Ordered magnetic frustation. VIII: Crystal and magnetic structures of the pyrochlore form of FeF3 between 2.5 and 25 K from powder neutron diffraction. Comparison with the order varieties of FeF3

La nouvelle forme de FeF 3 de structure pyrochlore cubique est antiferromagnetique. Resolution des structures cristallines et magnetiques au-dessous de la temperature de Neel