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Crystals
Special Issues
Magnetism in Low Dimensional Structures
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Magnetism in Low Dimensional Structures

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".

Deadline for manuscript submissions: closed (30 April 2020) | Viewed by 11240

Special Issue Editors

Prof. Dr. Abdellah Lisfi

E-Mail Website
Guest Editor
Department of Physics, Morgan State University, Baltimore, MD 21251, USA
Interests: magnetic materials; anisotropy; magnetostriction; magnetic sensing; magnetic imaging
Dr. Sabin Pokharel

E-Mail Website
Guest Editor
Department of Physics, Morgan State University, Baltimore, MD, USA
Interests: Magnetism in low dimensional structures, Highly magnetostrictive ceramics and metallic alloys, Permanent magnets and large anisotropy ferromagnets, Multifunctional materials, Nanostructured materials, Magnetic imaging, Surface magnetism and magneto-optic effects

Special Issue Information

Dear Colleagues,

Magnetism is one of the fascinating research topics in condensed matter, and its importance to our modern society is well reflected in the wide range of applications of magnetic materials in different technology sectors, such as data storage, permanent magnet, sensing, and actuating. Reducing dimensions of magnetic materials is generally motivated by scientific curiosity as well as technological demands, since modern technology has been shifting toward device miniaturization with a high performance. Low-dimensional magnets may include thin films, multilayered structures, nanowires, and nanoparticles and may offer superior performances over traditional materials. Their enhanced properties are mainly due to the surface effects, which are promoted through the large number of surface atoms in comparison to volume atoms, and the Physics phenomena that arise at the nanolevel. Among the spectacular phenomena found to manifest in low-dimensional magnets are: (1) giant anisotropy in ultra-thin film media generated by the interface and the broken symmetry; (2) the giant magnetoresistance (GMR) effect observed in multilayered structures; (3) the biasing effect produced by the interaction between ferromagnetic and antiferromagnetic layers in bilayer systems; (4) the tunneling magnetoresistance (TMR) effect generated in two-dimensional systems with ferromagnetic electrodes spaced by a very thin insulator layer; and (5) the development of a spin valve transistor (SVT), which integrates both a ferromagnet and semiconductor with large magnetoresistance response. The discovery of GMR and TMR has led to the emergence of a new research field called spintronics that has revolutionized the computer industry. Although a great progress has been achieved in low-dimensional magnets, there is still room for new discoveries that can impact our society and promote knowledge in this science field due to the spectacular advances in the tools of fabrication and characterization of nanostructures.

Prof. Abdellah Lisfi
Dr. Sabin Pokharel
Guest Editor

Manuscript Submission Information

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. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • thin film
  • epitaxial heterostructure
  • magnetic anisotropy
  • magnetic nanowires
  • magnetic nanoparticles
  • magnetic multilayer

Published Papers (3 papers)

