Magnetic ordering in submonolayer Mn films on fee Co(001) and the effects of oxidation

1997 ◽  
Vol 475 ◽  
Author(s):  
W.L. O'Brien ◽  
B.P. Tonner
Keyword(s):  
Magnetic Coupling ◽  
Magnetic Ordering ◽  
Magnetization Direction ◽  
Theoretical Predictions ◽  
Oriented Parallel

Submonolayer films of Mn grown on fcc Co(001) are ferromagnetically ordered with the magnetization direction oriented parallel to the Co substrate magnetization. After exposure to oxygen the Mn atoms remain ferromagnetically ordered but their magnetization direction rotates 180 degrees and is now aligned antiparallel to the Co magnetization. This behavior in magnetic coupling between the Mn and Co films is not consistent with recent theoretical predictions.

scholarly journals Lattice disorder effect on magnetic ordering of iron arsenides

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Athena S. Sefat ◽  
Xiaoping P. Wang ◽  
Yaohua Liu ◽  
Qiang Zou ◽  
Mimgming Fu ◽  
...  
Keyword(s):  
Magnetic Coupling ◽  
Magnetic Ordering ◽  
Structural Features ◽  
Lattice Parameter ◽  
Chemical Compositions ◽  
Lattice Disorder ◽  
Local Lattice ◽  
Higher Temperature ◽  
Disordered Crystal ◽  
Planar Strain

AbstractThis study investigates magnetic ordering temperature in nano- and mesoscale structural features in an iron arsenide. Although magnetic ground states in quantum materials can be theoretically predicted from known crystal structures and chemical compositions, the ordering temperature is harder to pinpoint due to potential local lattice variations that calculations may not account for. In this work we find surprisingly that a locally disordered material can exhibit a significantly larger Néel temperature (TN) than an ordered material of precisely the same chemical stoichiometry. Here, a EuFe2As2 crystal, which is a ‘122’ parent of iron arsenide superconductors, is found through synthesis to have ordering below TN = 195 K (for the locally disordered crystal) or TN = 175 K (for the ordered crystal). In the higher TN crystals, there are shorter planar Fe-Fe bonds [2.7692(2) Å vs. 2.7745(3) Å], a randomized in-plane defect structure, and diffuse scattering along the [00 L] crystallographic direction that manifests as a rather broad specific heat peak. For the lower TN crystals, the a-lattice parameter is larger and the in-plane microscopic structure shows defect ordering along the antiphase boundaries, giving a larger TN and a higher superconducting temperature (Tc) upon the application of pressure. First-principles calculations find a strong interaction between c-axis strain and interlayer magnetic coupling, but little impact of planar strain on the magnetic order. Neutron single-crystal diffraction shows that the low-temperature magnetic phase transition due to localized Eu moments is not lattice or disorder sensitive, unlike the higher-temperature Fe sublattice ordering. This study demonstrates a higher magnetic ordering point arising from local disorder in 122.

scholarly journals Data-driven studies of magnetic two-dimensional materials

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Trevor David Rhone ◽  
Wei Chen ◽  
Shaan Desai ◽  
Steven B. Torrisi ◽  
Daniel T. Larson ◽  
...  
Keyword(s):  
Machine Learning ◽  
Dft Calculations ◽  
Density Functional ◽  
Magnetic Coupling ◽  
Magnetic Ordering ◽  
Magnetic Behavior ◽  
Data Driven ◽  
Two Dimensional ◽  
Computationally Efficient ◽  
Data Driven Approach

Abstract We use a data-driven approach to study the magnetic and thermodynamic properties of van der Waals (vdW) layered materials. We investigate monolayers of the form $$\hbox {A}_2\hbox {B}_2\hbox {X}_6$$ A 2 B 2 X 6 , based on the known material $$\hbox {Cr}_2\hbox {Ge}_2\hbox {Te}_6$$ Cr 2 Ge 2 Te 6 , using density functional theory (DFT) calculations and machine learning methods to determine their magnetic properties, such as magnetic order and magnetic moment. We also examine formation energies and use them as a proxy for chemical stability. We show that machine learning tools, combined with DFT calculations, can provide a computationally efficient means to predict properties of such two-dimensional (2D) magnetic materials. Our data analytics approach provides insights into the microscopic origins of magnetic ordering in these systems. For instance, we find that the X site strongly affects the magnetic coupling between neighboring A sites, which drives the magnetic ordering. Our approach opens new ways for rapid discovery of chemically stable vdW materials that exhibit magnetic behavior.

