In this work, we systematically report the synthesis, structure, and magnetism of a compound of filled
anti-Mn3Si5 type La3MnAs5. It crystallizes in a hexagonal structure with the space group of P63/mcm (193).
The structure consists of face-sharing MnAs6 octahedral chains along the c axis, which are well separated by a
large distance of 8.9913 Å, demonstrating a strong one-dimensional (1D) structural character. Physical property
measurements indicate that La3MnAs5 is a ferromagnetic metal with TC ∼ 112 K. Due to the short-range
intrachain spin coupling, the susceptibility deviates from the Curie-Weiss behavior in a wide temperature
window and the magnetic entropy corresponding to the ferromagnetic transition is significantly lower than that
expected from the fully saturated state. The magnetic critical behavior studies show that La3MnAs5 can be
described by the three-dimensional Heisenberg model. The orbital hybridization between the 1D MnAs6 chain
and intermediate La atom near the Fermi level reveals that the itinerant electrons play a key role in transmitting
spin interaction among the MnAs6 spin chains. Our results indicate that La3MnAs5 is a rare ferromagnetic metal
with well-separated spin chains, which provides a good opportunity to study the mechanism of interchain spin
coupling via itinerant electrons
