Neutron diffraction and Mossbauer studies of the La0.67Ba0.33Mn0.9957Fe0.01O3

The perovskite La_0.67Ba_0.33Mn_0.99⁵⁷Fe_0.01O₃ compound was prepared by wet chemical solution process at 1200°C for 3 h. Magnetic properties of La_0.67Ba_0.33Mn_0.99⁵⁷Fe_0.01O₃ were studied using X-ray diffraction, Rutherford backscattering spectroscopy (RBS), neutron diffraction, Mossbauer spectroscopy, vibrating sample magnetometry, and magnetoresistance measurements. The polycrystalline La_0.67Ba_0.33Mn_0.99⁵⁷Fe_0.01O₃ had a space group Pnma of orthorhombic perovskite structure with lattice constants a₀=5.526 Å, b₀=7.830 Å, and c₀=5.540 Å, respectively. A chemical composition was confirmed to be stoichiometric by RBS. The maximum magnetoresistance ratio (Δρ/ρ(0)) was observed at 281 K, with a magnitude of 9.5% in 1 Tesla. The Curie temperature (T_C) was determined to be 345 K. Mossbauer spectra of La_0.67Ba_0.33Mn_0.99⁵⁷Fe_0.01O₃ were taken at various temperatures ranging from 15 to 400 K. Below 77 K, two magnetic phases were increased and showed two sharp sextets of spectra. The magnetic hyperfine fields of outer (51%) and inner (49%) subspectrum were H_hf=530 and 480 kOe, respectively. These unusual phenomena provide direct evidence of the two-magnetic phase character of the metallic state in the mixed valence of La_0.67Ba_0.33Mn_0.99⁵⁷Fe_0.01O₃ powder. The outer sextet of Mossbauer spectra rapidly collapsed to paramagnetic phase with increasing temperature.