Spin patterns and phase diagrams of few (111)-monolayer EuTe including shape anisotropy

Abstract EuTe is a typical representative of the Heisenberg model, showing type-II antiferromagnetic ordering. In few monolayer samples grown by molecular-beam epitaxy, shape anisotropy plays a key role for magnetic ordering, especially in odd-layered systems which show drastically different phase diagrams for in-plane and perpendicular fields due to the remaining net magnetic moment in zero external field. Using a variational mean-field method based on the Bogoliubov-inequality, we show that the spin–flop like phases for either field directions are of completely different nature, treating a three-layer system as an example. The perpendicular spin–flop phase turns out to be a mixture between the conventional (isotropic) spin–flop and a novel tilted antiferromagnetic phase appearing only for low anisotropy.