NIST PROVIDES INSIGHT INTO MAGNETIC COUPLING THROUGH ANTIFERROMAGNETS.

The study of the magnetic coupling between two ferromagnetic films separated by a non-ferromagnetic metallic spacer has been an extremely active and fruitful area of research over the last decade. The interlayer exchange coupling that causes the magnetization of the two ferromagnetic layers to be parallel or antiparallel to each other, depending on the thickness of the spacer, is now well understood when the spacer is a diamagnetic or paramagnetic metal. However, when the spacer layer is an antiferromagnet, such as manganese (Mn), the observed coupling is non-collinear.

In a paper soon to appear in the Journal of Magnetism and Magnetic Materials, researchers at NIST report scanning tunneling microscopy (STM) measurements of the growth of Mn on nearly perfect iron (Fe) single-crystal whisker surfaces to determine the thickness distribution of the Mn layer for particular growth conditions. The coupling angles measured for Fe/Mn/Fe(001) tri-layers, using scanning electron microscopy with polarization analysis (SEMPA), were in approximate agreement with the predictions of the so-called torsion model, developed to describe the more complicated interlayer coupling when exchange coupling within the antiferromagnetic spacer is important. STM measurements of the lateral scale of the Mn thickness distribution provide insight into ways to go beyond the torsion model to obtain a better explanation of the SEMPA results.