Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.13/931615

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Title
Spin orientation in a natural Ti-bearing hematite: evidence for an out-of-plane component
Author/Creator
Harrison, Richard J.;  McEnroe, Suzanne A.;  Robinson, Peter;  Howard, Christopher J.
Institution
The University of Newcastle. Faculty of Engineering & Built Environment, School of Engineering
Description
The orientation of spins in a natural sample of Ti-bearing hematite (Fe₂O₃) has been measured from 2–300 K using time-of-flight neutron powder diffraction. It is shown that the antiferromagnetic alignment vector is tilted out of the basal plane by an average angle of 30°, independent of temperature, contrary to the normal expectation that all spins lie in the basal plane due to the suppression of the Morin transition by Ti. This unusual result is related to the non-uniform spatial distribution of Ti in this sample, which takes the form of ~1 nm exsolution lamellae of ilmenite (FeTiO₃), observed using transmission electron microscopy. It is suggested that the exsolution lamellae lead to a localization of Fe²⁺ species within the lamellar interfaces, which cause tilting of some spins toward the crystallographic c axis. The presence of an out-of-plane component of spin at room temperature reconciles experimental and computational attempts to explain the phenomenon of “giant exchange bias” that appears when this sample is zero-field cooled below the ilmenite Néel temperature.
Relation
American Mineralogist Vol. 95, Issue 7, p. 974-979
Publisher Link
http://dx.doi.org/10.2138/am.2010.3402
Date
2010
Publisher
Mineralogical Society of America
Keyword(s)
Hematite;  magnetic properties;  spin orientation;  Morin transition;  exchange bias
Resource Type
journal article
Identifier
http://hdl.handle.net/1959.13/931615
Identifier
ISSN:0003-004X
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Subject
"American Mineralogist"
 
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