DENSITY OF STATES AND MAGNETIC-PROPERTIES OF THE RARE-EARTH COMPOUNDS RFE2, RCO2 AND RNI2

The density of states of yttrium compounds YM//2 (M equals Fe, Co, Ni) is calculated within a tight-binding scheme. Using the Stoner model, conclusions are drawn about their magnetic and electronic properties. In YCo//2, the authors show that one has to introduce paramagnon effects in order to explain the electronic properties. The additional d-f interaction introduced by rare-earth atoms (R) in RM//2 is treated with a Hartree-Fock approximation. Little change is obtained in iron and nickel compounds. Conversely, in RCo//2 compounds, the exchange field due to the rare-earth atoms can produce collective metamagnetism as described by Wohlfarth and Rhodes and cobalt becomes magnetic. This effect stems from the position of the Fermi level of these compounds in a steep decrease of the density of states. Curie temperature, order of the transition and effect of an external magnetic field are studied following this method. Other consequences are drawn from the model.