Pressure-induced quantum phase transition in the itinerant ferromagnet UCoGa

Original · EN

In this paper, we report the results of a high pressure study of the itinerant 5f-electron ferromagnet UCoGa. The work is focused on probing the expected ferromagnet-to-paramagnet quantum phase transition induced by high pressure and on the general features of the P-T(-H) phase diagram. Diamond anvil cells were employed to measure the magnetization and electrical resistivity under pressures up to 10 GPa.At ambient pressure, UCoGa exhibits collinear ferromagnetic ordering of uranium magnetic moments μU 0.74 μB (at 2 K) aligned along the c-axis of the hexagonal crystal structure below Curie temperature TC = 48K. With the application of pressure, gradual decrease of both, TC and the saturated magnetic moment, has been observed up to pressures 6 GPa. This is followed by a sharp drop of magnetic moment and a sudden disappearance of the magnetic order at the pressure of 6.5 GPa, suggesting a first-order phase transition, as expected for a clean system. The low temperature power law dependence of the electrical resistivity shows distinct anomalies around the 6 GPa, consistent with the pressure evolution of the magnetic moment and the ordering temperature. The tricritical point of the UCoGa phase diagram is located at approximately 30 K and 6 GPa.