Magnetic properties of 2D nano-islands I

Ising spin model

A. Khater, M. Abou Ghantous

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

An Ising spin effective field theory (EFT) is developed as a framework for a detailed analysis of the magnetic properties of two-dimensional (2D) nano-islands on a nonmagnetic substrate with an out of plane magnetization. The Hamiltonian with nearest neighbor exchange interactions and single-atom magnetic anisotropy defines the ground state. The calculation yields the single site spin correlations, the magnetizations, and the isothermal susceptibilities for the core and periphery domains, and the island core phase diagrams. The choice of a spin S=1 for the atoms permits the analysis of the effects of spin fluctuations via the single site spin correlations. In particular we investigate the effects due to the different anisotropies and reduced dimensionalities for the core and periphery domains. The present model calculations are developed for different 2D nano-islands lattices. Detailed theoretical results are presented for the square and hexagonal lattices, with numerical applications for the 2D Co nano-islands on Pt. The derived transition temperature for the hexagonal lattice nano-islands is in good agreement with the experimental data for Co nano-islands on Pt. Though both the core and the periphery domains have the same orderdisorder transition temperature, the magnetization of each domain attains this transition differently. The temperature behavior of the spin correlations is also fundamentally different for the periphery and core sites, which entails distinctly different isothermal susceptibilities, and yields statistically averaged nano-islands susceptibilities that do not correspond to a second order phase transition. The experimental susceptibility results for 2D Co nano-islands on Pt can be interpreted within our EFT Ising model without reference to a transition from a blocking state of the particle to a superparamagnetic behavior. The results for the different lattices are formally comparable, and demonstrate the robustness and general character of the model.

Original languageEnglish
Pages (from-to)2717-2726
Number of pages10
JournalJournal of Magnetism and Magnetic Materials
Volume323
Issue number22
DOIs
Publication statusPublished - Nov 2011
Externally publishedYes

Fingerprint

Magnetization
Magnetic properties
magnetic properties
Superconducting transition temperature
Hamiltonians
Spin fluctuations
Atoms
Ising model
Magnetic anisotropy
Exchange interactions
magnetic permeability
Ground state
Phase diagrams
Anisotropy
Phase transitions
magnetization
transition temperature
Substrates
anisotropy
atoms

Keywords

  • Ising spin model
  • Isothermal susceptibility
  • Magnetic nano-islands
  • Spin fluctuations

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Magnetic properties of 2D nano-islands I : Ising spin model. / Khater, A.; Abou Ghantous, M.

In: Journal of Magnetism and Magnetic Materials, Vol. 323, No. 22, 11.2011, p. 2717-2726.

Research output: Contribution to journalArticle

Khater, A. ; Abou Ghantous, M. / Magnetic properties of 2D nano-islands I : Ising spin model. In: Journal of Magnetism and Magnetic Materials. 2011 ; Vol. 323, No. 22. pp. 2717-2726.
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