Magnetization Measurement and⁵⁵Mn NMR Study of La(Ni1-xMgx)0.5Mn0.5O₃

Magnetization measurement and 55 Mn NMR study on a ferromagnet system La(Ni 2+ 1- x Mg x 2+ ) 0.5 Mn 0.5 4+ O 3 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 Mn 4+ and Ni 2+ ions are estimated to be 26 K in magnitude. 55 Mn NMR signals are observed for samples with x ≤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 4+ surrounded by a specific number of Ni 2+ ions. The hyperfine magnetic field at 55 Mn supertransferred from a neighboring Ni 2+ ion is determined to be 6.3 kOe, and the field originating from the own 3d magnetic moment of Mn 4+ ion is estimated to be -295 kOe, being a typical value for Mn 4+ ions in oxides.