ACTA

NMR (⁵⁵Mn, ¹³⁹La) and Mössbauer Spectroscopy (¹¹⁹Sn) Studies of (La_0.67Ca_0.33)(Mn_1-xSn_x)O_3-δ Compounds

J. Przewoźnik
Department of Solid State Physics, Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Cracow, Poland

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A ¹¹⁹Sn Mössbauer spectroscopy and zero field ⁵⁵Mn and ¹³⁹La NMR studies of (La_0.67Ca_0.33)(Mn_1-xSn_x)O_3-δ (x=0, 0.01, 0.03, andδ≈0.06) were reported. The temperature evolution of the Sn hyperfine field (B_hf) for x=0.03 determined from the Mössbauer 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 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 Mn³⁺ and Mn⁴⁺ 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.

DOI: 10.12693/APhysPolA.111.649
PACS numbers: 76.60.-k, 76.80.+y, 75.47.Lx, 77.80.Bh, 75.47.Gk