Magnetic behaviour of the MTbF6 fluoroterbates (M=Cd, Ca, Sr, (α/β)-Ba)

► Five fluoroterbates are investigated by Powder Neutron Diffraction (PND). ► Four of them are antiferromagnetically ordered at 1.4 K. ► Magnetic structures of β-BaTbF6 and CdTbF6 are determined. ► PND under magnetic field emphasises the metamagnetic behaviour of β-BaTbF6. ► Comparison of α and β-BaTbF6 evidences superexchange interactions in fluoroterbates.