Domain orbital state in ferromagnetic insulating La₀.₈₂₅Ca₀.₁₇₅Mn₀.₉₉⁵⁷Fe₀.₀₁O₃ compound

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Using Mössbauer and EPR spectroscopy we have studied the insulating ferromagnetic La₁₋ₓCaₓMn₀.₉₉⁵⁷Fe₀.₀₁O₃ (x=0.175) compound prepared in air and reduced atmosphere. The average hyperfine field follows a mean field approximation solution in contrast with the ferromagnetic metallic regime where it significantly deviates from the order parameter deduced from neutron diffraction data or mean field approximation. Although the magnetic measurements show remarkable differences between air prepared and reduced R samples the corresponding Mössbauer spectra are almost identical. The strong temperature dependance of the hyperfine field distribution at the ⁵⁷Fe nucleus is related with the supertransferred magnetic field between ferric ion and the oxygen bridged six nearest-neighbor manganese ions. The sudden increasing of the width of the hyperfine field distribution above TB≈ 100 K has been attributed to the orbital disordering occurring for T>TB.