Abstract
Magnetic, thermal, and transport properties of a U3Fe4Ge4 single crystal have been studied. The compound crystallizes in the orthorhombic Gd3Cu4Ge4 structure type.
U3Fe4Ge4 displays ferromagnetic order below the Curie temperature T-C = 18 K. The magnetism originates from the uranium sublattice, as iron atoms have no ordered magnetic moments.
U3Fe4Ge4 exhibits a pronounced easy-axis anisotropy with the anisotropy field exceeding 60 T. The spontaneous magnetic moment is M-s = 1.2 mu(B)/f.u. at T = 2 K.
Magnetic contribution to specific heat shows a gap excitation behavior with Delta = 4 meV, which can be related to the magnon gap due to the anisotropy. The Sommerfeld coefficient of the electronic specific heat is gamma = 57 mJ/(mol-U K-2) in the ordered state, whereas it is much higher (145 mJ/(mol-U K-2) if derived from the paramagnetic state.
Electrical resistivity has very high values on the m Omega cm range.