Tuning of Gadolinium Based Compounds for Potential Application in Self-Controlled Hyperthermia Treatment of Cancer

2010 ◽  
Vol 442 ◽  
pp. 242-249 ◽  
Author(s):  
S.N. Ahmad ◽  
S.A. Shaheen
Keyword(s):  
Magnetic Materials ◽  
Magnetic Coupling ◽  
Magnetic Ordering ◽  
Invasive Technique ◽  
Hyperthermia Treatment ◽  
Non Invasive ◽  
Ferromagnetic Bulk ◽  
Constituent Elements ◽  
Curie Temperature Tc ◽  
Potential Use

We report on the synthesis and investigation of magnetic properties of several new Gd based alloys suitable for their potential use in self-controlled hyperthermia treatment of cancer. Self-controlled hyperthermia is a non-invasive technique that employs heating of magnetic materials (ferromagnetic bulk sized thermo-seeds or magnetic nanoparticles) in a. c. fields to cure cancer cells. Magnetic materials with Curie temperature (Tc) in the range of 40-46oC are desired, as decreased magnetic coupling in paramagnetic regime (above Tc) provides a safeguard against overheating of normal cells. The need for developing such materials was dictated by the lack of existing magnetic materials with magnetic ordering temperature in the suitable range of hyperthermia applications. This study shows that these materials have high magnetization values and their Tc values can be varied linearly over a broad range by adjusting the composition of the constituent elements.

Hard versus soft: zero-field dinuclear Dy(iii) oxygen bridged SMM and theoretical predictions of the sulfur and selenium analogues

2019 ◽  
Vol 48 (9) ◽  
pp. 2872-2876 ◽  
Author(s):  
Kuduva R. Vignesh ◽  
Dimitris I. Alexandropoulos ◽  
Brian S. Dolinar ◽  
Kim R. Dunbar
Keyword(s):  
Magnetic Anisotropy ◽  
Magnetic Coupling ◽  
Magnetic Behavior ◽  
Dinuclear Complexes ◽  
Zero Field ◽  
Theoretical Predictions

Structural, magnetic and CASSCF studies were used to quantify the observed magnetic behavior of two lanthanide dinuclear complexes. The effect of soft-donor atoms was probed in order to ascertain the effect of magnetic anisotropy combined with magnetic coupling in dinuclear SMMs.

scholarly journals Tailoring the magnetic ordering of the Cr4O5/Fe(001) surface via a controlled adsorption of C60 organic molecules.

2020 ◽  
Author(s):  
Federico Orlando ◽  
Guido Fratesi ◽  
Giovanni Onida ◽  
Simona Achilli
Keyword(s):  
Density Functional ◽  
Organic Molecules ◽  
Molecular Layer ◽  
Magnetic Coupling ◽  
Magnetic Ordering ◽  
Magnetic Interaction ◽  
High Symmetry ◽  
Two Dimensional ◽  
Adsorption Sites ◽  
Controlled Adsorption

We analyse the spinterface formed by a C60 molecular layer on a Fe(001) surface covered by a two-dimensional Cr4O5 layer. We consider different geometries, by combining the high symmetry adsorption sites of the surface with three possible orientations of the molecules in a fully relaxed Density Functional Theory calculation.We show that the local hybridization between the electronic states of the Cr4O5 layer and those of the organic molecules is able to modify the magnetic coupling of the Cr atoms. Both the intra-layer and the inter-layer magnetic interaction is indeed driven by O atoms of the two-dimensional oxide. We demonstrate that the C60 adsorption on the energetically most stable site turns the ferromagnetic intra-layer coupling into an antiferromagnetic one, and that antiferromagnetic to ferromagnetic switching and spin patterning of the substrate are made possible by adsorption on other sites.

Tailor-Made Strong Exchange Magnetic Coupling through Very Long Bridging Ligands:  Theoretical Predictions

2003 ◽  
Vol 42 (16) ◽  
pp. 4881-4884 ◽  
Author(s):  
Eliseo Ruiz ◽  
Antonio Rodríguez-Fortea ◽  
Santiago Alvarez
Keyword(s):  
Magnetic Coupling ◽  
Bridging Ligands ◽  
Theoretical Predictions ◽  
Strong Exchange

scholarly journals Suppressed-moment 2-k order in the canonical frustrated antiferromagnet Gd2Ti2O7

