TEPON · Thermal and Electronic Properties of Nanotubes (TEPON)

Final Activity Report Summary - TEPON (Thermal and Electronic Properties of Nanotubes)

The main objective of the International Re-Integration Grants (IRGs) is to help stabilise the research career of the grantee. Dr Norbert Nemes spent over six years in the United States before returning to the EU, specifically to Spain. He received a three-year research fellowship from the Spanish Ministry of Education concurrent with the IRG. In recognition of his research activities, in large part helped by the IRG, he was recently awarded an even more prestigious 5-year fellowship by the Ministry. Therefore, Dr Nemes has been successfully stabilised in Spain. An important objective of the IRG is enabling the transfer of knowledge from third countries to the EU. Before Dr Nemes's arrival, Dr Garcia-Hernandez's group had no experience working with nanotubes or other carbon based nanostructures. Now there are several ongoing research directions, involving nanotubes, cubane-fullerene compounds, irradiated graphite, to mention just a few. Dr Nemes also introduced the group the magnetic resonance techniques, such as electron spin resonance and ferromagnetic resonance, and these prove highly useful in several projects, for example in the study of ferromagnetic manganite thin films. There were three main original research objectives, of which two were successfully completed while one was modified to take advantage of advancements in new discoveries. Lastly, a completely new research direction was added. Optical properties of alkali doped SWNT: the most important research objectives were to see the effect of alkali doping of SWNT on their optical properties. We studied this in detail and demonstrated an important shift of the Drude-edge, progressively with alkali doping. Magnetically purified SWNT: a new material, magnetically purified SWNT was developed at the University of Pennsylvania. We successfully studied its magnetic and electronic properties with ESR. In collaboration with Prof. Ferenc Simon of TUB and Prof. Laszlo Forro (EPFL), we discovered interesting super-Curie magnetic behaviour, and an important lengthening of the spin relaxation time at low temperature. We have also started to collaborate on the study of the magnetic and spin resonance properties of alkali doped SWNT, and SWNT based heterostructures, which is an outgrowth of Prof. Simon's own Marie-Curie Fellowship and ERG projects. High temperature thermal conductivity of SWNT: we attempted to measure the thermal conductivity of SWNT using the laser-flash method, but for technical reasons were unable to get useful results. However, we modified this sub-project to take advantage of an exciting new material developed by Dr Sandor Pekker's group (SzFKI), cubane-fullerene compounds, which are related to SWNT, being also carbon based nanostructures. Instead of thermal conductivity, we used calorimetry in their study and investigated a very interesting rotational phase transition, in which the ball like fullerenes stop spinning at low temperature, while the cube like cubanes remain static even at high temperature. Finally, the research program was significantly broadened to better integrate Dr Nemes to the on-going work of the Host group. This new direction forms the basis of his new activities and involves the study of a new filed in device physic: oxide electronics and spintronics. We studied ferromagnet / superconductor based thin film oxide heterostructures, using various techniques and addressed important physical questions, like the nature of spin transport through the superconductor, the role of stray fileds, magnetic anisotropy of the ferromagnet.

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