Magnetic-field-induced transitions in multiferroicTbMnO3probed by resonant and nonresonant x-ray diffraction

Abstract

Multiferroic ${\text{TbMnO}}_{3}$ is investigated using x-ray diffraction in high magnetic fields. Measurements on first- and second-harmonic structural reflections due to modulations induced by the Mn and Tb magnetic order are presented as function of temperature and field oriented along the $a$ and $b$ directions of the crystal. The relation to changes in ordering of the rare earth moments in applied field is discussed. Observations below ${T}_{N}^{\text{Tb}}$ without and with applied magnetic field point to a strong interaction of the rare earth order, the Mn moments, and the lattice. Also, the incommensurate to commensurate transition of the wave vector at the critical fields is discussed with respect to the Tb and Mn magnetic order, and a phase diagram on basis of these observations for magnetic fields $H\ensuremath{\parallel}a$ and $H\ensuremath{\parallel}b$ is presented. The observations point to a complicated and delicate magnetoelastic interaction as function of temperature and field.