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Magnetochemistry, Volume 7, Issue 11 (November 2021) – 11 articles

Cover Story (view full-size image): Utilizing a large perpendicular EB field as pinned layers has been the subject of intense attraction because of its potential in spintronic applications. However, typical AFM/FM systems indicate a limitation in attaining large EB fields (usually below 1 KOe). Thus, it seems that these cannot provide reasonable necessities for future spintronic applications. This experimental study shows that by replacing the commonly used AFM pinned layer with the ferrimagnet pinning layer, large PEE is generated by varying the Tb content of the Tb–Co layer. The developed FIM/FM films with great PEE show possibilities for pinned layers in spintronics and memory device applications. View this paper
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12 pages, 1826 KiB  
Article
Magnetic Behaviour of Perovskite Compositions Derived from BiFeO3
by Andrei N. Salak, João Pedro V. Cardoso, Joaquim M. Vieira, Vladimir V. Shvartsman, Dmitry D. Khalyavin, Elena L. Fertman, Alexey V. Fedorchenko, Anatoli V. Pushkarev, Yury V. Radyush, Nikolai M. Olekhnovich, Róbert Tarasenko, Alexander Feher and Erik Čižmár
Magnetochemistry 2021, 7(11), 151; https://doi.org/10.3390/magnetochemistry7110151 - 16 Nov 2021
Cited by 3 | Viewed by 2586
Abstract
The phase content and sequence, the crystal structure, and the magnetic properties of perovskite solid solutions of the (1−y)BiFeO3yBiZn0.5Ti0.5O3 series (0.05 ≤ y ≤ 0.90) synthesized under high pressure have been studied. [...] Read more.
The phase content and sequence, the crystal structure, and the magnetic properties of perovskite solid solutions of the (1−y)BiFeO3yBiZn0.5Ti0.5O3 series (0.05 ≤ y ≤ 0.90) synthesized under high pressure have been studied. Two perovskite phases, namely the rhombohedral R3c and the tetragonal P4mm, which correspond to the structural types of the end members, BiFeO3 and BiZn0.5Ti0.5O3, respectively, were revealed in the as-synthesized samples. The rhombohedral and the tetragonal phases were found to coexist in the compositional range of 0.30 ≤ y ≤ 0.90. Magnetic properties of the BiFe1−y[Zn0.5Ti0.5]yO3 ceramics with y < 0.30 were measured as a function of temperature. The obtained compositional variations of the normalized unit-cell volume and the Néel temperature of the BiFe1−y[Zn0.5Ti0.5]yO3 perovskites in the range of their rhombohedral phase were compared with the respective dependences for the BiFe1−yB3+yO3 perovskites (where B3+ = Ga, Co, Mn, Cr, and Sc). The role of the high-pressure synthesis in the formation of the antiferromagnetic states different from the modulated cycloidal one characteristic of the parent BiFeO3 is discussed. Full article
(This article belongs to the Special Issue Ferromagnetism)
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11 pages, 2197 KiB  
Article
Counterintuitive Single-Molecule Magnet Behaviour in Two Polymorphs of One-Dimensional Compounds Involving Chiral BINOL-Derived Bisphosphate Ligands
by Carlo Andrea Mattei, Bertrand Lefeuvre, Vincent Dorcet, Gilles Argouarch, Olivier Cador, Claudia Lalli and Fabrice Pointillart
Magnetochemistry 2021, 7(11), 150; https://doi.org/10.3390/magnetochemistry7110150 - 16 Nov 2021
Cited by 3 | Viewed by 2410
Abstract
The coordination reaction of the [Dy(hfac)3(H2O)2] units (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate) with the [8′-(Diphenoxylphosphinyl)[1,1′-binaphthalen]-8-yl]diphenoxylphosphine oxide ligand (L) followed by a crystallisation in a 1:3 CH2Cl2:n-hexane solvent mixture led to [...] Read more.
