Editorial

4 pages, 207 KiB

Open AccessEditorial

Special Issue: Soft and Hard Magnetic Materials: Latest Advances and Prospects

by Cristina Favieres

Magnetochemistry 2023, 9(7), 179; https://doi.org/10.3390/magnetochemistry9070179 - 10 Jul 2023

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The Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects aims to provide researchers with an overview of some aspects of the current research in magnetic materials from theoretical studies to their applications, including their fabrication and characterization [...] Full article

(This article belongs to the Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects)

Research

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15 pages, 4019 KiB

Open AccessFeature PaperArticle

Transformation Pathways of Ferromagnetic Mn-Al-Ga-Ni

by Shane Palmer, John Martin, Paul Lindquist and Peter Müllner

Magnetochemistry 2023, 9(5), 128; https://doi.org/10.3390/magnetochemistry9050128 - 11 May 2023

Cited by 1 | Viewed by 969

Abstract

This study investigates the impact of alloying Mn-Al-Ga with 3 at.-% Ni and the stability and formation mechanisms of the

τ

phase and the resulting magnetic properties. The stabilizing effect of Ga on the

τ

phase was verified, and the ternary alloy’s magnetization [...] Read more.

This study investigates the impact of alloying Mn-Al-Ga with 3 at.-% Ni and the stability and formation mechanisms of the

τ

phase and the resulting magnetic properties. The stabilizing effect of Ga on the

τ

phase was verified, and the ternary alloy’s magnetization was measured up to

M_{2 T} = 482

k A m^{- 1}

. The phase transformation from

γ

₂ to

τ

in ternary Mn-Al-Ga was demonstrated microscopically. The solubility limit of Ni into the

τ

phase was exceeded at 3 at.-% and a primitive cubic κ phase formed. The Ni addition stabilized the

τ

phase. The highest magnetization at 2 T for the Mn₅₂Al_39.4Ga_5.6Ni₃ alloy was

M_{2 T} = 416 k A m^{- 1}

. A new transformation pathway was demonstrated by first annealing the Mn-Al-Ga-Ni alloy at 800 °C for 24 h, which forms a nearly single κ phase, which is followed by a second anneal at 500 °C for 24 h at which the

τ

phase formed with some remaining κ phase. This is a new transformation mechanism since it involves a phase reaction from κ to τ. The energy product of the Mn-Al-Ga-Ni alloy exceeded that of the ternary Mn-Al-Ga alloy by a factor of 4.5. The κ-phase particles in the Mn-Al-Ga-Ni alloy hinder magnetic domain boundary motion, thus providing a method for magnetic hardening and increasing the energy product. Full article

(This article belongs to the Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects)

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10 pages, 2367 KiB

Open AccessFeature PaperArticle

Magnetic Properties of the Fe₂B Alloy Doped with Transition Metal Elements

by Diana Benea and Viorel Pop

Magnetochemistry 2023, 9(4), 109; https://doi.org/10.3390/magnetochemistry9040109 - 20 Apr 2023

Cited by 2 | Viewed by 1169

Abstract

The intrinsic magnetic properties (magnetic moments, magneto-crystalline anisotropy, Curie temperatures) of the (Fe_1−xM_x)₂B alloys have been calculated using the spin-polarized relativistic Korringa–Kohn–Rostoker (SPR-KKR) band structure method. The transition metal elements M (M = Co, Ni, Mo, Ta, [...] Read more.

The intrinsic magnetic properties (magnetic moments, magneto-crystalline anisotropy, Curie temperatures) of the (Fe_1−xM_x)₂B alloys have been calculated using the spin-polarized relativistic Korringa–Kohn–Rostoker (SPR-KKR) band structure method. The transition metal elements M (M = Co, Ni, Mo, Ta, W and Re) considered in the present study are reported to form stable M₂B or FeMB alloys with a tetragonal Cu₂Al structure type. The experimental studies show that the Fe₂B alloy has a large magnetization (173 Am²/kg), a large Curie temperature (1017 K) and a relatively large anisotropy constant K₁ (−0.80 MJ/m³), but the alloy is inappropriate for permanent magnet applications due to in-plane easy magnetization axis (EMD). The present investigations show the magnetocrystalline anisotropy behaviour by doping with selected d-elements aiming to find an appropriate dopant which is able to switch the EMD from planar to axial and to enhance the magnetocrystalline anisotropy energy (MAE) value without a major decrease of magnetization and Curie temperature. Full article

(This article belongs to the Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects)

