Magnetochemistry

13 pages, 3035 KiB

Open AccessArticle

The Magnetostriction of Amorphous Magnetic Microwires: The Role of the Local Atomic Environment and Internal Stresses Relaxation

by Valentina Zhukova, Alfonso García-Gómez, Alvaro Gonzalez, Margarita Churyukanova, Sergey Kaloshkin, Paula Corte-Leon, Mihail Ipatov, Jesus Olivera and Arcady Zhukov

Magnetochemistry 2023, 9(10), 222; https://doi.org/10.3390/magnetochemistry9100222 - 20 Oct 2023

Cited by 1 | Viewed by 1278

Abstract

We studied the magnetostriction coefficients, λ_s, Curie temperature, T_c, and their dependence on annealing conditions in Fe₄₇Ni₂₇Si₁₁B₁₃C₂ and Co₆₇Fe_3.9Ni₁.₅B₁₁.₅ [...] Read more.

We studied the magnetostriction coefficients, λ_s, Curie temperature, T_c, and their dependence on annealing conditions in Fe₄₇Ni₂₇Si₁₁B₁₃C₂ and Co₆₇Fe_3.9Ni₁.₅B₁₁.₅Si_14.5Mo_1.6 amorphous glass-coated microwires with rather different character of hysteresis loops. A positive λ_s ≈ 20 × 10⁻⁶ is observed in as-prepared Fe₄₇Ni₂₇Si₁₁B₁₃C_2, while low and negative λ_s ≈ −0.3 × 10⁻⁶ is obtained for Co₆₇Fe_3.9Ni₁.₅B₁₁.₅Si_14.5Mo_1.6 microwire. Annealing affects the magnetostriction coefficients and Curie temperatures, T_c, of both Fe₄₇Ni₂₇Si₁₁B₁₃C₂ and Co₆₇Fe_3.9Ni₁.₅B₁₁.₅Si_14.5Mo_1.6 glass-coated microwires in a similar way. Observed dependencies of hysteresis loops, λ_s and T_c on annealing conditions are discussed in terms of superposition of internal stresses relaxation and structural relaxation of studied microwires. We observed linear λ_s dependence on applied stress, σ, in both studied microwires. A decrease in the magnetostriction coefficient upon applied stress is observed for Co-rich microwires with low and negative magnetostriction coefficient. On the contrary, for Fe-Ni-rich microwires with a positive magnetostriction coefficient, an increase in the magnetostriction coefficient with applied stress is observed. The observed results are discussed considering the internal stresses relaxation and short range atomic rearrangements induced by annealing on hysteresis loops, magnetostriction coefficients and Curie temperatures of studied microwires. Full article

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

► Show Figures

Figure 1

13 pages, 911 KiB

Open AccessArticle

Estimation of Radiation Damping Rates Using ¹³³Cs, ⁷Li and ³¹P Solution NMR Spectroscopy and a Theoretical NMR RASER Model

by Eisuke Chikayama, Stephan J. Ginthör, Matthias Bechmann and Norbert Müller

Magnetochemistry 2023, 9(10), 221; https://doi.org/10.3390/magnetochemistry9100221 - 18 Oct 2023

Viewed by 1093

Abstract

Radio amplification using stimulated emission of radiation (RASER) effects in the NMR can increase NMR signals over time due to a feedback loop between the sample magnetization and the probe coil coupled with radiation damping (RD). Previously, RD rates had been directly observed [...] Read more.

Radio amplification using stimulated emission of radiation (RASER) effects in the NMR can increase NMR signals over time due to a feedback loop between the sample magnetization and the probe coil coupled with radiation damping (RD). Previously, RD rates had been directly observed only for the ¹H, ³He, ¹⁷O and ¹²⁹Xe nuclei. We report that experimental direct measurements of an NMR RASER to determine RD time constants for the three heteronuclei (¹³³Cs (I = 7/2), ⁷Li (I = 3/2) and ³¹P (I = 1/2)) in a highly concentrated solution from the NMR RASER emissions using a conventional NMR probe. Under conditions where the RD rate exceeds the transverse relaxation rate (i.e., the NMR RASER condition is fulfilled), we recorded both the transverse NMR RASER response to imperfect inversion and the recovery of longitudinal magnetization. The data were directly evaluated based on the well-known Bloom model as estimated RD rate constants of 8.0, 1.8 and 25 Hz for ¹³³Cs, ⁷Li and ³¹P, respectively. The proposed method can be applied to observe RD rate constants for the other nuclei as well. Full article

