Muons and magnets

Abstract:

We report magnetoconductance measurements on two metallic 60 % PANI-CSA films at fields of up to 15 Tesla. Our results are generally consistent with measurements on other conducting PANI-CSA samples reported by Menon et. al.(1) at lower magnetic fields. However, there are some deviations at low temperatures and high magnetic fields which suggest the need for further detailed investigation.

Abstract:

The muon is a valuable probe of spin excitations in polymers, as the muon implantation process itself generates a lest excitation whose dynamical properties can be studied via the evolution of the muon spin polarisation. We report here studies on undoped polyaniline in its emeraldine base form (PANI:EB). Characteristic field dependences and cutoff frequencies for the muon spin relaxation are observed which are related to the spin diffusion. One-dimensional diffusion is seen at low temperatures and at short probe times. The on chain diffusion is observed to have a weak metallic temperature dependence whereas the interchain diffusion is strongly activated and phenyl ring rotations are seen to have an important effect on the diffusion processes.

Abstract:

The crystallography and electronic properties of the Ln(2-x)Sr(1+x)Mn(2)O(7) manganese oxides adopting the n = 2 Ruddlesden-Popper (RP) structure are discussed, focusing on the structural phase diagrams and electronic properties in the vicinity of the Mn + 3.5 oxidation slate and in particular the ease of synthesis of single phases of these materials.

Abstract:

We report the results of magnetization, susceptibility and muon spin rotation/relaxation (mu SR) measurements and crystal structure analyses of the organic neutral and ion radicals based on nitronyl nitroxide. Magneto-structural correlations in naphthyl and quinolyl nitronyl nitroxides, some of which exhibit ferromagnetic intermolecular interactions, are discussed in terms of intermolecular and interatomic contacts. The temperature dependence of the paramagnetic susuceptibility of sodium 2-sulfonatofuryl nitronyl nitroxide and 2-carboxyfuryl nitronyl nitroxide are interpreted in terms of a combination of ferromagnetic and antiferromagnetic interactions. Of the organic radicals exhibiting ferromagnetic intermolecular interactions, magnetic transitions in the zero-field muon spin relaxation are observed in l-naphthyl and p-cyanophenyl nitronyl nitroxide below 0.10 and 0.17 K, respectively.