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13 pages, 3605 KiB

Open AccessArticle

Dissolution of Lysozyme Amyloid Fibrils Using Magnetic Nanoparticles in an Alternating Magnetic Field: Design of an Effective Treatment for Cutaneous Amyloidosis

by Natália Andrýsková, Hana Vrbovská, Melánia Babincová, Peter Babinec and Mária Šimaljaková

Magnetochemistry 2023, 9(3), 84; https://doi.org/10.3390/magnetochemistry9030084 - 17 Mar 2023

Cited by 2 | Viewed by 1354

Abstract

The purpose of this study was to apply functionalized magnetic nanoparticles for the treatment of amyloidosis, a disease characterized by the accumulation of aberrant protein forms with an insoluble amyloid structure. The dissolution and clearance of these extremely stable fibrils from lesions is [...] Read more.

The purpose of this study was to apply functionalized magnetic nanoparticles for the treatment of amyloidosis, a disease characterized by the accumulation of aberrant protein forms with an insoluble amyloid structure. The dissolution and clearance of these extremely stable fibrils from lesions is very complicated. For this purpose, we examined the possibility of using magnetic nanoparticles that generate heat in an external alternating magnetic field with a frequency of 3.5 MHz. As a convenient model system, we used lysozyme fibrils. For the quantification of fibrillar status, we used Thioflavin T and Congo red, specific dyes which change their spectroscopic properties upon binding with the cross-beta structure of fibrils. We found that by using fluorescence, and polarization microscopy, as well as absorption spectrophotometry, the amyloid-like fibrils can be almost completely dissolved. The obtained results suggest that the application of magnetic nanoparticles could be a possible therapeutic intervention in cutaneous amyloidosis. Full article

(This article belongs to the Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects)

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11 pages, 4071 KiB

Open AccessArticle

Magnetic Properties and Microstructure of Ce-Cu-Al Low Melting Alloy Bonding Sm₂Fe₁₇N₃ Magnet Fabricated by the Hot-Pressing Method

by Jingwu Zheng, Shitong Yu, Heng Huang, Rongyao Li, Wei Cai, Haibo Chen, Juan Li, Liang Qiao, Yao Ying, Wangchang Li, Jing Yu and Shenglei Che

Magnetochemistry 2022, 8(11), 149; https://doi.org/10.3390/magnetochemistry8110149 - 07 Nov 2022

Cited by 3 | Viewed by 1813

Abstract

Sm₂Fe₁₇N₃ compounds, having excellent intrinsic magnetic properties, are prone to decomposition at high temperatures; thus, a low melting point metal binder is the key to prepare high performance bulk magnets at low temperatures. In this paper, a new [...] Read more.

Sm₂Fe₁₇N₃ compounds, having excellent intrinsic magnetic properties, are prone to decomposition at high temperatures; thus, a low melting point metal binder is the key to prepare high performance bulk magnets at low temperatures. In this paper, a new low melting point alloy Ce₇₂Cu_28-xAl_x was used as the binders, and high-performance Ce-based alloy bonding Sm₂Fe₁₇N₃ magnets were realized by the hot-pressing method. The experimental results demonstrated that the content of Al in the Ce-based alloys had an important influence on the performance of the magnets. High performance Sm-Fe-N bonded magnets with remanence of 10.19 KGs and maximum magnetic energy product of 21.06 MGOe were achieved by using 5 wt.% Ce₇₂Cu₂₂Al₆ alloy as a binder. At the same time, it was found that the Ce₇₂Cu_28-xAl_x alloy has a lower density and better bonding effect than the common Zn binder. Its bonding magnets still have higher performance even with extremely high oxygen content. Therefore, Ce₇₂Cu_28-xAl_x alloy with low melting point is a promising new rare earth-based alloy binder. If the oxygen content of the alloy powders could be reduced, higher performance Sm₂Fe₁₇N₃ bonded magnets can be prepared. Full article

(This article belongs to the Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects)

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23 pages, 9233 KiB

Open AccessArticle

Tailoring Magnetic and Transport Anisotropies in Co_100−x–Cu_x Thin Films through Obliquely Grown Nano-Sheets

by Cristina Favieres, José Vergara and Vicente Madurga

Magnetochemistry 2022, 8(1), 4; https://doi.org/10.3390/magnetochemistry8010004 - 28 Dec 2021

Cited by 4 | Viewed by 1994

Abstract

The magnetic and transport properties of pulsed laser-deposited Co_100−x–Cu_x thin films were tailored through their nano-morphology and composition by controlling for the deposition geometry, namely normal or oblique deposition, and their Cu content. All films were composed of an amorphous [...] Read more.

