Multiferroic properties of TbMn1–xFexO3

Magnetoelectric multiferroics, such as orthorhombic rare-earth manganites, where both magnetic and ferroelectric orders are coupled, have attracted great interest as they are crucial to magnetoelectric devices processing. In the case of TbMnO₃, an incommensurate sinusoidal collinear order of the Mn spins occurs at T_N = 41K, wherein the Mn spins lie in the bc-plane (Pbnm setting). Below T_lock = 28K, a magnetic transition occurs into a commensurate cycloidal spin order with Mn spins rotating in bc-plane, compatible with the stabilization of an improper ferroelectric polarization along the c-axis [1, 2]. Furthermore, it is possible to magnetically control the polarization, as a magnetic field along the b-axis rotates the cycloidal spin order to the ab-plane, and thus the electric polarization to the a-axis [1]. One way to tune the magnetoelectric coupling is by chemical substitution in TbMnO₃. The work done in ceramics shows that the substitution of Mn³⁺ by small amounts of Fe³⁺ profoundly changes the magnetic structure, altering the magnetoelectric coupling [3]. However, these studies were done in ceramics, and thus anisotropic effects cannot be ascertained, such as the flop of the cycloidal plane with an applied magnetic field.

In this work, oriented single crystals of TbMn_1-xFe_xO₃ with x = 2, 4 and 6% were used to measure polar and dielectric properties versus temperature and magnetic field along the crystallographic directions. The obtained results will be presented emphasizing the effect of temperature and magnetic field on the physical properties for the different x-values.

[1] T Kimura et al, Phys. Rev. B, 71(22), 224425 (2005)
[2] M Mochizuki et al, Phys. Rev. B, 80(13), 134416 (2009)
[3] R. Vilarinho et al, JMMM, 439, 167 (2017)