Mössbauer study of iron ordering in mixed valence system LuFe ₂O₄

Single crystalline LuFe₂O₄ was grown by the floating zone method. The crystallographic and magnetic properties of the sample were measured using x-ray diffractometer (XRD), Mössbauer spectroscopy, and vibrating sample magnetometer (VSM). The crystal structure was found to be a two-dimensional layeredtype rhombohedral with space group R3-mh. The magnetic Curie temperature (T_C) was determined to be 250 K from the M-T curve and Mössbauer spectra. Just below T_C, the magnetic moment has large value and shows a abrupt change in M-T curve. The Mössbauer spectra have been taken at various temperatures ranging from 4.2 to 370 K. We confirmed that the charge ordering of Fe³⁺ and Fe²⁺ ions was begun below 350 K, magnetic superstructure of the different ionic state was formed around 320 K. The isomer shift value of Fe²⁺ doublet increases with decreasing temperature from 320 to 235 K. At low temperature, Mössbauer spectra consisted of four sextets with magnetic ordering.