Transport properties of RECo2compounds (RE=Tb, Dy, Ho, Er, Y)

Abstract

The temperature dependence of the thermopower S and electrical resistivity rho of ReCo₂ compounds (RE=Tb, Dy, Ho, and Y) have been measured. Both the S versus T and the rho versus T curves are characterised by discontinuities at T_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.