Strong magnetoelastic effect in CeCo 1 − x Fe x Si as Néel order is suppressed

A very strong magnetoelastic effect in the ${\\mathrm{CeCo}}_{1\\ensuremath{-}x}{\\mathrm{Fe}}_{x}\\mathrm{Si}$ alloys is reported. The strength of the magnetostrictive effect can be tuned upon changing $x$. The moderate low-temperature linear magnetostriction observed at low Fe concentrations becomes very large $(\\frac{\\mathrm{\\ensuremath{\\Delta}}L}{L}\\left(16T,2K\\right)=\\phantom{\\rule{4pt}{0ex}}3\\ifmmode\\times\\else\\texttimes\\fi{}{10}^{\\ensuremath{-}3})$ around the critical concentration ${x}_{c}\\ensuremath{\\approx}0.23$ at which the long-range antiferromagnetic order vanishes. Upon increasing doping through the nonmagnetic region $(xg{x}_{c})$, the magnetostriction strength gradually weakens again. The interplay between magnetic order and the Kondo screening appears to cause an enhanced valence susceptibility slightly changing the Ce ions valence, ultimately triggering the large magnetostriction observed around the critical concentration. Previous studies of the evolution of the lattice parameters with $x$ as well as magnetization and x-ray absorption spectroscopy measurements support this hypothesis.