Da Woon Jeong

Charge states and magnetic ordering in LaMnO3/SrTiO3 superlattices

We investigated the magnetic and optical properties of [(LaMnO{sub 3}){sub n}/(SrTiO{sub 3}){sub 8}]{sub 20} (n = 1, 2, and 8) superlattices grown by pulsed-laser deposition. We found that a weak ferromagnetic and semiconducting state developed in all superlattices. An analysis of the optical conductivity showed that the LaMnO{sub 3} layers in the superlattices were slightly doped. The amount of doping was almost identical regardless of the LaMnO{sub 3} layer thickness up to eight unit cells, suggesting that the effect is not limited to the interface. On the other hand, the magnetic ordering became less stable as the LaMnO{sub 3} layer thickness decreased, probably due to a dimensional effect.

Temperature evolution of itinerant ferromagnetism in SrRuO3 probed by optical spectroscopy.

The temperature (T) dependence of the optical conductivity spectra σ(ω) of a single crystal SrRuO(3) thin film is studied over a T range from 5 to 450 K. We observed significant T dependence of the spectral weights of the charge transfer and interband d-d transitions across the ferromagnetic Curie temperature (T(c) ∼ 150 K). Such T dependence was attributed to the increase in the Ru spin moment, which is consistent with the results of density functional theory calculations. T scans of σ(Ω,T) at fixed frequencies Ω reveal a clear T(2) dependence below T(c), demonstrating that the Stoner mechanism is involved in the evolution of the electronic structure. In addition, σ(Ω,T) continues to evolve at temperatures above T(c), indicating that the local spin moment persists in the paramagnetic state. This suggests that SrRuO(3) is an intriguing oxide system with itinerant ferromagnetism.

Phonon-assisted optical excitation in the narrow bandgap Mott insulator Sr3Ir2O7

We examined the temperature (T) evolution of the optical conductivity spectra of Sr

Dimensionality Control of d-orbital Occupation in Oxide Superlattices

_3

LaMnO3 thin films grown by using pulsed laser deposition and their simple recovery to a stoichiometric phase by annealing

Ir

Optical Spectroscopy of the Carrier Dynamics in LaVO3/SrVO3 Superlattices

_2

Phonon assisted optical excitation in narrow bandgap spin-orbit insulator Sr

O

_{3}

_7

Ir

over a wide range of 10-400 K. The system was barely insulating, exhibiting a small indirect bandgap of

_{2}

\sim