Physical properties of GdFe₂(Al_xZn _1-x)₂₀

The high ferromagnetic ordering temperature of the dilute, rare-earth-bearing, intermetallic compound GdFe₂Zn₂₀ has been understood as being the consequence of the Gd3⁺ moment being embedded in a nearly ferromagnetic Fermi liquid. To test this understanding in detail, single crystals of the pseudoternary series GdFe₂(Al _xZn_1-x)₂₀ (x≤0.122) and YFe ₂(Al_xZn_1-x)₂₀ (x≤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 GdFe₂(Al_xZn_1-x) ₂₀ compounds decrease from 86 K (x= 0) to 10 K (x= 0.122); for the nonmagnetic analog, the YFe₂(Al_xZn_1-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(Fe _1-xCo_x)₂Zn₂₀ (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.