Socioeconomic Distance as a Determinant of Female Autonomy and Child Welfare

We quantify the impact of network-based learning and influence on measures of female power and child nutrition in rural India. Empowering women to have greater say in child rearing may generate greater and more lasting benefits to children than nutrition supplementation. While researchers have used proxy reports or correlates like caste to trace networks, we map networks by surveying friends of respondents. We use participation in a women's education program to identify increases in female power, as well as stronger and more diverse networks. We study the ways in which networks affect individuals, namely learning and influence. Finally, we characterize the benefits of using survey data rather than proxies to identify networks. Our results linking networks to child nutrition should also inform child health policy.Consumer/Household Economics, Food Security and Poverty,

On pressure dependence of the relative compression (V/V0) at room temperature for the solids : copper and lead as prototypes

A correction term has been introduced in the usual Tait’s equation of state (EOS) and then used to predict the pressure dependence of the thermal compression for the solids : copper (Cu) and lead (Pb). The predictive capabilities of the complete EOS are discussed. The results obtained from the modified Usual Tait’s equation of state are found closer to the available experimental data as compared to those values achieved without taking into account the correction factor in the original Tait’s equation of state.Author Affiliation: Deepika Kandpal, K Y Singh and B R K Gupta 1.Department of Physics, G. B. Pant University of Agriculture and Technology, Pantnagar-263145, India E-mail : [email protected] of Physics, G. B. Pant University of Agriculture and Technology, Pantnagar-263145, Indi

Investigation of Co2_2FeSi: The Heusler compound with Highest Curie Temperature and Magnetic Moment

This work reports on structural and magnetic investigations of the Heusler compound Co$_2$FeSi. X-Ray diffraction and M\"o\ss bauer spectrometry indicate an ordered $L2_1$ structure. Magnetic measurements by means of X-ray magnetic circular dichroism and magnetometry revealed that this compound is, currently, the material with the highest magnetic moment ($6 \mu_B$) and Curie-temperature (1100K) in the classes of Heusler compounds as well as half-metallic ferromagnets

Kitaev interactions between j=1/2 moments in honeycomb Na2IrO3 are large and ferromagnetic: insights from ab initio quantum chemistry calculations

Na$_2$IrO$_3$, a honeycomb 5$d^5$ oxide, has been recently identified as a potential realization of the Kitaev spin lattice. The basic feature of this spin model is that for each of the three metal-metal links emerging out of a metal site, the Kitaev interaction connects only spin components perpendicular to the plaquette defined by the magnetic ions and two bridging ligands. The fact that reciprocally orthogonal spin components are coupled along the three different links leads to strong frustration effects and nontrivial physics. While the experiments indicate zigzag antiferromagnetic order in Na$_2$IrO$_3$, the signs and relative strengths of the Kitaev and Heisenberg interactions are still under debate. Herein we report results of ab initio many-body electronic structure calculations and establish that the nearest-neighbor exchange is strongly anisotropic with a dominant ferromagnetic Kitaev part, whereas the Heisenberg contribution is significantly weaker and antiferromagnetic. The calculations further reveal a strong sensitivity to tiny structural details such as the bond angles. In addition to the large spin-orbit interactions, this strong dependence on distortions of the Ir$_2$O$_2$ plaquettes singles out the honeycomb 5$d^5$ oxides as a new playground for the realization of unconventional magnetic ground states and excitations in extended systems.Comment: 13 pages, 2 tables, 3 figures, accepted in NJ

