Giant magnetoresistance in intermetallics

Some typical examples of large magnetoresistance effects observed in intermetallic compounds are reviewed and briefly compared with the giant magnetoresistance (GMR) of magnetic multilayers. Basically, the large magnetoresistance changes are observed at metamagnetic transitions in two classes of intermetallics, antiferromagnetics and spin fluctuators. In the former case, a metamagnetic-transition is connected with the suppression of the antiferromagnetic coupling between magnetic moments as discussed with several examples of f-electron materials (NdGa ₂, UNiGa and other UTX antiferromagnets). The latter class is represented by the RCo₂ compounds in which a large resistivity drop is connected with the formation and ferromagnetic ordering of Co magnetic moments, which leads to the suppression of the spin fluctuation scattering of conduction electrons. In FeRh based alloys we observe combination of both phenomena, the suppression of antiferromagnetic coupling in the Fe sublattice and the formation of Rh moments. The possibilities of tuning the material parameters desired for applications are discussed with several examples of SmMn₂Ge ₂, Ce(Fe,T)₂, Ce(Fe,X)₂, (Mn,T)₂ Sb and MnPtAl