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A special issue of Magnetochemistry (ISSN 2312-7481). This special issue belongs to the section "Magnetic Materials".

Deadline for manuscript submissions: closed (20 October 2023) | Viewed by 22853

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Special Issue Editors

Prof. Dr. Devashibhai Adroja

E-Mail Website
Guest Editor

ISIS Facility, Rutherford Appleton Laboratory, Chlton OX11 0QX, UK
Interests: Magnetism and superconductivity

Prof. Dr. Dmitry Alexandrovich Filippov

E-Mail Website
Guest Editor

Polytechnical Institute, Yaroslav-the-Wise Novgorod State University, Veliky Novgorod 173003, Russia
Interests: magnetostriction; piezoelectricity; magnetoelectric effect
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Magnetic materials are an important class of materials for the development of technology as well as to our fundamental understanding of the microscopic magnetic interactions. They are constantly used in memory storage devices, power generation, medical and scientific equipment, and magnetic sensors. Magnetic materials represent an interdisciplinary field of research and researchers from physics, chemistry, materials science, engineering, and metallurgy work together to achieve a common goal, which is line with the scope of the Magnetochemistry journal. Rare earths ions possess a large magnetic moment, while transition metal ions have a high Curie temperature. These two properties can co-exist in the same material, which can help to produce novel materials such as high-performance permanent magnets.

Magnetoelectric materials have unique properties due to the relationship between the magnetic and electrical subsystems. Based on them, it is possible to create new devices in which control is exerted by both magnetic and electric fields.

The study of the properties and synthesis of new magnetoelectric materials will serve as a good impetus for the creation of fundamentally new electronic devices.

In this Special Issue of Magnetochemistry on “Magnetic and Magnetoelectric Materials”, we aim to share the latest advancements in magnetic and magnetoelectric materials. We therefore welcome high-quality research papers, original unpublished works, and review papers, focusing on rare earth and transition metal magnetism and the magnetoelectric effect. Although, rare-earth and transition metals exhibit an unusual and unique magnetism related to orbital wave functions, their alloys, and intermetallic and oxidative compounds, These features can be related to the strong coupling between spin, change, lattice, and orbital degrees of freedom. Furthermore, to explain the large variety of observed novel magnetic and magnetoelectric behaviors, electronic structure calculations need to be considered.

We hope to offer a platform for some of this exciting new research in magnetic and magnetoelectric materials, both experimental and theoretical, with a promotional Special Issue of the new Open Access journal Magnetochemistry, which aims to become a staple of research among the journals on the old but futuristic discipline after which it has been named.

Prof. Dr. Devashibhai Adroja
Prof. Dr. Dmitry Filippov
Guest Editors

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Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Magnetochemistry is an international peer-reviewed open access monthly journal published by MDPI.

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Keywords

magnetic materials
functional magnetic materials
rare-earth and transition metals magnetism
permanent magnet materials
magnetic structures and magnetic excitations
heavy fermion systems
quantum magnets
quantum spin-liquid behavior
spin-glass
multiferroic materials
magnetoelectric effect
ferrite-piezoelectric composites
magnetostrictive
magnetic nanoparticles
giant magnetoresistance (GMR)
magnetic skyrmions
electronic structure calculations
computational magnetism

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Published Papers (13 papers)

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Editorial

Jump to: Research

6 pages, 181 KiB

Open AccessEditorial

Magnetic and Magnetoelectric Materials

by Devashibhai Adroja and Dmitry Filippov

Magnetochemistry 2024, 10(2), 8; https://doi.org/10.3390/magnetochemistry10020008 - 1 Feb 2024

Cited by 1 | Viewed by 1583

Abstract

Magnetic materials are an important class of materials for the development of technology as well as for our fundamental understanding of microscopic magnetic interactions [...] Full article

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

Research

Jump to: Editorial

11 pages, 2729 KiB

Open AccessArticle

Process-Gas-Influenced Anti-Site Disorder and Its Effects on Magnetic and Electronic Properties of Half-Metallic Sr₂FeMoO₆ Thin Films

by Ekta Yadav, Ketan S. Navale, Gulloo L. Prajapati and Krushna R. Mavani

Magnetochemistry 2023, 9(7), 167; https://doi.org/10.3390/magnetochemistry9070167 - 28 Jun 2023

