A MAGNETIC-STRUCTURE INVESTIGATION OF TETRAGONAL (FE1-XCOX)(2)AS

The crystal and magnetic structures of tetragonal (Fe1-xCox)(2) As hav e been investigated using magnetization measurements, Mossbauer spectr oscopy and neutron powder diffraction. Mossbauer and magnetisation mea surements were performed on compositions with x = 0.05, 0.10 and 0.20, and neutron diffraction data were recorded on the composition x = 0.2 0 at 10, 180 and 295 K. Two magnetic phase transitions were found. One is from a paramagnetic to an antiferromagnetic state and the other at lower temperatures from an antiferromagnetic to a ferrimagnetic state . The crystal and magnetic structures were refined with the Rietveld m ethod, and two possible models to interpret the data are discussed.