Magnetic properties of iron-rich Nd2−yDyyFe17−xSix mixed rare-earth system

Abstract

A series of Nd2−yDyyFe17−xSix solid solutions with x=0, 1, 2, and 3 and y=0, 0.5, 1.0, 1.5, and 2.0 were prepared by induction melting stoichiometric amounts of high-purity elements. The x-ray diffraction data confirmed that the postannealed samples are 2:17 intermetallics of the R3̄m space group. The lattice parameters and unit-cell volumes were calculated using FULLPROF to analyze the neutron diffraction (ND) data. It was observed that for a particular y, the unit-cell volume decreased almost linearly with increasing silicon content (x⩽3), as is observed for single rare-earth 2:17 intermetallic compounds. For a given x, the cell volume decreased almost linearly with the increasing replacement of neodymium with dysprosium. The ND studies revealed additional density along the c-axis chains of Fe dumbells and rare-earth atoms. The perfect a-b-c stacking of the CaCu5 layers with a regular one third replacement of the rare-earth atoms by Fe dumbells appear to be broken, resulting in a disordered rhombohedral structure. The Curie temperature measurements showed no particular kind of dependence with increasing y. For a fixed content of Dy, an increase in Curie temperature from 61.46 °C to 236 °C for y=0, 69.3 °C to 241 °C for y=0.5, 76 °C to 227 °C for y=1, 95.45 °C to 224 °C for y=1.5, and 94.19 °C to 226 °C for y=2 was observed with increasing x (x⩽3). With increasing y, there was almost a linear decrease in magnetization of about 46% for x=0, 49% for x=1, 52% for x=2, and 50% for x=3. For a particular y with increasing x, the magnetization appears to reach saturation between x=1 and x=2.