Composition Dependent Room Temperature Structure, Electric and Magnetic Properties in Magnetoelectric Pb (Fe1/2Nb1/2) O3Pb (Fe2/3W1/3) O3 Solid-Solutions

We report on the studies of room temperature (RT) crystal structure, electric and magnetic properties of (1−x) Pb(Fe1/2Nb1/2)O3 – x Pb(Fe2/3W1/3)O3 (PFN1−x – PFWx) (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) solid solutions through the measurements of X-ray diffraction, FTIR, scanning electron microscopy (SEM), Neutron diffraction, Raman, Magnetic, Mössbauer and ferroelectric measurements. FTIR spectra showed two main perovskite related transmission bands. The SEM analysis shows an average grain size of 2 μm for all the solid solutions. Rietveld refinement was performed on RT X-ray diffraction (XRD) and neutron diffraction (ND), which reveals, the monoclinic phase for x = 0.0 with space group Cm and Cubic phase for x = 1.0 with space group Pm-3m. In other words, increasing x, the samples exhibit a gradual phase transition from monoclinic to cubic. In addition, the Raman spectroscopy corroborates the change in structural symmetry from monoclinic (Cm) to cubic (Pm-3m) on varying x. The coexistence of both monoclinic and cubic symmetries was observed between x = 0.2–0.8. Magnetic measurements shows that, the magnetic phase transition from paramagnetic to antiferromagnetic (AFM) was observed at or above RT for x = 0.6 and above. The magnetic structure was refined using the propagation vector k = (½, ½, ½) and structure was found to be G-type antiferromagnetic. Magnetic properties (M-H loops) shows, a weak ferromagnetic behaviour with antiferromagnetic ordering at RT. At RT, x = 0.0–0.6 the samples exhibits disordered paramagnetic property but weakly coupled with antiferromagnetic domains. But, x = 0.8 and 1.0 samples show antiferromagnetic and they are weakly coupled with paramagnetic domains. The temperature dependent magnetization (M(T)) confirms, the augmentation of Néel temperature (TN) from 155 K to 350 K on increasing x. Mössbauer spectroscopy confirms superparamagnetic nature with the presence of Fe in 3+ state and on increasing x, the spectra changes from doublet to sextet. The ferroelectric (P-E) study confirms the existence of ferroelectric ordering with leaky behaviour. The reasonable ferroelectric loops with antiferromagnetic properties indicate samples with x = 0.2–0.6 show good magnetoelectric characteristics and may find applications in multiferroics

Kharif Sorghum in Karnataka: An Economic Analysis

Sorghum, which once occupied more than 18 M ha of area in the country, has been on a continuous decline during the past two decades and has fallen down to 10.39 M ha. Most of the decline in area has occurred in kharif sorghum. This warrants critical examination of the changing scenario of kharif sorghum and identification of the reasons thereof. For the macro analysis, secondary data on various aspects of kharif sorghum have been used, whereas the farm survey data have been used to draw the inferences at the micro level with respect to changing scenario of kharif sorghum. The growth rates in area, production and productivity of kharif sorghum have been computed. The Herfindahl index has been computed to find out crop diversification in the sample districts of Dharwad and Belgaun. The deceleration in the kharif sorghum area in the overall period 1970-71 to 1997-98 and different sub-periods has been found due to the diversion of kharif sorghum area to more remunerative crops like oil seeds (groundnut and sunflower), and pulses. Belgaum district displayed a moderate degree of crop diversification compared to that of Dharwad district. Unfavourable prices, declining yields, inadequate credit and adverse climatic conditions have been identified as the major reasons for the replacement of kharif sorghum crop in the two sample districts. The net returns and benefit-cost ratio have been found low in the cultivation of kharif sorghum compared to those of its competing crops, viz. cotton, green gram and groundnut.Agricultural and Food Policy,

