Flipping magnetization induced by noncollinear ferromagnetic-antiferromagnetic exchange coupling.

We present a direct observation of a flipping magnetization of a uniform Fe film/wedged-Mn bilayer induced by a biquadratic-type exchange coupling established at the interface. The element-resolved magnetic imaging shows that the Fe film exhibited a flipping of magnetization between the [&1horbar00] and [010] directions with a periodicity of one monolayer Mn thickness as below a critical temperature. The enhancement of the variation angle with the increase of Mn thickness follows the tendency of the finite-size effect of antiferromagnetism on interface exchange coupling. The flipping magnetization emerging coincidentally with the uncompensated-compensated transition of Mn magnetic surface indicates a frustration-induced biquadratic-type interface exchange coupling, and suggests a layered-like uncompensated AFM ordering for the Mn layer. [ABSTRACT FROM AUTHOR]