Elemental substitution effects in multiferroic R Fe₂O₄ (R: Rare earths)

We report the effects of elemental substitutions in multiferroic R Fe₂O₄ (R: Y, Ho-Lu, In). The substitution by nonmagnetic Ga³⁺ at the Fe site, which has not been reported so far, shows a drastic decrease in the ferrimagnetic transition temperature (T_N). This is plausibly owing to the suppression of magnetic interactions between Fe ions, based on our previous results of other substituted systems such as R FeCoO₄. Dielectric constants near room temperature were comparable to those of R Fe₂O₄. The suppression of dielectric loss in this system is suitable to application. The R -site substitution was also attempted by the large R³⁺ ions such as Dy³⁺. The solubility limit was up to ~10% of R ions. T_N was raised by 5-10 K for Dy³⁺ substitution.