S. Satapathy

Effect of coalesce doping of Nd and La on structure, dielectric, and magnetic properties of BiFeO3

Single phase Bi0.9−xLa0.1NdxFeO3 (BLNFOx) (x=0.05, 0.07, and 0.1) multiferroic ceramics were prepared to study the effect of combine substitution of La and Nd in BiFeO3 (BFO). X-ray diffraction studies revealed phase transition from rhombohedral (R3c) to triclinic (P1) on substitution of 05 and 07 mol % of Nd and subsequent transition to monoclinic C2/c with 10 mol % of Nd along with 10 mol % of La. These structural phase transitions and weakening of long range ferroelectric order with increasing x are also confirmed from Raman spectra. The existence of ferroelectricity and the corresponding Curie temperature for all noncentrosymmetric composition were determined using differential thermal analysis. Small remnant magnetization of 0.067 emu/g is observed in (BLNFO)x=0.07 as a result of collapse of space modulated spin structure. For pure BFO dielectric anomaly was observed at 355 °C corresponding to Neel temperature. Due to coexistence of long range ferroelectric order and canted antiferromagnetic orders i...

Relaxor ferroelectric behavior of BaMnO3 (2H) at room temperature

Geometrically frustrated hexagonal BaMnO3 (2H) is an interesting material due to the presence of more than one ferroic order parameters. Although the material is well known, still there exists confusion on the crystal structure of this material at room temperature and its ferroelectric properties have not been explored. Here, we report noncentrosymmetric crystal structure and ferroelectric properties of BaMnO3 (2H) at room temperature. The dielectric diffusivity calculated from modified Curie-Weiss laws and non linear Vogel-Fulcher fittings implies weak relaxor characteristic of BaMnO3 (2H). The ferroelectric properties arise due to off centering of Mn4+ ion in unit cell and weak relaxor properties are attributed to the presence of a smaller amount of Mn3+ cations which creates disorder in 2H-BaMnO3.

Resonant Raman of O–H/O–D vibrations and photoluminescence studies in LiTaO3 thin film

Resonant Raman spectra (RRS) of O–H and O–D vibration and libration modes, their combinations, and higher harmonics have been observed in LiTaO3 polycrystalline thin films. RRS peaks are superimposed on photoluminescence (PL) spectrum. Monochromatic light from a xenon lamp is used as excitation source. PL spectrum shows two broad peaks: first near the band gap in UV (4.4–4.8 eV) and another in the sub-band-gap region (<4.0 eV). Band gap PL along with RRS peaks are reported for the first time. PL excitation spectrum shows a peak at 4.8 eV. Peak positions and full width at half maximum of RRS peaks depend on the excitation energy. Dispersions of the fundamental and the third harmonic of the stretching mode of O–H with excitation energy are about 800 and 2000 cm−1/eV, respectively. This dispersion is much higher than reported in any other material.