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Magnetochemistry, Volume 7, Issue 4 (April 2021) – 11 articles

Cover Story (view full-size image): The origin of thermotherapy is lost in the mists of time. Today, a technological challenge is to achieve local control of a tumor. In this sense, several concepts have been proposed for the improvement of hyperthermia mediated by magnetic nanoparticles, in which the heat derived from hysteresis is key for its effective clinical translation. For example, chemically synthesized exchange-coupled ferrites are said to provide efficiencies in excess of 10 kW/g. Such statements challenge us to develop a more precise understanding of the interplay between magnetism and geometry. This work compares core–shell Fe/Fe3O4 nanoparticles of cubic and spherical shapes developed using physical vapor deposition techniques. From the information available, it is probably fair to conclude that heating efficiency values reaching around 2 kW/g seem feasible, but anything above should be judged carefully. View this paper
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13 pages, 3292 KiB  
Article
Long-Term Converse Magnetoelectric Response of Actuated 1-3 Multiferroic Composite Structures
by Ryan Stampfli, Nha Uyen Huynh and George Youssef
Magnetochemistry 2021, 7(4), 55; https://doi.org/10.3390/magnetochemistry7040055 - 20 Apr 2021
Cited by 4 | Viewed by 1715
Abstract
Multiferroic composite materials operating under the principle of strain mediation across the interfaces separating different material boundaries address many limitations of single-phase magnetoelectric materials. Although significant research has been conducted to explore their responses relating to the topography and directionality of material polarization [...] Read more.
Multiferroic composite materials operating under the principle of strain mediation across the interfaces separating different material boundaries address many limitations of single-phase magnetoelectric materials. Although significant research has been conducted to explore their responses relating to the topography and directionality of material polarization and magnetic loading, there remain unanswered questions regarding the long-term performance of these multiferroic structures. In this study, a multiferroic composite structure consisting of an inner Terfenol-D magnetostrictive cylinder and an outer lead zirconate titanate (PZT) piezoelectric cylinder was investigated. The composite was loaded over a 45-day period with an AC electric field (20 kV/m) at a near-resonant frequency (32.5 kHz) and a simultaneously applied DC magnetic field of 500 Oe. The long-term magnetoelectric and thermal responses were continuously monitored, and an extensive micrographic analysis of pretest and post-test states was performed using scanning electron microscopy (SEM). The extended characterization revealed a significant degradation of ≈30–50% of the magnetoelectric response, whereas SEM micrographs indicated a reduction in the bonding interface quality. The increase in temperature at the onset of loading was associated with the induced oscillatory piezoelectric strain and accounted for 28% of the strain energy loss over nearly one hour. Full article
(This article belongs to the Special Issue Multiferroic Materials 2021)
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16 pages, 4385 KiB  
Article
New Radical Cation Salts Based on BDH-TTP Donor: Two Stable Molecular Metals with a Magnetic [ReF6]2− Anion and a Semiconductor with a [ReO4] Anion
by Nataliya D. Kushch, Gennady V. Shilov, Lev I. Buravov, Eduard B. Yagubskii, Vladimir N. Zverev, Enric Canadell and Jun-ichi Yamada
Magnetochemistry 2021, 7(4), 54; https://doi.org/10.3390/magnetochemistry7040054 - 20 Apr 2021
Cited by 2 | Viewed by 2202
Abstract
Three radical cation salts of BDH-TTP with the paramagnetic [ReF6]2− and diamagnetic [ReO4] anions have been synthesized: κ-(BDH-TTP)4ReF6 (1), κ-(BDH-TTP)4ReF6·4.8H2O (2) and pseudo-κ″-(BDH-TTP)3 [...] Read more.