The coordination reaction of the [Dy(hfac)3(H2O)2] units (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate) with the [8′-(Diphenoxylphosphinyl)[1,1′-binaphthalen]-8-yl]diphenoxylphosphine oxide ligand (L) followed by a crystallisation in a 1:3 CH2Cl2:n-hexane solvent mixture led to the isolation of a new polymorph of formula [(Dy(hfac)3((S)-L))3]n (1). The X-ray structure on single crystal of 1 revealed the formation of a mono-dimensional coordination polymer with three crystallographically independent DyIII centres, which crystallised in the polar chiral P21 space group. Ac magnetic measurements highlighted single-molecule magnet behaviour under both zero and 1000 Oe applied magnetic field with magnetic relaxation through quantum tunneling of the magnetisation (QTM, zero field only) and Raman processes. Despite the three crystallographically independent DyIII centres adopting a distorted D4d coordination environment, a single slow magnetic relaxation contribution was observed at a slower rate than its previously studied [(Dy(hfac)3((S)-L))]n (2) polymorph. Full article
(This article belongs to the Special Issue Advances in Lanthanide Coordination Chemistry)
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13 pages, 1626 KiB  
Article
Role of Disordered Precursor in L10 Phase Formation in FePt-Based Nanocomposite Magnet
by Alina Daniela Crisan, Ioan Dan and Ovidiu Crisan
Magnetochemistry 2021, 7(11), 149; https://doi.org/10.3390/magnetochemistry7110149 - 14 Nov 2021
Cited by 2 | Viewed by 2251
Abstract
In order to prove the usefulness of having a structurally disordered precursor to the formation of FePt L10 phase and to facilitate the co-existence of exchange coupled hard and soft magnetic phases with optimized magnetic properties in various conditions of annealing, a [...] Read more.
In order to prove the usefulness of having a structurally disordered precursor to the formation of FePt L10 phase and to facilitate the co-existence of exchange coupled hard and soft magnetic phases with optimized magnetic properties in various conditions of annealing, a Fe-Pt-Zr-B melt spun alloy has been synthesized and detailed structural and magnetic investigations have been undertaken to probe its phase evolution during annealing. The dynamics of formation of the hard magnetic L10 phase during the gradual disorder–order phase transformation has been monitored by using a complex combination of X-ray diffraction methods and 57Fe Mössbauer spectroscopy methods, over a wide range of annealing temperatures. Multiple phases co-existing in the annealed sample microstructures, observed in XRD, have been reconfirmed by the Mössbauer spectra analysis and, moreover, accurate quantitative data have been acquired in what concerns the relative abundance of each of the observed crystalline phases in every stage of annealing. It is shown that the formation of the hard magnetic phase, emerging from the chemically disordered precursor, is gradual and occurs via complex mechanisms, involving the presence of a disordered Fe-Zr-B-rich intergranular region which contributes to an increase in the abundance of the L10 phase for higher annealing temperatures. Magnetic measurements have confirmed the good performances of these alloys in terms of coercivity and remanence. These results contribute to the development of these alloys as the next generation of rare earth, free permanent magnets. Full article
(This article belongs to the Special Issue Magnetic Materials, Thin Films and Nanostructures)
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10 pages, 2446 KiB  
Article
Predicting Pt-195 NMR Chemical Shift and 1J(195Pt-31P) Coupling Constant for Pt(0) Complexes Using the NMR-DKH Basis Sets
by Joyce H. C. e Silva, Hélio F. Dos Santos and Diego F. S. Paschoal
Magnetochemistry 2021, 7(11), 148; https://doi.org/10.3390/magnetochemistry7110148 - 12 Nov 2021
Cited by 4 | Viewed by 2606
Abstract
Pt(0) complexes have been widely used as catalysts for important reactions, such as the hydrosilylation of olefins. In this context, nuclear magnetic resonance (NMR) spectroscopy plays an important role in characterising of new structures and elucidating reaction mechanisms. In particular, the Pt-195 NMR [...] Read more.
