Transport properties of RECo2 compounds (RE = Tb, Dy, Ho, Er, Y)

The temperature dependence of the thermopower S and electrical resistivity rho of RECo2 compounds (RE = Tb, Dy, Ho, Er and Y) have been measured. Both the S versus T and the rho versus T curves are characterised by discontinuities at Tsub(c) for ErCo2, HoCo2 and DyCo2. The magnitude of these steps increases with decreasing ordering temperatures. This behaviour is caused by the magnetic first-order transition observed in these compounds. The results for TbCo2 point to a second-order magnetic transition. The discussion is based on the assumption that YCo2 represents the non-magnetic starting compound, in which mainly the Co 3d matrix defines physical properties like susceptibility, resistivity, thermopower, etc. Furthermore, it is assumed that the density-of-states function in the paramagnetic state of the RECo2 compounds in question is equal to that in YCo2, where the Fermi energy is situated in a region of steep decrease of the density-of-states curve. (author)