Magnetochemistry

11 pages, 2283 KiB

Open AccessArticle

Interlayer Coupling and High-Frequency Performance in Magnetic Anisotropic FeCoB/Hf/FeCoB Trilayers with Various Hf Thicknesses

by Duo Liu, Shouheng Zhang and Shandong Li

Magnetochemistry 2022, 8(6), 65; https://doi.org/10.3390/magnetochemistry8060065 - 16 Jun 2022

Viewed by 1968

Abstract

FeCoB (25 nm)/Hf(

t_{Hf}

)/FeCoB (25 nm) sandwich films with different hafnium thicknesses

t_{Hf}

were fabricated using a modified compositional gradient sputtering method to obtain self-biased high-frequency performances. The effects of

t_{Hf}

on the interlayer coupling and FMR frequency were [...] Read more.

FeCoB (25 nm)/Hf(

t_{Hf}

)/FeCoB (25 nm) sandwich films with different hafnium thicknesses

t_{Hf}

were fabricated using a modified compositional gradient sputtering method to obtain self-biased high-frequency performances. The effects of

t_{Hf}

on the interlayer coupling and FMR frequency were investigated. It is revealed that interlayer coupling enhanced the resonance frequency by 48%, and a ferromagnetic coupling between the FeCoB films occurred for the trilayers with

t_{Hf}

< 3.0 nm, likely due to the interface roughness and pinhole effect. In this case, only acoustic mode resonance was observed with the same high-frequency performance as the corresponding FeCoB single layer. In contrast, a

t_{Hf}

-dependent antiferromagnetic interlayer coupling appeared at

t_{Hf}

> 3.0 nm. The coupling coefficient J₁ was antiferromagnetic, and a biquadratic coupling J₂ appeared at t_Hf > 3.5 nm. The coupling mechanism was simulated and verified by Layadi’s rigid model, and the simulation was consistent with the experimental results. Full article

(This article belongs to the Special Issue Recent Research on Ferromagnetic Materials)

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11 pages, 2051 KiB

Open AccessArticle

Control of Molecular Orientation and Carrier Transport of Thiophene-Based Semiconducting Polymer via Superparamagnetic Nanoparticles Fe₃O₄@C-Assisted Magnetic Alignment Method

by Di Hui, Tian Li, Chun Ye and Guoxing Pan

Magnetochemistry 2022, 8(6), 64; https://doi.org/10.3390/magnetochemistry8060064 - 10 Jun 2022

Viewed by 2789

Abstract

Realizing the high molecular orientation and structurally ordered microstructure of organic semiconductor polymer thin films is beneficial for enhancing the charge transport of conjugated polymers and achieving high-performance organic electronic devices. In this work, we successfully developed large-area highly aligned films of a [...] Read more.

Realizing the high molecular orientation and structurally ordered microstructure of organic semiconductor polymer thin films is beneficial for enhancing the charge transport of conjugated polymers and achieving high-performance organic electronic devices. In this work, we successfully developed large-area highly aligned films of a thiophene-based polymer, namely poly(2,5-bis(3-alkylthiophen-2-yl) thieno [3,2-b] thiophene) (PBTTT), using the magnetic alignment method at a low magnetic field (0.12 T), which was assisted by superparamagnetic nanoparticles Fe₃O₄@C. The aligned microstructure of the composite films is confirmed by systematic analysis that includes polarized optical microscopy, polarized UV–visible absorption spectroscopy, and an atomic force microscope. Organic field effect transistors based on magnetic aligned composite film exhibit a 2.8-fold improvement in carrier mobility compared with the unaligned films. We hold a formation mechanism that the rapid magnetically induced self-assembly property of Fe₃O₄@C and its intermolecular interaction with polymer chains are key to the new method of preparing oriented thin films. Full article

(This article belongs to the Special Issue Study on the Growth and Performance of Materials under Magnetic Field)

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15 pages, 4598 KiB

Open AccessArticle

Simulating Evaluation Method on Heating Performances of Magnetic Nanoparticles with Temperature-Dependent Heating Efficiencies in Tumor Hyperthermia

by Shuai-Wen Ding, Cheng-Wei Wu, Xiao-Gang Yu, Chao Dai, Wei Zhang and Jian-Po Gong

Magnetochemistry 2022, 8(6), 63; https://doi.org/10.3390/magnetochemistry8060063 - 8 Jun 2022

Cited by 4 | Viewed by 2334

Abstract

The magnetic nanoparticles (MNPs) with decreasing heating efficiency (characterized by specific loss power, SLP) with temperature increase, especially around the Curie temperature (T_C), are expected to realize the self-regulated temperature hyperthermia of the tumor. However, the actual decrease of [...] Read more.

