Electric-field control of magnetic domain wall motion and local magnetization reversal

Spintronic devices currently rely on magnetic switching or controlled motion of domain walls by an external magnetic field or spin-polarized current. Achieving the same degree of magnetic controllability using an electric field has potential advantages including enhanced functionality and low power consumption. Here, we report on an approach to electrically control local magnetic properties, including the writing and erasure of regular ferromagnetic domain patterns and the motion of magnetic domain walls, in multiferroic CoFe-BaTiO3 heterostructures. Our method is based on recurrent strain transfer from ferroelastic domains in ferroelectric media to continuous magnetostrictive films with negligible magnetocrystalline anisotropy. Optical polarization microscopy of both ferromagnetic and ferroelectric domain structures reveals that domain correlations and strong inter-ferroic domain wall pinning persist in an applied electric field. This leads to an unprecedented electric controllability over the ferromagnetic microstructure, an accomplishment that produces giant magnetoelectric coupling effects and opens the way to multiferroic spintronic devices.Comment: 6 pages, 4 figure

Harmful and beneficial aspects of Parthenium hysterophorus: an update

Parthenium hysterophorus is a noxious weed in America, Asia, Africa and Australia. This weed is considered to be a cause of allergic respiratory problems, contact dermatitis, mutagenicity in human and livestock. Crop production is drastically reduced owing to its allelopathy. Also aggressive dominance of this weed threatens biodiversity. Eradication of P. hysterophorus by burning, chemical herbicides, eucalyptus oil and biological control by leaf-feeding beetle, stem-galling moth, stem-boring weevil and fungi have been carried out with variable degrees of success. Recently many innovative uses of this hitherto notorious plant have been discovered. Parthenium hysterophorus confers many health benefits, viz remedy for skin inflammation, rheumatic pain, diarrhoea, urinary tract infections, dysentery, malaria and neuralgia. Its prospect as nano-medicine is being carried out with some preliminary success so far. Removal of heavy metals and dye from the environment, eradication of aquatic weeds, use as substrate for commercial enzyme production, additives in cattle manure for biogas production, as biopesticide, as green manure and compost are to name a few of some other potentials. The active compounds responsible for hazardous properties have been summarized. The aim of this review article is to explore the problem P. hysterophorus poses as a weed, the effective control measures that can be implemented as well as to unravel the latent beneficial prospects of this weed

Anomalous variation of magnetoresistance in Nd0.67−yEuySr0.33Mn03Nd_{0.67-y}Eu_ySr_{0.33}Mn_{03} manganites

A systematic investigation of Eu-doped Nd-based colossal magnetoresistive manganites with compositional formula $Nd_{0.67-y}Eu_ySr_{0.33}Mn_{03}$ (y = 0–0.67) has been undertaken to understand their structural, magnetic as well as electrical behavior. These materials were prepared by the citrate gel route, and were later characterized by X-ray diffraction (XRD), AC susceptibility, electrical resistivity etc; measurements. A detailed structural characterization of the XRD data has also been undertaken, using Rietveld refinement method. From a systematic analysis of electrical resistivity versus temperature data, it has been found that the last two samples of the series (y = 0.57 and 0.67) are found to exhibit charge order (CO) phenomenona, and that the CO state melts completely in the case of former sample (y = 0.57) while it melts partially only in the case of later one (y = 0.67), even in a magnetic field of 7 T. The observed behavior has been explained qualitatively. Some of the samples of the series are found to exhibit unusually large magnetoresistance over a wide temperature range in the low temperature region, and their behavior has been explained on the basis of phase segregation and an inter-grain spin polarized tunneling effect

Influence of A-site cation mismatch on structural, magnetic and electrical properties of lanthanum manganites

