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Phase Transitions in Hoalga

Published online by Cambridge University Press:  21 February 2011

M. Doukoure ,
D. Gignoux  and
F. Sayetat
M. Doukoure
Affiliation:
Laboratoire Louis Néel,
D. Gignoux
Affiliation:
Laboratoire Louis Néel,
F. Sayetat
Affiliation:
Laboratoire de Cristallographie, C.N.R.S., 166 X, 38042 Grenoble Cedex, France
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Abstract

HoAlGa is hexagonal at room temperature. It undergoes two magnetic transitions succesively at TN = 32 K from a paramagnetic to a triangular antiferromagnetic state where the Ho moments lie in the basal plane and at Tt = 18 K in the course of which the moments rotate toward c giving rise to a colinear antiferromagnetic arrangement. X-ray experiments performed between 5 and 300 K allow to determine the crystal evolution through the two transitions. The hexagonal symmetry is not lowered through the transitions; this result is compatible with the observed magnetic groups. The thermal expansion curves show a very anisotropic behaviour of the lattice parameters. The “c” parameter shrinks below TN and this anomaly is to be related to the magnetic order. Along a, a positive thermal anomaly appears below 70 K and this can be interpreted by crystal field effects. Stability of magnetic structures is discussed with regard to exchange interactions and magnetocrystalline anisotropy.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 21: Symposium GREECE – Phase Transformations in Solids , 1983 , 201
Copyright
Copyright © Materials Research Society 1984

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References

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