Magnetic properties of two-dimensional dipolar squares: Boundary geometry dependence

Ryoko Sugano, Katsuyoshi Matsushita, Akiyoshi Kuroda, Yusuke Tomita, Hajime Takayama

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

By means of the molecular dynamics simulation of gradual cooling processes, we investigate magnetic properties of classical spin systems only with the magnetic dipole-dipole interaction, which we call dipolar systems. Focusing on their finite-size effect, particularly their boundary geometry dependence, we study two finite dipolar squares cut out from a square lattice with Φ = 0 and π/4, where Φ is the angle between the direction of the lattice axis and that of the square boundary. Distinctly different results are obtained in the two dipolar squares. In the Φ = 0 square, the "from-edge-to- interior freezing" of spins is observed. Its ground state has a multidomain structure whose domains consist of two among infinitely (continuously) degenerated Luttinger-Tisza (LT) ground-state orders on a bulk square lattice, i.e., the two antiferromagnetically aligned ferromagnetic chains (af-FMC) orders directed parallel to the two lattice axes. In the Φ = π/4 square, on the other hand, the freezing starts from the interior of the square, and its ground state is nearly in a single domain with one of the two af-FMC orders. These geometry effects are argued to originate from the anisotropic nature of the dipole-dipole interaction, which depends on the relative direction of sites in the real space of the interacting spins.

Original languageEnglish
Article number044705
JournalJournal of the Physical Society of Japan
Volume76
Issue number4
DOIs
Publication statusPublished - 2007 Apr 1

Keywords

  • Dipole-dipole interaction
  • Freezing characteristics
  • Magnetic nano-particle array
  • Molecular dynamics simulation

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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