MAGNETIZATION MEASUREMENT AND MN-55 NMR-STUDY OF LA(NI1-XMGX)0.5MN0.5O3

Magnetization measurement and Mn-55 NMR study on a ferromagnet system La(Ni1+x2+Mgx2+)0.5Mn0.54+O3 are made. The divalent and the tetravalent ions are found to be ordered to a considerable extent in the whole compositional range, and the ferromagnetic superexchange interactions between neighboring Mn4+ and Ni2+ ions are estimated to be 26 K in magnitude. Mn-55 NMR signals are observed for samples with x less-than-or-equal-to 0.6 in a frequency range between 270 and 310 MHz. The spectra composed of several equidistantly separated peaks can be successfully interpreted as each peak being the signal from Mn" surrounded by a specific number of Ni2+ ions. The hyperfine magnetic field at Mn-55 supertransferred from a neighboring Ni2+ ion is determined to be 6.3 kOe, and the field originating from the own 3d magnetic moment of Mn4+ ion is estimated to be - 295 kOe, being a typical value for Mn4+ ions in oxides.