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Adiabatic physics of an exchange-coupled spin-dimer system : magnetocaloric effect, zero-point fluctuations, and possible two-dimensional universal behavior
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Brambleby, Jamie, Goddard, Paul, Singleton, J., Jaime, M., Lancaster, T., Huang, L., Wosnitza, J., Topping, C. V., Carreiro, K. E., Tran, H. E., Manson, Z. E. and Manson, J. L. (2017) Adiabatic physics of an exchange-coupled spin-dimer system : magnetocaloric effect, zero-point fluctuations, and possible two-dimensional universal behavior. Physical Review B (Condensed Matter and Materials Physics), 95 (2). 024404. doi:10.1103/PhysRevB.95.024404
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Official URL: http://dx.doi.org/10.1103/PhysRevB.95.024404
Abstract
We present the magnetic and thermal properties of the bosonic-superfluid phase in a spin-dimer network using both quasistatic and rapidly changing pulsed magnetic fields. The entropy derived from a heat-capacity study reveals that the pulsed-field measurements are strongly adiabatic in nature and are responsible for the onset of a significant magnetocaloric effect (MCE). In contrast to previous predictions we show that the MCE is not just confined to the critical regions, but occurs for all fields greater than zero at sufficiently low temperatures. We explain the MCE using a model of the thermal occupation of exchange-coupled dimer spin states and highlight that failure to take this effect into account inevitably leads to incorrect interpretations of experimental results. In addition, the heat capacity in our material is suggestive of an extraordinary contribution from zero-point fluctuations and appears to indicate universal behavior with different critical exponents at the two field-induced critical points. The data at the upper critical point, combined with the layered structure of the system, are consistent with a two-dimensional nature of spin excitations in the system.
| Item Type: | Journal Article | |||||||||||||||||||||
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| Subjects: | Q Science > QC Physics | |||||||||||||||||||||
| Divisions: | Faculty of Science > Physics | |||||||||||||||||||||
| Library of Congress Subject Headings (LCSH): | Nuclear spin , Thermodynamics, Bosons, Magnetic fields | |||||||||||||||||||||
| Journal or Publication Title: | Physical Review B (Condensed Matter and Materials Physics) | |||||||||||||||||||||
| Publisher: | American Physical Society | |||||||||||||||||||||
| ISSN: | 1098-0121 | |||||||||||||||||||||
| Official Date: | 5 January 2017 | |||||||||||||||||||||
| Dates: |
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| Date of first compliant deposit: | 20 January 2017 | |||||||||||||||||||||
| Volume: | 95 | |||||||||||||||||||||
| Number: | 2 | |||||||||||||||||||||
| Article Number: | 024404 | |||||||||||||||||||||
| DOI: | 10.1103/PhysRevB.95.024404 | |||||||||||||||||||||
| Status: | Peer Reviewed | |||||||||||||||||||||
| Publication Status: | Published | |||||||||||||||||||||
| Access rights to Published version: | Restricted or Subscription Access | |||||||||||||||||||||
| RIOXX Funder/Project Grant: |
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