The magnetic and transport properties of pulsed laser-deposited Co_100−x–Cu_x thin films were tailored through their nano-morphology and composition by controlling for the deposition geometry, namely normal or oblique deposition, and their Cu content. All films were composed of an amorphous Co matrix and a textured growth of Cu nanocrystals, whose presence and size d increased as x increased. For x = 50, all films were superparamagnetic, regardless of deposition geometry. The normally deposited films showed no in-plane magnetic anisotropy. On the contrary, controllable in-plane uniaxial magnetic anisotropy in both direction and magnitude was generated in the obliquely deposited films. The magnetic anisotropy field H_k remained constant for x = 0, 5 and 10, H_k ≈ 35 kAm⁻¹, and decreased to 28 and 26 kAm⁻¹ for x = 20 and 30, respectively. This anisotropy had a magnetostatic origin due to a tilted nano-sheet morphology. In the normally deposited films, the coercive field H_c increased when x increased, from 200 (x = 0) to 1100 Am⁻¹ (x = 30). In contrast, in obliquely deposited films, H_c decreased from 1500 (x = 0) to 100 Am⁻¹ (x = 30) as x increased. Activation energy spectra corresponding to structural relaxation phenomena in obliquely deposited films were obtained from transport property measurements. They revealed two peaks, which also depended on their nano-morphology and composition. Full article

(This article belongs to the Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects)

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12 pages, 3408 KiB

Open AccessArticle

Magnetic Properties of a Ni Nanonet Grown in Superfluid Helium under Laser Irradiation

by Oksana Koplak, Elizaveta Dvoretskaya, Maxim Stepanov, Alexander Karabulin, Vladimir Matyushenko and Roman Morgunov

Magnetochemistry 2021, 7(10), 139; https://doi.org/10.3390/magnetochemistry7100139 - 11 Oct 2021

Cited by 1 | Viewed by 2115

Abstract

A nanonet consisting of ultrathin Ni nanowires (diameter <4 nm) and Ni nanoballs (diameter <20 nm) has been grown through laser ablation of a Ni target in superfluid helium. At a low Ni concentration, the nanonet consists mainly of nanowires and manifests a [...] Read more.

A nanonet consisting of ultrathin Ni nanowires (diameter <4 nm) and Ni nanoballs (diameter <20 nm) has been grown through laser ablation of a Ni target in superfluid helium. At a low Ni concentration, the nanonet consists mainly of nanowires and manifests a rectangular magnetic hysteresis loop, while an increase in the Ni concentration results in an increase in both the concentration and diameter of the nanoballs. A decrease in hysteresis loop rectangularity is observed as the concentration of the nanoball increases. We show that the composition of the system can be determined from the changes in the magnetic hysteresis loop and the temperature dependence of magnetization. The significance of the work consists of the observation of evolution of magnetic properties of the ferromagnetic nanonet, while its composition varies from nanowires to a combined nanowires–nanoballs system. Full article

(This article belongs to the Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects)

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20 pages, 7413 KiB

Open AccessArticle

A Ti/Pt/Co Multilayer Stack for Transfer Function Based Magnetic Force Microscopy Calibrations

by Baha Sakar, Sibylle Sievers, Alexander Fernández Scarioni, Felipe Garcia-Sanchez, İlker Öztoprak, Hans Werner Schumacher and Osman Öztürk

Magnetochemistry 2021, 7(6), 78; https://doi.org/10.3390/magnetochemistry7060078 - 01 Jun 2021

Cited by 4 | Viewed by 2839

Abstract

Magnetic force microscopy (MFM) is a widespread technique for imaging magnetic structures with a resolution of some 10 nanometers. MFM can be calibrated to obtain quantitative (qMFM) spatially resolved magnetization data in units of A/m by determining the calibrated point spread function of [...] Read more.

Magnetic force microscopy (MFM) is a widespread technique for imaging magnetic structures with a resolution of some 10 nanometers. MFM can be calibrated to obtain quantitative (qMFM) spatially resolved magnetization data in units of A/m by determining the calibrated point spread function of the instrument, its instrument calibration function (ICF), from a measurement of a well-known reference sample. Beyond quantifying the MFM data, a deconvolution of the MFM image data with the ICF also corrects the smearing caused by the finite width of the MFM tip stray field distribution. However, the quality of the calibration depends critically on the calculability of the magnetization distribution of the reference sample. Here, we discuss a Ti/Pt/Co multilayer stack that shows a stripe domain pattern as a suitable reference material. A precise control of the fabrication process, combined with a characterization of the sample micromagnetic parameters, allows reliable calculation of the sample’s magnetic stray field, proven by a very good agreement between micromagnetic simulations and qMFM measurements. A calibrated qMFM measurement using the Ti/Pt/Co stack as a reference sample is shown and validated, and the application area for quantitative MFM measurements calibrated with the Ti/Pt/Co stack is discussed. Full article

