Magnetochemistry

Open AccessArticle

Substitution Effects in Spin-Polarized (Cr_4-xFe_x)_0.5AC (A = Ge, Si, Al) MAX Phases

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Sergei G. Ovchinnikov

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Magnetochemistry 2023, 9(6), 147; https://doi.org/10.3390/magnetochemistry9060147 - 30 May 2023

Abstract

The use of spintronic devices with a tunable magnetic order on small scales is highly important for novel applications. The MAX phases containing transition metals and/or magnetic ion-substituted lattices attract a lot of attention. In this study, the magnetic and electronic properties of [...] Read more.

The use of spintronic devices with a tunable magnetic order on small scales is highly important for novel applications. The MAX phases containing transition metals and/or magnetic ion-substituted lattices attract a lot of attention. In this study, the magnetic and electronic properties of (Cr_4-xFe_x)_0.5AC (A = Ge, Si, Al) compounds were predicted and investigated within the density functional theory. It was established that single-substituted (Cr₃Fe₁)_0.5AC (A = Ge, Si, Al) lattices are favorable in terms of energy. An analysis of the magnetic states of the MAX phases demonstrated that their spin order changes upon substitution of iron atoms for chromium ones. It was found that mostly the (Cr_4-xFe_x)_0.5GeC and (Cr_4-xFe_x)_0.5AlC lattices acquire a ferrimagnetic state in contrast to (Cr_4-xFe_x)_0.5SiC for which the ferromagnetic spin order dominates. It was pointed out that the atomic substitution could be an efficient way to tune the magnetic properties of proposed (Cr_4-xFe_x)_0.5AC (A = Ge, Si, Al) MAX phases. Full article

(This article belongs to the Section Spin Crossover and Spintronics)

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Open AccessArticle

Research on the Surfactant-Assisted Synthesis of MnZn Ferrite Precursor Powders

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Magnetochemistry 2023, 9(6), 146; https://doi.org/10.3390/magnetochemistry9060146 - 30 May 2023

Abstract

MnZn ferrite precursor powders were prepared by the nano in situ composite method. Three surfactants, which include polyethylene glycol 400 (PEG-400), cetyltrimethyl ammonium bromide (CTAB), and sodium dodecyl sulfate (SDS), were usedM and the impact of the surfactants on the precursor sol solutions [...] Read more.

MnZn ferrite precursor powders were prepared by the nano in situ composite method. Three surfactants, which include polyethylene glycol 400 (PEG-400), cetyltrimethyl ammonium bromide (CTAB), and sodium dodecyl sulfate (SDS), were usedM and the impact of the surfactants on the precursor sol solutions and precursor powders was studied. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, a field emission scanning electron microscope (FE-SEM), a transmission electron microscope (TEM), a Zeta potential meter, a BET surface analyzer, and a vibrational sample magnetometer (VSM) were used to characterize the precursor sol solutions and the precursor powders. The results showed that these surfactants can improve the dispersion state and Zeta potentials of sol particles and increase the specific surface areas of the precursor powders. Moreover, the precursor powders were composed of MnZn ferrite, and some were amorphous. CTAB was the optimum surfactant and the zeta potential of the sol particles and the specific surface area of the precursor powders named P-0.1CTAB are 10.7 mV and 129.07 m²/g, respectively. In addition, the nano-particles that were made up of the P-0.1CTAB precursor powders had smaller sizes and more uniform particle distributions than the others. The magnetic properties’ improvement was attributed to the addition of surfactants, and CTAB is the optimal type. In addition, the novel nano in situ composite method will inspire fresh thinking and investigation into the research of ferrite. Full article

(This article belongs to the Special Issue Advances in Soft Magnetic Materials)

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Open AccessArticle

Fabrication and Soft Magnetic Properties of Fe–Si–Cr Composites with Double-Insulating Layers Suitable for High-Frequency Power Applications

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Magnetochemistry 2023, 9(6), 145; https://doi.org/10.3390/magnetochemistry9060145 - 30 May 2023

Abstract

Soft magnetic composites (SMCs) are composed of alloy materials with the core and insulating layers as the shell. These composites exhibit high saturation magnetic sensitivity and low hysteresis loss, making them a promising material for various applications. The investigation of double layers is [...] Read more.