Three radical cation salts of BDH-TTP with the paramagnetic [ReF6]2− and diamagnetic [ReO4] anions have been synthesized: κ-(BDH-TTP)4ReF6 (1), κ-(BDH-TTP)4ReF6·4.8H2O (2) and pseudo-κ″-(BDH-TTP)3(ReO4)2 (3). The crystal and band structures, as well as the conducting properties of the salts, have been studied. The structures of the three salts are layered and characterized by alternating κ-(1, 2) and κ″-(3) type organic radical cation layers with inorganic anion sheets. Similar to other κ-salts, the conducting layers in the crystals of 1 and 2 are formed by BDH-TTP dimers. The partial population of positions of Re atoms and disorder in the anionic layers of 13 are their distinctive features. Compounds 1 and 2 show the metallic character of conductivity down to low temperatures, while 3 is a semiconductor. The ac susceptibility of crystals 1 was investigated in order to test the possible slow relaxation of magnetization associated with the [ReF6]2− anion. Full article
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19 pages, 13993 KiB  
Article
Tuning of Structural, Dielectric, and Electronic Properties of Cu Doped Co–Zn Ferrite Nanoparticles for Multilayer Inductor Chip Applications
by Muhammad Hadi, Khalid Mujasam Batoo, Ankush Chauhan, Omar M. Aldossary, Ritesh Verma and Yujie Yang
Magnetochemistry 2021, 7(4), 53; https://doi.org/10.3390/magnetochemistry7040053 - 14 Apr 2021
Cited by 83 | Viewed by 4196
Abstract
Herein, we report the synthesis of nanoparticles and doping of Cu-doped Co–Zn ferrites using the auto-combustion sol–gel synthesis technique. X-ray diffraction studies confirmed the single-phase structure of the samples with space group Fd3m and crystallite size in the range of 20.57–32.69 [...] Read more.
Herein, we report the synthesis of nanoparticles and doping of Cu-doped Co–Zn ferrites using the auto-combustion sol–gel synthesis technique. X-ray diffraction studies confirmed the single-phase structure of the samples with space group Fd3m and crystallite size in the range of 20.57–32.69 nm. Transmission electron microscopy micrographs and selected area electron diffraction patterns confirmed the polycrystalline nature of the ferrite nanoparticles. Energy-dispersive X-ray spectroscopy revealed the elemental composition in the absence of any impurity phases. Fourier-transform infrared studies showed the presence of two prominent peaks at approximately 420 cm−1 and 580 cm−1, showing metal–oxygen stretching and the formation of ferrite composite. X-ray photoelectron spectroscopy was employed to determine the oxidation states of Fe, Co, Zn, and Cu and O vacancies based on which cationic distributions at tetrahedral and octahedral sites are proposed. Dielectric spectroscopy showed that the samples exhibit Maxwell–Wagner interfacial polarization, which decreases as the frequency of the applied field increases. The dielectric loss of the samples was less than 1, confirming that the samples can be used for the fabrication of multilayer inductor chips. The ac conductivity of the samples increased with increasing doping and with frequency, and this has been explained by the hopping model. The hysteresis loops revealed that coercivity decreases slightly with doping, while the highest saturation magnetization of 55.61 emu/g was obtained when x = 0.1. The magnetic anisotropic constant was found to be less than 0.5, which suggests that the samples exhibit uniaxial anisotropy rather than cubic anisotropy. The squareness ratio indicates that the samples are useful in high-frequency applications. Full article
(This article belongs to the Special Issue Advances in Fine Particle Magnetism and Bio-Magnetic Materials)
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12 pages, 3424 KiB  
Article
AC Susceptibility Studies under DC Fields in Superspinglass Nanomaghemite-Multiwall Carbon Nanotube Hybrid
by Juan A. Ramos-Guivar, F. Jochen Litterst and Edson C. Passamani
Magnetochemistry 2021, 7(4), 52; https://doi.org/10.3390/magnetochemistry7040052 - 12 Apr 2021
Cited by 5 | Viewed by 1994
Abstract
Magnetic properties of maghemite (γ-Fe2O3) nanoparticles grown on activated multiwall carbon nanotubes have been studied by alternating current (AC) magnetic susceptibility experiments performed under different temperatures, frequencies, and applied magnetic fields. Transmission electron images have suggested that the γ-Fe [...] Read more.
