Ferromagnetic and antiferromagnetic arrangements of uranium magnetic moments in non-stoichiometric UNi1-xGa1+x compounds

The local magnetic configurations in the non-stoichiometric UNi1-xGa1+x (x = +/- 0.03) compounds have been investigated by Mossbauer spectroscopy technique. The compounds are characterized by coexistence of ferro- and antiferromagnetic alignments of uranium magnetic moments in the adjacent U-Ni layers. At 5 K, a rather small deviation from the exact 1: 1: 1 stoichiometry (both excess, as well as deficit, of Ni) leads to the drastic increase in the fraction of the ferromagnetic local configuration (up to 73% at x = +0.03 and 66% at x = -0.03). The fraction of ferromagnetic domains decreases gradually with temperature. At the vicinity of the Curie temperature, the fraction of the ferromagnetic configuration approaches 33% which corresponds to the complete restoration of the "ideal" antiferromagnetic structure, which is peculiar to the stoichiometric UNiGa compound. (C) 2008 Elsevier Ltd. All rights reserved.