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Special Issue "Advances in Functional Materials with Tunable Magnetic Properties"

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A special issue of Magnetochemistry (ISSN 2312-7481). This special issue belongs to the section "Magnetic Materials".

Deadline for manuscript submissions: 30 November 2023 | Viewed by 1639

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Dr. Paula Corte-Leon

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Guest Editor

1. Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, University of the Basque Country, UPV/EHU, 20018 San Sebastian, Spain
2. Department of Applied Physics I, University of the Basque Country EIG, UPV/EHU, 20018 San Sebastian, Spain
Interests: advanced magnetic materials; amorphous; nanocrystalline and granular magnetic materials; magnetic sensors; magnetic microwires; giant magnetoimpedance effect; hysteretic magnetic properties; domain wall dynamics; functional composite materials
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Dr. Ahmed Talaat

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Guest Editor

1. Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, University of the Basque Country, UPV/EHU, 20018 San Sebastian, Spain
2. Department of Applied Physics I, University of the Basque Country EIG, UPV/EHU, 20018 San Sebastian, Spain
Interests: magnetism and magnetic materials; ferromagnetic metallic glasses; functional (nano)composite materials; giant magne-toimpedance effect; domain wall dynamics; rapid solidification techniques; induction heating; magnetic hyperthermia; me-chanical alloying
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Functional materials with tunable magnetic properties and reduced dimensions in high demand for numerous technological applications, such as sensors, wireless nondestructive control and monitoring security electronic surveillance, microelectronics, medicine, automobile and aircraft industries, energy harvesting and conversion, home entertainment, electrical engineering, magnetic recording, magnetic memories, among others.

This Special Issue will focus on the latest scientific results and novel concepts for the development and applications of highly sensitive magnetic devices, magnetic sensing technology, basic phenomena and fundamental studies of new magnetic materials suitable for the above-mentioned applications.

The overall goal of this issue is to provide the most up-to-date information about recent developments and trends related to optimization in the processing of magnetic materials for the achievement of advanced functional properties.

We are particularly interested in and invite colleagues to submit original research articles that will fit, but are not limited to, one of the topics listed below:

magnetic properties;
magnetic anisotropy;
magnetic sensors;
smart materials and composites;
soft magnetic materials;
amorphous magnetic materials;
nanocrystallization;
rapid annealing;
domain wall dynamics.

Short communications, reviews, and original research articles are encouraged. We look forward to your valuable contributions to this Special Issue.

Dr. Paula Corte-Leon
Dr. Ahmed Talaat
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 100 words) can be sent to the Editorial Office for announcement on this website.

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. Magnetochemistry 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 2700 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.

Published Papers (3 papers)

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Research

Open AccessFeature PaperArticle

NiFe Alloy Nanoparticles Tuning the Structure, Magnetism, and Application for Oxygen Evolution Reaction Catalysis

Rafael A. Raimundo

Vinícius D. Silva

Luciena S. Ferreira

Francisco J. A. Loureiro

and

Magnetochemistry 2023, 9(8), 201; https://doi.org/10.3390/magnetochemistry9080201 - 08 Aug 2023

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Abstract

In this study, Ni-Fe alloy nanoparticles were prepared using the proteic sol–gel method, followed by a reduction in H₂ at 500 and 700 °C, namely hereafter as NiFe-500 and NiFe-700, respectively. The morphological, structural, and magnetic properties were tuned via the thermal treatment in H₂. The samples were studied using XPS, TEM, Mössbauer spectroscopy, DC magnetic measurements, and electrochemical measurements. Ritveld refinements showed that the sample NiFe-500 has FCC (face-centered cubic) and BCC (body-centered cubic) NiFe alloys, while the sample NiFe-700 has only FCC NiFe alloy. For both samples, magnetization measurements in the range of 300–900 K showed the presence of the Griffiths phase, indicating the formation of clusters of either Fe or Ni-Fe alloys rich in Fe. The sample NiFe-500 presented ferromagnetic (FM) transitions at 533, 700, and 834 K, assigned to the alloys Ni₃₇Fe₆₃-FCC, Ni₄₆Fe₅₄-FCC, and Ni₅₅Fe₄₅-FCC, respectively. In contrast, we could not observe the FM transition of the BCC Ni-Fe alloy because of limitations in our experimental setup (T ≤ 900 K). Meanwhile, three FM transitions were observed for the sample NiFe-700 at 480, 655, and 825 K, attributed to the alloys Ni₃₄Fe₆₆-FCC, Ni₄₃Fe₅₇-FCC, and Ni₅₄Fe₄₆-FCC, respectively. At 5 K, the samples NiFe-500 and NiFe-700 have saturation magnetizations of 164.2 and 173.6 emu g⁻¹, respectively. For application in Oxygen Evolution Reaction catalysis, the samples NiFe-500 and NiFe-700 showed different overpotentials of 319 and 307 mV at 10 mA cm⁻². These low overpotential values indicate a higher electrochemical activity of the FCC Ni-Fe alloy and, for both samples, a superior electrocatalytic activity in comparison to RuO₂ e IrO₂ conventional catalysts. Furthermore, the samples showed high electrochemical stability in chrono potentiometric studies for up to 15 h. This current work highlights that the Ni-Fe alloys produced via the proteic sol–gel and with a reduction in H₂ methods can be promising for OER systems due to their good performance and low costs. Full article

