Structural phase analysis, optical and magnetic properties of nano Mn-doped LiFe₅O₈

Nano Mn-doped LiFe₅O₈ was synthesized by citrate procedure. Structural and microstructure investigations have been performed applying X-ray diffraction (XRD), neutron powder diffraction (NPD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscope (TEM). Field-cooled (FC) and zero field-cooled (ZFC) dc magnetization were measured using a SQUID magnetometer. Law of Approach to saturation model was applied on hysteresis loops measured by vibrating sample magnetometer (VSM) at room temperature to obtain the saturation magnetization and magneto anisotropy constant for all samples. Rietveld analysis of XRD and NPD revealed that LiFe₅O₈ has ordered cubic structure with space group P4₃32. On the other hand XRD and FTIR analyses revealed that Mn-doped LiFe₅O₈ system has biphasic structures; cubic with ordered phase (P4₃32) and disordered one (Fd$\overline{3}$m). TEM image shown that the sample has an average particle size ~ 14 nm. Applying a propagation vector k=(0 0 0), all magnetic peaks of NPD data at 4 K are indexed with total magnetic moment = 1.8 μB. The coercivity and saturation magnetization reduced generally with raising the amount of Mn doping. Photoluminescence spectra of all samples exhibited two UV and one green sub-emissions.