On the Origin of the Positive Curie–Weiss Temperature in Ferrimagnetic GdTiO3

Abstract Recent investigations into the magnetic properties of high-quality GdTiO3 single crystals have reported an isotropic ferrimagnetic ordering at TN ≈ 32 K, accompanied by a positive Curie–Weiss temperature (θCW ≈ 34–35 K) in the paramagnetic regime. The original study interpreted this positive θCW as arising from antiferromagnetic interactions between the Gd and Ti magnetic sublattices, together with ferromagnetic interactions within the individual sublattices. Here we reassess this interpretation within the Néel molecular-field theory for two-sublattice ferrimagnets. The analysis shows that an antiferromagnetic inter-sublattice coupling gives a negative contribution to the asymptotic Curie–Weiss temperature. Therefore, the observed positive θCW requires a dominant positive intra-sublattice contribution. Because the Curie constant of the Gd3+ sublattice is about 21 times larger than that of the Ti3+ sublattice, the high-temperature susceptibility is expected to be governed mainly by ferromagnetic Gd–Gd correlations, whereas the antiferromagnetic Gd‒Ti coupling determines the antiparallel locking of the two sublattices in the ferrimagnetic state.