Atomic and Molecular Magnets on Surfaces

2013 ◽  
pp. 447-470 ◽  
Author(s):  
Harald Brune ◽  
Pietro Gambardella
Keyword(s):  
Molecular Magnets

Exchange Spin Coupling from Gaussian Process Regression

2020 ◽  
Author(s):  
Marc Philipp Bahlke ◽  
Natnael Mogos ◽  
Jonny Proppe ◽  
Carmen Herrmann
Keyword(s):  
Machine Learning ◽  
Gaussian Process ◽  
Gaussian Process Regression ◽  
Molecular Magnets ◽  
Molecular Structures ◽  
Spin Coupling ◽  
Structure Property ◽  
Data Set ◽  
Uncertainty Estimates

Heisenberg exchange spin coupling between metal centers is essential for describing and understanding the electronic structure of many molecular catalysts, metalloenzymes, and molecular magnets for potential application in information technology. We explore the machine-learnability of exchange spin coupling, which has not been studied yet. We employ Gaussian process regression since it can potentially deal with small training sets (as likely associated with the rather complex molecular structures required for exploring spin coupling) and since it provides uncertainty estimates (“error bars”) along with predicted values. We compare a range of descriptors and kernels for 257 small dicopper complexes and find that a simple descriptor based on chemical intuition, consisting only of copper-bridge angles and copper-copper distances, clearly outperforms several more sophisticated descriptors when it comes to extrapolating towards larger experimentally relevant complexes. Exchange spin coupling is similarly easy to learn as the polarizability, while learning dipole moments is much harder. The strength of the sophisticated descriptors lies in their ability to linearize structure-property relationships, to the point that a simple linear ridge regression performs just as well as the kernel-based machine-learning model for our small dicopper data set. The superior extrapolation performance of the simple descriptor is unique to exchange spin coupling, reinforcing the crucial role of choosing a suitable descriptor, and highlighting the interesting question of the role of chemical intuition vs. systematic or automated selection of features for machine learning in chemistry and material science.

scholarly journals Decoherence measurements in crystals of molecular magnets

2019 ◽  
Vol 99 (18) ◽  
Author(s):  
Gheorghe Taran ◽  
Edgar Bonet ◽  
Wolfgang Wernsdorfer
Keyword(s):  
Molecular Magnets

Mixed-valence molecular magnets based on building block: Structures, magnetic properties and DFT analyses

Polyhedron ◽  
2007 ◽  
Vol 26 (9-11) ◽  
pp. 1781-1786 ◽  
Author(s):  
Y.C. Chen ◽  
G.X. Liu ◽  
P.F. Wang ◽  
H. Xu ◽  
X.M. Ren ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Building Block ◽  
Mixed Valence ◽  
Molecular Magnets ◽  
Block Structures

scholarly journals XXXIX.—Magnetic Quality in the most open Cubic Arrangement of Molecular Magnets.

1908 ◽  
Vol 28 ◽  
pp. 643-651 ◽  
Author(s):  
W. Peddie
Keyword(s):  
Magnetic Properties ◽  
Molecular Magnets ◽  
Molecular Arrangement ◽  
Good Agreement

In a former paper (Proc. R.S.E., 1905) an investigation was given of the magnetic properties of the closest packed homogeneous cubic arrangement of molecular magnets, and it was found that the results were in good agreement with the observed properties of crystals of magnetite. It was also suggested that a parallel investigation of other cubic arrangements might lead to a discrimination of molecular arrangement, so far as the magnetic constituents are concerned, in actual crystals. To settle this point, if possible, the present investigation was undertaken.

scholarly journals Dragging Human Mesenchymal Stem Cells with the Aid of Supramolecular Assemblies of Single-Walled Carbon Nanotubes, Molecular Magnets, and Peptides in a Magnetic Field

2015 ◽  
Vol 2015 ◽  
pp. 1-9
Author(s):  
Ana Cláudia C. de Paula ◽  
Gustavo A. M. Sáfar ◽  
Alfredo M. Góes ◽  
Marcelo P. Bemquerer ◽  
Marcos A. Ribeiro ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Carbon Nanotubes ◽  
Stem Cells ◽  
Supramolecular Assembly ◽  
Single Walled Carbon Nanotubes ◽  
Molecular Magnets ◽  
Multiwalled Carbon ◽  
Blood Capillaries ◽  
Single Walled Carbon ◽  
Walled Carbon Nanotubes

