We have studied the magnetic and magnetotransport properties of the perovskites La8Sr0.2Mn8Ni0.2O3 and La0.7Sr0.3Mn0.8Ni0.2O3. Ferromagnetic cluster behaviors have been observed. The most interesting feature is that the cluster-glass state exhibits both macroscopic insulator-like transport behavior and largely enhanced magnetoresistance (MR) at low temperature. Such a low-temperature MR is weakly temperature dependent. In particular, a low-temperature magnetoresistance ratio (Δρ/ρ0) as high as 60% has been found in La0.7Sr0.3Mn0.8Ni0.2O3. We attribute the low-temperature magnetotransport to the spin-dependent scattering inside the grains.

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With the aim to stabilize reduced CGO molecules of solid hlleride as free anion radicals in solution, Na,C60 (x=l, 10) was dissolved in DMSO. The NaXC6o was chosen among the other alkali-metal hllerides due to the possibility to increase a number of intercalated Na atoms in a f.c.c. lattice of c60. A sufficiently high concentration of c 6 0 anion radicals of an order of magnitude larger than that usually achieved in solution by an electrochemical reduction was obtained. The sharp resonances with the linewidths of order of 0.1 G and with g=2.0004(6) -2.0012(8) of the room temperature ESR spectra of fluid solution were assigned from mono-to pentaanions of C60. An appearance of additional sharp peaks at g=2.0016-2.0019 in the spectra of solution of nominal NaloC60, but NalC60, tentatively related to C6On-with n>6. The results of this study showed a simple approach in an accomplishment of highly concentrated solutions of free anion radicals c60n-, as well as in stabilization of the anion radicals with increased n. In this way a homogeneity of alkali metal intercalation and characteristics of the solvent will be important.

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