Magnetic resonance of type-I fcc antiferromagnets

Marko Heinilä, Aarne Oja

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

We calculate magnetic-resonance absorption curves for an assembly of classical spins located in an fcc lattice with spin-spin interactions which stabilize antiferromagnetic order of the first kind. The only source of anisotropy in the model is the dipole-dipole interaction which, at equilibrium, confines the ordered moments into planes perpendicular to the respective type-I ordering vectors. Our principal tool of analysis combines numerical integration of the equations of motion with Monte Carlo simulations. Complete absorption line shapes for classical spins can be calculated using this technique. Spin dynamics is investigated as well by extending our earlier mean-field analysis, the results of which are compared with the simulations. Special attention is paid to a sum rule that relates the intensities of the resonance peaks to the static susceptibility. To this end, we calculate the static susceptibility matrixes for certain single-k and triple-k type-I structures. We investigate, in particular, examples of cases where thermal fluctuations beyond the mean-field theory shift resonance lines from zero frequency to a finite value. It is demonstrated that this effect is related to the so-called ‘‘ordering-by-disorder’’ mechanism in which fluctuations stabilize a unique ground state in a continuously degenerate manifold. Our results explain several features observed in recent NMR studies of antiferromagnetic nuclear-spin ordering in copper and silver at nanokelvin temperatures. Analogies with spin dynamics in solid 3He and superfluid 3A are briefly discussed.
Original languageEnglish
Pages (from-to)9275-9287
Number of pages13
JournalPhysical Review B: Condensed Matter and Materials Physics
Volume54
Issue number13
DOIs
Publication statusPublished - 1996
MoE publication typeA1 Journal article-refereed

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Spin dynamics
Magnetic resonance
magnetic resonance
Mean field theory
spin dynamics
Silver
Ground state
Equations of motion
Copper
Anisotropy
Nuclear magnetic resonance
dipoles
magnetic permeability
numerical integration
resonance lines
nuclear spin
sum rules
line shape
equations of motion
simulation

Cite this

Heinilä, Marko ; Oja, Aarne. / Magnetic resonance of type-I fcc antiferromagnets. In: Physical Review B: Condensed Matter and Materials Physics. 1996 ; Vol. 54, No. 13. pp. 9275-9287.
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abstract = "We calculate magnetic-resonance absorption curves for an assembly of classical spins located in an fcc lattice with spin-spin interactions which stabilize antiferromagnetic order of the first kind. The only source of anisotropy in the model is the dipole-dipole interaction which, at equilibrium, confines the ordered moments into planes perpendicular to the respective type-I ordering vectors. Our principal tool of analysis combines numerical integration of the equations of motion with Monte Carlo simulations. Complete absorption line shapes for classical spins can be calculated using this technique. Spin dynamics is investigated as well by extending our earlier mean-field analysis, the results of which are compared with the simulations. Special attention is paid to a sum rule that relates the intensities of the resonance peaks to the static susceptibility. To this end, we calculate the static susceptibility matrixes for certain single-k and triple-k type-I structures. We investigate, in particular, examples of cases where thermal fluctuations beyond the mean-field theory shift resonance lines from zero frequency to a finite value. It is demonstrated that this effect is related to the so-called ‘‘ordering-by-disorder’’ mechanism in which fluctuations stabilize a unique ground state in a continuously degenerate manifold. Our results explain several features observed in recent NMR studies of antiferromagnetic nuclear-spin ordering in copper and silver at nanokelvin temperatures. Analogies with spin dynamics in solid 3He and superfluid 3A are briefly discussed.",
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Magnetic resonance of type-I fcc antiferromagnets. / Heinilä, Marko; Oja, Aarne.

In: Physical Review B: Condensed Matter and Materials Physics, Vol. 54, No. 13, 1996, p. 9275-9287.

Research output: Contribution to journalArticleScientificpeer-review

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AU - Heinilä, Marko

AU - Oja, Aarne

PY - 1996

Y1 - 1996

N2 - We calculate magnetic-resonance absorption curves for an assembly of classical spins located in an fcc lattice with spin-spin interactions which stabilize antiferromagnetic order of the first kind. The only source of anisotropy in the model is the dipole-dipole interaction which, at equilibrium, confines the ordered moments into planes perpendicular to the respective type-I ordering vectors. Our principal tool of analysis combines numerical integration of the equations of motion with Monte Carlo simulations. Complete absorption line shapes for classical spins can be calculated using this technique. Spin dynamics is investigated as well by extending our earlier mean-field analysis, the results of which are compared with the simulations. Special attention is paid to a sum rule that relates the intensities of the resonance peaks to the static susceptibility. To this end, we calculate the static susceptibility matrixes for certain single-k and triple-k type-I structures. We investigate, in particular, examples of cases where thermal fluctuations beyond the mean-field theory shift resonance lines from zero frequency to a finite value. It is demonstrated that this effect is related to the so-called ‘‘ordering-by-disorder’’ mechanism in which fluctuations stabilize a unique ground state in a continuously degenerate manifold. Our results explain several features observed in recent NMR studies of antiferromagnetic nuclear-spin ordering in copper and silver at nanokelvin temperatures. Analogies with spin dynamics in solid 3He and superfluid 3A are briefly discussed.

AB - We calculate magnetic-resonance absorption curves for an assembly of classical spins located in an fcc lattice with spin-spin interactions which stabilize antiferromagnetic order of the first kind. The only source of anisotropy in the model is the dipole-dipole interaction which, at equilibrium, confines the ordered moments into planes perpendicular to the respective type-I ordering vectors. Our principal tool of analysis combines numerical integration of the equations of motion with Monte Carlo simulations. Complete absorption line shapes for classical spins can be calculated using this technique. Spin dynamics is investigated as well by extending our earlier mean-field analysis, the results of which are compared with the simulations. Special attention is paid to a sum rule that relates the intensities of the resonance peaks to the static susceptibility. To this end, we calculate the static susceptibility matrixes for certain single-k and triple-k type-I structures. We investigate, in particular, examples of cases where thermal fluctuations beyond the mean-field theory shift resonance lines from zero frequency to a finite value. It is demonstrated that this effect is related to the so-called ‘‘ordering-by-disorder’’ mechanism in which fluctuations stabilize a unique ground state in a continuously degenerate manifold. Our results explain several features observed in recent NMR studies of antiferromagnetic nuclear-spin ordering in copper and silver at nanokelvin temperatures. Analogies with spin dynamics in solid 3He and superfluid 3A are briefly discussed.

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