Spin orientation in solid solution hematite-ilmenite

Erik Brok, Cathrine Frandsen, Kim Lefmann, Suzanne A. McEnroe, Peter Robinson, Benjamin P. Burton, Thomas C. Hansen, Richard Harrison

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Abstract

The spin orientation in synthetic hematite-ilmenite samples and in a sample of natural hematite was studied from room temperature to above the antiferromagnetic-paramagnetic phase transition (the Néel temperature; TN ≈ 600–950 K) by neutron powder diffraction and at room temperature by Mössbauer spectroscopy. The usually assumed magnetic structure of hematite within this temperature range is antiferromagnetic with the spins confined to the basal plane of the hexagonal structure; however, an out-of-plane spin component is allowed by the symmetry of the system and has been observed in recent studies of synthetic hematite samples. We find the spins in the antiferromagnetic sublattices to be rotated out of the basal plane by an angle between 11(2)° and 22.7(5)° in both synthetic hematite-ilmenite samples and in the natural hematite sample. The spin angle remains tilted out of the basal plane in the entire temperature range below the Néel temperature and does not depend systematically on Ti-content. The results indicate that the out-of-plane spin component is an intrinsic feature of hematite itself, with an origin not yet fully understood, but consistent with group theory. This represents a major shift in understanding of one of the two main mineral systems responsible for rock magnetism.
Original languageEnglish
JournalAmerican Mineralogist
Volume102
Issue number6
Pages (from-to)1234-1243
Number of pages10
ISSN0003-004X
DOIs
Publication statusPublished - 2017

Bibliographical note

© 2017 Mineralogical Society of America

Keywords

  • Hematite
  • Magnetic properties
  • Spin orientation
  • Neutron scattering
  • Mössbauer spectroscopy

Cite this

Brok, E., Frandsen, C., Lefmann, K., McEnroe, S. A., Robinson, P., Burton, B. P., ... Harrison, R. (2017). Spin orientation in solid solution hematite-ilmenite. American Mineralogist, 102(6), 1234-1243. https://doi.org/10.2138/am-2017-5792CCBY
Brok, Erik ; Frandsen, Cathrine ; Lefmann, Kim ; McEnroe, Suzanne A. ; Robinson, Peter ; Burton, Benjamin P. ; Hansen, Thomas C. ; Harrison, Richard. / Spin orientation in solid solution hematite-ilmenite. In: American Mineralogist. 2017 ; Vol. 102, No. 6. pp. 1234-1243.
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title = "Spin orientation in solid solution hematite-ilmenite",
abstract = "The spin orientation in synthetic hematite-ilmenite samples and in a sample of natural hematite was studied from room temperature to above the antiferromagnetic-paramagnetic phase transition (the N{\'e}el temperature; TN ≈ 600–950 K) by neutron powder diffraction and at room temperature by M{\"o}ssbauer spectroscopy. The usually assumed magnetic structure of hematite within this temperature range is antiferromagnetic with the spins confined to the basal plane of the hexagonal structure; however, an out-of-plane spin component is allowed by the symmetry of the system and has been observed in recent studies of synthetic hematite samples. We find the spins in the antiferromagnetic sublattices to be rotated out of the basal plane by an angle between 11(2)° and 22.7(5)° in both synthetic hematite-ilmenite samples and in the natural hematite sample. The spin angle remains tilted out of the basal plane in the entire temperature range below the N{\'e}el temperature and does not depend systematically on Ti-content. The results indicate that the out-of-plane spin component is an intrinsic feature of hematite itself, with an origin not yet fully understood, but consistent with group theory. This represents a major shift in understanding of one of the two main mineral systems responsible for rock magnetism.",
keywords = "Hematite, Magnetic properties, Spin orientation, Neutron scattering, M{\"o}ssbauer spectroscopy",
author = "Erik Brok and Cathrine Frandsen and Kim Lefmann and McEnroe, {Suzanne A.} and Peter Robinson and Burton, {Benjamin P.} and Hansen, {Thomas C.} and Richard Harrison",
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Brok, E, Frandsen, C, Lefmann, K, McEnroe, SA, Robinson, P, Burton, BP, Hansen, TC & Harrison, R 2017, 'Spin orientation in solid solution hematite-ilmenite', American Mineralogist, vol. 102, no. 6, pp. 1234-1243. https://doi.org/10.2138/am-2017-5792CCBY