(This article belongs to the Special Issue Future Prospects for NMR Spectroscopy: A Perspective)

► Show Figures

Figure 1

22 pages, 3668 KiB

Open AccessArticle

Superparamagnetism of Artificial Glasses Based on Rocks: Experimental Data and Theoretical Modeling

by Petr Kharitonskii, Elena Sergienko, Andrey Ralin, Evgenii Setrov, Timur Sheidaev, Kamil Gareev, Alexander Ustinov, Nikita Zolotov, Svetlana Yanson and Danil Dubeshko

Magnetochemistry 2023, 9(10), 220; https://doi.org/10.3390/magnetochemistry9100220 - 08 Oct 2023

Viewed by 1344

Abstract

Artificial glasses containing nanoscale inclusions of iron oxides, including magnetite and hematite, were obtained via the method of the high-temperature melting of rocks. The main factors influencing the magnetic properties of glasses are the composition of the initial charge and the conditions of [...] Read more.

Artificial glasses containing nanoscale inclusions of iron oxides, including magnetite and hematite, were obtained via the method of the high-temperature melting of rocks. The main factors influencing the magnetic properties of glasses are the composition of the initial charge and the conditions of cooling of the melt. The data of magnetic granulometry and frequency-field dependencies of magnetic susceptibility showed the presence of a sufficiently large superparamagnetic fraction in the samples. Coordinated theoretical modeling using two independent models that take into consideration possible the chemical inhomogeneity of particles and magnetostatic interaction between them made it possible to calculate hysteresis characteristics corresponding to the experiment and to estimate ferrimagnetic concentrations in the samples, including the superparamagnetic fraction. Full article

(This article belongs to the Section Magnetic Nanospecies)

► Show Figures

Figure 1

14 pages, 2536 KiB

Open AccessArticle

Phase Separation in the Double Perovskite Sr₂FeNbO_6-δ

by Daniil Popov, Ruslan Batulin, Mikhail Cherosov, Farit Vagizov, Almaz Zinnatullin, Tatiana Chupakhina, Yuliya Deeva, Tanmoy Maiti and Rushana Eremina

Magnetochemistry 2023, 9(10), 219; https://doi.org/10.3390/magnetochemistry9100219 - 08 Oct 2023

Cited by 2 | Viewed by 1129

Abstract

The ceramic perovskite Sr₂FeNbO_6-δ was synthesized via the solution combustion precursor method. X-ray phase analysis showed that the sample is single-phase and does not contain impurities. The specific heat capacity and the Mössbauer spectra were measured for the Sr₂ [...] Read more.

The ceramic perovskite Sr₂FeNbO_6-δ was synthesized via the solution combustion precursor method. X-ray phase analysis showed that the sample is single-phase and does not contain impurities. The specific heat capacity and the Mössbauer spectra were measured for the Sr₂FeNbO_6-δ ceramic in the temperature range of 4–300 K. The observation of an asymmetric doublet in the Mössbauer spectra and the literature data on the magnetic susceptibility indicated the presence of two magnetic subsystems in Sr₂FeNbO_6-δ with antiferromagnetic exchange interactions. Based on the analysis of the temperature dependence of the specific heat capacity, we determined the Debye and Einstein temperatures. Full article

(This article belongs to the Section Magnetic Materials)

► Show Figures

Figure 1

17 pages, 9708 KiB

Open AccessArticle

Temperature Dependence of Magnetization Dynamics in Co/IrMn and Co/FeMn Exchange Biased Structures

by Irina O. Dzhun, Andrey V. Gerasimenko, Alexander A. Ezhov, Stanislav I. Bezzubov, Valeria V. Rodionova, Christina A. Gritsenko and Nikolai G. Chechenin

Magnetochemistry 2023, 9(10), 218; https://doi.org/10.3390/magnetochemistry9100218 - 08 Oct 2023

Viewed by 1672

Abstract

Thin film ferromagnet/antiferromagnet (F/AF) exchange biased structures that are widely used in GMR spin valves are considered nowadays as promising systems for antiferromagnetic spintronic and spin-orbitronic devices. Here, the temperature dependences of magnetization dynamics in Co/IrMn and Co/FeMn F/AF structures are investigated using [...] Read more.

