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Charge-transfer between electron–donor and –acceptor molecules is a widely studied subject of great chemical interest. Some of the charge-transfer compounds in solid state exhibit novel electronic properties. In the last two to three years, occurrence of molecular charge-transfer involving single-walled carbon nanotubes (SWNTs) and graphene has been demonstrated. This interaction gives rise to significant changes in the electronic properties of these nanocarbons. We examine charge-transfer phenomenon in graphene and SWNTs in this article in view of its potential utility in device applications.
We present results of an electron paramagnetic resonance (EPR) study of Nd$_{1-x}$Sr$_x$MnO$_3$ with x = 0.5 across the paramagnetic to ferromagnetic, insulator to metal transition at 260 K (T$_c$) and the antiferromagnetic, charge ordering transition (T$_N$ = T$_{co}$) at 150 K. The results are compared with those on Nd$_{0.45}$Sr$_{0.55}$MnO$_3$ which undergoes a transition to a homogeneous A-type antiferromagnetic phase at T$_N$ = 230 K and on La$_{0.77}$Ca$_{0.23}$MnO$_3$ which undergoes a transition to coexisting ferromagnetic metallic and ferromagnetic insulating phases. For x = 0.5, the EPR signals below T$_c$ consist of two Lorentzian components attributable to the coexistence of two phases. From the analysis of the temperature dependence of the resonant fields and intensities, we conclude that in the mixed phase ferromagnetic and A-type antiferromagnetic (AFM) phases coexist. The x = 0.55 compound shows a single Lorentzian throughout the temperature range. The signal persists for a few degrees below T_N. The behaviour of the A-type AFM phase is contrasted with that of the two ferromagnetic phases present in La$_{0.77}$Ca$_{0.23}$MnO$_3$. The comparison of behaviour of A-type AFM signal observed in both Nd$_{0.5}$Sr$_{0.5}$MnO$_3$and Nd$_{0.45}$Sr$_{0.55}$MnO$_3with the two FM phases of La$_{0.77}$Ca$_{0.23}$MnO$_3$, vis-a-vis the shift of resonances with respect to the paramagnetic phases and the behaviour of EPR intensity as a function of temperature conclusively prove that the Nd$_{0.5}$Sr$_{0.5}$MnO$_3$undergoes phase separation into A-type AFM and FM phases.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
