Argonne National Laboratory

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(Tri)critical Phase Transitions in Magnetocaloric Materials

PSE/MSD Seminar
Karl G. Sandeman, Imperial College London
January 21, 2013 3:00PM to 4:00PM
Building 223, Room S105
Much of today's research in so-called functional materials is driven by the quest for technologies that use energy more efficiently and reduce our impact on the environment. Such pressures drive a renewed investigation of some of the most fundamental properties of condensed matter. Solid-state phase transitions are one good example. In order to find an energy efficient solution to the problem of reducing our use of HFCs in a variety of cooling applications, a new field has been defined.

In "ferroic cooling", a good solid refrigerant has a phase transition with a large entropy change, tuned by chemical composition over the temperature range of the particular application [1]. I will show how the search for suitable magnetic refrigerants leads to: a survey of novel critical and tricritical material systems [2,3], the development of characterization tools to study first order phase transitions, and hi-resolution neutron diffraction data that act as an ideal test of ab initio theories of finite temperature magnetism [4].  

[1] S. Fähler et al., Adv. Eng. Mater. 14 10-19 (2012)
[2] K.G. Sandeman, Scripta Materialia 67 566-571 (2012)
[3] A. Barcza et al., Phys. Rev. Lett. 104 247202 (2010)
[4] J.B. Staunton et al., arXiv:cond-mat/1206.3394