I have annealed hematite using bothe air and vacuum atmosphere, am not able to understand how this atmosphere affecting magnetic and electrical parameters in hematite system.
Is the hematite in (nano)powder, thin film, or single crystal form? What specific changes in electrical and magnetic properties do you see?
Annealing hematite in vacuum would probably reduce some fraction of your sample to magnetite, which is more conductive and magnetic than hematite.
dear sir,
Thank you. it is nano powder and Also it is metal (Ga) doped hematite. both vacuum and air samples show rhombohedral structure. i did not observe any structural changes till (low temperature )15K. i have observed the increase of magnetic moment in vacuum annealed sample than air-annealed sample. also the coercivity less in vacuum annealed samples.
(frequency dependent) conductivity order is (2 order) is more in vacuum samples. i am not able to understand conduction mechanism (hopping) in these (rhombohedral) structures. I-V studies show more magnitude of current in vacuum annealed samples.
I suppose annealing in vacuum may introduce Fe2+ in hematite, stabilized by O vacancies or some other local/surface transformation. The addition of Fe2+ would increase the electrical conductivity by small polaron hopping, since there will be more excess electrons (up to a point). The papers linked here may help clarify the conduction phenomenon.
http://pubs.acs.org/doi/abs/10.1021/cm504451j
http://scitation.aip.org/content/aip/journal/jcp/122/14/10.1063/1.1869492
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