Adiabatic physics of an exchange-coupled spin-dimer system: Magnetocaloric effect, zero-point fluctuations, and possible two-dimensional universal behavior

Brambleby, J.; Goddard, P.A.; Singleton, J.; Jaime, M.; Lancaster, T.; Huang, L.; Wosnitza, J.; Topping, C.V.; Carreiro, K.E.; Tran, H.E.; Manson, Z.E.; Manson, J.L.

doi:10.1103/physrevb.95.024404

Adiabatic physics of an exchange-coupled spin-dimer system: Magnetocaloric effect, zero-point fluctuations, and possible two-dimensional universal behavior

Brambleby, J.; Goddard, P.A.; Singleton, J.; Jaime, M.; Lancaster, T.; Huang, L.; Wosnitza, J.; Topping, C.V.; Carreiro, K.E.; Tran, H.E.; Manson, Z.E.; Manson, J.L.

Authors

J. Brambleby

P.A. Goddard

J. Singleton

M. Jaime

Professor Tom Lancaster tom.lancaster@durham.ac.uk
Professor

L. Huang

J. Wosnitza

C.V. Topping

K.E. Carreiro

H.E. Tran

Z.E. Manson

J.L. Manson

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.

Citation

Brambleby, J., Goddard, P., Singleton, J., Jaime, M., Lancaster, T., Huang, L., …Manson, J. (2017). Adiabatic physics of an exchange-coupled spin-dimer system: Magnetocaloric effect, zero-point fluctuations, and possible two-dimensional universal behavior. Physical Review B, 95(2), Article 024404. https://doi.org/10.1103/physrevb.95.024404

Journal Article Type	Article
Acceptance Date	Dec 6, 2016
Online Publication Date	Jan 5, 2017
Publication Date	Jan 5, 2017
Deposit Date	Jan 18, 2017
Publicly Available Date	Jan 25, 2017
Journal	Physical Review B
Print ISSN	2469-9950
Electronic ISSN	2469-9969
Publisher	American Physical Society
Peer Reviewed	Peer Reviewed
Volume	95
Issue	2
Article Number	024404
DOI	https://doi.org/10.1103/physrevb.95.024404
Related Public URLs	https://arxiv.org/abs/1610.08661

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