Effect of localization of 5f-electrons and pressure on magnetism in uranium intermetallics in spin-fluctuation theory

摘要

UCoGa and URhGa, two isostructural compounds, show opposite signs of the initial response of Curie temperature to applied hydrostatic pressure. To determine the physical origin of this difference the magnetization data measured with respect to temperature, magnetic field, and hydrostatic pressure were analyzed in the framework of the Takahashi spin-fluctuation theory. The parameters T_0 and T_A characterizing the distribution widths of the spin-fluctuation spectrum in the energy and wave-vector space, respectively, and T_c/T_0, the degree of the 5f-electron localization, have been determined. Examination of available experimental data for the other VTX (T = a transition metal. X = Al, Ga) ferromagnets having the ZrNiAl-type structure revealed some correlations between the degree of the 5/-electron localization represented by the spin-fluctuation parameters and the response of Curie temperature on the applied pressure. The extent to which this correlation can be used to describe the localization and magnetic behavior of other uranium ferromagnetic compounds is discussed.