With a view to understand the influence of cation mismatch on magnetic as well as electrical behavior of colossal magnetoresistive materials, a systematic investigation of $La_{0.67}D_{0.33}MnO_3$ (D = Ca, Sr, Pb and Ba) manganite perovskites has been undertaken. The materials were prepared by sol–gel route sintering at $900^oC$ and after usual structural characterization by X-ray diffraction (XRD), their metal–insulator transition $(T_P)$ as well as magnetic transition $(T_C)$ temperatures were determined. The XRD data have been analyzed by Rietveld refinement technique. It has been concluded that apart from A-site cation, the size variance factor $(\sigma^2)$ also influences $T_P$ and $T_C$ values. The extrinsic nature of magnetoresistance in ferromagnetic metallic region is explained on the basis of inter-grain spin polarized tunneling effect. A systematic analysis of electrical resistivity data were carried out using theoretical models to understand the conduction mechanism. It has been concluded that the electrical resistivity data in the ferromagnetic (metallic) regime $(T < T_P)$ may be explained by domain or grain boundary and single magnon scattering processes, while the adiabatic small polaron and variable range hopping models may be used to explain the resistivity data of high temperature paramagnetic insulating region $(T > T_P)$

Influence of particle size on electrical transport properties of La0.67Sr0.33MnO3La_{0.67}Sr_{0.33}MnO_3 manganite system

A systematic investigation of lanthanum-based manganite, $La_{0.67}Sr_{0.33}MnO_3$, has been undertaken with a view to understand the influence of varying particle sizes on electrical transport properties. With a view to obtain materials with varying particle size, they were prepared by sol-gel route, sintering at four different temperatures. The samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD data has been analyzed by Rietveld refinement technique and it has been confirmed that the materials have rhombohedral crystal structure with R (3) over barc space group. Metal-insulator transition temperatures $(T_p)$ were found to decrease continuously with decreasing particle size where as ferro to paramagnetic transition temperatures $(T_c)$ are found to remain constant. The magnetoresistance (MR) values are found to increase with decreasing particle size. With a view to understand the conduction mechanism, the electrical resistivity data have been analyzed both in the ferromagnetic metallic $(T < T_p)$ as well as high temperature paramagnetic insulating $(T > T_p)$ regions

Effect of sintering temperature on electrical transport properties of La<SUB>0.67</SUB>Ca<SUB>0<SUB>.33</SUB></SUB>B>MnO<SUB>3</SUB>

A systematic investigation of lanthanum-based manganite, La0.67Ca0.33MnO3, has been undertaken with a view to understand the influence of varying crystallite size, in the nanoscale, on various physical properties. The materials were prepared by the sol-gel route by sintering at four different temperatures starting from 800 to 1100 &#176; C, with an interval of 100 &#176;C. After the usual characterization of these materials structurally by XRD, their metal-insulator transition (TP) as well as magnetic transition (TC) temperatures were determined. Surprisingly these materials are found to exhibit two different types of behaviors, viz, while TC is found to decrease from 253 to 219 K, TP is increasing from 145 to 195 K with increasing sintering temperature. A systematic study of electrical conductivity of all four materials was undertaken not only as a function of temperature (80-300 K), but also as a function of magnetic field up to 7 T mainly to understand the detailed conduction mechanism in these materials. On analyzing the data by using several theoretical models, it has been concluded that the metallic (ferromagnetic) part of the resistivity (&#961;) (below TP) fits well with the equation &#961;(T)=&#961;0+&#961;2.5T2.5, indicating the importance of grain/domain boundary effects (&#961;0) and electron-magnon scattering processes (~T2.5). On the other hand, in the high temperature (T&gt;TP) paramagnetic insulating regime, the adiabatic small polaron and VRH models fit well in different temperature regions, thereby indicating that polaron hopping might be responsible for the conduction mechanism

Conformationally restricted novel pyrazole derivatives: synthesis of 1,8-disubstituted 5,5-dimethyl-4,5-dihydro-1H-benzo[g]indazoles as a new class of PDE4 inhibitors

A number of novel 1,8-disubstituted 5,5-dimethyl-4,5-dihydro-1H-benzo[g]indazoles based on a conformationally restricted pyrazole framework have been designed as potential inhibitors of PDE4. All these compounds were readily prepared by using simple chemistry strategy. The in vitro PDE4B inhibitory properties and molecular modeling studies of some of the compounds synthesized along with the X-ray single crystal data of a representative compound is presented