Thin film ferromagnet/antiferromagnet (F/AF) exchange biased structures that are widely used in GMR spin valves are considered nowadays as promising systems for antiferromagnetic spintronic and spin-orbitronic devices. Here, the temperature dependences of magnetization dynamics in Co/IrMn and Co/FeMn F/AF structures are investigated using ferromagnetic resonance (FMR) in comparison to a free Co layer. A strong additional decrease in the resonance field was observed in Co/IrMn with a temperature decrease attributed to the rotatable anisotropy increase, which almost vanished at room temperature. In contrast to Co/IrMn, the contribution of the rotatable anisotropy in Co/FeMn is much weaker, even though it exists at RT, it is negative, and slightly varies with the temperature and resonance field shift in Co/FeMn. This is mainly due to unidirectional exchange anisotropy. FMR linewidth for the free Co layer increases with decreasing temperature and is accompanied with a slow relaxation process, while the additional contribution to FMR line broadening in Co/IrMn and Co/FeMn structures is correlated with variation in the exchange anisotropy. The observed results are discussed based on structural and surface morphology and magnetization reversal characterization using X-ray diffraction, atomic force microscopy, and vibrating sample magnetometry data. Full article

(This article belongs to the Section Magnetic Materials)

► Show Figures

Figure 1

13 pages, 3021 KiB

Open AccessArticle

In One Fell Sweep: Modeling Exchange, Hyperfine and Dipolar Interactions from EPR Spectra of Copper(II) Spin Triangles

by Athanassios K. Boudalis

Magnetochemistry 2023, 9(10), 217; https://doi.org/10.3390/magnetochemistry9100217 - 06 Oct 2023

Viewed by 1228

Abstract

The weak intramolecular magnetic interactions within a series of Cu^II₃ complexes based on the trinucleating 2,4,6-tris(di-2-pyridylamino)-1,3,5-triazine (dipyatriz) ligand were investigated via Electron Paramagnetic Resonance (EPR) spectroscopy. X- and Q-band EPR spectroscopy in powders and frozen solutions were recorded and the Q-band [...] Read more.

The weak intramolecular magnetic interactions within a series of Cu^II₃ complexes based on the trinucleating 2,4,6-tris(di-2-pyridylamino)-1,3,5-triazine (dipyatriz) ligand were investigated via Electron Paramagnetic Resonance (EPR) spectroscopy. X- and Q-band EPR spectroscopy in powders and frozen solutions were recorded and the Q-band spectra were interpreted by a multispin Hamiltonian model comprising exchange, dipolar and hyperfine interactions. The described methodology is suitable for the elucidation of weak intramolecular interactions which are not amenable to analysis via magnetic susceptibility studies. Full article

(This article belongs to the Special Issue Selected Papers from Young Investigators in Magnetic Resonances)

► Show Figures

Figure 1

18 pages, 4029 KiB

Open AccessArticle

Design and Numerical Study of Magnetic Energy Storage in Toroidal Superconducting Magnets Made of YBCO and BSCCO

by Radu Jubleanu and Dumitru Cazacu

Magnetochemistry 2023, 9(10), 216; https://doi.org/10.3390/magnetochemistry9100216 - 01 Oct 2023

Viewed by 1807

Abstract

The superconducting magnet energy storage (SMES) has become an increasingly popular device with the development of renewable energy sources. The power fluctuations they produce in energy systems must be compensated with the help of storage devices. A toroidal SMES magnet with large capacity [...] Read more.

The superconducting magnet energy storage (SMES) has become an increasingly popular device with the development of renewable energy sources. The power fluctuations they produce in energy systems must be compensated with the help of storage devices. A toroidal SMES magnet with large capacity is a tendency for storage energy because it has great energy density and low stray field. A key component in the creation of these superconducting magnets is the material from which they are made. The present work describes a comparative numerical analysis with finite element method, of energy storage in a toroidal modular superconducting coil using two types of superconducting material with different properties bismuth strontium calcium copper oxide (BSCCO) and yttrium barium copper oxide (YBCO). Regarding the design of the modular torus, it was obtained that for a 1.25 times increase of the critical current for the BSCCO superconducting material compared with YBCO, the dimensions of the BSCCO torus were reduced by 7% considering the same stored energy. Also, following a numerical parametric analysis, it resulted that, in order to maximize the amount of energy stored, the thickness of the torus modules must be as small as possible, without exceeding the critical current. Another numerical analysis showed that the energy stored is maximum when the major radius of the torus is minimum, i.e., for a torus as compact as possible. Full article

