Magnetic structure and spin correlations in magnetoelectric honeycomb Mn4Ta2O9

Abstract

We elucidate the magnetic interactions and the role of spin (electron) correlation in determining the ground state of the honeycomb compound Mn 4 Ta 2 O 9 , by neutron powder diffraction, inelastic neutron scattering (INS), specific-heat (C P) measurements, and electronic-structure calculations. The antiferromagnetic long-range order with moments along c occurs at 102 K with strong exchange striction and small anisotropy. It is described by the three-dimensional Ising model. Diffuse magnetic scattering has been observed above T N , which is attributed to the two-dimensional spin correlations within the Mn 2+ honeycombs. This is confirmed by the calculated exchange constants. INS experiments and spin-wave simulations together with C P measurements reveal two gapped modes on the ab plane, originating from the rotation of the spins away from the easy axis c. The magnetic anisotropy is mainly determined by an electron-correlation-assisted dipole-dipole interaction. This work provides insight into the competing origins of the magnetic anisotropy, which leads to different magnetic ground states in the family of honeycomb compounds.

Highly nonlinear magnetoelectric effect in buckled-honeycomb antiferromagnetic Co4Ta2O9

“…To overcome this challenge, we grew single crystals of CTO by utilizing the conventional flux method 32 . Despite an antiferromagnetic order of CTO on buckled-honeycomb lattices, similar to the magnetic structure of Co 4 Nb 2 O 9 21 , the single crystalline CTO reveals strongly nonlinear magnetoelectric effect which is unique among A 4 B 2 O 9 (A = Co, Fe, Mn and B = Nb, Ta) compounds 20,30,[33][34][35][36] . This suggests the existence of two different polarization components originating from inequivalent Co 2+ sublattices.…”

Fe2Co2Nb2O9: a magnetoelectric honeycomb antiferromagnet

“…Honeycomb antiferromagnets (AF) M 4 M 0 2 O 9 (with M = Mn, Fe, Co and M 0 = Nb, Ta) form a large class of magnetoelectrics (ME). [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] They crystallize at room temperature (RT) in the P% 3c1 centrosymmetric space-group 1 (Fig. 1a): the M magnetic cations lie in planar honeycomb layers (A) of edge-sharing M A O 6 octahedra (in blue) alternating with buckled honeycomb layers (B) of corner-sharing M B O 6 octahedra (in green).…”

Magnetic and structural properties of Ni-substituted magnetoelectric Co4Nb2O9

“…The family of M 4 A 2 O 9 (M = Co, Mn and A = Nb, Tb) compounds was initially reported by Fischer et al [11] to show a similar magnetoelectric coupling under application of a magnetic field below their magnetic ordering temperature. In recent years, several works have been published considering the magnetic, structural, and magnetoelectric features in this series of compounds [9,[12][13][14][15][16][17][18][19][20][21]. Among these compounds, Co 4 Nb 2 O 9 has been reported to show high magnetoelectric coupling at the vicinity of its Néel transition temperature [13,14,17].…”