  Within the same failure mode, iron has the lowest ideal tensile strength
among the transition metals crystallizing in the body-centered cubic structure.
Here, we demonstrate that this anomalously low strength of Fe originates partly
from magnetism and is reflected in unexpected alloying effects in dilute
Fe(\emph{M}) (\emph{M} = Al, V, Cr, Mn, Co, Ni) binaries. We employ the
structural energy difference and the magnetic pressure to disentangle the
magnetic effect on the ideal tensile strength from the chemical effect. We find
that the investigated solutes strongly alter the magnetic response of the Fe
host from the weak towards a stronger ferromagnetic behavior, which is
explained based on single-particle band energies.