Soft magnetic composites (SMCs) are composed of alloy materials with the core and insulating layers as the shell. These composites exhibit high saturation magnetic sensitivity and low hysteresis loss, making them a promising material for various applications. The investigation of double layers is considered valuable as it can effectively address the issues of low resistivity and high dynamic loss that arise from non-uniform insulating layers in SMCs. In this study, Fe-Si-Cr/SiO₂ particles with a core–shell heterostructure were produced via chemical vapor deposition (CVD). The Fe-Si-Cr/SiO₂ materials were coated with different weight percentages (1–6%) of sodium silicate (SS). Subsequently, Fe-Si-Cr-based SMCs were synthesized through high-pressure molding and heat treatment. The effect of the SS weight percentage on microscopic changes and magnetic characteristics was investigated. These findings indicated that a concentration of 4 wt% of SS was the most effective at enhancing magnetic characteristics. The resultant SMCs exhibited high resistivity (21.07 mΩ·cm), the lowest total loss (P_{10 mt/300 kHz} of 44.23 W/kg), a relatively high saturation magnetization (181.8 emu/g), and permeability (35.9). Furthermore, it was observed that the permeability exhibited stabilization at lower frequencies. According to these findings, the combination of CVD and double layers could lead to the further development of SMCs in a variety of applications. Full article

(This article belongs to the Special Issue Advances in Soft Magnetic Materials)

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Open AccessArticle

Magnetism and Exchange Bias Properties in Ba₂ScRuO₆

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Prachi Mohanty

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Sourav Marik

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Ravi Prakash Singh

Magnetochemistry 2023, 9(6), 144; https://doi.org/10.3390/magnetochemistry9060144 - 29 May 2023

Abstract

This paper presents structural, detailed magnetic, and exchange bias studies in polycrystalline Ba

_{2}

ScRuO

_{6}

synthesized at ambient pressure. In contrast to its strontium analogue, this material crystallizes in a 6L hexagonal structure with space group P

\bar{3}

m1. The Rietveld [...] Read more.

This paper presents structural, detailed magnetic, and exchange bias studies in polycrystalline Ba

_{2}

ScRuO

_{6}

synthesized at ambient pressure. In contrast to its strontium analogue, this material crystallizes in a 6L hexagonal structure with space group P

\bar{3}

m1. The Rietveld refinement using the room-temperature powder XRD pattern suggests a Ru-Sc disorder in the structure. The temperature variation of the DC electrical resistivity highlights a semiconducting behavior with the electron conduction corresponding to Mott’s 3D variable range hopping (VRH) model. The detailed magnetization measurements show that Ba

_{2}

ScRuO

_{6}

develops antiferromagnetic ordering at

T_{N}

≈ 9 K. Interestingly, below 9 K (T

_{N}

), the field-cooled magnetic field variation (FC) of the magnetization curves highlights an exchange bias effect in the sample. The exchange bias field reaches a maximum value of 1.24 kOe at 2 K. The exchange bias effect below the magnetic ordering temperature can be attributed to the inhomogeneous magnetic correlations due to the disorder in the structure. Remarkably, the appearance of a large exchange bias field in Ba

_{2}

ScRuO

_{6}

indicates that inhomogeneous hexagonal double perovskites are a promising class to explore new materials having potential applications in spintronics. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Magnetic and Magnetoelectric Materials)

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Open AccessArticle

Study of Dynamic Viscoelasticity of a Mineral Oil-Based Magnetic Fluid

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Magnetochemistry 2023, 9(6), 143; https://doi.org/10.3390/magnetochemistry9060143 - 29 May 2023

Abstract

Magnetic fluid is a field-responsive intelligent fluid, which has the flow characteristics of liquid and the elastic properties of solid. Because of its unique properties, it has a strong application prospect in the fields of magnetic soft robot, intelligent sensor, and so on. [...] Read more.

