Frustration-driven magnetic order in hexagonal InMnO3

Abstract

InMnO 3 is a peculiar member of the hexagonal manganites h-RMnO 3 (where R is a rare-earth metal element), showing crystalline, electronic, and magnetic properties at variance with the other compounds of the family. We have studied high quality samples synthesized at high pressure and temperature by powder neutron diffraction. The position of the Mn ions is found to be close to the threshold x = 1/3 where superexchange Mn-Mn interactions along the c axis compensate. Magnetic long-range order occurs below T N = 120(2) K with a magnetic unit cell doubled along c, whereas short-range two-dimensional dynamical spin correlations are observed above T N . We propose that pseudodipolar interactions are responsible for the long period magnetic structure.

Hexagonal Manganites—(RMnO3): Class (I) Multiferroics with Strong Coupling of Magnetism and Ferroelectricity

“…In contrast to other hexagonal RMnO 3 , the magnetic order below causes a doubling of the unit cell along the -axis [89]. High resolution neutron scattering experiments are consistent with the doubling of the magnetic unit cell, the onset of magnetic order at 120 K, and the absence of any further spin reorientation at lower temperatures [204]. The magnetic symmetry of the ordered Mn 3+ spins was determined to be either Γ 2 or Γ 4 (Figure 4), with the spins of two subsequent unit cells along the -axis reversed by 180 ∘ .…”

“…The lattice parameters of InMnO 3 , as determined from X-ray and neutron scattering experiments [89,200,204], deviate significantly from other hexagonal RMnO 3 . While the lattice parameter of all hexagonal RMnO 3 , including ScMnO 3 , are a linear function of the 3+ ionic radius, and of InMnO 3 deviate significantly with and found to be clearly smaller and larger, respectively, as expected from the linear dependence [89].…”

“…The 2D short range correlations of the Mn 3+ spins arise at much higher temperatures, however, 3D long range order is stabilized only at lower temperature by the weak interplane magnetic interactions. The nature of these interactions was discussed by Fabrèges et al [204] and they were attributed to long-range pseudodipolar interactions stabilizing the magnetic order along the -axis with the modulation vector ⃗ = (0, 0, 1/2).…”

Critical behavior of multiferroic hexagonal RMnO3

“…From heat capacity measurements Tachibana et al 10 have observed for the critical exponent α = − 0.16, whereas Katsufuji et al 11 have obtained α = 0.25 from dielectric susceptibility measurements. For ν Fabreges et al 12 reported the value of 0.65.…”

Incommensurate helical spin ground states on the hollandite lattice

“…[21][22][23] Nevertheless this study was only a zeroth order approximation to this type of systems as manganese compounds are known to display low magnetic anisotropy. In fact experimental data for several manganese compounds [40][41][42] have shown that these compounds are well described by the Heisenberg model. Consequently, the model of Ref.…”