Flexible and self-standing nickel ferrite-PVDF-TrFE cast films: promising candidates for high-end magnetoelectric applications.

Polymer-based magnetoelectrics are identified as a newly emerging area of research due to their profound potential applications centered on spintronic technology. In line with this, we have developed a novel, flexible nickel ferrite (NiFe2O4)-PVDF-TrFE (NF-PVDF-TrFE) polymer based magnetoelectric film, with excellent magnetoelectric coupling at room temperature. Nanocomposite films were prepared by the solution cast method, in which the nickel ferrite nanoparticles with different weight percentages (2, 4, 8 and 16%) were incorporated in the electroactive PVDF-TrFE polymer matrix. The ferroelectric ß-crystalline phase of PVDF-TrFE was confirmed by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and Raman studies. Dielectric and thermal properties of the composite films were found to be substantially improved with the addition of magnetic nanoparticles. Ferroelectric and magnetic characteristics of the composite films were also considerably improved with an increase in NiFe2O4 concentration. A magnetic saturation (Ms) of 4.81 emu g-1 and a ferroelectric maximum polarization of 18.9 µC cm-2 were shown by the composite film at room temperature for 16 wt% loading of NF nanoparticles. Besides these functionalities, ac and dc magnetoelectric coupling coefficients of 69 mV cm-1 Oe-1 and 90 mV cm-1 Oe-1 were obtained for 16NF-PVDF-TrFE along with excellent mechanical stability. These flexible and self-standing magnetoelectric composite films with enhanced magnetoelectric coupling coefficients at room temperature could be suitable candidates for the development of ultramodern information storage devices, memory devices, signal processing devices etc.

Physical properties of RIr3 (R = Gd, Tb, Ho) compounds with coexisting polymorphic phases.

The binary compounds GdIr3, TbIr3 and HoIr3 are synthesized successfully and found to form with macroscopic co-existence of two polymorphic phases: AuBe5 (C15b) and AuCu3-type. The dc magnetization and heat capacity studies confirm that the C15b phase orders ferromagnetically, whereas the AuCu3 phase remains paramagnetic down to 2 K. The frequency dependent ac-susceptibility data, time dependent magnetic relaxation behavior and magnetic memory effect studies suggest that TbIr3 and HoIr3 are cannonical spin-glass systems, but no glassy feature could be found in GdIr3. The critical behavior of all three compounds has been investigated using the magnetization and heat capacity measurements around the transition temperature (TC). The critical exponents α, ß, γ and δ have been estimated using different techniques such as the Arrott-Noakes plot, Kouvel-Fisher plot and critical isotherm as well as analysis of specific heat data and study of magnetocaloric effect. The critical analysis study identifies the type of universal magnetic class in which the three compounds belong.

Unusual bidirectional frequency dependence of dynamical susceptibility in hexagonal intermetallic Pr2Ni0.95Si2.95.

In this study, the synthesis of a novel ternary intermetallic compound Pr2Ni0.95Si2.95 forming in single phase only by deliberately introducing vacancies in Ni/Si site is reported. The detailed studies on dc magnetization, heat capacity, ac magnetization & associated dynamical scaling, different types of non-equilibrium dynamical behaviour, viz., magnetic relaxation behaviour as a function of wait time and temperature, aging phenomena, and magnetic memory effect firmly establish that the compound exhibits spin freezing behaviour below 3.3 K (Tf). However, below Tf, temperature dependence of ac susceptibility data exhibit an additional peak that shows reverse frequency dependence to that generally observed in a glassy system. The unusual bidirectional frequency dependence in a single magnetic system is of significant interest and rarely reported in literature. Competing exchange interaction arising from c/a ~ 1 and crystallographic randomness driven magnetic phase separation has been argued to be responsible for such observation. The reverse frequency shift of the low temperature peak has been described on the basis of a simple phenomenological model proposed in this work.

Dopamine functionalization of BaTiO3: an effective strategy for the enhancement of electrical, magnetoelectric and thermal properties of BaTiO3-PVDF-TrFE nanocomposites.

Electro-active polymer-ceramic composite systems are emerging materials in the fields of nanoelectronic, microelectromechanical and macroelectronic device applications. Still more precise and concise research studies have yet to come in the areas of energy storage, harvesting, energy conversion, etc. In line with this, we have synthesized and analyzed PVDF-TrFE based nanocomposites of both functionalized and non-functionalized BaTiO3 (BTO). All the samples were prepared as free standing films by employing a solvent cast method. A systematic study of structural, morphological, thermal, dielectric, ferroelectric, piezoelectric and magnetoelectric (ME) properties has been carried out. It has been reported that the addition of BTO nanoparticles (with and without functionalization) into a polymer matrix substantially improved the properties of the nanocomposite. By performing the above mentioned characterization, it could be proved that dopamine functionalized BTO (DBTO) samples are better choices for the above mentioned applications including magnetoelectric applications, than the non-functionalized ones.