Effect of composition and short-range order on the magnetic moments of Fe in Fe/sub 1-x/V/sub x/ alloys

Abstract

We report dc magnetization, Mössbauer spectroscopy, and x-ray-diffraction measurements on Fe₁₋xVx alloys, quenched or heat treated, with single phase bcc structure in the whole concetration range. It is well known that the saturation magnetization of these alloys decreases when the vanadium concentration increases and vanishes completely for x≥0.7. We find a very large additional decrease of the saturation magnetization and hyperfine splitting after heat treatments, which preserve the pure bcc structure. Our data, however, exclude the presence of an appreciable amount of paramagnetic phase and of magnetic disorder. The Mössbauer spectra also gave account of a regular sequence of hyperfine fields, in accord with previous NMR and Mössbauer works, whose relative weights, in the case of splat-cooled samples, approximate the values predicted by the binomial distribution. While a moderate decrease of the iron moment in the neighborhood of V impurities in dilute FeV alloys has been evidenced by neutron diffuse scattering, our experimental data of concentrated alloys indicate a literal suppression in heat treated samples above 40 at.% V and the predominance of Pauli spin paramagnetism in samples above 80 at.% V. The suppression of the iron moments is discussed within the scenario of Stoner’s band ferromagnetism using the electronic structure calculated by the discrete variational method.