A study of the quantum classical crossover in the spin dynamics of the 2D S=5/2 antiferromagnet Rb2MnF4: neutron scattering, computer simulations, and analytic theories
We report comprehensive inelastic neutron scattering measurements of the magnetic excitations in the 2D spin-5/2 Heisenberg antiferromagnet Rb2MnF4 as a function of temperature from deep in the Neel ordered phase up to paramagnetic, 0.13 < kBT/4JS < 1.4. Well defined spin-waves are fou...
| Main Authors: | , , , , |
|---|---|
| Format: | Journal article |
| Language: | English |
| Published: |
2008
|
| _version_ | 1797073927898398720 |
|---|---|
| author | Huberman, T Tennant, D Cowley, R Coldea, R Frost, C |
| author_facet | Huberman, T Tennant, D Cowley, R Coldea, R Frost, C |
| author_sort | Huberman, T |
| collection | OXFORD |
| description | We report comprehensive inelastic neutron scattering measurements of the magnetic excitations in the 2D spin-5/2 Heisenberg antiferromagnet Rb2MnF4 as a function of temperature from deep in the Neel ordered phase up to paramagnetic, 0.13 < kBT/4JS < 1.4. Well defined spin-waves are found for wave-vectors larger than the inverse correlation length $\eta^{-1}$ for temperatures up to near the Curie-Weiss temperature, $\Theta_{CW}$. For wave-vectors smaller than $\eta^{-1}$, relaxational dynamics occurs. The observed renormalization of spin-wave energies, and evolution of excitation line-shapes, with increasing temperature are quantitatively compared with finite-temperature spin-wave theory, and computer simulations for classical spins. Random phase approximation calculations provide a good description of the low-temperature renormalisation of spin-waves. In contrast, lifetime broadening calculated using the first Born approximation shows, at best, modest agreement around the zone boundary at low temperatures. Classical dynamics simulations using an appropriate quantum-classical correspondence were found to provide a good description of the intermediate- and high-temperature regimes over all wave-vector and energy scales, and the crossover from quantum to classical dynamics observed around $\Theta_{CW}/S$, where the spin S=5/2. A characterisation of the data over the whole wave-vector/energy/temperature parameter space is given. In this, $T^2$ behaviour is found to dominate the wave-vector and temperature dependence of the line widths over a large parameter range, and no evidence of hydrodynamic behaviour or dynamical scaling behaviour found within the accuracy of the data sets. |
| first_indexed | 2024-03-06T23:28:56Z |
| format | Journal article |
| id | oxford-uuid:6b5c10ba-938a-4785-b1ce-9177933d259a |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T23:28:56Z |
| publishDate | 2008 |
| record_format | dspace |
| spelling | oxford-uuid:6b5c10ba-938a-4785-b1ce-9177933d259a2022-03-26T19:03:28ZA study of the quantum classical crossover in the spin dynamics of the 2D S=5/2 antiferromagnet Rb2MnF4: neutron scattering, computer simulations, and analytic theoriesJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:6b5c10ba-938a-4785-b1ce-9177933d259aEnglishSymplectic Elements at Oxford2008Huberman, TTennant, DCowley, RColdea, RFrost, CWe report comprehensive inelastic neutron scattering measurements of the magnetic excitations in the 2D spin-5/2 Heisenberg antiferromagnet Rb2MnF4 as a function of temperature from deep in the Neel ordered phase up to paramagnetic, 0.13 < kBT/4JS < 1.4. Well defined spin-waves are found for wave-vectors larger than the inverse correlation length $\eta^{-1}$ for temperatures up to near the Curie-Weiss temperature, $\Theta_{CW}$. For wave-vectors smaller than $\eta^{-1}$, relaxational dynamics occurs. The observed renormalization of spin-wave energies, and evolution of excitation line-shapes, with increasing temperature are quantitatively compared with finite-temperature spin-wave theory, and