Magnetic fluid is a field-responsive intelligent fluid, which has the flow characteristics of liquid and the elastic properties of solid. Because of its unique properties, it has a strong application prospect in the fields of magnetic soft robot, intelligent sensor, and so on. Dynamic viscoelasticity is a significant index to investigate the performance of magnetic fluid in the application process. In this paper, the dynamic viscoelasticity of a homemade mineral oil-based magnetic fluid was investigated under oscillatory shear experimental conditions using an MCR302 rheometer, and the effects of different temperatures and magnetic fields on the dynamic viscoelasticity were examined. Amplitude sweeps tests showed that the value of the storage modulus remained constant within the linear viscoelastic region (LVE) and the stable structure was not destroyed. As the magnetic field strength increased or the temperature increased, the range of the linear viscoelastic zone decreased. At large amplitude, the loss modulus will first appear as a peak and then decrease. The frequency sweep experiment showed that the storage modulus and loss modulus increased with the increase in angular frequency, and the greater the magnetic field intensity, the longer the internal structure relaxation time. When the magnetic field was constant, the higher the temperature, the smaller the storage modulus and loss modulus of the magnetic fluid. At high temperature, the loss coefficient of mesmeric fluid was large, and the magnetic fluid was more viscous. The lower the temperature is, the smaller the loss coefficient of the magnetic fluid is, and the magnetic fluid is more pliant. The study of dynamic viscoelasticity of magnetic fluids lays the foundation for establishing the complete structure intrinsic relationship of magnetic fluids and provides guidance for the application of magnetic fluids in magnetic 3D printing, droplet robot, and smart wear. Full article

(This article belongs to the Section Applications of Magnetism and Magnetic Materials)

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Open AccessArticle

Magnetoelectric Coupling Effects in Tb-Doped BiFeO₃ Nanoparticles

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Iliana Apostolova

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Angel Apostolov

and

Julia Wesselinowa

Magnetochemistry 2023, 9(6), 142; https://doi.org/10.3390/magnetochemistry9060142 - 26 May 2023

Abstract

The magnetic, electric, and optical properties in Tb-doped BiFeO₃ nanoparticles as functions of size and doping concentrations were investigated using a microscopic model, taking into account both linear and quadratic magnetoelectric (ME) coupling. We observed improved multiferroic properties and band-gap tuning. The [...] Read more.

The magnetic, electric, and optical properties in Tb-doped BiFeO₃ nanoparticles as functions of size and doping concentrations were investigated using a microscopic model, taking into account both linear and quadratic magnetoelectric (ME) coupling. We observed improved multiferroic properties and band-gap tuning. The magnetization and polarization increased with the decreased nanoparticle size and increased Tb-doping substitution x. The Neel temperature remained nearly unchanged whereas the Curie temperature was reduced with the increased x. There was doping-induced ME coupling. The dielectric constant is discussed as a function of the size, doping, and the magnetic field. The band gap decreased with the decreased size or increased Tb dopants due to competing effects of the compressive strain, oxygen defects on the surface, and Coulomb interactions. Increasing the Tb dopants and decreasing the nanoparticle size improved the ME effect. Full article

(This article belongs to the Special Issue Advances in Magnetic Nanomaterials and Nanostructures)

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Open AccessArticle

Thermal Conductivity for p–(Bi, Sb)₂Te₃ Films of Topological Insulators

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Lidia N. Lukyanova

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Yuri A. Boikov

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Oleg A. Usov

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Viacheslav A. Danilov

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Igor V. Makarenko

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Vasilii N. Petrov

Magnetochemistry 2023, 9(6), 141; https://doi.org/10.3390/magnetochemistry9060141 - 25 May 2023

Abstract

In this study, we investigated the temperature dependencies of the total, crystal lattice, and electronic thermal conductivities in films of topological insulators p–Bi_0.5Sb_1.5Te₃ and p–Bi₂Te₃ formed by discrete and thermal evaporation methods. The largest decrease [...] Read more.

In this study, we investigated the temperature dependencies of the total, crystal lattice, and electronic thermal conductivities in films of topological insulators p–Bi_0.5Sb_1.5Te₃ and p–Bi₂Te₃ formed by discrete and thermal evaporation methods. The largest decrease in the lattice thermal conductivity because of the scattering of long-wavelength phonons on the grain interfaces was observed in the films of the solid-solution p–Bi_0.5Sb_1.5Te₃ deposited by discrete evaporation on the amorphous substrates of polyimide without thermal treatment. It was shown that in the p–Bi_0.5Sb_1.5Te₃ films with low thermal conductivity, the energy dependence of the relaxation time is enhanced, which is specific to the topological insulators. The electronic thermal conductivity was determined by taking into account the effective scattering parameter in the relaxation time approximation versus energy in the Lorentz number calculations. A correlation was established between the thermal conductivity and the peculiarities of the morphology of the interlayer surface (0001) in the studied films. Additionally, the total κ and the lattice κ_L thermal conductivities decrease, while the number of grains and the roughness of the surface (0001) increase in unannealed films compared to annealed ones. It was demonstrated that increasing the thermoelectric figure of merit ZT in the p–Bi_0.5Sb_1.5Te₃ films formed by discrete evaporation on a polyimide substrate is determined by an increase in the effective scattering parameter in topological insulators due to enhancement in the energy dependence of the relaxation time. Full article

