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LiHoF4 : cuboidal demagnetizing factor in an Ising ferromagnet
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Twengström, M., Bovo, L., Petrenko, Oleg, Bramwell, S. T. and Henelius, P. (2020) LiHoF4 : cuboidal demagnetizing factor in an Ising ferromagnet. Physical Review B, 102 (14). 144426. doi:10.1103/PhysRevB.102.144426 ISSN 2469-9950.
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WRAP-LiHoF4-cuboidal-demagnetizing-factor-Ising-ferromagnet-Petrenko-2020.pdf - Published Version - Requires a PDF viewer. Available under License Creative Commons Attribution 4.0. Download (777Kb) | Preview |
Official URL: http://dx.doi.org/10.1103/PhysRevB.102.144426
Abstract
The demagnetizing factor can have an important effect on physical properties, yet its role in determining the behavior of nonellipsoidal samples remains to be fully explored. We present a detailed study of the role of spin symmetry in determining the demagnetizing factor of cuboids, focusing, as a model example, on the Ising dipolar ferromagnet LiHoF4. We distinguish two different functions: the demagnetizing factor as a function of intrinsic susceptibility N(χ) and the demagnetizing factor as a function of temperature N(T ). For a given nonellipsoidal sample, the function N(χ) depends only on dipolar terms in the spin Hamiltonian, but apart from in the limits χ → 0 and χ →∞, it is a different function for different spin symmetries. The function N(T ) is less universal, depending on exchange terms and other details of the spin Hamiltonian. We apply a recent theory to calculate these functions for spherical and cuboidal samples of LiHoF4. The theoretical results are compared with N(χ) and N(T ) derived from experimental measurements of the magnetic susceptibility of corresponding samples of LiHoF4, both above and below its ferromagnetic transition at Tc = 1.53 K. Close agreement between theory and experiment is demonstrated, showing that the intrinsic susceptibility of LiHoF4 and other strongly magnetic systems can be accurately estimated from measurements on cuboidal samples. Our results further show that for cuboids, and implicitly for any sample shape, N(χ) below the ordering transition takes the value N(∞). This confirms and extends the scope of earlier observations that the intrinsic susceptibility of ferromagnets remains divergent below the transition, in contradiction to the implications of broken symmetry. We discuss the topological and microscopic origins of this result.
Item Type: | Journal Article | ||||||||||||
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Subjects: | Q Science > QC Physics | ||||||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||||||
Library of Congress Subject Headings (LCSH): | Ising model, Antiferromagnetism , Spin waves | ||||||||||||
Journal or Publication Title: | Physical Review B | ||||||||||||
Publisher: | American Physical Society | ||||||||||||
ISSN: | 2469-9950 | ||||||||||||
Official Date: | 19 October 2020 | ||||||||||||
Dates: |
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Volume: | 102 | ||||||||||||
Number: | 14 | ||||||||||||
Article Number: | 144426 | ||||||||||||
DOI: | 10.1103/PhysRevB.102.144426 | ||||||||||||
Status: | Peer Reviewed | ||||||||||||
Publication Status: | Published | ||||||||||||
Access rights to Published version: | Open Access (Creative Commons) | ||||||||||||
Copyright Holders: | The Authors | ||||||||||||
Date of first compliant deposit: | 21 December 2020 | ||||||||||||
Date of first compliant Open Access: | 22 December 2020 | ||||||||||||
RIOXX Funder/Project Grant: |
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