100mK 4-Circle Dilution

N. Belkhier, Ph. Decarpentrie, J. Gonthier, E. Lelièvre-Berna, P. Martin, B. Ouladdiaf, X. Tonon
Institut Laue Langevin, 71 Avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France
Ph. Camus, G. Donnier-Valentin, G. Garde, Y. Launay, O. Tissot
Institut Néel, CNRS, 25 Avenue des Martyrs, BP 156, 38042 Grenoble Cedex 9, France

The full determination of magnetic ground states is a key point in understanding the fundamental properties of magnetic materials. The measurement of the magnetic structure factors requires access to the three dimensions of reciprocal space using single-crystal four-circle geometry.

A four-circle dilution cryostat that avoids the influence of gravity by using a capillary dilution chamber was developed [1,2] for experiments below 2 K. This system, where the sample was cooled down to 110 mK by a gravity-insensitive dilution refrigerator, was successfully used on D10 for several years.

However, it did present certain disadvantages: autonomy was limited to several hours, the re-distillation of the 3He was done off-site, and temperature stability was difficult to maintain when rotating the phi shaft. To overcome these difficulties, a closed-cycle dilution cryostat providing four-circle diffraction accessibility has been developed and commissioned successfully on D10.

[1] A. Benoît and S. Pujol, Physica B 169 (1991) 457 
[2] A. Benoît, M. Caussignac, and S. Pujol, Physica B 197 (1994) 48