• Ferromagnetic CrBr₃ (T_c = 37 K)
  Tsubokawa, J. Phys. Soc. Jpn. 15, 1664 (1960)
  structure: bayerite (rare and complicated)

• Stoichiometric Eu chalcogenides (1963)
  EuO: ferromagnet (T_c= 77 K)
  EuS: ferromagnet (T_c = 16.5 K)
  EuSe: antiferro-/ferrimagnet
  EuTe: antiferromagnet

structure: NaCl
good realizations of Heisenberg models with
J₁ (nearest neighbor) and J₂ (NNN) relevant Mechanism: kinetic and Coulomb