Magnetic short-range order in Gd

The magnetic short-range order in a ferromagnetic, isotopically enriched ¹⁶⁰Gd metal single crystal has been investigated by quasielastic scattering of 81-meV neutrons. Since Gd behaves as an S-state ion in the metal, little anisotropy is expected in its magnetic behavior. However, the data show that there is anisotropic short-range order present over a large temperature interval both above and below T_C. The data have been analyzed in terms of an Ornstein-Zernike Lorentzian form with anisotropic correlation ranges. These correlation ranges as deduced from the observed data behave normally above T_C but seem to remain constant over a fairly large interval below T_C before becoming unobservable at lower temperatures. These observations suggest that the magnetic ordering in Gd may be a more complicated phenomenon than first believed.