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Potential Energy Surfaces and Rates of Spin Transitions

  • Pavel F. Bessarab EMAIL logo , Valery M. Uzdin and Hannes Jónsson
Published/Copyright: July 8, 2013
Zeitschrift für Physikalische Chemie
From the journal Zeitschrift für Physikalische Chemie Volume 227 Issue 11

Abstract

The stability of magnetic states and the mechanism for magnetic transitions can be analyzed in terms of the shape of the energy surface, which gives the energy as a function of the angles determining the orientation of the magnetic moments. Minima on the energy surface correspond to stable or metastable magnetic states and can represent parallel, antiparallel or, more generally, non-collinear arrangements. A rate theory has been developed for systems with arbitrary number, N, of magnetic moments, to estimate the thermal stability of magnetic states and the mechanism for magnetic transitions based on a transition state theory approach. The minimum energy path on the 2N-dimensional energy surface is determined to identify the transition mechanism and estimate the activation energy barrier. A pre-exponential factor in the rate expression is obtained from the Landau–Lifshitz–Gilbert equation for spin dynamics. The velocity is zero at saddle points so it is particularly important in this context to realize that the transition state is a dividing surface with 2N − 1 degrees of freedom, not just a saddle point. An application of this rate theory to nanoscale Fe islands on W(110) has revealed how the transition mechanism and rate depend on island shape and size. Qualitative agreement is obtained with experimental measurements both for the activation energy and the pre-exponential factor. In particular, a distinct maximum is observed in the pre-exponential factor for islands where two possible transition mechanisms are competing: Uniform rotation and the formation of a temporary domain wall. The entropy of the transition state is enhanced for those islands making the pre-exponential factor more than an order of magnitude larger than for islands were only the uniform rotation is viable.

Keywords: Rate Theory; Spin Transitions; Magnetic Memory; Magnetic Nano-Islands; Potential Energy Surface
Received: 2013-2-21
Published Online: 2013-7-8
Published in Print: 2013-11-1

© 2013 by Walter de Gruyter Berlin Boston

Articles in the same Issue

  1. Masthead
  2. Masthead
  3. Editorial
  4. Milestones in Physical Chemistry (I) – A Special Issue Honoring the Seminal Work of Henry Eyring and Michael Polanyi
  5. International Collaborations are nothing new... and sometimes they are simply amazing
  6. Personal Perspective
  7. A Comment on Henry Eyring
  8. Comment
  9. Michael Polanyi, the Scientist
  10. Historical Paper
  11. On Simple Gas Reactions
  12. Feature Article
  13. Probing Quantum Dynamics of Elementary Chemical Reactions via Accurate Potential Energy Surfaces
  14. Elementary Gas Phase Reactions
  15. Experimental and Theoretical Studies of Roaming Dynamics in the Unimolecular Dissociation of CH3NO2 to CH3O + NO
  16. Simultaneous Measurement of Reactive and Inelastic Scattering: Differential Cross Section of the H + HD → HD(v′, j′) + H Reaction
  17. The Decomposition of Hydrazine in the Gas Phase and over an Iridium Catalyst
  18. A Theoretical Study of the X-Abstraction Reactions (X = H, Br, or I) from CH2IBr by OH Radicals: Implications for Atmospheric Chemistry
  19. Models for Intrinsic Non-RRKM Dynamics. Decomposition of the SN2 Intermediate Cl––CH3Br
  20. Chemical Reactions at Surfaces
  21. Electronic Excitations in the Course of the Reaction of H with Coinage and Noble Metal Surfaces: A Comparison
  22. 7D Quantum Dynamics of H2 Scattering from Cu(111): The Accuracy of the Phonon Sudden Approximationy
  23. Exploring Pathways of Photoaddition Reactions by Artificial Force Induced Reaction Method: A Case Study on the Paternò–Büchi Reaction
  24. Kinetic Prefactors of Reactions on Solid Surfaces
  25. Electron-Transfer-Induced Dissociation of H2 on Gold Nanoparticles: Excited-State Potential Energy Surfaces via Embedded Correlated Wavefunction Theory
  26. Toward Detection of Electron-Hole Pair Excitation in H-atom Collisions with Au(111): Adiabatic Molecular Dynamics with a Semi-Empirical Full-Dimensional Potential Energy Surface
  27. Initial Sticking Coefficient of H2 on the Pd–Cu(111) Surface Alloy at very Low Coverages
  28. Catalyzed Surface-Aligned Reaction, H(ad) + H2(ad) = H2(g) + H(ad) on Coinage Metals
  29. Nitrogen Scattering at Ru(0001) Surfaces
  30. Ready, Set and no Action: A Static Perspective on Potential Energy Surfaces commonly used in Gas-Surface Dynamics
  31. Reactions in Clusters
  32. Potential Energy Surfaces and Rates of Spin Transitions
  33. A Full-Dimensional Neural Network Potential-Energy Surface for Water Clusters up to the Hexamer
  34. Embedded Cluster Models for Reactivity of the Hydrated Electron
  35. Novel Experimenta Methods
  36. Stark Deceleration of NO Radicals
  37. A Forty-Segment Molecular Synchrotron
https://doi.org/10.1524/zpch.2013.0403
Keywords for this article
Rate Theory; Spin Transitions; Magnetic Memory; Magnetic Nano-Islands; Potential Energy Surface

