Effect of field dependent core size on reversible magnetization of high-κ\kappa superconductors

The field dependence of the vortex core size $\xi(B)$ is incorporated in the London model, in order to describe reversible magnetization $M(B,T)$ for a number of materials with large Ginzburg-Landau parameter $\kappa$. The dependence $\xi(B)$ is directly related to deviations in $M(\ln B)$ from linear behavior prescribed by the standard London model. A simple method to extract $\xi(B)$ from the magnetization data is proposed. For most materials examined, $\xi(B)$ so obtained decreases with increasing field and is in qualitative agreement both with behavior extracted from $\mu$SR and small angle neutron scattering data and with that predicted theoretically

Gender, war and militarism: making and questioning the links

The gender dynamics of militarism have traditionally been seen as straightforward, given the cultural mythologies of warfare and the disciplining of ‘masculinity’ that occurs in the training and use of men's capacity for violence in the armed services. However, women's relation to both war and peace has been varied and complex. It is women who have often been most prominent in working for peace, although there are no necessary links between women and opposition to militarism. In addition, more women than ever are serving in many of today's armies, with feminists rather uncertain on how to relate to this phenomenon. In this article, I explore some of the complexities of applying gender analyses to militarism and peace work in sites of conflict today, looking most closely at the Israeli feminist group, New Profile, and their insistence upon the costs of the militarized nature of Israeli society. They expose the very permeable boundaries between the military and civil society, as violence seeps into the fears and practices of everyday life in Israel. I place their work in the context of broader feminist analysis offered by researchers such as Cynthia Enloe and Cynthia Cockburn, who have for decades been writing about the ‘masculinist’ postures and practices of warfare, as well as the situation of women caught up in them. Finally, I suggest that rethinking the gendered nature of warfare must also encompass the costs of war to men, whose fundamental vulnerability to psychological abuse and physical injury is often downplayed, whether in mainstream accounts of warfare or in more specific gender analysis. Feminists need to pay careful attention to masculinity and its fragmentations in addressing the topic of gender, war and militarism

Bulk electronic structure of superconducting LaRu2P2 single crystals measured by soft x-ray angle-resolved photoemission spectroscopy

We present a soft X-ray angle-resolved photoemission spectroscopy (SX-ARPES) study of the stoichiometric pnictide superconductor LaRu2P2. The observed electronic structure is in good agreement with density functional theory (DFT) calculations. However, it is significantly different from its counterpart in high-temperature superconducting Fe-pnictides. In particular the bandwidth renormalization present in the Fe-pnictides (~2 - 3) is negligible in LaRu2P2 even though the mass enhancement is similar in both systems. Our results suggest that the superconductivity in LaRu2P2 has a different origin with respect to the iron pnictides. Finally we demonstrate that the increased probing depth of SX-ARPES, compared to the widely used ultraviolet ARPES, is essential in determining the bulk electronic structure in the experiment.Comment: 4 pages, 4 figures, 1 supplemental material. Accepted for publication in Physical Review Letter

Single crystal of superconducting SmFeAsO1-xFy grown at high pressure

Single crystals of SmFeAsO1-xFy of a size up to 120 micrometers have been grown from NaCl/KCl flux at a pressure of 30 kbar and temperature of 1350-1450 C using the cubic anvil high-pressure technique. The superconducting transition temperature of the obtained single crystals varies between 45 and 53 K.Obtained crystals are characterized by a full diamagnetic response in low magnetic fields and by a high critical current density in high magnetic fields. Structural refinement has been performed on single crystal. Differential thermal analysis investigations at 1 bar Ar pressure show decomposition of SmFeAsO1-xFy at 1302 C.Comment: 12 pages, 3 tables, 6 figure

Localized versus itinerant magnetic moments in Na0.72CoO2

Based on experimental 59Co-NMR data in the temperature range between 0.1 and 300 K, we address the problem of the character of the Co 3d-electron based magnetism in Na0.7CoO2. Temperature dependent 59Co-NMR spectra reveal different Co environments below 300 K and their differentiation increases with decreasing temperature. We show that the 23Na- and 59Co-NMR data may consistently be interpreted by assuming that below room temperature the Co 3d-electrons are itinerant. Their magnetic interaction appears to favor an antiferromagnetic coupling, and we identify a substantial orbital contribution corb to the d-electron susceptibility. At low temperatures corb seems to acquire some temperature dependence, suggesting an increasing influence of spin-orbit coupling. The temperature dependence of the spin-lattice relaxation rate T1-1(T) confirms significant variations in the dynamics of this electronic subsystem between 200 and 300K, as previously suggested. Below 200 K, Na0.7CoO2 may be viewed as a weak antiferromagnet with TN below 1 K but this scenario still leaves a number of open questions.Comment: 8.7 pages, 6 Figures, submitted to Phys. Rev.

NMR and dc-susceptibility studies of NaVGe2O6

We report the results of measurements of the dc magnetic susceptibility chi(T) and of the 23Na nuclear magnetic resonance (NMR) response of NaVGe2O6, a material in which the V ions form a network of interacting one-dimensional spin S=1 chains. The experiments were made at temperatures between 2.5 and 300 K. The chi(T) data suggest that the formation of the expected low-temperature Haldane phase is intercepted by an antiferromagnetic phase transition at 18 K. The transition is also reflected in the 23Na NMR spectra and the corresponding spin-lattice relaxation rate 1/T1(T). In the ordered phase, 1/T1(T) decreases by orders of magnitude with decreasing temperature, indicating the formation of a gap of the order of 12 K in the magnetic excitation spectrum.Comment: 10 pages, 15 figures; v2 with minor revisions of the tex