Cited by 3 | Viewed by 1706

Abstract

Anti-site disorder, arising due to the similar size of Fe and Mo ions in Sr₂FeMoO₆ (SFMO) double perovskites, hampers spintronic applicability by deteriorating the magnetic response of this double perovskite system. A higher degree of anti-site disorder can also completely destroy the half-metallicity of the SFMO system. To study the effects of different process gas conditions on the anti-site disorder, we have prepared a series of SFMO thin films on SrTiO₃ (001) single-crystal substrate using a pulsed laser deposition (PLD) technique. The films are grown either under vacuum or under N₂/O₂ partial gas pressures. The vacuum-grown SFMO film shows the maximum value of saturation magnetization (M_S) and Curie temperature (T_C), signaling the lowest anti-site disorder in this series. In other words, there is a long-range Fe/Mo-O-Mo/Fe ferrimagnetic exchange in the vacuum-grown thin film, thereby enhancing the magnetization. Further, all the SFMO films show a semiconducting state with a systematic increase in overall resistivity with the increased anti-site disorder. The electrical conduction mechanism is defined by the variable-range hopping model at low temperatures. Raman spectra show a weak Fano peak, suggesting the presence of electron–phonon coupling in SFMO thin films. These results show the significance of the process gas in causing anti-site disorder, tuning the degree of this disorder and therefore its influence on the structural, magnetic, electrical, and vibrational properties of SFMO thin films. Full article

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

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24 pages, 11538 KiB

Open AccessEditor’s ChoiceArticle

Interplay of Magnetic Interaction and Electronic Structure in New Structure RE-12442 Type Hybrid Fe-Based Superconductors

by Amit Pokhriyal, Abyay Ghosh, Smritijit Sen and Haranath Ghosh

Magnetochemistry 2023, 9(7), 164; https://doi.org/10.3390/magnetochemistry9070164 - 26 Jun 2023

Cited by 2 | Viewed by 1543

Abstract

We present detailed first-principles density functional theory-based studies on RbRE₂Fe₄As₄O₂ (RE = Sm, Tb, Dy, Ho) hybrid 12442-type iron-based superconducting compounds with particular emphasis on competing magnetic interactions and their effect on possible magneto-structural coupling and electronic structure. The stripe antiferromagnetic (sAFM) pattern across the xy plane emerges as the most favorable spin configuration for all the four compounds, with close competition among the different magnetic orders along the z-axis. The structural parameters, including arsenic heights, Fe-As-Fe angle, and other relevant factors that influence superconducting T

_{c}

and properties, closely match the experimental values in stripe antiferromagnetic arrangement of Fe spins. Geometry optimization with inclusion of explicit magnetic ordering predicts a spin–lattice coupling for all the four compounds, where a weak magneto–structural transition, a tetragonal-to-orthorhombic structural transition, takes place in the relaxed stripe antiferromagnetic spin configuration. Absence of any experimental evidence of such structural transition is possibly an indication of nematic transition in RE-12442 compounds. As a result of structural distortion, the lattice contracts (expands) along the direction with parallel (anti-parallel) alignment of Fe spins. Introduction of stripe antiferromagnetic order in Fe sub-lattice reconstructs the low-energy band structure, which results in significantly reduced number of bands crossing the Fermi level. Moreover, the dispersion of bands and their orbital characteristics also are severely modified in the stripe antiferromagnetic phase similar to BaFe

_{2}

_{2}

. Calculations of exchange parameters were performed for all the four compounds. Exchange coupling along the anti-parallel alignment of Fe spins J

_{1 a}

is larger than that for the parallel aligned spins J

_{1 b}

. A crossover between the super-exchange-driven in-plane next-nearest-neighbor exchange coupling J

_{2}

and in-plane exchange coupling J

_{1 a}

due to lanthanide substitution was found. A large super-exchange-driven next-nearest-neighbor exchange interaction is justified using the construction of 32 maximally localized Wannier functions, where the nearest-neighbor Fe-As hopping amplitudes were found to be larger than the nearest- and the next-nearest-neighbor Fe-Fe hopping amplitudes. We compare the hopping parameters in the stripe antiferromagnetic pattern with non-magnetic configuration, and increased hopping amplitude was found along the anti-parallel spin alignment with more majority-spin electrons in Fe d