(This article belongs to the Special Issue Advances in Superconducting Magnetic Energy Storage (SMES): From Materials to Renewable Energy Applications)

► Show Figures

Figure 1

13 pages, 4431 KiB

Open AccessArticle

Investigation of Ferrofluid Sessile Droplet Tensile Deformation in a Uniform Magnetic Field

by Gui-Ping Zhu, Shi-Hua Wu, Shu-Ze Zheng, Lai Li and Nam-Trung Nguyen

Magnetochemistry 2023, 9(10), 215; https://doi.org/10.3390/magnetochemistry9100215 - 30 Sep 2023

Viewed by 1046

Abstract

A significant growth of research on digital microfluidics has been achieved over the past several decades, and the field is still attracting increasing attention for fulfilling relevant mechanisms and potential applications. Numerous studies have been devoted to actively manipulating droplets in a variety [...] Read more.

A significant growth of research on digital microfluidics has been achieved over the past several decades, and the field is still attracting increasing attention for fulfilling relevant mechanisms and potential applications. Numerous studies have been devoted to actively manipulating droplets in a variety of fundamental and applicational scenarios. In this work, the deformation of ferromagnetic fluid droplets is studied under an external uniform magnetic field. The droplets are precisely dispersed on the bottom surface of a container assembled with polymer methacrylate (PMMA) plates. Mineral oil is applied instead of air as the surrounding medium for easy stretching and preventing water solvent evaporation in ferrofluid. The design and processing of the container are firstly carried out to observe the shape and characterize the wettability of the droplets in the immiscible mineral oil medium. Furthermore, the droplets’ deformation and the working mechanism are given under the action of the horizontal uniform magnetic field. At different magnetic field intensities, the droplet is stretched in the horizontal direction parallel to the applied field. Due to volume conservation, the dimension in the height reduces correspondingly. With the coupling effect of magnetic force, viscous force and interfacial tension, the contact angle first increases with the magnetic field and then basically remains unchanged upon magnetization saturation. Consistent with the experimental results, the numerical method clearly reveals the field coupling mechanism and the nonlinear deformation of the sessile droplet. Full article

(This article belongs to the Special Issue Ferrofluids - Electromagnetic Properties and Applications)

► Show Figures

Figure 1

13 pages, 2819 KiB

Open AccessArticle

Equivalent Noise Analysis and Modeling for a Magnetic Tunnel Junction Magnetometer with In Situ Magnetic Feedback

by Aiyu Dou, Ru Bai, Yucheng Sun, Jiakun Tu, Chuanjia Kou, Xin Xie and Zhenghong Qian

Magnetochemistry 2023, 9(10), 214; https://doi.org/10.3390/magnetochemistry9100214 - 29 Sep 2023

Cited by 1 | Viewed by 1192

Abstract

Magnetic tunnel junction (MTJ) sensors have been one of the excellent candidates for magnetic field detection due to their high sensitivity and compact size. In this paper, we design a magnetometer with in situ magnetic feedback consisting of an MTJ sensor. To analyze [...] Read more.

Magnetic tunnel junction (MTJ) sensors have been one of the excellent candidates for magnetic field detection due to their high sensitivity and compact size. In this paper, we design a magnetometer with in situ magnetic feedback consisting of an MTJ sensor. To analyze and evaluate the detectivity of the MTJ magnetometer, a noise model of the MTJ sensor in the magnetometer without magnetic feedback is first developed. Then, the noise model of the MTJ magnetometer with in situ magnetic feedback is also established, including the noises of the MTJ sensor and the signal conditioning circuit, as well as the feedback circuit. The equivalent noise model of the MTJ magnetometer with in situ magnetic feedback is evaluated through nonlinear fitting for the noise voltage spectrum. Although the noise generated by the MTJ sensor is much greater than that of the signal conditioning circuit, the noise introduced by the feedback coils into the MTJ sensor is slightly more than twice that generated by the MTJ sensor itself. The measurement results show that the detectivity of the MTJ magnetometer with in situ magnetic feedback reaches 526 pT/Hz^1/2 at 10 Hz. The equivalent noise analysis method presented in this paper is suitable for the detectivity analysis of magnetometers with magnetic feedback. Full article

