Field-induced magnetic structures in UNiGe

Below TN=50 K, UNiGe exhibits incommensurate (INC) antiferromagnetic (AF) order with an additional order–order (AF) phase transition at TM=42.5 K. The ground-state AF structure is characterized by a propagation vector (0,1/2,1/2). At 4.2 K, there are two field-induced transitions at 17 and 25 T for the b-axis and at 3 and 10 T for fields along c. No transitions are observed for the a∥B orientation up to 38 T. While the intermediate field-induced phases for both b∥B and c∥B geometries have propagation vector (0,1/3,1/3), the INC structure is characterized by a propagation vector (0,δ1, δ2). All phases have a non-collinear arrangement of U moments with all three components, i.e. also along the a-axis, which is the hard-magnetization direction. The field-forced ferromagnetic phase, which is established for c∥B above 10 T still exhibits a significant a-axis component. This suggests that the magnetic ordering in UNiGe is governed by anisotropic exchange interactions.