_{x z}

and d

_{x y}

but not in Fe d

_{y z}

. On the other hand, the hopping amplitudes are increased in stripe antiferromagnetic phase along the parallel spin alignment with more majority-spin electrons in only Fe d

_{y z}

. This difference in hopping amplitudes in the stripe antiferromagnetic order enables more isotropic hopping. Full article

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

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14 pages, 2858 KiB

Open AccessArticle

Nonlinear Electromagnetic Properties of Thinfilm Nanocomposites (CoFeZr)_x(MgF₂)_100−x

by Evelina P. Domashevskaya, Sergey A. Ivkov, Pavel V. Seredin, Dmitry L. Goloshchapov, Konstantin A. Barkov, Stanislav V. Ryabtsev, Yrii G. Segal, Alexander V. Sitnikov and Elena A. Ganshina

Magnetochemistry 2023, 9(6), 160; https://doi.org/10.3390/magnetochemistry9060160 - 20 Jun 2023

Viewed by 1165

Abstract

The aim of this work is a comprehensive study of the effect of variable atomic composition and structural-phase state of (CoFeZr)_x(MgF₂)_100−x nanocomposites (NCs) on their nonlinear electronic and magnetic/magneto-optical properties. Micrometer-thick nanocomposite layers on the glass substrates were obtained by ion-beam sputtering of a composite target in the argon atmosphere in a wide range of compositions x = 9–51 at·%. The value of the resistive percolation threshold, x_per = 34 at·%, determined from the concentration dependencies of the electrical resistance of NCs, coincides with the beginning of nucleation of metallic nanocrystals CoFeZr in MgF₂ dielectric matrix. The absolute value of maximum magnetoresistance of NCs is 2.4% in a magnetic field of 5.5 kG at x = 25 at·%, up to the percolation threshold. Two maxima appear in the concentration dependencies of magneto-optical transversal Kerr effect, one of which, at x = 34 at·%, corresponds to the formation of CoFeZr alloy nanocrystals of a hexagonal structure, and the second one at x = 45 at·% corresponds to the phase transition of nanocrystals from a hexagonal to a cubic body-centered structure. The magnetic percolation threshold in (CoFeZr)_x(MgF₂)_100−x system at x_fm = 34 at·%, with the appearance of a hysteresis loop and a coercive force of H_c ≈ 8 Oe, coincides with the resistive percolation threshold x_per = 34 at·%. Concentration dependence of the coercive force showed that at low contents of metallic alloy x < 30 at·%, NCs are superparamagnetic (H_c = 0). With an increase of the alloy content, in the region of magnetic and resistive percolation thresholds, NCs exhibit a magnetically soft ferromagnetic character and do not change it far beyond the percolation threshold, with the maximum value of the coercive force H_c < 30 Oe. Full article

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

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12 pages, 3449 KiB

Open AccessArticle

Magnetism and Exchange Bias Properties in Ba₂ScRuO₆

by Prachi Mohanty, Sourav Marik and Ravi Prakash Singh

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

Cited by 3 | Viewed by 1603

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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7 pages, 1589 KiB

Open AccessCommunication

Effect of Co-Doping on the Magnetic Ground State of the Heavy-Fermion System CeCu₂Ge₂ Studied by Neutron Diffraction

by Rajesh Tripathi, Dmitry Khalyavin, Shivani Sharma, Devashibhai Thakarshibhai Adroja and Zakir Hossain

Magnetochemistry 2023, 9(5), 115; https://doi.org/10.3390/magnetochemistry9050115 - 26 Apr 2023

Cited by 1 | Viewed by 1466

Abstract

The antiferromagnetic phase transition of the heavy-fermion system Ce(Cu

_{1 - x}

_{x}

)

_{2}

_{2}

for x = 0.05 and 0.2, showing up in specific heat, magnetic susceptibility, and muon spin relaxation (

μ

SR) data, has been further investigated. [...] Read more.

