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Origin of G-type Antiferromagnetism and Orbital-Spin Structures in ${\rm LaTiO}_3$

Masahito Mochizuki·Masatoshi Imada
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Abstract

The possibility of the $D_{3d}$ distortion of ${\rm TiO}_6$ octahedra is examined theoretically in order to understand the origin of the G-type antiferromagnetism (AFM(G)) and experimentally observed puzzling properties of ${\rm LaTiO}_3$. By utilizing an effective spin and pseudospin Hamiltonian with the strong Coulomb repulsion, it is shown that AFM(G) state is stabilized through the lift of the $t_{2g}$-orbital degeneracy accompanied by a tiny $D_{3d}$-distortion . The estimated spin-exchange interaction is in agreement with that obtained by the neutron scattering. Moreover, the level-splitting energy due to the distortion can be considerably larger than the spin-orbit interaction even when the distortion becomes smaller than the detectable limit under the available experimental resolution. This suggests that the orbital momentum is fully quenched and the relativistic spin-orbit interaction is not effective in this system, in agreement with recent neutron-scattering experiment.

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Masahito Mochizuki, Masatoshi Imada. 2001-05-07. Origin of G-type Antiferromagnetism and Orbital-Spin Structures in ${\rm LaTiO}_3$. https://doi.org/10.1143/jpsj.70.2872

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