Coupled Magnetic Cycloids in MultiferroicTbMnO3andEu3/4Y1/4MnO3

Abstract

Based on the detailed Mn $L_{2,3}$-edge x-ray resonant scattering results, we report a new complexity in the magnetic order of multiferroic orthomangnites, which has been considered as the simple $A$-type cycloid order inducing ferroelectricity. The Dzyaloshinskii-Moriya interaction involved in the orthorhombic distortion brings on $F$-type canting from the $A$ type, and the ordering type becomes the off-phase synchronized $bc$ cycloid in ${\mathrm{TbMnO}}_3$ or the tilted antiphase $ab$ cycloid in ${\mathrm{Eu}}_{3/4}{\mathrm{Y}}_{1/4}{\mathrm{MnO}}_3$. The $F$-type canting is responsible for the magnetic field-driven multiferroicity to weak ferromagnetism transition.