Magnetic-field induced effects on the electric polarization inRMnO3(R=Dy,Gd)

Abstract

X-ray resonant magnetic scattering studies of rare-earth magnetic ordering were performed on perovskite manganites RMnO 3 ͑R =Dy,Gd͒ in an applied magnetic field. The data reveal that the field-induced threefold polarization enhancement for H ʈ a͑H Ϸ 20 kOe͒ observed in DyMnO 3 below 6.5 K is due to a re-emergence of the Mn-induced Dy spin order with propagation vector Dy = Mn = 0.385b ‫ء‬ , which accompanies the suppression of the independent Dy magnetic ordering, Dy =1/ 2b ‫ء‬ . For GdMnO 3 , the Mn-induced ordering of Gd spins is used to track the Mn-ordering propagation vector. The data confirm the incommensurate ordering reported previously, with Mn varying from 0.245b ‫ء‬ to 0.16b ‫ء‬ on cooling from T N Mn down to a transition temperature TЈ.New superstructure reflections which appear below TЈ suggest a propagation vector Mn =1/ 4b ‫ء‬ in zero magnetic field, which may coexist with the previously reported A-type ordering of Mn. The Gd spins order with the same propagation vector below 7 K. Within the ordered state of Gd at T = 1.8 K we find a phase boundary for an applied magnetic field H ʈ b, H = 10 kOe, which coincides with the previously reported transition between the ground-state paraelectric and the ferroelectric phases of GdMnO 3 . Our results suggest that the magnetic ordering of Gd in magnetic field may stabilize a cycloidal ordering of Mn that, in turn, produces ferroelectricity.

Magnetic and optical properties of multiferroic GdMnO3 nanoparticles

“…[1][2][3][4] The single-phase RMnO 3 ͑R ϵ a trivalent rare-earth ion, such as Tb, Dy, and Gd͒ perovskite manganites have attracted more attention in recent years because strongly competing magnetic interactions play a very important role in inducing a magnetoelectric effect. [5][6][7][8][9][10] Bulk GdMnO 3 has metamagnetic features with a transition from antiferromagnetic to weak-ferromagnetic state upon cooling and the antiferromagnetic alignments of Gd sublattice below 6 K. 11 Investigation on a single crystal GdMnO 3 shows a significant anisotropy with a strong increase in magnetization along the c-axis at about 20 K, indicating a canted state of the spontaneous magnetization. 12 Recently, attention has been focused on optical properties of single crystals and films of the manganites, proving that characteristic energy scales are related to corresponding physical phenomena.…”

Anisotropic magnetic properties and giant magnetocaloric effect in antiferromagneticRMnO3crystals (R=Dy, Tb, Ho

“…The magnetic structure determination is a prerequisite for understanding the coupling between ferroelectricity and magnetism in these materials. Several neutron and resonance x-ray studies reveal that RMnO 3 undergo sequence of complicated magnetic phase transitions with decreasing temperature [10][11][12][13][14][15][16] . It has also been shown the rareearth magnetic ordering plays a very important role in the magnetoelectric coupling 17 .…”

Ferrielectricity in DyMn2O5: A golden touchstone for multiferroicity of RMn2O5 family

“…One issue to be covered in this mini-review is the very different FE behaviors in compounds with coexisting 4f and 3d moments. [20][21][22][23] Without losing the generality, one may take the well-known multiferroic manganite DyMnO 3 as an example. First, this material has two kinds of moments: 3d-Mn 3þ and 4f-Dy 3þ , which unfortunately add complexity to the two mechanisms for ferroelectricity generation and are appreciated due to involvement of additional physics.…”