Crystallographic and Mossbauer studies of Li0.5Fe2.5O4 prepared by high temperature thermal decomposition and sol-gel methods

Li0.5Fe2.5O4 powders were prepared by high temperature thermal decomposition (HTTD) and sol-gel methods. The sample prepared by HTTD method (SA) has space group of Fd3m. The samples annealed at 700 degrees C (SB) and quenched at 1000 degrees C (SC) prepared by sol-gel method have space groups of P4(3)32 and Fd3m, respectively. The saturation magnetizations (M-s) for the sample prepared by HTTD method (SA) at room temperature is 55 emu/g and those for the samples annealed at 700 degrees C (SB) and quenched at 1000 degrees C (SC) prepared by sol-gel method are 59 and 62 emu/g, respectively. In contrast, the coercivity (H-c) values of the each sample are 4.1, 93.7, and 9.1 Oe, respectively. Mossbauer spectra of each sample have been obtained from 4.2 to 700 K. The valence state of Fe ions for the tetrahedral (A) and octahedral (B) sites is Fe3+. Mossbauer spectrum of the sample prepared by HTTD method shows superparamagnetic behavior at room temperature, while in case of sol-gel method, Mossbauer spectra show ferrimagnetic state of six line having the hyperfine field (H-f) values of 518 kOe for the A sites and 536 kOe for the B sites. (c) 2007 American Institute of Physics.