High field magnetic measurements on FexGe1-xamorphous alloys

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Abstract
Magnetic measurements and Mossbauer spectrometry under magnetic field have been performed on amorphous FexGe1-x alloys of various compositions. For x=0.35, no ferromagnetic ordering is observed down to 1.6K. For x=0.45 and x=0.55, magnetic order exists at 4.2K. From the hyperfine field distribution measured by Mossbauer spectrometry, the distributions of magnetic moments born by the Fe atoms has been calculated, as well as the value of saturation magnetisation expected for colinear spin structure. Fair agreement is obtained between these calculated values and the experimental ones measured directly by an extraction method. The very large widths of the distributions are attributed to hybridisation effects between the d orbitals of iron and the sp orbitals of germanium, whose effect on the magnetic moment of a given iron atom depends on its variety of near neighbour environments. A large number of near neighbour Ge atoms will widen the d levels of the iron atom and make it either non-magnetic or weakly magnetic; on decreasing the number of Ge neighbours the d levels get narrower and higher values of localised moments are obtained.

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