(This article belongs to the Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects)

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24 pages, 10347 KiB

Open AccessArticle

Estimation of the Electricity Storage Volume Density of Compact SMESs of a New Concept Based on Si Microfabrication Technologies

by Tomoyoshi Motohiro, Minoru Sasaki, Joo-hyong Noh and Osamu Takai

Magnetochemistry 2021, 7(3), 44; https://doi.org/10.3390/magnetochemistry7030044 - 23 Mar 2021

Cited by 5 | Viewed by 2154

Abstract

A compact superconducting magnetic energy storage system (SMES) produced by Si micro fabrication technologies has been proposed to improve electricity storage volume density, w, in the sub-Wh/L range of conventional SMESs and to produce them at a low cost by mass production. [...] Read more.

A compact superconducting magnetic energy storage system (SMES) produced by Si micro fabrication technologies has been proposed to improve electricity storage volume density, w, in the sub-Wh/L range of conventional SMESs and to produce them at a low cost by mass production. In parallel with the experimental development reported previously, a series of trials was performed to estimate a feasible value of w based on the calculation of the magnetic field generated by the compact SMES by improving the calculation models step by step. In this work, the experimentally obtained magnetic flux density dependence of superconductive critical current density was taken into consideration for the first time in this series of trials, together with the additional improvement of the calculation models. The results of the estimation indicated that a compact SMES produced by the proposed concept can attain a w in the Wh/L range or more, ranking with or surpassing that of presently used capacitors. Full article

(This article belongs to the Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects)

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Review

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24 pages, 6611 KiB

Open AccessReview

Laser Additive Manufacturing of Fe-Based Magnetic Amorphous Alloys

by Merve G. Ozden and Nicola A. Morley

Magnetochemistry 2021, 7(2), 20; https://doi.org/10.3390/magnetochemistry7020020 - 29 Jan 2021

Cited by 28 | Viewed by 4552

Abstract

Fe-based amorphous materials offer new opportunities for magnetic sensors, actuators, and magnetostrictive transducers due to their high saturation magnetostriction (λ_s = 20–40 ppm) and low coercive field compared with polycrystalline Fe-based alloys, which have high magnetostriction but large coercive fields and [...] Read more.

Fe-based amorphous materials offer new opportunities for magnetic sensors, actuators, and magnetostrictive transducers due to their high saturation magnetostriction (λ_s = 20–40 ppm) and low coercive field compared with polycrystalline Fe-based alloys, which have high magnetostriction but large coercive fields and Co-based amorphous alloys with small magnetostriction (λ_s = −3 to −5 ppm). Additive layer manufacturing (ALM) offers a new fabrication technique for more complex net-shaping designs. This paper reviews the two different ALM techniques that have been used to fabricate Fe-based amorphous magnetic materials, including the structural and magnetic properties. Selective laser melting (SLM)—a powder-bed fusion technique—and laser-engineered net shaping (LENS)—a directed energy deposition method—have both been utilised to fabricate amorphous alloys, owing to their high availability and low cost within the literature. Two different scanning strategies have been introduced by using the SLM technique. The first strategy is a double-scanning strategy, which gives rise to maximum relative density of 96% and corresponding magnetic saturation of 1.22 T. It also improved the glassy phase content by an order of magnitude of 47%, as well as improving magnetic properties (decreasing coercivity to 1591.5 A/m and increasing magnetic permeability to around 100 at 100 Hz). The second is a novel scanning strategy, which involves two-step melting: preliminary laser melting and short pulse amorphisation. This increased the amorphous phase fraction to a value of up to 89.6%, and relative density up to 94.1%, and lowered coercivity to 238 A/m. On the other hand, the LENS technique has not been utilised as much as SLM in the production of amorphous alloys owing to its lower geometric accuracy (0.25 mm) and lower surface quality, despite its benefits such as providing superior mechanical properties, controlled composition and microstructure. As a result, it has been commonly used for large parts with low complexity and for repairing them, limiting the production of amorphous alloys because of the size limitation. This paper provides a comprehensive review of these techniques for Fe-based amorphous magnetic materials. Full article

(This article belongs to the Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects)

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