Structural and magnetic properties of MnxCo1−xFe2O4 ferrite nanoparticles

We report on the structural and magnetic properties of nanoparticles of MnxCo1−xFe2O4 (x=0.1, 0.5) ferrites produced by the glycothermal reaction. From the analysis of XRD spectra and TEM micrographs, particle sizes of the samples have been found to be about 8 nm (for x=0.1) and 13 nm (for x=0.5). The samples were characterized by DC magnetization in the temperature range 5–380 K and in magnetic fields of up to 40 kOe using a SQUID magnetometer. Mössbauer spectroscopy results show that the sample with higher Mn content has enhanced hyperfine fields after thermal annealing at 700 °C. There is a corresponding small reduction in hyperfine fields for the sample with lower Mn content. The variations of saturation magnetization, remnant magnetization and coercive fields as functions of temperature are also presented. Our results show evidence of superparamagnetic behaviour associated with the nanosized particles. Particle sizes appear to be critical in explaining the observed properties.

Research Highlights
► We have successfully made MnxCo1–xFe2O4 nanosized compounds by glycothermal reaction as confirmed by XRD and TEM measurements.
► Slight reduction in hyperfine fields due to annealing is also obtained in the Mn0.1Co0.90Fe2O4 sample.
► Spin glass-like behaviour has been observed at low temperature in the two Mn substituted samples.
► From the FC and ZFC measurements the state of magnetization appears to be higher in the Mn0.5Co0.5Fe2O4 sample. The spin freezing at low temperature also appears to be stronger.
► Our results also show evidence for superparamagnetic behaviour of the samples investigated.