Magnetism and phase stability of R(Co,M)7 pseudobinary intermetallics with TbCu7-type structure.

Pseudobinary RCo7-xMx intermetallic compounds with TbCu7-type structure have been synthesized, and their structural and magnetic properties have been investigated using powder x-ray diffraction and magnetic measurements. Based upon the structural analysis, the stabilized element M occupies the 2e or the 3g position depending on its electronegativity. RCo7-xMx compounds exhibit ferromagnetic order with high Curie temperature. In addition, the uniaxial magnetocrystalline anisotropy is observed in SmCo7-xMx intermetallics. The magnetic moments have been investigated using a modified magnetic valence model with the equation <Zm>=±xRZmR+xTZmT+2Nsp↑∑ixi, where the magnetic moment contributed by 4f transition metal is corrected from its chemical valence numbers of rare earth in the original magnetic valence model to the theoretical value of gJμBJ. It is also assumed that the nonmagnetic metal has no contribution to the moment. The corrected model can also be used to calculate the moments of the other strong ferromagnetic intermetallics such as R–(T,M) 1:5, 2:17, and R2Fe14B, etc. This model could estimate and even predict the moments as long as the composition of the ferromagnetic alloy is known. [ABSTRACT FROM AUTHOR]