NMR (55Mn, 139La) and Mossbauer spectroscopy (119Sn) studies of (La0.67Ca0.33)(Mn1-xSnx)O3-δ compounds

A Sn-119 Mossbauer spectroscopy and zero field Mn-55 and La-139 NMR studies of (La0.67Ca0.33)(Mn1-x Sn-x)O3-delta (x = 0, 0.01, 0.03, and delta approximate to 0.06) were reported. The temperature evolution of the Sn hyperfine field (B-hf) for x = 0.03 determined from the Mossbauer spectroscopy measurements was analysed within a molecular field model. A fit to the temperature dependence of B-hf(max) provided the Curie temperature T*(C) = 160(3) K, which is h in good agreement with T-c obtained from dc magnetisation measurements. The 55Mn NMR spectra for x = 0 and 0.01 show a single double exchange Mn 3(+)/4(+) resonance line and exhibit strong Suhl-Nakamura relaxation effects characteristic of the ferromagnetic metallic phase. The spectra for x = 0.03 show a coexistence of the double exchange line with the lines characteristic of Mn (3+) and Mn (4+) valence states. This shows that a 3% Sn doping strongly suppresses the double exchange interaction and leads to microscopic. phase segregation into ferromagnetic metal and ferromagnetic insulator.