Magnetic order of Mn5Si3-type Tb5Sb3 and Tb5Si1.5Sb1.5

Neutron diffraction study has been performed on the Tb5Sb3 and Tb5Si1.5Sb1.5 compounds (hexagonal Mn5Si3-type, hP16, P63/mcm) to understand their magnetic structures. The temperature dependence of neutron diffraction results proves that these intermetallics show a complex magnetic ordering. The Tb5Sb3 presents five subsequent changes in magnetic structure at ∼150, 119, 85, 70 and 54 K on cooling: paramagnet→antiferromagnetic flat spiral→ferromagnetic cone→antiferromagnetically canted ferromagnetic cone→canted AF→sine modulated AF. The Tb5Si1.5Sb1.5 shows two subsequent changes in magnetic structure at 123 and 66 K: paramagnet→sine modulated antiferromagnet I→sine modulated antiferromagnet II. The Tb5Si3, Tb5Sb3 and Tb5Si1.5Sb1.5 have the different magnetic structure in the full temperature range.

► Nature of p-element sublattice in Mn5Si3-type rare earth intermetallics determines the interatomic distances of Tb sublattice.
► The magnetic symmetry of Tb5Si1.5Sb1.5 is higher than the one of Tb5Si3 and Tb5Sb3.
► Magnetic structures of Tb5Si3 and Tb5Sb3 sensitive to internal magnetic field.
► Whereas magnetic structure of Tb5Si1.5Sb1.5 should not be sensitive to one.