Hidden magnetic order in the triangular-lattice magnet Li2MnTeO6

Abstract

The manganese tellurate Li 2 MnTeO 6 consists of trigonal spin lattices made up of Mn 4+ (d 3 , S = 3/2) ions. The magnetic properties of this compound were characterized by several experimental techniques, which include magnetic susceptibility, specific-heat, dielectric permittivity, electron-spin-resonance, nuclear magnetic resonance (NMR), and neutron powder-diffraction measurements, and by density functional theory calculations. The magnetic susceptibility χ (T ) demonstrates very unusual behavior. It is described by the Curie-Weiss law at high temperature with Curie-Weiss temperature of = −74 K and exhibits no obvious anomaly indicative of a long-range magnetic ordering at low magnetic fields. At high magnetic fields, however, the character of χ (T ) changes showing a maximum at about 9 K. That this maximum of χ (T ) reflects the onset of an antiferromagnetic order was confirmed by specific-heat measurements, which exhibit a clear λ-type anomaly at T N ≈ 8.5 K even at zero magnetic field, and by 7 Li NMR and dielectric permittivity measurements. The magnetic structure of Li 2 MnTeO 6 , determined by neutron powder-diffraction measurements at 1.6 K, is described by the 120 • noncollinear spin structure with the propagation vector k = (1/3, 1/3, 0). Consistent with this finding, the spin-exchange interactions evaluated for Li 2 MnTeO 6 by density functional calculations are dominated by the nearest-neighbor antiferromagnetic exchange within each triangular spin lattice. This spin lattice is strongly spin frustrated with f = | |/T N ≈ 8 and exhibits a two-dimensional magnetic character in a broad temperature range above T N .

Effects of Non-Stoichiometry on the Ground State of the Frustrated System Li0.8Ni0.6Sb0.4O2

“…Here, ε = |T − T crit |/T crit is reduced temperature, c is a prefactor, T crit is a critical temperature and p is a critical exponent (see Figure 10, insert to left panel). The obtained critical exponent value p = 1.67 is close to 2D Ising model (p = 1.5-1.9 [50][51][52]) and drastically different from the value obtained from the ac susceptibility. The obtained T crit = 11.7 K, which is close to T*.…”

Commensurate helicoidal order in the triangular layered magnet Na2MnTeO6

“…Earlier studied Li 2 MnTeO 6 sample, whose properties will be compared with the characteristics of its Na-based counterpart, has been prepared by the exchange reactions of Na 2 MnTeO 6 and molten lithium nitrate. The analytical and x-ray diffraction data confirmed the full replacement of sodium by lithium ions in Li 2 MnTeO 6 [10,11].…”

“…The interlayer space in these compounds is filled by the dense package of the alkali ions centered face-sharing trigonal prisms. It has been established by neutron powder diffraction that the magnetic structure of the first member in this series, Li 2 MnTeO 6 , can be represented by a 120 °noncollinear spin arrangement with the propagation vector k = (1/3, 1/3, 0) [11].…”