Spin-Lattice Coupling, Frustration, and Magnetic Order in MultiferroicRMnO3

Abstract

We have performed high-resolution neutron diffraction and inelastic neutron scattering experiments in the frustrated multiferroic hexagonal compounds RMnO_{3} (R = Ho,Yb,Sc,Y), which provide evidence of a strong magnetoelastic coupling in the whole family. We can correlate the atomic positions, the type of magnetic structure, and the nature of the spin waves whatever the R ion and temperature. The key parameter is the position of the Mn ions in the unit cell with respect to a critical threshold of 1/3, which determines the sign of the coupling between Mn triangular planes.

Suppression of multiferroic order in hexagonal ceramics

“…Optical studies on YMnO 3 also find clear evidence for coupling between the ferroelectric and antiferromagnetic domain walls [3], with measurements on the related compound HoMnO 3 demonstrating control of the magnetic phase using a static electric field [7]. The microscopic origin of the spin-charge coupling in YMnO 3 has also been investigated in detail using Raman scattering [8][9] and magnetoelastic measurements [6]. Raman studies on YMnO 3 thin films provide evidence for spin-phonon coupling below T N [9], while neutron measurements of spin excitations highlight the importance of magnetoelastic coupling in this system [6].…”

“…The microscopic origin of the spin-charge coupling in YMnO 3 has also been investigated in detail using Raman scattering [8][9] and magnetoelastic measurements [6]. Raman studies on YMnO 3 thin films provide evidence for spin-phonon coupling below T N [9], while neutron measurements of spin excitations highlight the importance of magnetoelastic coupling in this system [6]. Theoretical studies on YMnO 3 point to the importance of the displacement of the Y 3+ ions [10], which is facilitated by hybridization of the Y 4d orbitals with the O 2p orbitals and the buckling of the MnO 5 bipyramids [11].…”

“…The hexagonal rare earth manganites, RMnO 3 with R=Ho, Er, Tm, Yb, Lu, or Y, have been widely studied because of their magnetoelectric properties [1][2][3][4][5][6]. YMnO 3 , which develops ferroelectric order at T C~9 00 K and antiferromagnetic order below T N~7 5 K, and is therefore multiferroic below T N , has been the subject of numerous investigations exploring the nature of the magnetoelectric coupling in this class of materials.…”

Elastic anomalies associated with structural and magnetic phase transitions in single crystal hexagonal YMnO3

“…The magnetoelastic coupling effect in YMnO 3 has been the subject of much work in recent years and a series of neutron diffraction experiments has been carried out to monitor changes in lattice parameters and atomic positions at T N [7,10,29,[35][36][37]. Monitoring of changes in atomic positions and bond lengths is difficult due to the small changes involved.…”

Phonons and hybrid modes in the high and low temperature far infrared dynamics of hexagonal TmMnO3

“…[12,13] Thulium ions are in cages surrounded by seven oxygens (TmO 7 ) in a trivalent state and occupy two non-equivalent lattice sites. It is anticipated to also order magnetically at an unspecified lower temperature T N Th.…”