Magnetic structure of bornite, Cu5FeS4

Neutron powder diffraction techniques have been used to investigate the magnetic structure of bornite, Cu 5 FeS 4 . Below the antiferromagnetic ordering temperature of 76 ± 2 K extra peaks appear in the diffraction pattern corresponding to magnetic ordering. The data are consistent with an antiferromagnetic alignment of iron atoms with moments of 4.4 ± 0.3 μ B on the iron sites proposed by Koto and Morimoto on the basis of X-ray measurements of the crystal structure. Mössbauer and neutron diffraction data suggest that the second magnetic phase transition at 8 K arises from a spin rotation. Since the magnetic structure gives only superexchange paths between iron atoms through two or more anions, it is difficult to understand why the Néel temperature is so high without invoking small moments on copper atoms