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arXiv · 1909.05763

Temperature and field evolution of site-dependent magnetism in $ε$-Fe$_2$O$_3$ nanoparticles

Richard Jones·Rachel Nickel·Palash K. Manna·J. Hilman·Johan van Lierop
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Abstract

8~nm epsilon-Fe2O3 nanoparticles exhibit a spin reorientation transition that begins at 150 K which is a hallmark of this unique iron-oxide polymorph. We find that the change from the high to low temperature magnetic structures has been suppressed by ~50 K. At the spin reorientation temperature, a change of the field-dependent response of the tetrahedral sites in intermediate field strengths (0.25 - 1.5 T) indicates that a collective tetrahedral distortion occurs to which the octahedral sites adjust, altering the magnetic anisotropy. An abrupt step in the hyperfine parameters' temperature dependencies, especially at 125 K for the hyperfine field associated with the Fe4 tetrahedral sites, suggests strongly a change in the superexchange pathways are responsible for the spin reorientation.

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Richard Jones, Rachel Nickel, Palash K. Manna, J. Hilman, Johan van Lierop. 2019-09-12. Temperature and field evolution of site-dependent magnetism in $ε$-Fe$_2$O$_3$ nanoparticles. https://doi.org/10.1103/physrevb.100.094425

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