Nidhi Adhlakha

Study of structural, dielectric and magnetic behaviour of Ni0.75Zn0.25Fe2O4–Ba(Ti0.85Zr0.15)O3 composites

A class of hybrid composites (x)Ni0.75Zn0.25Fe2O4?(1???x)Ba(Ti 0.85Zr 0.15)O 3 (for x variations 0, 0.20, 0.30 and 0.40) synthesized via a solid state reaction method is investigated. The structural analysis was carried out using an x-ray diffraction graph which reveals a mixed phase of the hybrid composites with spinel phase for ferrite component and perovskite phase for the ferroelectric component. The microstructural analysis and grain size determination is carried out using a field emission scanning electron microscope (FESEM). The relative dielectric constant with frequency variation (in the range of 100?Hz?1?MHz) and temperature at three fixed frequencies (100?Hz, 1?KHz and 10?KHz) is studied. The magnetic properties such as saturation magnetization (Ms ) and magnetic moment (?B) are calculated from the magnetic hysteresis loops obtained using a vibrating sample magnetometer (VSM). The value of remnant polarization for pure BZT is found to be 6.18??C?cm?2 and as the content of ferrite phase is increased up to 40?mol%, this value decreases. The magnetoelectric effect is studied using magnetocapacitance which takes a maximum value for 40?mol% addition of ferrite.

Effect of BaTiO 3 addition on structural, multiferroic and magneto-dielectric properties of 0.3CoFe 2 O 4 0.7BiFeO 3 ceramics

This study reports the various physical properties of (1�x)(0.3CoFe2O4-0.7BiFeO3)-xBaTiO3 composites (equivalently denoted as 0.3CFO-0.7BFO/BT) with the compositions x=0, 0.30, 0.35, 0.40 and 1.0. The composites are synthesized through a hybrid processing technique in which 0.3CFO–0.7BFO is prepared through a sol-gel process, and BT is processed through a solid state reaction method. Subsequently, the effects of the addition of BT on the structural, dielectric, magnetic and magneto-dielectric properties of 0.3CFO–0.7BFO have been investigated for various BT concentrations. The Rietveld refinement analysis of x-ray diffraction patterns reveals the structural distortion in the BFO phase with the addition of BT, while no such distortion has been observed for the CFO phase. Energy dispersive spectroscopy confirms the presence of two types of grains that correspond to the 0.3CFO–0.7BFO and BT phases in field emission scanning electron micrographs of the composites. Improved dielectric properties have been observed, which are associated with the improved density of composites with the addition of BT. Measurements of the magnetic and ferroelectric hysteresis loops at room temperature indicate that the composites exhibit ferroelectricity and ferromagnetism simultaneously at room temperature. An increase of the electric polarization has been observed due to structural distortion arising with the addition of BT. The significant dependence of the dielectric constant on the magnetic field has been observed in the prepared composites. The highest value of the magneto-dielectric response (3.2%) has been observed for a 40 mol% addition of BT.

Direct-Write X-ray Nanopatterning: A Proof of Concept Josephson Device on Bi2Sr2CaCu2O8+δ Superconducting Oxide

We describe the first use of a novel photoresist-free X-ray nanopatterning technique to fabricate an electronic device. We have produced a proof-of-concept device consisting of a few Josephson junctions by irradiating microcrystals of the Bi2Sr2CaCu2O8+δ (Bi-2212) superconducting oxide with a 17.6 keV synchrotron nanobeam. Fully functional devices have been obtained by locally turning the material into a nonsuperconducting state by means of hard X-ray exposure. Nano-XRD patterns reveal that the crystallinity is substantially preserved in the irradiated areas that there is no evidence of macroscopic crystal disruption. Indications are that O ions have been removed from the crystals, which could make this technique interesting also for other oxide materials. Direct-write X-ray nanopatterning represents a promising fabrication method exploiting material/material rather than vacuum/material interfaces, with the potential for nanometric resolution, improved mechanical stability, enhanced depth of patterning, and absence of chemical contamination with respect to traditional lithographic techniques.

Study of dielectric, magnetic and magnetoelectric behavior of (x)NZF-(1-x)PLSZT multiferroic composites

The magnetoelectric composites (x)Ni_0.75Zn_0.25Fe₂O₄-(1-x)Pb_0.9(La_0.96Sr_0.04)_0.1(Zr_0.65 Ti_0.35)_0.975 O₃ (for x variations 0, 0.20 and 1.0) where Ni_0.75Zn_0.25Fe₂O₄ i.e. NZF is ferrite phase and Pb_0.9(La_0.96Sr_0.04)_0.1(Zr_0.65Ti_0.35)_0.975O₃ i.e. PLSZT is ferroelectric phase, were synthesized via solid state reaction method. The presence of both the constituent phases was confirmed by X-ray diffraction studies. The microstructural analysis and grain size determination was carried out using field emission scanning electron microscope (FESEM). Variation of dielectric constant and dielectric loss with temperature at various frequencies (1 kHz and 10 kHz) was studied. The good ferroelectric behavior and ferromagnetic behavior of the composites were confirmed by Polarization versus Electric field (P-E) and Magnetization versus Magnetic field (M-H) measurements, respectively. The coupling between ferroelectric and ferromagnetic domains was confirmed through the observation of magnetic fieldinduced relative change in dielectric constant (Magnetocapacitance). The value of magnetocapacitance is found to be 2.6 % for the synthesized composite (with x=0.20). The fractional change of magnetic field induced dielectric constant can also be expressed as Δε~γM² and the value of γ is found to be ~8.16×10^-2 (emu/g)^-2 for composite with x=0.20.

Magnetocapacitance and Magnetic Properties of Cr³+ Ions Doped Hematite Prepared by Sol-Gel Method at Room Temperature

Hematite (α-Fe2O3) and 5 mol.% Cr3+ ions doped hematite were synthesized by sol gel method. X-ray diffraction (XRD) patterns of powder calcined at 500 0C show the formation of single-phase rhombohedral structure. Thermogravimetric (TG) analysis of as prepared powder indicates the formation of sample around 400 0C. FESEM analysis shows grain size of sintered pellets ~ 100 nm. Magnetization of hematite powders was found to be higher compared with Cr3+ ions doped hematite at the same magnetic field (10 kOe). We observed magnetocapacitance in both the systems at room temperature. As neither hematite nor Cr3+ ions doped hematite is multiferroic material, the observed magnetodielectric property is believed to arise from extrinsic effect such as magnetoresistance. Keywords—Sol-gel; Magnetic materials; Hematite; X-ray diffraction.