Pt(0) complexes have been widely used as catalysts for important reactions, such as the hydrosilylation of olefins. In this context, nuclear magnetic resonance (NMR) spectroscopy plays an important role in characterising of new structures and elucidating reaction mechanisms. In particular, the Pt-195 NMR is fundamental, as it is very sensitive to the ligand type and the oxidation state of the metal. In the present study, quantum mechanics computational schemes are proposed for the theoretical prediction of the Pt-195 NMR chemical shift and 1J(195Pt–31P) in Pt(0) complexes. The protocols were constructed using the B3LYP/LANL2DZ/def2-SVP/IEF-PCM(UFF) level for geometry optimization and the GIAO-PBE/NMR-DKH/IEF-PCM(UFF) level for NMR calculation. The NMR fundamental quantities were then scaled by empirical procedures using linear correlations. For a set of 30 Pt(0) complexes, the results showed a mean absolute deviation (MAD) and mean relative deviation (MRD) of only 107 ppm and 2.3%, respectively, for the Pt-195 NMR chemical shift. When the coupling constant is taken into account, the MAD and MRD for a set of 33 coupling constants in 26 Pt(0) complexes were of 127 Hz and 3.3%, respectively. In addition, the models were validated for a group of 17 Pt(0) complexes not included in the original group that had MAD/MRD of 92 ppm/1.7% for the Pt-195 NMR chemical shift and 146 Hz/3.6% for the 1J(195Pt–31P). Full article
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8 pages, 925 KiB  
Article
Revisiting the Potential Functionality of the MagR Protein
by Alexander Pekarsky, Herwig Michor and Oliver Spadiut
Magnetochemistry 2021, 7(11), 147; https://doi.org/10.3390/magnetochemistry7110147 - 11 Nov 2021
Viewed by 2752
Abstract
Recent findings have sparked great interest in the putative magnetic receptor protein MagR. However, in vivo experiments have revealed no magnetic moment of MagR at room temperature. Nevertheless, the interaction of MagR and MagR fusion proteins with silica-coated magnetite beads have proven useful [...] Read more.
Recent findings have sparked great interest in the putative magnetic receptor protein MagR. However, in vivo experiments have revealed no magnetic moment of MagR at room temperature. Nevertheless, the interaction of MagR and MagR fusion proteins with silica-coated magnetite beads have proven useful for protein purification. In this study, we recombinantly produced two different MagR proteins in Escherichia coli BL21(DE3) to (1) expand earlier protein purification studies, (2) test if MagR can magnetize whole E. coli cells once it is expressed to a high cytosolic, soluble titer, and (3) investigate the MagR-expressing E. coli cells’ magnetic properties at low temperatures. Our results show that MagR induces no measurable, permanent magnetic moment in cells at low temperatures, indicating no usability for cell magnetization. Furthermore, we show the limited usability for magnetic bead-based protein purification, thus closing the current knowledge gap between theoretical considerations and empirical data on the MagR protein. Full article
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13 pages, 17805 KiB  
Article
Magnetic Properties of Bi-Magnetic Core/Shell Nanoparticles: The Case of Thin Shells
by Alexander Omelyanchik, Silvia Villa, Gurvinder Singh, Valeria Rodionova, Sara Laureti, Fabio Canepa and Davide Peddis
Magnetochemistry 2021, 7(11), 146; https://doi.org/10.3390/magnetochemistry7110146 - 8 Nov 2021
Cited by 4 | Viewed by 3413
Abstract
Bi-magnetic core/shell nanoparticles were synthesized by a two-step high-temperature decomposition method of metal acetylacetonate salts. Transmission electron microscopy confirmed the formation of an ultrathin shell (~0.6 nm) of NiO and NiFe2O4 around the magnetically hard 8 nm CoFe2O [...] Read more.
Bi-magnetic core/shell nanoparticles were synthesized by a two-step high-temperature decomposition method of metal acetylacetonate salts. Transmission electron microscopy confirmed the formation of an ultrathin shell (~0.6 nm) of NiO and NiFe2O4 around the magnetically hard 8 nm CoFe2O4 core nanoparticle. Magnetization measurements showed an increase in the coercivity of the single-phase CoFe2O4 seed nanoparticles from ~1.2 T to ~1.5 T and to ~2.0 T for CoFe2O4/NiFe2O4 and CoFe2O4/NiO, respectively. The NiFe2O4 shell also increases the magnetic volume of particles and the dipolar interparticle interactions. In contrast, the NiO shell prevents such interactions and keeps the magnetic volume almost unchanged. Full article
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34 pages, 5023 KiB  
Review
Green Synthesis of Metal and Metal Oxide Nanoparticles: Principles of Green Chemistry and Raw Materials
by Liubov Soltys, Ostap Olkhovyy, Tetiana Tatarchuk and Mu. Naushad
Magnetochemistry 2021, 7(11), 145; https://doi.org/10.3390/magnetochemistry7110145 - 31 Oct 2021
Cited by 71 | Viewed by 11858
Abstract
Increased request for metal and metal oxide nanoparticles nanoparticles has led to their large-scale production using high-energy methods with various toxic solvents. This cause environmental contamination, thus eco-friendly “green” synthesis methods has become necessary. An alternative way to synthesize metal nanoparticles includes using [...] Read more.