Magnetic properties of maghemite (γ-Fe2O3) nanoparticles grown on activated multiwall carbon nanotubes have been studied by alternating current (AC) magnetic susceptibility experiments performed under different temperatures, frequencies, and applied magnetic fields. Transmission electron images have suggested that the γ-Fe2O3 nanoparticles are not isolated and have an average size of 9 nm, but with a relatively broad size distribution. The activation energies of these 9 nm γ-Fe2O3 nanoparticles, determined from the generalized Vogel–Fulcher relation, are reduced upon increasing the direct current (DC) field magnitude. The large activation energy values have indicated the formation of a superspinglass state in the γ-Fe2O3 nanoparticle ensemble, which were not observed for pure γ-Fe2O3 nanoparticles, concluding that the multiwall carbon nanotubes favored the appearance of highly concentrated magnetic regions and hence the formation of superspinglass state. Magnetic relaxation studies, using Argand diagrams recorded for DC probe fields (<20 kOe) below the magnetic blocking temperature at 100 and 10 K, have revealed the presence of more than one relaxation process. The behavior of the ensemble of γ-Fe2O3 nanoparticles can be related to the superspinglass state and is also supported by Almeida–Thouless plots. Full article
(This article belongs to the Special Issue Magnetic Properties of Nanomaterials)
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14 pages, 2641 KiB  
Article
Magneto-Erythrocyte Membrane Vesicles’ Superior T2 MRI Contrast Agents to Magneto-Liposomes
by Nina Kostevšek, Patricija Miklavc, Matic Kisovec, Marjetka Podobnik, Wafa Al-Jamal and Igor Serša
Magnetochemistry 2021, 7(4), 51; https://doi.org/10.3390/magnetochemistry7040051 - 11 Apr 2021
Cited by 2 | Viewed by 2398
Abstract
Despite their high potential, most of the clinically approved iron oxide (IO)-based contrast agents for magnetic resonance imaging (MRI) have been withdrawn from the market either due to safety issues or lack of sales. To address this challenge, erythrocyte membranes have been used [...] Read more.
Despite their high potential, most of the clinically approved iron oxide (IO)-based contrast agents for magnetic resonance imaging (MRI) have been withdrawn from the market either due to safety issues or lack of sales. To address this challenge, erythrocyte membranes have been used to prepare IO-based T2 contrast agents with superior MRI properties and higher safety margin. A simple formulation procedure has been proposed, and the nanostructures’ morphology and physicochemical properties have been evaluated. We compared their performance in terms of contrast ability in MRI to the more clinically established magneto-liposomes and non-encapsulated nanoparticles (NPs). The encapsulation of 5-nm iron oxide nanoparticles (IO NPs) in the liposomes and erythrocyte membrane vesicles (EMVs) led to a significant improvement in their r2 relaxivity. r2 values increased to r2 = 188 ± 2 mM−1s−1 for magneto-liposomes and r2 = 269 ± 3 mM−1s−1 for magneto-erythrocyte membranes, compared to “free” IO NPs with (r2 = 12 ± 1 mM−1 s−1), measured at a 9.4 T MRI scanner. The superiority of magneto-erythrocyte membranes in terms of MRI contrast efficacy is clearly shown on T2-weighted MR images. Our study revealed the hemocompatibility of the developed contrast agents in the MRI-relevant concentration range. Full article
(This article belongs to the Special Issue Biomedical Application of Magnetic Nanoparticles in 2022)
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16 pages, 2391 KiB  
Article
Coexistence of Spin Canting and Metamagnetism in a One-Dimensional Mn(II) Compound Bridged by Alternating Double End-to-End and Double End-On Azido Ligands and the Analog Co(II) Compound
by Nesrine Benamara, Zouaoui Setifi, Chen-I Yang, Sylvain Bernès, David K. Geiger, Güneş Süheyla Kürkçüoğlu, Fatima Setifi and Jan Reedijk
Magnetochemistry 2021, 7(4), 50; https://doi.org/10.3390/magnetochemistry7040050 - 6 Apr 2021
Cited by 7 | Viewed by 3036
Abstract
Two new compounds of general formula [M(N3)2(dmbpy)] in which dmbpy = 5,5′-dimethyl-2,2′-bipyridine, and M = Mn(II) or Co(II), have been solvothermally synthesized and characterized structurally and magnetically. The structures consist of zig-zag polymeric chains with alternating bis-µ(azide-N1)2M [...] Read more.