Human adipose-derived stem cells (hASCs) are an attractive cell source for therapeutic applicability in diverse fields for the repair and regeneration of damaged or malfunctioning tissues and organs. There is a growing number of cell therapies using stem cells due to their characteristics of modulation of immune system and reduction of acute rejection. So a challenge in stem cells therapy is the delivery of cells to the organ of interest, a specific site. The aim of this paper was to investigate the effects of a supramolecular assembly composed of single-walled carbon nanotubes (SWCNT), molecular magnets (lawsone-Co-phenanthroline), and a synthetic peptide (FWYANHYWFHNAFWYANHYWFHNA) in the hASCs cultures. The hASCs were isolated, characterized, expanded, and cultured with the SWCNT supramolecular assembly (SWCNT-MA). The assembly developed did not impair the cell characteristics, viability, or proliferation. During growth, the cells were strongly attached to the assembly and they could be dragged by an applied magnetic field of less than 0.3 T. These assemblies were narrower than their related allotropic forms, that is, multiwalled carbon nanotubes, and they could therefore be used to guide cells through thin blood capillaries within the human body. This strategy seems to be useful as noninvasive and nontoxic stem cells delivery/guidance and tracking during cell therapy.

scholarly journals Effects of Arbitrarily Directed Field on Spin Phase Oscillations in Biaxial Molecular Magnets

2001 ◽  
Vol 35 (6) ◽  
pp. 751-758
Author(s):  
Hu Hui ◽  
Zhu Jia-Lin ◽  
Lü Rong ◽  
Xiong Jia-Jiong
Keyword(s):  
Molecular Magnets

scholarly journals The atomic process in ferromagnetic Induction

1922 ◽  
Vol 100 (706) ◽  
pp. 449-460 ◽  
Keyword(s):  
Magnetic Particles ◽  
Strong Field ◽  
Molecular Magnets ◽  
Magnetic Element ◽  
Atomic Process ◽  
Dissipation Of Energy ◽  
Unstable Phase ◽  
Complete Alignment ◽  
The Stability ◽  
Ferromagnetic Substance

The object of this paper is to amend, in an important particular, the theory of ferromagnetic induction put forward by me more than 30 years ago, and to describe a new model. That theory was itself a modification of the earlier theory of Weber. To Weber is due the fundamental notion that a substance contains minute particles, each of which acts as a magnet, and that in the process of magnetising a ferromagnetic substance these are turned into more or less complete alignment. The ultimate magnetic particles use to be called “molecular magnets”: we now recognise them as attributes of the atom, not of the molecule, and (in all probability) they derive their magnetic moment from the circulation of electricity in electron orbits or in ring electrons. What turns is not the molecule nor the atom, but something within the atom. The characteristics which distinguish ferromagnetic substances from other paramagnetics are: (1) the much larger amount of magnetism they can acquire under the action of an impressed field; (2) the fact that the acquired magnetism tends towards a saturation limit when the field is progressively increased; (3) the fact that the acquired magnetism shows hysteresis with respect to variations of the field, except in certain small initial changes. Weber’s theory explained (1) and (2). My modification of it explained, in addition, (3) as an effect of the irreversible action which occurs when the equilibrium of a magnetic element becomes unstable through change in the externally impressed magnetic force, and it swings over, with dissipation of energy, into a new position of stability. The stability in both positions is sufficiently explained by magnetic forces only. In breaking away from one stable position it is deflected at first in a quasi­-elastic (reversible) manner until the external force reaches a certain value at which the equilibrium is upset. The essence of hysteresis is the turning from one position of stability to another, through a region of instability. If the conditions are such that there is no unstable phase in the turning, then there is no dissipation of energy, and consequently no hysteresis. This occurs in very feeble magnetisation, when the deflections are reversible; it also occurs if the piece be caused to rotate in a field of great strength. J. Swinburne pointed out that, as a consequence of my theory, hysteresis should vanish when a cylinder of ferromagnetic metal is rotated in a very strong field, and this curious result was confirmed experimentally by F. G. Baily.

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