Abstrakt
Dielectric and magnetic properties of Eu0.5Ba0.25Sr0.25TiO3 are investigated between 10 and 300?K in the frequency range 10?Hz100?THz. A peak in permittivity revealed near 130?K and observed ferroelectric hysteresis loops prove the ferroelectric order below this temperature.
The peak in permittivity is given mainly by softening of the lowest frequency polar phonon (soft mode revealed in THz and infrared (IR) spectra) that demonstrates displacive character of the phase transition. Room-temperature X-ray diffraction analysis reveals cubic structure, but the IR reflectivity spectra give evidence of a lower crystal structure, presumably tetragonal I4/mcm with tilted oxygen octahedra as it has been observed in EuTiO3.
The magnetic measurements show that the antiferromagnetic order occurs below 1.8?K. Eu0.5Ba0.25Sr0.25TiO3 has three times lower coercive field than Eu0.5Ba0.5TiO3; therefore, we propose this system for measurements of electric dipole moment of electron.