Variation of the magnetic ordering inGdT2Zn20(T=Fe, Ru, Os, Co, Rh and Ir) and its correlation with the electronic structure of isostructuralYT2Zn20

Magnetization, resistivity, and specific heat measurements were performed on solution-grown single crystals of six $\text{Gd}{T}_{2}{\text{Zn}}_{20}$ ($T=\text{Fe}$, Ru, Os, Co, Rh, and Ir) compounds, as well as on their Y analogs. For the Gd compounds, the Fe column members manifest a ferromagnetic (FM) ground state (with an enhanced Curie temperature ${T}_{C}$ for $T=\text{Fe}$ and Ru), whereas the Co column members manifest an antiferromagnetic (AFM) ground state. Thermodynamic measurements on $\text{Y}{T}_{2}{\text{Zn}}_{20}$ revealed that the enhanced ${T}_{C}$ for ${\text{GdFe}}_{2}{\text{Zn}}_{20}$ and ${\text{GdRu}}_{2}{\text{Zn}}_{20}$ can be understood within the framework of Heisenberg moments embedded in a nearly ferromagnetic Fermi liquid. Furthermore, electronic structure calculations indicate that this significant enhancement is due to a large transition metal partial density of states at the Fermi level that places these compounds close to the Stoner FM criterion. The change from FM to AFM ordering (between the Fe and Co column materials) is associated with the filling of electronic states with two additional electrons/f.u. The degree of this sensitivity is addressed by the studies of the pseudoternary compounds $\text{Gd}{({\text{Fe}}_{x}{\text{Co}}_{1\ensuremath{-}x})}_{2}{\text{Zn}}_{20}$ and $\text{Y}{({\text{Fe}}_{x}{\text{Co}}_{1\ensuremath{-}x})}_{2}{\text{Zn}}_{20}$, which clearly reveal the effect of $3d$-band filling on their magnetic properties.