Noncollinear Exchange Coupling Research Articles

Noncollinear interlayer exchange coupling caused by interface spin-orbit interaction

The interlayer exchange couplings between neighboring ferromagnetic layers in ferromagnetic-nonmagnetic multilayer structures are derived analytically in the frame of the extended Anderson s-d mixing model with spin-orbit interaction. After transforming the extended Anderson mixing model into an s-d exchange model and taking into account the spin frustration at interfaces, the second-order perturbation calculation naturally gives rise to both the noncollinear Dzyaloshinski-Moriya (DM) exchange coupling as well as the usual isotropic Ruderman-Kittel-Kasuya-Yosida exchange coupling between the neighboring ferromagnetic layers. The isotropic and anisotropic exchange couplings have a decaying oscillatory behavior as a function of spacer layer thickness, but they differ by a phase factor of \ensuremath{\pi}/2. While the exact value of the DM coupling depends on the material parameters as well as the interface s-d mixing effect, a rough estimate suggests that it is significant. Thus our result offers an alternative explanation to the noncollinear exchange coupling as was observed in the experiments.

Correlation between non-collinear exchange coupling and interface structure in Fe/Cr(001) superlattices

Using polarized neutron reflectometry with polarization analysis we have studied the non-collinear interlayer exchange coupling in Fe/Cr(0 0 1) superlattices as a function of growth temperature. From diffuse X-ray spectra we find that the occurence of non-collinear spin structures is correlated with long range lateral Cr-thickness fluctuations which, in turn, depend on the growth temperature. This finding leads the way to a better understanding of the origin of non-collinear coupling in Fe/Cr(0 0 1).

Direct observation of a non-collinear 50°-coupled magnetization profile in a Fe/Cr(001) superlattice

Using spin polarized neutron reflectometry on molecular beam epitaxy-grown Fe/Cr(001) superlattices we have studied the noncollinear exchange coupling of the Fe layers over the Cr spacers. A surprisingly strong exchange coupling and a non-collinear coupling angle of 50° were discovered.