Increased request for metal and metal oxide nanoparticles nanoparticles has led to their large-scale production using high-energy methods with various toxic solvents. This cause environmental contamination, thus eco-friendly “green” synthesis methods has become necessary. An alternative way to synthesize metal nanoparticles includes using bioresources, such as plants and plant products, bacteria, fungi, yeast, algae, etc. “Green” synthesis has low toxicity, is safe for human health and environment compared to other methods, meaning it is the best approach for obtaining metal and metal oxide nanoparticles. This review reveals 12 principles of “green” chemistry and examples of biological components suitable for “green” synthesis, as well as modern scientific research of eco-friendly synthesis methods of magnetic and metal nanoparticles. Particularly, using extracts of green tea, fruits, roots, leaves, etc., to obtain Fe3O4 NPs. The various precursors as egg white (albumen), leaf and fruit extracts, etc., can be used for the „green” synthesis of spinel magnetic NPs. “Green” nanoparticles are being widely used as antimicrobials, photocatalysts and adsorbents. “Green” magnetic nanoparticles demonstrate low toxicity and high biocompatibility, which allows for their biomedical application, especially for targeted drug delivery, contrast imaging and magnetic hyperthermia applications. The synthesis of silver, gold, platinum and palladium nanoparticles using extracts from fungi, red algae, fruits, etc., has been described. Full article
(This article belongs to the Special Issue Advances in Magnetic Force Microscopy)
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27 pages, 10098 KiB  
Article
Feasibility Study of Cooling a Bulk Acoustic Wave Resonator by Nanoparticle Enhanced Phase Change Material
by Mohammad Yaghoub Abdollahzadeh Jamalabadi
Magnetochemistry 2021, 7(11), 144; https://doi.org/10.3390/magnetochemistry7110144 - 28 Oct 2021
Cited by 1 | Viewed by 2489
Abstract
In the current study, the coupling of a cooling problem with the electromagnetic resonance of a bulk acoustic wave (BAW) material is investigated. As well, a new cooling method by the addition of nanoparticles to a phase change material surrounding the BAW resonator [...] Read more.
In the current study, the coupling of a cooling problem with the electromagnetic resonance of a bulk acoustic wave (BAW) material is investigated. As well, a new cooling method by the addition of nanoparticles to a phase change material surrounding the BAW resonator is presented. To solve the governing equations of piezoelectric charge and momentum balance, thermal balance, and fluid flow a code with the method of finite element is introduced. After validation of various features of the code with melting profile, heat generation, charge curve, and dispersion curve with benchmarks, the eigenfrequency analysis of the system is done. The thermal behavior of the system at first mode and various boundary conditions are studied. As well, the effect of nanoparticles in fastening the cooling of the BAW resonator is demonstrated. Full article
(This article belongs to the Special Issue Magnetic Materials, Thin Films and Nanostructures)
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15 pages, 4987 KiB  
Review
Magnetic Force Microscopy on Nanofibers—Limits and Possible Approaches for Randomly Oriented Nanofiber Mats
by Andrea Ehrmann and Tomasz Blachowicz
Magnetochemistry 2021, 7(11), 143; https://doi.org/10.3390/magnetochemistry7110143 - 27 Oct 2021
Cited by 2 | Viewed by 2731
Abstract
Magnetic force microscopy (MFM) belongs to the methods that enable spatially resolved magnetization measurements on common thin-film samples or magnetic nanostructures. The lateral resolution can be much higher than in Kerr microscopy, another spatially resolved magnetization imaging technique, but since MFM commonly necessitates [...] Read more.
