We have investigated single crystals and polycrystals from the series ${\mathrm{Nb}}_{1-y}{\mathrm{Fe}}_{2+y}, -0.004\le y\le 0.018$, by electron spin resonance, muon spin relaxation, and Mössbauer spectroscopy. Our data establish that at lowest temperatures all samples exhibit bulk magnetic order. Slight Fe excess induces low-moment ferromagnetism, consistent with bulk magnetometry, while Nb-rich and stoichiometric ${\mathrm{NbFe}}_2$ display spin density wave order with small magnetic moment amplitudes of order $\sim 0.001–0.01{\mu }_B/\mathrm{Fe}$. This provides microscopic evidence for a modulated magnetic state on the border of ferromagnetism in ${\mathrm{NbFe}}_2$.

• Received 28 February 2014
• Revised 14 April 2015

DOI:https://doi.org/10.1103/PhysRevB.91.174404