On the magnetization of the Ho(Co1-xRhx)(2) pseudobinary

In this paper we study the effects of temperature and Rh concentration on t he magnetization of the Ho(Co1-xRhx)(2) pseudobinary. To this end we use a model in which the localized spins are immersed in an effective subsystem o f itinerant electrons. Using functional integral techniques combined with t he molecular-field approximation, we calculate the temperature dependence o f the magnetization for several values of the Ph concentration. The curve o btained for the clean limit x = 0 shows a first-order phase transition. Abo ve a critical Rh concentration of 10%, the phase transition changes to seco nd order, in good agreement with experimental data from thermal and magneto striction measurements.