Covalent bonding and the nature of band gaps in some half-Heusler compounds

Half-Heusler compounds \textit{XYZ}, also called semi-Heusler compounds, crystallize in the MgAgAs structure, in the space group $F\bar43m$. We report a systematic examination of band gaps and the nature (covalent or ionic) of bonding in semiconducting 8- and 18- electron half-Heusler compounds through first-principles density functional calculations. We find the most appropriate description of these compounds from the viewpoint of electronic structures is one of a \textit{YZ} zinc blende lattice stuffed by the \textit{X} ion. Simple valence rules are obeyed for bonding in the 8-electron compound. For example, LiMgN can be written Li$^+$ + (MgN)$^-$, and (MgN)$^-$, which is isoelectronic with (SiSi), forms a zinc blende lattice. The 18-electron compounds can similarly be considered as obeying valence rules. A semiconductor such as TiCoSb can be written Ti$^{4+}$ + (CoSb)$^{4-}$; the latter unit is isoelectronic and isostructural with zinc-blende GaSb. For both the 8- and 18-electron compounds, when \textit{X} is fixed as some electropositive cation, the computed band gap varies approximately as the difference in Pauling electronegativities of \textit{Y} and \textit{Z}. What is particularly exciting is that this simple idea of a covalently bonded \textit{YZ} lattice can also be extended to the very important \textit{magnetic} half-Heusler phases; we describe these as valence compounds \textit{ie.} possessing a band gap at the Fermi energy albeit only in one spin direction. The \textit{local} moment in these magnetic compounds resides on the \textit{X} site.Comment: 18 pages and 14 figures (many in color

Correlation in the transition metal based Heusler compounds Co2_2MnSi and Co2_2FeSi

Half-metallic ferromagnets like the full Heusler compounds with formula X$_2$YZ are supposed to show an integer value of the spin magnetic moment. Calculations reveal in certain cases of X = Co based compounds non-integer values, in contrast to experiments. In order to explain deviations of the magnetic moment calculated for such compounds, the dependency of the electronic structure on the lattice parameter was studied theoretically. In local density approximation (LDA), the minimum total energy of Co$_2$FeSi is found for the experimental lattice parameter, but the calculated magnetic moment is about 12% too low. Half-metallic ferromagnetism and a magnetic moment equal to the experimental value of $6\mu_B$ are found, however, only after increasing the lattice parameter by more than 6%. To overcome this discrepancy, the LDA$+U$ scheme was used to respect on-site electron correlation in the calculations. Those calculations revealed for Co$_2$FeSi that an effective Coulomb-exchange interaction $U_{eff}=U-J$ in the range of about 2eV to 5eV leads to half-metallic ferromagnetism and the measured, integer magnetic moment at the measured lattice parameter. Finally, it is shown in the case of Co$_2$MnSi that correlation may also serve to destroy the half-metallic behavior if it becomes too strong (for Co$_2$MnSi above 2eV and for Co$_2$FeSi above 5eV). These findings indicate that on-site correlation may play an important role in the description of Heusler compounds with localized moments.Comment: submitted to Phys. Rev.

Ferrimagnetism and disorder in epitaxial Mn(2-x)Co(x)VAl thin films

The quaternary full Heusler compound Mn(2-x)Co(x)VAl with x = 1 is predicted to be a half-metallic antiferromagnet. Thin films of the quaternary compounds with x = 0...2 were prepared by DC and RF magnetron co-sputtering on heated MgO (001) substrates. The magnetic structure was examined by x-ray magnetic circular dichroism and the chemical disorder was characterized by x-ray diffraction. Ferrimagnetic coupling of V to Mn was observed for Mn2VAl (x = 0). For x = 0.5, we also found ferrimagnetic order with V and Co antiparallel to Mn. The observed reduced magnetic moments are interpreted with the help of band structure calculations in the coherent potential approximation. Mn2VAl is very sensitive to disorder involving Mn, because nearest-neighbor Mn atoms couple anti-ferromagnetically. Co2VAl has B2 order and has reduced magnetization. In the cases with x >= 0.9 conventional ferromagnetism was observed, closely related to the atomic disorder in these compounds.Comment: 10 pages, 4 figure

Revision of model parameters for kappa-type charge transfer salts: an ab initio study

Intense experimental and theoretical studies have demonstrated that the anisotropic triangular lattice as realized in the kappa-(BEDT-TTF)2X family of organic charge transfer (CT) salts yields a complex phase diagram with magnetic, superconducting, Mott insulating and even spin liquid phases. With extensive density functional theory (DFT) calculations we refresh the link between manybody theory and experiment by determining hopping parameters of the underlying Hubbard model. This leads us to revise the widely used semiempirical parameters in the direction of less frustrated, more anisotropic triangular lattices. The implications of these results on the systems' description are discussed.Comment: Accepted for pupblication in Phys. Rev. Let