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

Low temperature magnetic studies on PbFe0.5Nb 0.5O3 multiferroic

PbFe0.5Nb0.5O3 (PFN), a well-known A(B′1/2B″1/2)O3 type multiferroic, was successfully synthesized in single phase by a single step solid state reaction method. The single phase PFN was characterized through XRD, microstructure through SEM, and magnetic studies were carried out through a temperature dependent vibrating sample magnetometer (VSM) and neutron diffraction (ND) measurements. PFN exhibits a cusp at around 150 K in the temperature dependent magnetic susceptibility corresponding to the Néel temperature (TN1) and another peak around 10 K (TN2) corresponding to spin-glass like transition. In the temperature dependent ND studies, a magnetic Bragg peak appears at Q=1.35 Å−1 (where Q=4πsinθ/λ, is called the scattering vector) below TN (150 K) implying antiferromagnetic (AFM) ordering in the system. On the basis of Rietveld analysis of the ND data at T=2 K, the magnetic structure of PFN could be explained by a G-type antiferromagnetic structure

K-Means and Fuzzy based Hybrid Clustering Algorithm for WSN

Wireless Sensor Networks (WSN) acquired a lotof attention due to their widespread use in monitoring hostileenvironments, critical surveillance and security applications. Inthese applications, usage of wireless terminals also has grownsignificantly. Grouping of Sensor Nodes (SN) is called clusteringand these sensor nodes are burdened by the exchange of messagescaused due to successive and recurring re-clustering, whichresults in power loss. Since most of the SNs are fitted with nonrechargeablebatteries, currently researchers have been concentratingtheir efforts on enhancing the longevity of these nodes. Forbattery constrained WSN concerns, the clustering mechanism hasemerged as a desirable subject since it is predominantly good atconserving the resources especially energy for network activities.This proposed work addresses the problem of load balancingand Cluster Head (CH) selection in cluster with minimum energyexpenditure. So here, we propose hybrid method in which clusterformation is done using unsupervised machine learning based kmeansalgorithm and Fuzzy-logic approach for CH selection

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

K-Means and Fuzzy based Hybrid Clustering Algorithm for WSN

Wireless Sensor Networks (WSN) acquired a lotof attention due to their widespread use in monitoring hostileenvironments, critical surveillance and security applications. Inthese applications, usage of wireless terminals also has grownsignificantly. Grouping of Sensor Nodes (SN) is called clusteringand these sensor nodes are burdened by the exchange of messagescaused due to successive and recurring re-clustering, whichresults in power loss. Since most of the SNs are fitted with nonrechargeablebatteries, currently researchers have been concentratingtheir efforts on enhancing the longevity of these nodes. Forbattery constrained WSN concerns, the clustering mechanism hasemerged as a desirable subject since it is predominantly good atconserving the resources especially energy for network activities.This proposed work addresses the problem of load balancingand Cluster Head (CH) selection in cluster with minimum energyexpenditure. So here, we propose hybrid method in which clusterformation is done using unsupervised machine learning based kmeansalgorithm and Fuzzy-logic approach for CH selection

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

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

Comparitive clinical study on the effect of Mahatriphaladi Ghrita Tarpana and Jeevantyadi Ghrita Tarpana in Parathama Patalagata Timira w.r.t. Keratoconus

Keratonus is one of the important causes of progressive myopia and its incidence is 1 in 500 worldwide. Keratoconus is a degenerative disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than the more normal gradual curve. Keratoconus typically starts at puberty as a progressive myopia causing substantial distortion of vision and marked astigmatism rapidly. This results in significant visual impairment leading to problems in doing routine works like driving and reading. Only temporary measures like Contact lenses and Surgery are available. In Ayurvedic terms, it can be correlated with Prathama Patalagata Timira. As Tarpana is considered to be supreme among all the Kriyakalpas in treating timira, it has been selected for the study. Giving due importance to the doshas and the site of pathology involved, Jeevantyadi Ghrita and Mahatriphaladi Ghrita are selected. Hence a clinical study has been done to compare the efficacies of Mahatriphaladi ghrita tarpana and Jeevantyadi Ghrita tarpana in Keratoconus

Stubble height and fertilizer N requirements for maximizing canola yield in the semiarid Canadian prairie

Non-Peer ReviewedCanola is becoming a viable crop when grown under fallow in the semiarid prairie, but is also grown in longer rotations, most often direct seeded into standing stubble. Taller standing stubble provides the canola seedlings with a more favorable micro-climate promoting more efficient use of water and increased yields compared to canola grown without the protection of standing stubble. When grown under the more limited moisture conditions of extended rotations but in the moisture conserving characteristics of taller standing stubble, we found canola yielded best with fertilizer N rates similar to those of the moister Black soil zone. Canola yields were consistently highest when fertilized with > 100 kg N ha-1

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