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Magnetochemistry, Volume 10, Issue 2 (February 2024) – 7 articles

Cover Story (view full-size image): We study the magnetic and entanglement properties of one-dimensional confined trimetric nickel(II) acetylacetonate by using Matrix Product States, in which we model the changes in the proximity of the molecular spins that result from being confined into a uni-axial arrangement, as it gives rise to the appearance of an intermolecular exchange interaction and the quenching of the intramolecular exchange. We find distinct signatures of the interaction topology of the molecules inside the single-walled carbon nanotubes (SWCNTs), reflected in the magnetism and entanglement plateaus of the resulting spin chains. These insights could provide versatile control strategies and valuable information about the interplay between topology and confinement in 1D-encapsulated single molecules. View this paper
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10 pages, 2123 KiB  
Article
Compatibility of LaFe13−x−yMnxSiyH1.6 and Eutectic Liquid GaInSn Alloy
by Jamieson Brechtl, Joseph Rendall, Mingkan Zhang, Michael R. Koehler, Kashif Nawaz and Ayyoub M. Momen
Magnetochemistry 2024, 10(2), 13; https://doi.org/10.3390/magnetochemistry10020013 - 12 Feb 2024
Viewed by 1430
Abstract
The heat transfer rate of magnetocaloric regenerators is a topic of extensive research and the cyclability of these regenerators is critical to the operation of systems with a high coefficient of performance (e.g., potentially >22, significantly higher than typical vapor compression cooling technologies). [...] Read more.
The heat transfer rate of magnetocaloric regenerators is a topic of extensive research and the cyclability of these regenerators is critical to the operation of systems with a high coefficient of performance (e.g., potentially >22, significantly higher than typical vapor compression cooling technologies). To enable a high operating frequency that will result in a high specific cooling power, the heat transfer fluid should have high thermal conductivity and lower specific heat, i.e., higher thermal diffusivity. Eutectic metal alloys possess these qualities, such as gallium–indium–tin (Galinstan), whose thermal diffusivity has been found to be approximately an order of magnitude higher than water. For this study, the effects of eutectic liquid Galinstan exposure on the phase stability of LaFe13−x−yMnxSiyH1.6 magnetocaloric powders in an active magnetic regenerator device were investigated. The powders were characterized before and after exposure to Galinstan using X-ray diffraction, in which the phases were determined using the Rietveld refinement technique and X-ray fluorescence. It was found that after Galinstan exposure, hydrogen containing phases were present in the powder, suggesting that the hydrogen was lost from the magnetocaloric phase. The magnetocaloric phase degradation indicates that the powder was incompatible with the Galinstan metal in an environment with moisture. Full article
(This article belongs to the Special Issue Advances in Functional Materials with Tunable Magnetic Properties)
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0 pages, 4352 KiB  
Article
Experimental Thermal Conductivity Studies of Agar-Based Aqueous Suspensions with Lignin Magnetic Nanocomposites
by Bishal Gautam, Saja M. Nabat Al-Ajrash, Mohammad Jahid Hasan, Abhishek Saini, Sarah J. Watzman, Esteban Ureña-Benavides and Erick S. Vasquez-Guardado
Magnetochemistry 2024, 10(2), 12; https://doi.org/10.3390/magnetochemistry10020012 - 10 Feb 2024
Viewed by 1145 | Correction
Abstract
Nanoparticle additives increase the thermal conductivity of conventional heat transfer fluids at low concentrations, which leads to improved heat transfer fluids and processes. This study investigates lignin-coated magnetic nanocomposites (lignin@Fe3O4) as a novel bio-based magnetic nanoparticle additive to enhance [...] Read more.
