Strongly correlated one-dimensional magnetic behavior ofNiTa2O6

Abstract

The magnetic properties of NiTa2O6 were investigated by magnetic susceptibility, specific heat, electron paramagnetic resonance, neutron powder diffraction and pulse field magnetization measurements. Accompanying ab initio DFT calculations of the spin-exchange constants complemented and supported our experimental findings that NiTa2O6 must be described as a quasi-1D Heisenberg S = 1 spin chain system with a nearest-neighbor only anti-ferromagnetic spin-exchange interaction of 18.92(2) K. Inter-chain coupling is by about two orders of magnitude smaller. Electron paramagnetic resonance measurements on Mg1−xNixTa2O6 (x ≈ 1%) polycrystalline samples enabled us to estimate the single-ion zero-field splitting of the S = 1 states which amounts to less than 4% of the nearest-neighbor spin-exchange interaction. At 0 T NiTa2O6 undergoes long-range antiferromagnetic ordering at 10.3(1) K evidenced by a λ-type anomaly in the specific heat capacity. On application of a magnetic field the specific heat anomaly is smeared out. We confirmed the magnetic structure by neutron powder diffraction measurements and at 2.00(1) K refined a magnetic moment of 1.93(5) µB per Ni 2+ ion. Additionally, we followed the magnetic order parameter as a function of temperature. Lastly we found saturation of the magnetic moment at 55.5(5) T with a g-factor of 2.14(1), with an additional high field phase above 12.8(1) T. The onset of the new high field phase is not greatly effected by temperature, but rather smears out as one approaches the long-range ordering temperature.

Crystal growth and magnetic characterization of a tetragonal polymorph of NiNb2O6

“…The observations above have implications for the expected magnetic properties, as the Ni sublattice will be essentially identical to that for NiTa 2 O 6 , i.e. body-centred tetragonal, a topology which is known to give rise to a type of interlayer geometric frustration [21,22].…”

“…These results are very similar to those for the related tri-rutile phase NaTa 2 O 6 [21] and, given given that the Ni sublattices of this phase and NiNb 2 O 6 are essentially identical, this is not surprising. Data for the tantalate material have been fitted to various short range models including a S = 1 square planar [23], a S = 1 2 Ising[21] and a S = 1 Heisenberg chain [22]. The solid line in Figure 5 is a fit to the square lattice S = 1 model of Rushbrooke and Wood [24] which yields G = 2.29(7) and J/k B = -5.26(3) K.…”

Local and long-range magnetic order of thespin−32systemCoSb2O6

“…The magnetic susceptibility χ of these compounds also exhibits behavior expected for one-dimensional spin-chain systems, 8,11,14,16 with broad peaks in χ above T N .…”

“…13,14 In the case of CuSb 2 O 6 , orbital order is believed to promote antiparallel ordering of the magnetic moments along the [110] direction at z = 0 and the [110] direction at z = 1/2, which is commonly referred to as the two-sublattice antiferromagnetic structure. Spinexchange constants of NiTa 2 O 6 , obtained 14 from density functional theory (DFT), exhibit a dominant antiferromagnetic exchange along the same structural diagonals as CuSb 2 O 6 . In contrast, MnSb 2 O 6 (trigonal crystal structure) possesses a cycloidal magnetic structure, where all spin-exchange constants are of similar magnitude.…”

“…The complexity of the magnetism in CuSb 2 O 6 , CoSb 2 O 6 , and NiTa 2 O 6 is further demonstrated in the C P data above T N by the presence of local magnetic order between ∼100 K and T N = 8.7 K, 13.45 and 10.5 K, respectively. [11][12][13][14] In the case of CuSb 2 O 6 , C P exhibits an energy gap below T N , with magnitude ∆/k B = 17.5 K (k B is the Boltzmann constant), which is associated with the magnetic order, and leads to the elimination of a linear term in C P existing above T N .…”