Effect of Thermal Treatments on Magnetic Properties of Some Magnetite Samples Investigated by 57Fe Mössbauer Spectroscopy

Abstract

57Fe Mössbauer spectroscopy is one of the most powerful tools that used in studying magnetic properties of materials. This work aims to investigate the magnetic properties of MgxSrxMnxCo1-3xFe2O4 (x = 0, 0.1, 0.2, 0.3 and 0.33) nanoparticles annealed at 500 ˚C. The aim extends to study the magnetic properties of BaFe2O4 sample as a function of different measuring temperatures. The results showed that magnetic hyperfine fields of the annealed samples were larger compared to as-prepared samples which agrees with literature. This reflects the effect of particle sizes on relaxation time τ as explained by Néel theory. The values of isomer shift were in the range of 0.30 to 0.51 mm/s. This indicates presence of Fe3+ ions in the samples. The line widths decreased in annealed samples compared to as-prepared ones. Investigation the magnetic properties of BaFe2O4 sample as a function of different measuring temperatures of 77, 80, 90, 160, 200, 250 and 300 K revealed that increasing of measuring temperature changed the ferrimagnetic order of the sample to paramagnetic state. Isomer shift values were in the range of 0.30 to 0.45 mm/s, which related to Fe3+ ions. Line width values show no significant trends with increasing measuring temperatures. The results showed that temperature (annealing or measuring) has significant influence upon hyperfine parameters therefore; it can decide the magnetic state of a material.