A polarised neutron diffraction study of the field-induced magnetisation density in vanadium metal

The magnetisation density in vanadium metal induced by an applied field of 4.6 T at 100K has been measured using the polarised neutron technique. The authors have also measured the nuclear scattering length of vanadium in their crystal by making absolute measurements of the integrated intensity of reflection of unpolarised neutrons. These yield a value of -0.0446(9)*10 -12 cm for the scattering length of vanadium, and indicate the presence of interstitial impurities giving a scattering length of 0.0010(1)*10 -12 cm per interstitial site of the type (0, 0, 1 / 2 ). The magnetisation density has been fitted to a simple model based on the vanadium 3d 3 4s 2 free-atom form factor. Coefficients giving the amounts of spin and orbital moment and the degree of asphericity were determined. The density is nearly spherical with respect to the vanadium sites and appears to be almost completely orbital in character. This latter result, which is at variance with gyromagnetic measurements, probably indicates a contraction of the radial wavefunction of states near the Fermi surface. The fit also suggests that about 20% of the magnetic moment does not contribute to the scattering at finite angles.