SPIN FLUCTUATIONS AND MAGNETIC ORDER IN NB1-XZRXFE2

Zero and longitudinal field muSR have been used to study the evolution of spin correlations and magnetic order resulting from 10at% substitution of Zr for Nb in the weak itinerant antiferromagnet NbFe2. Rapidly fluctuating atomic fields (lambda=0.02mus-1) are found to persist almost unchanged to low temperatures. These coexist with a narrow distribution of static fields (sigma=0.2mus-1) which evolves from a gaussian to lorentzian form between 90K and the Curie temperature of 43K. It is suggested that these effects may be a consequence of topologically frustrated exchange between Fe sites in the C14 structure.