Crossover in the nature of the metallic phases in the perovskite-type RNiO_3

We have measured the photoemission spectra of Nd$_{1-x}$Sm$_{x}$NiO$_{3}$, where the metal-insulator transition and the N\'{e}el ordering occur at the same temperature for $x \lesssim 0.4$ and the metal-insulator transition temperature ($T_{MI}$) is higher than the N\'{e}el temperature for $x \gtrsim 0.4$. For $x \le 0.4$, the spectral intensity at the Fermi level is high in the metallic phase above $T_{MI}$ and gradually decreases with cooling in the insulating phase below $T_{MI}$ while for $x > 0.4$ it shows a pseudogap-like behavior above $T_{MI}$ and further diminishes below $T_{MI}$. The results clearly establish that there is a sharp change in the nature of the electronic correlations in the middle ($x \sim 0.4$) of the metallic phase of the $R$NiO$_3$ system.Comment: 4 pages, 4 figure, submitted to Phys. Rev.

Teaching our grandchildren to suck eggs?: Introducing the study of communication technologies to the 'Digital generation'

It has been argued that age-related and generational differences in communication technology use and more generally in learning style and mindset increasingly divide lecturers from students. This paper reports an investigation of one cohort of level 1 students’ current communication practices and learning styles conducted in order to adapt a module in direct response to student need. A small scale survey of communication and web use was undertaken and students completed the Kolb learning style inventory. The results demonstrate that the sweeping generalizations of generational or age related difference are not a firm foundation for pedagogy. For example, familiarity and use of Web2.0 technologies was patchy and students seemed to prefer to be consumers not producers, though they did show a preference for immediate communication. This reinforced our sense of the need to teach students about many Web2.0 technologies, especially the content creation aspects. Students had diverse learning styles and their preferences did not suggest a radical change from the past. The need continues to be to offer a variety of learning opportunities for a diverse student body. The paper demonstrates the value of systematic data collection about students’ existing knowledge and practices and of assessed reflective activities to stimulate students to be more active in negotiating a successful learning experience for themselves

Tuning of Metal/Insulator Transition around Room Temperature of Perovskites Sm1-xNdxNiO3

International audienceWe report here a study of the synthesis and properties of the solid solution series Sm1-xNdxNiO3. It was found to crystallize in the GdFeO3-type orthorhombically distorted perovskite structure, The metal-insulator (M/I) transition was mapped out as a function of the composition, It is possible to control this transition between 200 and 410 K by simply adjusting the composition. For instance, the MII transition occurs at room temperature for Sm0.55Nd0.45NiO3, and the variation of the transition temperature with composition is about 2.3 K/x%. These phase transitions have been studied by differential scanning calorimetry, microwave procedure, and X-ray diffraction. Microwave data reveal hysteresis effects, An interpretation of the experimental results may be the coexistence of the metallic and insulating phases. On the other hand, we have observed that the enthalpy change of phase transition decreases when the powder is ground. This phenomenon can be related to amorphization of the material