Speaker
Description
We present a systematic classification of the magnetic ground states in hundreds of two-dimensional (2D) materials. Non-collinear order is shown to be abundant and may typically be represented by planar spin spiral ground states. We discuss a range of physical effects associated with non-collinear order and take specific materials as examples. The Ni(Cl,Br,I)$_2$ compounds exhibit type II multiferroic order where the spontaneous polarization is induced by spiral order and we discuss the subtleties associated with the calculation of the polarization from first principles. The breathing Kagomé compounds Nb$_3$(Cl,Br,I)$_8$ are pyroelectric and have spiral ground states with ordering vectors that couple strongly to out-of-plane external electric fields. Finally we discuss a set of 2D altermagnets and analyse the important role of spin-orbit coupling with respect to the band structure, magnons and non-collinearity.