The magnetic nanoparticles (MNPs) with decreasing heating efficiency (characterized by specific loss power, SLP) with temperature increase, especially around the Curie temperature (T_C), are expected to realize the self-regulated temperature hyperthermia of the tumor. However, the actual decrease of the SLP is gradual, resulting in the deviation of self-regulated temperatures from the measured T_C. So far, no method is available for evaluating the heating performances of those MNPs. Here, by simulating the temperature-dependent SLP, the heating performances of MNPs are evaluated from three clinically concerning aspects: the capacity for effective heating, the temperature uniformity in the tumor, and the temperature stability under environmental changes such as MNP loss or tumor progression. The developed methods were applied to ZnCoCrFeO, Fe₃O₄, and γ-Fe₂O₃ MNPs. It was found that the uniform temperature distribution relies on lowering the heating power in the inner regions of the tumor, and the stable control of temperature depends on the dynamic adaptation of the heating power to the tumor temperature change. The proposed method may be used to predict the heating ability of MNPs and help the selection of MNPs for hyperthermia. Full article

(This article belongs to the Special Issue Biofunctionization and Applications of Magnetic Particles)

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9 pages, 3762 KiB

Open AccessArticle

Influence of a Constant Perpendicular High Magnetic Field on the Electrodeposition of Calcium Phosphate Coating

by Anne-Lise Daltin and Jean-Paul Chopart

Magnetochemistry 2022, 8(6), 62; https://doi.org/10.3390/magnetochemistry8060062 - 7 Jun 2022

Cited by 3 | Viewed by 1983

Abstract

Calcium phosphate coatings were formed on a Ti6Al4V substrate by electrodeposition under a high magnetic field up to 16 T. The magnetic field was parallelly applied to the vertical surface electrode. Changes in crystal morphology of calcium phosphates were investigated as a function [...] Read more.

Calcium phosphate coatings were formed on a Ti6Al4V substrate by electrodeposition under a high magnetic field up to 16 T. The magnetic field was parallelly applied to the vertical surface electrode. Changes in crystal morphology of calcium phosphates were investigated as a function of the magnetic field amplitude, and the results are discussed in terms of magnetic field effects. Magnetohydrodynamic convection due to the Lorentz force could considerably reduce the formation of volcano-like structures and generate more uniform deposits without changing Ca/P ratios. Full article

(This article belongs to the Special Issue Magnetohydrodynamic Effect in Electrochemical Processes: Magnetoelectrodeposition, Magnetoelectrocatalysis, and Related Studies)

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23 pages, 6776 KiB

Open AccessArticle

Magnetohydrodynamic Effects on Third-Grade Fluid Flow and Heat Transfer with Darcy–Forchheimer Law over an Inclined Exponentially Stretching Sheet Embedded in a Porous Medium

by Amir Abbas, Mdi Begum Jeelani and Nadiyah Hussain Alharthi

Magnetochemistry 2022, 8(6), 61; https://doi.org/10.3390/magnetochemistry8060061 - 6 Jun 2022

Cited by 31 | Viewed by 2521

Abstract

The major aim of the current investigations is to study the magnetohydrodynamic effects on heat and mass transfer phenomena in third-grade fluid past an inclined exponentially stretching sheet fixed in a porous medium with Darcy–Forchheimer law influence. The constitutive equations compatible for heat [...] Read more.

The major aim of the current investigations is to study the magnetohydrodynamic effects on heat and mass transfer phenomena in third-grade fluid past an inclined exponentially stretching sheet fixed in a porous medium with Darcy–Forchheimer law influence. The constitutive equations compatible for heat and mass transportation in third-grade fluid in terms of partial differential equations are modeled. These partial differential equations are then converted to ordinary differential equations by using suitable similarity variables formulation. The transformed flow model is solved by using MATLAB built-in numerical solver bvp4c. Effects of pertinent parameters on physical properties that are velocity field, temperature field and mass concentration along with skin friction coefficient, Nusselt number and Sherwood number are demonstrated in graphs and tables. The impact of dimensionless numbers on the physical properties is analyzed and discussed with a physical view point at angle

