Physical properties of GdFe 2 (Al x Zn 1 − x ) 20

The high ferromagnetic ordering temperature of the dilute, rare-earth-bearing, intermetallic compound ${\mathrm{GdFe}}_{2}{\mathrm{Zn}}_{20}$ has been understood as being the consequence of the Gd${}^{3+}$ moment being embedded in a nearly ferromagnetic Fermi liquid. To test this understanding in detail, single crystals of the pseudoternary series ${\mathrm{GdFe}}_{2}({\mathrm{Al}}_{x}{\mathrm{Zn}}_{1\ensuremath{-}x}{)}_{20}$ ($x\ensuremath{\leqslant}0.122$) and ${\mathrm{YFe}}_{2}({\mathrm{Al}}_{x}{\mathrm{Zn}}_{1\ensuremath{-}x}{)}_{20}$ ($x\ensuremath{\leqslant}0.121$) were grown out of Zn-rich solution. Magnetization, heat capacity, and resistivity measurements show that, with Al doping, the ferromagnetic phase transition temperatures of the ${\mathrm{GdFe}}_{2}({\mathrm{Al}}_{x}{\mathrm{Zn}}_{1\ensuremath{-}x}{)}_{20}$ compounds decrease from 86 K ($x=$ 0) to 10 K ($x=$ 0.122); for the nonmagnetic analog, the ${\mathrm{YFe}}_{2}({\mathrm{Al}}_{x}{\mathrm{Zn}}_{1\ensuremath{-}x}{)}_{20}$ series, the Stoner enhancement factor $Z$ decreases from 0.88 ($x=$ 0) to 0.35 ($x=$ 0.121) in a similar manner. Tight-binding linear-muffin-tin orbital atomic-sphere approximation band structure calculations are used to rationalize this trend. These results, together with the earlier studies of the $R({\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}{)}_{2}{\mathrm{Zn}}_{20}$ ($R=$ Gd and Y) series, clearly highlight the importance of band filling and the applicability of even a simple, rigid-band model to these compounds.