(This article belongs to the Special Issue Spin and Charge Transport in Novel Quantum and Topological Materials)

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Open AccessArticle

Controlling the Magnetic Properties of La_0.9A_0.1Mn_0.9Cr_0.1O₃ (A: Li, K, Na) Powders and Ceramics by Alkali Ions Doping

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Aliaksandr Zhaludkevich

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Dmitry Karpinsky

Magnetochemistry 2023, 9(6), 140; https://doi.org/10.3390/magnetochemistry9060140 - 25 May 2023

Abstract

Nanocrystalline La_0.9A_0.1Mn_0.9Cr_0.1O₃ (A: Li, K, Na) powders have been synthesized by combustion method. The powders were used to prepare ceramics by high-pressure low-temperature sintering technique. For all samples the structure, elemental composition and morphology [...] Read more.

Nanocrystalline La_0.9A_0.1Mn_0.9Cr_0.1O₃ (A: Li, K, Na) powders have been synthesized by combustion method. The powders were used to prepare ceramics by high-pressure low-temperature sintering technique. For all samples the structure, elemental composition and morphology were studied using X-ray diffraction (XRD), Raman spectroscopy, Energy-Dispersive X-ray Spectroscopy (EDS) and Scanning electron microscopy (SEM). Magnetic properties were studied using magnetometry methods and the valency changes of the cations after alkali ions doping were studied using X-ray photoelectron spectroscopy (XPS). The influence of the sintering pressure on the structural and magnetic properties of the manganites doped with different alkali ions and chromium was also investigated. Magnetization properties were studied as a function of sintering pressure and type of the dopant. Chemical doping with alkali ions as well as external pressure significantly changed the magnetic properties of the compounds. It was found that the magnetic properties of the manganites could be predictably modified through the use of a suitable dopant element. Full article

(This article belongs to the Special Issue Synthetic, Natural and Natural-Synthetic Hybrid Magnetic Structures: Technology and Application)

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Open AccessArticle

Hydrothermal Synthesis and Magnetic Properties of Zn/Mn Oxides Nano Particles

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Izabela Kuryliszyn-Kudelska

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Magnetochemistry 2023, 9(6), 139; https://doi.org/10.3390/magnetochemistry9060139 - 25 May 2023

Abstract

The aim of this study was to investigate the magnetic properties of mixed nanocrystalline Zn/manganese oxide compounds synthesized by a hydrothermal method. These compounds are designed as (ZnO)_1−n(MnO)_n, where index n ranges from 0.05 to 0.60. The results of [...] Read more.

The aim of this study was to investigate the magnetic properties of mixed nanocrystalline Zn/manganese oxide compounds synthesized by a hydrothermal method. These compounds are designed as (ZnO)_1−n(MnO)_n, where index n ranges from 0.05 to 0.60. The results of magnetic measurements, including AC magnetic susceptibility as a function of temperature (up to 160 K) and frequency (from 7 Hz up to 9970 Hz), as well as DC magnetization in magnetic fields up to 9 T and temperature up to 50 K, are reported. We observed various types of magnetic behavior depending on the nominal weight content of MnO. Samples with a low nominal content (up to n = 0.10) of MnO exhibited Curie–Weiss behavior at higher temperatures. For samples with high nominal weight contribution (from n = 0.30 to 0.60), spin-glass-like or/and weak ferromagnetic behavior is observed. Full article

(This article belongs to the Special Issue Advances in Magnetic Nanomaterials and Nanostructures)

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Open AccessArticle

Influence of Mn Doping on Local Spin Moments and Stacking Fault Energies in Co(Mn) Alloys

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Magnetochemistry 2023, 9(6), 138; https://doi.org/10.3390/magnetochemistry9060138 - 23 May 2023

Abstract

We report on the results of first principles calculations investigating the influences of Mn doping on the local moments and stacking fault energies (SFEs) in the Co

_{95.8}

Mn

_{4.2}

and Co

_{91.6}

Mn

_{8.4}

systems as compared to pure face-centered cubic Co. [...] Read more.

