Magnetic, Caloric and Crystallographic Properties of Dy5(SixGe1-x)4 Alloys

摘要

A study of a series of Dy5(SixGe1-x)4 alloys using dc and ac magnetic susceptibility, magnetization, heat capacity, and x-ray powder diffraction techniques revealed that the variation of the magnetic properties and crystal structures with composition is similar to that observed in the Gd5(SixGe1-x)4 system, except that the magnetic ordering temperatures are lower. The magnetic phase transition temperatures vary from (tilda) 46K (Dy5Ge4) to (tilda) 137K (Dy5Si4). The intermediate ternary phase Dy5Si3Ge undergoes a first order magnetic phase transition at (tilda) 65K. The value of magnetic entropy change for this composition is quite large (-34J/kgK for magnetic field change from 0 to 50kOe), compared to the values for the two end members (-7 J/kgK for Dy5Ge4 and -12.5J/kgK for Dy5Si4). The magnetization and ac susceptibility measurements showed that alloys with monoclinic crystal structure have a non-collinear ordering of the magnetic moments at low temperatures. The alloy Dy5Si3Ge appears to exhibit a FM phase transition below the Curie temperature at 65K. Also a series of critical fields are observed at low temperature during magnetization vs magnetic field measurements in all of the Dy5(SixGe1-x)4 alloys regardless type of crystal structure.