Competing magnetic interactions in the intermetallic compound Ho_2Mn_3Si_5

摘要

The compound Ho_2Mn_3Si_5 exhibits multiple magnetic transitions: (ⅰ) an ordering at ～78 K, (ⅱ) a second magnetic transition at ～16 K, and (ⅲ) an anomaly at ～4 K. Its paramagnetic Curie temperature is found to be small but positive. Assuming a free ion effective paramagnetic moment of 10.6μ_B for Ho~(3+) ion, the effective paramagnetic moment per Mn in this compound is calculated to be 1.73μg, which indicates the itinerant nature of Mn d electrons. The various transitions in magnetization data are perhaps due to the ordering of rare earth and Mn moments. The magnetization at 2 K in applied fields of up to 7 T has linear field dependence, indicating dominant antiferromagnetic interactions in the system. Neutron diffraction studies point to a complex amplitude modulated incommensurate magnetic structure at 9 K.