We report on the results of first principles calculations investigating the influences of Mn doping on the local moments and stacking fault energies (SFEs) in the Co

_{95.8}

Mn

_{4.2}

and Co

_{91.6}

Mn

_{8.4}

systems as compared to pure face-centered cubic Co. A supercell was developed to maintain periodicity in calculations, provide a simple relaxation mechanism, and allow for easy expansion to accommodate different concentrations of Mn. Calculations to determine the generalized SFE were performed on relaxed and non-relaxed systems in both ferromagnetic and nonmagnetic states. Analysis revealed fluctuations in the magnetic moments that are closely tied to the relaxation state and faulting state of the system. In the case of systems containing Mn, we observed a dependence of the SFE on the location of the Mn atom(s) within the supercell relative to the stacking fault interface and a strong induced magnetic moment for these atoms. Full article

(This article belongs to the Special Issue Advances in Magnetic Nanomaterials and Nanostructures)

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Open AccessArticle

Magnetic Dilution as a Direct Method for Detecting and Evaluation of Exchange Interactions between Rare Earth Elements in Oxide Systems

by

Natalia Chezhina

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Anna Fedorova

Magnetochemistry 2023, 9(5), 137; https://doi.org/10.3390/magnetochemistry9050137 - 20 May 2023

Abstract

This work is devoted to the study of exchange interactions between rare earth atoms in the LaAlO₃ matrix. Using the magnetic dilution method, the study of concentration and temperature dependences of magnetic susceptibility and effective magnetic moments of diluted solid solutions the [...] Read more.

This work is devoted to the study of exchange interactions between rare earth atoms in the LaAlO₃ matrix. Using the magnetic dilution method, the study of concentration and temperature dependences of magnetic susceptibility and effective magnetic moments of diluted solid solutions the magnetic characteristics of single rare earth atoms and the character of superexchange between them are described—antiferromagnetic at low concentrations, and for samarium, predominantly ferromagnetic within greater clusters as the concentration increases. The development of superexchange is similar to the exchange between d-elements in the same matrix. Full article

(This article belongs to the Special Issue Phase Change Material and Magnetic Research)

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Open AccessArticle

Magnetic Adsorbent Based on Faujasite Zeolite Decorated with Magnesium Ferrite Nanoparticles for Metal Ion Removal

by

Mariana Rodrigues Meirelles

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João Otávio Donizette Malafatti

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Márcia Tsuyama Escote

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Alexandre Henrique Pinto

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Elaine Cristina Paris

Magnetochemistry 2023, 9(5), 136; https://doi.org/10.3390/magnetochemistry9050136 - 20 May 2023

Abstract

Magnetic nanoparticles are a promising alternative as a support in adsorption processes, aiming at the easy recovery of the aqueous medium. A faujasite zeolite (FAU) surface was decorated with magnesium ferrite (MgFe₂O₄) nanoparticles. FAU is a porous adsorbent with [...] Read more.

Magnetic nanoparticles are a promising alternative as a support in adsorption processes, aiming at the easy recovery of the aqueous medium. A faujasite zeolite (FAU) surface was decorated with magnesium ferrite (MgFe₂O₄) nanoparticles. FAU is a porous adsorbent with high specific surface area (SSA) and chemical stability. The FAU:MgFe₂O₄ nanocomposite 3:1 ratio (w w⁻¹) promotes the combination of the surface and magnetic properties. The results showed the effectiveness of the MgFe₂O₄ immobilization on the FAU surface, exhibiting a high SSA of 400 m² g⁻¹. The saturation magnetization (Ms) was verified as 5.9 emu g⁻¹ for MgFe₂O₄ and 0.47 emu g⁻¹ for FAU:MgFe₂O₄, an environmentally friendly system with soft magnetic characteristics. The magnetic nanocomposite achieved high adsorption values of around 94% removal for Co²⁺ and Mn²⁺ ions. Regarding its reuse, the nanocomposite preserved adsorption activity of above 65% until the third cycle. Thus, the FAU:MgFe₂O₄ nanocomposite presented favorable adsorptive, magnetic, and recovery properties for reuse cycles in polluted water. Full article

