Spectroscopic study of the magnetic ground state of Nb${}_{1-y}$Fe${}_{2+y}$

Abstract

We have investigated single crystals and polycrystals from the series Nb${}_{1-y}$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 ($\simeq 0.06\hat{I}{¼}_B/\mathrm{Fe}$), Nb--rich and stoichiometric NbFe${}_2$ display spin density wave order with small magnetic moment amplitudes of the order $\sim 0.001-0.01\hat{I}{¼}_B/\mathrm{Fe}$. This provides microscopic evidence for a modulated magnetic state on the border of ferromagnetism in NbFe${}_2$.

7 pages, 9 figures