G. Helgesen

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Featured researches published by G. Helgesen.

Physica B-condensed Matter | 1996

P. M. Gehring; A Vigliante; D.F. McMorrow; Doon Gibbs; Charles F. Majkrzak; G. Helgesen; R. A. Cowley; R. C. C. Ward; M.R. Wells

Abstract Two-axis neutron-scattering measurements on a 1 μm thick holmium film reveal the presence of two magnetic correlation lengths above T N that are qualitatively similar to those recently observed in X-ray and neutron scattering studies of bulk holmium and terbium. The scattering profile is well described by a broad Lorentzian plus a narrow Lorentzian-squared line-shape with widths that, for temperatures sufficiently close to T N , differ by a factor often or more.

Journal of Magnetism and Magnetic Materials | 1995

N. Bernhoeft; A. Stunault; C. Vettier; F. de Bergevin; Doon Gibbs; T.R. Thurston; S. M. Shapiro; J. B. Hastings; P. Dalmas; G. Helgesen; O. Vogt

Abstract Resonant magnetic X-ray scattering from UAs using the Miv uranium absorption edge allows a detailed examination of the first order antiferromagnetic phase transition occuring at 122 K which appears to proceed via the formation of antiferromagnetically coupled surface layers.

Physica B-condensed Matter | 1993

T.R. Thurston; G. Helgesen; Jonathan P. Hill; Doon Gibbs; B. D. Gaulin; G. Shirane

We describe measurements of the magnetic critical fluctuations of holmium by x-ray scattering techniques. The x-ray results are compared to those obtained in neutron scattering experiments performed on the same sample.

Physical Review B | 1995