  Honeycomb or triangular lattices were extensively studied and thought to be
proper platforms for realizing quantum anomalous Hall effect (QAHE), where
magnetism is usually caused by d orbitals of transition metals. Here we propose
that square lattice can host three magnetic topological states, including the
fully spin polarized nodal loop semimetal, QAHE and topologically trivial
ferromagnetic semiconductor, in terms of the symmetry and k$\cdot$p model
analyses that are materials-independent. A phase diagram is presented. We
further show that the above three magnetic topological states can be indeed
implemented in two-dimensional (2D) materials ScLiCl5, LiScZ5 (Z=Cl, Br), and
ScLiBr5, respectively. The ferromagnetism in these 2D materials is
microscopically revealed from p electrons of halogen atoms. This present study
opens a door to explore the exotic topological states as well as quantum
magnetism from p-orbital electrons by means of the materials-independent
approach.
