Structural effects at the ferromagnetic to antiferromagnetic phase transition in Ce(Fe1-xCox)2

Following the recent discovery of a new magnetic phase transition in the Ce(Fe1-xCox)2 compounds for which x<0.3, the authors report the results of a neutron powder diffraction study on a compound with x=0.20 using HRPD at the Rutherford Appleton Laboratories. Rietveld structure refinements show that the ferromagnetic phase is the cubic Laves phase ( alpha =90 degrees ), but the low-temperature antiferromagnetic phase below TN approximately=85 K is distorted to rhombohedral symmetry with alpha =90.20+or-0.01 degrees at 18 K. This distortion coincides with a discontinuity in cell volume at TN.