The Effect of $ f$–$d$ Magnetic Coupling in Multiferroic $R$MnO3 Crystals

概要

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We have established detailed magnetoelectric phase diagrams of (Eu0.595Y0.405)1-xTbxMnO3 ($0\leq x\leq 1$) and (Eu,Y)1-xGdxMnO3 ($0\leq x\leq 0.69$), whose average ionic radii of $R$-site ($R$: rare earth) cations are equal to that of Tb3+, in order to reveal the effect of rare earth 4f magnetic moments on the magnetoelectric properties. In spite of the same $R$-site ionic radii, the magnetoelectric properties of the two systems are remarkably different from each other. A small amount of Tb substitution on $R$ sites ($x\sim 0.2$) totally destroys ferroelectric polarization along the $a$-axis ($P_{a}$), and an increase in Tb concentration stabilizes the $P_{c}$ phase. On the other hand, Gd substitution ($x\sim 0.2$) extinguishes the $P_{c}$ phase, and slightly suppresses the $P_{a}$ phase. These results demonstrate that the magnetoelectric properties of $R$MnO3 strongly depend on the characteristics of the rare earth 4f moments.
2010-05-15