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Joseph A. M. Paddison ◽  
Georg Ehlers ◽  
Andrew B. Cairns ◽  
Jason S. Gardner ◽  
Oleg A. Petrenko ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Spin Wave ◽  
Inelastic Neutron Scattering ◽  
Magnetic Moments ◽  
Magnetic Ordering ◽  
Thermal Fluctuation ◽  
Inelastic Neutron ◽  
Scattering Measurements ◽  
Theoretical Predictions ◽  
Powder Samples

AbstractIn partially ordered magnets, order and disorder coexist in the same magnetic phase, distinct from both spin liquids and spin solids. Here, we determine the nature of partial magnetic ordering in the canonical frustrated antiferromagnet Gd2Ti2O7, in which Gd3+ spins occupy a pyrochlore lattice. Using single-crystal neutron-diffraction measurements in applied magnetic field, magnetic symmetry analysis, inelastic neutron-scattering measurements, and spin-wave modeling, we show that its low-temperature magnetic structure involves two propagation vectors (2-k structure) with suppressed ordered magnetic moments and enhanced spin-wave fluctuations. Our experimental results are consistent with theoretical predictions of thermal fluctuation-driven order in Gd2Ti2O7, and reveal that inelastic neutron-scattering measurements on powder samples can solve the longstanding problem of distinguishing single-k and multi-k magnetic structures.

Structural Characterization of the Chromium-Iron Alloy Formed by Thermal Diffusion Processes

2013 ◽  
Vol 651 ◽  
pp. 284-288 ◽  
Author(s):  
Roberto Baca Arroyo
Keyword(s):  
Thermal Diffusion ◽  
Diffusion Processes ◽  
Iron Alloy ◽  
Magnetic Coupling ◽  
Magnetic Ordering ◽  
X Ray Diffraction ◽  
Lattice Constants ◽  
Air Atmosphere ◽  
Direct Band

We have investigated the chromium-iron alloy and compared it to the oxides α-Fe2O3 (Eg = 4.8eV) and α-Cr2O3 (Eg = 2.1eV). It is known that α-Cr2O3 and α-Fe2O3 both adopt a corundum-type structure, but display differences in the lattice constants, direct band gap, and magnetic ordering of the cations. The chromium-iron alloy was synthesized by thermal diffusion processes of both chromium and iron thin-films in air atmosphere conditions. We have studied the elastic distortions related to nature of the relative strains as well as magnetic coupling between Fe and Cr from the X-ray diffraction studies.

scholarly journals Anomalous magnetic ordering in PrBa2Cu3O7−y single crystals: evidence for magnetic coupling between the Cu and Pr sublattices

1999 ◽  
Vol 312 (3-4) ◽  
pp. 233-238 ◽  
Author(s):  
V.N Narozhnyi ◽  
D Eckert ◽  
K.A Nenkov ◽  
G Fuchs ◽  
T.G Uvarova ◽  
...  
Keyword(s):  
Single Crystals ◽  
Magnetic Coupling ◽  
Magnetic Ordering

Mechanical-Magnetic Coupling Analysis of a Novel Large Stroke Penta-Stable Mechanism Possessing Multistability Transforming Capability

2014 ◽  
Vol 6 (3) ◽  
Author(s):  
Jian Zhao ◽  
Yongcun Zhang ◽  
Yu Huang ◽  
Shutian Liu ◽  
Guoxi Chen ◽  
...  
Keyword(s):  
Magnetic Coupling ◽  
Design Criterion ◽  
Variation Principle ◽  
Stable States ◽  
Magnetization Direction ◽  
Stable Mechanism ◽  
Element Simulation ◽  
Nonlinear Force ◽  
The Stability ◽  
Energy Based Design

Considering the nonlinear mechanical-magnetic coupling effects, an accurate mathematical model was established for analyzing large stroke penta-stable mechanism possessing multistability transforming capability, with which the mechanism can be switched from pentastability to quadristability. The multistability with any number of stable states can be achieved by integrating spatially arranged magnets and large deformation beams as the fundamental energy storage elements to maintain stable states. By theoretically analyzing the influence of the large mechanical deformation on the magnetic field distribution and system energy, the nonlinear force–displacement characteristics of the multistable mechanism were obtained numerically, which were in good agreement with those obtained by experiments and finite element simulation. Then, an energy-based design criterion for magnetic-mechanical multistable mechanisms was proposed according to the stability theory and energy variation principle. In addition, the multistable transformability was theoretically analyzed, which can transform the proposed mechanism from penta-stability to quadristability by only changing the magnetization direction of moving magnets without varying the structure parameters.

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