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Homonuclear Separated Local-Field Spectroscopy by Magnetization-Exchange NMR

100%

Demco D. E., Filip X., Filip C., Chira D., Cozar O.

Acta Physica Polonica A

1997

vol. 92

issue 6

1135-1149

The possibility to perform homonuclear separated-local field NMR spectroscopy by magnetization-exchange is presented. Solid-state one-dimensional proton magnetization-exchange NMR is used to investigate intergroup residual dipolar couplings in cis-1,4-polybutadiene elastomer. A three-spin model is employed, in which the CH- and CH_{2}-protons are considered to be coupled by residual dipolar interactions. The magnetization-exchange process between the CH- and the CH_{2}-group in the regime of short mixing time provides valuable insight regarding molecular order. The spin-system response reflects well-localized dipolar interactions. The residual intergroup dipolar couplings are measured along the average polymer-chain direction for different temperatures. The dynamic order parameter along the chains is also evaluated.

Influence of the Grain Size on Polaron Transport in Nanostructured La_{2/3}Ca_{1/3}MnO_3 Evidenced by EPR

86%

Raita O., Grecu M., Filip X., Toloman D., Giurgiu L., Idziak S., Hoffmann S.

Acta Physica Polonica A

2005

vol. 108

issue 1

113-118

We report an electron paramagnetic resonance investigation of the grain size effects on the polaron transport in the paramagnetic regime of nanosized La_{2/3} Ca_{1/3}MnO_3 manganites. The temperature dependences of the EPR integral intensity were analyzed in terms of spin-spin exchange interaction and small polaron hopping scenarios. The polaron activation energy decreases with the reduction of the grain size. A discussion is given concerning the factors which could explain the observed change.

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2 Acta Physica Polonica A

1 2005

1 1997

2 Filip X.

1 Chira D.

1 Cozar O.

1 Demco D. E.

1 Filip C.

1 Giurgiu L.

1 Grecu M.

1 Hoffmann S.

1 Idziak S.

1 Raita O.

1 Toloman D.

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Homonuclear Separated Local-Field Spectroscopy by Magnetization-Exchange NMR

Influence of the Grain Size on Polaron Transport in Nanostructured La_{2/3}Ca_{1/3}MnO_3 Evidenced by EPR