The antiferromagnetic phase transition of the heavy-fermion system Ce(Cu

_{1 - x}

_{x}

)

_{2}

_{2}

for x = 0.05 and 0.2, showing up in specific heat, magnetic susceptibility, and muon spin relaxation (

μ

SR) data, has been further investigated. The neutron diffraction (ND) results show that Co-doping drastically reduces the moment size of Ce, without a qualitative change in the magnetic structure of the undoped compound CeCu

_{2}

_{2}

. An incommensurate magnetic propagation vector k = (0.2852, 0.2852, 0.4495) with a cycloidal magnetic structure with a Ce moment of 0.55

μ_{B}

in the

a b

-plane has been observed for x = 0.05. Although for x = 0.2 the specific heat and magnetic susceptibility data reflect a phase transition with a broad peak and the muon relaxation rate shows a sharp peak at T = 0.9 K, our ND data dismiss the possibility of a long-range magnetic ordering down to 50 mK. The ND data, along with previously reported results for x = 0.2, are interpreted in terms of the reduced ordered state magnetic moments of the Ce

^{3 +}

ion by Kondo screening and the presence of dynamical short-range magnetic correlations. Full article

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

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14 pages, 3020 KiB

Open AccessArticle

Structural, Elastic, Electronic, and Magnetic Properties of Full-Heusler Alloys Sc₂TiAl and Sc₂TiSi Using the FP-LAPW Method

by Khadejah M. Al-Masri, Mohammed S. Abu-Jafar, Mahmoud Farout, Diana Dahliah, Ahmad A. Mousa, Said M. Azar and Rabah Khenata

Magnetochemistry 2023, 9(4), 108; https://doi.org/10.3390/magnetochemistry9040108 - 16 Apr 2023

Cited by 3 | Viewed by 2374

Abstract

In this article, the structural, elastic, electronic, and magnetic characteristics of both regular and inverse Heusler alloys, Sc₂TiAl and Sc₂TiSi, were investigated using a full-potential, linearized augmented plane-wave (FP-LAPW) method, within the density functional theory. The optimized structural parameters were determined from the minimization of the total energy versus the volume of the unit cell. The band structure and DOS calculations were performed within the generalized gradient approximation (GGA) and modified Becke–Johnson approaches (mBJ-GGA), employed in the Wien2K code. The density of states (DOS) and band structure (BS) indicate the metallic nature of the regular structure of the two compounds. The total spin magnetic moments for the two compounds were consistent with the previous theoretical results. We calculated the elastic properties: bulk moduli,

B

, Poisson’s ratio,

ν

, shear modulus, S, Young’s modulus (Y), and the B/s ratio. Additionally, we used Blackman’s diagram and Every’s diagram to compare the elastic properties of the studied compounds, whereas Pugh’s and Poisson’s ratios were used in the analysis of the relationship between interatomic bonding type and physical properties. Mechanically, we found that the regular and inverse full-Heusler compounds Sc₂TiAl and Sc₂TiSi were stable. The results agree with previous studies, providing a road map for possible uses in electronic devices. Full article

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

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8 pages, 2386 KiB

Open AccessCommunication

Magnetoelectric Properties of Ni-PZT-Ni Heterostructures Obtained by Electrochemical Deposition of Nickel in an External Magnetic Field

by Natalia Poddubnaya, Dmitry Filippov, Vladimir Laletin, Aliaksei Aplevich and Kazimir Yanushkevich

Magnetochemistry 2023, 9(4), 94; https://doi.org/10.3390/magnetochemistry9040094 - 30 Mar 2023

Cited by 2 | Viewed by 1541

Abstract

This paper studied the influence of external electric and magnetic fields on the magnetoelectric properties of layered structures of metal-piezoelectric-metal. The structures under study had the shape of a square 4 mm wide and were obtained in two steps: first, by the chemical deposition of nickel with a thickness of 0.5 μm, and then by the electrochemical deposition of nickel with a thickness of 50 μm on each side onto a lead zirconate–lead titanate substrate. Electrochemical deposition was carried out without a magnetic field on both non-polarized and polarized ceramics. Electrochemical deposition was also carried out in a magnetic field on a non-polarized and polarized PZT ceramic substrate. A magnetic field of 500 Oe at electrochemical deposition was applied in all cases in the direction of structure polarization. The maximum ME voltage coefficient 300 mV/(cmOe) was obtained at transverse orientation at bias magnetic field near 20 Oe. Full article

