magneto-crystalline anisotropy, magnetic moments, exchange-coupling parameters, and Curie temperatures. The spin-polarized fully relativistic Korringa–Kohn–Rostoker (SPR-KKR) [...] Read more.
We present theoretical investigations examining the electronic and magnetic properties of the SmFe12−xMox (x = 1, 2) and SmFe10Mo2H compounds, including magneto-crystalline anisotropy, magnetic moments, exchange-coupling parameters, and Curie temperatures. The spin-polarized fully relativistic Korringa–Kohn–Rostoker (SPR-KKR) band structure method has been employed, using the coherent potential approximation (CPA) to deal with substitutional disorder. Hubbard-U correction was applied to the local spin density approximation (LSDA+U) in order to account for the significant correlation effects arising from the 4f electronic states of Sm. According to our calculations, the total magnetic moments increases with H addition, in agreement with experimental data. Adding one H atom in the near-neighbor environment of the Fe 8j site reduces the magnetic moments of Fe 8j and enhances the magnetic moment of Fe 8f. For every investigated alloy, the site-resolved spin magnetic moments of Fe on the 8i, 8j, and 8f sites exhibit the same magnitude sequence, with msFe (8i) > msFe (8j) > msFe (8f). While the addition of H has a positive impact on magneto-crystalline anisotropy energy (MAE), the increase in Mo concentration is detrimental to MAE. The computed exchange-coupling parameters reveal the highest values between the closest Fe 8i spins, followed by Fe 8i and Fe 8j spins, for all investigated alloys. The Curie temperature of the alloys under investigation is increased by decreasing the Mo concentration or by H addition, which is qualitatively consistent with experimental findings. Full article
(This article belongs to the Special Issue New Trends in Materials for Permanent Magnets)
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