(This article belongs to the Special Issue Magnetic Nanoparticles: State of the Art and Future Perspectives)

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Open AccessCommunication

Superconducting Gap Structure of the Noncentrosymmetric Topological Superconductor Candidate HfRuP

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Magnetochemistry 2023, 9(5), 135; https://doi.org/10.3390/magnetochemistry9050135 - 19 May 2023

Abstract

We investigate the gap symmetry of the topological superconductor candidate HfRuP, which crystallizes in a noncentrosymmetric hexagonal crystal structure, using muon spin rotation/relaxation (

μ

SR) measurements in transverse-field (TF) geometry. The temperature and magnetic field dependencies of the superconducting relaxation rate derived [...] Read more.

We investigate the gap symmetry of the topological superconductor candidate HfRuP, which crystallizes in a noncentrosymmetric hexagonal crystal structure, using muon spin rotation/relaxation (

μ

SR) measurements in transverse-field (TF) geometry. The temperature and magnetic field dependencies of the superconducting relaxation rate derived from the TF-

μ

SR spectra can be well described by an isotropic s-wave gap. The superconducting carrier density

n_{s}

= 1.41(1) × 10

^{26}

m

^{- 3}

and the magnetic penetration depth,

λ

(0) = 603(2) nm, were calculated from the TF-

μ

SR data. Interestingly, the ratio between the superconducting transition temperature and the superfluid density,

T_{c}

/

λ

^{- 2}

(0) ∼ 3.3, is very close to those of unconventional superconductors. Further, our zero-field (ZF)

μ

SR results do not show any considerable change in the muon spin relaxation above and below the superconducting transition temperature, suggesting that time-reversal symmetry is preserved in the superconducting state of this superconductor. Full article

(This article belongs to the Section Applications of Magnetism and Magnetic Materials)

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Open AccessArticle

Influence of High Viscosity and Magnetoviscous Effect on the Washout Resistance of Magnetic Fluid

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Magnetochemistry 2023, 9(5), 134; https://doi.org/10.3390/magnetochemistry9050134 - 19 May 2023

Abstract

Magnetic fluid seals have long been thought to be a successful sealing form while sealing liquids are always a challenge. The instability of the liquid–liquid interface under the washout has become the key technical problem that hinders the realization of sealing liquid. This [...] Read more.

Magnetic fluid seals have long been thought to be a successful sealing form while sealing liquids are always a challenge. The instability of the liquid–liquid interface under the washout has become the key technical problem that hinders the realization of sealing liquid. This work mainly presents an experimental study about the influence of high viscosity and magnetoviscous effects on washout resistance. Three engine oil-based magnetic fluids of different viscosities were prepared with two kinds of surfactants. The magnetoviscous effects of the prepared magnetic fluids under different working conditions were found through rheological experiments. The viscosity of the three samples decreased at most by about 100 times with the shear rate increasing. An experimental platform was designed and built for the washout tests. The entire process of magnetic fluids being washed away was obtained experimentally. The magnetic fluid of higher viscosity can remain stationary with lower magnetic force. The quantitative results show that the viscosity of the magnetic fluid has a significant influence on washout resistance under a magnetic field. Full article

(This article belongs to the Special Issue Advanced Applications of Magnetic Field-Responsive Fluid)

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Open AccessEditorial

Magnetic Materials, Thin Films and Nanostructures

by

Catalin-Daniel Constantinescu

and

Lucian-Gabriel Petrescu

Magnetochemistry 2023, 9(5), 133; https://doi.org/10.3390/magnetochemistry9050133 - 19 May 2023

Abstract

In this first volume, we cover relevant aspects of chemical and physical processes of the production and characterization of magnetic materials in bulk, thin films, nanostructures, and/or nanocomposites, as well as modeling aspects involving such structures. Accordingly, this volume presents eleven original research [...] Read more.

