Magnetocaloric materials

In the last decade of the twentieth century there has been a significant in crease in research on a more than 100-year old phenomenon-the magnetocalori c effect (MCE). As a result, many new materials with large MCEs (and many w ith lesser values) have been discovered, and a much better understanding of this magneto-thermal property has resulted. In this review we briefly disc uss the principles of magnetic cooling (and heating); the measurement of th e magnetocaloric properties by direct and indirect techniques; the special problems that can arise; and the MCE properties of the 4f lanthanide metals , their intra-lanthanide alloys and their compounds [including the giant MC E Gd-5(SixGe1-x)(4) phases]; the 3d transition metals, their alloys and com pounds; and mixed lanthanide-3d transition metal materials (including the L a manganites).