Phase relationships, and structural, magnetic, and magnetocaloric properties in the Ce5Si4–Ce5Ge4 system

Abstract

The crystallography, phase relationships, and magnetic properties of the Ce5Si4−xGex alloys with 0≤x≤4 have been investigated by using x-ray powder diffraction and isothermal magnetization measurements. There are three different crystal structures in the Ce5Si4−xGex system: the Zr5Si4-type tetragonal structure with space group P41212 exists from 0≤x<2.15, the Gd5Si2Ge2-type monoclinic structure with space group P1121/a exists at x≈2.225, and the Sm5Ge4-type orthorhombic structure with space group Pnma is found for 2.4<x≤4. The magnetic ordering temperature increases when the tetragonal phase changes to the monoclinic phase, and then it remains composition independent throughout the orthorhombic phase, which is the opposite trend compared to that observed in the heavy lanthanide 5:4 compounds when Ge content increases. Another distinct difference is that Ce5Si4 exhibits an antiferromagnetic ground state while Ce5Ge4 phase orders ferromagnetically, which is reverse compared to the R5Si4−xGex systems where R=Gd and Tb. The magnetocaloric effect has been calculated from the magnetization data. The Ce5Ge4 has the maximum magnetic entropy change ΔSM(−11.6 J/kg K) at the Curie temperature of 11.5 K for a field change of 5 T.