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

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13 pages, 3734 KiB

Open AccessArticle

Magnetic and Transport Anomalies and Large Magnetocaloric Effect in Cubic R₄PtAl (R = Ho and Er)

by Kartik K. Iyer, Sudhindra Rayaprol, Ram Kumar, Shidaling Matteppanavar, Suneel Dodamani, Kalobaran Maiti and Echur V. Sampathkumaran

Magnetochemistry 2023, 9(3), 85; https://doi.org/10.3390/magnetochemistry9030085 - 20 Mar 2023

Cited by 2 | Viewed by 1683

Abstract

We report the electronic properties of R₄PtAl (R = Ho, and Er), which contains three sites for R, by the measurements of magnetization (ac and dc), heat-capacity, transport, and magnetoresistance (MR). Dc magnetization data reveal antiferromagnetic order below 19 K and 12 K in Ho and Er compounds, respectively. Additional features observed at lower temperatures (12 K for Ho₄PtAl and 5 K for Er₄PtAl) are akin to the cluster spin-glass phase. Resistivity data exhibit a weak minimum at a temperature marginally higher than their respective Néel temperature (T_N), which is unusual for such rare-earths with well-localized 4f states. Isothermal magnetization and magnetoresistance data well below T_N exhibit signatures of a subtle field-induced magnetic transition for a small magnetic field (<10 kOe). Notably, the isothermal entropy change at T_N has the largest peak value within this rare-earth family; for a field change from zero to 50 kOe, the entropy change is ~14.5 J/kg K (Ho4PtAl) and ~21.5 J/kg K (Er₄PtAl) suggesting a role of anisotropy of 4f orbital in determining this large value. The results provide some clues for the advancement of the field of magnetocaloric effect. The magnetocaloric property of Er₄PtAl is nonhysteretic, meeting a challenge to find materials with reversible magnetocaloric effect. Full article

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

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13 pages, 2401 KiB

Open AccessArticle

μSR Study of Unconventional Pairing Symmetry in the Quasi-1D Na₂Cr₃As₃ Superconductor

by Amitava Bhattacharyya, Devashibhai Adroja, Yu Feng, Debarchan Das, Pabitra Kumar Biswas, Tanmoy Das and Jun Zhao

Magnetochemistry 2023, 9(3), 70; https://doi.org/10.3390/magnetochemistry9030070 - 28 Feb 2023

Cited by 2 | Viewed by 1648

Abstract

We report the finding of a novel pairing state in a newly discovered superconductor Na

_{2}

_{3}

_{3}

. This material has a non-centrosymmetric quasi-one-dimensional crystal structure and is superconducting at

T_{C} \sim

8.0 K. We find that the magnetic [...] Read more.

We report the finding of a novel pairing state in a newly discovered superconductor Na

_{2}

_{3}

_{3}

. This material has a non-centrosymmetric quasi-one-dimensional crystal structure and is superconducting at

T_{C} \sim

8.0 K. We find that the magnetic penetration depth data suggests the presence of a nodal line

p_{z}

-wave pairing state with zero magnetic moment using transverse-field muon-spin rotation (TF-

μ

SR) measurements. The nodal gap observed in Na

_{2}

_{3}

_{3}

compound is consistent with that observed in isostructural (K,Cs)

_{2}

_{3}

_{3}

compounds using TF-

μ

SR measurements. The observed pairing state is consistent with a three-band model spin-fluctuation calculation, which reveals the

S_{z} = 0

spin-triplet pairing state with the

sin k_{z}

pairing symmetry. The long-sought search for chiral superconductivity with topological applications could be aided by such a novel triplet

S_{z} = 0

p-wave pairing state. Full article

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

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13 pages, 2475 KiB

Open AccessArticle

Insight into Unsteady Separated Stagnation Point Flow of Hybrid Nanofluids Subjected to an Electro-Magnetohydrodynamics Riga Plate

by Najiyah Safwa Khashi’ie, Norihan Md Arifin, Nur Syahirah Wahid and Ioan Pop

Magnetochemistry 2023, 9(2), 46; https://doi.org/10.3390/magnetochemistry9020046 - 31 Jan 2023

