Competition between magnetism and superconductivity in Eu-based intermetallic compounds

Eu-based intermetallic compounds present a path to discover new correlated electronic behavior in quantum materials. Reports of superconductivity, intermediate valence behavior, and heavy fermions indicate that Eu-based compounds are promising routes to study the relationship between crystallography and electronic properties. The present work is focused on EuGa$_4$, an antiferromagnet with T$_N$ = 16 K isostructural with the tetragonal RT$_2$M$_2$ (R = rare earth, T = transition metal, M = metal or metalloid) family that exhibits heavy fermion behavior and unconventional superconductivity. Single crystals of the doped series (Eu$_{1-x}$La$_x$)Ga$_4$, (Eu$_{1-x}$Ca$_x$)Ga$_4$, and Eu(Ga$_{1-x}$Al$_x$)$_4$ have been grown using the self-flux method and tested for change in unit cell volume and magnetic susceptibility. Results show that doping with Ca (isoelectronic doping) and La (hole doping) reduce T$_N$ to 12.4 K and 2.3 K, respectively, for Ca doping up to x = 0.11 and La doping up to x = 0.74 without an associated change in unit cell volume. The series Eu(Ga$_{1-x}$Al$_x$)$_4$ has shown incommensurate-to-commensurate magnetic transitions. Future studies will aim to further decrease T$_N$ and the unit cell volume using physical pressure and chemical pressure through doping.