In this first volume, we cover relevant aspects of chemical and physical processes of the production and characterization of magnetic materials in bulk, thin films, nanostructures, and/or nanocomposites, as well as modeling aspects involving such structures. Accordingly, this volume presents eleven original research and review works on the challenges and trends covering fundamental and experimental work, with a special focus on the design, synthesis, and characterization of various types of magnetic materials, and the study of their structure–property relationships. State-of-the-art results on the development of new experimental concepts, leading to the transfer, chemical transformation, and high-resolution patterning of advanced thin films and nanomaterials, and to the design and fabrication of devices, are also presented and discussed. Full article

(This article belongs to the Special Issue Magnetic Materials, Thin Film and Nanostructures)

Open AccessArticle

Solid Phase Extraction Penicillin and Tetracycline in Human Serum Using Magnetic Graphene Oxide-Based Sulfide Nanocomposite

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Magnetochemistry 2023, 9(5), 132; https://doi.org/10.3390/magnetochemistry9050132 - 19 May 2023

Abstract

Herein, we report a procedure for separating and preconcentrating antibiotics from human serum using a novel adsorbent of magnetic graphene oxide (MGO) and cadmium sulfide (CdS) nanoparticles. The adsorbent (MGO@CdS) was characterized using Fourier transformed infrared spectrometry (FT-IR), energy dispersive X-ray spectroscopy (EDX), [...] Read more.

Herein, we report a procedure for separating and preconcentrating antibiotics from human serum using a novel adsorbent of magnetic graphene oxide (MGO) and cadmium sulfide (CdS) nanoparticles. The adsorbent (MGO@CdS) was characterized using Fourier transformed infrared spectrometry (FT-IR), energy dispersive X-ray spectroscopy (EDX), and field emission scanning electron microscopy (FE-SEM). The effective parameters for extraction efficiency were investigated, including the desorption solvent’s nature, pH, adsorbent dose, salt concentration, extraction time, and volume of sample solution and desorption solvent. The proposed procedure proved to be fast (20 min), simple (two stages), and cost-effective (20 mg of nanoparticles). Under the optimum conditions, satisfactory linearity (R2 > 0.992) was obtained, and limits of detection (LOD) were estimated as 4.5 µg L⁻¹ (for tetracycline) and 5.7 µg L⁻¹ (for penicillin) and a linear dynamic range (LDR) from 20 to 200 µg L⁻¹. The magnetic solid phase extraction (MSPE) method based on MGO@CdS has achieved a satisfactory recovery (71.5–109.5%) in human serum for the selected antibiotics. Finally, the antibiotic’s release was studied in simulated fluids of the gastric (pH = 1.2) and intestine (pH = 7.4). In this light, we demonstrate that the newly introduced adsorbent can be used in drug extraction from different biological media. Full article

(This article belongs to the Special Issue Application of Magnetic Materials in Environmental Remediation)

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Open AccessFeature PaperArticle

Slow Magnetic Relaxation and Luminescence Properties in Tetra β-Diketonate Lanthanide(III) Complexes

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Magnetochemistry 2023, 9(5), 131; https://doi.org/10.3390/magnetochemistry9050131 - 16 May 2023

Abstract

The reaction of [Ln(btfa)₃(H₂O)₂] (btfa⁻ = 4,4,4-trifluoro-1-phenyl-1,3-butanedionate) with additional 4,4,4-trifluoro-1-phenyl-1,3-butanedione (Hbtfa) and acridine (Acr) in ethanol allows the isolation of the mononuclear compounds HAcr[Nd(btfa)₄]·EtOH, (1) and HAcr[Ln(btfa)₄], Ln = Dy [...] Read more.

The reaction of [Ln(btfa)₃(H₂O)₂] (btfa⁻ = 4,4,4-trifluoro-1-phenyl-1,3-butanedionate) with additional 4,4,4-trifluoro-1-phenyl-1,3-butanedione (Hbtfa) and acridine (Acr) in ethanol allows the isolation of the mononuclear compounds HAcr[Nd(btfa)₄]·EtOH, (1) and HAcr[Ln(btfa)₄], Ln = Dy (2) and Yb (3); HAcr⁺ = acridinium cation. Magnetic measurements indicate that complexes 1–3 show field-induced single-ion magnet behavior with anisotropy energy barriers and preexponential factors of U_eff = 20.7 cm⁻¹, τ₀ = 24.5 × 10⁻⁸ s; U_eff = 40.5 cm⁻¹, τ₀ = 8.6 × 10⁻¹⁰ s and U_eff = 22.7 cm⁻¹, τ₀ = 8.4 × 10⁻⁸ s, for 1–3 respectively. The solid-state luminescence emission in the NIR region shows efficient energy transfer from the 4,4,4-trifluoro-1-phenyl-1,3-butanedionate ligands to the central Ln³⁺ ion in the case of compounds 1 and 3. Full article