α = π / 6

(inclined sheet). It is seen that as the third-grade fluid parameter

(0.1 \leq β \leq 11)

is increased, the velocity profile increases, but the temperature field and mass concentration are decreased. It is observed that as the permeability parameter

(1 \leq K^{*} \leq 11)

is raised, the velocity distribution decreases and mass concentration increases. It is concluded from the results that owing to an increase in the local inertial coefficient

(0.1 \leq F r \leq 5)

, the velocity profile reduces but an increment in mass concentration is noted. It is concluded that by increasing values of magnetic field parameter

(0.1 \leq M \leq 10)

the velocity field is delineated and temperature field is elevated exactly according to the physics of magnetic field parameters. The present results are compared with already published results and it is observed that there is good agreement between them. This good agreement ensures the validation of accuracy of the results. Full article

(This article belongs to the Special Issue Magnetohydrodynamic Effect in Electrochemical Processes: Magnetoelectrodeposition, Magnetoelectrocatalysis, and Related Studies)

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27 pages, 8096 KiB

Open AccessFeature PaperReview

Magnetic Losses in Soft Ferrites

by Samuel Dobák, Cinzia Beatrice, Vasiliki Tsakaloudi and Fausto Fiorillo

Magnetochemistry 2022, 8(6), 60; https://doi.org/10.3390/magnetochemistry8060060 - 2 Jun 2022

Cited by 33 | Viewed by 4747

Abstract

We review the basic phenomenology of magnetic losses from DC to 1 GHz in commercial and laboratory-prepared soft ferrites considering recent concepts regarding their physical interpretation. This is based, on the one hand, on the identification of the contributions to the magnetization process [...] Read more.

We review the basic phenomenology of magnetic losses from DC to 1 GHz in commercial and laboratory-prepared soft ferrites considering recent concepts regarding their physical interpretation. This is based, on the one hand, on the identification of the contributions to the magnetization process provided by spin rotations and domain walls and, on the other hand, the concept of loss separation. It additionally contemplates a distinction between the involved microscopic dissipation mechanisms: spin damping and eddy currents. Selected experimental results on the broadband behavior of complex permeability and losses in Mn-Zn ferrites provide significant examples of their dependence on sintering methods, solute elements, and working temperature. We also highlight the peculiar frequency and temperature response of Ni-Zn ferrites, which can be heavily affected by magnetic aftereffects. The physical modeling of the losses brings to light the role of the magnetic anisotropy and the way its magnitude distribution, affected by the internal demagnetizing fields, acts upon the magnetization process and its dependence on temperature and frequency. It is shown that the effective anisotropy governs the interplay of domain wall and rotational processes and their distinctive dissipation mechanisms, whose contributions are recognized in terms of different loss components. Full article

(This article belongs to the Special Issue Development and Applications of Advanced Magnetic Ceramic Materials)

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19 pages, 6098 KiB

Open AccessArticle

Pressure–Temperature Phase Diagram of Multiferroic TbFe_2.46Ga_0.54(BO₃)₄

by Alexander Krylov, Svetlana Krylova, Irina Gudim, Yuri Kitaev, Elena Golovkina, Haibo Zhang and Alexander Vtyurin

Magnetochemistry 2022, 8(6), 59; https://doi.org/10.3390/magnetochemistry8060059 - 1 Jun 2022

Cited by 2 | Viewed by 1816

Abstract

The pressure–temperature phase diagram of the multiferroic TbFe

_{2.46}

Ga

_{0.54}

(BO

_{3}

)

_{4}

was studied for hydrostatic pressures up to 7 GPa and simultaneously with temperatures up to 400 K by the Raman spectroscopy technique. The structural phase transition from the [...] Read more.

The pressure–temperature phase diagram of the multiferroic TbFe

_{2.46}

Ga

_{0.54}

(BO

_{3}

)

_{4}

was studied for hydrostatic pressures up to 7 GPa and simultaneously with temperatures up to 400 K by the Raman spectroscopy technique. The structural phase transition from the

R 32

phase to the

P 3_{1} 21

phase was determined by observing the condensation of soft modes and the appearance of new lines. An increase in pressure leads to an increase in the temperature of the structural phase transition. These phases are stable over the entire investigated temperature and pressure range. No other phases have been found. Full article

(This article belongs to the Special Issue Multiferroic Materials 2021)

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Magnetochemistry, Volume 8, Issue 6 (June 2022) – 7 articles

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