Physical properties of RCo2 Laves phases

The large variety of magnetic phenomena observed in the Co based Laves phas es are reviewed. Following the band structure calculations it is argued tha t the outstanding magnetic features of the RCo2 intermetallics are intimate ly related to the position of the Fermi level, which is near to a local pea k in N(epsilon). This is why the Co 3d-electron system reacts sensitively e ither to the molecular field of the R partner element or to the changes of external parameters such as a magnetic field or pressure. Magnetic, magneto elastic and transport measurements of RCo2 compounds and related pseudobina ries such as R(Co1-xAlx)(2) with R either magnetic or nonmagnetic rare eart h element are shown and discussed. The conditions for the appearance of iti nerant electron metamagnetism and spin fluctuations are outlined. In partic ular, the influences of spin fluctuations on physical properties, e.g, the susceptibility, thermal expansion and transport phenomena, are demonstrated .