[Zurück]

V. Paul-Boncour, M. Guillot, G. André, F. Bourée, G. Wiesinger, A. Percheron-Guégan:
"Origin of the first order magnetostructural transition in YFe₂D_4.2";
Journal of Alloys and Compounds, 404-406 (2005), S. 355 - 359.

Origin of the first order magnetostructural transition in YFe₂D_4.2

V. Paul-Boncour a, M. Guillot b, G. André c, F. Bourée c, G. Wiesinger d and A. Percheron-Guégan a

a LCMTR, CNRS, 2-8 rue Henri Dunant, 94320 Thiais Cedex, France
b LCMI, CNRS-MPI, BP166, 38042 Grenoble Cedex 9, France
c LLB, CE-Saclay, 91191 Gif/Yvette, France
d IFP, T.U. Wien,Wiedner Haupstrasse 8-10, 1040 Vienna, Austria

Received 6 September 2004; accepted 5 October 2004. Available online 7 July 2005.

Abstract

The deuterium order-disorder and the first order magnetic transitions in YFe₂D_4.2 have been studied by X-ray and neutron diffraction, magnetization measurements and ⁵⁷Fe Mössbauer spectroscopy. From 363 down to 290 K, a progressive lowering of the crystal symmetry from cubic to rhombohedral and then monoclinic structure is observed. At 290 K YFe₂D_4.2 crystallizes in a primitive monoclinic space group P1c with a=9.429(1) Angstrom capital A, ring, b=11.474(1) Angstrom capital A, ring, c=5.508(1) Angstrom capital A, ring, β=122.37°. This lowering of crystal symmetry leads to very different quantity of D neighbours around each Fe sites. The magnetic study shows that the moment of the Fe3 atoms, surrounded by nearly 5 D atoms, collapses at 84 K, leading to a transition from a ferromagnetic to an antiferromagnetic structure. The first order transition at 84 K is associated with a 0.55% volume decrease and the magnetization curves above 84 K display the same behaviour than the collective electron metamagnetism (CEM) observed in RCo2 compounds. This is related to the fact that for critical deuterium content between 4 and 5 D atoms in YFe₂ the Fe 3d ferromagnetism becomes instable due to a strong modification of the electronic band structure.

Keywords: Hydrogen storage materials; X-ray diffraction; Neutron diffraction; Magnetic measurements; Mössbauer spectroscopy

doi:10.1016/j.jallcom.2004.10.083

http://aleph.ub.tuwien.ac.at/F?base=tuw01&func=find-c&ccl_term=AC05938079

http://dx.doi.org/10.1016/j.jallcom.2004.10.083