Nanoparticle additives increase the thermal conductivity of conventional heat transfer fluids at low concentrations, which leads to improved heat transfer fluids and processes. This study investigates lignin-coated magnetic nanocomposites (lignin@Fe3O4) as a novel bio-based magnetic nanoparticle additive to enhance the thermal conductivity of aqueous-based fluids. Kraft lignin was used to encapsulate the Fe3O4 nanoparticles to prevent agglomeration and oxidation of the magnetic nanoparticles. Lignin@Fe3O4 nanoparticles were prepared using a pH-driven co-precipitation method with a 3:1 lignin to magnetite ratio and characterized by X-ray diffraction, FT-IR, thermogravimetric analysis, and transmission electron microscopy. The magnetic properties were characterized using a vibrating sample magnetometer. Once fully characterized, lignin@Fe3O4 nanoparticles were dispersed in aqueous 0.1% w/v agar–water solutions at five different concentrations, from 0.001% w/v to 0.005% w/v. Thermal conductivity measurements were performed using the transient line heat source method at various temperatures. A maximum enhancement of 10% in thermal conductivity was achieved after adding 0.005% w/v lignin@Fe3O4 to the agar-based aqueous suspension at 45 °C. At room temperature (25 °C), the thermal conductivity of lignin@Fe3O4 and uncoated Fe3O4 agar-based suspensions was characterized at varying magnetic fields from 0 to 0.04 T, which were generated using a permanent magnet. For this analysis, the thermal conductivity of lignin magnetic nanosuspensions initially increased, showing a 5% maximum peak increase after applying a 0.02 T magnetic field, followed by a decreasing thermal conductivity at higher magnetic fields up to 0.04 T. This result is attributed to induced magnetic nanoparticle aggregation under external applied magnetic fields. Overall, this work demonstrates that lignin-coated Fe3O4 nanosuspension at low concentrations slightly increases the thermal conductivity of agar aqueous-based solutions, using a simple permanent magnet at room temperature or by adjusting temperature without any externally applied magnetic field. Full article
(This article belongs to the Section Applications of Magnetism and Magnetic Materials)
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12 pages, 3460 KiB  
Article
Optimal Selection for Redox Couples and Enhanced Performance through Magnetic Nanofluid Electrolyte in Solar Flow Batteries
by Zixing Gu, Ping Lu, Zihan Zhang, Qiang Ma, Huaneng Su and Qian Xu
Magnetochemistry 2024, 10(2), 11; https://doi.org/10.3390/magnetochemistry10020011 - 06 Feb 2024
Cited by 1 | Viewed by 1152
Abstract
The limited photoelectric conversion efficiency poses one of the critical constraints on commercializing solar flow batteries (SFBs). This study compares the chemical and photoelectrochemical properties of three commonly used redox couples. Additionally, magnetic Fe3O4 nanoparticles, for the first time, are [...] Read more.
The limited photoelectric conversion efficiency poses one of the critical constraints on commercializing solar flow batteries (SFBs). This study compares the chemical and photoelectrochemical properties of three commonly used redox couples. Additionally, magnetic Fe3O4 nanoparticles, for the first time, are introduced to optimize the electrolyte, and they are compared with the original electrolyte. Across different redox couples, the variations in semiconductor flat-band potentials and carrier concentrations result in changes in photoelectric current density. Notably, FeCl2/FeCl3 redox coupled with TiO2 photoelectrodes exhibits the highest photoelectric current density, reaching 75.7 µA cm−2. However, the trade-off of this electrolyte, i.e., providing high photocurrent while being unable to supply sufficient open-circuit voltage, imposes limitations on the practical application of SFBs. Alternatively, for TEMPO and 4-OH-TEMPO electrolytes, which can provide a higher open-circuit voltage, the electrochemical activity is enhanced, and the solution ohmic resistance is reduced by introducing magnetic nanoparticles to form a magnetic nanofluid. As a result, the photoanode’s photocurrent density increases by 36.6% and 17.0%, respectively, in the two electrolytes. The work reported here effectively addresses the current issue of low photocurrent density in SFBs and presents new optimization strategies for SFBs. Full article
(This article belongs to the Special Issue Feature Paper on Magnetic Nanospecies—Educational Aspects)
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13 pages, 2870 KiB  
Article
Low-Frequency Dynamic Magnetic Fields Decrease Cellular Uptake of Magnetic Nanoparticles
by Anna V. Ivanova, Nelly S. Chmelyuk, Aleksey A. Nikitin, Alexander G. Majouga, Vladimir P. Chekhonin and Maxim A. Abakumov
Magnetochemistry 2024, 10(2), 9; https://doi.org/10.3390/magnetochemistry10020009 - 01 Feb 2024
Viewed by 1165
Abstract
Magnetic nanoparticles have gained attention as a potential structure for therapy and diagnosing oncological diseases. The key property of the magnetic nanoparticles is the ability to respond to an external magnetic field. It is known that magnetofection causes an increase in the cellular [...] Read more.
