Thermodynamics of thermomagnetic effects and application to magnetic refrigerators and heat pumps

Magnetic refrigeration has been used for over 60 years as a technology to achieve temperatures below 1 K. However, in the last twenty years, the technology has been developing for refrigeration applications above 1 K up to including heat pumps above room temperature. The work has been multinational in scope and has focused on the analysis of magnetic thermodynamic systems, investigation of magnetic materials suitable for refrigerants, and development of prototype refrigerators. The aim of this paper is an examination of the magnetocaloric effect and of the various thermodynamic relations of magnetic systems for which it is possible to assume an equation of the kind f(H, M, T) similar to the relation f(p, v, T) utilized for fluids. A a synthetic examination of several theoretical magnetic cycles is then carried out.