ABSTRACT
In this chapter we consider intermetallic magnetic compounds containing rare earth elements. Among them, two large groups of the materials where the magnetocaloric properties were studied can be singled out-alloys and compounds between rare earth and nonmagnetic elements and those between rare earth and 3d metal elements. In the first group RE ions are the only carriers of the magnetic moment (to this group the compounds R-Ni can also be attributed because Ni in them does not have a magnetic moment). These materials can display not only ferromagnetic but also more complex types of magnetic ordering, in particular due to the crystalline field effects. In RE-Fe compounds there are two magnetic sublattices, Fe and RE, ordered ferrimagnetically, and they exhibit magnetic behaviour analogous to that observed in rare earth iron garnets. The magnetic moment of Co in RE-Co compounds has an itinerant nature and according to the existing models is induced by a molecular field acting from an RE sublattice. The transition to magnetically ordered state in some of these materials is of the first order. There is also a metamagnetic transition induced by an external magnetic field related to the itinerant behaviour of the Co moment. Because of that it is possible to expect essential values of the magnetocaloric effect in RE-Co compounds.
