Influence of interstitial Mn on magnetism in the room-temperature ferromagnetMn1+δSb

Abstract

We report elastic and inelastic neutron-scattering measurements of the high-${T}_{\mathrm{C}}$ ferromagnet ${\mathrm{Mn}}_{1+\ensuremath{\delta}}\mathrm{Sb}$. Measurements were performed on a large, ${T}_{\mathrm{C}}=434$ K, single crystal with an interstitial Mn content of $\ensuremath{\delta}\ensuremath{\approx}0.13$. The neutron-diffraction results reveal that the interstitial Mn has a magnetic moment, and that it is aligned antiparallel to the main Mn moment. We perform density functional theory calculations including the interstitial Mn and find the interstitial to be magnetic, in agreement with the diffraction data. The inelastic neutron-scattering measurements reveal two features in the magnetic dynamics: (i) a spin-wave-like dispersion emanating from ferromagnetic Bragg positions $(\mathrm{H}\phantom{\rule{4pt}{0ex}}\mathrm{K}\phantom{\rule{0.16em}{0ex}}2n)$, and (ii) a broad, nondispersive signal centered at forbidden Bragg positions $(\mathrm{H}\phantom{\rule{4pt}{0ex}}\mathrm{K}\phantom{\rule{0.16em}{0ex}}2n+1)$. The inelastic spectrum cannot be modeled by simple linear spin-wave-theory calculations and appears to be significantly altered by the presence of the interstitial Mn ions. The results show that the influence of the interstitial Mn on the magnetic state in this system is more important than previously understood.