Mendive-Tapia, Eduardo and Staunton, Julie B. (2020) Caloric effects around phase transitions in magnetic materials described by ab initio theory : the electronic glue and fluctuating local moments. Journal of Applied Physics, 127 (11). 113903. doi:10.1063/5.0003243 ISSN 0021-8979.

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Abstract

We describe magneto-, baro-, and elastocaloric effects (MCEs, BCEs, and eCEs) in materials, which possess both discontinuous (first-order) and continuous (second-order) magnetic phase transitions. Our ab initio theory of the interacting electrons of materials in terms of disordered local moments has produced explicit mechanisms for the drivers of these transitions, and here, we study associated caloric effects in three case studies where both types of transition are evident. Our earlier work had described FeRh’s magnetic phase diagram and large MCE. Here, we present calculations of its substantial BCE and eCE. We describe the MCE of dysprosium and find very good agreement with experimental values for isothermal entropy ((ΔSiso) and adiabatic temperature (ΔTad) changes over a large temperature span and different applied magnetic field values. We examine the conditions for optimal values of both ΔSiso and ΔTad that comply with a Clausius–Clapeyron analysis, which we use to propose a promising elastocaloric cooling cycle arising from the unusual dependence of the entropy on temperature and biaxial strain found in our third case study—the Mn3GaN antiperovskite. We explain how both ΔSiso and ΔTad can be kept large by exploiting the complex tensile strain–temperature magnetic phase diagram, which we had earlier predicted for this material and also propose that hysteresis effects will be absent from half of the caloric cycle. This rich and complex behavior stems from the frustrated nature of the interactions among the Mn local moments.

Item Type:	Journal Article
Subjects:	Q Science > QC Physics
Divisions:	Faculty of Science, Engineering and Medicine > Science > Physics
Library of Congress Subject Headings (LCSH):	Magnetic materials , Cooling curves
Journal or Publication Title:	Journal of Applied Physics
Publisher:	American Institute of Physics
ISSN:	0021-8979
Official Date:	18 March 2020
Dates:	Date Event 18 March 2020 Published 5 March 2020 Accepted
Volume:	127
Number:	11
Article Number:	113903
DOI:	10.1063/5.0003243
Status:	Peer Reviewed
Publication Status:	Published
Reuse Statement (publisher, data, author rights):	“This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in J. Appl. Phys. 127, 113903 (2020); https://doi.org/10.1063/5.0003243 and may be found at http://dx.doi.org/10.1063/5.0003243
Access rights to Published version:	Restricted or Subscription Access
Date of first compliant deposit:	19 March 2020
Date of first compliant Open Access:	23 March 2020
RIOXX Funder/Project Grant:	Project/Grant ID RIOXX Funder Name Funder ID EP/J06750/1 [EPSRC] Engineering and Physical Sciences Research Council http://dx.doi.org/10.13039/501100000266 EP/M028941/1 [EPSRC] Engineering and Physical Sciences Research Council http://dx.doi.org/10.13039/501100000266 HI1300/6-2 [EPSRC] Engineering and Physical Sciences Research Council http://dx.doi.org/10.13039/501100000266

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