Volume collapse in Ce alloys under pressure by neutron diffraction

Neutron-diffraction measurements under hydrostatic pressure up to 10 kbar were performed on the Ce$_{0.9-x}$La$_{x}$Th$_{0.10}$ system to investigate the tricritical point at $x_{c}$ = 0.14. For $x < \quad x_{c}$, we observe first-order transitions with a pressure derivative of the transition temperature, d$T$/d$P$ = 20 K/kbar. For $x \quad > \quad x_{c}$ we observe a continuous transition that is second order, which again demonstrates a tri-critical point in the pressure-temperature phase diagram. The results will be presented and discussed.