UNUSUAL TEMPERATURE DEPENDENCE OF COERCIVITY IN ε-Fe2O3 PHASE

Nano iron oxides have been intensively investigated due to their various potential biomedical applications. epsilon-Fe2O3 phase exerted internal coercivity value up to similar to 20 kOe, high Curie temperature (T-c= 510 K), and magnetoelectric character. Accordingly, epsilon phase is recognized as a suitable material for medical spintronic biosensors production, that present important part for the lab-on-a-chip systems. Noteworthy, epsilon-Fe2O3 phase exerts peculiar magnetic behavior. To get better insight into the magnetism of this material, epsilon-Fe2O3/SiO2 sample was prepared by the combination of the sol-gel synthesis and microemulsion method (T-ann=1050 degrees C, t(ann)=4h). Afterwards, the sample was exposed to post-annealing treatment at 100 degrees C and 200 degrees C. Synthesized material was preliminary examined by XRD and SQUID techniques. Coercivity changes, induced by the post-annealing temperature oscillations, were monitored by hysteretic measurements. Sample annealed at 1050 degrees C for 4h, showed coercivity similar to 20 kOe. The same sample performed to the post-annealing treatment at 100 degrees C, exerted significantly decreased coercivity (similar to 1600 Oe). Further rise of the post-annealing temperature (200 degrees C) resulted in the increased coercivity similar to 15 kOe. Obtained study showed that there is insufficient knowledge concerning the epsilon-Fe2O3 coercivity changes of the polymorph. The more detailed investigation will be conducted, in order to advance the control of the epsilon phase magnetic properties.