THE MAGNETIC PHASE-TRANSITION IN ZRZN2

The critical behaviour of the ferro-paramagnetic phase transformation has been analysed in the weak itinerant-electron ferromagnet, ZrZn2. T he critical exponents beta, gamma and gamma' describe the temperature dependence of the spontaneous polarization J(S) and the inverse zero-f ield susceptibility chi(-1), whereas the exponent delta determines the field dependence of the polarization at the Curie temperature, T-C. T o complete the description of the critical behaviour the reduced criti cal amplitudes J(0)/J(S)(0), mu h(0)/(k(B)T(C)) and DJ(0)(delta)/h(0) were also determined. The exponent values obtained are in good agreeme nt with the theoretical predictions of the mean field theory, which sh ould be valid in the case of magnetic long-range interactions. In the case of the critical amplitudes, the values cannot be correlated to a particular model.