The Magnetic Phase Transition of CoS $_{2 - {\rm x}}$ Se $_{{\rm x}}$

The nature of the magnetic phase transition of the itinerant ferromagnet CoS 2 has been studied. We have measured high-pressure X-ray diffraction and magnetization, at different temperatures and fields. Our results are discussed on the basis of a thermodynamic model applicable to itinerant ferromagnets with strong spin fluctuations.