Ferromagnetic ordering in UFe0.5Ni0.5Al

Abstract

The alloy UFe0.5Ni0.5Al crystallizing in the hexagonal ZrNiAl-type structure has been studied by means of neutron powder diffraction and specific heat measurements. The Ni atoms occupy preferentially the (1b) sites. The transition into a ferromagnetic state at TC ∼ 55 K reported previously is corroborated by the occurrence of specific heat anomaly and magnetic reflections. The magnetic structure consists of the ferromagnetic (001)-planes with the magnetic moments parallel to the c-axis. At 1.4 K, the ordered uranium moment is about 0.6 μB. The low-temperature dependence of Cp may be described by an expression involving an energy gap in the magnon spectrum. The electronic coefficient of the specific heat is modestly enhanced and amounts to about 47 mJ/mol K2. This feature together with a small value of μord point to the strongly 5f-d hybridized character of the magnetism in UFe0.5Ni0.5Al.