Spatially resolved modelling of inhomogeneous materials with a first order magnetic phase transition

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Abstract

We present a numerical model that can simulate a magnetocaloric sample on the grain size level, including magnetostatics, heat transfer, local hysteresis and spatial variation of stoichiometry expressed as a variation in Curie temperature, . Grain structure of a sample is realised as a number of regions each having a uniform and defined through a Voronoi-map. We show that demagnetising effects, caused by a finite sample size, and spatial variation in can account for the previously experimentally observed 'virgin' effects in the adiabatic temperature change and isothermal entropy change, respectively and first order reversal effect as a function of temperature. We conclude that even a very little variation in local stoichiometry of less than a percent, corresponding to a standard deviation in of for has a significant impact on the overall properties and history dependence of a sample.
Original languageEnglish
Article number414002
JournalJournal of Physics D: Applied Physics
Volume50
Issue number41
Number of pages9
ISSN0022-3727
DOIs
Publication statusPublished - 2017

Keywords

  • First order phase change
  • Magnetocaloric
  • Hysteresis
  • Model

Cite this

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title = "Spatially resolved modelling of inhomogeneous materials with a first order magnetic phase transition",
abstract = "We present a numerical model that can simulate a magnetocaloric sample on the grain size level, including magnetostatics, heat transfer, local hysteresis and spatial variation of stoichiometry expressed as a variation in Curie temperature, . Grain structure of a sample is realised as a number of regions each having a uniform and defined through a Voronoi-map. We show that demagnetising effects, caused by a finite sample size, and spatial variation in can account for the previously experimentally observed 'virgin' effects in the adiabatic temperature change and isothermal entropy change, respectively and first order reversal effect as a function of temperature. We conclude that even a very little variation in local stoichiometry of less than a percent, corresponding to a standard deviation in of for has a significant impact on the overall properties and history dependence of a sample.",
keywords = "First order phase change, Magnetocaloric, Hysteresis, Model",
author = "Nielsen, {Kaspar Kirstein} and Christian Bahl and Anders Smith and Rasmus Bj{\o}rk",
year = "2017",
doi = "10.1088/1361-6463/aa86e2",
language = "English",
volume = "50",
journal = "Journal of Physics D: Applied Physics",
issn = "0022-3727",
publisher = "IOP Publishing",
number = "41",

}

Spatially resolved modelling of inhomogeneous materials with a first order magnetic phase transition. / Nielsen, Kaspar Kirstein; Bahl, Christian; Smith, Anders; Bjørk, Rasmus.

In: Journal of Physics D: Applied Physics, Vol. 50, No. 41, 414002, 2017.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Spatially resolved modelling of inhomogeneous materials with a first order magnetic phase transition

AU - Nielsen, Kaspar Kirstein

AU - Bahl, Christian

AU - Smith, Anders

AU - Bjørk, Rasmus

PY - 2017

Y1 - 2017

N2 - We present a numerical model that can simulate a magnetocaloric sample on the grain size level, including magnetostatics, heat transfer, local hysteresis and spatial variation of stoichiometry expressed as a variation in Curie temperature, . Grain structure of a sample is realised as a number of regions each having a uniform and defined through a Voronoi-map. We show that demagnetising effects, caused by a finite sample size, and spatial variation in can account for the previously experimentally observed 'virgin' effects in the adiabatic temperature change and isothermal entropy change, respectively and first order reversal effect as a function of temperature. We conclude that even a very little variation in local stoichiometry of less than a percent, corresponding to a standard deviation in of for has a significant impact on the overall properties and history dependence of a sample.

AB - We present a numerical model that can simulate a magnetocaloric sample on the grain size level, including magnetostatics, heat transfer, local hysteresis and spatial variation of stoichiometry expressed as a variation in Curie temperature, . Grain structure of a sample is realised as a number of regions each having a uniform and defined through a Voronoi-map. We show that demagnetising effects, caused by a finite sample size, and spatial variation in can account for the previously experimentally observed 'virgin' effects in the adiabatic temperature change and isothermal entropy change, respectively and first order reversal effect as a function of temperature. We conclude that even a very little variation in local stoichiometry of less than a percent, corresponding to a standard deviation in of for has a significant impact on the overall properties and history dependence of a sample.

KW - First order phase change

KW - Magnetocaloric

KW - Hysteresis

KW - Model

U2 - 10.1088/1361-6463/aa86e2

DO - 10.1088/1361-6463/aa86e2

M3 - Journal article

VL - 50

JO - Journal of Physics D: Applied Physics

JF - Journal of Physics D: Applied Physics

SN - 0022-3727

IS - 41

M1 - 414002

ER -