Magnetic force microscopy (MFM) belongs to the methods that enable spatially resolved magnetization measurements on common thin-film samples or magnetic nanostructures. The lateral resolution can be much higher than in Kerr microscopy, another spatially resolved magnetization imaging technique, but since MFM commonly necessitates positioning a cantilever tip typically within a few nanometers from the surface, it is often more complicated than other techniques. Here, we investigate the progresses in MFM on magnetic nanofibers that can be found in the literature during the last years. While MFM measurements on magnetic nanodots or thin-film samples can often be found in the scientific literature, reports on magnetic force microscopy on single nanofibers or chaotic nanofiber mats are scarce. The aim of this review is to show which MFM investigations can be conducted on magnetic nanofibers, where the recent borders are, and which ideas can be transferred from MFM on other rough surfaces towards nanofiber mats. Full article
(This article belongs to the Special Issue Advances in Magnetic Force Microscopy)
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9 pages, 2572 KiB  
Article
Breaking of Odd Chirality in Magnetoelectrodeposition of Copper Films on Micro-Electrodes
by Iwao Mogi, Ryoichi Aogaki and Kohki Takahashi
Magnetochemistry 2021, 7(11), 142; https://doi.org/10.3390/magnetochemistry7110142 - 27 Oct 2021
Cited by 4 | Viewed by 1836
Abstract
The surface chirality was investigated in magnetoelectrodeposition (MED) of copper films on micro-disc electrodes with the diameters of 100 and 25 µm. The MED was conducted in the magnetic fields of 1–5 T, which were parallel or antiparallel to the ionic currents. In [...] Read more.
The surface chirality was investigated in magnetoelectrodeposition (MED) of copper films on micro-disc electrodes with the diameters of 100 and 25 µm. The MED was conducted in the magnetic fields of 1–5 T, which were parallel or antiparallel to the ionic currents. In the case of 100 µm-electrodes, the MED films prepared in 2 and 3 T exhibited odd chirality for the magnetic field polarity, as expected in the magnetohydrodynamic (MHD) vortex model. However, the films prepared in the higher fields of 4 and 5 T exhibited breaking of odd chirality. In the case of the 25 µm-electrode, the broken odd chirality was observed in 2 and 3 T. These results indicate that the strong vertical MHD flows induce the breaking of odd chirality. The mapping of chiral symmetry on the axes of the magnetic field and electrode diameter demonstrate that the odd chirality could be easily broken by the fluctuation of micro-MHD vortices. Full article
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9 pages, 1641 KiB  
Article
Large Perpendicular Exchange Energy in TbxCo100−x/Cu(t)/[Co/Pt]2 Heterostructures
by Sina Ranjbar, Satoshi Sumi, Kenji Tanabe and Hiroyuki Awano
Magnetochemistry 2021, 7(11), 141; https://doi.org/10.3390/magnetochemistry7110141 - 25 Oct 2021
Cited by 3 | Viewed by 2547
Abstract
In order to realize a perpendicular exchange bias for applications, a robust and tunable exchange bias is required for spintronic applications. Here, we show the perpendicular exchange energy (PEE) in the TbxCo100−x/Cu/[Co/Pt]2 heterostructures. The structure consists of amorphous [...] Read more.
In order to realize a perpendicular exchange bias for applications, a robust and tunable exchange bias is required for spintronic applications. Here, we show the perpendicular exchange energy (PEE) in the TbxCo100−x/Cu/[Co/Pt]2 heterostructures. The structure consists of amorphous ferrimagnetic Tb–Co alloy films and ferromagnetic Co/Pt multilayers. The dependence of the PEE on the interlayer thickness of Cu and the composition of Tb–Co were analyzed. We demonstrate that the PEE can be controlled by changing the Cu interlayer thickness of 0.2 < tCu < 0.3 (nm). We found that PEE reaches a maximum value (σPw = 1 erg/cm2) at around x = 24%. We, therefore, realize the mechanism of PEE in the TbxCo100−x/Cu/[Co/Pt]2 heterostructures. We observe two competing mechanisms—one leading to an increase and the other to a decrease—which corresponds to the effect of Tb content on saturation magnetization and the coercivity of heterostructures. Sequentially, our findings show possibilities for both pinned layers in spintronics and memory device applications by producing large PEE and controlled PEE by Cu thickness, based on TbxCo100−x/Cu/[Co/Pt]2 heterostructures. Full article
(This article belongs to the Special Issue Advances in Antiferromagnetic Spintronics)
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