Magnetic Phase Transition of the Perovskite-Type Ti Oxides

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Abstract

The properties and mechanism of the magnetic phase transition of the perovskite-type Ti oxides, which is driven by the Ti-O-Ti bond angle distortion, are studied theoretically using the effective spin and pseudo-spin Hamiltonian with strong Coulomb repulsion. It is shown that the A-type antiferromagnetic (AFM(A)) to ferromagnetic (FM) phase transition occurs as the Ti-O-Ti bond angle is decreased. Through this phase transition, the orbital state is hardly changed so that the spin-exchange coupling along the c-axis changes nearly continuously from positive to negative and is approximately zero at the phase boundary. The resultant strong two-dimensionality in the spin coupling causes rapid suppression of the critical temperature, as observed experimentally.

Original languageEnglish
Pages (from-to)1982-1985
Number of pages4
Journaljournal of the physical society of japan
Volume69
Issue number7
DOIs
Publication statusPublished - 2000 Jul
Externally publishedYes

Keywords

  • A-type antiferromagnetism
  • GdFeO-type distortion
  • Mermin and Wagner's theorem
  • Orbital ordering
  • Perovskite-type Ti oxides
  • Second-order perturbation theory
  • d-level degeneracy

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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