(This article belongs to the Special Issue Magnetic Relaxation in Metal Complexes)

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Open AccessArticle

A Chain of Vertex-Sharing {Co^III₂Co^II₂}_n Squares with Single-Ion Magnet Behavior

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Maria-Gabriela Alexandru

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Magnetochemistry 2023, 9(5), 130; https://doi.org/10.3390/magnetochemistry9050130 - 15 May 2023

Abstract

A new mixed-valence one-dimensional coordination polymer of formula {[Co^II(MeOH)₂][(μ-NC)₂Co^III(dmphen)(CN)₂]₂}_n·2nH₂O (1) was obtained by reacting the Ph₄P[Co^II(dmphen)(CN)₃ [...] Read more.

A new mixed-valence one-dimensional coordination polymer of formula {[Co^II(MeOH)₂][(μ-NC)₂Co^III(dmphen)(CN)₂]₂}_n·2nH₂O (1) was obtained by reacting the Ph₄P[Co^II(dmphen)(CN)₃] metalloligand (dmphen = 2,9-dimethyl-1,10-phenanthroline and Ph₄P⁺ = tetraphenylphosphonium ion) with cobalt(II) acetate tetrahydrate. The structural analysis shows the formation of a neutral 4,2-ribbon-like chain of vertex-sharing cyanido-bridged {Co^III₂Co^II₂} squares in which the metalloligand underwent an oxidation process and a reorganization to form {Co^III(dmphen)(CN)₄}⁻ linkers that coordinate to the [Co^II(MeOH)₂]²⁺ units through single cyanido ligands. Both cobalt(II) and Co(III) cations are six-coordinated in distorted octahedral environments. The shortest intrachain distance between the paramagnetic cobalt(II) ions is 7.36 Å, a value which is shorter than the shortest interchain one (10.36 Å). Variable-temperature (1.9–300 K) static (dc) magnetic measurements for 1 indicate the occurrence of magnetically isolated high-spin cobalt(II) ions with a D value of +67.0 cm⁻¹. Dynamic alternating current (ac) magnetic measurements between 2.0–13 K reveal that 1 exhibits slow magnetic relaxation under non-zero applied dc fields, being thus a new example of field-induced SIM with easy-plane magnetic anisotropy. Theoretical calculations by CASSCF/NEVPT2 on 1 support the results from magnetometry. The relaxation of the magnetization occurs in the ground state under external dc fields through a two-phonon Raman process and one intra-Kramers mechanism. Full article

(This article belongs to the Special Issue Advances in Molecular Magnetism)

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Open AccessArticle

Novel Concentric Magnetic Continuum Robot with Multiple Stiffness Modes for Potential Delivery of Nanomedicine

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Magnetochemistry 2023, 9(5), 129; https://doi.org/10.3390/magnetochemistry9050129 - 12 May 2023

Abstract

The utilisation of miniature robots has become essential in the domain of minimally invasive surgery and long-distance delivery of nanomedicine. Among these, the miniature magnetic continuum robot (MCR) stands out because of its simple structure and dexterity, which allow it to penetrate small [...] Read more.

The utilisation of miniature robots has become essential in the domain of minimally invasive surgery and long-distance delivery of nanomedicine. Among these, the miniature magnetic continuum robot (MCR) stands out because of its simple structure and dexterity, which allow it to penetrate small cavities, transport specialised tools such as a laser, and deliver medications to support surgical treatment. Nevertheless, because of their soft bodies with a single stiffness, conventional MCRs have limited controllability when navigating through intricate cavities. To address this limitation, we propose a novel concentric magnetic continuum robot (C-MCR) comprising a concentric magnetic catheter with a guidewire having varying stiffness. The C-MCR allows substantial curvature bending owing to its difference in stiffness, and its detachable nature allows it to have four working modes to adapt to specific application requirements with improved stiffness controllability. Experiments demonstrate the ability of the C-MCR to navigate complex pathways and deliver nanomedicines over long distances to specific areas via its internal channels using a large homemade eight-coil electromagnetic system. The C-MCR offers promising application prospects for the long-distance delivery of tailored nanomedicines because of its simple operation, reduced risks, and larger attainable workspace. Full article

(This article belongs to the Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects)

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