Cited by 4 | Viewed by 1530

Abstract

The main objective of this work is to analyze and compare the numerical solutions of an unsteady separated stagnation point flow due to a Riga plate using copper–alumina/water and graphene–alumina/water hybrid nanofluids. The Riga plate generates electro-magnetohydrodynamics (EMHD) which is expected to delay the boundary layer separation. The flow and energy equations are mathematically developed based on the boundary layer assumptions. These equations are then simplified with the aid of the similarity variables. The numerical results are generated by the bvp4c function and then presented in graphs and tables. The limitation of this model is the use of a Riga plate as the testing surface and water as the base fluid. The results may differ if another wall surfaces or base fluids are considered. Another limitation is the Takabi and Salehi’s correlation of hybrid nanofluid is used for the computational part. The findings reveal that dual solutions exist where the first solution is stable using the validation from stability analysis. Graphene–alumina/water has the maximum skin friction coefficient while copper–alumina/water has the maximum thermal coefficient for larger acceleration parameter. Besides, the single nanofluids (copper–water, graphene–water and alumina–water) are also tested and compared with the hybrid nanofluids. Surprisingly, graphene–water has the maximum skin friction coefficient while alumina–water has the maximum heat transfer rate. The findings are only conclusive and limited to the comparison between graphene–alumina and copper–alumina with water base fluid. The result may differ if another base fluid is used. Hence, future study is necessary to investigate the thermal progress of these hybrid nanofluids. Full article

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

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9 pages, 427 KiB

Open AccessFeature PaperArticle

Magnetic-Moment-Induced Metal–Insulator Transition in ThMnXN (X = As, P): A First Principles Study

by Smritijit Sen and Haranath Ghosh

Magnetochemistry 2023, 9(1), 16; https://doi.org/10.3390/magnetochemistry9010016 - 31 Dec 2022

Cited by 3 | Viewed by 1599

Abstract

In this work, we show magnetic-moment-induced metal–insulator transitions in ThMnXN (X = As, P) and elucidate some of the experimentally observed results obtained by Zhang et al. through a first principles density functional study. Our calculations revealed that the magnetic ground states of ThMnXN (X = As, P) are C-type anti-ferromagnets with a small energy gap (∼0.4 eV) at the Fermi level, which is in good agreement with the experiments. Our constraint moment calculations revealed local magnetic moments of 3.42

μ_{B}

and 3.63

μ_{B}

in Mn atoms for ThMnAsN and ThMnPN, respectively, which are consistent with the experimentally measured local magnetic moment for Mn atoms. An effective Hubbard U = (U − J) of 0.9 eV was applied within the GGA+U formalism in ThMnPN to reproduce the experimental Mn moment. We also found that, as the Mn moments decrease in ThMnXN (X = As, P), the energy gaps also decrease and finally disappear at Mn moment 2.7

μ_{B}

for ThMnAsN and 2.8

μ_{B}

for ThMnPN. Therefore, our results stipulate a possible metal–insulator transition in ThMnXN (X = As, P) induced by the Mn local moment. Full article

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

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11 pages, 2330 KiB

Open AccessArticle

Interrelation between the Solid-State Synthesis Conditions and Magnetic Properties of the NiCr₂O₄ Spinel

by Mikhail Cherosov, Ruslan Batulin, Airat Kiiamov, Alexey Rogov, Iskander Vakhitov, Damir Gabadullin, Dmitrii Tayurskii and Roman Yusupov

Magnetochemistry 2023, 9(1), 13; https://doi.org/10.3390/magnetochemistry9010013 - 30 Dec 2022

Cited by 4 | Viewed by 2399

Abstract

The synthesis of the NiCr₂O₄ compound with the spinel structure via the high-temperature solid-state reaction leads to different deviations of the cationic composition from the nominal depending on the atmosphere in the furnace chamber. The samples prepared from the same starting NiO and Cr₂O₃ compounds but in different atmospheres differ in phase composition and orbital and spin ordering temperatures. We find that a common route of synthesis in the air and a possible presence of the Ni₂O₃ in initial NiO lead to the incorporation of the Ni³⁺ ions into the octahedral sites regularly occupied by the Cr³⁺ ions. This results in a decrease in the orbital ordering and an increase in the Nèel temperatures. We propose that the Nèel temperature value serves as a measure of a departure of a composition from the nominal NiCr₂O₄. The lowest Nèel temperature among our series was T_N = 63 K which we consider the closest to the intrinsic quantity of the NiCr₂O₄ compound. Full article

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

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