Transitions induced by a magnetic field in slightly doped TbMnO3

• We replace Mn by different cations in the multiferroic TbMnO3.
• We monitor the effects of substitution in macroscopic properties.
• We determine the magnetic ground state of the doped compounds.
• We identify metamagnetic transitions in the Tb sublattice.
• We model the magnetic ordering at high magnetic fields.

We have investigated the magnetic properties of slightly doped multiferroic TbMnO3 after application of a magnetic field. The study focused on compositions TbMn1−xAxO3 (x ≤ 0.1) with A = Ga, Sc, Co and Al. The replacement of Mn by Ga, Al or Sc proved to be isovalent while the addition of Co leads to a partial charge transfer as Mn3+ + Co3+ → Mn4+ + Co2+. The samples with 10% of non-magnetic doping, TbMn0.9Sc0.1O3, TbMn0.9Al0.1O3 and TbMn0.9Ga0.1O3, preserve the long range antiferromagnetic ordering of the Mn sublattice with, however, reduced transition temperatures compared to TbMnO3. New magnetic interactions in the Co-doped compound lead to the suppression of Mn ordering in TbMn0.9Co0.1O3. The application of an external magnetic field produces similar metamagnetic transitions in all TbMn0.9A0.1O3 compounds that are ascribed to the Tb-sublattice. Powder neutron diffraction was used to determine the changes in the magnetic structure with applied magnetic field revealing a strong increase of F- and C-type magnetic reflections in these compounds. These results are accounted for by the anisotropic response of the Tb sublattice to a magnetic field while the Mn sublattice remains unchanged.

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