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Research

17 pages, 4339 KiB  
Article
Anatomy of Magnetic Anisotropy and Voltage-Controlled Magnetic Anisotropy in Metal Oxide Heterostructure from First Principles
by Indra Pardede, Daiki Yoshikawa, Tomosato Kanagawa, Nurul Ikhsan, Masao Obata and Tatsuki Oda
Crystals 2020, 10(12), 1118; https://doi.org/10.3390/cryst10121118 - 8 Dec 2020
Cited by 1 | Viewed by 2685
Abstract
Voltage control of magnetic anisotropy (VCMA) is one of the promising approaches for magnetoelectric control of magnetic tunnel junction (MTJ). Here, we systematically calculated the magnetic anisotropy (MA) and the VCMA energies in the well-known MTJ structure consisting of Fe/MgO interface with Cr [...] Read more.
Voltage control of magnetic anisotropy (VCMA) is one of the promising approaches for magnetoelectric control of magnetic tunnel junction (MTJ). Here, we systematically calculated the magnetic anisotropy (MA) and the VCMA energies in the well-known MTJ structure consisting of Fe/MgO interface with Cr buffer layer. In this calculation, we investigated an alloying between Fe and Cr and a strain effect. We used a spin density functional approach which includes both contributions from magnetocrystalline anisotropy energy (MCAE) originating from spin–orbit coupling and shape magnetic anisotropy energy from spin dipole–dipole interaction. In the present approach, the MCAE part, in addition to a common scheme of total energy, was evaluated using a grand canonical force theorem scheme. In the latter scheme, atom-resolved and k-resolved analyses for MA and VCMA can be performed. At first, we found that, as the alloying is introduced, the perpendicular MCAE increases by a factor of two. Next, as the strain is introduced, we found that the MCAE increases with increasing compressive strain with the maximum value of 2.2 mJ/m2. For the VCMA coefficient, as the compressive strain increases, the sign becomes negative and the absolute value becomes enhanced to the number of 170 fJ/Vm. By using the atom-resolved and k-resolved analyses, we clarified that these enhancements of MCAE and VCMA mainly originates from the Fe interface with MgO (Fe1) and are located at certain lines in the two dimensional Brillouin zone. The findings on MCAE and VCMA are fully explained by the spin-orbit couplings between the certain d-orbital states in the second-order perturbation theory. Full article
(This article belongs to the Special Issue Magnetism in Low Dimensional Structures)
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11 pages, 26567 KiB  
Article
Fabrication of CoFe2O4 Nanowire Using a Double-Pass Porous Alumina Template with a Large Range of Pore Diameters
by Wei Chen, Hui Zheng, Dongping Hu, Qiong Wu, Peng Zheng, Liang Zheng and Yang Zhang
Crystals 2020, 10(4), 331; https://doi.org/10.3390/cryst10040331 - 23 Apr 2020
Cited by 4 | Viewed by 3248
Abstract
In this work, CoFe2O4 nanowire was fabricated by using a self-designed double-pass porous alumina template. The double-pass porous alumina template was prepared by a two-step oxidation method using a mixed acid (phosphoric acid and oxalic acid) electrolyte and polymethyl methacrylate [...] Read more.
In this work, CoFe2O4 nanowire was fabricated by using a self-designed double-pass porous alumina template. The double-pass porous alumina template was prepared by a two-step oxidation method using a mixed acid (phosphoric acid and oxalic acid) electrolyte and polymethyl methacrylate (PMMA) filler. The combustion of aluminum foil at a high voltage has been effectively resolved by using this mixed acid electrolyte. Additionally, the range of pore diameters has been obviously increased to 230–400 nm by using PMMA as the filler, which can prevent contact between the pore and solution when removing the barrier layer. Subsequently, CoFe2O4 ferrite nanowire arrays were successfully fabricated into the double-pass porous alumina template by an electrochemical deposition method, and show an anisotropic feature of magnetic properties. Full article
(This article belongs to the Special Issue Magnetism in Low Dimensional Structures)
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9 pages, 2105 KiB  
Article
Simple Synthesis of NdFeO3 Nanoparticles By the Co-Precipitation Method Based on a Study of Thermal Behaviors of Fe (III) and Nd (III) Hydroxides
by Tien A. Nguyen, V. Pham, Thanh L. Pham, Linh T. Tr. Nguyen, I. Ya. Mittova, V. O. Mittova, Lan N. Vo, Bich Tram T. Nguyen, Vuong X. Bui and E. L. Viryutina
Crystals 2020, 10(3), 219; https://doi.org/10.3390/cryst10030219 - 20 Mar 2020
Cited by 39 | Viewed by 4784
Abstract
In this study, a nanostructured NdFeO3 material was synthesized via a simple process of the hydrolysis of Nd (III) and Fe (III) cations in hot water with 5% NaOH as a precipitating agent. According to the results of the thermal behaviors of [...] Read more.
In this study, a nanostructured NdFeO3 material was synthesized via a simple process of the hydrolysis of Nd (III) and Fe (III) cations in hot water with 5% NaOH as a precipitating agent. According to the results of the thermal behaviors of each hydroxide, either containing Fe (III) or Nd (III), the perovskite type of neodymium orthoferrite NdFeO3 was simply synthesized by annealing a mixture of Fe (III) and Nd (III) hydroxides at 750 °C. The nanostructured NdFeO3 was obtained in spherical granules with diameters of around 30 nm. The magnetic properties of the material were a coercive force (Hc) of 136.76 Oe, a remanent magnetization (Mr) of 0.68 emu·g–1, and a saturation magnetization (Ms) of 0.79 emu·g–1. Full article
(This article belongs to the Special Issue Magnetism in Low Dimensional Structures)
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