MAGNETIC PHASE-DIAGRAMS OF NDRU2SI2 AND TBRU2SI2 COMPOUNDS

Here we report a detailed study providing complete H-T phase diagrams for both NdRu2Si2 and TbRu2Si2 intermetallic compounds, based on high resolution SQUID magnetization measurements, in the temperature range 2-300 K and in applied magnetic fields up to 5 T, using c-axis magneti cally oriented powders. For NdRu2Si2, our results are in good agreemen t with recent neutron diffraction work under applied magnetic fields, confirming the appearance of an intermediate (temperature and field) f errimagnetic phase responsible for the two-step metamagnetic process o bserved in the temperature range 16-22.5 K. Our isofield magnetization curves provide unambiguous evidence on the decomposition of this ferr imagnetic phase into ferromagnetic and antiferromagnetic components. F urthermore, at low temperatures and low fields, we observe, in this co mpound, the presence of thermal irreversibility effects. For TbRu2Si2, we present an experimental account, on its H-T phase diagram, which s hows striking differences with respect to that of NdRu2Si2. In particu lar, the ferrimagnetic phase, which sets in at 50 K, persists down to the lowest temperature. In addition, we observe reentrant ferrimagneti sm in this compound (ferri-ferro-ferri) under applied fields in the ra nge 28-31 kOe.