STRUCTURAL AND MAGNETIC-ANISOTROPY IN AMORPHOUS ALLOY RIBBONS

We report x-ray, EXAFS and neutron diffraction experiments on stress-r elieved (SR) and field-annealed (FA) ribbons of Fe78Si9B13 using optim ized geometries to measure the structural and magnetic anisotropy to u nprecedented accuracy. A peak of magnitude similar to 5% of the main p eak height is found in the Delta S(Q) pattern from three independent n eutron experiments on the FA ribbons, at Q similar to 3 Angstrom(-1). We establish that this peak is of magnetic origin, arising from moment s that to some extent lie perpendicularly to the anneal field directio n, and is associated with local structure. We show that this anistropy is consistent with a recently proposed disturbed exchange model, sugg esting that the result represents the first direct observation of the existence of antiferromagnetically coupled moments within an amorphous ferromagnetic alloy.