Orbital Ordering and Local Magnetic Properties of Mott-Hubbard Insulators YTiO_<b>3</b>and LaTiO_<b>3</b>: NMR Study

Abstract

47,49 Ti, 89 Y and 139 La NMR measurements have been performed to study local magnetic properties of the Mott-Hubbard insulators YTiO 3 and LaTiO 3 . In particular, the magnetic structure of the ferromagnetic (antiferromagnetic) state of YTiO 3 (LaTiO 3 ) is discussed based on the analysis of 47,49 Ti frequency-swept NMR spectra. We found that the Ti NMR spectrum in YTiO 3 is successfully explained by an orbital ordering model proposed by the unrestricted Hartree-Fock and the band calculations. On the other hand, the Ti NMR spectrum in LaTiO 3 is explained without orbital ordering. The internal field H n at the Y site in YTiO 3 is due to the supertransferred hyperfine interaction, whereas the H n at the La site is canceled out because of the local symmetry in the antiferromagnetic state of LaTiO 3 .