Two new compounds of general formula [M(N3)2(dmbpy)] in which dmbpy = 5,5′-dimethyl-2,2′-bipyridine, and M = Mn(II) or Co(II), have been solvothermally synthesized and characterized structurally and magnetically. The structures consist of zig-zag polymeric chains with alternating bis-µ(azide-N1)2M and bis-µ(azide-N1,N3)2M units in which the cis-octahedrally based coordination geometry is completed by the N,N’-chelating ligand dmbpy. The molecular structures are basically the same for each metal. The Mn(II) compound has a slightly different packing mode compared to the Co(II) compound, resulting from their different space groups. Interestingly, relatively weak interchain interactions are present in both compounds and this originates from π–π stacking between the dmbpy rings. The magnetic properties of both compounds have been investigated down to 2 K. The measurements indicate that the manganese compound shows spin-canted antiferromagnetic ordering with a Néel temperature of TN = 3.4 K and further, a field-induced magnetic transition of metamagnetism at temperatures below the TN. This finding affords the first example of an 1D Mn(II) compound with alternating double end-on (EO) and double end-to-end (EE) azido-bridged ligands, showing the coexistence of spin canting and metamagnetism. The cobalt compound shows a weak ferromagnetism resulting from a spin-canted antiferromagnetism and long-range magnetic ordering with a critical temperature, TC = 16.2 K. Full article
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14 pages, 2221 KiB  
Article
Finding the Limits of Magnetic Hyperthermia on Core-Shell Nanoparticles Fabricated by Physical Vapor Methods
by Carlos Martinez-Boubeta, Konstantinos Simeonidis, Judit Oró, Antonios Makridis, David Serantes and Lluis Balcells
Magnetochemistry 2021, 7(4), 49; https://doi.org/10.3390/magnetochemistry7040049 - 2 Apr 2021
Cited by 10 | Viewed by 2906
Abstract
Magnetic nanoparticles can generate heat when exposed to an alternating magnetic field. Their heating efficacy is governed by their magnetic properties that are in turn determined by their composition, size and morphology. Thus far, iron oxides (e.g., magnetite, Fe3O4) [...] Read more.
Magnetic nanoparticles can generate heat when exposed to an alternating magnetic field. Their heating efficacy is governed by their magnetic properties that are in turn determined by their composition, size and morphology. Thus far, iron oxides (e.g., magnetite, Fe3O4) have been the most popular materials in use, though recently bimagnetic core-shell structures are gaining ground. Herein we present a study on the effect of particle morphology on heating efficiency. More specifically, we use zero waste impact methods for the synthesis of metal/metal oxide Fe/Fe3O4 nanoparticles in both spherical and cubic shapes, which present an interesting venue for understanding how spin coupling across interfaces and also finite size effects may influence the magnetic response. We show that these particles can generate sufficient heat (hundreds of watts per gram) to drive hyperthermia applications, whereas faceted nanoparticles demonstrate superior heating capabilities than spherical nanoparticles of similar size. Full article
(This article belongs to the Special Issue Advances in Multifunctional Magnetic Nanomaterials)
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4 pages, 397 KiB  
Editorial
Feature Papers in Magnetochemistry
by Carlos J. Gómez-García
Magnetochemistry 2021, 7(4), 48; https://doi.org/10.3390/magnetochemistry7040048 - 2 Apr 2021
Viewed by 1493
Abstract
When we launched the journal Magnetochemistry in 2015 we could not imagine such an enthusiastic response from the scientific community [...] Full article
(This article belongs to the Special Issue Feature Papers in Magnetochemistry)
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16 pages, 7742 KiB  
Article
Gd3+ Doped CoFe2O4 Nanoparticles for Targeted Drug Delivery and Magnetic Resonance Imaging
by Fatima Javed, Muhammad Asad Abbas, Muhammad Imran Asad, Naveed Ahmed, Nauman Naseer, Hassan Saleem, Abdelhamid Errachid, Noureddine Lebaz, Abdelhamid Elaissari and Nasir M. Ahmad
Magnetochemistry 2021, 7(4), 47; https://doi.org/10.3390/magnetochemistry7040047 - 30 Mar 2021
Cited by 17 | Viewed by 3204
Abstract
Nanoparticles of CoGdxFe2 − xO4 (x = 0%, 25%, 50%) synthesized via sol–gel auto combustion technique and encapsulated within a polymer (Eudragit E100) shell containing curcumin by single emulsion solvent evaporation technique were formulated in this study. [...] Read more.
