Neutron diffraction and neutron depolarization study of perovskite La0.7-xYxCa0.3Mn0.97Fe0.03O3 (x = 0.07 and 0.12)

Perovskite manganites of type AMnO3 have recently attracted much attention because of their unusual physical properties and technological applications. Depending upon the type of A cation, these manganites exhibits a range of interesting properties including colossal magnetoresistance, charge-ordering, magnetic-field induced structural transitions. Here we report the structural and magnetic properties of perovskite La0.7-xYxCa0.3Mn0.97Fe0.03O3 (x = 0.07 and 0.12). Polycrystalline samples were prepared by using the conventional solid-state reaction method. The Rietveld analysis of neutron diffraction pattern at 300 K, confirms the single-phase formation of this compound in the orthorhombic crystal structure under the space group Pnma (Space Group No. 62). The refined lattice parameters are a = 5.483 (9), b = 7.744 (6), c = 5.485 (4) Å, for x = 0.07 and α = β = γ = 90°. Mössbauer study shows that the Fe ions are in high spin +3 state at room temperature. The magnetization study shows a ferromagnetic ordering with Curie temperature (TC) of 111 K and 79 K for x = 0.07 and 0.12, respectively. An enhancement in the intensity of the fundamental (nuclear) Bragg peak has been observed below TC. The observed magnetic Bragg peaks have been indexed using the propagation vector k = (0, 0, 0). The magnetic structure is shown. In the magnetic structure, moments are aligned along the crystallographic b direction. The refined value of the magnetic moment at 4b site is 3.19(1)μB per Mn/Fe. Neutron depolarization study at an applied field of 50 Oe for x = 0.07, and 0.12 samples show a decrease in the ferromagnetic (FM) clusters size with increasing Y concentration. (author)