Local structure and magnetic inhomogeneity of nano-sized La0.7Sr0.3MnO3 manganites.

We present the study of the local structure and magnetic inhomogeneity of nano-sized La0.7Sr0.3MnO3 manganites performed by x-ray absorption fine structure (XAFS) spectroscopy and nuclear magnetic resonance (NMR). Nano-powders with particle size of 50-200 nm (NP1) and 20 nm (NP2), and bulk samples (BS) were studied. EXAFS data show the difference between the local structure of core and outer shell of the nano-particle. The data evidenced that the shell of particles presents the disordered crystalline array. According to the NMR, at low temperature the magnetic state of NP1 sample is homogenous. However, with increase of temperature the two ferromagnetic phases, with strong and weakened double exchange, coexist. The NP2 powder is magnetically homogeneous and characterized by weakened double exchange at all temperatures of the existence of the magneto-ordered state. The results specify on possible existence of characteristic spatial scale below which the phase stratification becomes energetically unfavorable. [ABSTRACT FROM AUTHOR]