Magnetic properties of RFe$_2$Zn$_{20}$ (R = Y, Gd - Lu): $4f$ moments embedded in strongly correlated electron host

The RFe$_2$Zn$_{20}$ series of compounds manifest varied magnetic properties, from near ferromagnetism (R = Y, Lu), to enhanced ferromagnetic (FM) ordering of local moments (R = Gd to Tm), to heavy Fermi ground state (R = Yb). Thermodynamic and transport measurement results reveal that these varied magnetic states can be understood in the framework of $4f$ moments embedded in a nearly ferromagnetic Fermi liquid. In such a highly polarizable electronic host, the different type of 4f moments, null moments for Y$^{3+}$ and Lu$^{3+}$, pure spin- contributed Gd$^{3+}$, spin-orbital-coupling contributed Tb$^ {3+}$ to Tm$^{3+}$, and the hybridized Yb ions, correlated with the itinerant electrons, lead to this magnetic versatility. For local moment members (R = Gd to Tm), the Curie temperatures roughly scale with the de Gennes parameter, indicating negligible crystal electric field (CEF) effect on the magnetic ordering, although the CEF on the $4f$ local moments leads to anisotropic FM ground state for R = Tb to Tm. For hybridized moment member (R = Yb), the Kondo temperature seems to be enhanced, associated with the electronic host.