Magnetic nanoparticles have gained attention as a potential structure for therapy and diagnosing oncological diseases. The key property of the magnetic nanoparticles is the ability to respond to an external magnetic field. It is known that magnetofection causes an increase in the cellular uptake of RNA and DNA in complexes with magnetic nanoparticles in the presence of a permanent magnetic field. However, the influence of a dynamic magnetic field on the internalization of MNPs is not clear. In this work, we propose the idea that applying external low-frequency dynamic magnetic fields may decrease the cellular uptake, such as macrophages and malignant neuroblastoma. Using fluorescence microscopy and atomic emission spectroscopy, we found that oscillating magnetic fields decreased the cellular uptake of magnetic nanoparticles compared to untreated cells by up to 46%. In SH-SY5Y tumor cells and macrophage RAW264.7 cells, the absolute values of Fe per cell differed by 0.10 pg/cell and 0.33 pg/cell between treated and untreated cells, respectively. These results can be applied in the control of the cellular uptake in different areas of biomedicine. Full article
(This article belongs to the Special Issue Advanced Magnetic Nanomaterial for Cancer Therapy and Diagnosis)
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6 pages, 181 KiB  
Editorial
Magnetic and Magnetoelectric Materials
by Devashibhai Adroja and Dmitry Filippov
Magnetochemistry 2024, 10(2), 8; https://doi.org/10.3390/magnetochemistry10020008 - 01 Feb 2024
Viewed by 1048
Abstract
Magnetic materials are an important class of materials for the development of technology as well as for our fundamental understanding of microscopic magnetic interactions [...] Full article
24 pages, 16841 KiB  
Article
On the Magnetization and Entanglement Plateaus in One-Dimensional Confined Molecular Magnets
by Javier I. Norambuena Leiva, Emilio A. Cortés Estay, Eric Suarez Morell and Juan M. Florez
Magnetochemistry 2024, 10(2), 10; https://doi.org/10.3390/magnetochemistry10020010 - 01 Feb 2024
Viewed by 1169
Abstract
One-dimensional (1D) magnetic systems offer rich phenomena in the quantum limit, proving more chemically accessible than zero-dimensional or higher-dimensional frameworks. Single-walled carbon nanotubes (SWCNT) have recently been used to encapsulate trimetric nickel(II) acetylacetonate [Nanoscale, 2019, 11, 10615–10621]. Here, we investigate the magnetization on [...] Read more.
One-dimensional (1D) magnetic systems offer rich phenomena in the quantum limit, proving more chemically accessible than zero-dimensional or higher-dimensional frameworks. Single-walled carbon nanotubes (SWCNT) have recently been used to encapsulate trimetric nickel(II) acetylacetonate [Nanoscale, 2019, 11, 10615–10621]. Here, we investigate the magnetization on spin chains based on nickel trimers by Matrix Product State (MPS) simulations. Our findings reveal plateaus in the exchange/magnetic-field phase diagram for three coupling configurations, showcasing effective dimeric and trimeric spin-ordering with similar or staggered entanglement across chains. These ordered states allow the qubit-like tuning of specific local magnetic moments, exhibiting disengagement or uniform coupling in entanglement plateaus. This behavior is consistent with the experimental transition from frustrated (3D) to non-frustrated (1D) molecules, corresponding to large and smaller SWCNT diameters. Our study offers insights into the potential of 1D-confined trimers for quantum computation, extending beyond the confinement of trimetric nickel-based molecules in one dimension. Full article
(This article belongs to the Special Issue Advances in Functional Materials with Tunable Magnetic Properties)
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16 pages, 2922 KiB  
Article
Experimental Investigations on the Ferromagnetic Resonance and Absorbing Properties of a Ferrofluid in the Microwave Range
by Iosif Malaescu, Catalin N. Marin and Paul C. Fannin
Magnetochemistry 2024, 10(2), 7; https://doi.org/10.3390/magnetochemistry10020007 - 26 Jan 2024
Viewed by 1343
Abstract
Measurements of complex magnetic permeability, μ(f,H) = μ′(f,H) − ″(f,H) and dielectric permittivity ε(f,H) = ε′(f,H) − [...] Read more.
Measurements of complex magnetic permeability, μ(f,H) = μ′(f,H) − ″(f,H) and dielectric permittivity ε(f,H) = ε′(f,H) − ″(f,H), in the frequency range, f of (0.4–7) GHz, and polarizing field, H of (0–135) kA/m, were performed, for a kerosene-based ferrofluid with magnetite nanoparticles. Based on these measurements, the phenomenon of ferromagnetic resonance was highlighted and some microwave propagation parameters of the ferrofluid were determined: the attenuation constant, α(f,H), and the reflection coefficient, R(f,H), at the air-material interface, at the normal incidence. Knowing these parameters we proposed a theoretical model establishing for the first time an equation that allows the calculation of the overall reflection coefficient, Rw(f,H), at the normal incidence of the wave, for a ferrofluid of thickness d, deposited on a totally reflective support, following multiple internal reflections of the electromagnetic wave in the material. The results show that by increasing both, H, and d, the parameter, Rw(f,H) presents a minimum that decreases from 0.90 (for d = 2 mm) to 0.64 (for d = 10 mm), at frequency f = 5 GHz, which indicates an increase in the absorption of the electromagnetic wave by the ferrofluid. The obtained results are useful in the study of some materials that could be used as electromagnetic absorbers in the microwave range, by the determination of the overall reflection coefficient, Rw(f,H), controlled both by the thickness, d, of the absorber and by the external applied field, H. Full article
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