J. H. Jung

Elastic softening and central peaks in BaTiO3 single crystals above the cubic-tetragonal phase-transition temperature

A strong relaxation mode was observed in the paraelectric phase of barium titanate (BaTiO3) single crystals by Brillouin scattering study and was found to correlate with the softening of the longitudinal acoustic mode and the increase in the hypersonic damping. These observations support the existence of polar percursors and their electrostrictive coupling with the strain caused by the acoustic waves, consistent with former studies evidencing off-centered Ti ions in the high-symmetry cubic phase. A critical slowing down has been clearly observed in the vicinity of the cubic-tetragonal phase transition, indicating order-disorder component contributes to the phase transition of BaTiO3.

Strain-induced magnetoelectric coupling in BaTiO3/Fe3O4 core/shell nanoparticles

We report a strain-induced magnetoelectric coupling in BaTiO3/Fe3O4 ferroelectric core/ferrimagnetic shell nanoparticles. The temperature-dependent magnetoresistance and magnetization clearly show several jumps near the structural phase transition temperatures of BaTiO3. Below the Verwey transition temperature of Fe3O4, i.e., at 20 K, the dielectric constant of BaTiO3/Fe3O4 decreases continuously upon application of an external magnetic field, and the observed magnetodielectric curve does not follow the square of the magnetization. We discuss the effect of strain on the electric field-dependent magnetic anisotropy near the core/shell interface.

Magnetodielectric effect in BaTiO3−LaMnO3 composites

The structural, dielectric, magnetic, and magnetodielectric properties were systematically investigated for (1−x)BaTiO3−(x)LaMnO3 composites in wide temperatures, frequencies, and mole percent (x). Dielectric anomaly around 410 K and magnetic hysteresis at 293 K were clearly observed, which might imply the coexistence of ferroelectricity and ferromagnetism at room temperature. The values of magnetodielectric effect were well scaled with M2, i.e., ([e(H)−e(0)]/e(0))∼M2, and were increased with x. The observed magnetodielectric effect were discussed in conjunction with the formation of a magnetoresistive (La,Ba)MnO3 phase.

Resonant Magnetoelectric X-ray Scattering in GaFeO3: Observation of Ordering of Toroidal Moments

We report on the first observation of magnetoelectric X-ray scattering (MEXS), i.e., incident- k -direction-dependent scattering, for a polar ferrimagnet GaFeO 3 . Near the K edge of Fe, the magnet...

Application of magnetic fields for a low temperature growth of high-quality SrRuO3 thin films

We report the low temperature growth of high-quality SrRuO3 thin films by applying moderate magnetic fields (Heclipse) during the growth. The lattice constants, the temperature dependence of resistivity and the ferromagnetic transition temperature of the film grown under Heclipse = 2500?Oe at a temperature as low as 400??C were quite similar to the reported values for the film grown at high temperatures of 700?800??C under no magnetic field. Moreover, we found that the magnetic coercive field decreased significantly with increasing Heclipse, which should be quite useful for a coercivity tunable top electrode for magnetic tunnel junctions.