Abstract
We report shape- and field-dependent magnetic properties of ellipsoid-, spindle-, flattened- and rhombohedra-shaped α-Fe 2O 3 samples prepared by solvothermal technique. We observed that a magnetic spin-flip mechanism, mostly known as Morin transition ( T M), depends on the shape of α-Fe 2O 3 as well as on the applied magnetic field. In each of these structures the obtained value of T M was less than its bulk value of 263 K. We observed that T M shifted from highest 251.4 K for ellipsoid to lowest 220.8 K for rhombohedra structure, with intermediate values of T M for the other two structures. However, for rhombohedra structure T M shifted from 220.8 to 177.5 K under the external magnetic field of 100 Oe–30 kOe, respectively. The observed lowering of T M in the structured sample was analyzed in terms of elementary size, shape of the nanocrystallites, lattice parameters and occupancy of Fe +3 ions as well. These parameters were determined from the Rietveld refinement process using MAUD software.
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