Local moments and suppression of antiferromagnetism in correlated Zr ⁴Fe⁴Si⁷

We report magnetic, transport, and neutron diffraction measurements as well as a doping study of the V-phase compound Zr⁴Fe⁴Si ⁷. This compound exhibits collinear antiferromagnetic order below T_N=98±1 K with a staggered moment of 0.57(3)μ_B/ Fe as T→ 0. The magnetic order can be quenched with Co substitution to the Fe site, but even then a 1.5μ_B/Fe paramagnetic moment remains. The resistivity and heat capacity of Zr⁴Fe⁴Si⁷ are Fermi-liquid-like below 16 and 7 K, respectively, and reveal correlations on the scale of those observed in superconducting Fe pnictides and chalcogenides. Electronic structure calculations overestimate the ordered moment, suggesting the importance of dynamical effects. The existence of magnetic order, electronic correlations, and spin fluctuations make Zr⁴Fe⁴Si ⁷ distinct from the majority of Fe-Si compounds, fostering comparison instead with the parent compounds of Fe-based superconductors.