Interplay of itinerant magnetism and spin-glass behavior in FexCr1−x

When suppressing the itinerant antiferromagnetism in chromium by doping with the isostructural itinerant ferromagnet iron, a dome of spin-glass behavior emerges around a putative quantum critical point at an iron concentration $x\ensuremath{\approx}0.15$. Here, we report a comprehensive investigation of polycrystalline samples of ${\mathrm{Fe}}_{x}{\mathrm{Cr}}_{1\ensuremath{-}x}$ in the range $0.05\ensuremath{\le}x\ensuremath{\le}0.30$ using x-ray powder diffraction, magnetization, ac susceptibility, and neutron depolarization measurements, complemented by specific heat and electrical resistivity data for $x=0.15$. Besides antiferromagnetic $(x<0.15)$ and ferromagnetic regimes $(x\ensuremath{\ge}0.15)$, we identify a dome of spin-glass behavior at low temperatures for $0.10\ensuremath{\le}x\ensuremath{\le}0.25$. Neutron depolarization measurements indicate an increase of the size of ferromagnetic clusters with increasing $x$ and the Mydosh parameter $\ensuremath{\phi}$, inferred from the ac susceptibility, implies a crossover from cluster-glass to superparamagnetic behavior. Taken together, these findings consistently identify ${\mathrm{Fe}}_{x}{\mathrm{Cr}}_{1\ensuremath{-}x}$ as an itinerant-electron system that permits to study the evolution of spin-glass behavior of gradually varying character in an unchanged crystalline environment.