Abstract
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-toparamagnet 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 similar to 10 GPa. At ambient pressure, UCoGa exhibits collinear ferromagnetic ordering of uranium magnetic moments mu(U) similar to 0.74 mu B (at 2 K) aligned along the c-axis of the hexagonal crystal structure below Curie temperature T-C = 48K.
With the application of pressure, gradual decrease of both, T-C and the saturated magnetic moment, has been observed up to pressures similar to 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 similar to 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 similar to 30K and similar to 6GPa. (C) 2017 Author(s).