Magnetic correlations in Nb 1-y Fe 2+y

The evolution of spin correlations with temperature in the ferromagnetic C14 Laves-phase compound Nb1-yFe2+y with y=-0.03 and 0.01 has been studied by small-angle neutron scattering. The Q-dependence of the scattering is squared-Lorentzian in form for y=-0.03 but is predominantly Lorentzian for y=0.01. The magnetic correlation range remains close to 30 A, showing no evidence of any critical divergence at the reported Curie points (TC∼20 K) of the respective compounds.