The influence of the lanthanide element on the magnetic properties of the R2(Co,Ga)17 alloys

The role of the substitution of Tb for Y atoms in the R-2(Co,Ga)(17) alloys is discussed on the basis of magnetic measurements in the temperature range 1.9-1000 K and in a magnetic field up to 5 T. The crystal structure of these compounds depends on Ga concentration and in the Y alloys demonstrate the following sequence of structure types: Th2Ni17 -> TbCu7 -> Th2Zn17, whereas in preliminary examination in the Th compounds only Th2Zn17-type has been detected. Our present research shows that in the Th system Th2Ni17 -> Th2Zn17 sequence exist. In both Tb-2(Co,Ga)(17) and Y-2(Co,Ga)(17) ternaries the substitution of Ga for Co atoms is a reason for the decreasing of Curie points whereas the same tendency in the saturation magnetization is observed only in the Y system. Examination of both families of the compounds allows to conclude that the substitution of the Th for the Y atoms only slightly decreases Curie points and strongly decreases the values of the saturation magnetic moment proving that the coupling scheme of the 4f-3d compounds is preserved, however, the simple comparison is only possible for the materials with same structure. (C) 2007 Elsevier B.V. All rights reserved.