Optical response of ferromagnetic YTiO_3 studied by spectral ellipsometry

Abstract

We have studied the temperature dependence of spectroscopic ellipsometry spectra of an electrically insulating, nearly stoichiometric YTiO_3 single crystal with ferromagnetic Curie temperature T_C = 30 K. The optical response exhibits a weak but noticeable anisotropy. Using a classical dispersion analysis, we identify three low-energy optical bands at 2.0, 2.9, and 3.7 eV. Although the optical conductivity spectra are only weakly temperature dependent below 300 K, we are able to distinguish high- and low-temperature regimes with a distinct crossover point around 100 K. The low-temperature regime in the optical response coincides with the temperature range in which significant deviations from Curie-Weiss mean field behavior are observed in the magnetization. Using an analysis based on a simple superexchange model, the spectral weight rearrangement can be attributed to intersite d_i^1d_j^1 \longrightarrow d_i^2d_j^0 optical transitions. In particular, Kramers-Kronig consistent changes in optical spectra around 2.9 eV can be associated with the high-spin-state (^3T_1) optical transition. This indicates that other mechanisms, such as weakly dipole-allowed p-d transitions and/or exciton-polaron excitations, can contribute significantly to the optical band at 2 eV. The recorded optical spectral weight gain of 2.9 eV optical band is significantly suppressed and anisotropic, which we associate with complex spin-orbit-lattice phenomena near ferromagnetic ordering temperature in YTiO_3.

References in corpus (19)

• Calculations of Hubbard U from first-principles
• Mott transition and suppression of orbital fluctuations in orthorhombic 3$d^1$ perovskites
• Orbital order and fluctuations in Mott insulators
• Crystal and magnetic structure of LaTiO3 : evidence for non-degenerate $t_{2g}$-orbitals
• How chemistry controls electron localization in 3d1 perovskites: A Wannier-function study
• Interplay between orbital ordering and lattice distortions in LaMnO3, YVO3, and YTiO3
• Spin-controlled Mott-Hubbard bands in LaMnO_3 probed by optical ellipsometry
• Fingerprints of spin-orbital physics in cubic Mott insulators: Magnetic exchange interactions and optical spectral weights
• Orbital Physics in the Perovskite Ti Oxides
• Magnetic Order and Dynamics in an Orbitally Degenerate Ferromagnetic Insulator
• Quantum behavior of Orbitals in Ferromagnetic Titanates: Novel Orderings and Excitations
• Lattice Distortion and Magnetism of 3d-$t_{2g}$ Perovskite Oxides
• Theory of optical spectral weights in Mott insulators with orbital degrees of freedom
• Determination of the orbital moment and crystal field splitting in LaTiO${}_3$
• Theory of orbital state and spin interactions in ferromagnetic titanates
• Lattice Relaxation and Charge-Transfer Optical Transitions Due to Self-Trapped Holes in Non-Stoichiometric LaMnO${}_3$ Crystal
• The magnetic structure of the Jahn-Teller System LaTiO3
• Magnetic and Orbital States and Their Phase Transition of the Perovskite-Type Ti Oxides: Strong Coupling Approach
• Magnetic Phase Transition of the Perovskite-type Ti Oxides

Cited by in corpus (15)

• Electrodynamics of Correlated Electron Materials
• Optical Stabilization of Fluctuating High Temperature Ferromagnetism in YTiO${}_3$
• Low-energy Mott-Hubbard excitations in LaMnO_3 probed by optical ellipsometry
• Atomic scale electronic structure of the ferromagnetic semiconductor Cr2Ge2Te6
• Mott-Hubbard exciton in the optical conductivity of YTiO3 and SmTiO3
• Floquet engineering of multi-orbital Mott insulators: applications to orthorhombic titanates
• Ferromagnetism and Lattice Distortions in the Perovskite YTiO${}_3$
• Interband and polaronic excitations in YTiO3 from first principles
• Dipole-active optical phonons in YTiO_3: ellipsometry study and lattice-dynamics calculations
• Formation of metallic magnetic clusters in a Kondo-lattice metal: Evidence from an optical study
• Nature of the ferromagnetic-antiferromagnetic transition in Y${}_{1-x}$La${}_x$TiO${}_3$
• Localization Phenomena in Disordered Tantalum Films
• Control of Mooij correlations at the nanoscale in the disordered metallic Ta - nanoisland FeNi multilayers
• Raman scattering study and lattice-dynamics calculations in YTiO3: Precursor of the magnetic phase transition in the phonon anomalies
• Magnetic resonance study of rare-earth titanates