Articles in the same Issue

  1. Masthead
  2. Masthead
  3. Editorial
  4. Milestones in Physical Chemistry (I) – A Special Issue Honoring the Seminal Work of Henry Eyring and Michael Polanyi
  5. International Collaborations are nothing new... and sometimes they are simply amazing
  6. Personal Perspective
  7. A Comment on Henry Eyring
  8. Comment
  9. Michael Polanyi, the Scientist
  10. Historical Paper
  11. On Simple Gas Reactions
  12. Feature Article
  13. Probing Quantum Dynamics of Elementary Chemical Reactions via Accurate Potential Energy Surfaces
  14. Elementary Gas Phase Reactions
  15. Experimental and Theoretical Studies of Roaming Dynamics in the Unimolecular Dissociation of CH3NO2 to CH3O + NO
  16. Simultaneous Measurement of Reactive and Inelastic Scattering: Differential Cross Section of the H + HD → HD(v′, j′) + H Reaction
  17. The Decomposition of Hydrazine in the Gas Phase and over an Iridium Catalyst
  18. A Theoretical Study of the X-Abstraction Reactions (X = H, Br, or I) from CH2IBr by OH Radicals: Implications for Atmospheric Chemistry
  19. Models for Intrinsic Non-RRKM Dynamics. Decomposition of the SN2 Intermediate Cl––CH3Br
  20. Chemical Reactions at Surfaces
  21. Electronic Excitations in the Course of the Reaction of H with Coinage and Noble Metal Surfaces: A Comparison
  22. 7D Quantum Dynamics of H2 Scattering from Cu(111): The Accuracy of the Phonon Sudden Approximationy
  23. Exploring Pathways of Photoaddition Reactions by Artificial Force Induced Reaction Method: A Case Study on the Paternò–Büchi Reaction
  24. Kinetic Prefactors of Reactions on Solid Surfaces
  25. Electron-Transfer-Induced Dissociation of H2 on Gold Nanoparticles: Excited-State Potential Energy Surfaces via Embedded Correlated Wavefunction Theory
  26. Toward Detection of Electron-Hole Pair Excitation in H-atom Collisions with Au(111): Adiabatic Molecular Dynamics with a Semi-Empirical Full-Dimensional Potential Energy Surface
  27. Initial Sticking Coefficient of H2 on the Pd–Cu(111) Surface Alloy at very Low Coverages
  28. Catalyzed Surface-Aligned Reaction, H(ad) + H2(ad) = H2(g) + H(ad) on Coinage Metals
  29. Nitrogen Scattering at Ru(0001) Surfaces
  30. Ready, Set and no Action: A Static Perspective on Potential Energy Surfaces commonly used in Gas-Surface Dynamics
  31. Reactions in Clusters
  32. Potential Energy Surfaces and Rates of Spin Transitions
  33. A Full-Dimensional Neural Network Potential-Energy Surface for Water Clusters up to the Hexamer
  34. Embedded Cluster Models for Reactivity of the Hydrated Electron
  35. Novel Experimenta Methods
  36. Stark Deceleration of NO Radicals
  37. A Forty-Segment Molecular Synchrotron
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