Ga substitution as an effective variation of Mn-Tb coupling in multiferroic TbMnO3

TL;DR

This study investigates how substituting Ga for Mn in TbMnO3 affects magnetic interactions, revealing that Ga substitution reduces Mn-Mn exchange interactions and suppresses Tb-magnetic ordering, highlighting the importance of Mn-Tb coupling.

Contribution

It demonstrates that Ga substitution modifies Mn-Mn exchange interactions and significantly influences Tb-magnetic ordering, providing new insights into magnetic coupling in multiferroic TbMnO3.

Findings

Ga substitution decreases Mn-Néel temperature and exchange interactions.

Suppression of Tb-magnetic ordering with Ga substitution.

Mn-Tb exchange fields stabilize Tb-magnetic ground state.

Abstract

Ga for Mn substitution in multiferroic TbMnO$_{3}$ has been performed in order to study the influence of Mn-magnetic ordering on the Tb-magnetic sublattice. Complete characterization of TbMn$_{1-x}$Ga$_x$O$_{3}$ ($x$ = 0, 0.04, 0.1) samples, including magnetization, impedance spectroscopy, and x-ray resonant scattering and neutron diffraction on powder and single crystals has been carried out. We found that keeping the same crystal structure for all compositions, Ga for Mn substitution leads to the linear decrease of $T_{\rm N}^{\rm Mn}$ and $\tau^{\rm Mn}$, reflecting the reduction of the exchange interactions strength $J_{\rm Mn-Mn}$ and the change of the Mn-O-Mn bond angles. At the same time, a strong suppression of both the induced and the separate Tb-magnetic ordering has been observed. This behavior unambiguously prove that the exchange fields $J_{\rm Mn-Tb}$ have a strong influence on the Tb-magnetic ordering in the full temperature range below $T_{\rm N}^{\rm Mn}$ and actually stabilize the Tb-magnetic ground state.