(This article belongs to the Special Issue Advances in Functional Materials with Tunable Magnetic Properties)

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Open AccessArticle

Magnetic and Magnetocaloric Properties of Nano- and Polycrystalline Bulk Manganites La_0.7Ba_(0.3−x)Ca_xMnO₃ (x ≤ 0.25)

and

Magnetochemistry 2023, 9(7), 170; https://doi.org/10.3390/magnetochemistry9070170 - 30 Jun 2023

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Abstract

Here we report the synthesis and investigation of bulk and nano-sized La_0.7Ba_0.3−xCa_xMnO₃ (x = 0, 0.15, 0.2 and 0.25) compounds that are promising candidates for magnetic refrigeration applications. We compare the structural and magnetic properties of bulk and nano-scale polycrystalline La_0.7Ba_0.3−xCa_xMnO₃ for potential use in magnetic cooling systems. Solid-state reactions were implemented for bulk materials, while the sol–gel method was used for nano-sized particles. Structurally and morphologically, the samples were investigated by X-ray diffraction (XRD), optical microscopy and transmission electron microscopy (TEM). Oxygen stoichiometry was investigated by iodometry. Bulk compounds exhibit oxygen deficiency, while nano-sized particles show excess oxygen. Critical magnetic behavior was revealed for all samples using the modified Arrott plot (MAP) method and confirmed by the Kouvel–Fisher (KF) method. The bulk polycrystalline compound behavior was better described by the tricritical field model, while the nanocrystalline samples were governed by the mean-field model. Resistivity in bulk material showed a peak at a temperature T_p1 attributed to grain boundary conditions and at T_p2 associated with a Curie temperature of T_c_. Parent polycrystalline sample La_0.7Ba_0.3MnO₃ has T_c at 340 K. Substitution of x = 0.15 of Ca brings T_c to 308 K, and x = 0.2 brings it to 279 K. Nanocrystalline samples exhibit a very wide effective temperature range in the magnetocaloric effect, up to 100 K. Bulk compounds exhibit a high and sharp peak in magnetic entropy change, up to 7 J/kgK at 4 T at T_c for x = 0.25. To compare the magnetocaloric performances of the studied compounds, both relative cooling power (RCP) and temperature-averaged entropy change (TEC) figures of merit were used. RCP is comparable for bulk polycrystalline and nano-sized samples of the same substitution level, while TEC shows a large difference between the two systems. The combination of bulk and nanocrystalline materials can contribute to the effectiveness and improvement of magnetocaloric materials. Full article

(This article belongs to the Special Issue Advances in Functional Materials with Tunable Magnetic Properties)

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Open AccessArticle

Structural and Magnetic Investigations of the Novel Pyrophosphate Na₇Ni₃Fe(P₂O₇)₄

and

Magnetochemistry 2023, 9(7), 162; https://doi.org/10.3390/magnetochemistry9070162 - 24 Jun 2023

Viewed by 381

Abstract

A novel pyrophosphate Na₇Ni₃Fe(P₂O₇)₄ was synthesized in two distinct forms, single-crystal and powder. Single-crystal X-ray diffraction was used to determine the crystal structure, and powder X-ray diffraction and scanning electron microscopy were used to [...] Read more.

\bar{1}

space group of the triclinic system with a = 6.3677 (2) Å, b = 9.3316 (4) Å, c = 10.8478 (4) Å, α = 65.191 (1)°, β = 80.533 (1)° and γ = 73.042 (1)°. The crystal framework is assembled from the linkage of centro-symmetrical clusters Ni₂(Ni/Fe)₂P₄O₂₈. Each cluster consists of two (Fe1/Ni1)O₆ octahedra, two Ni2O₆ octahedra and two P₂O₇ units. The linkage of these clusters is provided by two other P₂O₇ units to generate a three-dimensional structure with distinct tunnels in the [100], [010] and [001] directions, housing the Na⁺ cations. The infrared and Raman analyses show the characteristic bands of the pyrophosphate anion P₂O₇⁴⁻. Remarkably, the magnetic investigations revealed the coexistence of two magnetic transitions at ~29 K and ~4.5 K with dominating antiferromagnetic interactions. Full article

(This article belongs to the Special Issue Advances in Functional Materials with Tunable Magnetic Properties)

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