Sujit K. Barik

Magnetic and calorimetric studies of magnetocaloric effect in La0.7-xPrxCa0.3MnO3

We report magnetocaloric effect in La0.7 − xPrxCa0.3MnO3 (x = 0, 0.2, 0.3, and 0.4). All these compounds undergo first-order paramagnetic to ferromagnetic transition upon cooling and show field-induced metamagnetic transition (FIMMT) in the paramagnetic state. The FIMMT is accompanied by a release of latent heat and change in temperature of the sample as evidenced from differential scanning calorimetry and thermal analysis data for x = 0.3. The magnetic entropy decreases (−ΔSm = 8.23, 8.1, 7, and 5.38 Jkg−1 K−1 for a field change of ΔH = 5 T, for x = 0, 0.2, 0.3, and 0.4, respectively) and refrigeration capacity (RC) increases with increasing x (RC = 197, 215, 240, and 259 J/kg for x = 0, 0.2, 0.3, and 0.4, respectively). We suggest that collapse of magnetic polarons in the paramagnetic state and magnetovolume effect are responsible for the observed FIMMT and large −ΔSm values.

Investigations on electrical and magnetic properties of multiferroic [(1−x)Pb(Fe0.5Nb0.5)O3−xNi0.65Zn0.35Fe2O4] composites

Here, we report the magnetic, ferroelectric, dielectric properties, and Raman spectroscopic studies of multiferroic [(1−x)Pb(Fe0.5Nb0.5)O3−xNi0.65Zn0.35Fe2O4] composites at room temperature. The phase formation of composites was confirmed independently from the X-ray diffraction and Raman studies. The room temperature magnetic studies reveal ferromagnetic like behavior of these composites in contrast to the paramagnetic nature of Pb(Fe0.5Nb0.5)O3. Furthermore, with increasing x, the saturation magnetization, remnant magnetization, and coercive fields are found to increase. The electrical characterizations of these composites reveal a decrease in remnant polarization and dielectric constant with increasing x. More importantly, the x = 0.2 composite is found to be a very good multiferroic material at room temperature among the composites and could be a potential candidate for future potential applications.

Studies on magnetoelectric coupling in PFN-NZFO composite at room temperature

We report magnetoelectric coupling and Raman spectroscopic studies on [(1 − x)Pb(Fe0.5Nb0.5)O3-xNi0.65Zn0.35Fe2O4] (x = 0.20) PFN-NZFO composite. Apart from the presence of zone centre Raman active modes of the parent compound, some new peaks are observed in the low frequency region. The electric field controlled peak position (∼48 cm−1) suggests that this mode is of magnetic origin. From temperature dependent Raman scattering studies, temperature coefficients for phonons of different symmetries were estimated. Our measurements on electrical control of magnetic order and magnetic control of electrical order confirmed the existence of converse and direct magnetoelectric coupling in this composite at room temperature.