Magnetic properties of PrCu2_2 at high pressure

We report a study of the low-temperature high-pressure phase diagram of the intermetallic compound PrCu$_2$, by means of molecular-field calculations and $^{63,65}$Cu nuclear-quadrupole-resonance (NQR) measurements under pressure. The pressure-induced magnetically-ordered phase can be accounted for by considering the influence of the crystal electric field on the $4f$ electron orbitals of the Pr$^{3+}$ ions and by introducing a pressure-dependent exchange interaction between the corresponding local magnetic moments. Our experimental data suggest that the order in the induced antiferromagnetic phase is incommensurate. The role of magnetic fluctuations both at high and low pressures is also discussed.Comment: 7 pages, 6 figures, submitted to Eur. Phys. J.

Power, participation and partnership: methodological reflection on researching professional doctorate candidates' experiences of researching in the workplace

This study aimed to explore the candidate experience in order to understand more deeply aspects of the development in work based research. Delphi technique was chosen as an approach in order to capture a range of experience and data, to inform how we may best support candidates on practice based doctorates. Many such programmes include a stakeholder learning agreement between the candidate, the university and the employer organisation with the common aim to bring about transformational and sustainable change. Our research to date indicates a disparity within the agreement in the level of stakeholder participation. Where the organisation stakeholder is not fully engaged and involved in supporting the research, there is a potential threat to the effectiveness of any change outcome. Current practice based doctoral research participants were invited to relate to a range of temporal themes in their research project cycle, for example: setting up the project; implementing the project; changes/ contingency planning within the project; project completion and post completion. Of particular interest in relation to the above was the availability of resources and how they were used within the project life cycle. In this respect, resources are deemed to include, human, material, time, personal and organisational culture influence. The allocation, manipulation and distribution of such resources can be understood in terms of power relationships. The paper presents our experience and reflections from two iterative Delphi cycles and proposes a final stage of greater integration with existing academic resources within the professional doctorate programme. The study has enabled the researchers to gain a new understanding of how power may operate in a work based research project through the experience of undertaking the Delphi approach. Furthermore, by thinking about affordances of the project life cycle, it may help us to better understand needs and strategy for the curriculum in order to more effectively support candidates through their transformational learning experience. The consequences of such change might have implications for participation and power distribution within the management and leadership of doctoral work base research projects

Deuteron Compton Scattering in Effective Field Theory: Spin-Dependent Cross Sections and Asymmetries

Polarized Compton scattering on the deuteron is studied in nuclear effective field theory. A set of tensor structures is introduced to define 12 independent Compton amplitudes. The scalar and vector amplitudes are calculated up to ${\cal O}((Q/\Lambda)^2)$ in low-energy power counting. Significant contribution to the vector amplitudes is found to come from the spin-orbit type of relativistic corrections. A double-helicity dependent cross section $\Delta_1 \sigma = (\sigma_{+1-1}-\sigma_{+1+1})/2$ is calculated to the same order, and the effect of the nucleon isoscalar spin-dependent polarizabilities is found to be smaller than the effect of isoscalar spin-independent ones. Contributions of spin-independent polarizabilities are investigated in various asymmetries, one of which has as large as 12 (26) percent effect at the center-of-mass photon energy 30 (50) MeV.Comment: 22 pages, 8 figures included, replaced with the version submitted to PR

Structure of plastically compacting granular packings

The developing structure in systems of compacting ductile grains were studied experimentally in two and three dimensions. In both dimensions, the peaks of the radial distribution function were reduced, broadened, and shifted compared with those observed in hard disk- and sphere systems. The geometrical three--grain configurations contributing to the second peak in the radial distribution function showed few but interesting differences between the initial and final stages of the two dimensional compaction. The evolution of the average coordination number as function of packing fraction is compared with other experimental and numerical results from the literature. We conclude that compaction history is important for the evolution of the structure of compacting granular systems.Comment: 12 pages, 12 figure

Magnetic properties of PrCu2 at high pressure

We report a study of the low-temperature high-pressure phase diagram of the intermetallic compound PrCu2, by means of molecular-field calculations and 63,65Cu nuclear-quadrupole-resonance (NQR) measurements under pressure. The pressure-induced magnetically-ordered phase can be accounted for by considering the influence of the crystal electric field on the 4f electron orbitals of the Pr3+ ions and by introducing a pressure-dependent exchange interaction between the corresponding local magnetic moments. Our experimental data suggest that the order in the induced antiferromagnetic phase is incommensurate. The role of magnetic fluctuations both at high and low pressures is also discusse

Proton spin polarizabilities from polarized Compton scattering

Polarized Compton scattering off the proton is studied within the framework of subtracted dispersion relations for photon energies up to 300 MeV. As a guideline for forthcoming experiments, we focus the attention on the role of the proton's spin polarizabilities and investigate the most favorable conditions to extract them with a minimum of model dependence. We conclude that a complete separation of the four spin polarizabilities is possible, at photon energies between threshold and the $\Delta(1232)$ region, provided one can achieve polarization measurements with an accuracy of a few percent.Comment: 26 pages, 7 figures