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 by using the effective spin and pseudospin 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 changes only little whereas the spin-exchange coupling along the c-axis is expected to change from positive to negative nearly continuously and approaches zero at the phase boundary. The resultant strong two-dimensionality in the spin coupling causes rapid suppression of the critical temperature, as observed experimentally. It may induce large quantum fluctuations in this region.
| Original language | English |
|---|---|
| Pages (from-to) | 1777-1789 |
| Number of pages | 13 |
| Journal | journal of the physical society of japan |
| Volume | 70 |
| Issue number | 6 |
| DOIs | |
| Publication status | Published - 2001 Jun |
| Externally published | Yes |
Keywords
- A-type antiferromagnetism
- GdFeO-type distortion
- Mermin and Wagner's theorem
- Orbital degrees of freedom
- Orbital ordering
- Perovskite-type Ti oxides
- Second-order perturbation theory
- Two-dimensional spin coupling
- d-type Jahn-Teller distortion
ASJC Scopus subject areas
- Physics and Astronomy(all)