Static magnetization of polycrystalline nickel spheres (diameter about 0.3 cm) has been studied in detail as a function of the magnetic field above and below the Curie point, T , , using a vibrating sample magnetometer. Above T, the initial magnetic susceptibility is

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Body-centered tetragonal VF2 has a transition temperature at 7°K to a spiral structure in which the spins are perpendicular to the c axis and spiral along this axis with a turn angle of 96 deg/layer.'Magnetic correlations which persist to high temperatures have been interpreted 2 as evidence for relatively strong interactions between V+2 ions spaced along the c axis but weak interactions between these chains. We have measured the magnetic incoherent neutron scattering from VF 2 powder and find that significant magnetic correlations persist to temperatures about 25 times the Neel temperature. Least-squares fitting of the data to a general formula for magnetic short-range order scattering was used to determine the correlation coefficients as a function of temperature. A model assuming uniaxial magnetic correlations fits the data over the temperature range studied but allowing some correlations between different chains could perhaps improve the fit at very low temperatures. Thus, VF 2 appears to exhibit properties characteristic of one-dimensional ordering.

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