Spin orientation in solid solution hematite-ilmenite. / Brok, Erik; Frandsen, Cathrine; Lefmann, Kim; McEnroe, Suzanne A.; Robinson, Peter; Burton, Benjamin P.; Hansen, Thomas C.; Harrison, Richard.

In: American Mineralogist, Vol. 102, No. 6, 2017, p. 1234-1243.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Spin orientation in solid solution hematite-ilmenite

AU - Brok, Erik

AU - Frandsen, Cathrine

AU - Lefmann, Kim

AU - McEnroe, Suzanne A.

AU - Robinson, Peter

AU - Burton, Benjamin P.

AU - Hansen, Thomas C.

AU - Harrison, Richard

N1 - © 2017 Mineralogical Society of America

PY - 2017

Y1 - 2017

N2 - The spin orientation in synthetic hematite-ilmenite samples and in a sample of natural hematite was studied from room temperature to above the antiferromagnetic-paramagnetic phase transition (the Néel temperature; TN ≈ 600–950 K) by neutron powder diffraction and at room temperature by Mössbauer spectroscopy. The usually assumed magnetic structure of hematite within this temperature range is antiferromagnetic with the spins confined to the basal plane of the hexagonal structure; however, an out-of-plane spin component is allowed by the symmetry of the system and has been observed in recent studies of synthetic hematite samples. We find the spins in the antiferromagnetic sublattices to be rotated out of the basal plane by an angle between 11(2)° and 22.7(5)° in both synthetic hematite-ilmenite samples and in the natural hematite sample. The spin angle remains tilted out of the basal plane in the entire temperature range below the Néel temperature and does not depend systematically on Ti-content. The results indicate that the out-of-plane spin component is an intrinsic feature of hematite itself, with an origin not yet fully understood, but consistent with group theory. This represents a major shift in understanding of one of the two main mineral systems responsible for rock magnetism.

AB - The spin orientation in synthetic hematite-ilmenite samples and in a sample of natural hematite was studied from room temperature to above the antiferromagnetic-paramagnetic phase transition (the Néel temperature; TN ≈ 600–950 K) by neutron powder diffraction and at room temperature by Mössbauer spectroscopy. The usually assumed magnetic structure of hematite within this temperature range is antiferromagnetic with the spins confined to the basal plane of the hexagonal structure; however, an out-of-plane spin component is allowed by the symmetry of the system and has been observed in recent studies of synthetic hematite samples. We find the spins in the antiferromagnetic sublattices to be rotated out of the basal plane by an angle between 11(2)° and 22.7(5)° in both synthetic hematite-ilmenite samples and in the natural hematite sample. The spin angle remains tilted out of the basal plane in the entire temperature range below the Néel temperature and does not depend systematically on Ti-content. The results indicate that the out-of-plane spin component is an intrinsic feature of hematite itself, with an origin not yet fully understood, but consistent with group theory. This represents a major shift in understanding of one of the two main mineral systems responsible for rock magnetism.

KW - Hematite

KW - Magnetic properties

KW - Spin orientation

KW - Neutron scattering

KW - Mössbauer spectroscopy

U2 - 10.2138/am-2017-5792CCBY

DO - 10.2138/am-2017-5792CCBY

M3 - Journal article

VL - 102

SP - 1234

EP - 1243

JO - American Mineralogist

JF - American Mineralogist

SN - 0003-004X

IS - 6

ER -

Brok E, Frandsen C, Lefmann K, McEnroe SA, Robinson P, Burton BP et al. Spin orientation in solid solution hematite-ilmenite. American Mineralogist. 2017;102(6):1234-1243. https://doi.org/10.2138/am-2017-5792CCBY