Multiple magnetic phases and magnetization plateaus in TbRh6Ge4

We probe the magnetic order in single crystals of TbRh6Ge4 using electrical transport, magnetization, and thermodynamic measurements. TbRh6Ge4 crystallizes in the noncentrosymmetric tetragonal LiCo6P4-type structure, where the Tb ions form a triangular lattice in the basal plane and chains along the c axis. This compound undergoes a second-order antiferromagnetic transition at TN = 12.7 K, which is followed by an additional transition at TM = 2.8 K. When fields are applied along the easy c axis, multiple metamagnetic transitions are observed, where there are plateaus at 1/9 and 1/3 of the saturation magnetization. We map the field-temperature phase diagram revealing complex magnetism, where antiferromagnetic coupling within the basal plane may lead to significant magnetic frustration.