Phase relationships, and the structural, magnetic, and thermodynamic properties in the Sm5SixGe4-x pseudobinary system

The crystallography, phase relationships, and physical properties of the Sm5SixGe4-x alloys with 0 <= x <= 4 have been investigated by using x-ray powder diffraction, dc magnetization, and heat capacity measurements between similar to 3 K and 350 K in magnetic fields ranging from 0 and 10 T. Similar to Gd5SixGe4-x, there are three distinct phase regions in the Sm5SixGe4-x system: the Gd5Si4 type for Si-rich compositions, the Gd5Si2Ge2 type for intermediate range of concentrations, and the Sm5Ge4 type for Ge-rich alloys. The magnetic properties of the Sm5SixGe4-x compounds can be well described by considering the temperature-independent Van Vleck term due to a small energy separation between the ground state and the first excited state of Sm3+ ions. Compared with other light lanthanide R5SixGe4-x, magnetic ordering temperatures of Sm5SixGe4-x compounds are much higher than expected from the de Gennes scaling. The change in the magnetic behaviors with the substitution of Ge by Si is also similar to that observed in the Gd5SixGe4-x system. The external magnetic fields up to 10 T have no effect on the magnetism of the Sm5SixGe4-x alloys.