Nanoparticles of CoGdxFe2 − xO4 (x = 0%, 25%, 50%) synthesized via sol–gel auto combustion technique and encapsulated within a polymer (Eudragit E100) shell containing curcumin by single emulsion solvent evaporation technique were formulated in this study. Testing of synthesized nanoparticles was carried out by using different characterization techniques, to investigate composition, crystallinity, size, morphology, surface charge, functional groups and magnetic properties of the samples. The increased hydrophilicity resulted in sustained drug release of 90.6% and 95% for E1(CoGd0.25Fe1.75O4) and E2(CoGd0.50Fe1.5O4), respectively, over a time span of 24 h. The relaxivities of the best-chosen samples were measured by using a 3T magnetic resonance imaging (MRI) machine, and a high r2/r1 ratio of 43.64 and 23.34 for composition E1(CoGd0.25Fe1.75O4) and E2(CoGd0.50Fe1.5O4) suggests their ability to work as a better T2 contrast agent. Thus, these novel synthesized nanostructures cannot only enable MRI diagnosis but also targeted drug delivery. Full article
(This article belongs to the Special Issue Biomedical Application of Magnetic Nanoparticles in 2022)
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22 pages, 6117 KiB  
Article
Oscillatory Copper Deposition on Conical Iron Electrodes in a Nonuniform Magnetic Field
by Giovanni Marinaro, Mengyuan Huang, Gerd Mutschke, Xuegeng Yang and Kerstin Eckert
Magnetochemistry 2021, 7(4), 46; https://doi.org/10.3390/magnetochemistry7040046 - 28 Mar 2021
Cited by 5 | Viewed by 2346
Abstract
We report the effect of a magnetic field on the deposition of copper ions on a conically shaped iron probe. In our setup, the magnetic forces and buoyancy are the key factors influencing the electrolyte flow and the mass transfer. Without external current, [...] Read more.
We report the effect of a magnetic field on the deposition of copper ions on a conically shaped iron probe. In our setup, the magnetic forces and buoyancy are the key factors influencing the electrolyte flow and the mass transfer. Without external current, a spontaneous reduction of copper on the iron cone occurs, known as electroless deposition. Mach–Zehnder and differential interferometry indicate a variation in the concentration of copper ions near the cone. After an initial transient of about 60 s, temporal oscillations in the copper concentration are found under the effect of a magnetic field. In galvanostatic conditions, a similar oscillatory behavior of the concentration of the electrolyte is observed. Numerical simulations show that the oscillations are caused by the magnetic gradient, Lorentz force, and buoyancy force counteracting one another, and the oscillation frequency is estimated analytically based on this mechanism. Furthermore, we present a study on the oscillation frequency for both electroless and galvanostatic conditions with different current densities. The results of this study may stimulate future research aimed at the local control of the deposition rate and the realization of miniaturized, regularly structured deposits using magnetic fields. Full article
(This article belongs to the Special Issue Advances in Computational Electromagnetics)
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5 pages, 1161 KiB  
Article
Electric Field Control of Magnetic Properties by Means of Li+ Migration in FeRh Thin Film
by Gengfei Li, Yali Xie, Baomin Wang, Huali Yang and Run-Wei Li
Magnetochemistry 2021, 7(4), 45; https://doi.org/10.3390/magnetochemistry7040045 - 26 Mar 2021
Cited by 1 | Viewed by 1833
Abstract
Recently, the electric control of magnetism by means of ion migration has been proven to be effective with nonvolatility and low energy consumption. In this work, we investigated the control of the magnetic properties of FeRh films by means of Li+ migration [...] Read more.
Recently, the electric control of magnetism by means of ion migration has been proven to be effective with nonvolatility and low energy consumption. In this work, we investigated the control of the magnetic properties of FeRh films by means of Li+ migration in FeRh/MgO heterostructures. We found that the migration of Li+ could reduce the phase transition temperature by 2 K with an applied voltage of 1 V. Meanwhile, the voltage-dependent saturated magnetization exhibited a repetitive switching behavior from high to low magnetization values while the voltage was switched from 4 to −4 V, indicating that the migration of Li+ in the FeRh film can be reversible. This provides a means to control the magnetic properties of FeRh films. Full article
(This article belongs to the Special Issue Magnetic Materials, Thin Films and Nanostructures)
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