Magnetic refrigeration can be viewed as an alternative to the conventional vapor-compression technology. Magnetic refrigeration owes its renewed interest not only to its comparatively high efficiency but also to the fact that it is an environmentally friendly techniques, avoiding ozone-depleting or global-warming gases. This opens new research opportunities that have culminated in a worldwide search for novel magnetocaloric materials. In practice, magnetic refrigeration requires the combination of a magnetic field source of high strength and a material with a sufficiently high magnetocaloric effect (MCE). When looking at domestic applications, the best choice of the field source would be a permanent magnet. However, the field generated by permanent magnets falls typically into the 1-2 Tesla range and the MCE of most magnetic materials is too small for such a low field change to result in sufficient cooling power. Recent research activities have therefore been focused on materials with higher than average MCE value, and the prerequisites for attaining high MCEs will be briefly addressed in this talk. A commercially important aspect is the materials cost. Magnetocaloric materials based on magnetic 3d elements are much less expensive than those based on rare earth elements. In the present talk we will concentrate mainly on the results obtained with the former type of materials. |