Very large spontaneous electric polarization in BiFeO3 single crystals at room temperature and its evolution under cycling fields

Electric polarization loops are measured at room temperature on highly pure BiFeO3 single crystals synthesized by a flux growth method. Because the crystals have a high electrical resistivity, the resulting low leakage currents allow us to measure a large spontaneous polarization reaching 100 microC.cm^{-2}, a value never reported in the bulk. During electric cycling, the slow degradation of the material leads to an evolution of the hysteresis curves eventually preventing full saturation of the crystals.Comment: 8 pages, 3 figure

Macroeconomic Determinants of Liquidity of the Bond Market in Africa: Case Study of South Africa

The importance of the bond market to the financial system and broader economy of a country cannot be underestimated. Thus this study seeks to establish the determinants of liquidity in the South African bond market using monthly data covering the period 1995 to 2009, employing the Johansen cointegration test and the Vector Error Correction Model. Empirical results reveal that there is a longterm relationship between the selected macroeconomic variables and bond market liquidity in South Africa. Based on the empirical results, it is recommended that authorities should keep inflation at low and stables levels as well as a stable currency. Of great importance in the study is the role played by foreign investors in the bond market. The positive impact of the foreign investor participation on the bond market liquidity in South Africa suggests that authorities should remove restrictions on foreign investor activities to enhance liquidity in this important market

Doping dependence of the lattice dynamics in Ba(Fe1−x_{1-x}Cox_x)2_2As2_2 studied by Raman spectroscopy

We report Raman scattering spectra of iron-pnictide superconductor Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ single crystals with varying cobalt $x$ content. Upon cooling through the tetragonal-to-orthorhombic transition, we observe a large splitting of the E$_g$ in-plane phonon modes involving Fe and As displacements. The splitting of the in-plane phonons at the transition is strongly reduced upon doping and disappears for $x=0.06$ qualitatively following the trend displayed by the Fe magnetic moment. The origin of the splitting is discussed in terms of magnetic frustration inherent to iron-pnictide systems and we argue that such enhanced splitting may be linked to strong spin-phonon coupling.Comment: 6 pages, 6 figure

Impact of the Spin Density Wave Order on the Superconducting Gap of Ba(Fe1−x_{1-x}Cox_x)2_2As2_2

We report a doping dependent electronic Raman scattering measurements on iron-pnictide superconductor Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ single crystals. A strongly anisotropic gap is found at optimal doping for x=0.065 with $\Delta_{max}\sim 5\Delta_{min}$. Upon entering the coexistence region between superconducting (SC) and spin-density-wave (SDW) orders, the effective pairing energy scale is strongly reduced. Our results are interpreted in terms of a competition between SC and SDW orders for electronic state at the Fermi level. Our findings advocate for a strong connection between the SC and SDW gaps anisotropies which are both linked to interband interactions.Comment: 4 pages, 3 figure

The nodal gap component as a good candidate for the superconducting order parameter in cuprates

Although more than twenty years have passed since the discovery of high temperature cuprate superconductivity, the identification of the superconducting order parameter is still under debate. Here, we show that the nodal gap component is the best candidate for the superconducting order parameter. It scales with the critical temperature $T_c$ over a wide doping range and displays a significant temperature dependence below $T_c$ in both the underdoped and the overdoped regimes of the phase diagram. In contrast, the antinodal gap component does not scale with $T_c$ in the underdoped side and appears to be controlled by the pseudogap amplitude. Our experiments establish the existence of two distinct gaps in the underdoped cuprates

MGS accelerometer data analysis with the LMD GCM

Mars Global Surveyor aerobreaking phases, required to achieve its mapping orbit, have yielded vertical profiles of thermospheric densities, scale heights and temperatures covering a broad range of local times, seasons and spatial coordinates [Keating et al. 1998, 2001]. Phase I covered local times from 11 to 16 h (assuming 24 "martian hours” per martian day or sols), with a latitude coverage of approximately 40deg to 60deg N. Seasons observed during this phase were centered around winter solstice and altitudes of periapsis range from 115 to 135 km. The altitudes for Phase II were lower, with a minimum around 100 km and a maximum around 120. Martian spring was the season covered during this phase and the local time was between 15 and 16 h. The latitude covered by Phase II, however, was more extense than that seen during Phase I, with a coverage from 60deg N to basically the South Pole

Financial Development and Income Inequality in the Selected Southern African Development Community Countries

Financial development is widely regarded as another conduit through which income inequality can be reduced. The study empirically examines the relationship between financial development and income inequality in selected Southern African Development Community (SADC) countries, employing the Generalised Method of Moments technique for the period 1980 to 2016. Based on the inequality-decreasing hypothesis, a model which links financial sector development and inequality was estimated. Empirical results revealed that financial sector development overall does have an impact on income inequality in the selected SADC countries. An interesting observation from the empirical results is that the actual dimension of financial development plays a significant role in determining the relationship between financial development and income inequality in the SADC region. The impact of financial depth on income inequality is not obvious in the study, depending on the variable used. On the relationship between financial system stability and income inequality, results reveal that a stable financial system is beneficial to the poor. Financial efficiency does not appear to have a significant role in reducing income inequality in the selected SADC countries. The findings imply that a specific approach to financial sector development rather than a blanket approach is desirable

Financial Sector Development and Poverty Alleviation in the SADC Region

Financial development is widely regarded as another conduit through which poverty can be reduced. The study empirically examines the relationship between financial sector development and poverty reduction in SADC countries utilising the Generalised Method of Moments technique for the period 1980 to 2017. The empirical results indicate that the effect of the different measures of financial sector development on poverty in the SADC region is mixed. Six out of nine financial development variables have a negative effect on poverty in the SADC region. In terms of financial depth, the empirical results reveal mixed outcomes. Results on financial system stability confirm the notion that a stable financial system is beneficial to the poor. The results also reveal that financial inclusion or access to financial services significantly reduces poverty in the SADC region. The results thus suggest that financial sector development is beneficial to the poor when it is inclusive and stable. The results imply that policies aimed at ensuring a stable financial system, which is also inclusive, should be pursued if the poor are to benefit from the financial system