Incommensurate phases in ferromagnetic spin-chains with weak antiferromagnetic interchain interaction

We study planar ferromagnetic spin-chain systems with weak antiferromagnetic inter-chain interaction and dipole-dipole interaction. The ground state depends sensitively on the relative strengths of antiferromagnetic exchange and dipole energies kappa=J'a^2c/(g_L\mu_B)^2. For increasing values of \kappa, the ground state changes from a ferromagnetic via a collinear antiferromagnetic and an incommensurate phase to a 120^o structure for very large antiferromagnetic energy. Investigation of the magnetic phase diagram of the collinear phase, as realized in CsNiF_3, shows that the structure of the spin order depends sensitivly on the direction of the magnetic field in the hexagonal plane. For certain angular domains of the field incommensurate phases appear which are separated by commensurate phases. When rotating the field, the wave vector characterizing the structure changes continuously in the incommensurate phase, whereas in the commensurate phase the wave vector is locked to a fixed value describing a two-sublattice structure. This is a result of the competition between the exchange and the dipole-dipole interaction.Comment: 12 pages, ReVTeX, 13 figures, to be published in Z. Physi

Phase diagram and magnons in quasi-one-dimensional dipolar antiferromagnets

We investigate antiferromagnetic spin chains, which are coupled by a weak antiferromagnetic exchange interaction on a hexagonal lattice. We particulary study the role of the dipole-dipole interaction within the framework of a Heisenberg model with nearest-neighbor exchange and additional dipolar interaction. We find several commensurate and incommensurate phases depending on the ratio of dipolar energy to interchain-exchange energy due to their competing qualtity. The ground-state analysis is supplemented by a stability analysis by means of a linear spin-wave theory. In comparison with experiments (CsMnBr_3, RbMnBr_3) we obtain good agreement for the energy gaps. From this we conclude, that the dipolar interaction is the most important source of anisotropy in these Mn-compounds.Comment: 3 pages, 3 Postscript figure

Understanding the role of social media in political corporate branding research in the context of Indian politics

This paper seeks to explore how political actors within the Bharatiya Janata Party (BJP) use social media in their communication campaigns and how these social media platforms are understood by citizens following the 2014 Indian General Election. This research attempts to address the limited understanding of social media in the context of politics (Barnard and Kreiss, 2013; Burton and Shea, 2010; Cogburn and Espinoza-Vasquez 2011; Ganz, 2009; Gulati and Williams, 2007; Kumar 2009; Owen and Davis 2008). Furthermore, the limited research on political branding and social media has predominantly focused a western context negating eastern perspectives including the republic of India. This study will use the adapted Kapferer’s (2008) brand identity prism developed by Pich et al. (2014) to a political setting. This framework will ground the study and offer the opportunity to examine the role of social media from an internal brand identity and external brand image perspective. The findings will have implications not only for political parties but also for politicians, candidates and other parties interested in social media. This study will offer organisations a mechanism that will allow them understand how their social media is projected and understood and allow them to investigate whether their projected brand identity is coherent with the understood external brand image

Enhancing data collection methods with qualitative projective techniques in the exploration of a university’s brand identity and brand image

This paper focuses on assessing the capabilities of projective techniques, in gaining a deeper insight into complex university corporate brands. In particular we will explore identities and how these might align with brand images in different departments and faculties. There are explicit calls for further research on projective techniques in new contexts in particular, and where and when they are most useful during data collection. Responding to this gap in the literature, this study adopts a two-staged approach to the research design utilising qualitative projective techniques as a supplement to more traditional methods of data collection. This paper provides an updated matrix on how qualitative projective techniques can be better utilised during the planning, research and analysis stages of research in different contexts. This can be employed to assist inexperienced and experienced individuals with projective techniques during the planning, research and analysis stages of research into corporate brands

Alternating commensurate-incommensurate structures in the magnetic phase diagram of CsNiF3

The magnetic phase diagram of the quasi one-dimensional spinchain system CsNiF$_3$ below the N\'eel temperature is determined. For magnetic fields perpendicular to the spin chains incommensurate phases are predicted. From linear spin-wave theory we obtain the instability line of the paramagnetic phase as a function of the strength and the direction of the field. The system undergoes a transition to a commensurate or an incommensurate phase depending on the direction of the magnetic field. In the commensurate phase the characterizing wave vector is locked to values describing a two-sublattice structure, whereas in the incommensurate phase the wave vector changes continuously between the corresponding two-sublattice wave vectors.Comment: 11 pages, LaTeX, 5 figures, sent to PRB Rapid Communicatio

Charm-quark mass from weighted finite energy QCD sum rules

The running charm-quark mass in the $\bar{MS}$ scheme is determined from weighted finite energy QCD sum rules (FESR) involving the vector current correlator. Only the short distance expansion of this correlator is used, together with integration kernels (weights) involving positive powers of $s$, the squared energy. The optimal kernels are found to be a simple {\it pinched} kernel, and polynomials of the Legendre type. The former kernel reduces potential duality violations near the real axis in the complex s-plane, and the latter allows to extend the analysis to energy regions beyond the end point of the data. These kernels, together with the high energy expansion of the correlator, weigh the experimental and theoretical information differently from e.g. inverse moments FESR. Current, state of the art results for the vector correlator up to four-loop order in perturbative QCD are used in the FESR, together with the latest experimental data. The integration in the complex s-plane is performed using three different methods, fixed order perturbation theory (FOPT), contour improved perturbation theory (CIPT), and a fixed renormalization scale $\mu$ (FMUPT). The final result is $\bar{m}_c (3\, {GeV}) = 1008\,\pm\, 26\, {MeV}$, in a wide region of stability against changes in the integration radius $s_0$ in the complex s-plane.Comment: A short discussion on convergence issues has been added at the end of the pape