computer simulations for classical spins. Random phase approximation calculations provide a good description of the low-temperature renormalisation of spin-waves. In contrast, lifetime broadening calculated using the first Born approximation shows, at best, modest agreement around the zone boundary at low temperatures. Classical dynamics simulations using an appropriate quantum-classical correspondence were found to provide a good description of the intermediate- and high-temperature regimes over all wave-vector and energy scales, and the crossover from quantum to classical dynamics observed around $\Theta_{CW}/S$, where the spin S=5/2. A characterisation of the data over the whole wave-vector/energy/temperature parameter space is given. In this, $T^2$ behaviour is found to dominate the wave-vector and temperature dependence of the line widths over a large parameter range, and no evidence of hydrodynamic behaviour or dynamical scaling behaviour found within the accuracy of the data sets. |
| spellingShingle | Huberman, T Tennant, D Cowley, R Coldea, R Frost, C A study of the quantum classical crossover in the spin dynamics of the 2D S=5/2 antiferromagnet Rb2MnF4: neutron scattering, computer simulations, and analytic theories |
| title | A study of the quantum classical crossover in the spin dynamics of the
2D S=5/2 antiferromagnet Rb2MnF4: neutron scattering, computer simulations,
and analytic theories |
| title_full | A study of the quantum classical crossover in the spin dynamics of the
2D S=5/2 antiferromagnet Rb2MnF4: neutron scattering, computer simulations,
and analytic theories |
| title_fullStr | A study of the quantum classical crossover in the spin dynamics of the
2D S=5/2 antiferromagnet Rb2MnF4: neutron scattering, computer simulations,
and analytic theories |
| title_full_unstemmed | A study of the quantum classical crossover in the spin dynamics of the
2D S=5/2 antiferromagnet Rb2MnF4: neutron scattering, computer simulations,
and analytic theories |
| title_short | A study of the quantum classical crossover in the spin dynamics of the
2D S=5/2 antiferromagnet Rb2MnF4: neutron scattering, computer simulations,
and analytic theories |
| title_sort | study of the quantum classical crossover in the spin dynamics of the 2d s 5 2 antiferromagnet rb2mnf4 neutron scattering computer simulations and analytic theories |
| work_keys_str_mv | AT hubermant astudyofthequantumclassicalcrossoverinthespindynamicsofthe2ds52antiferromagnetrb2mnf4neutronscatteringcomputersimulationsandanalytictheories AT tennantd astudyofthequantumclassicalcrossoverinthespindynamicsofthe2ds52antiferromagnetrb2mnf4neutronscatteringcomputersimulationsandanalytictheories AT cowleyr astudyofthequantumclassicalcrossoverinthespindynamicsofthe2ds52antiferromagnetrb2mnf4neutronscatteringcomputersimulationsandanalytictheories AT coldear astudyofthequantumclassicalcrossoverinthespindynamicsofthe2ds52antiferromagnetrb2mnf4neutronscatteringcomputersimulationsandanalytictheories AT frostc astudyofthequantumclassicalcrossoverinthespindynamicsofthe2ds52antiferromagnetrb2mnf4neutronscatteringcomputersimulationsandanalytictheories AT hubermant studyofthequantumclassicalcrossoverinthespindynamicsofthe2ds52antiferromagnetrb2mnf4neutronscatteringcomputersimulationsandanalytictheories AT tennantd studyofthequantumclassicalcrossoverinthespindynamicsofthe2ds52antiferromagnetrb2mnf4neutronscatteringcomputersimulationsandanalytictheories AT cowleyr studyofthequantumclassicalcrossoverinthespindynamicsofthe2ds52antiferromagnetrb2mnf4neutronscatteringcomputersimulationsandanalytictheories AT coldear studyofthequantumclassicalcrossoverinthespindynamicsofthe2ds52antiferromagnetrb2mnf4neutronscatteringcomputersimulationsandanalytictheories AT frostc studyofthequantumclassicalcrossoverinthespindynamicsofthe2ds52antiferromagnetrb2mnf4neutronscatteringcomputersimulationsandanalytictheories |