Multiwalled carbon nanotube-based patch antenna for bandwidth enhancement

A novel carbon nanotube (CNT)-based rectangular microstrip antenna for wide impedance bandwidth applications has been designed and developed. The copper patch commonly placed on the substrate in a conventional rectangular microstrip antenna is replaced with a CNT patch prepared using spin coating. The MWCNT patch antenna was fabricated by spin coating method and it exhibits an increased impedance bandwidth of 20. The enhancement of the impedance bandwidth does not affect the broadside radiation characteristics. The carbon nanotubes are highly conductive nanomaterial. Due to this unique property, each nanotube present on the surface resonates electromagnetic waves individually and influences the enhancement in the bandwidth. The simple design and fabrication of the proposed antenna can be employed for synthetic aperture radar applications. © 2017 Elsevier B.V

Structural and magnetic properties of nanocrystalline BaFe12O19 synthesized by microwave-hydrothermal method

Nanocrystalline BaFe12O19 powders were prepared by microwave-hydrothermal method at 200 °C/45 min. The as-synthesized powders were characterized by using X-ray diffraction (XRD), thermogravimetry (TG) and differential thermal analysis (DTA). The present powders were densified at different temperatures, i.e., 750, 850, 900 and 950 °C for 1 h using microwave sintering method. The phase formation and morphology studies were carried out using XRD and field emission scanning electron microscopy (FE-SEM). The average grain sizes of the sintered samples were found to be in the range of 185–490 nm. The magnetic properties such as saturation magnetization and coercive field of sintered samples were calculated based on magnetization curves. A possible relation between the magnetic hysteresis curves and the microstructure of the sintered samples was investigated

Evidence for Room-Temperature Weak Ferromagnetic and Ferroelectric Ordering in Magnetoelectric Pb(Fe0.634W0.266Nb0.1)O3 Ceramic

We report the evidence of weak ferromagnetic and ferroelectric ordering in polycrystalline Pb(Fe0.634 W0.266Nb0.1)O3 (0.8(PbFe2/3W1/3)O3�0.2Pb(Fe1/2Nb1/2) O3) (PFWN) ceramic at room temperature. The Pb(Fe0.634 W0.266Nb0.1)O3solid solution synthesized through the columbite method. The obtained single-phase Pb(Fe0.634 W0.266Nb0.1)O3ceramic was subjected to X-ray diffraction, neutron diffraction, magnetization, Mössbauer spectroscopy, and ferroelectric measurements. The X-ray diffraction and neutron diffraction pattern confirms the formation of single phase without any traces of pyrochlore phases, having cubic structure with Pm-3m space group. The Rietveld refinements were carried out on both patterns, and ND data confirms the G-type antiferromagnetic structure with propagation vector (k = 1/2, 1/2, and 1/2). However, along with the antiferromagnetic ordering of the Fe spins, we also observed the existence of weak ferromagnetism. This result was confirmed through (i) a clear opening of hysteresis (M � H) loop, (ii) bifurcation of the field-cooled (FC) and zero-field-cooled (ZFC) susceptibilities, (iii) spin-glass behavior, and (iv) Mössbauer spectroscopy. © 2016, Springer Science+Business Media New York

Low-temperature neutron diffraction and magnetic studies on the magnetoelectric multiferroic Pb(Fe0.534Nb0.4W0.066)O3

We report detailed low-temperature magnetic and neutron diffraction studies on 0.8 Pb(Fe0.5Nb0.5)O3�0.2 Pb(Fe0.67W0.33)O3 which is written as Pb(Fe0.534Nb0.4W0.066)O3 (PFWN) in the general form. Magnetic susceptibility measurement data show that PFN exhibits antiferromagnetic to paramagnetic transition (TN) around 155 K (Matteppanavar et al. in J Mater Sci 50:4980�4993. doi:10.1007/s10853-015-9046-5, 2015). In the present solid solution, the magnetic susceptibility (�) shows Néel temperature enhanced up to around 187 K. Temperature-dependent neutron diffraction studies well support the tuning up of TN from 155 to 187 K. On decreasing the temperature, for T < TN (TN = 187 K), an extra peak grows at scattering vector Q = 1.35 à �1, which indicates the onset of antiferromagnetic ordering. The observed magnetic structure is G-type antiferromagnetic with the propagation vector, k = 0.25, 0.5, 0.5. The refined monoclinic lattice parameters (a, b and c), angle (β), unit cell volume, derivative of unit cell volume, magnetic moments and integrated intensity of magnetic peak (111) show anomaly around the TN, which is a manifestation of spin�lattice coupling. Also, the lattice parameters (a, b and c) and unit cell volume exhibit negative thermal expansion below TN and a large thermal expansion above TN. © 2017, Springer Science+Business Media New York

