Effect of Al Substitution on the Electronic and Magnetic Properties of GdCo$\text{}_{5}$

Experimental data show that aluminium doped RCo$\text{}_{5}$ systems crystallize in CaCu$\text{}_{5}$-type structure for most of the rare-earth elements (R). Al impurities randomly occupy one of the two possible positions (2c and 3g) and there is a critical concentration of Al, x$\text{}_{c}$=2.0, for RCo$\text{}_{5-x}$Al$\text{}_{x}$ when the Co sublattice becomes nonmagnetic. The ab initio self-consistent calculations show strong dependence of magnetic properties of GdCo$\text{}_{5-x}$Al$\text{}_{x}$ on concentration of Al and position of the impurities in the unit cell, furthermore to fulfil experimental observation of existence of critical concentration, x$\text{}_{c}$=2.0, the Al impurities should prefer 3g positions otherwise the magnetic moments on Co atoms do not vanish.