(Tri)critical Phase Transitions in Magnetocaloric Materials
Karl G. Sandeman
Dept. of Physics
Imperial College, London
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 . 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 characterisation 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 .
 S. Fähler et al., Adv. Eng. Mater. 14 10-19 (2012).
 K.G. Sandeman, Scripta Materialia 67 566-571 (2012)
 A. Barcza et al., Phys. Rev. Lett. 104 247202 (2010)
 J.B. Staunton et al., arXiv:cond-mat/1206.3394
The research leading to these results has received funding from the European Community's 7th Framework Programme under grant agreement No. 214864 ("SSEEC", www.sseec.eu). KGS acknowledges financial support from The Royal Society.