Effect of Fe doping on the structural, optical and magnetic properties of combustion synthesized nanocrystalline ZnO particles

In the present study, the effect of Fe substitution in nanocrystalline Zn1�xFexO (x = 0, 0.01, 0.03, 0.05 and 0.07) particles synthesized through solution combustion are reported. The detailed structural and microstructural studies of as-synthesized samples were carried out through X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Further, the optical and magnetic properties were investigated respectively through Diffuse Reflectance Spectroscopy and Superconducting Quantum Interference Device (SQUID). The XRD results as well as the Rietveld refinement on XRD data reveals the single phase, polycrystalline nature of the prepared materials and no impurities such as ZnFe2O4, Fe2O3, Fe3O4 were seen, which confirms the substitution of Fe at Zn site. SEM and TEM studies reveal that, the samples are porous and agglomerated due to the evolution of large amount of gases during the combustion and also as-formed particles are found to be in nano-range with an particle size varies from 20�25 nm. Optical studies show that, the absorption edge shifts to lower energy/higher wavelength. Room temperature magnetic (SQUID) studies shows that the undoped ZnO exhibit diamagnetic property where as Fe doped ZnO exhibit intrinsic room temperature ferromagnetism (RTFM) with increasing coercivity with Fe concentration and is attributed to the incorporation of Fe into ZnO host matrix. © 2017 The Society of Powder Technology Japa

Electric field-induced tuning of magnetism in PbFe0.5Nb0.5O3 at room temperature

We study the influence of electrical poling, carried out at room temperature, on the structure and magnetism of Pb(Fe0.5Nb0.5)O-3 by analyzing the differences observed in structural and magnetic properties before and after the electrical poling. The changes observed in magnetization of Pb(Fe0.5Nb0.5)O-3 before and after electrical poling exhibit considerably strong converse magnetoelectric effect at room temperature. In addition, the strengthening of Fe/Nb-O bond due to electrical poling is discussed on the basis of Raman spectral studies and analysis of neutron diffraction patterns. The potential tunability of magnetization with electrical poling can be an ideal tool for realization of application potential of this multiferroic material. (C) 2015 AIP Publishing LLC

Synthesis Of Nano Bismuth Ferrite Multiferroics By Microcontroller Based Thermogravimetric Analyzer

Microcontroller based thermogravimetric analyzer (MTGA) is an home built technique used to study the thermal decomposition of inorganic solids, chemical properties of intermediate and final products, synthetic conditions and synthesis of nanomaterials. The MTGA has additional features like controlled gas delivery system suitable for synthesis of nanomaterials in various gas atmospheres. This paper reports characterization of nano bismuth ferrite-BifeO3 (BFO) synthesized by MTGA. The MTGA system has been calibrated for BFO precursors. The variation in mass of redox mixture (metal nitrates and gylcene) with respect to temperature (thermogram) reveal the ideal conditions for the preparation of nano BFO by different techniques. It was found that structural and electrical results of BiFeO3 synthesized by MTGA are in good agreement with that prepared by other techniques like solution combustion method, sol-gel method, Pechini method, sonochemical method, hydrothermal method etc. The microcontroller based thermogravimetric analyser is one of the good techniques for the preparation of nanomaterials in different gas atmaspheres