(This article belongs to the Special Issue New Trends in Spintronic Materials and Devices)

► Show Figures

Figure 1

17 pages, 25998 KiB

Open AccessEditor’s ChoiceArticle

Polymer-Assisted Synthesis, Structure and Magnetic Properties of Bimetallic FeCo- and FeNi/N-Doped Carbon Nanocomposites

by Gulsara D. Kugabaeva, Kamila A. Kydralieva, Lyubov S. Bondarenko, Rose K. Baimuratova, Dmitry Yu. Karpenkov, Ekaterina A. Golovkova, Pavel N. Degtyarenko, Nina D. Golubeva, Igor E. Uflyand and Gulzhian I. Dzhardimalieva

Magnetochemistry 2023, 9(10), 213; https://doi.org/10.3390/magnetochemistry9100213 - 27 Sep 2023

Cited by 1 | Viewed by 1204

Abstract

Bimetallic FeCo and FeNi nanoparticles attract much attention due to their promising magnetic properties and a wide range of practical applications as recording and storage media, catalytic systems in fuel cells, supercapacitors, lithium batteries, etc. In this paper, we propose an original approach [...] Read more.

Bimetallic FeCo and FeNi nanoparticles attract much attention due to their promising magnetic properties and a wide range of practical applications as recording and storage media, catalytic systems in fuel cells, supercapacitors, lithium batteries, etc. In this paper, we propose an original approach to the preparation of FeCo- and FeNi/N-doped carbon nanocomposites by means of a coupled process of frontal polymerization and thermolysis of molecular co-crystallized acrylamide complexes. The phase composition, structure, and microstructure of the resulting nanocomposites are studied using XRD, IR spectroscopy, elemental and thermal analysis, and electron microscopy data. The main magnetic characteristics of the synthesized nanocomposites, including the field dependences and the ZFC-FC curves peculiarities, are studied. It is shown that the obtained FeCo/N-C nanocomposites exhibit exchange bias behavior at low temperatures. In turn, FeNi/N-C nanocomposites are ferromagnetically ordered. Full article

(This article belongs to the Section Magnetic Nanospecies)

► Show Figures

Figure 1

18 pages, 8362 KiB

Open AccessArticle

A Study of the Structure and Physicochemical Properties of the Mixed Basicity Iron Ore Sinter

by Andrey N. Dmitriev, Elena A. Vyaznikova, Galina Yu. Vitkina and Antonina I. Karlina

Magnetochemistry 2023, 9(10), 212; https://doi.org/10.3390/magnetochemistry9100212 - 22 Sep 2023

Cited by 1 | Viewed by 904

Abstract

To study the influence of sinter basicity on the microstructure, phase composition, and physicochemical and metallurgical properties, samples of agglomerates with different basicities were sintered and investigated. A comprehensive study of the structure, composition, chemical, and metallurgical properties of the sinter was conducted, [...] Read more.

To study the influence of sinter basicity on the microstructure, phase composition, and physicochemical and metallurgical properties, samples of agglomerates with different basicities were sintered and investigated. A comprehensive study of the structure, composition, chemical, and metallurgical properties of the sinter was conducted, and the optimum values for these properties were determined. The results of the mineralogical transformations that occurred during the sintering process are also presented. The magnetite contained in the concentrate partially dissolves in the silicate component and flux during agglomeration, forming a complex silicate SFCA with the general formula M₁₄O₂₀ (M–Ca, Si, Al, and Mg), which is the binder of the ore phases of the agglomerate. The proportion of ferrosilicates of calcium and aluminum in the sinter depends on the basicity of the sinter charge, and the morphology of the SFCA phase depends on the cooling rate of the sinter. The more CaO in the sinter charge, the more SFCA phase is formed in the sinter, and slow cooling results in the growth of large lamellar and dendritic SFCA phases. Full article

(This article belongs to the Special Issue Magnetism: Energy, Recycling, Novel Materials)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Magnetochemistry, Volume 9, Issue 10 (October 2023) – 11 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI