Structural and magnetic properties of arc-melted carbides (R = Y or Sm)

Abstract

Using x-ray diffraction, powder neutron diffraction, high-field magnetization measurement and thermomagnetic analysis, we have studied the structural and magnetic properties of alloys ( R = Sm or Y) made by arc melting, in which the carbon was added using Fe - C alloy. Both samples are found to be nearly single phase with -type structure and with a small amount of -Fe phase (less than 4 wt%). The neutron diffraction of the Y-containing compound indicates that the real composition of the main phase is , and that the carbon atoms occupy not only the interstitial 2b site but also the substitutional 8i site. The Fe moments of the 8i site as well as the 8j site are found to be reduced in the compound compared with its carbon-free counterpart. The decrease in the Fe moment at the 8j site is due to the surrounding interstitial carbon atoms, while the decrease in the Fe moment at the 8i site is ascribed to the surrounding substitutional carbon atoms as nearest neighbours. The high-field magnetization measurements indicate that the anistropy field of and are slightly higher than those of and , respectively. In , the magnetization curve in the hard direction at 4.2 K shows a first-order-magnetization-process (FOMP)-like or quasi-FOMP-like transition.